JP5718111B2 - Lithium transition metal silicate positive electrode active material and method for producing positive electrode for non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a positive electrode active material used for a positive electrode of a nonaqueous electrolyte secondary battery, including a lithium transition metal silicate.

In recent years, with the increasing mobility and functionality of electronic devices, secondary batteries, which are driving power sources, have become one of the most important components. In particular, Li-ion secondary batteries replace the conventional NiCd batteries and Ni-hydrogen batteries due to the high energy density obtained from the high voltages of the positive electrode active material and the negative electrode active material used. Occupies a position. However, currently used Li-ion secondary batteries using a combination of lithium cobalt oxide (LiCoO ₂ ) -based positive electrode active material and carbon-based negative electrode active material are the power consumption of recent high-performance, high-load electronic components. A sufficient amount cannot be supplied, and the portable power supply cannot meet the required performance.

  The theoretical electrochemical specific capacity of the positive electrode active material is generally small, manganate lithium or nickelate lithium used in addition to cobaltate lithium, or iron phosphate lithium to be studied for the next practical application Even so, the value is smaller than the theoretical specific capacity of the current carbon-based negative electrode active material. However, carbon-based negative electrode active material whose performance has been gradually improved year by year is approaching the theoretical specific capacity, and the combination of the current positive electrode and negative electrode active material systems can no longer expect a large improvement in power supply capacity. In the future, there is a limit to the demand for further enhancement of electronic equipment functionality and long-term mobile drive, as well as for use in industrial applications such as electric tools, uninterruptible power supplies, power storage devices, etc. Out.

  Under such circumstances, the application of a metal-based negative electrode active material instead of the carbon (C) -based negative electrode active material has been studied as a method capable of dramatically increasing the electric capacity from the current level. This uses germanium (Ge), tin (Sn), or silicon (Si) based materials having a theoretical specific capacity several times to 10 times that of the current carbon based negative electrode as a negative electrode active material. Since it has a specific capacity comparable to that of metallic Li, which is considered difficult to put into practical use, it is the center of investigation.

  However, since the specific capacity on the other positive electrode active material side to be combined is low, a large theoretical specific capacity of Si cannot actually be realized with a practical battery. The theoretical specific capacity per unit mass of the layered rock salt type or spinel type composite oxide, which has been studied for practical use as a positive electrode active material for the time being, is at most about 150 mAh / g. It is less than 1/2 of the specific capacity of the material, and is actually less than 1/20 of the Si specific capacity. For this reason, it is also necessary to examine material systems aimed at increasing the capacity of the positive electrode active material. As a candidate for a new positive electrode active material, studies have been started on lithium transition metal silicate (also referred to as lithium silicate transition metal) compounds, which are expected to exceed 300 mAh / g, which is twice that of conventional materials. (For example, refer to Patent Document 1 and Non-Patent Document 1).

JP 2001-266882 A

Miki Yasutomi and 4 others, "Synthesis of Li2-xM (SiO4) 1-x (PO4) x (M = Fe, Mn) cathode active material for lithium ion battery by hydrothermal reaction and its electrochemical properties", GS Yuasa Technical Report, GS Yuasa Corporation, June 26, 2009, Vol. 6, No. 1, p21-26

  However, the conventional lithium iron silicate-based positive electrode active material has a problem in that the initial discharge capacity is larger than the initial charge capacity, and the balance between the initial charge and discharge capacity is poor.

If the iron of the lithium iron silicate in the positive electrode active material is all divalent and is composed only of Li ₂ FeSiO ₄ , the initial charge capacity and the initial discharge capacity should be the same. However, since iron is oxidized in the manufacturing process and LiFeSiO ₄ which is a trivalent iron compound is included in the positive electrode active material, lithium ions are not discharged at the time of discharge even at sites where lithium was not included before charging. It is considered that the initial discharge capacity becomes larger than the initial charge capacity.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for producing a lithium transition metal silicate positive electrode active material in which the oxidation of a transition metal element is suppressed. And

  The inventors of the present invention, as a result of the study, when firing the fine particle mixture that is a precursor of the positive electrode active material material, firing in the green compact state, compared with the case of firing in the powder state The present inventors have found that a lithium transition metal silicate-based positive electrode active material in which oxidation of the fine particle mixture is suppressed and oxidation is suppressed can be obtained.

That is, the present invention provides the following inventions.
(1) Supplying a lithium source, a transition metal source and a silicon source together with a combustion-supporting gas and a combustible gas into a flame to synthesize a fine particle mixture (a), and mixing a carbon source into the fine particle mixture A step (b), a step (c) of producing a green compact by filling and pressing the fine particle mixture mixed with the carbon source into a mold, and firing the green compact in an inert gas filling atmosphere. A process for producing a lithium transition metal silicate positive electrode active material comprising a step (d) and a step (e) of pulverizing the green compact.
( 2 ) In the step (a), the mixed solution containing the lithium source, the transition metal source and the silicon source is supplied into the flame in the form of mist droplets ( 1 ) The manufacturing method of positive electrode active material material as described in any one of.
( 3 ) In the said process (a), the temperature of the said flame is 1000-3000 degreeC, The manufacturing method of the positive electrode active material material as described in ( 1) or (2) characterized by the above-mentioned.
( 4 ) The positive electrode according to any one of (1) to ( 3 ), wherein in the step (a), the combustible gas is a hydrocarbon-based gas, and the combustion-supporting gas is air. A method for producing an active material.
( 5 ) A step (a) of synthesizing a fine particle mixture by heating a mist-like droplet of a mixed solution containing a lithium source, a transition metal source and a silicon source, and a step of mixing a carbon source into the fine particle mixture (b) ), And a step (c) of producing a green compact by filling and pressing the fine particle mixture mixed with the carbon source into a mold, and a step (d) of firing the green compact in an inert gas filled atmosphere (d) And a step (e) of pulverizing the green compact, and a method for producing a lithium transition metal silicate-based positive electrode active material.
( 6 ) The lithium compound of the lithium source is lithium chloride, lithium hydroxide, lithium acetate, lithium nitrate, lithium bromide, lithium phosphate, lithium sulfate, lithium oxalate, lithium naphthenate, lithium ethoxide, lithium oxide, Any one or more of lithium peroxide, and the transition metal compound of the transition metal source is selected from the group consisting of Fe, Mn, Ti, Cr, V, Ni, Co, Cu, Zn, Zr, Mo, W Chloride, oxalate, acetate, sulfate, nitrate, hydroxide, ethylhexane salt, naphthenate, hexate salt, cyclopentadienyl compound, alkoxide, organic acid of at least one selected transition metal Metal salts (stearic acid, dimethyldithiocarbamic acid, acetylacetonate, oleic acid, linoleic acid, linolenic acid ), Any one of oxides, and the silicon compound of the silicon source is silicon tetrachloride, octamethylcyclotetrasiloxane (OMCTS), silicon dioxide, silicon monoxide or a hydrate of these silicon oxides, condensation Silicic acid, tetraethylorthosilicate (tetraethoxysilane, TEOS), tetramethylorthosilicate (tetramethoxysilane, TMOS), methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), hexamethyldisiloxane (HMDSO), (1) to (5), which are any one or more of tetramethyldisiloxane (TMDSO), tetramethylcyclotetrasiloxane (TMCTS), octamethyltrisiloxane (OMTSO), and tetra-n-butoxysilane. ) Process for producing a positive electrode active material according to any Re.
( 7 ) The method for producing a positive electrode active material according to any one of (1) to ( 6 ), wherein the carbon source is polyvinyl alcohol.
( 8 ) In the step (d), the calcination is performed in a gas atmosphere filled with an inert gas at 300 to 900 ° C. for 0.5 to 10 hours, wherein (1) to ( 7 ) The manufacturing method of the positive electrode active material material in any one.
( 9 ) A step of producing a slurry containing the positive electrode active material produced by the method for producing a positive electrode active material according to any one of (1) to ( 8 ), and applying and firing the slurry onto a current collector And a process for producing a positive electrode for a non-aqueous electrolyte secondary battery.
(10) the slurry, (1) second-order either to the positive electrode active material 0.5~20μm size was granulated by adding the produced positive electrode active material by the method for producing according to (8) The manufacturing method of the positive electrode for nonaqueous electrolyte secondary batteries as described in ( 9 ) characterized by containing particle | grains.

  The present invention can provide a method for producing a lithium transition metal silicate-based positive electrode active material in which the oxidation of a transition metal element is suppressed.

Schematic of the fine particle manufacturing apparatus used for the spray combustion method for producing the fine particle mixture according to the present invention. The schematic sectional drawing of the nonaqueous electrolyte secondary battery using the positive electrode active material which concerns on this invention. The XRD measurement result of the fine particle mixture and positive electrode active material which concern on an Example and a comparative example. (A) Transmission electron microscope (TEM) image of the fine particle mixture before firing in Example 1, (b) TEM image of the positive electrode active material after firing in Example 1, (c) After firing in Comparative Example 1 TEM image of positive electrode active material. (A) HAADF-STEM image of the positive electrode active material after firing in Example 1, (b) EDS map of iron atoms at the same observation location, (c) EDS map of silicon atoms at the same observation location, (d ) EDS map of oxygen atoms at the same observation location. (A) HAADF-STEM image of the positive electrode active material after firing in Comparative Example 1, (b) EDS map of iron atom at the same observation location, (c) EDS map of silicon atom at the same observation location, (d ) EDS map of oxygen atoms at the same observation location. (A) The charge / discharge curve of the 1st cycle of the nonaqueous electrolyte secondary battery which concerns on an Example and a comparative example, (b) The charge / discharge curve of the 2nd cycle similarly.

  Hereinafter, preferred embodiments of the fine particle mixture and the positive electrode active material according to the present invention will be described. The present invention is not limited to these embodiments.

  The positive electrode active material of the present invention is obtained and provided as a powder material. Furthermore, the positive electrode active material is a water-based solvent or an organic solvent in which a predetermined amount of a dispersant, a thickener, a conductive material, or the like is added in a state as it is or in a state where the particles are granulated to increase the size of the secondary particles. Also provided as a solvent slurry. Moreover, it is provided also as an electrode form which apply | coated these slurries on the electrical power collector base material, and formed the positive electrode active material material in the film form. And the secondary battery in this invention is assembled and provided as a secondary battery with other structural materials, such as a well-known negative electrode, a separator, and electrolyte solution, using the positive electrode for secondary batteries of this invention.

  The positive electrode active material according to the present invention is synthesized by synthesizing a fine particle mixture which is an active material precursor by supplying constituent raw materials to the same reaction system, and heat-treating the mixture.

(Production method of fine particle mixture by spray combustion method)
The spray combustion method is a method of supplying a constituent raw material into a flame and reacting the constituent raw materials to obtain a target substance by a method of supplying a raw material gas such as chloride or a method of supplying a raw material liquid through a vaporizer. . As a spray combustion method, VAD (Vapor-phase Axial Deposition) method etc. are mentioned as a suitable example. The temperature of these flames varies depending on the mixing ratio of the combustible gas and the combustion-supporting gas and the addition ratio of the constituent raw materials, but is usually between 1000 and 3000 ° C., particularly about 1500 to 2500 ° C. Is preferred.

  The flame hydrolysis method is a method in which constituent raw materials are hydrolyzed in a flame. In the flame hydrolysis method, an oxyhydrogen flame is generally used as a flame. The constituent material of the positive electrode active material and the flame raw material (oxygen gas and hydrogen gas) are simultaneously supplied from the nozzle under the flame supplied with hydrogen gas and oxygen gas to synthesize the target substance. In the flame hydrolysis method, nanoscale ultrafine, mainly amorphous particles of the target substance can be obtained in an inert gas-filled atmosphere.

  The thermal oxidation method is a method in which constituent raw materials are thermally oxidized in a flame. In the thermal oxidation method, a hydrocarbon flame is generally used as a flame, and a constituent material and a flame material (for example, propane gas and oxygen gas) are simultaneously supplied from a nozzle under a hydrocarbon gas (for example, propane gas) and an oxygen gas supply flame. Synthesize target substance while supplying.

  The constituent raw materials for obtaining the fine particle mixture of the present invention are a lithium source, a transition metal source, and a silicon source. For example, a solution such as lithium naphthenate as the lithium source, iron octylate as the transition metal source, and octamethylcyclotetrasiloxane (OMCTS) as the silicon source is used. When the raw material is solid, it is supplied as a powder, dispersed in a liquid, or dissolved in a solvent to form a solution, which is supplied to a flame through a vaporizer. In the case where the raw material is a solution, in addition to passing through a vaporizer, vaporization can be performed by increasing the vapor pressure by heating or pressure reduction and bubbling before the supply nozzle.

  Examples of lithium sources include lithium inorganic acid salts such as lithium chloride, lithium hydroxide, lithium carbonate, lithium nitrate, lithium bromide, lithium phosphate, and lithium sulfate, and lithium organic acids such as lithium oxalate, lithium acetate, and lithium naphthenate. A salt, a lithium alkoxide such as lithium ethoxide, an organic lithium compound such as a β-diketonate compound of lithium, lithium oxide, lithium peroxide, or the like can be used. Naphthenic acid is a mixture of different carboxylic acids mainly mixed with a plurality of acidic substances in petroleum, and the main component is a carboxylic acid compound of cyclopentane and cyclohexane.

Transition metal sources include chlorides of various transition metals such as ferric chloride, manganese chloride, titanium tetrachloride, and vanadium chloride, transition metal oxalates such as iron oxalate and manganese oxalate, and transition metals such as manganese acetate. Acetate, transition metal sulfate such as ferrous sulfate and manganese sulfate, transition metal nitrate such as manganese nitrate, transition metal hydroxide such as manganese oxyhydroxide and nickel hydroxide, 2-ethylhexanoic acid Transition metal ethyl hexanoate (also called octylate), tetra (2-ethylhexyl) titanate, iron naphthenate, manganese naphthenate, chromium naphthenate, naphthenic acid Naphthenic acid transition metal salts such as zinc, zirconium naphthenate and cobalt naphthenate, and heptate such as manganese Transition metal salts of Soeto, cyclopentadienyl compounds of a transition metal, titanium tetraisopropoxide (TTIP), can be used a transition metal alkoxide such as titanium alkoxide. Further, organic metal salts of transition metals such as stearic acid, dimethyldithiocarbamic acid, acetylacetonate, oleic acid, linoleic acid, and linolenic acid, and oxides of various transition metals such as iron oxide and manganese oxide are also used depending on conditions.
As will be described later, when two or more transition metals are used in the lithium transition metal silicate compound, two or more transition metal raw materials are supplied into the flame.

  Silicon sources include silicon tetrachloride, octamethylcyclotetrasiloxane (OMCTS), silicon dioxide, silicon monoxide or hydrates of these silicon oxides, condensed silicic acid such as orthosilicic acid, metasilicic acid, metadisilicic acid, tetraethyl Orthosilicate (tetraethoxysilane, TEOS), tetramethylorthosilicate (tetramethoxysilane, TMOS), methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), hexamethyldisiloxane (HMDSO), tetramethyldisiloxane (TMDSO), tetramethylcyclotetrasiloxane (TMCTS), octamethyltrisiloxane (OMTSO), tetra-n-butoxysilane, and the like can be used.

When a part of the silicate of the lithium transition metal silicate compound is replaced with another anion, an oxide of transition metal, a raw material of phosphoric acid, a raw material of boric acid is added as an anion source. For example, titanium oxide, subtitanium Metal titanates such as iron oxide and manganese titanate, titanates such as zinc titanate, magnesium titanate and barium titanate, vanadium oxide, ammonium metavanadate, chromium oxide, chromate and dichromate , Manganese oxide, permanganate and manganate, cobaltate, zirconium oxide, zirconate, molybdenum oxide, molybdate, tungsten oxide, tungstate, phosphoric acid such as orthophosphoric acid and metaphosphoric acid, pyrophosphoric acid , Hydrogen phosphates such as diammonium hydrogen phosphate and ammonium dihydrogen phosphate Various phosphates or pyrophosphates such as ammonium salts, ammonium phosphates and sodium phosphates, phosphates of introduced transition metals such as ferrous phosphate, boric acid and diboron trioxide, sodium metaborate and tetraborates Various borates such as sodium acid and borax can be used depending on the desired anion source and synthesis conditions.

  These raw materials are supplied to the same reaction system together with the flame raw material to synthesize a fine particle mixture. The produced particulate mixture can be recovered from the exhaust gas with a filter. It can also be generated around the core rod as follows. A silica or silicon-based core rod (also called a seed rod) is installed in the reactor, and a lithium source, transition metal source, and silicon source are supplied together with the flame raw material into the oxyhydrogen flame or propane flame that is blown onto the core rod. When hydrolyzed or oxidized, nano-order fine particles are mainly generated and attached to the surface of the core rod. These generated fine particles are collected and, if necessary, filtered or sieved to remove impurities and coarse aggregates. The fine particle mixture thus obtained is composed of fine particles mainly having an amorphous nano-scale particle size and amorphous.

  In the spray combustion method, which is a method for producing a fine particle mixture according to the present invention, the fine particle mixture that can be produced is amorphous and has a small particle size. Furthermore, in the spray combustion method, a large amount of synthesis is possible in a short time as compared with the conventional hydrothermal synthesis method and solid phase reaction method, and a homogeneous fine particle mixture can be obtained at low cost.

(Characteristics of fine particle mixture by spray combustion method)
The fine particle mixture is mainly composed of amorphous fine particles of lithium, transition metal, silicon oxide, or lithium transition metal silicate, but in many cases, a crystalline oxide of transition metal is also mixed. Furthermore, a part of the crystalline component of the lithium transition metal silicate compound is also included.

  When these fine particle mixtures are measured by powder method X-ray diffraction in the range of 2θ = 10 to 60 °, the diffraction peak is small and the diffraction angle is wide. These are derived from the crystal planes of each lithium transition metal silicate compound, which are microcrystals with small crystallites, or polycrystalline microparticles with small single crystals, and microcrystalline forms with amorphous components around these microparticles. It seems to show diffraction. Note that the peak position may be shifted by about ± 0.1 ° to ± 0.2 ° due to crystal distortion and measurement error.

The lithium transition metal silicate fine particles contained in the obtained fine particle mixture contain a lithium transition metal silicate compound represented by Li ₂ MSiO ₄ . M is at least one transition metal selected from the group consisting of Fe, Mn, Ti, Cr, V, Ni, Co, Cu, Zn, Zr, Mo, and W. Further, in the spray combustion method of the present application, carbon burns in the flame, so the obtained fine particle mixture does not contain carbon. Even if a carbon component is mixed, the amount is very small and is not so large as to be a conductive aid when used for the positive electrode.

(Production method of fine particle mixture by spray pyrolysis)
The fine particle mixture which is a precursor of the active material can also be produced by a spray pyrolysis method. The spray pyrolysis method is a mixture solution containing a lithium source, a transition metal source, and a silicon source in the form of mist droplets that are circulated in a reaction vessel heated to about 500 to 900 ° C. And a fine particle mixture is obtained. For heating in the reaction vessel, an electric furnace or a flame furnace may be used.

  The spray combustion method described above is the same as the types of usable lithium source, transition metal source, and silicon source, and the formation of mist-like droplets. However, in the spray combustion method, the reaction proceeds at about 2000 ° C. in the flame, but in the spray pyrolysis method, the reaction proceeds at a lower temperature in the reaction vessel. Further, the carrier gas of the mist-like droplets is air or an inert gas in the spray pyrolysis method, whereas the spray combustion method includes a combustible gas and a combustion-supporting gas. The spray pyrolysis method is different in that the reaction time is longer than that of the spray combustion method because the spray pyrolysis method is circulated in the reaction vessel.

  In the spray pyrolysis method, as in the spray combustion method, a mixture of fine particles mainly composed of amorphous fine particles of lithium, transition metal, silicon oxide and lithium transition metal silicate, which are precursors of the active material, is used. can get.

(Production method of fine particle mixture by hydrothermal synthesis method and solid phase reaction method)
The fine particle mixture can also be produced by a hydrothermal synthesis method or a solid phase reaction method. The hydrothermal synthesis method is a method in which a raw material solution is placed in a sealed container and a compound is synthesized in the presence of high-temperature and high-pressure water. The solid-phase reaction method is a method in which powder raw materials are mixed and then heat-treated. In this method, a compound is synthesized directly from a solid phase. In the present invention, the fine particle mixture produced by the solid phase reaction method is not a simple mixture of a lithium source, a transition metal source, and a silicon source, but a compound powder that has been subjected to heat treatment and proceeded with the solid phase reaction. means.

(Manufacture of positive electrode active material)
By heat-treating the fine particle mixture, the amorphous compound or oxide-type mixture contained in the fine particle mixture is changed into a lithium transition metal silicate-based compound mainly by the heat treatment, and the lithium transition metal silicate positive electrode An active material is obtained.

  First, in order to increase the conductivity of the product after the heat treatment, a polyhydric alcohol such as polyvinyl alcohol, a saccharide such as sucrose, and a carbon source such as carbon black are added to and mixed with the fine particle mixture. In this case, polyvinyl alcohol, which is a kind of polyhydric alcohol, is particularly preferable because it plays a role as a carbon source and also serves as a binder for molding in a compacting process described later, and can reduce an iron component during firing. .

  Thereafter, the fine particle mixture after mixing the carbon source is filled in a mold and pressed to produce a green compact. As this mold, a normal mold used for forming a green compact can be used. For example, a mold capable of molding a green compact of a tablet type or a pellet type is used. Moreover, it is preferable that the pressurization conditions at the time of forming a green compact are pressurization for 5 to 120 seconds with a pressing force of 1 to 10 MPa.

  Thereafter, the fine particle mixture and the green compact of the carbon source are fired in an atmosphere filled with an inert gas. Nitrogen gas, argon gas, neon gas, helium gas, carbon dioxide gas, etc. can be used as the inert gas. Firing products having desired crystallinity and particle size can be appropriately obtained by combining the firing conditions of a temperature of 300 to 900 ° C. and a treatment time of 0.5 to 10 hours. Excessive heat load due to high temperature or long-time heat treatment can generate a coarse single crystal and should be avoided. Under heating conditions to obtain a desired crystalline or microcrystalline lithium transition metal silicate compound, Heat treatment conditions that can suppress the crystallite size as small as possible are desirable.

  Thereafter, the fired green compact is applied to a mortar, ball mill, or other pulverizing means to obtain fine particles, and the positive electrode active material of the present invention that can suffice with a Li ion intercalation host is obtained.

(Characteristics of positive electrode active material according to the present invention)
Since the positive electrode active material according to the present invention performs the firing step in a green compact state, the oxidation of the transition metal element can be suppressed. Therefore, a positive electrode active material having a target composition can be obtained in the present invention, and a non-aqueous electrolyte secondary battery using the positive electrode active material according to the present invention is a trivalent lithium transition metal during the first charge / discharge. Since the side reaction in which the silicate reacts with lithium ions hardly occurs, the initial charge capacity and the initial discharge capacity are close.

  Since the positive electrode active material according to the present invention has less oxidized positive electrode active material than the conventional positive electrode active material, the capacity increases when used in a non-aqueous electrolyte secondary battery.

  Further, the structure of the oxidized positive electrode active material is fragile because lithium ions are inserted at the first discharge into a site where there is no lithium immediately after synthesis. Since the positive electrode active material according to the present invention has less oxidized positive electrode active material than the conventional positive electrode active material, the cycle life becomes longer when used in a non-aqueous electrolyte secondary battery.

  By suppressing the oxidation in the present invention, by making a green compact, the effective surface area is small during firing and before and after firing, and the surface area where each fine particle comes into contact with the atmosphere can be reduced, thereby suppressing oxidation. It is thought that you can.

  Most of the crystallized lithium transition metal silicate compounds contained in the positive electrode active material of the present invention are fine crystals, but there are also “microcrystalline” states containing an amorphous component in part. For example, a state in which fine particles composed of a plurality of crystallites are covered with an amorphous component, or a state in which fine crystals are present in an amorphous component matrix, or an amorphous state between and around the fine particles The state in which a component exists.

Further, when the particle size distribution of the positive electrode active material according to the present invention is measured by observation with a transmission electron microscope (TEM) and the particle size distribution is obtained, it is in the range of 10 to 200 nm and the average value is in the range of 25 to 100 nm. To do. These particles are composed of a plurality of crystallites. The particle size distribution is more preferably in the range of 10 to 150 nm, and the average value is more preferably in the range of 25 to 80 nm. It should be noted that the presence of the particle size distribution in the range of 10 to 200 nm does not require the obtained particle size distribution to cover the entire range of 10 to 200 nm, the lower limit of the obtained particle size distribution is 10 nm or more, and the upper limit is 200 nm or less. It means that there is. That is, the obtained particle size distribution may be 10 to 100 nm or 50 to 150 nm.
Since the positive electrode active material according to the present invention has a small particle size, the conductive path of Li ions or electrons in single crystals or polycrystalline particles is short, and ionic conductivity and electronic conductivity are excellent. The reaction barrier can be lowered.

  The positive electrode active material according to the present invention has a substantially spherical shape. Although a partially rounded portion is also recognized, the whole has a substantially spherical shape.

  In the positive electrode active material according to the present invention, it is preferable that the lithium transition metal silicate fine particles are at least partially coated with carbon or at least partially supported with carbon. The carbon coat is to coat the surface of particles with carbon, and the carbon support is to contain carbon in the particles. The carbon coating or carbon support increases the electrical conductivity of the material, provides a conductive path to the lithium transition metal silicate fine particles, and improves the electrode characteristics when used for the positive electrode.

The characteristics of the obtained positive electrode active material vary depending on the transition metal used and its type, such as charge / discharge capacity. For example, when an Fe raw material is used as a transition metal source, synthesis is easy at a low cost, but the capacity is limited to the conventional level with only one kind of Fe. In the case of a Mn raw material, the synthesis is easy at a low cost, but lithium manganese silicate has a defect that its crystal structure tends to collapse due to Li intercalation and deintercalation, and tends to have a short charge / discharge cycle life. Therefore, the use two elements of transition metals like lithium iron manganese silicate using two raw materials of Fe and _{Mn (Li 2 Fe 1-x} Mn x SiO 4), wherein the low volume and the crystal structure collapse problem solving To do. On the other hand, Fe contributes to stabilization of the crystal structure. The same can be said for Ti, Cr, V, Ni, Co, Cu, Zn, Al, Ge, Zr, Mo, and W other than Fe and Mn.

On the other hand, (SiO ₄ ) _n silicate of an anion or polyanion is the same, and a part of (SiO ₄ ) _n can be substituted with another anion. For example, the transition metal acid is titanic acid (TiO ₄ ), chromic acid (CrO ₄ ), vanadic acid (VO ₄ , V ₂ O ₇ ), zirconic acid (ZrO ₄ ), molybdic acid (MoO ₄ , Mo ₇ O ₂₄ ), tungstic acid (WO ₄ ), etc., or substitution with phosphoric acid (PO ₄ ) or boric acid (BO ₃ ). By substituting a part of the polysilicate ion with these anion species, it contributes to the suppression and stabilization of the crystal structure change due to repeated desorption and recovery of Li ions, and the cycle life is improved. In addition, these anionic species are less likely to release oxygen even at high temperatures, and can be used safely without causing ignition.

(Method for producing positive electrode for non-aqueous electrolyte secondary battery)
In order to form a positive electrode using a positive electrode active material obtained by pulverizing a green compact obtained by heat treatment of a fine particle mixture, it is necessary to form a positive electrode active material material coated or supported with carbon. Depending on the case, conductive materials such as carbon black (especially acetylene black) are added, and binders such as polytetrafluoroethylene, polyvinylidene fluoride and polyimide, or dispersants such as butadiene rubber, or carboxymethylcellulose and cellulose derivatives, etc. A mixture of the above thickener added in an aqueous solvent or organic solvent matrix and applied as a slurry is coated on one or both sides of a current collector such as an aluminum alloy foil containing 95% by weight or more of aluminum. Calcinate and evaporate the solvent. Thereby, the positive electrode of the present invention is obtained.

  At this time, in order to improve the coating property of the slurry, the adhesion between the current collector and the active material, and the current collection, granulation is performed by a spray dry method using the positive electrode active material and a carbon source, and firing. The secondary particles thus obtained can be used in the form of a slurry instead of the active material. The agglomerated secondary particles become large agglomerates of about 0.5 to 20 μm, but this greatly improves the slurry coatability and further improves the characteristics and life of the battery electrode. As the slurry used for the spray drying method, either an aqueous solvent or a non-aqueous solvent can be used.

  Furthermore, in a positive electrode in which a slurry containing the positive electrode active material is applied and formed on a current collector such as an aluminum alloy foil, the current collector surface roughness of the active material layer forming surface is Japanese Industrial Standard (JIS B 0601-1994). It is desirable that the ten-point average roughness Rz defined in (1) is 0.5 μm or more. The adhesiveness between the formed active material layer and the current collector is excellent, the electron conductivity accompanying the insertion and release of Li ions and the current collecting power to the current collector are increased, and the cycle life of charge / discharge is improved.

  Further, at the interface between the current collector and the active material layer formed on the current collector, when a mixed state in which the main component of the current collector diffuses at least into the active material layer is shown, the current collector and the active material The interfacial bondability is improved and resistance to changes in volume and crystal structure in the charge / discharge cycle is increased, so that the cycle life is improved. It is even better when the current collector surface roughness condition is also satisfied. According to sufficient firing conditions that can volatilize the solvent, the current collector component diffuses into the active material layer, resulting in an interfacial state having mutual components, excellent adhesion, and volume change due to the entry and exit of Li ions even after repeated charge and discharge Withstands and improves cycle life.

(Nonaqueous electrolyte secondary battery)
In order to obtain a high-capacity secondary battery using the positive electrode of the present invention, various materials such as a negative electrode, an electrolytic solution, a separator, and a battery case using a conventionally known negative electrode active material can be used without particular limitation. it can. In the nonaqueous electrolyte secondary battery of the present invention, a separator is disposed between the positive electrode and the negative electrode as described above to form a battery structure. After winding or folding such a battery structure into a cylindrical or rectangular battery case, an electrolyte is injected to complete a lithium ion secondary battery.

  Specifically, as shown in FIG. 2, the nonaqueous electrolyte secondary battery 11 of the present invention includes a positive electrode 13 and a negative electrode 15 that are stacked in the order of separator-negative electrode-separator-positive electrode via a separator 17. Then, the positive electrode 13 is wound so as to be on the inner side to constitute an electrode plate group, which is inserted into the battery can 21. The positive electrode 13 is connected to the positive electrode terminal 27 via the positive electrode lead 23, and the negative electrode 15 is connected to the battery can 21 via the negative electrode lead 25, and the chemical energy generated inside the nonaqueous electrolyte secondary battery 11 is externally used as electric energy. To be able to take out. Next, after filling the battery can 21 with the non-aqueous electrolyte 19, the upper end (opening portion) of the battery can 21 is composed of a circular lid plate and a positive electrode terminal 27 on the upper portion thereof, and a sealing body incorporating a safety valve mechanism therein. 29 can be attached via an annular insulating gasket to produce the nonaqueous electrolyte secondary battery 11 of the present invention.

  Although the secondary battery using the positive electrode according to the present invention has a high capacity and good electrode characteristics, a non-aqueous solvent containing fluorine is used for the electrolytic solution using the non-aqueous solvent constituting the secondary battery. If added or added, the capacity is unlikely to decrease even after repeated charging and discharging, resulting in a long life. For example, in particular, when using a negative electrode containing a silicon-based high-capacity negative electrode active material, in order to suppress large expansion and contraction due to Li ion doping / dedoping, the electrolyte contains fluorine, or fluorine It is desirable to use an electrolytic solution containing a nonaqueous solvent having as a substituent. Since the fluorine-containing solvent relaxes the volume expansion of the silicon-based film due to alloying with Li ions during charging, particularly during the first charging process, it is possible to suppress a decrease in capacity due to charging and discharging. As the fluorine-containing non-aqueous solvent, fluorinated ethylene carbonate, fluorinated chain carbonate, or the like can be used. Mono-tetra-fluoroethylene carbonate (4-fluoro-1,3-dioxolan-2-one, FEC) is used for fluorinated ethylene carbonate, and methyl 2,2,2-trifluoroethyl carbonate is used for fluorinated chain carbonate. , Ethyl 2,2,2-trifluoroethyl carbonate, etc., and these can be used alone or in combination with a plurality of electrolytes. Since the fluorine group is easy to bond with silicon and is strong, it is considered that the film can be stabilized and contribute to suppression of expansion even when it is expanded by charging alloy with Li ion.

(Effect of the present invention)
Since the positive electrode active material according to the present invention performs the firing step in a green compact state, the oxidation of the transition metal element can be suppressed. Therefore, in the nonaqueous electrolyte secondary battery according to the present invention, a side reaction in which trivalent lithium transition metal silicate reacts with lithium ions hardly occurs at the time of initial discharge, so that the initial charge capacity and the initial discharge capacity are close to each other.

  Since the positive electrode active material according to the present invention has less oxidized positive electrode active material than the conventional positive electrode active material, when used in a non-aqueous electrolyte secondary battery, the capacity increases and the cycle life is reduced. become longer.

  The positive electrode active material for a secondary battery according to the present invention has unprecedented nanoscale small crystals and primary particles, and further, since the crystallinity is low, the distance to which Li ions and electrons move is small. Since the ionic conductivity and the electronic conductivity are excellent, a high capacity inherently possessed by the lithium transition metal silicate compound can be obtained during charging and discharging.

  In addition, when the positive electrode active material according to the present invention is used, Li ion diffusibility and electronic conductivity of the particles of the active material itself are improved, so that Li ions can be easily deintercalated and intercalated. I found out that I can. The present invention serves as a basis for realizing the high charge / discharge capacity inherent in lithium transition metal silicate compounds in the future.

  In addition, the positive electrode active material according to the present invention has a larger half-width of the diffraction peak by X-ray diffraction measurement and a smaller crystallite size or smaller particle size and particle size than conventional materials. , Li ion or electron conduction path in single crystal or polycrystalline particles is short, and ion conductivity and electron conductivity are excellent.

  In addition, coating and carrying a conductive additive or conductive carbon improves the electrical conductivity and macro current collection up to the current collector through the conductive path network, and it can be used even in low-temperature environments such as normal room temperature. A lithium transition metal silicate compound that can be discharged can be provided.

  In addition, the positive electrode active material according to the present invention is also characterized by being in a microcrystalline state having a crystal in which an amorphous component exists in a part of the periphery, as compared with a conventional positive electrode active material. These can not be obtained by the production method by a solid phase reaction method that has been generally used in the past, but mainly by a method in which a raw material that is a material source of a positive electrode active material is supplied to the same reaction system and reacted in a flame, etc. It can be obtained by firing after generating an amorphous active material precursor. According to such a production method, a homogeneous positive electrode active material such as a substantially spherical fine particle can be obtained by finely pulverizing the fine particle mixture after firing. This makes it possible to granulate secondary particles of a size that can be easily coated on the current collector, and has excellent adhesion between the current collector and the active material. An active material layer can be obtained.

  When the component of the lithium transition metal silicate compound contained in the positive electrode active material of the present invention contains a plurality of transition metals capable of obtaining a two-electron reaction in the charge / discharge reaction, a higher capacity can be obtained. In addition, since it is a silicate compound that does not release oxygen, it does not ignite and burn even in a high-temperature environment, and a safe secondary battery can be provided.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples.
In the following examples, the lithium iron silicate compound was synthesized. However, when other transition metals are used or when other anions are added to the composition material, they can be synthesized and provided in the same manner.

(1-1) Example 1
(Preparation of fine particle mixture)
A production apparatus for producing a fine particle mixture by a spray combustion method is shown in FIG. The reaction vessel of the apparatus shown in FIG. 1 has a fine particle synthesis nozzle 3 disposed in the vessel, and propane gas, air, and a raw material solution are supplied into a flame generated from the nozzle 3. On the other hand, it has an exhaust pipe for exhausting the generated fine particles and reaction products, and the fine particle mixture 7 in the exhaust is recovered by the fine particle recovery filter 5. The types of raw materials supplied to the nozzle and the supply conditions were as follows. The raw material solution was supplied into the flame using a two-fluid nozzle so that the size of the droplets was 20 μm. The flame temperature was about 2000 ° C.
Combustible gas: Propane (C ₃ H ₈ ): 1 dm ³ / min,
Combustion gas: Air: 5 dm ³ / min,
Lithium source: lithium naphthenate (4M solution): 0.025 dm ³ / min
Iron source: C ₁₆ H ₃₀ FeO ₄ (2-ethylhexane iron (II), iron octylate) (1M solution): 0.1 dm ³ / min
Silicon source: Octamethylcyclotetrasiloxane: 0.1 dm ³ / min,

The method for producing the fine particle mixture by the spray combustion method is as follows. First, a predetermined amount of N ₂ gas was supplied, and the reaction vessel was filled with an inert gas atmosphere. Under such conditions, a solution in which each of a lithium source, an iron source, and a silicon source was mixed was made into 20 μm droplets through an atomizer and supplied to a flame together with propane gas and air. A fine particle mixture such as fine particles of lithium oxide, iron oxide, silicon oxide and the like produced in the flame and fine particles of lithium iron silicate compound was collected by a fine particle collecting filter. The obtained fine particle mixture is the fine particle mixture a.

(Manufacture of positive electrode active material)
Next, polyvinyl alcohol was added to the fine particle mixture so that the polyvinyl alcohol would be 10 wt% of the total, and mixed. Thereafter, the fine particle mixture was filled in a cylindrical mold having an inner diameter of 10 mm, and a pressure of 10 MPa was applied for 30 seconds to form a disk-shaped green compact having a diameter of 10 mm and a thickness of 6 mm.
Thereafter, the green compact was placed in a furnace filled with N ₂ gas, and heat treatment was performed at 650 ° C. for 4 hours to perform firing. Simultaneously with the firing, carbon coating or carbon loading was performed. The green compact was pulverized to obtain a positive electrode active material A.

(2-1) Comparative Example 1
(Manufacture of positive electrode active material)
Polyvinyl alcohol was added to the fine particle mixture a obtained in Example 1 and mixed so that the polyvinyl alcohol would be 10 wt% of the total.
Thereafter, without further form a green compact, placed particulate mixture in the furnace of the N ₂ gas filling, subjected to heat treatment for 4 hours at 650 ° C., was fired. Simultaneously with the firing, carbon coating or carbon loading was performed. The fine particle mixture after firing was pulverized to obtain a positive electrode active material B.

(3) Measurement observation confirmation of sample (3-1) Powder X-ray diffraction measurement Powder X-ray diffraction measurement (2θ = 10 to 60) of the fine particle mixture of Example 1 and Comparative Example 1 and the respective positive electrode active material after firing. °). The X-ray diffraction measurement results are shown in FIG.

  As shown in FIG. 3A, it can be seen that the fine particle mixture before firing, which is the precursor of the active material, has a wide peak and is in a microcrystalline form. Furthermore, as shown in FIGS. 3B and 3C, the fired positive electrode active material had a number of peaks, and these peaks were peaks derived from the crystal structure of lithium iron silicate. By firing the fine particle mixture, the crystal structure of lithium iron silicate has grown, but even after firing, the peak is wider than the conventional material, and it can be seen that the crystal grains are small.

(3-2) Observation by Transmission Electron Microscope (TEM) Similarly, the obtained positive electrode active material was observed by TEM. The result of TEM image observation is shown in FIG.
As shown in FIG. 4A, the fine particle mixture before firing was substantially spherical, and particles having a primary particle diameter of 10 to 50 nm were observed. Moreover, as shown in FIG.4 (b), the primary particle diameter of the positive electrode active material which concerns on an Example is 10-50 nm, and amorphous carbon is coated around the lithium iron silicate particle. Similarly, in FIG. 4C, carbon is coated around the positive electrode active material lithium iron silicate particles according to the comparative example.

(3-3) Composition analysis by EDS Observation of the particle shape and composition analysis of the positive electrode active material after firing in Example 1 were performed using a scanning transmission electron microscope (JEM 3100FEF, HAADF-STEM). (High-Angle-Annular-Dark-Field-Scanning-Transmission-Electron-Microscopy: observation of particle shape by high-angle scattering dark field-scanning transmission electron microscopy) Analysis) Performed by analysis. FIG. 5A is a HAADF-STEM image of the positive electrode active material after firing in Example 1, and FIG. 5B is an EDS map of iron atoms at the same observation location. ) Is an EDS map of silicon atoms at the same observation location, and FIG. 5D is an EDS map of oxygen atoms at the same observation location. FIG. 6 is a HAADF-STEM image and EDS map of the positive electrode active material after firing in Comparative Example 1.

  In FIG. 5A, particles covered with an amorphous substance can be observed. Further, in FIGS. 5B to 5D, the distribution of atoms of oxygen, iron, and silicon is consistent, so that the composition is uniform and uniform in the particles, and the composition is also uniform between the particles. As can be seen from FIG.

  Also in the positive electrode active material after firing according to Comparative Example 1 in FIG. 6, the distribution of atoms of oxygen, iron, and silicon is somewhat consistent, but the distribution is more consistent as the positive electrode active material according to the example. Absent.

(4) Preparation of positive electrode for test evaluation using active material sample and secondary battery 10% by weight of conductive additive (carbon black) with respect to positive electrode active material A and B obtained in Examples and Comparative Examples Then, the mixture was further mixed for 5 hours using a ball mill in which the inside was replaced with nitrogen. The mixed powder and polyvinylidene fluoride (PVdF) as a binder were mixed at a weight ratio of 95: 5, and N-methyl-2-pyrrolidone (NMP) was added and sufficiently kneaded to obtain a positive electrode slurry.

The surface roughness Rz (JIS B 0601-1994 ten-point average roughness) of the aluminum foil current collector having a 0.7μm thick 15 [mu] m, the positive electrode slurry was coated at a coat weight of 50 g / ^{m 2,} at 120 ° C. Dry for 30 minutes. Thereafter, it was rolled to a density of 2.0 g / cm ³ with a roll press, punched into a 2 cm ² disk shape, and used as a positive electrode.

Using these positive electrodes, metallic lithium for the negative electrode, and a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 in the electrolytic solution, LiPF ₆ was dissolved at a concentration of 1M, and a lithium secondary battery was used. Produced. The production atmosphere was a dew point of −50 ° C. or lower. Each electrode was used by being crimped to a battery case with a current collector. A coin-type lithium secondary battery having a diameter of 25 mm and a thickness of 1.6 mm was formed using the positive electrode, the negative electrode, the electrolyte, and the separator.

(5) Test Evaluation of Sample Next, test evaluation of the positive electrode active material of the present invention was performed as follows using the above coin-type lithium secondary battery.
Charged to 4.2 V (vs. Li / Li ⁺ ) at a test temperature of 25 ° C. and a CC-CV method at a current rate of 0.1 C, and then stopped after the current rate dropped to 0.005 C. . Thereafter, the battery was discharged at a rate of 0.1 C to 1.5 V (same as above) by the CC method, and the initial charge / discharge capacity was measured.
Next, charge / discharge characteristics at the second cycle were measured under the same conditions.

  FIG. 7A shows a charge / discharge curve for the first cycle of the positive electrode active material according to Example 1 and Comparative Example 1, and FIG. 7B shows a charge / discharge curve for the second cycle. Table 1 shows the discharge capacity.

  As shown in FIG. 7A, in the comparative example, the discharge capacity at the first cycle was about twice the charge capacity, but in the example having the compacting step before firing, The discharge capacity was about 1.1 times the charge capacity, and the balance of the initial charge / discharge capacity was improved in the example as compared with the comparative example.

  Further, as shown in FIG. 7B, in the second cycle, the charge capacity and the discharge capacity in the example were almost the same, and the charge capacity and the discharge capacity in the comparative example were also almost the same. However, the capacity of the example is higher than that of the comparative example.

  In the above-described embodiments, the fine particle mixture is formed by using the spray combustion method. However, when the fine particle mixture is fired, the fine particle mixture is formed into pellets or tablet-like green compacts, thereby obtaining a positive electrode. Owing to the structure of the present invention that suppresses the oxidation of the active material, the oxidation of the positive electrode active material can be similarly suppressed by using a fine particle mixture formed by spray pyrolysis.

  Moreover, it is thought that the effect of this invention is acquired also about the fine particle mixture obtained by the solid-phase reaction method or the hydrothermal synthesis method. That is, when carbon coating is performed on a fine particle mixture obtained by a solid phase reaction method or a hydrothermal synthesis method, after mixing a carbon source and firing in the state of a green compact as in the present invention, the positive electrode active material It is thought that oxidation can be suppressed.

  Moreover, in the above-mentioned Examples, iron was used as the transition metal element. However, when the fine particle mixture is fired, the fine particle mixture is molded into pellets or tablet-shaped green compacts, thereby obtaining the positive electrode active material obtained. From the configuration of the present invention that suppresses oxidation, it is considered that the oxidation of the positive electrode active material can be similarly suppressed even when other transition metal elements other than iron are used.

  As described above, the positive electrode obtained by applying the positive electrode active material of the present invention to a predetermined current collector is a rechargeable secondary battery such as a lithium ion secondary battery using a non-aqueous electrolyte. It can be used as a positive electrode exhibiting excellent charge / discharge characteristics. In the future, further improvements will serve as the basis for improving the charge / discharge capacity with the goal of the higher theoretical specific capacity inherent in the compound system of the present invention. Thereby, the characteristic which shows the high energy and the high output which are not in the past can be provided to the secondary battery for industrial use and automobile use which have been put into practical use such as conventional electronic equipment use. Moreover, among the method for producing the fine particle mixture of the present invention, the spray combustion method is particularly excellent in mass productivity and can provide a product at low cost.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

DESCRIPTION OF SYMBOLS 1 ......... Particle manufacturing apparatus 3 ......... Particle synthesis nozzle 5 ......... Particle collection filter 7 ......... Particle mixture 11 ......... Nonaqueous electrolyte secondary battery 13 ......... Positive electrode 15 ......... Negative electrode 17 ... … Separator 19 ……… Electrolyte 21 ……… Battery can 23 ……… Positive lead 25 ……… Negative lead 27 ……… Positive terminal 29 ……… Sealing body

Claims (10)

Supplying a lithium source, a transition metal source and a silicon source together with a combustion-supporting gas and a combustible gas into a flame to synthesize a fine particle mixture;
Mixing a carbon source in the fine particle mixture;
A step of (c) producing a green compact by filling and pressing the fine particle mixture mixed with the carbon source into a mold;
Firing the green compact in an inert gas-filled atmosphere (d);
Crushing the green compact (e),
A process for producing a lithium transition metal silicate positive electrode active material comprising: In the step (a),
The lithium source, the mixed solution containing the transition metal source and the silicon source, in the mist-like droplet, process for producing a positive electrode active material according to claim 1, characterized by supplying to the flame . In the step (a),
Process for producing a positive electrode active material according to claim 1 or claim 2 you, wherein the temperature of the flame is 1000 to 3000 ° C.. In the step (a),
The combustible gas is a hydrocarbon gas,
The method for producing a positive electrode active material according to claim 1 , wherein the combustion-supporting gas is air. (A) synthesizing a fine particle mixture by heating a mist-like droplet of a mixed solution containing a lithium source, a transition metal source and a silicon source;
Mixing a carbon source in the fine particle mixture;
A step of (c) producing a green compact by filling and pressing the fine particle mixture mixed with the carbon source into a mold;
Firing the green compact in an inert gas-filled atmosphere (d);
Crushing the green compact (e),
A process for producing a lithium transition metal silicate positive electrode active material comprising: The lithium source lithium compound is lithium chloride, lithium hydroxide, lithium acetate, lithium nitrate, lithium bromide, lithium phosphate, lithium sulfate, lithium oxalate, lithium naphthenate, lithium ethoxide, lithium oxide, lithium peroxide Any one or more of
The transition metal compound of the transition metal source is at least one transition metal chloride selected from the group consisting of Fe, Mn, Ti, Cr, V, Ni, Co, Cu, Zn, Zr, Mo, and W , Shu Acid salt, acetate salt, sulfate salt, nitrate salt, hydroxide, ethyl hexane salt, naphthenate salt, hexoate salt, cyclopentadienyl compound, alkoxide, organic acid metal salt (stearic acid, dimethyldithiocarbamic acid, acetylacetonate Oleic acid, linoleic acid, linolenic acid salt), or any one of oxides,
The silicon compound of the silicon source is silicon tetrachloride, octamethylcyclotetrasiloxane (OMCTS), silicon dioxide, silicon monoxide or a hydrate of these silicon oxides, condensed silicic acid, tetraethylorthosilicate (tetraethoxysilane, TEOS) , Tetramethylorthosilicate (tetramethoxysilane, TMOS), methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), hexamethyldisiloxane (HMDSO), tetramethyldisiloxane (TMDSO), tetramethylcyclotetrasiloxane (TMCTS), octamethyltrisiloxane (OMTSO), production of the positive electrode active material according to any one of claims 1 to 5, characterized in that either one or more tetra -n- butoxysilane Law. The method for producing a positive electrode active material according to any one of claims 1 to 6 , wherein the carbon source is polyvinyl alcohol. In the step (d),
The firing in an inert gas-filled atmosphere, the positive electrode active material according to any one of claims 1 to 7, which comprises carrying out the heat treatment of 0.5 to 10 hours at 300 to 900 ° C. Production method. A step of producing a slurry containing the positive electrode active material produced by the method of producing a positive electrode active material according to any one of claims 1 to 8 ,
Applying and baking the slurry to a current collector;
The manufacturing method of the positive electrode for nonaqueous electrolyte secondary batteries characterized by comprising. The slurry contains secondary particles having a size of 0.5 to 20 μm, which is granulated by adding the positive electrode active material produced by the method for producing a positive electrode active material according to any one of claims 1 to 8. The manufacturing method of the positive electrode for nonaqueous electrolyte secondary batteries of Claim 9 characterized by the above-mentioned.