JP5553590B2 - Non-aqueous electrolyte battery active material and non-aqueous electrolyte battery - Google Patents

Description

  The present invention relates to an active material for a nonaqueous electrolyte battery containing iron borate and a nonaqueous electrolyte battery using the same.

  Manganese batteries, alkaline manganese batteries, and nickel metal hydride batteries that are currently commercially available and widely used are 1.5V class batteries. In recent years, with higher performance of electrical equipment using batteries as a driving power source, it is desired that these batteries have higher capacities.

Patent Document 1 discloses a nonaqueous electrolyte secondary battery (lithium-iron borate battery) in which the positive electrode active material is FeBO ₃ and the negative electrode active material is metallic lithium. Patent Document 2 discloses a lithium-iron borate battery in which the positive electrode active material is Fe ₃ BO ₆ and the negative electrode is metallic lithium. The lithium iron borate batteries described in Patent Documents 1 and 2 have an average discharge voltage of about 1.3 to 1.6V. The theoretical capacity of the active material is about 701 mAh / g for FeBO ₃ , about 879 mAh / g for Fe ₃ BO ₆ , and about 3863 mAh / g for metallic lithium, all of which are extremely high. For this reason, the lithium iron borate battery can be used as a 1.5 V class battery, and can achieve high capacity.

Japanese Patent Laid-Open No. 10-134813 JP-A-10-223225

  However, when the lithium-iron borate battery is stored at a high temperature, iron borate may be decomposed at the positive electrode and boron may be liberated. As a result, the battery storage capacity is lowered, and the high temperature storage characteristics are lowered.

  The objective of this invention is suppressing the decomposition | disassembly of the active material for nonaqueous electrolyte batteries containing iron borate, and providing the nonaqueous electrolyte battery excellent in the high temperature storage characteristic.

One aspect of the nonaqueous electrolyte battery active material of the present invention, viewed contains a eutectic of boric iron and iron oxide (III) Fe ₂ O _3, the content of Fe ₂ O ₃ for boric acid iron 0. It is 5 to 40% by mass .

  A nonaqueous electrolyte battery according to another aspect of the present invention includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a porous insulator separating the positive electrode and the negative electrode, and a nonaqueous electrolyte. A nonaqueous electrolyte battery provided, wherein either one of the positive electrode active material and the negative electrode active material is the active material for a nonaqueous electrolyte battery according to the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, about the active material for nonaqueous electrolyte batteries containing an iron borate, decomposition | disassembly of an iron borate when it preserve | saves at high temperature can be suppressed. Therefore, by using the active material for a nonaqueous electrolyte battery of the present invention, a nonaqueous electrolyte battery excellent in high temperature storage characteristics can be provided. Further, by using the non-aqueous electrolyte battery active material of the present invention as an active material of one electrode, and using lithium metal or a lithium alloy or a lithium-containing transition metal oxide as an active material of the other electrode, high temperature storage characteristics It is possible to provide a 1.5 V class non-aqueous electrolyte battery excellent in the above.

It is a longitudinal cross-sectional view which shows typically one Embodiment of a nonaqueous electrolyte battery.

<Active material for non-aqueous electrolyte battery>
The active material for a non-aqueous electrolyte battery of this embodiment includes a eutectic of iron borate and iron (III) oxide (hereinafter referred to as “iron borate-iron oxide eutectic”). The iron borate is preferably at least one selected from FeBO ₃ and Fe ₃ BO ₆ . Specifically, examples of the iron borate-iron oxide eutectic include an eutectic of FeBO ₃ and Fe ₂ O ₃ and an eutectic of Fe ₃ BO ₆ and Fe ₂ O ₃ .

An iron borate-iron oxide eutectic is a high-capacity active material. When a nonaqueous electrolyte battery is formed using an iron borate-iron oxide eutectic as a positive electrode active material and lithium or a lithium alloy as a negative electrode active material, the average discharge voltage is about 1.3 to 1.6 V ( That is, a battery of 1.5V class) can be obtained. In addition, using an iron borate-iron oxide eutectic as a negative electrode active material, a lithium-containing transition metal composite oxide capable of occluding and releasing lithium ions such as LiCoO ₂ , LiNiO ₂ , and LiMnO ₄ is used as a positive electrode active material. Even when a water electrolyte battery is formed, a 1.5 V class battery can be obtained.

  The iron borate-iron oxide eutectic suppresses the liberation of boron from iron borate when stored at a high temperature as compared with the case where iron borate is used alone as an active material. For this reason, when an iron borate-iron oxide eutectic is used as an active material, the decomposition reaction on the electrode can be suppressed. Therefore, according to the active material for a nonaqueous electrolyte battery of the present embodiment, a nonaqueous electrolyte battery excellent in high temperature storage characteristics can be obtained.

  In addition, the iron borate-iron oxide eutectic is used as an active material for a secondary battery, and even when charging / discharging is repeated, iron borate is produced from iron borate as compared with the case of using iron borate alone as an active material. The release of boron can be suppressed. Therefore, according to the active material for a nonaqueous electrolyte battery of the present embodiment, not only the primary battery but also the secondary battery can have excellent high-temperature storage characteristics.

When the iron borate-iron oxide eutectic is a eutectic of FeBO ₃ and Fe ₂ O ₃ , the content ratio of Fe ₂ O ₃ to FeBO ₃ is preferably 0.5 to 40% by mass, and 1 to 30% by mass. % Is more preferable.
When the iron borate-iron oxide eutectic is a eutectic of Fe ₃ BO ₆ and Fe ₂ O ₃ , the content ratio of Fe ₂ O ₃ to Fe ₃ BO ₆ is preferably 0.5 to 40% by mass, 1-30 mass% is further more preferable.

By setting the content ratio of iron (III) oxide to iron borate within the above range, the high-temperature storage characteristics of the battery can be further improved while maintaining the capacity of the active material.
On the other hand, when the content rate of iron (III) oxide is less than the above range, the effect of suppressing the decomposition reaction of iron borate may be reduced. On the other hand, if the content ratio of iron (III) oxide exceeds the above range, the ability of the iron borate-iron oxide eutectic to occlude and release lithium ions may decrease, and the active material capacity may greatly decrease. is there. In addition, since the change in the crystal structure of iron (III) oxide associated with insertion and extraction of lithium ions has a large effect on the electrode, when the secondary battery is configured, the cycle characteristics of the battery may also be degraded. .

  Iron (III) oxide is a substance having a very high theoretical capacity of about 1007 mAh / g, but the expression of electrochemical characteristics such as charge / discharge characteristics correlates with the particle size. Specifically, when the particle diameter of the iron oxide (III) is the micron level (μm order) of the active material, lithium ions cannot be inserted and desorbed. Therefore, sufficient electrochemical characteristics can be obtained. Furthermore, the crystal structure of iron (III) oxide changes due to insertion and extraction of lithium ions. For this reason, the battery capacity is small when an electrode reaction is performed by occlusion and release of lithium ions using micron level iron oxide (III) as an active material. In this case, since the change in the crystal structure of iron (III) oxide is repeated in the electrode, the charge / discharge cycle cannot be stably repeated.

  However, in this embodiment, iron (III) oxide is not used alone as an active material, but is used as a eutectic with iron borate. For this reason, it is possible to suppress the degree of decrease in battery capacity due to containing iron oxide (III) and the degree of change in crystal structure due to insertion and extraction of lithium ions by iron (III) oxide, The capacity of the battery can be maintained in a high range. Moreover, even if it is a case where a secondary battery is comprised, a charge / discharge characteristic can be maintained.

As the iron (III) oxide, those having a known crystal structure such as α-Fe ₂ O ₃ , β-Fe ₂ O ₃ , and γ-Fe ₂ O ₃ can be used without particular limitation. Among these, α-Fe ₂ O ₃ is preferable from the viewpoints of increasing the capacity of the active material, stability of the crystal structure during occlusion and release of lithium ions, and the like.

The iron borate-iron oxide eutectic can be produced, for example, by mixing and firing Fe ₂ O ₃ and H ₃ BO ₃ and then washing with water.
The mixing ratio of Fe ₂ O ₃ and H ₃ BO ₃ is appropriately set according to the composition of the target iron borate-iron oxide eutectic. Therefore, although the mixing ratio is not particularly limited, usually, as the mass ratio of Fe ₂ O ₃ and _{H 3 BO 3, 50: 50~85} : 15 is preferred, 55: 45-80: 20 it is more preferred.

Firing of the mixture of Fe ₂ O ₃ and H ₃ BO ₃ can be performed in the air or in an oxygen atmosphere. Firing conditions are appropriately set according to the composition of the target iron borate-iron oxide eutectic. For this reason, although it does not specifically limit, 400-1000 degreeC is preferable normally and baking temperature is more preferable 600-900 degreeC. The firing time is preferably 5 to 120 hours, more preferably 12 to 72 hours.

  The iron borate-iron oxide eutectic obtained by firing is used by pulverizing and classifying as necessary. The particle size of the iron borate-iron oxide eutectic is not particularly limited, but is preferably 0.05 to 100 μm as the volume-based average particle size. The volume-based average particle diameter can be determined by a known method such as a Coulter counter method.

  It can be confirmed that the product is a eutectic of iron borate and iron (III) oxide based on an analysis result by a powder X-ray diffraction method. The content ratio of iron (III) oxide to iron borate can be calculated based on the element ratio of the iron borate-iron oxide eutectic obtained by the high frequency inductively coupled plasma emission spectroscopy (ICP emission spectroscopy) method. it can.

In the iron borate-iron oxide eutectic of the present embodiment, iron borate (FeBO ₃ and Fe ₃ BO ₆ ) contains a part of Fe, Ni, Ti, V, Cr, Mn, Co, Cu, Al and It can be substituted with one or more elements selected from the group consisting of Mg. By substituting a part of Fe with these elements, the symmetry of the crystal structure can be lowered, and thereby the distortion of the crystal can be reduced and stabilized (Yarnteller effect). As a result, when the secondary battery is configured, the cycle characteristics of the battery are improved, and in particular, the capacity retention rate after repeating the charge / discharge cycle can be improved.

  Although the ratio of the element selected from the said group contained in iron borate is not specifically limited, Preferably it is 0.3 mol or less with respect to 1 mol of iron elements in the iron borate before substitution, More preferably 0.03 mol or more and 0.2 mol or less. When the content ratio of the element selected from the above group exceeds the above range, the distortion of the crystal in the iron borate-iron oxide eutectic becomes too large, and the charge / discharge characteristics may be deteriorated.

<Nonaqueous electrolyte battery>
The nonaqueous electrolyte battery of this embodiment includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a porous insulator that separates the positive electrode and the negative electrode, and a nonaqueous electrolyte. In this nonaqueous electrolyte battery, either the positive electrode active material or the negative electrode active material is the nonaqueous electrolyte battery active material (iron borate-iron oxide eutectic) of the present embodiment.

When using an iron borate-iron oxide eutectic as a positive electrode active material, it is preferable to use metallic lithium and a lithium alloy as the negative electrode active material. Examples of the lithium alloy include a Li—Si alloy, a Li—Sn alloy, a Li—Al alloy, and a wood alloy. In addition, silicon or tin oxide such as SiO _m , SnO _m (m satisfies 0 <m <2), SnSiO ₃ or metal nitride such as LiCoN ₂ , which is alloyed with lithium during charging. It is also preferable to use, as the negative electrode active material, a material that occludes lithium and releases lithium by dealloying during discharge.
When an iron borate-iron oxide eutectic is used as a positive electrode active material and metallic lithium and a lithium alloy are used as a negative electrode active material, the average discharge voltage is about 1.3 to 1.6 V (that is, 1.5 V class). A nonaqueous electrolyte battery can be obtained.

When using an iron borate-iron oxide eutectic as a negative electrode active material of a nonaqueous electrolyte battery, it is preferable to use a lithium-containing transition metal composite oxide as the positive electrode active material. Specific examples of the lithium-containing transition metal composite oxide include compounds represented by the following formula.
Li _a M _1-x Me _x O _{2 + δ}
(Me represents at least one element selected from the group consisting of Co, Ni and Mn, and M represents a group consisting of Na, Mg, Sc, Y, Cr, Fe, Cu, Zn, Al, Pb, Sb and B. At least one element selected from the above, a satisfies 0 <a ≦ 1.2, x satisfies 0.1 ≦ x ≦ 1, and δ indicates an oxygen defect or oxygen excess)
Li _b Mn _2-y Me _y O ₄
(Me is the same as above, b satisfies 0 <b ≦ 2, and y satisfies 0 ≦ y ≦ 0.9)
LiM'PO ₄
(M ′ represents Fe or Mn)

Specific examples of the exemplified compounds include LiCoO ₂ , LiNiO ₂ , LiCo _1-z Ni _z O ₂ (z satisfies 0 <z <1), LiMnO ₄ , LiFePO ₄ , LiMnPO _{4 and the} like.
Even when an iron borate-iron oxide eutectic is used as a negative electrode active material and the lithium-containing transition metal composite oxide exemplified above is used as a positive electrode active material, a 1.5 V class non-aqueous electrolyte battery can be obtained.

Next, the manufacturing method of the electrode containing an iron borate-iron oxide eutectic as an active material is demonstrated.
An electrode including an iron borate-iron oxide eutectic as an active material is, for example, a mixture containing an iron borate-iron oxide eutectic, a binder, and, if necessary, a conductive agent, in a predetermined electrode shape. In addition, it can be manufactured by pressure molding with a press machine or the like.

  As the binder, those conventionally used for nonaqueous electrolyte batteries can be used without any particular limitation. Specifically, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacryl Acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyethersulfone, styrene butadiene rubber And carboxymethyl cellulose. These binders can be used individually by 1 type or in mixture of 2 or more types.

  A conductive agent is a component for supplementing the electroconductivity of an active material, and what is conventionally used for the nonaqueous electrolyte battery can be used without limitation. Specifically, graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, conductive fibers such as carbon fiber and metal fiber And metal powders such as aluminum powder, conductive whiskers such as zinc oxide whisker and potassium titanate whisker, conductive metal oxides such as titanium oxide, and organic conductive materials such as phenylene derivatives. These electrically conductive agents can be used individually by 1 type or in mixture of 2 or more types. Among the conductive agents exemplified above, acetylene black is particularly suitable because of its excellent conductivity.

  In order to improve the workability at the time of manufacturing the electrode, a liquid component can be further mixed with the mixture containing the iron borate-iron oxide eutectic, the binder and the conductive agent. Examples of the liquid component include N-methyl-2-pyrrolidone (NMP).

  In the case of producing the electrode by pressure molding of the above mixture, the amount of the binder is not particularly limited, but is preferably 0.5 to 20 parts by mass with respect to 100 parts by mass of the iron borate-iron oxide eutectic, 1-10 mass parts is more preferable. Although the compounding quantity of a electrically conductive agent is not specifically limited, 1-50 mass parts is preferable with respect to 100 mass parts of iron borate-iron oxide eutectic bodies, and 3-30 mass parts is more preferable.

  After pressure-molding the mixture into a predetermined shape, heat treatment is performed as necessary. In this way, an electrode for a nonaqueous electrolyte battery formed into a predetermined shape such as a pellet shape or a disk shape can be obtained.

  An electrode containing an iron borate-iron oxide eutectic as an active material is, for example, an electrode mixture slurry containing an iron borate-iron oxide eutectic, a binder, a liquid component, and, if necessary, a conductive agent. Can be produced by coating the surface of the electrode current collector with an electrode mixture layer. The preparation method and application | coating method of an electrode mixture slurry are not specifically limited, A well-known method is employable.

Examples of the binder and the conductive agent used for preparing the electrode mixture slurry include the same ones as described above. Examples of the liquid component include NMP, acetone, methyl ethyl ketone, tetrahydrofuran, dimethylformamide and the like.
In the case where the electrode is manufactured by applying the electrode mixture slurry to the surface of the electrode current collector, the amount of the binder or conductive agent is not particularly limited, but the case where the electrode is manufactured by pressure molding of the above mixture and It may be set similarly.

As the electrode current collector, those conventionally used in non-aqueous electrolyte batteries can be used without any particular limitation.
Specific examples of the forming material for the positive electrode current collector include metals such as Ag, Ni, Pd, Au, Pt, Al, and stainless steel. These metals can be used as a film or foil. A nonwoven fabric sheet made of the above metal fibers can also be used as a positive electrode current collector. The said metal can be used individually by 1 type or in combination of 2 or more types.

Examples of the forming material for the negative electrode current collector include metals such as Cu, Ni, Pd, and stainless steel. These metals can be used as a film or foil. A nonwoven fabric sheet made of the above metal fibers can also be used as the negative electrode current collector. The said metal can be used individually by 1 type or in combination of 2 or more types.
The thickness of the electrode current collector is not particularly limited, but is preferably 1 to 30 μm.

The counter electrode of the electrode containing an iron borate-iron oxide eutectic as an active material is not particularly limited, and a known electrode can be appropriately employed.
In the case where the counter electrode is a negative electrode made of metallic lithium or a lithium alloy, the negative electrode can be manufactured by cutting metallic lithium or a lithium alloy into a predetermined shape or forming it into a predetermined shape.
When the counter electrode is a negative electrode containing SiO _m or SnO _m (m is the same as above) as a negative electrode active material, the negative electrode is formed on the surface of the electrode current collector by a method such as vapor deposition. It can manufacture by forming the film of this.
In the case where the counter electrode is a positive electrode including a lithium-containing transition metal composite oxide such as LiCoO ₂ as a positive electrode active material, the positive electrode includes, for example, a lithium-containing transition metal composite oxide, a binder, a liquid component, and a necessity. Accordingly, it can be produced by applying an electrode mixture slurry containing a conductive agent to the surface of the electrode current collector to form an electrode mixture layer.

  The porous insulator that separates the positive electrode and the negative electrode is a separator for preventing a short circuit, and those conventionally used in non-aqueous electrolyte batteries can be used without any particular limitation. Specific examples of the material for forming the porous insulator include polyethylene, polypropylene, and cellulose. The porous insulator is used as a porous sheet or a nonwoven fabric made of the above-described forming material.

Examples of the nonaqueous electrolyte include those containing a nonaqueous solvent and a solute dissolved in the nonaqueous solvent.
As the non-aqueous solvent, those conventionally used for non-aqueous electrolyte batteries can be used without any particular limitation. Specifically, carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate, diethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2- Ethers such as methyltetrahydrofuran, nitriles such as acetonitrile, lactones such as γ-butyrolactone and γ-valerolactone, oxolanes such as 1,3-dioxolane, dimethyl sulfoxide, methyl formate, 3-methyl-1,3- Examples include oxazolidine-2-one, sulfolane, ethyl acetate, and methyl propionate. These can be used individually by 1 type or in mixture of 2 or more types.

As the solute, those conventionally used in nonaqueous electrolyte batteries can be used without any particular limitation. Specifically, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiF, LiCl, LiBr, LiI, LiCN, LiNO ₃ , LiNH ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiCF ₃ SO ₃ , C ₆ H ₅ COOLi, and the like. The concentration of the solute in the nonaqueous electrolyte is not particularly limited, but is preferably 0.5 to 2.0 mol / L.

As the non-aqueous electrolyte, in addition to those exemplified above, a polymer electrolyte, an inorganic solid electrolyte, and the like can be used.
As the host polymer of the polymer electrolyte, known host polymers such as polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride and the like can be used without particular limitation. The polymer electrolyte may be a gel polymer electrolyte or a dry polymer electrolyte.
As the inorganic solid electrolyte, known inorganic solid electrolytes such as lithium halides including lithium iodide and derivatives thereof, lithium nitride, oxyacid salt materials, sulfide materials, and the like can be used without particular limitation.

A specific example of a nonaqueous electrolyte battery and a method for manufacturing the nonaqueous electrolyte battery will be described using the coin-type battery shown in FIG. 1 as an example.
In the manufacture of the coin-type battery 10, first, a positive electrode 12 formed in a disc shape is installed on the bottom surface of the battery case 11, and a porous insulator 13 is arranged on the surface of the positive electrode 12. For the positive electrode 12, an iron borate-iron oxide eutectic is mixed with a binder and a conductive agent and is pressure-molded into a disk shape. On the inner surface of the sealing plate 14 for sealing the battery case 11, a negative electrode 15 made of metallic lithium cut into a disc shape is pressure-bonded. A ring-shaped gasket 16 made of an insulating material is attached to the tip of the sealing plate 14 in advance. Next, the nonaqueous electrolyte is brought into contact with the positive electrode 12 and the porous insulator 13, and the battery case 11 is sealed with the sealing plate 14 so that the positive electrode 12 and the negative electrode 15 overlap with each other through the porous insulator 13. After sealing the battery case 11 with the sealing plate 14, the nonaqueous electrolyte battery 10 is sealed by caulking the sealing plate 14 at the opening end of the battery case 11. The battery case 11 also serves as a positive electrode terminal, and the sealing plate 14 also serves as a negative electrode terminal. This nonaqueous electrolyte battery 10 is a so-called coin-type battery.

  The form of the non-aqueous electrolyte battery is not particularly limited, and various forms such as a flat type, a cylindrical type, a square type, and a laminated type can be adopted in addition to the coin type battery shown in FIG.

  The nonaqueous electrolyte battery of this embodiment has an average discharge voltage of about 1.3 to 1.6V. For this reason, the non-aqueous electrolyte battery of this embodiment is compatible with 1.5 V class batteries, such as a manganese battery, an alkaline manganese battery, and a nickel-zinc battery, and its practical value is extremely high.

The nonaqueous electrolyte battery of this embodiment can be used as a primary battery or a secondary battery. The non-aqueous electrolyte primary battery has excellent high-temperature storage characteristics, maintains the battery capacity at a high level, and can be used as a general-purpose 1.5 V class battery. In addition, the nonaqueous electrolyte secondary battery has excellent high-temperature storage characteristics and cycle characteristics, maintains the battery capacity at a high level, and can be used as a general-purpose 1.5 V class battery.
Since the nonaqueous electrolyte battery of this embodiment is maintained at a high level, the battery can be downsized. Therefore, the nonaqueous electrolyte battery of the present embodiment is also suitable for applications such as a hearing aid power supply and a pacemaker power supply.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to a following example.

Example 1
<Preparation of FeBO ₃ -Fe ₂ O ₃ eutectic>
Obtained after weighed α-Fe ₂ O ₃ (manufactured by Sigma-Aldridge) and H ₃ BO ₃ (manufactured by Kanto Chemical Co., Inc.) at a mass ratio of 56.4: 43.6 and mixed in a mortar. The resulting mixture was calcined by heating at 670 ° C. for 24 hours in air. The obtained fired product was pulverized and pressure-molded into a pellet. Further, the obtained pellets were fired again by heating at 750 ° C. for 48 hours in the air. The fired product thus obtained was pulverized again, washed with water, heated at 120 ° C. for 12 hours and dried to obtain a powder sample. The volume-based average particle size of the powder sample was about 8 μm.

The obtained powder sample was analyzed with an X-ray diffractometer (Spectres, X'Pert PRO) to confirm that it was a eutectic of FeBO ₃ and Fe ₂ O ₃ . Furthermore, by analyzing the powder sample with an ICP emission spectroscopic analyzer (Thermo Fisher Scientific, iCAP6300), it was confirmed that the composition of the eutectic was FeBO ₃ -0.50 mass% Fe ₂ O ₃ . .

<Preparation of positive electrode>
The eutectic (FeBO ₃ -0.50 mass% Fe ₂ O ₃ ) as a positive electrode active material, acetylene black as a conductive agent, and styrene butadiene rubber as a binder at a mass ratio of 70: 25: 5 The mixture was mixed at a ratio, and the resulting mixture was pressure-molded to produce a disk-shaped pellet having a diameter of 15 mm and a thickness of 0.5 mm. Subsequently, the obtained pellet was heated at 120 ° C. for 5 hours and dried to obtain a positive electrode.

<Production of evaluation battery>
Disk-shaped metallic lithium having a diameter of 16 mm and a thickness of 0.3 mm was used as the negative electrode. This negative electrode was pressure-bonded to the inner surface of a stainless sealing plate. A gasket made of polypropylene was attached to the tip of the sealing plate. Next, a propylene separator as a porous insulator and a positive electrode were arranged in this order on the surface of the negative electrode. A non-aqueous electrolyte was previously brought into contact with the porous insulator and the positive electrode. As the non-aqueous electrolyte, a solution (LiPF ₆ concentration of 1.25 mol / L) in which LiPF ₆ was dissolved in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2 was used.

Stainless steel spacers were disposed on the surface of the positive electrode with a carbon layer interposed. This spacer is a member for ensuring electrical connection of a laminate composed of a negative electrode, a porous insulator, and a positive electrode between the battery case and the sealing plate, and the laminate is disposed within the battery case. Press toward the sealing plate. Next, a battery case was put on the sealing plate on which the electrode group and the spacer were arranged, and an outer peripheral portion of the sealing plate was caulked at the opening end of the battery case, thereby obtaining an evaluation battery.
The evaluation battery was a coin-type battery having a thickness of 3.2 mm and a diameter of 20 mm. The battery for evaluation was left to stand in an atmosphere of 45 ° C. after the production and subjected to an aging treatment for 3 days.

<Evaluation of physical properties of battery for evaluation>
The battery for evaluation subjected to the aging treatment was discharged in an atmosphere at 25 ° C. The discharge was a constant current discharge (0.36 mA) and the final discharge voltage was 0.8V. The discharge capacity at the time of this discharge (1st cycle) was measured and it was set as the initial discharge capacity _Winit [mAh]. Furthermore, based on the measurement result of the initial discharge capacity W _init, to determine the battery capacity per unit mass of the positive electrode active material [mAh / g].

Next, for the battery for evaluation whose initial discharge capacity _Winit was measured, the charge / discharge cycle was repeated in an atmosphere at 25 ° C. Discharging was performed under the same conditions as described above. Charging was performed at a constant current, and the upper limit voltage was 3.1V.
The charge / discharge cycle was repeated 30 times in total, and then the discharge capacity W ₃₀ [mAh] at the 30th cycle was measured. Then, the capacity retention rate (%) after the cycle test was obtained from the discharge capacity W _{30 at} the 30th cycle and the initial discharge capacity W _{init according} to the following formula.
Capacity maintenance rate after cycle test (%) = W ₃₀ / W _init × 100

On the other hand, the evaluation battery subjected to the aging treatment was stored in an atmosphere at 85 ° C. for 30 days. Thereafter, the battery for evaluation after high-temperature storage was discharged in an atmosphere at 25 ° C. Discharging was performed under the same conditions as described above.
The discharge capacity at the time of this discharge was measured to obtain the battery capacity W _A [mAh] after the high-temperature storage test. A battery capacity W _A after the high temperature storage test, because the initial discharge capacity W _init [mAh] and to determine the capacity retention ratio after storage test by the following formula (%).
Capacity retention rate after storage test (%) = W _A / W _init × 100

Examples 2 to 6 and Comparative Example 1
A eutectic of FeBO ₃ and Fe ₂ O ₃ was prepared in the same manner as in Example 1 except that the mixing ratio (mass ratio) of α-Fe ₂ O ₃ and H ₃ BO ₃ was changed. As a result of analyzing the obtained powder sample with an X-ray diffractometer and an ICP emission spectroscopic analyzer, it was confirmed that in Examples 2 to 6, the powder sample was a eutectic of FeBO ₃ and Fe ₂ O _3. did. On the other hand, the powder sample of Comparative Example 1 was confirmed to be a simple substance of FeBO ₃ . In Comparative Example 1, no eutectic was formed.

The mixing ratio (α-Fe ₂ O ₃ : H ₃ BO ₃ , mass ratio) of α-Fe ₂ O ₃ and H ₃ BO ₃ is shown below. The composition of the obtained eutectic is shown in Table 1.
Example 2 Mixing ratio 56.7: 43.3
Example 3 Mixing ratio 58.1: 41.9
Example 4 Mixing ratio 59.6: 40.4
Example 5: Mixing ratio 64.9: 35.1
Example 6: Mixing ratio 67.0: 33.0
Comparative Example 1 ... Mixing ratio 46.3: 53.7

  Next, an evaluation battery was prepared and evaluated for physical properties in the same manner as in Example 1 except that the eutectic having the above composition was used as the positive electrode active material. The evaluation results are shown in Table 1.

As shown in Table 1, the batteries of Examples 1 to 6 using a eutectic of FeBO ₃ and Fe ₂ O ₃ as the positive electrode active material were stored at a higher temperature than Comparative Example 1 using a single body of FeBO _3. The capacity retention rate after the test was high, and the high-temperature storage characteristics were excellent. Moreover, it turned out that the battery of Examples 1-6 has comparatively high initial stage (1st cycle) discharge capacity. Moreover, it turned out that the battery of Examples 1-6 can be used also as a secondary battery with a high capacity | capacitance maintenance factor after a cycle test, and excellent in cycling characteristics. In particular, the batteries of Examples 2 to 5 in which the content ratio of Fe ₂ O ₃ to FeBO ₃ is 1.0 to 30% by mass are the initial discharge capacity, and the capacity retention rate after the high-temperature storage test and the cycle test. However, both were very good.

Example 7
<Preparation of Fe ₃ BO ₆ -Fe ₂ O ₃ eutectic>
Obtained after weighed α-Fe ₂ O ₃ (manufactured by Sigma-Aldridge) and H ₃ BO ₃ (manufactured by Kanto Chemical Co., Inc.) at a mass ratio of 66.3: 33.7 and mixed in a mortar. The resulting mixture was calcined by heating at 670 ° C. for 24 hours in air. The obtained fired product was pulverized and pressure-molded into a pellet. Furthermore, the obtained pellet was fired again by heating at 900 ° C. for 48 hours in the air. The fired product thus obtained was pulverized again, washed with water, heated at 120 ° C. for 12 hours and dried to obtain a powder sample. The volume-based average particle size of the powder sample was about 8 μm.

The obtained powder sample was analyzed with an X-ray diffractometer (X′Pert PRO), and confirmed to be a eutectic of Fe ₃ BO ₆ and Fe ₂ O ₃ . Furthermore, by analyzing the powder sample with an ICP emission spectroscopic analyzer (iCAP6300), it was confirmed that the composition of the eutectic was Fe ₃ BO ₆ -0.50 mass% Fe ₂ O ₃ .

<Preparation of positive electrode and battery for evaluation and evaluation of physical properties of battery>
A positive electrode was produced in the same manner as in Example 1 except that the above eutectic (Fe ₃ BO ₆ -0.50 mass% Fe ₂ O ₃ ) was used as the positive electrode active material. A battery for evaluation was produced and the physical properties were evaluated in the same manner as in Example 1 except that the positive electrode thus obtained was used. The evaluation results are shown in Table 2.

Examples 8-12
A eutectic of Fe ₃ BO ₆ and Fe ₂ O ₃ was prepared in the same manner as in Example 7 except that the mixing ratio (mass ratio) of α-Fe ₂ O ₃ and H ₃ BO ₃ was changed. The obtained powder sample was analyzed by an X-ray diffractometer and an ICP emission spectroscopic analyzer. As a result, in Examples 8 to 12, the powder sample was a eutectic of Fe ₃ BO ₆ and Fe ₂ O _3. It was confirmed. On the other hand, the powder sample of Comparative Example 2 was confirmed to be a simple substance of Fe ₃ BO ₆ . In Comparative Example 2, no eutectic was formed.

The mixing ratio (α-Fe ₂ O ₃ : H ₃ BO ₃ , mass ratio) of α-Fe ₂ O ₃ and H ₃ BO ₃ is shown below. The composition of the obtained eutectic is shown in Table 2.
Example 8: Mixing ratio 66.7: 33.3
Example 9: Mixing ratio 69.4: 30.6
Example 10: Mixing ratio 72.2: 27.8
Example 11: Mixing ratio 79.7: 20.3
Example 12: Mixing ratio 82.1: 17.9
Comparative Example 2 ... Mixing ratio 56.4: 43.7

  Next, an evaluation battery was prepared and evaluated for physical properties in the same manner as in Example 1 except that the eutectic having the above composition was used as the positive electrode active material. The evaluation results are shown in Table 2.

As shown in Table 2, the batteries of Examples 7 to 12 using the eutectic of Fe ₃ BO ₆ and Fe ₂ O ₃ as the positive electrode active material were compared with Comparative Example 2 using the simple substance of Fe ₃ BO _6. Thus, the capacity retention rate after the high temperature storage test was high, and the high temperature storage characteristics were excellent. Moreover, it turned out that the battery of Examples 7-12 has comparatively high initial stage (1st cycle) discharge capacity. Moreover, it was found that the batteries of Examples 7 to 12 had a high capacity retention rate after the cycle test and could be used as secondary batteries having excellent cycle characteristics. In particular, the batteries of Examples 8 to 11 in which the content ratio of Fe ₂ O ₃ to Fe ₃ BO ₆ is 1.0 to 30% by mass are the initial discharge capacity, the capacity after the high-temperature storage test and the cycle test. The maintenance rate was extremely good.

  The active material for a nonaqueous electrolyte battery of the present invention is excellent in high-temperature storage characteristics and is extremely useful as a material for forming a nonaqueous electrolyte battery. The nonaqueous electrolyte battery of the present invention is useful as a 1.5 V class battery having a relatively large capacity and excellent versatility. Moreover, since the cycle characteristics are excellent, it is also useful as a secondary battery.

  10 coin type battery, 11 battery case, 12 positive electrode, 13 porous insulator, 14 sealing plate, 15 negative electrode, 16 gasket

Claims (7)

Comprises eutectic of boric iron and Fe ₂ O _3, the content of Fe ₂ O ₃ for boric acid iron is 0.5 to 40 mass%, the active material for a non-aqueous electrolyte batteries. The active material for a non-aqueous electrolyte battery according to claim 1, wherein the iron borate is at least one selected from FeBO ₃ and Fe ₃ BO ₆ . The active material for a non-aqueous electrolyte battery according to claim 1, wherein the eutectic is a eutectic of FeBO ₃ and Fe ₂ O ₃ . The active material for a non-aqueous electrolyte battery according to claim 1, wherein the eutectic is a eutectic of Fe ₃ BO ₆ and Fe ₂ O ₃ . The active material for a nonaqueous electrolyte battery according to claim 1, wherein the content ratio of Fe ₂ O _{3 to} iron borate is 1 to 30% by mass. A non-aqueous electrolyte battery comprising a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a porous insulator separating the positive electrode and the negative electrode, and a non-aqueous electrolyte,
The non-aqueous electrolyte battery in which any one of the said positive electrode active material and the said negative electrode active material is an active material for non-aqueous electrolyte batteries of any one of Claims 1-5. The positive active material is an active material for the nonaqueous electrolyte battery,
The negative active material is metallic lithium or a lithium alloy, a non-aqueous electrolyte battery according to claim 6.

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