JP4604237B2 - Lithium-iron-manganese composite oxide having a layered rock salt structure, positive electrode material for lithium ion secondary battery, lithium ion secondary battery - Google Patents

Description

  The present invention relates to a lithium-iron-manganese composite oxide, and more particularly to a lithium-iron-manganese composite oxide useful as a positive electrode material for a lithium ion secondary battery.

  At present, most of the secondary batteries installed in portable devices such as mobile phones and notebook computers in Japan are lithium ion secondary batteries having outstanding energy density. Lithium ion secondary batteries are also expected to play an important role in the future as large batteries in various fields such as electric vehicles and power load leveling systems, and their importance is increasing. .

Conventionally, 4V class lithium secondary battery positive electrode materials utilizing iron have been required from the viewpoint of reducing the cost of the battery and stabilizing the material cost. We have developed a LiFeO ₂ -Li ₂ MnO ₃ solid solution (
In this specification, the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ or described as a lithium-iron-manganese composite oxide) can be a 4V class iron-based positive electrode material. I have already found that. (Patent Documents 1 and 2). It has also been clarified that the charge / discharge characteristics can be improved by dissolving nickel ions (Patent Document 3).

  However, as Non-Patent Document 1 reveals, the charge / discharge characteristics of the material represented by the above composition formula are greatly influenced by the iron content in the material or the manufacturing conditions, so quality control during mass production. Is not easy. Therefore, it is extremely important to find out what composition, characteristics, manufacturing method, etc. of the lithium-iron-manganese composite oxide can give stable and good charge / discharge characteristics to the positive electrode material.

Furthermore, in order to put lithium-iron-manganese composite oxide into practical use as a positive electrode material for a lithium secondary battery, an existing positive electrode material, such as lithium manganese spinel (Li _{1 + δ} Mn _2-δ It is also a necessary requirement to have characteristics superior to O ₄ (0 <δ <0.33).
JP 2002-068748 A Japanese Patent Laid-Open No. 2002-121026 JP 2003-048718 M. Tabuchi, A. Nakashima, H. Shigemura, K. Ado, H. Kobayashi, H. Sakaebe, H. Kageyama, T. Nakamura, M. Kohzaki, A. Hirono and R. Kanno, Journal of The Electrochemical Society, 149, A509-A524, 2002 (In the following, this is referred to as “Tanabe literature”)

  The present invention provides lithium-iron-manganese as a positive electrode material for a lithium ion secondary battery, which can exhibit stable and good charge / discharge characteristics, and has better charge / discharge characteristics than existing positive electrode materials. The main object is to provide a composite oxide.

  As a result of researches on various factors affecting the charge / discharge characteristics in the lithium-iron-manganese composite oxide as the positive electrode material, the present inventor has succeeded in elucidating and can achieve the above-described object. A new high quality lithium-iron-manganese composite oxide has been obtained.

That is, the present invention provides the following lithium-iron-manganese composite oxide, positive electrode material, and lithium ion secondary battery.
1. Layered rock-salt lithium-iron-manganese composite oxide with the following components:
(a) represented by the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ (where 0.4 ≦ y ≦ 0.6, 0.18 ≦ x ≦ 0.33),
(b) the transition metal ion occupancy at the lithium position is 12% or less,
(c) The total amount of transition metals in the composition formula is 67% or more and the amount of tetravalent iron is 12% or more
(d) Spontaneous magnetization at 25 ° C. is 0.4 Gcm ³ / g or less.
2. A positive electrode material for a lithium ion secondary battery, comprising the layered rock salt type lithium-iron-manganese composite oxide according to item 1.
3. A lithium ion secondary battery using the material according to Item 2 as a positive electrode.

  Hereinafter, a representative example of a method for producing the lithium-iron-manganese composite oxide of the present invention that satisfies the above-mentioned requirements will be shown, and each of the steps (1) to (4) constituting the method will be described in detail. explain. Thereafter, the requirements that the lithium-iron-manganese composite oxide of the present invention should have will be described in detail based on Examples and Comparative Examples.

I. Process (1)
Step (1) is a step of obtaining a coprecipitate by adding an alkaline aqueous solution to a mixed solution of an iron salt and a manganese salt.

  Examples of the iron source material and the manganese source material include water-soluble salts (such as chlorides, nitrates, sulfates, oxalates, and acetates) and hydroxides of the respective metals. These salts may be either anhydrides or hydrates. These salts and hydroxides may be used alone or in combination of two or more for both metals. As the metal source, for any metal, an aqueous solution in which a metal or metal oxide is dissolved with an acid such as hydrochloric acid may be used.

The Fe / (Fe + Mn) molar ratio in the mixed aqueous solution can be appropriately selected according to the Fe / (Fe + Mn) molar ratio in the target composite metal oxide, but corresponds to the above composition formula Thus, it is more preferable that 0.4 ≦ y ≦ 0.6.

In the present invention, an alkaline aqueous solution is added to the mixed solution of iron salt and manganese salt to precipitate the iron-manganese coprecipitate, the reaction temperature is 20 ° C. or less, more preferably 10 ° C. or less,
More preferably, it is kept at about 5 to -15 ° C. By this temperature control, it is possible to suppress the generation of spinel ferrite (MnFe ₂ O ₄ ) as an impurity and prevent a decrease in the amount of iron ions in the target composite oxide. In particular, in order to maintain a low temperature state of 0 ° C. or lower, an amount of alcohol such as methanol, ethanol, ethylene glycol or the like necessary to exhibit the function as an antifreeze is added to the mixed solution. The amount of antifreeze added is about 1 to 50 parts by weight with respect to 100 parts by weight of water in consideration of the set reaction temperature.

As an alkali source for forming an iron-manganese coprecipitate from the above mixed solution, lithium hydroxide, potassium hydroxide, sodium hydroxide, ammonia and the like are in the form of an aqueous solution (usually about 0.1 to 20M, preferably 0.5 to 10M). Degree). The aqueous alkali source solution is added dropwise with stirring until the mixed solution becomes completely alkaline (pH 11 or more). When lithium hydroxide is used as the alkali source, lithium derived from the alkali source also constitutes a part of the lithium component in the target composite oxide.

II. Process (2)
Next, it is about 0 to 150 ° C. (more preferably about 20 to 100 ° C.) for about 2 to 7 days (more preferably 3
Over about 5 days), the coprecipitate is oxidized and aged while blowing air into the reaction solution containing the coprecipitate. The resulting oxide is then washed with distilled water to remove excess alkali components and residual salts, and a coprecipitate separated by filtration is obtained.

III. Process (3)
The purified coprecipitate is then mixed with distilled water in a predetermined container (for example, a polytetrafluoroethylene beaker), and this is mixed with lithium hydroxide (anhydride and / or hydrate), lithium chloride, lithium nitrate. Lithium salt such as 0.1 to 10M (more preferably about 1 to 8M) is added and stirred, and further an oxidizing agent such as potassium chlorate is about 0.1 to 10M (more preferably about 0.5 to 5M). The container is allowed to stand in a hydrothermal reactor (for example, an autoclave), and the mixture in the container is subjected to a hydrothermal reaction. This hydrothermal reaction treatment mixture may be prepared by preparing a liquid containing a lithium salt and an oxidizing agent in advance, and then adding the product coprecipitate to this and stirring.

  Hydrothermal reaction conditions are not particularly limited, but are usually about 100 to 400 ° C. for about 0.1 to 150 hours, more preferably about 150 to 300 ° C. for about 1 to 100 hours. .

After allowing the reaction solution after completion of the hydrothermal reaction treatment to cool, the hydrothermal reaction treatment product is washed with water, water-alcohol, acetone, etc. and filtered to remove the remaining lithium salt and the like. In this way, a purified layered rock salt type lithium-iron-manganese composite oxide (low crystalline sample) is obtained.

IV. Process (4)
Next, in order to further improve the crystallinity of the layered rock salt type lithium ferrite composite oxide, the composite oxide obtained above is pulverized and Li salt (lithium hydroxide, lithium hydroxide) in the form of powder or aqueous solution.
Lithium chloride, lithium nitrate, etc. are selected: The amount of addition varies depending on the alkali species, but in the case of lithium hydroxide and potassium hydroxide, about 0.3-1.2 times mole of lithium salt with respect to the charged molar amount is sodium hydroxide. In this case, lithium salt of about 0.3 to 1.7 times the molar amount of the charged amount is necessary), and after drying at about 50 to 200 ° C. (more preferably about 70 to 150 ° C.) in the air, Firing in an oxidizing atmosphere, an inert atmosphere or a reducing atmosphere at about 575 to 725 ° C. (more preferably about 600 to 700 ° C.) for about 1 to 200 hours (more preferably about 10 to 100 hours) Good. The lithium salt is more preferably used in the form of an aqueous solution in order to ensure the uniformity of the reaction. Further, after the firing, in order to remove excess lithium salt, the fired product is subjected to a water washing treatment or a solvent washing treatment, filtered, and then dried by heating at a temperature of 80 ° C. or higher (more preferably, a temperature of about 100 ° C.). May be.

Furthermore, by repeating a series of operations of pulverizing, baking, washing, and drying this heat-dried product, the excellent properties of lithium ferrite-based composite oxides (operation as a positive electrode material for lithium ion secondary batteries) Stable charge / discharge characteristics in the voltage region, high capacity, etc.) can be further improved.

The lithium ferrite-based composite oxide synthesized through the above steps (1) to (4) is composed of (a) composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ (provided that 0.4 ≦ y ≦ 0.6, 0.18 ≦ x ≦ 0.33), (b) the transition metal ion occupancy at the lithium position is 12% or less, (c) the total transition metal content in the composition formula is 67% or more And the amount of tetravalent iron is 12% or more, and (d) the spontaneous magnetization at 25 ° C. is 0.4 Gcm ³ / g or less.

In the above definition, “transition metal ion occupancy at the lithium position” shown in the item (b) is a layered rock salt structure as described in detail in the section of X-ray lead belt analysis in Example 1 described later. This shows the occupancy of the transition metal elements (Fe and Mn) at the lattice position (3a position) in the Li single layer when using the model as the element ratio (%). Similarly, the “total amount of transition metal in the composition formula” shown in (c) is the same as the transition metal element at the lattice position (3a position) in the Li single layer when using the layered rock-salt structure model. (Fe and Mn) occupancy (element ratio (%)) and transition metal element (Fe and Mn) occupancy (element ratio (%)) at the lattice position (3b position) in the Li-Mn-Fe mixed layer Indicates the sum.

The lithium ion secondary battery using the lithium-iron-manganese composite oxide according to the present invention can be manufactured by a known method. That is, a composite oxide obtained by the method of the present invention is used as a positive electrode material, a known metal lithium, a carbon-based material (activated carbon, graphite) or the like is used as a negative electrode material, and a known ethylene carbonate is used as an electrolyte. Using a solution in which a lithium salt such as lithium perchlorate or LiPF ₆ is dissolved in a solvent such as dimethyl carbonate, and using other known battery components, a lithium ion secondary battery is manufactured according to a conventional method. Can be assembled.

  The lithium-iron-manganese composite oxide according to the present invention is a novel material that can be stably charged and discharged in an operating voltage range (about 4 V) equivalent to that of an existing lithium cobalt oxide-based positive electrode material.

Since the lithium-iron-manganese composite oxide according to the present invention suppresses the generation of spinel ferrite (MnFe ₂ O ₄ ) as an impurity as compared with the existing lithium-iron-manganese composite oxide, High amount of effective iron ions.

  The lithium-iron-manganese composite oxide according to the present invention can be synthesized using inexpensive raw materials.

  The lithium-iron-manganese composite oxide according to the present invention can exhibit excellent performance as a positive electrode material even under a high temperature environment. For example, it has a higher capacity when compared with lithium manganese spinel, which is a typical low-cost cathode material that has been put into practical use under high-temperature charge / discharge conditions (for example, about 60 ° C.). Therefore, the lithium-iron-manganese composite oxide of the present invention has excellent performance as a positive electrode for a lithium ion secondary battery that may be used in a high temperature environment such as an in-vehicle secondary battery. It can be demonstrated.

  The lithium-iron-manganese composite oxide according to the method of the present invention is extremely useful as a positive electrode material for lithium ion secondary batteries with low cycle deterioration and low cost.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
In a glass beaker, weigh 50.50 g of iron (III) nitrate nonahydrate equivalent to 0.125 mol and 24.72 g of manganese (II) chloride tetrahydrate equivalent to 0.125 mol, add 300 ml of distilled water and stir well. And completely dissolved. The beaker containing the obtained iron-manganese mixed aqueous solution was kept at room temperature or lower (5
° C). In another glass beaker, 50 g of lithium hydroxide monohydrate was weighed, 300 ml of distilled water was added and stirred to completely dissolve. The obtained lithium hydroxide aqueous solution was gradually dropped into an iron-manganese mixed aqueous solution kept at 5 ° C. to prepare an iron-manganese coprecipitate.

The reaction solution containing the coprecipitate was taken out of the ice-cooled bath, and the coprecipitate was air oxidized for 2 days while blowing air at room temperature. To the coprecipitate after air oxidation, 1000 ml of distilled water was added and stirred well, followed by filtration to separate and remove excess lithium hydroxide, water-soluble salts and the like.

Weigh 60 g of lithium hydroxide monohydrate and 60 g of potassium chlorate (oxidizing agent) in a polytetrafluoroethylene beaker with a capacity of 1000 ml, add 500 ml of distilled water, stir well, and then add the filtrate obtained above. And dispersed by stirring. The polytetrafluoroethylene beaker was left in an autoclave and hydrothermally treated at 220 ° C. for 8 hours. After natural cooling of the treatment liquid after completion of the hydrothermal reaction, the product was taken out from the autoclave, washed with distilled water 5 times, washed, filtered, and transferred to a polytetrafluoroethylene petri dish. . A lithium hydroxide aqueous solution in which 0.25 mol (10.49 g) of lithium hydroxide monohydrate was dissolved in 100 ml of distilled water was added to the petri dish and stirred well, followed by drying at 100 ° C.

Next, after the dried product was pulverized well in an agate mortar, the obtained powder was thinly spread in an alumina firing container and fired at 650 ° C. for 20 hours in an oxygen stream using an electric furnace. After calcination, the product was cooled to room temperature over 24 hours, pulverized, then decanted with distilled water 5 times to remove excess lithium hydroxide, lithium carbonate, etc., filtered, and filtered at 100 ° C. for 12 hours. By drying for a period of time, the target substance lithium-iron-manganese composite oxide was obtained. As is apparent from FIG. 1, the obtained powder is a fine particle having an average primary particle diameter of about 100 nm.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a=2.8769(3)Å、c=14.2725(12)
Å、ピーク位置は図２において、回折図形下の縦棒で表示)で指数づけ可能であり、層状
岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成していることが確認できた。得られた格子定数値は、前出の"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 The X-ray diffraction pattern of the obtained sample is shown as “+” (upper curve) in FIG. Every peak is

Unit cell derived from a layered rock-salt structure with a space group of (lattice constant a = 2.8769 (3) Å, c = 14.2725 (12)
The peak position can be indexed with a vertical bar below the diffraction pattern in FIG. 2, and it was confirmed that a lithium-iron-manganese composite oxide having a layered rock salt type was formed. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide (a = 2.882Å, c = 14.287Å) described in the above-mentioned “Tanabe Literature”.

Evaluation of charge / discharge characteristics To 20 mg of the obtained sample, 5 mg of acetylene black and 0.5 mg of polytetrafluoroethylene powder were added, mixed in a mortar, and pressed onto a metal aluminum current collector. The obtained positive electrode mixture was vacuum-dried at 120 ° C., and then introduced into the glove box. In the glove box, the electrolyte composed of the supporting salt LiPF ₆ and ethylene carbonate / diethyl carbonate mixed solvent and the metal lithium negative electrode were used. A coin-type lithium secondary battery was produced.

  This battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge at a test temperature of 30 ° C., a charge / discharge potential range of 3-4.3 V, and a charge / discharge current density of 42 mA / g.

The charge / discharge curve in FIG. 3 shows the results of measuring the charge / discharge capacity under each charge / discharge condition (the upward curve corresponds to the charge curve, and the downward curve corresponds to the discharge curve). Table 1 shows the charge / discharge capacity. The following tables also show the results of the composite oxides obtained in Examples 2 to 10 and Comparative Examples 1 to 7 below.

  From Fig. 3 and Table 1, the charge capacity is 100mAh / g or more, the 4V flat region appears at the time of initial discharge, the initial discharge average voltage is 3.80V or more, and after 10 cycles it is 3.5V or more, about 48mAh / g It is clear that it has a discharge capacity. From this, it was confirmed that the substance according to the present invention has good characteristics as a 4V class lithium secondary battery material.

Chemical analysis The composition formula Li _{1 + x} (Fe, calculated from the following formulas 1 and 2 from the contents (% by weight) of Li, Fe and Mn obtained by the inductively coupled plasma (ICP) method _y Mn _1-y ) The x and y values in _1-x O ₂ are estimated to be 0.20 and 0.503, respectively, since the x value is greater than the reference value of 0.18 and the y value is within the range of 0.4-0.6, It was found that the target substance was obtained (see Table 2).
Formula 1: x = (Li content / 6.94-iron content / 55.85-manganese content / 54.94) / (Li content / 6.94 + iron content / 55.85 + manganese content / 54.94)
Formula 2: y = iron content / 55.85 / (iron content / 55.85 + manganese content / 54.94)
Here, the values "6.94", "55.85" and "54.94" are the atomic weights of lithium, iron and manganese, respectively.

X-ray Rietveld analysis The X-ray diffraction pattern shown in Fig. 2 (measured in 2θ range 30-125 °, 0.02 ° step by 3.5s each step) "RIETAN-2000" (F. Izumi and T. Ikeda , Mater. Sci. Forum, 321-324 (2000) 198-203), fitting with the least square method and using the following layered rock salt structure model (see Fig. 4) Transition metal (M) occupancy (%) mixed at position (3a position) and transition metal (M ') occupancy (%) present in the lattice position (3b position) in the Li-Mn-Fe mixed layer are variable. Calculated as a parameter.
Structural model: (Li _1-m M _m ) _3a [Li _1-n M ' _n ] _3b O ₂ : Here, the subscript 3a represents the ion distribution at the 3a position, and 3b represents the ion at the 3b position. Represents the distribution.

The sum of both occupancy rates was defined as the total transition metal content (%). Table 3 shows various parameters based on the X-ray diffraction results.

It is known that iron ions are mainly mixed in addition to Li ions at the 3a position using neutron diffraction, as described in the above-mentioned "Tanabe Literature". In other words, the transition metal mixture at the 3a position is caused by the disturbance of iron ions. Lithium ions that are desorbed / inserted during charge / discharge are lithium ions at the 3a position, and lithium ions desorbed / inserted move to the adjacent 3a position through the vacancy at the 6c position adjacent to the lithium ion at the 3a position. Therefore, the presence of transition metal ions at the 3a position hinders lithium ion diffusion and may cause deterioration of charge / discharge characteristics. Therefore, it is desirable to reduce the amount of transition metal ions at the 3a position as much as possible. The amount of transition metal ions at the 3a position of the substance obtained by the present invention is as low as about 4%, so that it can be seen that a sample having good charge / discharge characteristics can be produced.

Further, the total amount of transition metal obtained depends on the iron ion amount and iron ion valence in the substance of the present invention. When the amount of iron ions (Fe / (Fe + Mn) ratio, y value) relative to the total amount of transition metals is 0.5, when all iron ions are trivalent and all manganese ions are tetravalent The composition formula is
Corresponds to the case of _{Li (4-z) / 3} Fe z Mn (2-2z) / 3 O 2 of z = 0.4, is represented by _{Li 1.2 Fe 0.4 Mn 0.4 O 2} . That is, in this composition, the total amount of transition metal is 0.8 (80%). However, as will be described later, from the result of ⁵⁷ Fe Mossbauer spectroscopy, some iron ions are oxidized to tetravalent, so the composition formula is
Li _{(4-z) / 3} Fe ³⁺ _z M ⁴⁺ _{(2-2z) / 3} O ₂ (M = Mn, Fe), and z is smaller than 0.4. Since the total amount of transition metals in the target substance is related to the amount of trivalent iron and the following formula 3, formula 3: Total transition metal content (%) = 100 × (z + 2 / 3-2z / 3) = 100 × (2 + z) / 3
When z = 0.4, the total transition metal amount is 80%, but when z <0.4, the total transition metal amount can be reduced to 80% or less. However, even in the state where all iron is tetravalent (z = 0), the total amount of transition metal should be 2/3 (67%) or more from Equation 3. However, if there is an impurity phase (such as cubic rock salt type α-LiFeO ₂ or spinel ferrite LiFe ₅ O ₈ or MnFe ₂ O ₄ ) that contains iron ions in the sample, the target layered rock salt type In some cases, the amount of iron ions in the crystal phase decreases and falls below the above value (67%). In that case, it is considered that the charge / discharge capacity is remarkably lowered due to the decrease in the amount of iron ions which are the charge / discharge active species in the structure. In Example 1, since this amount is 68.4%, it is considered that good charge / discharge characteristics were obtained.

⁵⁷ Fe Mossbauer spectroscopy In order to estimate the iron ion valence in the obtained material, a ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25 ° C) (see Fig. 5; ± 2.5 mm / s). Speed range, standard material for speed calibration α-Fe). The obtained spectrum (●) has an asymmetric doublet shape, indicating that the sample is a paramagnetic substance.

Two symmetrical doublets (A and B components) with different isomer shift values were used to fit asymmetric doublets. The isomer shift value of the A component is +0.3327 (6) mm / s, and the literature (G. Prado, A. Rougier, L. Fournes and C. Delmas, Journal of The Electrochemical Society, 147, 2880-2884: A component is 3 because it is close to the value of trivalent iron (+0.33 mm / s) in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample (hereinafter referred to as “Prado literature”). It was attributed to a valence iron component. On the other hand, the isomer shift value of the B component is -0.038 (4) mm / s, and the value of tetravalent iron (-0.11 mm / s) in the above-mentioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample Since it is close, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 68.5: 31.5, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample. These results are shown in Table 4. Table 4 also includes magnetization measurement data described later.

As described in “Tanabe Literature”, the substance of this example is a material that is charged and discharged in the 4 V region by oxidizing the trivalent iron component to tetravalent during charging and returning to trivalent during discharging. Therefore, simply, the amount of trivalent iron ions in the target substance is desirably close to 100%. However, in charge / discharge tests under a high current density, the positive electrode material needs to have high electron conductivity, In this example substance, the electronic conductivity is expressed by the trivalent / tetravalent mixed atomized state of iron ions. Considering these points comprehensively, in the case of the substance according to the present invention, it is essential that the amount of tetravalent iron ions is 12% or more. In the case of the substance of Example 1, since the amount of tetravalent iron is 31.5%, it can be interpreted that a sample having good charge / discharge characteristics was obtained.

Magnetization measurement The substance obtained in Example 1 was found to be a paramagnetic substance at room temperature by Mossbauer spectroscopy. However, since it contains trivalent iron ions, the sample contains spinel ferrite. There is a possibility that a magnetic impurity (LiFe ₅ O ₈ or MnFe ₂ O ₄ ) having a representative ferrimagnetism is mixed in a trace amount (1% or less). Such magnetic impurities are extremely difficult to detect by the aforementioned powder X-ray diffraction.

Therefore, the spontaneous magnetization of the impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities. Magnetization measurement was performed at 25 ° C. in a magnetic field range of ± 10 kOe. Manganese tutton salt ((NH ₄ ) ₂ Mn (SO ₄ ) ₂ · 6H ₂ O) was used as a standard substance for calibration of magnetization.

The obtained magnetization curve is shown in FIG. When the sample is a paramagnetic substance, this curve is a straight line with a positive slope, but the obtained curve is S-shaped, indicating that it contains a trace amount of magnetic impurities. To estimate the spontaneous magnetization, the magnetization from +7 to +10 kOe is approximated by a linear regression line (dotted line in the figure) to the magnetic field, the intercept is obtained, and the magnetization from -7 to -10 kOe is linear regression line to the magnetic field. The average value with the absolute value of the value corresponding to the intercept of was taken. In the sample of this example, the spontaneous magnetization was estimated to be 0.155 (5) Gcm ³ / g. If this impurity is estimated to be LiFe ₅ O ₈ only, the spontaneous magnetization at room temperature can be found in literature (Nakaku Yasunori, Ota Keizo, Adachi Kengo, Tsuya Noboru, Ishikawa Yoshikazu, Magnetic Handbook, Asakura Shoten, 1975, p611: hereinafter referred to as “close-angle literature”), the amount of impurities is estimated to be 0.24% because it is 65 Gcm ³ / g. On the other hand, when only MnFe ₂ O ₄ is used, the impurity amount is estimated to be 0.21% from the above “close-angle literature” because it is about 75 Gcm ³ / g. In this way, trace impurities can be detected by the magnetization measurement. Since the spontaneous magnetization of the sample according to Example 1 is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization value stipulated by the present invention, it can be seen that the charge / discharge characteristics are not particularly adversely affected.

High-temperature charge / discharge test A coin-type lithium secondary battery having the same structure as that used in the charge / discharge characteristic evaluation was prepared except that the negative electrode was changed to graphite. Charge and discharge characteristics up to 10 cycles at the start of charging at a charge density of 2.5-4.3V (however, the maximum charge capacity is limited to 150mAh / g) and current density of 42mA / g. Evaluation was performed.

For comparison, a charge / discharge test was performed at 60 ° C. using a coin-type lithium secondary battery manufactured in the same manner as described above except that lithium manganese spinel (Li _1.1 Mn _1.9 O ₄ ) was used as the positive electrode material. . The Li _1.1 Mn _1.9 O ₄ used here was prepared by dry-mixing Mn ₂ O ₃ and LiOH at a molar ratio of 0.95: 1.1 and firing in the atmosphere at 900 ° C. for 20 hours.

FIG. 7 is a graph showing the charge / discharge characteristics at 60 ° C., the curve rising to the right is the charge curve and the curve falling to the right is the discharge curve. In FIG. 7, “1c” is a curve indicating the initial charge capacity, “10c” is a curve indicating the charge capacity after 10 cycles, and “1d” is a curve indicating the initial discharge capacity. "10d" is a curve showing the discharge capacity after 10 cycles.

From the obtained charge / discharge characteristics (Fig. 7), the battery using Example 1 material had a low initial discharge capacity of 100 mAh / g, but the discharge capacity after 10 cycles was 148 mAh / g. Compared to a battery using spinel (discharge capacity 74 mAh / g at the first cycle, discharge capacity 41 mAh / g at the 10th cycle), the capacity was higher. In addition, the battery using the material of Example 1 has an average discharge voltage after 10 cycles of 3.21 V, indicating that a high potential is maintained.

Furthermore, after conducting a charge / discharge test at 60 ° C., the battery using the material of Example 1 was returned to room temperature (30 ° C.), a 10-cycle charge / discharge test was performed under the same charge / discharge conditions, and long-term cycle characteristics were evaluated.

FIG. 8 is a graph showing the charge / discharge characteristics when a charge / discharge test is performed at room temperature (30 ° C.) after 10 cycles of charge / discharge tests at 60 ° C., which is “1c” as in FIG. Is the curve indicating the initial charge capacity, “10c” is the curve indicating the charge capacity after 10 cycles, “1d” is the curve indicating the initial discharge capacity, and “10d” is It is a curve which shows the discharge capacity after 10 cycles. FIG. 9 is a graph showing changes in charge / discharge capacity depending on the number of cycles in the charge / discharge test.

  8 and 9, it can be seen that the battery using the material of Example 1 can be charged / discharged without causing a capacity decrease at each cycle with an average discharge voltage of 3.2 V and a discharge capacity of 120 to 123 mAh / g.

The above tests evaluate the charge / discharge characteristics at high temperature using graphite, which is a negative electrode material that has been put into practical use, and further evaluate the long-term cycle characteristics. As a result, the material of Example 1 is
This shows that charging and discharging can be stably performed even in a practical battery configuration using graphite as a negative electrode.

Example 1 Comprehensive evaluation of materials Since the parameters obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectrum and magnetization measurement all indicate the generation of the target substance, The example material can be interpreted as having good charge / discharge characteristics.

Example 2
When the powder obtained by mixing lithium hydroxide with the hydrothermal treatment reaction product, drying, and pulverizing is fired in an electric furnace, the firing temperature is set to 600 ° C., and Example 1 (baking temperature 650 ° C.) is used. A lithium-iron-manganese composite oxide was synthesized by the same method.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a=2.8783(3) Å、c=14.2656(12)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成
していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in Example 1.

Lithium-iron-manganese composite with layered rock salt type that can be indexed by unit cell (lattice constant a = 2.8783 (3) Å, c = 14.2656 (12) Å) derived from layered rock salt structure with space group It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced by using the sample obtained in this example by the same method as in Example 1. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As is clear from Table 1, the charge capacity is 100mAh / g or more, a 4V flat region appears at the time of initial discharge, the initial discharge average voltage is 3.80V or more, and the discharge is about 52mAh / g at 3.5V or more after 10 cycles. Since it has a capacity, it was confirmed that the material of this example had good characteristics as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated using (weight%) were estimated to be 0.21 and 0.505, respectively (see Table 2). ). Since the x value was larger than the reference value of 0.18 and the y value was in the range of 0.4 to 0.6, it was found that the desired substance was obtained.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

As shown in Table 3, the amount of transition metal ions at the 3a position of the substance obtained in this example is about 5.5%, which is 12% or less, and the total amount of transition metals is greater than the reference value of 67%. It was 69.4%, and it was confirmed that the desired substance was obtained.

⁵⁷ Fe Mossbauer spectroscopy The ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25 ° C) in the same manner as in Example 1.

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of the component A is +0.3358 (6) mm / s, and the trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in “Prado literature” Since it was close to the value (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.029 (4) mm / s, and the value of tetravalent iron in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample (-0.11 mm / s) The B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 66.3: 33.7, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). In the case of the substance of the present invention, the amount of tetravalent iron ions must be 12% or more.
Since the iron content is 33.7%, it can be interpreted that the target substance was obtained.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities.

The spontaneous magnetization was estimated to be 0.078 (3) Gcm ³ / g. Since this value is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization defined by the present invention, it can be seen that the target substance is obtained.

Example 2 Comprehensive evaluation of materials Since each parameter obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectrum and magnetization measurement indicates the generation of the target substance, The example material can be interpreted as having good charge / discharge characteristics.

Example 3
When preparing the iron-manganese coprecipitate, the beaker of the iron-manganese mixed aqueous solution was changed from glass to titanium, and the same amount was replaced with an aqueous solution containing 50 g of lithium hydroxide monohydrate. A target lithium-iron-manganese composite oxide was obtained in the same manner as in Example 1 except that a sodium hydroxide aqueous solution containing 50 g of sodium hydroxide was dropped.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a= 2.8821(2)Å、c= 14.2808(10)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in Example 1.

Lithium-iron-manganese composite with layered rock salt type, which can be indexed by unit cells (lattice constant a = 2.8821 (2) Å, c = 14.2808 (10) Å) derived from layered rock salt structure with space group It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As is clear from Table 1, the charge capacity is 100mAh / g or more, a 4V flat region appears at the time of initial discharge, the initial discharge average voltage is 3.80V or more, and the discharge is about 51mAh / g at 3.5V or more after 10 cycles. Has capacity. From this, it was confirmed that the material of this example had characteristics useful as a 4V class lithium secondary battery material.

Chemical analysis In the same manner as in Example 1, the composition formula Li1 _{+ x} (Fe) calculated using the Li, Fe and Mn contents (% by weight) obtained by the inductively coupled plasma (ICP) method was used. The x and y values in _y Mn _1-y ) _1-x O ₂ were estimated to be 0.23 and 0.502, respectively (see Table 2). Since the x value was larger than the standard value of 0.18 and the y value was in the range of 0.4-0.6, it was found that the target substance was obtained.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

As shown in Table 3, the amount of 3a-position transition metal ions of the substance obtained in this example is about 7.1% and 12% or less, and the total amount of transition metals is 72.4 which is larger than the reference value of 67%. %, It was confirmed that the target substance was obtained.

⁵⁷ Fe Mossbauer spectroscopy The ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25 ° C) in the same manner as in Example 1.

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of the A component is +0.3406 (8) mm / s, and the trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in the “Prado” document. Since it was close to the value (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.005 (9) mm / s, and the value of tetravalent iron (-0.11 mm / s) in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample From the closeness, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 70.4: 29.6, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). In the case of the substance of the present invention, 4
It is essential that the amount of valent iron ions is 12% or more. In the substance of Example 3, the amount of tetravalent iron is 29.6%, which can be interpreted as that the target substance was obtained.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities. Spontaneous magnetization was estimated to be 0.0221 (13) Gcm ³ / g (see Table 4). This value is the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization defined by the present invention.
Since it is smaller, it turns out that the target substance is obtained.

Example 3 Comprehensive evaluation of materials Since each parameter obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectrum and magnetization measurement indicates the generation of the target substance, The example material can be interpreted as having good charge / discharge characteristics.

Example 4
The same as in Example 3 except that the aqueous solution of lithium hydroxide monohydrate having a different concentration is added to the purified hydrothermal reaction product contained in the petri dish made of polytetrafluoroethylene and the calcination temperature is changed. Thus, the target substance, lithium-iron-manganese composite oxide, was prepared. That is, the amount of lithium hydroxide monohydrate in 100 ml of distilled water was 0.375 mol (15.74 g) (in Example 3, it was 0.25 mol (10.49 g)), and the firing temperature was 600 ° C. (in Example 3). 650 ° C).

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a =2.8821(3)Å、c= 14.2675(11)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained lithium-iron-manganese composite oxide sample, all the peaks are the same as in Example 1.

Lithium-iron-manganese composite with layered rock salt type that can be indexed by unit cells (lattice constant a = 2.8821 (3) Å, c = 14.2675 (11) Å) derived from a layered rock salt structure with a space group of It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As is clear from Table 1, the charge capacity is 100mAh / g or more, a 4V flat region appears at the time of initial discharge, the initial discharge average voltage is 3.80V or more, and after 10 cycles, discharge is about 50mAh / g at 3.5V or more. Has capacity. From these facts, it was confirmed that the substance of this example had characteristics useful as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated using (weight%) were estimated to be 0.22 and 0.505, respectively (see Table 2). ). Since the x value was larger than the reference value of 0.18 and the y value was in the range of 0.4-0.6, it was found that the desired substance was obtained.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

As shown in Table 3, the amount of 3a-position transition metal ions of the substance obtained in this example is about 8.8% and 12% or less, and the total transition metal amount is 72.5%, which is larger than the reference value of 67%. Therefore, it was confirmed that the target substance was obtained.

⁵⁷ Fe Mossbauer spectroscopy The ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25 ° C) in the same manner as in Example 1.

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of the A component is +0.3406 (4) mm / s, and the trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in the “Prado” document. Since it was close to the value (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.039 (4) mm / s, and the value of tetravalent iron in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample (-0.11 mm / s) The B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 75.5: 24.5, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). In the case of the substance of the present invention, the amount of tetravalent iron ions must be 12% or more. In the case of the substance of Example 4, the amount of tetravalent iron is 24.5%. It can be interpreted that the substance to be obtained was obtained.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities. The spontaneous magnetization was estimated to be 0.0761 (10) Gcm ³ / g (see Table 4). Since this value is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization value defined by the present invention, it can be seen that the target substance is obtained.

Example 4 Comprehensive evaluation of materials Since each parameter obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement indicates the generation of the target substance, this example Can be interpreted as having good charge / discharge characteristics.

Example 5
When the powder obtained by mixing lithium hydroxide with the hydrothermal treatment reaction product, drying, and pulverizing was fired in an electric furnace, the firing temperature was set to 650 ° C, and Example 4 (baking temperature 600 ° C) was used. A lithium-iron-manganese composite oxide was synthesized by the same method.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a = 2.8792(2)Å、c= 14.2794(10)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生
成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in Example 1.

Lithium-iron-manganese composite with layered rock salt type that can be indexed by unit cells (lattice constant a = 2.8792 (2) Å, c = 14.2794 (10) Å) derived from a layered rock salt structure with a space group of It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As is clear from Table 1, the charge capacity is 100mAh / g or more, a 4V flat region appears at the time of initial discharge, the initial discharge average voltage is 3.80V or more, and after 10 cycles, discharge is about 50mAh / g at 3.5V or more. Since it has capacity, it was confirmed that the material of this example had characteristics useful as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated using the weight% were estimated to be 0.21 and 0.505, respectively (see Table 2). ). Since the x value was larger than the standard value of 0.18 and the y value was in the range of 0.4-0.6, it was found that the target substance was obtained.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

The amount of transition metal ions at the 3a position of the substance obtained in this example is about 5.6% and 12% or less, and the total transition metal amount is 70.5%, which is larger than the reference value of 67%. It was confirmed that the substance to be obtained was obtained.

⁵⁷ Fe Mossbauer spectroscopy In the same manner as in Example 1, a ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25C).

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of component A is +0.3355 (7) mm / s, and the trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in the “Prado” document. Since it was close to the value (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.028 (7) mm / s, and the value of tetravalent iron (-0.11 mm / s) in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample From the closeness, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 70.7: 29.3, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). In the case of the substance of the present invention, the amount of tetravalent iron ions must be 12% or more.
Since the iron content is 29.3%, it can be interpreted that the target substance was obtained.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities. The spontaneous magnetization was estimated to be 0.0953 (10) Gcm ³ / g. Since this value is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization value defined by the present invention, it can be seen that the target substance is obtained.

Example 5 Overall evaluation of materials Since each parameter obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement indicates the generation of the target substance, this example The material can be interpreted as having good charge / discharge characteristics.

Example 6
Example 3 except that in preparing the iron-manganese coprecipitate, a potassium hydroxide aqueous solution containing 50 g of the same amount of potassium hydroxide was added dropwise to the iron-manganese mixed aqueous solution instead of the aqueous solution containing 50 g of sodium hydroxide. In the same manner as described above, the target substance lithium-iron-manganese composite oxide was obtained.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a = 2.8821(3)Å、c= 14.2742(12)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生
成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in Example 1.

Lithium-iron-manganese composite with layered rock salt type that can be indexed by unit cell derived from layered rock salt type structure with a space group of (lattice constant a = 2.8821 (3) Å, c = 14.2742 (12) Å) It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced as a sample positive electrode material obtained in this example by the same method as in Example 1. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As is clear from Table 1, the charge capacity is 100mAh / g or more, a 4V flat region appears at the time of initial discharge, the initial discharge average voltage is 3.80V or more, and the discharge is about 52mAh / g at 3.5V or more after 10 cycles. Has capacity. From these facts, it was confirmed that the substance of this example had useful properties as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated using the weight% were estimated to be 0.21 and 0.504, respectively (see Table 2). ). x value is larger than the standard value of 0.18, and y value is also 0.4
Since it was in the range of -0.6, it was found that the desired substance was obtained.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

The amount of 3a-position transition metal ions of the substance obtained by this example is about 7.2% and 12% or less,
And since the total amount of transition metals was 72.5%, which was larger than the standard value of 67%, it was confirmed that the target substance was obtained.

⁵⁷ Fe Mossbauer spectroscopy In the same manner as in Example 1, a ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25C).

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of component A is +0.3383 (6) mm / s, and the value of trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in the “Prado” document Since it was close to (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.043 (6) mm / s, and the value of tetravalent iron (-0.11 mm / s) in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample is From the closeness, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 76.2: 23.8, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). In the substance of the present invention, it is essential that the amount of tetravalent iron ions is 12% or more. In the substance of Example 6, the amount of tetravalent iron is 23.8%, so that the target substance was obtained. Can be interpreted.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities. The spontaneous magnetization was estimated to be 0.0208 (11) Gcm ³ / g (see Table 4). Since this value is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization value defined by the present invention, it can be seen that the target substance is obtained.

Example 6 Overall evaluation of materials The parameters obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy, and magnetization measurement all indicate the generation of the target substance. Can be interpreted as having good charge / discharge characteristics.

Example 7
In a titanium beaker, weigh 50.50 g of iron (III) nitrate nonahydrate equivalent to 0.125 mol and 24.72 g of manganese (II) chloride tetrahydrate equivalent to 0.125 mol, add 300 ml of distilled water and 100 ml of methanol. Stir well and dissolve completely. The beaker containing the obtained iron-manganese mixed aqueous solution was cooled in a low temperature constant temperature water bath and kept at -10 ° C. In another glass beaker, 50 g of lithium hydroxide monohydrate was weighed, and 300 ml of distilled water was added and stirred to dissolve completely. The obtained lithium hydroxide aqueous solution was gradually added dropwise to the iron-manganese mixed aqueous solution kept at −10 ° C. to prepare an iron-manganese coprecipitate.

Remove the resulting coprecipitate from a low temperature constant temperature water bath and remove the coprecipitate while blowing air at room temperature.
Air oxidized for days. To the coprecipitate after air oxidation, 1000 ml of distilled water was added and stirred well, followed by filtration to separate and remove excess lithium hydroxide, alcohol, water-soluble salt, and the like.

Weigh 60 g of lithium hydroxide monohydrate and 60 g of potassium chlorate (oxidant) in a polytetrafluoroethylene beaker with a capacity of 1000 ml, add 500 ml of distilled water, stir well, and then add the filtrate obtained above. And dispersed by stirring. The polytetrafluoroethylene beaker was left in an autoclave and hydrothermally treated at 220 ° C. for 8 hours. The reaction liquid after completion of the hydrothermal treatment was naturally cooled, and then the product was taken out from the autoclave, decanted with distilled water 5 times to wash the product, filtered, and transferred to a polytetrafluoroethylene petri dish. A lithium hydroxide aqueous solution in which 0.25 mol (10.49 g) of lithium hydroxide monohydrate was dissolved in 100 ml of distilled water was added to the petri dish and stirred well, followed by drying at 100 ° C.

Next, after the dried product was pulverized well in an agate mortar, the obtained powder was thinly spread in an alumina firing container and fired at 600 ° C. for 20 hours in an oxygen stream using an electric furnace. Cool the calcined product to room temperature over 24 hours, grind the product, and then decant 5 times with distilled water to remove excess lithium hydroxide, potassium chlorate, etc. at 100 ° C for 12 hours By drying, the target substance lithium-iron-manganese composite oxide was obtained.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a=2.8821(3)Å、c=14.2792(10)
Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成
していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in the sample of Example 1.

Unit cell derived from a layered rock-salt structure with a space group of (lattice constant a = 2.8821 (3) Å, c = 14.2792 (10)
It can be indexed in (ii) and it was confirmed that a lithium-iron-manganese composite oxide having a layered rock salt type was formed. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As is clear from Table 1, the charge capacity is 100mAh / g or more, a 4V flat region appears at the time of initial discharge, the initial discharge average voltage is 3.80V or more, and the discharge is about 52mAh / g at 3.5V or more after 10 cycles. Has capacity. From these facts, it was confirmed that the substance according to this example had characteristics useful as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated using (weight%) were estimated to be 0.20 and 0.504, respectively (see Table 2). ). Since the x value was larger than the reference value of 0.18 and the y value was in the range of 0.4 to 0.6, it was found that the target substance was obtained.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

As shown in Table 3, the amount of transition metal ions at the 3a position of the substance obtained in this example is about 6.7%, which is 12% or less, and the total transition metal amount is 71.1 which is larger than the reference value of 67%. %, It was confirmed that the target substance was obtained.

⁵⁷ Fe Mossbauer spectroscopy In the same manner as in Example 1, a ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25C).

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of the A component is +0.3398 (4) mm / s, and the trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in “Prado literature” Since it was close to the value (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.043 (4) mm / s, and the value of tetravalent iron (-0.11 mm / s) in the above-mentioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample From the closeness, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 76.5: 23.5, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). The substance of the present invention requires that the amount of tetravalent iron ions is 12% or more. In the case of the substance of Example 7, the amount of tetravalent iron is 23.5%. Can be interpreted.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities. The spontaneous magnetization was estimated to be 0.0150 (11) Gcm ³ / g (see Table 4). This value is the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization defined by the present invention.
Since it is smaller, it turns out that the target substance is obtained.

Example 7 Overall evaluation of materials The parameters obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement all indicate the generation of the target substance. The substance can be interpreted as having good charge / discharge characteristics.

Example 8
Example 7 (calcination temperature 600 ° C.) except that the hydrothermal treatment reaction product was mixed with an aqueous lithium hydroxide solution, dried and pulverized, and the powder obtained by calcination was 650 ° C. in the electric furnace. Lithium-iron-manganese composite oxide was synthesized by the same method.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a= 2.8803(2)Å、c= 14.2741(10)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in Example 1.

Lithium-iron-manganese composite with layered rock salt type that can be indexed by unit cells (lattice constant a = 2.8803 (2) Å, c = 14.2741 (10) Å) derived from layered rock salt structure with space group of It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As shown in Table 1, the charge capacity is 100mAh / g or more, a 4V flat region appears during initial discharge, the initial discharge average voltage is 3.80V or more, and after 10 cycles, the discharge capacity is about 54mAh / g at 3.5V or more. It is clear that it has. From these facts, it was confirmed that the substance of this example had characteristics useful as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated using (weight%) were estimated to be 0.22 and 0.503, respectively (see Table 2). . Since the x value was larger than the standard value of 0.18 and the y value was in the range of 0.4 to 0.6, it was found that the target substance was obtained.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.
As is apparent from Table 3, the amount of the transition metal ion at the 3a position of the substance obtained in this example is about 6.
Since the total transition metal content is about 1% and 12% or less, and 71.2% larger than the standard value of 67%, it was confirmed that the target substance was obtained.

⁵⁷ Fe Mossbauer spectroscopy The ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25 ° C) in the same manner as in Example 1.

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of the component A is +0.3378 (4) mm / s, and the trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in the “Prado literature” Since it was close to the value (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.020 (4) mm / s, and the value of tetravalent iron in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample (-0.11 mm / s) The B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 73.1: 26.9, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). In the substance of the present invention, 4
It is essential that the amount of valent iron ions is 12% or more. Since the amount of tetravalent iron of the substance of Example 8 is 26.9%, it can be interpreted that the target substance was obtained.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities. The spontaneous magnetization was estimated to be 0.0227 (11) Gcm ³ / g (see Table 4). This value is the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization defined by the present invention.
Since it is smaller, it turns out that the target substance is obtained.

Example 8 Overall evaluation of materials Since each of the parameters obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement indicates the production of the target substance, The example materials can be interpreted as having good charge / discharge characteristics.

Example 9
Example 8 (calcination temperature 650 ° C.) except that the hydrothermal treatment reaction product was mixed with an aqueous lithium hydroxide solution, dried and pulverized, and the powder obtained by baking in an electric furnace was set to 700 ° C. Lithium-iron-manganese composite oxide was synthesized by the same method.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a= 2.8835(3)Å、c= 14.2985(11)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in Example 1.

Lithium-iron-manganese composite with layered rock salt type, which can be indexed by unit cells (lattice constant a = 2.8835 (3) Å, c = 14.2985 (11) Å) derived from layered rock salt structure with space group It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As is clear from Table 1, the charge capacity is 100mAh / g or more, a 4V flat region appears at the time of initial discharge, the initial discharge average voltage is 3.80V or more, and the discharge is about 51mAh / g at 3.5V or more after 10 cycles. Has capacity. From these facts, it was confirmed that the substance obtained in this example had characteristics useful as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated using (weight%) were estimated to be 0.24 and 0.502, respectively (see Table 2). ). Since the x value was larger than the standard value of 0.18 and the y value was in the range of 0.4 to 0.6, it was found that the target substance was obtained.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

The amount of transition metal ions at the 3a position of the substance obtained in this example is about 4.5% and 12% or less, and the total amount of transition metal is 70.5%, which is larger than the reference value of 67%. It was confirmed that the target substance was obtained.

⁵⁷ Fe Mossbauer spectroscopy The ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25 ° C) in the same manner as in Example 1.

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of the A component is +0.3390 (6) mm / s, and the value of trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in “Prado literature” Since it was close to (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.018 (5) mm / s, and the value of tetravalent iron (-0.11 mm / s) in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample From the closeness, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 68.7: 31.3, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). In the substance of the present invention, it is essential that the amount of tetravalent iron ions is 12% or more. In the substance of Example 9, the amount of tetravalent iron is 31.3%, so that the desired substance is obtained. Can be interpreted.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities.

Spontaneous magnetization was estimated to be 0.0432 (10) Gcm ³ / g (see Table 4). Since this value is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization value defined by the present invention, it can be seen that the target substance is obtained.

Example 9 Overall evaluation of materials Since each of the parameters obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement indicates the production of the target substance of the present invention, This example material can be interpreted as having good charge / discharge characteristics.

Example 10
In preparing an iron-manganese coprecipitate, an example was carried out except that an aqueous solution containing 50 g of potassium hydroxide was added dropwise to an aqueous solution of iron-manganese mixed instead of an aqueous solution containing 50 g of lithium hydroxide monohydrate. In the same manner as in Example 8, a lithium-iron-manganese composite oxide as a target substance was obtained.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a= 2.8805(3)Å、c= 14.2888(11
)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in Example 1.

Unit cell derived from a layered rock-salt structure with a space group of (lattice constant a = 2.8805 (3) Å, c = 14.2888 (11
It was possible to index with (ii)), and it was confirmed that a lithium-iron-manganese composite oxide having a layered rock salt type was formed. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As is clear from Table 1, the charge capacity is 100mAh / g or more, a 4V flat region appears at the time of initial discharge, the initial discharge average voltage is 3.80V or more, and after 10 cycles, discharge is about 50mAh / g at 3.5V or more. Has capacity. From these facts, it was confirmed that the substance of this example had characteristics useful as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated using (weight%) were estimated to be 0.21 and 0.503, respectively (see Table 2). ). Since the x value was larger than the reference value of 0.18 and the y value was in the range of 0.4 to 0.6, it was found that the desired substance was obtained.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

The amount of transition metal ions at the 3a position of the substance obtained in this example is about 4.7% and 12% or less, and the total transition metal amount is 69.7%, which is larger than 67%, which is the reference value. It was confirmed that the target substance was obtained.

⁵⁷ Fe Mossbauer spectroscopy In the same manner as in Example 1, a ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25C).

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of the A component is +0.3337 (5) mm / s, and the value of trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in the “Prado literature” Since it was close to (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.018 (3) mm / s, and the value of tetravalent iron (-0.11 mm / s) in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample From the closeness, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 70.4: 29.6, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). In the target substance of the present invention, it is essential that the amount of tetravalent iron ions is 12% or more. In the substance of Example 10, the amount of tetravalent iron is 29.6%, so that the target substance is obtained. Can be interpreted.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities.

The spontaneous magnetization was estimated to be 0.1543 (15) Gcm ³ / g (see Table 4). Since this value is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization value defined by the present invention, it can be seen that the target substance is obtained.

Example 10 Comprehensive evaluation of materials Since each parameter obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement indicates the generation of the target substance, this example The material can be interpreted as having good charge / discharge characteristics.

Comparative Example 1
An iron-manganese-lithium composite oxide was synthesized in the same manner as in Example 1 except that the temperature at which the iron-manganese coprecipitate was formed was room temperature (25 ° C.).

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a= 2.8920(5)Å、c= 14.2677 (19)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生
成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in Example 1.

Lithium-iron-manganese composite with layered rock salt type that can be indexed by unit cells (lattice constant a = 2.8920 (5) Å, c = 14.2677 (19) Å) derived from layered rock salt structure with space group of It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics In the same manner as in Example 1, a coin-type lithium secondary battery was manufactured using the sample obtained in this example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge in a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As can be seen from Table 1, the charge capacity is 100mAh / g or less, and a 4V flat region appears at the time of initial discharge, but the initial discharge average voltage is less than 3.80V (3.68V), and after 10 cycles, 24mAh at 3.5V or more. It had only a discharge capacity of about / g.

  It is clear that this comparative example material is unsuitable as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated using (weight%) were estimated to be 0.20 and 0.508, respectively (see Table 2). ). Since the x value was larger than the reference value of 0.18 and the y value was also within the range of 0.4 to 0.6, no difference from the target substance was observed in the composition of this Comparative Example substance.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

  As is apparent from Table 3, the amount of the transition metal ion at the 3a position of the substance obtained in this comparative example was about 13.7%, which was 12% or more, which was different from the target substance. The total amount of transition metals was 73.4%, which was larger than the standard value of 67%, and was not different from the target substance.

⁵⁷ Fe Mossbauer spectroscopy In the same manner as in Example 1, a ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25C).

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of the A component is +0.3413 (6) mm / s, and the value of trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in the “Prado literature” Since it was close to (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of B component is -0.039 (5) mm / s, and the value of tetravalent iron (-0.11 mm / s) in the above-mentioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample From the closeness, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 75.9: 24.1, there are 3 iron ions in this sample.
It can be seen that it is in a mixed valence state of valence and tetravalence. In the target substance of the present invention, it is essential that the amount of tetravalent iron ions is 12% or more. Since the amount of tetravalent iron in the material of Comparative Example 1 is 24.1%, the amount of tetravalent iron ions is No difference from the target substance was observed.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities.

Spontaneous magnetization was estimated to be 0.0521 (10) Gcm ³ / g (see Table 4). Since this value is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization value defined by the present invention, no difference from the target substance was observed in the spontaneous magnetization.

Comparative Example 1 Overall evaluation of materials Among the parameters obtained by the above chemical analysis, Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement, the disturbance of transition metal ions at the 3a position exceeds the reference value. This shows that the target substance of the present invention was not produced. Therefore, it can be interpreted that a lithium secondary battery using the material of this example as a positive electrode material does not exhibit good charge / discharge characteristics.

Comparative Example 2
A lithium-iron-manganese composite was prepared in the same manner as in Example 1 except that aqueous solutions of lithium hydroxide monohydrate having different concentrations were added to the purified hydrothermal reaction product contained in the petri dish made of polytetrafluoroethylene. An oxide was prepared. That is, the amount of lithium hydroxide monohydrate in 100 ml of distilled water was 0.375 mol (15.74 g) (in Example 1, it was 0.25 mol (10.49 g)).

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a= 2.8633(3)Å、c= 14.2519(12)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in Example 1.

Lithium-iron-manganese composite with layered rock salt type that can be indexed by unit cell (lattice constant a = 2.8633 (3) Å, c = 14.22519 (12) Å) derived from layered rock salt structure with space group It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this comparative example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

As is clear from Table 1, the charge capacity is 100mAh / g or less, and although a 4V flat region appears at the time of initial discharge, the average initial discharge voltage is less than 3.80V (3.78V), and after 10 cycles, 35mAh at 3.5V or more / g
It had only about a discharge capacity. That is, it was confirmed that the substance of Comparative Example 2 was inappropriate as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated using the weight%) are estimated to be 0.15 and 0.501, respectively. The value was smaller than 0.18 and different from the target substance. On the other hand, since the y value is in the range of 0.4 to 0.6, no difference from the target substance was observed.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

The amount of transition metal ions at the 3a position of the substance obtained by this comparative example was about 0.60%, which was 12% or less, and there was no difference from the target substance. On the other hand, the total amount of transition metals was 62.9%, which is smaller than the standard value of 67%, indicating that it was different from the target substance.

⁵⁷ Fe Mossbauer spectroscopy In the same manner as in Example 1, a ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25C).
The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of the A component is +0.3410 (17) mm / s, and the value of trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in the “Prado literature” Since it was close to (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.044 (6) mm / s, and the value of tetravalent iron (-0.11 mm / s) in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample From the closeness, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 70.3: 29.7, it is understood that iron ions are in a trivalent and tetravalent mixed valence state in this sample. In the case of the target substance of the present invention, it is essential that the amount of tetravalent iron ions is 12% or more. In the case of the substance of Comparative Example 2, the amount of tetravalent iron is 29.7%. There was no difference with the substance.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities.

The spontaneous magnetization was estimated to be 0.112 (1) Gcm ³ / g (see Table 4). This value is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization value defined by the present invention, and no difference was observed between the substance of this comparative example and the target substance with respect to spontaneous magnetization.

Comparative Example 2 Comprehensive evaluation of materials Comparative Example 2 Regarding the materials, among the parameters obtained by chemical analysis, X-ray Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement, x value of composition formula and all transition metals The amount is less than the reference value, and it can be seen that the target substance is not produced in this comparative example. As a result, it can be interpreted that good charge / discharge characteristics cannot be obtained in the lithium secondary battery using the comparative example substance as the positive electrode material.

Comparative Example 3
Example 3 (calcination temperature 650 ° C.) except that the hydrothermal treatment reaction product was mixed with an aqueous lithium hydroxide solution, dried and pulverized, and the powder obtained by calcination in an electric furnace was 550 ° C. Lithium-iron-manganese composite oxide was synthesized by the same method.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a= 2.8955(3)Å、c= 14.3041(13)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all the peaks are the same as in Example 1.

Lithium-iron-manganese composite with layered rock salt type that can be indexed by unit cell (lattice constant a = 2.8955 (3) Å, c = 14.3041 (13) Å) derived from layered rock salt structure with space group It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this comparative example as a positive electrode material. Connect this battery to the charge / discharge device and charge / discharge potential range 3-4.
Charging / discharging characteristics were evaluated at the start of charging at 3 V and a charging / discharging current density of 42 mA / g.

As is clear from Table 1, the charge capacity is 100mAh / g or more, and a 4V flat region appears at the initial discharge, but the initial discharge average voltage is less than 3.80V (3.78V), and after 10 cycles, it is 39mAh at 3.5V or more. / g
It had only about a discharge capacity.

  It was confirmed that the substance according to this comparative example was inappropriate as a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
X and y values of the calculated composition formula _{Li 1 + x (Fe y Mn} 1-y) in _1-x O ₂ from the weight%) was estimated to be respectively 0.19 and 0.502 (see Table 2). Since the x value was larger than the reference value of 0.18 and the y value was in the range of 0.4 to 0.6, no difference from the target substance of the present invention was observed.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

  The amount of transition metal ions at the 3a position of the substance obtained by the present invention was about 11.6%, which was 12% or less, which was not different from the target substance of the present invention. Further, the total amount of transition metals was also 75.5%, which is larger than the reference value of 67%, and was not different from the target substance of the present invention.

⁵⁷ Fe Mossbauer spectroscopy The ⁵⁷ Fe Mossbauer spectrum was measured at room temperature (25 ° C) in the same manner as in Example 1.

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of component A is +0.3475 (13) mm / s, and the value of trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in “Prado” Since it was close to (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is +0.004 (6) mm / s, and the value of tetravalent iron (−0.11 mm / s) in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample. Therefore, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 89.6: 10.4, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this comparative example sample. In the substance of the present invention, it is essential that the amount of tetravalent iron ions is 12% or more. In this Comparative Example 3 substance, the amount of tetravalent iron is as low as 10.4%. It turned out to be different.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities. Spontaneous magnetization was estimated to be 0.0161 (19) Gcm ³ / g (see Table 4). This value is the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization defined by the present invention.
Since it was smaller, no difference from the target substance was observed.

Overall rating <br/> more chemical analysis for Comparative Example 3 material, X-rays Rietveld analysis, among the parameters obtained by the ⁵⁷ Fe Mesubauwa spectroscopy and magnetization measurements, less than only four Ataitetsuryou the reference value, In this comparative example, it turns out that the target substance is not produced | generated. As a result, it can be interpreted that good charge / discharge characteristics cannot be obtained in the lithium secondary battery using the comparative example substance as the positive electrode material.

Comparative Example 4
Example 6 (calcination temperature 650 ° C.) except that the hydrothermal treatment reaction product was mixed with an aqueous lithium hydroxide solution, dried and pulverized, and the powder obtained by calcination in an electric furnace was 550 ° C. Lithium-iron-manganese composite oxide was synthesized by the same method.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a= 2.8901(3)Å、c= 14.2935(13)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all peaks are

Lithium-iron-manganese composite with layered rock-salt type that can be indexed by unit cells (lattice constant a = 2.8901 (3) Å, c = 14.2935 (13) Å) derived from layered rock-salt structure with space group It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample of this example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

As is clear from Table 1, the charge capacity is 100mAh / g or more, and a 4V flat region appears during initial discharge, but the initial discharge average voltage is less than 3.80V (3.78V), and after 10 cycles, it is 40mAh at 3.5V or more. / g
It had only about a discharge capacity.

  It is clear that the material of this comparative example does not have the characteristics necessary for a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
X and y values of the calculated composition formula _{Li 1 + x (Fe y Mn} 1-y) in _1-x O ₂ from the weight%) is estimated to be respectively 0.17 and 0.503, x values of the reference value It was smaller than 0.18 and different from the target substance of the present invention. On the other hand, since the y value is in the range of 0.4 to 0.6, no difference from the target substance was observed.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

The amount of 3a-position transition metal ions of the substance obtained by the present invention is about 9.4% and 12% or less,
The total amount of transition metals was 74.1%, which is larger than the standard value of 67%, and was not different from the target substance of the present invention.

⁵⁷ Fe Mossbauer spectroscopy The ⁵⁷ Fe Mossbauer spectroscopy was measured at room temperature (25 ° C) in the same manner as in Example 1.

The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of the A component is +0.3419 (4) mm / s, and the trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in the “Prado literature” Since it was close to the value (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is +0.013 (4) mm / s, and the value of tetravalent iron in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample (−0.11 mm / s) The B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 90.6: 9.4, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). In the target substance of the present invention, it is essential that the amount of tetravalent iron ions is 12% or more, whereas in this Comparative Example 4 substance, the amount of tetravalent iron is as low as 9.4%. It was found that it was different from the target substance of the invention.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities.

The spontaneous magnetization was estimated to be 0.0169 (17) Gcm ³ / g (see Table 4). Since this value is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization defined by the present invention, no difference from the target substance was observed.

Comparative example 4 Overall evaluation of materials Among the parameters obtained by the above chemical analysis, X-ray Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement, the x value and the amount of tetravalent iron in the composition formula are the standards. Since it is less than the value, it is clear that the substance of Comparative Example 4 has physical properties different from those of the target substance of the present invention. Therefore, it can be interpreted that this Comparative Example substance cannot exhibit good charge / discharge characteristics.

Comparative Example 5
A lithium-iron-manganese composite was prepared in the same manner as in Example 6 except that aqueous solutions of lithium hydroxide monohydrate having different concentrations were added to the purified hydrothermal reaction product contained in the petri dish made of polytetrafluoroethylene. An oxide was prepared. That is, the amount of lithium hydroxide monohydrate in 100 ml of distilled water was 0.375 mol (15.74 g) (in Example 6, it was 0.25 mol (10.49 g)).

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a= 2.8865(3)Å、c= 14.2604(13)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all peaks are

Lithium-iron-manganese composite with a layered rock salt type that can be indexed by unit cells (lattice constant a = 2.8865 (3) Å, c = 14.2604 (13) Å) derived from a layered rock salt structure with a space group of It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this comparative example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

As is clear from Table 1, the charge capacity is 100mAh / g or less, and although a 4V flat region appears during initial discharge, the average initial discharge voltage is less than 3.80V (3.79V), and after 10 cycles, it is 39mAh at 3.5V or more. / g
It had only about a discharge capacity.

  It is clear that the material of this comparative example does not have the characteristics necessary for a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x value and the y value in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ calculated from (weight%) are estimated to be 0.16 and 0.506, respectively, and the x value is the reference value 0.18 It was less than the target substance of the present invention. On the other hand, since the y value is in the range of 0.4 to 0.6, no difference from the target substance was observed.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

  As shown in Table 3, the amount of transition metal ions at the 3a position of the substance obtained by this Comparative Example was about 1.0%, which was 12% or less, which was not different from the target substance of the present invention. On the other hand, the total amount of transition metals was 65.5%, which is less than the reference value of 67%, which was found to be different from the target substance.

⁵⁷ Fe Mossbauer spectroscopy The ⁵⁷ Fe Mossbauer spectroscopy was measured at room temperature (25 ° C) in the same manner as in Example 1. The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of component A is +0.3325 (5) mm / s, and the value of trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in “Prado literature” Since it was close to (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.0187 (4) mm / s, and the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂
The B component can be interpreted as a tetravalent iron component because it is close to the value of tetravalent iron (-0.11 mm / s) in the sample. These A
Since the area ratio of B and B components is 72.5: 27.5, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this sample (see Table 4). In the target substance of the present invention, it is essential that the amount of tetravalent iron ions is 12% or more. In this comparative example 5 substance, the amount of tetravalent iron is 27.5%. It was found that there was no difference.

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities.

Spontaneous magnetization was estimated to be 0.660 (6) Gcm ³ / g (see Table 4). Since this value is larger than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization value defined by the present invention, it was found that the material of Comparative Example 5 is different from the target material of the present invention.

Comparative Example 5 Overall evaluation of materials Among the parameters obtained by the above chemical analysis, X-ray Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement, the material of Comparative Example 5 has an x value in the composition formula. In addition, the total amount of transition metals is less than the reference value, and the spontaneous magnetization value exceeds the reference value, which is clearly different from the target substance of the present invention. Therefore, it can be interpreted that the material of Comparative Example 5 does not have good charge / discharge characteristics.

Comparative Example 6
Example 7 (calcination temperature 600 ° C.) except that the hydrothermal treatment reaction product was mixed with an aqueous lithium hydroxide solution, dried and pulverized, and the powder obtained by calcination in an electric furnace was set at 500 ° C. Lithium-iron-manganese composite oxide was synthesized by the same method.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a=2.8936(3)Å、c= 14.3135(13)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成
していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all peaks are

Lithium-iron-manganese composite with layered rock-salt type that can be indexed by unit cells (lattice constant a = 2.8936 (3) Å, c = 14.3135 (13) Å) derived from layered rock-salt structure with space group It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this comparative example as a positive electrode material. This battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

As is clear from Table 1, the charge capacity is 100mAh / g or more, and a 4V flat region appears during initial discharge, but the initial discharge average voltage is less than 3.80V (3.70V), and after 10 cycles, it is 36mAh at 3.5V or more. / g
It had only about a discharge capacity.

  It is clear that the substance of this comparative example does not have the characteristics necessary for a 4V class lithium secondary battery material.

Chemical analysis Li, Fe and Mn contents obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1 (
The x and y values in the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ are estimated to be 0.15 and 0.505, respectively. The value was less than 0.18, which was different from the target substance of the present invention. On the other hand, the y value was in the range of 0.4 to 0.6, which was consistent with the target substance of the present invention.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

The amount of transition metal ions at the 3a position of the substance obtained by this comparative example is about 8.7%, which is 12% or less, and the total transition metal content is also 72.4%, which is a reference value of 67% or more. There was no difference from the target substance.

⁵⁷ Fe Mossbauer spectroscopy The ⁵⁷ Fe Mossbauer spectroscopy was measured at room temperature in the same manner as in Example 1. The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of component A is +0.3449 (3) mm / s, and the value of trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in Non-Patent Document 3 Since it was close to (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of B component is -0.072 (4) mm / s, and the value of tetravalent iron in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample (-0.11 mm / s) From the closeness, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 91.3: 8.7, it is understood that iron ions are in a trivalent and tetravalent mixed valence state in this sample. In the target substance of the present invention, it is essential that the amount of tetravalent iron ions be 12% or more, and in this comparative example substance, the amount of tetravalent iron was as low as 8.7%, which was found to be different from the target substance of the present invention. .

Magnetization measurement In the same manner as in Example 1, spontaneous magnetization derived from impurities was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities.

Spontaneous magnetization was estimated to be 0.0405 (12) Gcm ³ / g (see Table 4). This value is smaller than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization defined by the present invention, and no difference was found between the substance of Comparative Example 6 and the object substance of the present invention.

Comparative Example 6 Overall evaluation of materials Among the parameters obtained by the above chemical analysis, X-ray Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement, the x value and the amount of tetravalent iron in the composition formula are the standards. Since it is less than a value, in Comparative Example 6, it turns out that the target substance of the present invention is not generated. Therefore, the substance of Comparative Example 6 can be interpreted as not exhibiting good charge / discharge characteristics.

Comparative Example 7
Example 10 (calcination temperature 650 ° C.) except that the hydrothermal treatment reaction product was mixed with an aqueous lithium hydroxide solution, dried and pulverized, and the powder obtained by calcination was baked in an electric furnace. Lithium-iron-manganese composite oxide was synthesized by the same method.

の空間群を有する層状岩塩型構造由来の単位胞(格子定数a=2.8747(3)Å、c= 14.2908(12)Å)で指数づけ可能であり、層状岩塩型を有するリチウム-鉄-マンガン複合酸化物が生成
していることが確認できた。得られた格子定数値は、"田渕文献"に記載されているリチウム-鉄-マンガン複合酸化物の値(a=2.882Å、c=14.287Å)に近かった。 From the X-ray diffraction pattern of the obtained sample, all peaks are

Lithium-iron-manganese composite with layered rock-salt type that can be indexed by unit cells (lattice constant a = 2.8747 (3) Å, c = 14.2908 (12) Å) derived from a layered rock-salt structure with a space group of It was confirmed that an oxide was generated. The obtained lattice constant values were close to the values of the lithium-iron-manganese composite oxide described in "Takata literature" (a = 2.882mm, c = 14.287mm).

Evaluation of charge / discharge characteristics A coin-type lithium secondary battery was produced in the same manner as in Example 1, using the sample obtained in this comparative example as a positive electrode material. The obtained battery was connected to a charge / discharge device, and charge / discharge characteristics were evaluated at the start of charge with a charge / discharge potential range of 3-4.3 V and a charge / discharge current density of 42 mA / g.

  As can be seen from Table 1, the charge capacity is less than 100mAh / g and a 4V flat region appears during initial discharge, but the initial discharge average voltage is less than 3.80V (3.55V), and after 10 cycles, 3mAh at 3.5V or more. It had only a discharge capacity of about / g.

  It is clear that the substance of this comparative example does not have the characteristics necessary for a 4V class lithium secondary battery material.

Chemical analysis The composition formula Li _{1 + x} (Fe _y Mn) calculated using the Li, Fe, and Mn contents (% by weight) obtained by the inductively coupled plasma (ICP) method in the same manner as in Example 1. _1-y ) The x and y values in _1-x O ₂ were estimated to be 0.20 and 0.505, respectively, and both values were within the composition range of the target substance of the present invention.

X-ray Rietveld analysis The above-described crystal structure parameters were calculated in the same manner as in Example 1.

The amount of transition metal ions at the 3a position of the substance obtained by this comparative example is about 3.5% and 12% or less, and the total transition metal amount is 69.0%, which is the reference value of 67% or more. No difference was observed.

⁵⁷ Fe Mossbauer spectroscopy The ⁵⁷ Fe Mossbauer spectroscopy was measured at room temperature (25 ° C) in the same manner as in Example 1. The obtained spectrum was asymmetric doublet shape, and two symmetrical doublets (A and B components) with different isomer shift values were used to fit it. The isomer shift value of component A is +0.3379 (9) mm / s, and the value of trivalent iron in the electrochemically oxidized Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample in "Prado literature" Since it was close to (+0.33 mm / s), the A component was assigned as a trivalent iron component. On the other hand, the isomer shift value of the B component is -0.018 (7) mm / s, and the value of tetravalent iron (-0.11 mm / s) in the aforementioned Li _0.53 (Ni _0.9 Fe _0.1 ) _1.06 O ₂ sample From the closeness, the B component can be interpreted as a tetravalent iron component. Since the area ratio of these A and B components is 75.7: 24.3, it can be seen that iron ions are in a trivalent and tetravalent mixed valence state in this comparative example sample. In the target substance of the present invention, the amount of tetravalent iron ions must be at least 12%, and even in this comparative example substance, the amount of tetravalent iron is as large as 24.3%, and there is a difference from the target substance of the present invention. I couldn't.

Magnetization measurement In the same manner as in Example 1, the spontaneous magnetization derived from impurities in this comparative example substance was measured using a vibration type magnetometer, and the value was evaluated as a parameter proportional to the amount of impurities. It was.

As shown in Table 4, the spontaneous magnetization was estimated to be 0.489 (3) Gcm ³ / g. Since this value is larger than the upper limit of 0.4 Gcm ³ / g of the allowable spontaneous magnetization value stipulated by the present invention, it was found that the comparative example substance is different from the target substance of the present invention.

Comparative Example 7 Overall evaluation of materials Among the parameters obtained by the above chemical analysis, X-ray Rietveld analysis, ⁵⁷ Fe Mossbauer spectroscopy and magnetization measurement, the spontaneous magnetization value exceeds the reference value, and the present invention It turns out that the target substance is not obtained. From this, it is clear that the substance of this comparative example does not have the characteristics required as a 4V class lithium secondary battery material.

Description of various conditions for the substance of the present invention From the results of Examples and Comparative Examples shown in Tables 1 to 4, lithium-iron-manganese oxide satisfying the conditions (a) to (d) of Claim 1 It is clear that only exhibits positive charge / discharge characteristics as a positive electrode material in a lithium secondary battery.

2 is a transmission electron micrograph showing a lithium-iron-manganese composite oxide powder having an average primary particle diameter of about 100 nm obtained in Example 1. FIG. 2 is an X-ray diffraction pattern of the lithium-iron-manganese composite oxide powder obtained in Example 1. FIG. 2 is a charge / discharge curve of a coin-type lithium secondary battery produced in Example 1 at 30 ° C. FIG. This is a structural model of layered rock salt type lithium-iron-manganese composite oxide. 3 is a ⁵⁷ Fe Mossbauer spectrum at room temperature of the material obtained in Example 1. 3 is a magnetization curve at room temperature of the material obtained in Example 1. It is a graph which shows the charging / discharging characteristic in 60 degreeC about the coin-type lithium secondary battery (graphite negative electrode) using the coin-type lithium secondary battery (graphite negative electrode) produced in Example 1 and lithium manganese spinel as a positive electrode material. It is a graph which shows the charging / discharging characteristic in 30 degreeC after the charging / discharging test of 10 cycles in 60 degreeC of the coin-type lithium secondary battery using the graphite produced in Example 1 as a negative electrode. The graph which shows the relationship between the number of charge cycles in the charge / discharge test in 30 degreeC after the charge / discharge test of 10 cycles in 60 degreeC of the coin-type lithium secondary battery using the graphite produced in Example 1 as a negative electrode, and charge / discharge capacity It is.

Claims (3)

Lithium-iron-manganese composite oxide having a layered rock-salt structure with the following components:
(a) represented by the composition formula Li _{1 + x} (Fe _y Mn _1-y ) _1-x O ₂ (where 0.4 ≦ y ≦ 0.6, 0.18 ≦ x ≦ 0.33),
(b) the transition metal ion occupancy at the lithium position is 12% or less,
(c) the total transition metal amount in the composition formula is 67% or more, and the amount of tetravalent iron is 12% or more,
(d) Spontaneous magnetization at 25 ° C. is 0.4 Gcm ³ / g or less. A positive electrode material for a lithium ion secondary battery comprising the lithium-iron-manganese composite oxide having the layered rock salt structure according to claim 1. The lithium ion secondary battery which uses the material of Claim 2 as a positive electrode.

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