JP7446595B2 - Method for producing lithium metal composite oxide powder - Google Patents

Description

The present invention relates to a lithium metal composite oxide powder containing lithium element, niobium element, manganese element, and oxygen element, a method for producing the same, a lithium ion secondary battery using the lithium metal composite oxide powder, and a method for producing the same.

Various lithium metal composite oxides are known as positive electrode active materials used in lithium ion secondary batteries.
For example, Patent Document 1 discloses a method for producing Li _x Me _y O ₂ , which is a type of lithium metal composite oxide. Specifically, Patent Document 1 describes that a solid material obtained by weighing and mixing a raw material containing Li, a raw material containing O, and a raw material containing Me is mechanochemically heated for 10 hours or more using a mixing device such as a ball mill. It is disclosed that Li _x Me _y O ₂ can be produced by reacting with. The synthesis method in which the reaction proceeds while maintaining the solid state using solid raw materials is hereinafter referred to as a solid-phase method, as necessary.

When using the solid phase method as introduced in Patent Document 1 mentioned above, there is a problem that it takes a long time to produce a lithium metal composite oxide. Therefore, it is difficult to say that the method for producing a lithium metal composite oxide using the solid phase method is excellent in efficiency, and a method for producing a lithium metal composite oxide with excellent production efficiency is desired.

Japanese Patent Application Publication No. 2017-152370

By the way, in consideration of the speed of battery reaction, it is said that it is preferable to use a positive electrode active material for a lithium ion secondary battery that has a relatively small average particle diameter. It is believed that the particles contained in the lithium metal composite oxide powder produced by the above-mentioned solid phase method have a relatively large average particle diameter of μm or more. Therefore, in order to further improve the reactivity of a lithium ion secondary battery using a lithium metal composite oxide powder manufactured by the solid phase method as introduced in Patent Document 1, it is necessary to It is necessary to further pulverize the powder. However, since the pulverization step requires a long time, there is a possibility that the production efficiency of the lithium metal composite oxide powder will be further deteriorated.
The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the production efficiency of lithium metal composite oxide powder.

The method for producing lithium metal composite oxide powder of the present invention includes:
A lithium metal composite oxide powder having an average particle size on the nano level, which includes a step of introducing a lithium metal composite oxide source containing lithium element, niobium element, manganese element, and oxygen element into plasma through an introduction flow. This is a manufacturing method.

According to the method for producing lithium metal composite oxide powder of the present invention, powdered lithium metal composite oxide powder can be produced in one step, which improves the production efficiency of lithium metal composite oxide powder and improves the lithium metal composite oxide powder production efficiency. The manufacturing efficiency of the lithium ion secondary battery used can be improved.

FIG. 1 is a schematic diagram of a plasma generator. 1 is a graph showing rate characteristics of lithium ion secondary batteries of Example 1 and Comparative Example 1. 1 is a SEM image of the lithium metal composite oxide powder of Example 1. 1 is a SEM image of lithium metal composite oxide powder of Comparative Example 1. 3 is a graph showing the cycle characteristics of the lithium ion secondary battery of Example 1. 3 is a graph showing the cycle characteristics of the lithium ion secondary battery of Example 2. 3 is a graph showing cycle characteristics of a lithium ion secondary battery of Comparative Example 1. 1 is an X-ray diffraction chart of the lithium metal composite oxide powder of Example 1 and the lithium metal composite oxide powder of Example 2.

The best mode for carrying out the present invention will be described below. Note that, unless otherwise specified, the numerical range "x to y" described herein includes the lower limit x and the upper limit y. A numerical range can be constructed by arbitrarily combining these upper and lower limit values, as well as the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from within these numerical ranges can be used as the upper and lower limits of the new numerical range.

(Lithium metal composite oxide powder)
The method for producing lithium metal composite oxide powder of the present invention is a method for producing lithium metal composite oxide powder having an average particle size on the nano level. As used herein, "the average particle size is on the nano level" refers to the average particle size being in the range of 1 nm or more and less than 1000 nm. That is, the average particle diameter of the lithium metal composite oxide powder obtained by the production method of the present invention is within the above range. Note that whether or not the average particle size of the lithium metal composite oxide powder obtained by the production method of the present invention is on the nano level can be confirmed by an electron microscope image as described later.
Hereinafter, the lithium metal composite oxide powder obtained by the method for producing lithium metal composite oxide powder of the present invention may be referred to as the lithium metal composite oxide powder of the present invention, if necessary. Further, the method for producing lithium metal composite oxide powder of the present invention may be simply referred to as the production method of the present invention.
The lithium metal composite oxide powder of the present invention is composed of a large number of particles, and each particle may be composed of crystallites or may be a composite of several crystallites.

The present invention will be explained below along with the manufacturing method of the present invention.

The method for producing a lithium metal composite oxide powder of the present invention is a method for producing a lithium metal composite oxide powder having an average particle size on the nano level, and includes a lithium metal composite oxide powder containing lithium element, niobium element, manganese element and oxygen element. The method includes the step of introducing a complex oxide source into the plasma in an inlet stream.

The lithium metal composite oxide powder of the present invention produced by the production method of the present invention is a powdered lithium metal composite oxide containing lithium element, niobium element, manganese element, and oxygen element derived from a lithium metal composite oxide source. It can be said that it is a thing.
The lithium metal composite oxide contains a lithium element, a niobium element, a manganese element, and an oxygen element, and may also contain other metal elements. Examples of the other metal elements include at least one selected from the group consisting of Group 2 elements, transition metals, rare earths, Group 13 elements, and Group 14 elements. Preferably, it is one selected from transition metals, Group 2 elements, and rare earth elements, and particularly preferably one selected from Ni, Cr, Ti, Cu, Zn, Pt, and Pd.

Specific lithium metal composite oxides include Li _1.2 Mn _0.6 Nb _0.2 O ₂ , Li _1.25 Mn _0.5 Nb _0.25 O ₂ , Li _1.17 Mn _0.67 Nb _0.17 O ₂ , Li _1.125 Mn _0.75 Nb _0.125 O ₂ , Li _1.21 Mn _0.67 Nb _0.11 O ₂ , Li _1.167 Mn _0.667 Nb _0.167 O ₂ Li _a Mn _b Nb _c O ₂ (0.8<a<1.3, 0<b<1, 0<c<1, 1.8≦a+b+c≦2.2).
The lithium metal composite oxide in the present invention is Li _a Mn _b Nb _c D _d O ₂ (0.8<a<1.3, 0<b<1, 0<c<1, 0≦d<1, 1 .8≦a+b+c+d≦2.2), the basic structure may be the above-mentioned Li _a Mn _b Nb _c O ₂ and further include other doping elements. Furthermore, a part of Mn or Nb in the lithium metal composite oxide may be replaced with another transition metal.
The crystal structure of the lithium metal composite oxide in the present invention can exhibit a crystal structure that can be assigned to the space group Fm-3m. In addition, in the notation of the type of space group such as "Fm-3m", "-3" represents 3 with an overline.
The lithium metal composite oxide in the present invention may be one that exhibits a crystal structure that can be assigned to the space group Fm-3m, or one that exhibits a crystal structure that can be assigned to the space group Fm-3m, and one that exhibits a crystal structure that can be assigned to the space group Fm-3m. A mixture may also be used.

The lithium metal composite oxide exhibiting a crystal structure that can be assigned to space group Fm-3m may exhibit a cubic rock salt structure.
The relationship between the lithium element, the manganese element, and the niobium element in the lithium metal composite oxide is such that a>b>c in the above Li _a Mn _b Nb _c O ₂ or Li _a Mn _b Nb _c D _d O ₂ . is preferred. Each range of a, b, and c will be described. More preferable ranges for a include the following ranges: 0.9≦a≦1.25, 1.0≦a≦1.2, and 1.0<a≦1.2. More preferable ranges for b include the following ranges: 0.3≦b≦0.8, 0.5≦b<0.8, and 0.55≦b≦0.75. More preferable ranges for c include the following ranges: 0.05≦c≦0.5, 0.07≦c≦0.3, and 0.1≦c≦0.25.

The lithium metal composite oxide powder of the present invention can be used as a positive electrode active material for lithium ion secondary batteries. In that case, the lithium metal composite oxide powder of the present invention may be used alone as the positive electrode active material, or may be used in combination with other positive electrode active materials. Moreover, two or more types of lithium metal composite oxide powders of the present invention may be used in combination as positive electrode active materials.

The method for producing lithium metal composite oxide powder of the present invention includes the step of introducing a lithium metal composite oxide source into plasma in an introduction flow.
The lithium metal composite oxide source only needs to contain a lithium element, a manganese element, a niobium element, and an oxygen element that can become oxygen gas, and can be a raw material or a raw material that can be a raw material for the powdered lithium metal composite oxide of the present invention. Any raw material mixture may be used. In other words, the lithium metal composite oxide source may be the same as the above-mentioned lithium metal composite oxide, it may be different, it may be a single substance, or it may be a mixture of multiple single substances. It may be. Furthermore, the lithium metal composite oxide source may be in a solid, liquid, or gaseous state, or may be a mixture thereof.

The method for producing lithium metal composite oxide powder of the present invention includes the step of introducing a lithium metal composite oxide source into plasma. For this reason, the lithium metal composite oxide source is preferably in a powder, liquid, and/or gas form that can be easily introduced into the plasma.

Hereinafter, as needed, a lithium metal composite oxide source containing a lithium element will be referred to as a Li source, a manganese element as a Mn source, a niobium element as a Nb source, and an oxygen A source containing oxygen that can become a gas is called an O source. Considering the ease of handling the lithium metal composite oxide source, it is preferable that at least the Li source, Mn source, and Nb source be in powder form. The Li source, Mn source, and Nb source may each be used alone, or may be used in the form of a compound containing two or more of them. The O source may be used in the form of a compound together with at least one of the Li source, Mn source, and Nb source, or may be used alone, that is, in the form of oxygen gas.

Specifically, the Li source may be lithium alone, that is, metallic lithium, or may be a compound containing at least one of manganese element, niobium element, and oxygen element in addition to lithium element. Furthermore, it may be a compound that requires a lithium source and contains elements other than those mentioned above.

Examples of such Li sources include lithium alone or lithium compounds represented by Li ₂ CO ₃ , LiOH, LiMn ₂ O ₄ , LiNbO ₃ , Li ₂ O, Li ₂ O ₂ , and LiO ₂ . can. In addition, LiBr, Li ₂ C ₂ , LiCl, LiF, LiH, LiI, LiN ₃ , Li ₃ N, etc. may be used. As the Li source, any one of these may be used alone, or a plurality of these may be used in combination.

The Mn source and the Nb source may each be a single substance, may constitute a compound together with the above Li source, may constitute an oxide together with the above O source, or may constitute a compound together with other elements. may be configured. For example, Mn sources and Nb sources may be used alone or in the form of metal compounds such as oxides, hydroxides, carbonates, nitrates, sulfates, acetates, oxalates, and halogenates. You may do so.

Specifically, Mn sources include manganese alone, MnO, Mn ₃ O ₄ , Mn ₂ O ₃ , MnO 2 , MnO _{3 ,} Mn ₂ O ₇ , Mn(OH) ₂ , MnO(OH) ₂ , Mn( Examples include OH) ₃ , MnCO ₃ , Mn(NO ₃ ) ₂ , MnSO ₄ , Mn(OCOCH ₃ ) ₂ , MnC ₂ O ₄ , MnCl ₂ , MnI2, MnBr ₂ , MnF ₂ , Mn ₂ C, and the like. In addition, MnNb ₂ O ₆ , which is both a Mn source and an Nb source, may be used.
Examples of the Nb source include simple niobium, Nb ₂ O ₅ , NbO ₂ , Nb ₂ O ₃ , NbO, Nb(OH) ₅ , NbCl ₅ , NbI ₅ , NbBr ₅ , NbF ₅ , NbC, and the like.

The proportions of the Li source, Mn source, and Nb source in the lithium metal composite oxide source are such that the molar ratio of lithium element, manganese element, and niobium element is close to the molar ratio of each element in the target product, that is, the lithium metal composite oxide powder. You can set it so that
For example, if the target object is Li _1.2 Mn _0.6 Nb _0.2 O ₂ , the molar ratio of lithium element to manganese element in the lithium metal composite oxide source is about 5:2 to 3:2. is preferable, and it is presumed that the closer the molar ratio is to 2:1, the better.
Further, the molar ratio of lithium element to niobium element in the lithium metal composite oxide source is preferably about 10:1 to 4:1, and it is presumed that the closer the molar ratio is to 6:1, the better.
The molar ratio of manganese element to niobium element in the lithium metal composite oxide source is preferably about 7:2 to 5:2, and it is presumed that the closer the molar ratio is to 3:1, the better.

The manufacturing method of the present invention is carried out using a plasma generator. Plasma may be generated by arc discharge, multiphase arc discharge, high frequency electromagnetic induction, microwave heating discharge, or the like. The manufacturing method of the present invention can be regarded as a method of manufacturing lithium metal composite oxide powder by a thermal plasma method.

In the case of a high frequency electromagnetic induction type plasma generator, the frequency may be, for example, within the range of 0.5 to 400 MHz, preferably within the range of 1 to 80 MHz. The plasma output may be, for example, within the range of 3 to 300 kW, preferably within the range of 5 to 100 kW. The pressure within the plasma generator may be set appropriately, and can be, for example, within a range of 10 kPa to atmospheric pressure. The average particle size of the lithium metal composite oxide powder of the present invention can be changed by varying the plasma output and the pressure within the plasma generator. For example, by increasing the plasma output, the average particle size of the lithium metal composite oxide powder of the present invention can be reduced.

The inlet flow is generated by the flow of gas toward the plasma. Considering the stability of the plasma, it is preferable that the main flow is a gas that can be used under the plasma. The gas constituting the introduced flow, that is, the introduced gas, is preferably a rare gas such as helium or argon. An example of the flow rate of the introduced gas is 20 to 120 L/min.

Although it depends on the type of plasma generator, in the manufacturing method of the present invention, the introduced gas is introduced into the coil separately from the carrier gas and carrier gas that carry the above-mentioned Li source, Mn source, Nb source, and O source. It is preferable to employ an inner gas and a process gas for placing the plasma generation site under an inert atmosphere.

An example of the flow rate of the carrier gas is 1 to 10 L/min. An example of the flow rate of the inner gas is 1 to 10 L/min. An example of the flow rate of the process gas is 15 to 100 L/min.

The introduced gas may or may not contain oxygen gas. When the introduced gas contains oxygen gas, the oxygen gas can be considered as an O source. Note that the O source in the manufacturing method of the present invention is not limited to a gaseous one, and may constitute a compound together with, for example, at least one of a Li source, a Mn source, and a Nb source. In this case, the introduced gas does not need to contain oxygen gas.

As will be described later, in the examples, when an introduced gas not containing oxygen gas was used, the generation of by-products was significantly suppressed. That is, in the manufacturing method of the present invention, it is preferable that the oxygen concentration of the introduced gas is low, and it is particularly preferable that the introduced gas does not contain oxygen. A preferable range of the oxygen concentration of the introduced gas is 5% by volume when the total volume of the introduced gases, such as the above-mentioned carrier gas, inner gas, process gas, etc., constituting the introduced flow is 100% by volume. %, less than 3.5% by volume, less than 2% by volume, less than 1% by volume, less than 0.5% by volume, and 0% by volume.

The production mechanism of the lithium metal composite oxide powder of the present invention will be discussed. The temperature inside the plasma is about 8000 to 20000°C. The lithium metal composite oxide source introduced into the plasma is considered to be in a vaporized or decomposed state within the plasma. It is believed that the lithium element, manganese element, niobium element, and oxygen element contained in the lithium metal composite oxide source each exist as high-temperature gases in the plasma.

Here, each of the above elements within the plasma moves out of the plasma by flowing together with the introduced gas or falling under its own weight. At this time, the temperature of the atmosphere in which each element is placed drops rapidly, and the temperature of the gas containing each element also drops rapidly. As the temperature decreases, each of the above elements undergoes a phase transition in the order of gas phase → liquid phase → solid phase.
Among lithium, manganese, niobium, and their compounds, metallic niobium has the highest nucleation temperature. Therefore, in the production method of the present invention, metal niobium is first nucleated, and then lithium and manganese are condensed on the crystal nuclei of the metal niobium with oxidation, thereby producing the target lithium metal composite oxide. , for example, it is assumed that the above-mentioned Li _1.2 Mn _0.6 Nb _0.2 O ₂ is generated.

As will be described later, in the manufacturing method of the present invention, oxides such as LiNbO ₃ and LiMn ₂ O ₄ may be produced as by-products if the oxygen concentration in the reaction system is excessive. However, by appropriately controlling the oxygen concentration based on the stoichiometric ratio of each element in the target product, it is possible to synthesize the target lithium metal composite oxide while reducing these byproducts. . Of course, it is preferable to appropriately control the amounts of not only the oxygen element but also the lithium element, the manganese element, and the niobium element based on the stoichiometric ratio.

In order to introduce each element into the plasma at a ratio based on the stoichiometric ratio, lithium containing each element at a ratio based on the stoichiometric ratio is necessary, rather than introducing each element separately into the plasma. It is more rational to prepare a metal composite oxide source and bring the prepared lithium metal composite oxide source into the plasma.
Therefore, it can be said that it is preferable to bring the oxygen element into the plasma as a compound with lithium element, manganese element, or niobium element than to bring it into the plasma as part of the introduced gas as oxygen gas. That is, in the production method of the present invention, it is preferable that the introduced gas constituting the introduced flow does not contain oxygen gas, and in addition, the lithium metal composite oxide source contains at least one selected from lithium element, niobium element, and manganese element. More preferably, it contains a compound with oxygen element.

For example, when the target object is Li _1.2 Mn _0.6 Nb _0.2 O ₂ , the molar ratio of lithium element to oxygen element in the lithium metal composite oxide source is 1.2:1 to 0.3. :1 is preferable, and it is presumed that the closer the molar ratio is to 0.6:1, the better. The molar ratio of manganese element to oxygen element in the lithium metal composite oxide source is preferably about 0.6:1 to 0.15:1, and the closer the molar ratio is to 0.3:1, the better. Guessed. Further, the molar ratio of niobium element to oxygen element in the lithium metal composite oxide source is preferably about 0.2:1 to 0.05:1, and the closer the molar ratio is to 0.1:1, the more It is presumed to be good.

According to the manufacturing method of the present invention, nano-level lithium metal composite oxide powder can be obtained. This is considered to be mainly due to the fact that the manufacturing method of the present invention uses a thermal plasma method.
In other words, in the production method of the present invention, the plasma used to synthesize the lithium metal composite oxide has a very high temperature, and the high temperature range is only within the plasma, so the range is very narrow compared to, for example, an electric furnace. It is. Therefore, after passing through the plasma, the lithium metal composite oxide source introduced into the plasma is rapidly cooled and becomes a lithium metal composite oxide. Due to such rapid cooling, crystal growth of the lithium metal composite oxide is suppressed, so the lithium metal composite oxide powder obtained by the production method of the present invention has extremely fine particles with an average particle size on the nano level. Composed of lithium metal composite oxide particles.
In order to rapidly cool down the lithium metal composite oxide source heated to a high temperature in the plasma, it is reasonable to appropriately control the flow rate of the introduced flow. Preferred ranges of the flow rate of the introduced flow include, for example, 20 L/min or more, 30 L/min or more, 50 L/min or more, and 60 L/min or more. There is no upper limit to the preferable flow rate, but if I had to choose one, it would be reasonable to set it to 200 L/min or less.

The lithium metal composite oxide powder obtained by the production method of the present invention is composed of a large number of lithium metal composite oxide particles. As described above, the lithium metal composite oxide particles constituting the lithium metal composite oxide powder of the present invention (hereinafter referred to as the particles of the present invention) are rapidly cooled from a high temperature state to around room temperature. There is almost no period for crystal growth. Therefore, the particles of the present invention are prevented from becoming acicular crystals with specific axes grown, which can be obtained by common manufacturing methods. As a result, the particles of the present invention contained in the lithium metal composite oxide powder of the present invention have a shape with uniform crystal growth rate on each axis.

The particles of the present invention constituting the lithium metal composite oxide powder of the present invention preferably have a crystallite diameter within the range of 0.1 nm to 150 nm, more preferably within the range of 1 nm to 100 nm, and preferably 50 nm to 100 nm. It is more preferably in the range of ~90 nm, and even more preferably in the range of 60 to 80 nm. The crystallite diameter of the particles of the present invention can be calculated using the Scherrer equation based on the half-width of the diffraction peak and the diffraction angle obtained by X-ray diffraction. In addition, when the said diffraction peak is plural, a plurality of crystallite diameters may be calculated based on each diffraction peak, and the arithmetic mean value may be regarded as the crystallite diameter of the particle|grains of this invention.

The average particle diameter of the lithium metal composite oxide powder of the present invention is preferably in the range of 10 nm to 400 nm, more preferably in the range of 30 nm to 150 nm, and even more preferably in the range of 50 nm to 100 nm. The average particle diameter here refers to the arithmetic value of the diameter of the circumscribed circle of the observed particle image when the lithium metal composite oxide powder of the present invention is observed with an electron microscope such as a scanning electron microscope or a transmission electron microscope. Means the average value. For example, when a rectangular particle image is observed, its circumscribed circle is created and the diameter of the circumscribed circle is measured. In this way, the diameter of each circumscribed circle is measured for, for example, 200 particles, and the arithmetic mean value is calculated. This value is the average particle diameter.

In the production method of the present invention, if the cooling rate of the gas flow containing the lithium metal composite oxide source is increased, the crystal growth of the crystal nuclei in the lithium metal composite oxide is interrupted at an early stage, so that the crystal nuclei become finer. It can also be said that lithium metal composite oxide particles having a uniform shape can be obtained.

Therefore, in order to obtain the lithium metal composite oxide powder of the present invention containing finer particles of the present invention, in the production method of the present invention, the passing flow after the introduction flow passes through the plasma must be added to the passing flow. It can be said that it is better to provide a step of cooling with opposing cooling gas flows.

Examples of the gas for the cooling gas flow include rare gases such as helium and argon, oxygen, and air, and a mixture of these may be used. As with the introduction gas for the above-mentioned introduction flow, it is preferable to use a gas that does not contain oxygen gas as the cooling gas flow.
The temperature of the cooling gas stream may be at room temperature or below room temperature. The flow rate of the cooling gas may be any flow rate smaller than the introduced flow, for example, within the range of 1 to 30 L/min.

In addition, when the lithium metal composite oxide powder of the present invention composed of fine particles of the present invention is used as a positive electrode active material of a battery, for example, high-speed charging and discharging can reduce the reaction resistance of the battery. It is expected to have effects such as being able to show capacity.

The lithium metal composite oxide powder of the present invention can be used as a positive electrode active material for batteries as described above. Hereinafter, the positive electrode comprising the lithium metal composite oxide powder of the present invention will be referred to as the positive electrode of the present invention, and the lithium ion secondary battery comprising the positive electrode of the present invention will be referred to as the lithium ion secondary battery of the present invention.

(Lithium ion secondary battery)
The positive electrode in the lithium ion secondary battery of the present invention includes a current collector and a positive electrode active material layer formed on the surface of the current collector.

As described above, the lithium metal composite oxide powder of the present invention is used as the positive electrode active material. The positive electrode active material layer in the lithium ion secondary battery of the present invention contains other known positive electrode active materials, binders, conductive aids, and other additives in addition to the lithium metal composite oxide powder of the present invention. It is possible.

Examples of preferable ranges for the amount of the positive electrode active material when the entire positive electrode active material layer is 100% by mass are 30 to 100% by mass, 40 to 90% by mass, and 50 to 80% by mass. Other examples include 50 to 99% by mass, 60 to 98% by mass, and 70 to 97% by mass.

The binder plays a role of binding the positive electrode active material and the conductive additive to the surface of the current collector. As a binder, fluororesins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, poly( Examples include acrylic resins such as meth)acrylic acid, styrene-butadiene rubber, and carboxymethyl cellulose. These binders may be used alone or in combination.

Although the amount of the binder is not particularly limited, the amount of the binder in the positive electrode active material layer is preferably in the range of 0.5 to 10% by mass, and preferably in the range of 1 to 7% by mass. More preferably, the amount is in the range of 2 to 5% by mass. If the blending amount of the binder is too small, the moldability of the positive electrode active material layer may deteriorate. Furthermore, if the amount of the binder is too large, the amount of the positive electrode active material in the positive electrode active material layer will be relatively reduced, which is not preferable.

The conductive agent may be any chemically inert electronic high conductor, and examples thereof include carbonaceous fine particles such as carbon black, graphite, vapor grown carbon fiber, and various metal particles. . Examples of carbon black include acetylene black, Ketjen black (registered trademark), furnace black, and channel black. These conductive aids can be added to the positive electrode active material layer alone or in combination of two or more.

Although the shape of the conductive aid is not particularly limited, in view of its role, it is preferable that the average particle diameter of the conductive aid is small. A preferable average particle size of the conductive additive is 10 μm or less, and a more preferable average particle size is from 0.01 to 1 μm.

Although the amount of the conductive additive in the positive electrode active material layer is not particularly limited, it is preferably in the range of 0.5 to 10% by mass, and preferably in the range of 1 to 7% by mass. It is preferably in the range of 2 to 5% by weight, particularly preferably.

Known additives such as a dispersant other than the conductive aid and the binder can be used.

The current collector is a chemically inert electronic high conductor that allows current to continue flowing through the electrodes during discharging or charging of the lithium ion secondary battery. The current collector may be at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel. An example is a metal material. The current collector may be coated with a known protective layer. A current collector whose surface has been treated by a known method may be used as the current collector.

The current collector can take the form of a foil, sheet, film, wire, rod, mesh, or the like. Therefore, as the current collector, for example, metal foil such as copper foil, nickel foil, aluminum foil, or stainless steel foil can be suitably used. When the current collector is in the form of a foil, sheet, or film, the thickness is preferably within the range of 1 μm to 100 μm.

In order to manufacture a positive electrode, the above lithium metal composite oxide powder is mixed with other materials and solvents as necessary, and the resulting positive electrode active material layer composition is applied or pressure-bonded to the above current collector. Just do it.
Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The amount of the solvent used is preferably such that the composition for the positive electrode active material layer becomes a slurry.

In order to apply the positive electrode active material layer composition to the current collector, conventionally known methods such as roll coating, die coating, dip coating, doctor blade method, spray coating, curtain coating, etc. may be used. .

One embodiment of the lithium ion secondary battery of the present invention includes a battery comprising the positive electrode, negative electrode, electrolyte, and separator of the present invention.

The negative electrode includes a current collector and a negative electrode active material layer formed on the surface of the current collector. As for the current collector, those described in connection with the positive electrode may be appropriately employed. The negative electrode active material layer contains a negative electrode active material and, if necessary, a conductive additive, a binder, an additive, and the like.

Examples of the negative electrode active material include carbon-based materials capable of intercalating and deintercalating lithium, elements that can be alloyed with lithium, compounds containing elements that can be alloyed with lithium, and polymeric materials.

Examples of carbon-based materials include non-graphitizable carbon, graphite, cokes, graphites, glassy carbons, fired organic polymer compounds, carbon fibers, activated carbon, and carbon blacks. Here, the term "fired organic polymer compound" refers to a material obtained by carbonizing a polymer material such as phenols or furans by firing it at an appropriate temperature.

Specific examples of elements that can be alloyed with lithium include Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, and Si. , Ge, Sn, Pb, Sb, and Bi, with Si or Sn being particularly preferred.
Specific examples of compounds having elements that can be alloyed with lithium include ZnLiAl, AlSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi2 _{, CrSi2} , _Cu5Si , FeSi2 _, MnSi2, _NbSi2 , _{TaSi2 , VSi2} , _WSi2 , _ZnSi2 , SiC, _{Si3N4 , Si2N2O} , _SiOv (0 _< v ≦2), SnO _w (0<w≦2), SnSiO ₃ , LiSiO or LiSnO, particularly SiO _x (0.3≦x≦1.6, or 0.5≦x≦1.5). is preferred.

Among these, the negative electrode active material preferably contains a Si-based material containing Si. The Si-based material is preferably made of silicon or/and a silicon compound capable of intercalating and deintercalating lithium ions, and is preferably SiOx (0.5≦x≦1.5), for example. Although silicon has a large theoretical charge/discharge capacity, silicon has a large volume change during charging and discharging. Therefore, by using SiOx containing silicon as the negative electrode active material, the volume change of silicon can be alleviated.
Moreover, it is preferable that the Si-based material has a Si phase and a SiO ₂ phase. The Si phase is made of simple silicon and is a phase that can absorb and release Li ions, and expands and contracts as Li ions are absorbed and released. The SiO ₂ phase is made of SiO ₂ and serves as a buffer phase that absorbs the expansion and contraction of the Si phase. Preferred is a Si-based material in which the Si phase is covered with _two SiO2 phases. Furthermore, it is preferable that a plurality of finely divided Si phases are coated with two SiO ₂ phases and integrally form particles. In this case, the volume change of the entire Si-based material can be effectively suppressed.
The mass ratio of the SiO ₂ phase to the Si phase in the Si-based material is preferably 1 to 3. When the mass ratio is less than 1, the expansion and contraction of the Si-based material increases, and there is a risk that cracks may occur in the negative electrode active material layer containing the Si-based material. On the other hand, when the mass ratio exceeds 3, the amount of intercalation and release of Li ions in the negative electrode active material decreases, and the electric capacity per unit mass of the negative electrode of the battery decreases.

Further, as a compound having an element capable of alloying with lithium, a tin compound such as a tin alloy (Cu--Sn alloy, Co--Sn alloy, etc.) can be exemplified.
Specific examples of polymeric materials include polyacetylene and polypyrrole.
As the negative electrode active material, a Si material obtained by heating layered polysilane obtained by treating CaSi ₂ with an acid such as hydrochloric acid or hydrofluoric acid at 300 to 1000° C. may be used. Furthermore, the above-mentioned Si material may be heated together with a carbon source and coated with carbon, and then used as the negative electrode active material.

As the negative electrode active material, one or more of the above materials can be used.
Regarding the conductive additive, binder, and other additives used in the negative electrode, those explained in the positive electrode may be suitably employed in the same proportions.

The electrolytic solution includes a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.
As the non-aqueous solvent, cyclic carbonates, cyclic esters, chain carbonates, chain esters, ethers, etc. can be used. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, and examples of the cyclic ester include gamma-butyrolactone, 2-methyl-gamma-butyrolactone, acetyl-gamma-butyrolactone, and gamma-valerolactone. Examples of chain carbonates include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, and ethylmethyl carbonate, and examples of chain esters include propionic acid alkyl esters, malonic acid dialkyl esters, acetic acid alkyl esters, and the like. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. As the non-aqueous solvent, a compound in which part or all of the hydrogens in the chemical structure of the above-mentioned specific solvents are replaced with fluorine may be used.
The electrolytic solution may use one of these nonaqueous solvents, or a plurality of them may be used in combination.

Examples of the electrolyte include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , and LiN(CF ₃ SO ₂ ) ₂ .
As an electrolytic solution, 0.5 mol/L to 1.7 mol of a lithium salt such as LiClO ₄ , LiPF ₆ , LiBF ₄ , or LiCF ₃ SO ₃ is added to a nonaqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, or diethyl carbonate. An example is a solution in which the compound is dissolved at a concentration of about /L.

The separator separates the positive electrode and the negative electrode, and allows lithium ions to pass through while preventing current short-circuiting due to contact between the two electrodes. Separators include synthetic resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polyamide), polyester, polyacrylonitrile, polysaccharides such as cellulose and amylose, natural materials such as fibroin, keratin, lignin, and suberin. Examples include porous bodies, nonwoven fabrics, woven fabrics, etc. using one or more electrically insulating materials such as polymers and ceramics. Further, the separator may have a multilayer structure.

Next, a method for manufacturing a lithium ion secondary battery of the present invention will be explained.

If necessary, a separator is sandwiched between the above-described positive electrode and negative electrode to form an electrode body. The electrode body may be of either a laminated type in which a positive electrode, a separator, and a negative electrode are stacked, or a wound type in which a laminated body of a positive electrode, a separator, and a negative electrode is wound. After connecting the positive electrode current collector and negative electrode current collector to the positive electrode terminal and negative electrode terminal leading to the outside using current collecting leads, etc., add an electrolyte to the electrode body to form a lithium ion secondary battery. . Further, the lithium ion secondary battery of the present invention may be capable of being charged and discharged in a voltage range suitable for the type of active material contained in the electrode.
The shape of the lithium ion secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, a laminate shape, etc. can be adopted.

The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be any vehicle that uses electric energy from a lithium ion secondary battery for all or part of its power source, and may be, for example, an electric vehicle, a hybrid vehicle, or the like. When a lithium ion secondary battery is installed in a vehicle, a plurality of lithium ion secondary batteries may be connected in series to form a battery pack. Devices equipped with lithium ion secondary batteries include, in addition to vehicles, various home appliances, office equipment, and industrial equipment powered by batteries, such as personal computers and mobile communication devices. Furthermore, the lithium ion secondary battery of the present invention can be used in power storage devices and power smoothing devices for wind power generation, solar power generation, hydroelectric power generation, and other power systems, power supply sources for motive power and/or auxiliary equipment of ships, etc., aircraft, Power supply sources for power and/or auxiliary equipment such as spacecraft, auxiliary power sources for vehicles that do not use electricity as a power source, power sources for mobile household robots, system backup power sources, power sources for uninterruptible power supplies, It may also be used in a power storage device that temporarily stores power necessary for charging at a charging station for an electric vehicle.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. Without departing from the gist of the present invention, the present invention can be implemented in various forms with modifications and improvements that can be made by those skilled in the art. Note that some of the lithium metal composite oxide powders of the present invention contain impurities.

EXAMPLES Below, the present invention will be explained in more detail with reference to Examples. Note that the present invention is not limited to these Examples.

(Example 1)
The lithium metal composite oxide powder of Example 1 was manufactured using the plasma generator shown in FIG. In the plasma generator shown in FIG. 1, black arrows represent cooling water.

Li ₂ CO ₃ was prepared as a Li source and an O source, MnO ₂ was prepared as a Mn source and an O source, and Nb ₂ O ₅ was prepared as an Nb source and an O source. Li ₂ CO ₃ , MnO ₂ , and Nb ₂ O ₅ are mixed in amounts such that the molar ratio of lithium element, manganese element, and niobium element is 1.2:0.6:0.2 to form a mixed powder. , the mixed powder was placed in a powder feeder. The molar ratio of lithium element to oxygen element in the mixed powder is 1.2:3.5, the molar ratio of manganese element to oxygen element is 0.6:3.5, and the molar ratio of niobium element to oxygen element is 1.2:3.5. The molar ratio of was 0.2:3.5.

A mixed gas of argon and oxygen mixed at a volume ratio of 57.5:2.5 was supplied as a process gas into the plasma generator at a rate of 60 L/min.
In addition, argon was supplied as an inner gas at a rate of 5 L/min, and argon was supplied as a carrier gas at a rate of 3 L/min. Electric power was supplied from the power supply device, and a magnetic field with a frequency of 4 MHz was applied to the coil to generate plasma with an output of 25 kW. Note that the pressure inside the plasma generator was atmospheric pressure.
The oxygen gas concentration of the introduced flow at this time was about 3.68% by volume. Further, the flow rate of the flow introduced into the plasma generator was the sum of the process gas, inner gas, and carrier gas, that is, 68 L/min.

After stabilizing the plasma, the powder feeder was activated, and the mixed powder was introduced into the plasma together with the carrier gas at a feed rate of 300 mg/min. The powder released together with the flow that passed through the plasma was collected and used as the lithium metal composite oxide powder of Example 1.

Although a cooling gas was not used in Example 1, a cooling gas such as argon as described above was used, and the passing flow after the introduced flow passed through the plasma was replaced by a cooling gas flow opposite to the passing flow. A cooling step may also be performed. In this case, it is thought that the cooling rate of the powder increases and a powder consisting of finer particles is obtained.

Using the lithium metal composite oxide powder of Example 1 above, a positive electrode and a lithium ion secondary battery of Example 1 were manufactured as follows.
5 parts by mass of the lithium metal composite oxide powder of Example 1 as a positive electrode active material, 4 parts by mass of acetylene black as a conductive aid, and 1 part by mass of polytetrafluoroethylene as a binder were weighed and mixed in an agate mortar, A composition for positive electrode active material was obtained by processing it into a clay-like form. A mesh-shaped aluminum was prepared as a current collector, and the positive electrode active material composition was pressure-bonded to this to obtain the positive electrode of Example 1. All work was carried out in a glove box with a moisture concentration of 1 ppm or less, which was purged with argon gas.

A lithium ion secondary battery (half cell) was produced using the positive electrode of Example 1 produced by the above procedure as a working electrode. The counter electrode was a metallic lithium foil.
A working electrode, a counter electrode, and a separator (a glass filter manufactured by Hoechst Celanese and "Celgard 2400" manufactured by Celgard) interposed between the two electrodes were provided to form an electrode body. This electrode body was housed in a battery case (CR2032 type coin battery member, manufactured by Hosen Co., Ltd.). A non-aqueous electrolyte in which LiPF ₆ was dissolved at a concentration of 1M in a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 3:7 was injected into the battery case, and the battery case was sealed. A lithium ion secondary battery was obtained.

(Example 2)
The lithium metal composite oxide powder of Example 2 was produced in the same manner as in Example 1 except that only argon gas was supplied as the process gas at a rate of 60 L/min. Further, using the lithium metal composite oxide powder of Example 2, a positive electrode of Example 2 and a lithium ion secondary battery of Example 2 were manufactured in the same manner as in Example 1.

(Comparative example 1)
Comparative Example 1 is a method for producing lithium metal composite oxide powder by a solid phase method.
In Comparative Example 1, Li ₂ CO ₃ was prepared as the Li source and O source, Mn ₂ O ₃ was prepared as the Mn source and O source, and Nb ₂ O ₅ was prepared as the Nb source and O source. These powders were weighed so that the molar ratio of lithium element, manganese element, and niobium element was 1.2:0.6:0.2, and these powders were charged into a ball mill. Then, mixing was performed using a ball mill at about 100 rpm for 24 hours to obtain a mixture. The mixture was molded and then heated and fired at 1000° C. for 12 hours in an argon gas atmosphere to obtain a lithium metal composite oxide powder of Comparative Example 1, which is a fired product.
The lithium metal composite oxide powder of Comparative Example 1 and acetylene black as a conductive additive were weighed so as to have a mass ratio of 5:2, and placed in a ball mill. Then, mixing using a ball mill was performed at 600 rpm for 0.5 hours to obtain a mixture of Comparative Example 1 containing the lithium metal composite oxide of Comparative Example 1 and acetylene black.

The mixture of Comparative Example 1, acetylene black, and polytetrafluoroethylene as a binder were mixed in a mortar to obtain a clay-like positive electrode active material layer composition. In the positive electrode active material layer composition, the mass ratio of the lithium metal composite oxide, acetylene black, and polytetrafluoroethylene of Comparative Example 1 was 5:4:1.
A mesh-shaped aluminum was prepared as a current collector, and the composition for a positive electrode active material layer was pressure-bonded to this to obtain a positive electrode of Comparative Example 1. A lithium ion secondary battery of Comparative Example 1 was manufactured in the same manner as Example 1 using the positive electrode of Comparative Example 1.

(Comparative example 2)
Comparative Example 2 is a method of producing lithium metal composite oxide powder by the solid phase method similarly to Comparative Example 1.
Except that Li ₂ CO ₃ , Mn ₂ O ₃ and Nb ₂ O ₅ were weighed so that the molar ratio of lithium element, manganese element and niobium element was 1.3:0.3:0.4. A lithium metal composite oxide powder of Comparative Example 2 was obtained in the same manner as Comparative Example 1.

(Evaluation test 1)
The lithium ion secondary battery of Example 2 and the lithium ion secondary battery of Comparative Example 1 were charged from 1.5V to 4.8V and discharged from 4.8V to 1.5V at room temperature for 0. A charge/discharge cycle test was conducted in the order of 03C, 0.1C, 0.5C, 1C, 2C and 5C rates. The results of evaluation test 1 are shown in FIG. 2.
Note that the description here assumes that the counter electrode is a negative electrode and the working electrode is a positive electrode. 1C means the current value required to fully charge or discharge a battery in one hour at a constant current.
The vertical axis (positive electrode utilization rate) in Figure 2 is the discharge capacity at each C rate expressed as a percentage when the discharge capacity at 1.5V at 0.03C is 100% for each lithium ion secondary battery. It is.

As shown in FIG. 2, the lithium ion secondary battery of Example 2 exhibited a larger capacity than the lithium ion secondary battery of Comparative Example 1 even at a high C rate. This result is considered to mean that in the lithium ion secondary battery of Example 2, the battery reaction at the positive electrode was performed more efficiently than in the lithium ion secondary battery of Comparative Example 1.

(Evaluation test 2)
The lithium metal composite oxide powder of Example 1 and the lithium metal composite oxide powder of Comparative Example 2 were observed using a scanning electron microscope (SEM). A SEM image of the lithium metal composite oxide powder of Example 1 is shown in FIG. 3, and a SEM image of the lithium metal composite oxide powder of Comparative Example 2 is shown in FIG.

Based on FIGS. 3 and 4, the average particle diameter of the lithium metal composite oxide powder of Example 1 and the average particle diameter of the lithium metal composite oxide powder of Comparative Example 2 were measured. As a result, it was found that the average particle size of the lithium metal composite oxide powder of Example 1 was 47 nm, and the average particle size of the lithium metal composite oxide powder of Comparative Example 2 was 3.3 μm.
The average particle diameter of the lithium metal composite oxide powder of Example 2 was similarly measured, and the average particle diameter was 43 nm, and the average particle diameter of the lithium metal composite oxide powder of Comparative Example 1 was also When measured, the average particle diameter was 3.1 μm.
From the above results, the lithium metal composite oxide powder of Example 1 and the lithium metal composite oxide powder of Example 2 synthesized by the thermal plasma method are different from the lithium metal composite oxide powder of Comparative Example 2 synthesized by the solid phase method. It can be seen that the average particle size is very small compared to the powder. In other words, according to the production method of the present invention using a thermal plasma method, it is possible to obtain lithium metal composite oxide particles having a much smaller particle size than the conventional production method using a solid phase method.

Considering the results of Evaluation Test 2 and the results of Evaluation Test 1 described above, the difference in rate characteristics between the lithium ion secondary battery of Example 2 and the lithium ion secondary battery of Comparative Example 1 is due to the difference in the rate characteristics of Example 2. It is presumed that the difference in average particle size between the lithium metal composite oxide powder of No. 2 and the lithium metal composite oxide powder of Comparative Example 1 is largely responsible.

That is, in the lithium metal composite oxide powder of Example 2 having a small average particle diameter, the specific surface area of the lithium metal composite oxide particles is large. Therefore, in the lithium ion secondary battery of Example 2 in which the particles were used in the positive electrode, it is thought that the battery reaction at the positive electrode occurred frequently.
From the above results, according to the production method of the present invention, by synthesizing a lithium metal composite oxide by a thermal plasma method, fine particulate lithium metal composite oxide, which is useful as a positive electrode active material of lithium ion secondary batteries, can be produced. It can be said that things can be manufactured.

(Evaluation test 3)
The lithium ion secondary battery of Example 1 and the lithium ion secondary battery of Example 2 were charged from 1.5V to 4.8V and discharged from 4.8V to 1.5V at 0.03C, respectively. A charge/discharge cycle test was conducted. Furthermore, the lithium ion secondary battery of Comparative Example 1 was also subjected to a charge/discharge cycle test in which charging from 1.5V to 4.8V and discharging from 4.8V to 1.5V were repeated. The results of the cycle test of the lithium ion secondary battery of Example 1 are shown in FIG. 5, the results of the cycle test of the lithium ion secondary battery of Example 2 are shown in FIG. The results of the cycle test are shown in FIG.

As shown in FIGS. 5 to 7, the lithium ion secondary battery of Example 1 and the lithium ion secondary battery of Example 2 have a lower capacity as the cycle progresses than the lithium ion secondary battery of Comparative Example 1. The decrease is small. In other words, the lithium ion secondary battery of Example 1 using the positive electrode active material produced by the thermal plasma method and the lithium ion secondary battery of Example 2 using the positive electrode active material produced by the solid phase method are different from the lithium ion secondary battery of Comparative Example 1 using the positive electrode active material produced by the solid phase method. Excellent cycle characteristics compared to secondary batteries.

Further, as shown in FIGS. 5 and 6, the lithium ion secondary battery of Example 2 shows a smaller decrease in capacity as the cycle progresses than the lithium ion secondary battery of Example 1. In other words, the lithium ion secondary battery of Example 2 has better cycle characteristics than the lithium ion secondary battery of Example 1.

The difference between the lithium ion secondary battery of Example 2 and the lithium ion secondary battery of Example 1 lies in the amount of oxygen supplied during synthesis of the lithium metal composite oxide powder. Therefore, it can be said that in the manufacturing method of Example 2, the amount of oxygen during synthesis of the lithium metal composite oxide powder was appropriate compared to that in the manufacturing method of Example 1.
Furthermore, the difference between the lithium ion secondary battery of Example 2 and the lithium ion secondary battery of Example 1 is whether or not an introduced gas containing oxygen gas was used during the synthesis of the lithium metal composite oxide powder. It can be said that there is. The manufacturing method of Example 2, which uses an introduced gas that does not contain oxygen gas, improves the cycle characteristics of the lithium ion secondary battery compared to the manufacturing method of Example 1, which uses an introduced gas that contains oxygen gas. It can also be said that the positive electrode active material obtained, that is, the lithium metal composite oxide powder can be manufactured.

In addition, according to FIGS. 5 and 6, in the lithium ion secondary battery of Example 1, the oxygen redox region is the same size as the manganese redox region, whereas in the lithium ion secondary battery of Example 2, the oxygen redox region is as large as the manganese redox region. It is thought that in batteries, the redox area of manganese is larger than the redox area of oxygen. It is presumed that the difference in durability between the lithium ion secondary battery of Example 1 and the lithium ion secondary battery of Example 2 described above is due to the size of the oxygen redox area relative to the manganese redox area. .

In other words, in the lithium ion secondary battery of Example 1, since oxygen greatly participates in the charge/discharge reaction of the positive electrode active material, that is, the lithium metal composite oxide, the crystal structure of the lithium metal composite oxide changes with each cycle. It is thought that it was damaged gradually. On the other hand, in the lithium ion secondary battery of Example 2, the amount of oxygen involved in the charge/discharge reaction of the lithium metal composite oxide, which is the positive electrode active material, is small, and as a result, the crystal structure of the lithium metal composite oxide is maintained. It is believed that this product exhibits excellent cycle characteristics.

(Evaluation test 4)
X-ray diffraction of each of the lithium metal composite oxide powders of Examples 1 and 2 was measured using a powder X-ray diffractometer. The results are shown in FIG. In the X-ray diffraction charts obtained from the lithium metal composite oxide powders of Examples 1 and 2, diffraction peaks specific to cubic crystals that can be assigned to the space group Fm-3m were observed in both cases. From this result, according to the manufacturing method of Example 1 and the manufacturing method of Example 2, a cubic lithium metal composite oxide containing lithium element, manganese element, niobium element, and oxygen element and which can be assigned to space group Fm-3m. It turns out that it is possible to synthesize. In the lithium metal composite oxide powder of Example 1, a diffraction peak of LiNbO ₃ and a diffraction peak of LiMn ₂ O ₄ which are not observed in the lithium metal composite oxide powder of Example 2 was confirmed. It can be seen that the production method of Example 2 can suppress by-products compared to the production method of Example 1.

Taking into account the results of Evaluation Test 4 and the results of Evaluation Test 3 above, by adjusting the amount of oxygen supplied during the synthesis of lithium metal composite oxide powder to a suitable amount, the sub-products contained in the lithium metal composite oxide can be It can be said that the amount of living organisms can be reduced and, in turn, the durability of lithium ion secondary batteries can be improved.
Furthermore, by using an introduced gas that does not contain oxygen gas during the synthesis of lithium metal composite oxide powder, it is possible to reduce the amount of byproducts contained in the lithium metal composite oxide, which in turn can improve the performance of lithium ion secondary batteries. It can also be said that durability can be improved.

Claims (5)

A lithium metal composite oxide source containing a lithium element, a niobium element, a manganese element, and an oxygen element is introduced into the plasma with an introduction flow that does not contain oxygen gas, and can belong to the space group Fm-3m. A method for producing a lithium metal composite oxide powder that exhibits a crystalline structure and has an average particle size on the nano level. A lithium metal composite oxide source containing a lithium element, a niobium element, a manganese element, and an oxygen element is introduced into the plasma with an introduction flow that does not contain oxygen gas, and can belong to the space group Fm-3m. A method for producing a lithium metal composite oxide powder that exhibits a crystalline structure and has an average particle size on the nano level (provided that the lithium metal composite oxide source contains an iron element). 3. The manufacturing method according to claim 1, wherein the lithium metal composite oxide source contains a compound of at least one selected from lithium element, niobium element, and manganese element and oxygen element. A step of producing a lithium metal composite oxide powder that exhibits a crystal structure that can be attributed to space group Fm-3m and has an average particle size on the nano-level by the production method according to any one of claims 1 to 3. ,as well as,
A method for manufacturing a positive electrode, comprising the step of manufacturing a positive electrode using the lithium metal composite oxide powder. A method for manufacturing a lithium ion secondary battery, comprising the step of manufacturing a lithium ion secondary battery using the positive electrode obtained by the manufacturing method according to claim 4 .