JP2020158335A - Method for producing lithium metal complex oxide powder - Google Patents

Abstract

To improve the production efficiency of lithium metal complex oxide powder.SOLUTION: A method for producing lithium metal complex oxide powder has the step of introducing a lithium metal complex oxide source containing lithium element, niobium element, manganese element, and oxygen element into plasma, by an introduction flow, the lithium metal complex oxide powder having an average particle size of nano level.SELECTED DRAWING: None

Description

The present invention relates to a lithium metal composite oxide powder containing a lithium element, a niobium element, a manganese element and an oxygen element, a method for producing the same, and 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, a method of producing a Li _x Me _y O ₂ which is a kind of lithium-metal composite oxide is disclosed. Specifically, Patent Document 1 describes a solid state in which a raw material containing Li, a raw material containing O, and a raw material containing Me are weighed and mixed using a mixing device such as a ball mill for 10 hours or more. by reacting to _the effect that can produce a Li x _Me y _{O 2} is disclosed. The synthetic method in which the reaction proceeds in a state where the solid state is maintained by using the solid material is hereinafter referred to as a solid phase method, if necessary.

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

Japanese Unexamined Patent Publication No. 2017-152370

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

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

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

It is a schematic diagram of a plasma generator. It is a graph which shows the rate characteristic of the lithium ion secondary battery of Example 1 and Comparative Example 1. It is an SEM image of the lithium metal composite oxide powder of Example 1. It is an SEM image of the lithium metal composite oxide powder of Comparative Example 1. It is a graph which shows the cycle characteristic of the lithium ion secondary battery of Example 1. FIG. It is a graph which shows the cycle characteristic of the lithium ion secondary battery of Example 2. It is a graph which shows the cycle characteristic of the lithium ion secondary battery of the comparative example 1. FIG. It 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. Unless otherwise specified, the numerical range "x to y" described in the present specification includes the lower limit x and the upper limit y in the range. Then, a numerical range can be constructed by arbitrarily combining these upper and lower limit values and the numerical values listed in the examples. Further, numerical values arbitrarily selected from these numerical values can be set as upper and lower limit values of a new numerical range.

(Lithium metal composite oxide powder)
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 a nano-level average particle size. In the present specification, "the average particle size is at the nano level" means that the average particle size is in the range of 1 nm or more and less than 1000 nm. That is, the average particle size of the lithium metal composite oxide powder obtained by the production method of the present invention is within the above range. Whether or not the average particle size of the lithium metal composite oxide powder obtained by the production method of the present invention is at the nano level can be confirmed by an electron microscope image as described later.
Hereinafter, if necessary, the lithium metal composite oxide powder obtained by the method for producing a lithium metal composite oxide powder of the present invention may be referred to as the lithium metal composite oxide powder of the present invention. In addition, the method for producing a lithium metal composite oxide powder of the present invention may be simply referred to as the method for producing a lithium metal composite oxide powder 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 crystals or a composite of several crystallites.

Hereinafter, the present invention will be described 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 a nano-level average particle size, and is a lithium metal containing lithium element, niobium element, manganese element and oxygen element. It has a step of introducing the composite oxide source into the plasma by the introduction flow.

The lithium metal composite oxide powder of the present invention produced by the production method of the present invention contains powdered lithium metal composite oxide containing lithium element, niobium element, manganese element and oxygen element derived from the 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 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. It is preferably one selected from transition metals, Group 2 elements or rare earths, 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 , and 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 Etc., 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) can be mentioned.
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). As in 0.8 ≦ a + b + c + d ≦ 2.2), the above Li _a Mn _b Nb _c O ₂ may be used as a basic structure and may further contain other doping elements. Further, 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 attributed to the space group Fm-3m. In addition, in "Fm-3m" and the like in the notation of the type of a space group, "-3" represents 3 with an overline.
The lithium metal composite oxide in the present invention may be only one having a crystal structure that can be attributed to the space group Fm-3m, or one that has a crystal structure that can be attributed to the space group Fm-3m and another. It may be a mixture.

The lithium metal composite oxide showing a crystal structure that can be attributed to the space group Fm-3m can show 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 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 preferable. Each range of a, b, and c will be described. More preferable ranges of a include 0.9 ≦ a ≦ 1.25, 1.0 ≦ a ≦ 1.2, and 1.0 <a ≦ 1.2. More preferable ranges of b include 0.3 ≦ b ≦ 0.8, 0.5 ≦ b <0.8, and 0.55 ≦ b ≦ 0.75. As a more preferable range of c, each range of 0.05 ≦ c ≦ 0.5, 0.07 ≦ c ≦ 0.3, and 0.1 ≦ c ≦ 0.25 can be mentioned.

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

The method for producing a lithium metal composite oxide powder of the present invention includes a step of introducing a lithium metal composite oxide source into plasma by 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 be an oxygen gas, and is a raw material that can be a raw material of the lithium metal composite oxide of the present invention in powder form. Any mixture of raw materials may be used. That is, the lithium metal composite oxide source may be the same as the above-mentioned lithium metal composite oxide, may be different, may be a simple substance, or a mixture of a plurality of simple substances. It may be. Furthermore, the lithium metal composite oxide source may have any of solid, liquid, and gaseous properties, or may be a mixture thereof.

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

Hereinafter, if necessary, a lithium metal composite oxide source containing a lithium element is referred to as a Li source, a manganese element-containing source is referred to as an Mn source, and a niobium element-containing source is referred to as an Nb source, and oxygen is used. A source having an oxygen element that can be a gas is called an O source. Considering the handleability of the lithium metal composite oxide source, at least the Li source, the Mn source and the Nb source are preferably in the form of powder. The Li source, the Mn source, and the Nb source may be used alone, or may be used in the state 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, the Mn source and the Nb source, or may be used alone, that is, in the state 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 a manganese element, a niobium element, and an oxygen element in addition to the lithium element. Furthermore, it may be a compound that requires a lithium source and contains elements other than the above.

Such Li source, lithium simple substance, _{or, Li 2 CO 3, LiOH,} LiMn 2 O 4, LiNbO 3, Li 2 O, may be exemplified lithium compound represented by _Li 2 O 2, LiO ₂ it can. _{Other, LiBr, Li 2 C 2,} LiCl, LiF, LiH, LiI, may be used _{LiN 3,} Li 3 N and the like. 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 be simple substances, may form a compound together with the above Li source, may form an oxide together with the above O source, or may form an oxide together with other elements. May be configured. For example, the Mn source and the Nb source may be used alone or in the state of metal compounds such as oxides, hydroxides, carbonates, nitrates, sulfates, acetates, oxalates and halides. You may.

Specifically, as the Mn source, 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 thereof include OH) ₃ , MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , Mn (OCOCH ₃ ) ₂ , MnC ₂ O ₄ , MnCl ₂ , MnI ₂ , MnBr ₂ , MnF ₂ , and Mn ₂ C. In addition, MnNb ₂ O ₆ which is a Mn source and an Nb source may be used.
Examples of the Nb source include niobium alone, 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 ratio of Li source, Mn source and Nb source in the lithium metal composite oxide source is 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. It should be set so as to be.
For example, if the target product 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 the lithium element and the niobium element in the lithium metal composite oxide source is preferably about 10: 1 to 4: 1, and it is presumed that the molar ratio is closer to 6: 1.
The molar ratio of the manganese element to the niobium element in the lithium metal composite oxide source is preferably about 7: 2 to 5: 2, and it is presumed that the molar ratio is closer to 3: 1.

The manufacturing method of the present invention is carried out using a plasma generator. Plasma may be generated by arc discharge, multi-phase arc discharge, high frequency electromagnetic induction, microwave heating discharge, or the like. The production method of the present invention can be regarded as a method for producing a 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, in the range of 0.5 to 400 MHz, preferably in the range of 1 to 80 MHz. The plasma output may be, for example, in the range of 3 to 300 kW, preferably in the range of 5 to 100 kW. The pressure in the plasma generator may be set as appropriate, and can be exemplified in the range of 10 kPa to atmospheric pressure, for example. By fluctuating the plasma output and the pressure in the plasma generator, the average particle size of the lithium metal composite oxide powder of the present invention can be changed. 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 introductory flow is generated by the flow of gas towards the plasma. As the introduction flow, it is preferable to use a gas that can be used under the plasma as the main flow in consideration of the stability of the plasma. As the gas constituting the introduction flow, that is, the introduction gas, a rare gas such as helium or argon is preferable. As the flow rate of the introduced gas, 20 to 120 L / min can be exemplified.

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

The flow rate of the carrier gas can be exemplified by 1 to 10 L / min. As the flow rate of the inner gas, 1 to 10 L / min can be exemplified. As the flow rate of the process gas, 15 to 100 L / min can be exemplified.

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

As will be described later, in the examples, the production of by-products was remarkably suppressed when the introduced gas containing no oxygen gas was used. That is, in the production 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. The preferable range of the oxygen concentration of the introduced gas is 5 volumes when the total volume of the introduced gas, for example, the above-mentioned carrier gas, inner gas, process gas, and other gases constituting the introduced flow is 100% by volume. Each range of less than%, 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 can be mentioned.

The mechanism for producing the lithium metal composite oxide powder of the present invention will be considered. The temperature in 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 in the plasma. Then, it is considered that the lithium element, the manganese element, the niobium element and the oxygen element contained in the lithium metal composite oxide source each exist as a high-temperature gas in the plasma.

Here, each of the above elements in the plasma moves out of the plasma by flowing with the introduced gas or falling by its own weight. At this time, the temperature of the atmosphere in which each of the above elements is placed drops sharply, and the temperature of the gas containing each element also drops sharply. As the temperature drops, each of the above elements undergoes a phase transition in the order of gas phase → liquid phase → solid phase.
Of lithium, manganese, niobium and their compounds, the metal niobium has the highest nucleation temperature. Therefore, in the production method of the present invention, first, metal niobium is formed into nuclei, and then lithium and manganese are condensed with oxidation in the crystal nuclei of the metal niobium, thereby condensing the target lithium metal composite oxide. For example, it is presumed that the above-mentioned Li _1.2 Mn _0.6 Nb _0.2 O ₂ is produced.

As will be described later, in the production method of the present invention, oxides such as LiNbO ₃ and LiMn ₂ O ₄ may be produced as a by-product when 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 by-products. .. Of course, it is preferable to appropriately control not only the amount of oxygen element but also the amount of lithium element, manganese element, and niobium element based on the chemical quantity theory ratio.

In order to introduce each element into the plasma at a ratio based on the chemical ratio, rather than bringing each element into the plasma separately, lithium containing each element at a ratio based on the chemical ratio in advance. It is 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 the lithium element, the manganese element, or the niobium element, rather than bringing it into the plasma as a part of the introduced gas as an oxygen gas. That is, in the production method of the present invention, it is preferable that the introduction gas constituting the introduction flow does not contain oxygen gas, and in addition, the lithium metal composite oxide source is at least one selected from lithium element, niobium element and manganese element. It is more preferable to contain a compound with an oxygen element.

For example, when the target product is Li _1.2 Mn _0.6 Nb _0.2 O ₂ , the molar ratio of the lithium element to the oxygen element in the lithium metal composite oxide source is 1.2: 1 to 0.3. It is preferably about 1: 1, and it is presumed that the molar ratio closer to 0.6: 1 is 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 molar ratio is better closer to 0.3: 1. Guess. Further, the molar ratio of the niobium element and the 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. Presumed to be good.

According to the production method of the present invention, a nano-level lithium metal composite oxide powder can be obtained. It is considered that this is mainly due to the fact that the production method of the present invention uses the thermal plasma method.
That is, in the production method of the present invention, the plasma used for synthesizing the lithium metal composite oxide has a very high temperature, and the high temperature range is only in the plasma, so that the range is very narrow as compared with, for example, an electric furnace. Is. Therefore, the lithium metal composite oxide source introduced into the plasma is rapidly cooled after passing through the plasma to become a lithium metal composite oxide. Since the crystal growth of the lithium metal composite oxide is suppressed due to such rapid cooling, the lithium metal composite oxide powder obtained by the production method of the present invention has a very fine average particle size of nano-level. It is composed of lithium metal composite oxide particles.
In order to rapidly cool the lithium metal composite oxide source heated to a high temperature in the plasma, it is rational to appropriately control the flow rate of the introduction flow. The preferable range of the flow rate of the introduced flow can be exemplified in each range of 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 it is strongly mentioned, it is rational 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 near room temperature, so that the lithium metal composite oxide particles are rapidly cooled. There is almost no period for crystal growth. Therefore, the particles of the present invention are prevented from becoming acicular crystals having a specific axis grown, which can be obtained by a general production method. As a result, the particles of the present invention contained in the lithium metal composite oxide powder of the present invention have a shape in which the crystal growth rate of each axis is not uneven.

The particles of the present invention constituting the lithium metal composite oxide powder of the present invention preferably have a crystallite diameter in the range of 0.1 nm to 150 nm, more preferably in the range of 1 nm to 100 nm, and more preferably 50 nm. It is more preferably in the range of ~ 90 nm, and even more preferably in the range of 60-80 nm. The crystallite diameter of the particles of the present invention can be calculated using Scheller's equation based on the half width and diffraction angle of the diffraction peak obtained by the X-ray diffraction method. When there are a plurality of diffraction peaks, a plurality of crystallite diameters may be calculated based on each diffraction peak, and the arithmetic mean value thereof may be regarded as the crystallite diameter of the particles of the present invention.

The lithium metal composite oxide powder of the present invention preferably has an average particle size in the range of 10 nm to 400 nm, more preferably in the range of 30 nm to 150 nm, and more preferably in the range of 50 nm to 100 nm. The average particle size here is an arithmetic of the diameter of the circumscribing 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 quadrangular particle image is observed, the circumscribed circle is created and the diameter of the circumscribed circle is measured. In this way, for example, for 200 particles, the diameter of each circumscribed circle is measured and the arithmetic mean value is calculated. This value is the average particle size.

In the production method of the present invention, if the cooling rate of the gas stream 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 initial stage, so that the size is finer. Moreover, it can 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, the passing flow after the introduction flow has passed through the plasma is used as the passing flow in the production method of the present invention. It can be said that it is good to provide a step of cooling with the opposing cooling gas flow.

Examples of the cooling gas flow gas include rare gases such as helium and argon, oxygen, and air, and these may be mixed and used. Similar to the introduction gas for introduction diversion described above, it is preferable to use a gas for cooling gas diversion that does not contain oxygen gas.
The temperature of the cooling gas flow may be room temperature or lower than room temperature. The flow rate of the cooling gas may be smaller than the introduced flow rate, and can be, for example, in the range of 1 to 30 L / min.

When the lithium metal composite oxide powder of the present invention composed of fine particles of the present invention is used as the positive electrode active material of the battery, for example, high-speed charge / discharge that can reduce the reaction resistance of the battery is sufficient. It is expected to have effects such as being able to show the capacity.

As described above, the lithium metal composite oxide powder of the present invention can be used as a positive electrode active material for batteries. Hereinafter, the positive electrode provided with the lithium metal composite oxide powder of the present invention is referred to as the positive electrode of the present invention, and the lithium ion secondary battery provided with the positive electrode of the present invention is 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 has a current collector and a positive electrode active material layer formed on the surface of the current collector.

As the positive electrode active material, as described above, the lithium metal composite oxide powder of the present invention is used. 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. Can be done.

Examples of the preferable range of the amount of the positive electrode active material when the entire positive electrode active material layer is 100% by mass include 30 to 100% by mass, 40 to 90% by mass, and 50 to 80% by mass. In addition, 50 to 99% by mass, 60 to 98% by mass, and 70 to 97% by mass can be exemplified.

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

The blending amount of the binder is not particularly limited, but the blending amount of the binder in the positive electrode active material layer is preferably in the range of 0.5 to 10% by mass, preferably in the range of 1 to 7% by mass. More preferably, it is particularly preferably in the range of 2 to 5% by mass. If the amount of the binder compounded is too small, the moldability of the positive electrode active material layer may decrease. Further, if the blending amount of the binder is too large, the amount of the positive electrode active material in the positive electrode active material layer is relatively reduced, which is not preferable.

The conductive auxiliary agent may be a chemically inert electron high conductor, and examples thereof include carbon black, graphite, vaporized carbon fiber (Vapor Grown Carbon Fiber), and various metal particles, which are carbonaceous fine 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.

The shape of the conductive auxiliary agent is not particularly limited, but from the viewpoint of its role, it is preferable that the average particle size of the conductive auxiliary agent is small. A preferable average particle size of the conductive auxiliary agent is 10 μm or less, and a more preferable average particle size is in the range of 0.01 to 1 μm.

The blending amount of the conductive auxiliary agent is not particularly limited, but the blending amount of the conductive auxiliary agent in the positive electrode active material layer is preferably in the range of 0.5 to 10% by mass, and is in the range of 1 to 7% by mass. It is preferably in the range of 2 to 5% by mass, and particularly preferably in the range of 2 to 5% by mass.

Known additives such as dispersants other than the conductive auxiliary agent and the binder can be adopted.

A current collector is a chemically inert electron high conductor that keeps current flowing through the electrodes during the discharge or charging of a lithium ion secondary battery. Collectors include 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. Metallic materials can be exemplified. The current collector may be coated with a known protective layer. A current collector whose surface is treated by a known method may be used as the current collector.

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

In order to produce a positive electrode, the above lithium metal composite oxide powder is mixed with other materials and a solvent as necessary, and the obtained composition for a positive electrode active material layer 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 composition for the positive electrode active material layer to the current collector, conventionally known methods such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, and a curtain coating method may be used. ..

One embodiment of the lithium ion secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolytic solution and a separator of the present invention.

The negative electrode has a current collector and a negative electrode active material layer formed on the surface of the current collector. As the current collector, the one described in the positive electrode may be appropriately adopted. The negative electrode active material layer contains a negative electrode active material and, if necessary, a conductive auxiliary agent, a binder, an additive and the like.

Examples of the negative electrode active material include carbon-based materials capable of occluding and releasing lithium, elements capable of alloying with lithium, compounds having elements capable of alloying with lithium, and polymer materials.

Examples of the carbon-based material include graphitizable carbon, graphite, cokes, graphites, vitreous carbons, calcined organic polymer compound, carbon fibers, activated carbon, and carbon blacks. Here, the calcined organic polymer compound refers to a polymer material such as phenols and furans that is calcined at an appropriate temperature and carbonized.

Specific 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, Bi can be exemplified, and Si or Sn is particularly preferable.
Specific examples of the compound having an element 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 , and NiSi ₂ . _{CaSi 2, CrSi 2, Cu 5} Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 <v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO or LiSnO can be exemplified, and in particular, SiO _x (0.3 ≦ x ≦ 1.6 or 0.5 ≦ x ≦ 1.5). Is preferable.

Among them, the negative electrode active material preferably contains a Si-based material having Si. The Si-based material is preferably composed of silicon or / or a silicon compound capable of occluding / releasing lithium ions, and for example, SiOx (0.5 ≦ x ≦ 1.5) is preferable. Although silicon has a large theoretical charge / discharge capacity, silicon has a large volume change during charge / discharge. Therefore, by using SiOx containing silicon as the negative electrode active material, it is possible to alleviate the volume change of silicon.
Further, the Si-based material preferably has a Si phase and a SiO ₂ phase. The Si phase is a phase composed of a simple substance of silicon and capable of occluding and releasing Li ions, and expands and contracts with the occlusal and release of Li ions. The SiO ₂ phase is composed of SiO ₂ and serves as a buffer phase that absorbs the expansion and contraction of the Si phase. A Si-based material in which the Si phase is coated with the SiO ₂ phase is preferable. Further, it is preferable that a plurality of finely divided Si phases are coated with the SiO ₂ phase to form particles integrally. 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 becomes large, and the negative electrode active material layer containing the Si-based material may be cracked. On the other hand, when the mass ratio exceeds 3, the amount of Li ions stored and released from the negative electrode active material is reduced, and the electric capacity per unit mass of the negative electrode of the battery is lowered.

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 the polymer material 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 adopted. Further, the Si material may be heated together with a carbon source and carbon-coated to be used as the negative electrode active material.

As the negative electrode active material, one or more of the above can be used.
As for the conductive auxiliary agent, the binder, and other additives used for the negative electrode, those described for the positive electrode may be appropriately and appropriately adopted in the same blending ratio.

The electrolytic solution contains 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 and the like 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 the chain carbonate include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, and ethyl methyl carbonate, and examples of the chain ester include propionic acid alkyl ester, malonic acid dialkyl ester, and acetate alkyl ester. 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 some or all of the chemical structure of the specific solvent is replaced with fluorine may be adopted.
These non-aqueous solvents may be used alone or in combination of two or more as the electrolytic solution.

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 the electrolytic solution, 0.5 mol / L to 1.7 mol of lithium salts such as LiClO ₄ , LiPF ₆ , LiBF ₄ , and LiCF ₃ SO ₃ are added to a non-aqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, and diethyl carbonate. An example of a solution dissolved at a concentration of about / L can be exemplified.

The separator separates the positive electrode and the negative electrode, and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. As the separator, polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, synthetic resin such as polyaramid (Aromatic polyamide), polyester, polyacrylonitrile, polysaccharides such as cellulose and amylose, and natural products such as fibroin, keratin, lignin and sverin. Examples thereof include porous bodies, non-woven fabrics, and woven fabrics using one or more electrically insulating materials such as polymers and ceramics. Further, the separator may have a multi-layer structure.

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

A separator is sandwiched between the above-mentioned positive electrode and negative electrode as needed 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 the negative electrode current collector to the positive electrode terminal and the negative electrode terminal leading to the outside using a current collector lead or the like, an electrolytic solution is added to the electrode body to form a lithium ion secondary battery. .. Further, the lithium ion secondary battery of the present invention may be 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 type, a square type, a coin type, and a laminated type can be adopted.

The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a 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 or a hybrid vehicle. When a lithium-ion secondary battery is mounted on a vehicle, a plurality of lithium-ion secondary batteries may be connected in series to form an assembled battery. In addition to vehicles, devices equipped with a lithium-ion secondary battery include various battery-powered home appliances such as personal computers and mobile communication devices, office devices, and industrial devices. Further, the lithium ion secondary battery of the present invention includes wind power generation, solar power generation, hydraulic power generation and other power system power storage devices and power smoothing devices, power supply sources for power and / or auxiliary machinery such as ships, aircraft, and aircraft. Power supply source for power and / or auxiliary equipment such as spacecraft, auxiliary power supply for vehicles that do not use electricity as power source, power supply for mobile household robots, power supply for system backup, power supply for uninterruptible power supply, It may be used as a power storage device that temporarily stores the electric power required for charging in a charging station for an electric vehicle or the like.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. It can be carried out in various forms with modifications, improvements, etc. that can be made by those skilled in the art, without departing from the gist of the present invention. In addition, some of the lithium metal composite oxide powders of the present invention contain impurities.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to these examples.

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

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

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

After the plasma was stabilized, the powder feeder was operated to introduce the mixed powder into the plasma together with the carrier gas at a supply amount of 300 mg / min. The powder released together with the passing flow after passing through the plasma was collected and used as the lithium metal composite oxide powder of Example 1.

Although the cooling gas was not used in Example 1, the cooling gas such as argon described above was used, and the passing flow after the introduction flow passed through the plasma was a cooling gas flow facing the passing flow. A cooling step may be carried out. In this case, it is considered that the cooling rate of the powder is increased and a powder composed of finer particles can be obtained.

Using the lithium metal composite oxide powder of Example 1 described above, the positive electrode and the lithium ion secondary battery of Example 1 were produced as follows.
Weigh 5 parts by mass of the lithium metal composite oxide powder of Example 1 as the positive electrode active material, 4 parts by mass of acetylene black as the conductive auxiliary agent, and 1 part by mass of polytetrafluoroethylene as the binder, and mix them in a Menou dairy pot. The composition was processed into a clay to obtain a composition for a positive electrode active material. A mesh-shaped aluminum was prepared as a current collector, and a composition for a positive electrode active material was pressure-bonded thereto to obtain a positive electrode of Example 1. All the work was performed in a glove box having a water concentration of 1 ppm or less, which was replaced with argon gas.

A lithium ion secondary battery (half cell) was prepared using the positive electrode of Example 1 prepared in the above procedure as a working electrode. The opposite electrode was a metallic lithium foil.
The working electrode and the counter electrode, and a separator (a glass filter manufactured by Hoechst Celanese and "Celgard 2400" manufactured by Celgard) intervening between the two electrodes were arranged to form an electrode body. This electrode body was housed in a battery case (CR2032 type coin battery member, manufactured by Hosen Co., Ltd.). In the battery case, a non-aqueous electrolyte solution in which LiPF ₆ was dissolved at a concentration of 1 M was injected into a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 3: 7, and the battery case was sealed to seal the battery case of Example 1. 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 at 60 L / min as the process gas. Further, using the lithium metal composite oxide powder of Example 2, the positive electrode of Example 2 and the lithium ion secondary battery of Example 2 were produced in the same manner as in Example 1.

(Comparative Example 1)
Comparative Example 1 is a method for producing a 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 the O source, Mn ₂ O ₃ was prepared as the Mn source and the O source, and Nb ₂ O ₅ was prepared as the Nb source and the O source, respectively. These 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 put into a ball mill. Then, mixing with a ball mill was carried out at about 100 rpm for 24 hours to prepare a mixture. After molding the mixture, it was heated at 1000 ° C. for 12 hours in an argon gas atmosphere and calcined to obtain a lithium metal composite oxide powder of Comparative Example 1 which was a calcined product.
The lithium metal composite oxide powder of Comparative Example 1 and acetylene black as a conductive auxiliary agent were weighed so as to have a mass ratio of 5: 2 and charged into a ball mill. Then, mixing with a ball mill was carried out 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 above-mentioned mixture of Comparative Example 1, acetylene black, and polytetrafluoroethylene as a binder were mixed in a mortar to obtain a clay-like composition for a positive electrode active material layer. In the composition for the positive electrode active material layer, the mass ratio of the lithium metal composite oxide of Comparative Example 1, acetylene black, and polytetrafluoroethylene was 5: 4: 1.
A mesh-shaped aluminum was prepared as a current collector, and a composition for a positive electrode active material layer was pressure-bonded thereto to obtain a positive electrode of Comparative Example 1. Using the positive electrode of Comparative Example 1, the lithium ion secondary battery of Comparative Example 1 was manufactured in the same manner as in Example 1.

(Comparative Example 2)
Comparative Example 2 is a method for producing a lithium metal composite oxide powder by a solid phase method as in 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. The lithium metal composite oxide powder of Comparative Example 2 was obtained in the same manner as in 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 at room temperature from 1.5 V to 4.8 V and discharged from 4.8 V to 1.5 V. A charge / discharge cycle test was performed in the order of 03C, 0.1C, 0.5C, 1C, 2C and 5C rates. The result of the evaluation test 1 is shown in FIG.
In the description here, the counter electrode is regarded as the negative electrode and the working electrode is regarded as the positive electrode. 1C means the current value required to fully charge or discharge the battery in 1 hour at a constant current.
The vertical axis (positive electrode utilization rate) in FIG. 2 represents the discharge capacity at each C rate as a percentage when the discharge capacity at 1.5 V at 0.03 C is 100% for each lithium ion secondary battery. Is.

As shown in FIG. 2, the lithium ion secondary battery of Example 2 showed a larger capacity even at a high C rate than the lithium ion secondary battery of Comparative Example 1. This result is considered to mean that the lithium ion secondary battery of Example 2 has a more efficient battery reaction at the positive electrode than 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 with a scanning electron microscope (SEM). The SEM image of the lithium metal composite oxide powder of Example 1 is shown in FIG. 3, and the 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 size of the lithium metal composite oxide powder of Example 1 and the average particle size 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.
When the average particle size of the lithium metal composite oxide powder of Example 2 was measured in the same manner, the average particle size was 43 nm, and the average particle size of the lithium metal composite oxide powder of Comparative Example 1 was similarly measured. The average particle size 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 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 much smaller than that of the physical powder. In other words, according to the production method of the present invention using the thermal plasma method, particles of a lithium metal composite oxide having a very small particle size can be obtained as compared with the conventional production method using the solid phase method.

Considering the result of the evaluation test 2 and the result of the evaluation test 1 described above, the difference in the rate characteristics between the lithium ion secondary battery of Example 2 and the lithium ion secondary battery of Comparative Example 1 is found in Examples. It is presumed that the difference in average particle size between the lithium metal composite oxide powder of 2 and the lithium metal composite oxide powder of Comparative Example 1 is largely involved.

That is, in the lithium metal composite oxide powder of Example 2 having a small average particle size, 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 are used as the positive electrode, it is considered that the battery reaction at the positive electrode is frequently performed.
From the above results, according to the production method of the present invention, fine particulate lithium metal composite oxidation useful as a positive electrode active material of a lithium ion secondary battery by synthesizing a lithium metal composite oxide by a thermal plasma method. It can be said that things can be manufactured.

(Evaluation test 3)
For the lithium ion secondary battery of Example 1 and the lithium ion secondary battery of Example 2, charging from 1.5V to 4.8V and discharging from 4.8V to 1.5V at 0.03C, respectively. The charge / discharge cycle test was repeated. Further, the lithium ion secondary battery of Comparative Example 1 was also subjected to a charge / discharge cycle test in which charging from 1.5 V to 4.8 V and discharging from 4.8 V to 1.5 V were repeated. The result of the cycle test of the lithium ion secondary battery of Example 1 is shown in FIG. 5, the result of the cycle test of the lithium ion secondary battery of Example 2 is shown in FIG. 6, and the result of the cycle test of the lithium ion secondary battery of Comparative Example 1 is shown. The result of the cycle test is 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 capacity with which the cycle elapses, as compared with the lithium ion secondary battery of Comparative Example 1. The drop is small. That is, the lithium ion secondary battery of Example 1 using the positive electrode active material by the thermal plasma method and the lithium ion secondary battery of Example 2 are the lithium ion secondary of Comparative Example 1 using the positive electrode active material by the solid phase method. Excellent cycle characteristics compared to the next battery.

Further, as shown in FIGS. 5 and 6, the lithium ion secondary battery of Example 2 has a smaller decrease in capacity with the lapse of the cycle than the lithium ion secondary battery of Example 1. That is, the lithium ion secondary battery of Example 2 is superior in cycle characteristics to 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 the synthesis of the lithium metal composite oxide powder. Therefore, it can be said that in the production method of Example 2, the amount of oxygen at the time of synthesizing the lithium metal composite oxide powder was appropriate as compared with the production method of Example 1.
Further, 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 introduction gas containing oxygen gas was used at the time of synthesizing the lithium metal composite oxide powder. It can be said that there is. Then, in the production method of Example 2 using the introduction gas containing no oxygen gas, the cycle characteristics of the lithium ion secondary battery are improved as compared with the production method of Example 1 using the introduction gas containing oxygen gas. It can also be said that the positive electrode active material to be obtained, that is, the lithium metal composite oxide powder can be produced.

In addition, according to FIGS. 5 and 6, in the lithium ion secondary battery of Example 1, the redox region of oxygen is the same size as the redox region of manganese, whereas the lithium ion secondary battery of Example 2 is used. It is considered that the redox region of manganese is larger than the redox region of oxygen in the battery. 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 redox region of oxygen with respect to the redox region of manganese. ..

That is, in the lithium ion secondary battery of Example 1, oxygen is greatly involved in the charge / discharge reaction of the positive electrode active material, that is, the lithium metal composite oxide, so that the crystal structure of the lithium metal composite oxide follows each cycle. It is considered that it was gradually damaged. 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 as the positive electrode active material is small, and as a result, the crystal structure of the lithium metal composite oxide is maintained. It is considered that it exhibits excellent cycle characteristics.

(Evaluation test 4)
The X-ray diffraction of each of the lithium metal composite oxide powders of Examples 1 and 2 was measured with 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 Example 1 and Example 2, diffraction peaks peculiar to cubic crystals that can be attributed to the space group Fm-3m were observed. From this result, according to the production method of Example 1 and the production method of Example 2, a cubic lithium metal composite oxide containing lithium element, manganese element, niobium element and oxygen element and can be attributed to the space group Fm-3m. It turns out that can be synthesized. Then, in the lithium-metal composite oxide powder of Example 1, since the diffraction peaks of the diffraction peaks and LiMn ₂ O ₄ of the lithium-metal composite oxide LiNbO ₃ not seen in the powder of Example 2 it is confirmed, implemented It can be seen that according to the production method of Example 2, by-products can be suppressed as compared with the production method of Example 1.

Taking into consideration the result of the evaluation test 4 and the result of the evaluation test 3, the amount of oxygen supplied at the time of synthesizing the lithium metal composite oxide powder is set to an appropriate amount, so that the sub-containing in the lithium metal composite oxide It can be said that the amount of organisms can be reduced, and thus the durability of the lithium ion secondary battery can be improved.
Furthermore, by using an introduction gas that does not contain oxygen gas when synthesizing the lithium metal composite oxide powder, the amount of by-products contained in the lithium metal composite oxide can be reduced, and by extension, the lithium ion secondary battery. It can be said that the durability can be improved.

Claims (8)

A lithium metal composite oxide powder having a nano-level average particle size, which has a step of introducing a lithium metal composite oxide source containing a lithium element, a niobium element, a manganese element, and an oxygen element into a plasma by an introduction flow. Manufacturing method. The production method according to claim 1, wherein the introduction stream does not contain oxygen gas. The production method according to claim 1 or 2, wherein the lithium metal composite oxide source contains a compound of at least one selected from a lithium element, a niobium element and a manganese element and an oxygen element. A lithium metal composite oxide powder containing particles containing lithium element, niobium element, manganese element, and oxygen element and having an average particle size of nano level. A step of producing a lithium metal composite oxide powder having a nano-level average particle size by the production method according to any one of claims 1 to 3.
A method for producing a positive electrode, which comprises a step of producing a positive electrode using the lithium metal composite oxide powder. A method for manufacturing a lithium ion secondary battery, which comprises a step of manufacturing a lithium ion secondary battery using the positive electrode obtained by the manufacturing method according to claim 5. A positive electrode comprising the lithium metal composite oxide powder according to claim 4. A lithium ion secondary battery comprising the positive electrode according to claim 7.