Method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, and method for producing a non-aqueous electrolyte secondary battery

Abstract

The present invention provides a positive electrode active material for nonaqueous electrolyte secondary batteries, said positive electrode active material contributing to the achievement of a good balance between charge capacity and thermal stability. This positive electrode active material contains a lithium metal composite oxide which is represented by general formula xLiyNizM1-zO2-(1-x)LiwNizM1-zO2 (wherein 0.1 < x ≤ 1, 1.5 ≤ y ≤ 2.5, 0.4 < z ≤ 0.9, 0.9 ≤ w ≤ 1.5, and M represents one or more elements that are selected from the group consisting of transition metals, Al, Si, Sn, Ge, Sb, Bi, Mg, Ca and Sr); and the lithium metal composite oxide has a layered structure, while comprising Li element that is coordinated to the position of the oxygen tetrahedron.

Description

Technical Field

[0001] The present disclosure relates to a positive electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.

Background Art

[0002] Conventionally, non-aqueous electrolyte secondary batteries that perform charge and discharge by moving Li ions or the like between a positive electrode and a negative electrode have been widely used. In recent years, further improvement of battery characteristics has been demanded. Patent Document 1 discloses a secondary battery in which by including Li2NiO2 in the positive electrode, a sufficient amount of Li ions are supplied to the negative electrode during charging, showing an effect on over-discharge characteristics while suppressing a decrease in battery capacity.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the charging capacity (battery capacity) increases, the thermal stability may decrease. Li2NiO2 has poor reversibility in the absorption and release of Li ions, and the technology disclosed in Patent Document 1 may rather decrease the charging capacity of the battery when Li2NiO2 is included in the positive electrode. There is still room for improvement in achieving both high charging capacity and thermal stability.

[0005] Therefore, an object of the present disclosure is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that contributes to achieving both high charging capacity and thermal stability.

Means for Solving the Problems

[0006] A positive electrode active material for a non-aqueous electrolyte secondary battery, which is one aspect of the present disclosure, has a general formula xLi[[ID= 47]] ، ، z ، ،

[0006] ، 1-z ، ، y [[ID= 48]]Ni[[ID= 49]] z [[ID= 50]]M [[ID= 51]] 1-zO2-(1-x)Li w Ni z M 1-z O2(where 0.1 < x ≤ 1, 1.5 ≤ y ≤ 2.5, 0.4 < z ≤ 0.9, 0.9 ≤ w ≤ 1.5, and M is one or more elements selected from the group consisting of transition metals and Al, Si, Sn, Ge, Sb, Bi, Mg, Ca, and Sr). The lithium metal composite oxide has a layered structure and has Li elements coordinated at the tetrahedral positions of oxygen.

[0007] A non-aqueous electrolyte secondary battery according to one aspect of the present disclosure includes a positive electrode containing the positive electrode active material for the non-aqueous electrolyte secondary battery, a negative electrode, and a non-aqueous electrolyte. The negative electrode contains a negative electrode active material, and the negative electrode active material is Si, SiC, SiO α (0 < α < 2), Li β SiO γ (1 < β ≤ 4, 1 < γ ≤ 4), and contains 3% or more of a mixture of one or more selected from the group consisting of Sn, SnO2, Sb, and Ge.

Advantages of the Invention

[0008] According to the positive electrode active material for a non-aqueous electrolyte secondary battery, which is one aspect of the present disclosure, it is possible to improve the charging capacity of the battery while improving the thermal decomposition temperature.

Brief Description of the Drawings

[0009] [Figure 1] It is a cross-sectional view of a non-aqueous electrolyte secondary battery which is an example of an embodiment.

Modes for Carrying Out the Invention

[0010] A non-aqueous electrolyte secondary battery performs charge and discharge by moving Li ions or the like between a positive electrode and a negative electrode. During charge and discharge of the non-aqueous electrolyte secondary battery, a phenomenon is observed where a part of the Li ions that moved from the positive electrode to the negative electrode during charging is absorbed by the negative electrode active material and is not released from the negative electrode during discharging, resulting in a decrease in the capacity retention rate of the battery. This phenomenon is also observed when using a general carbon-based material such as graphite, and is particularly prominent when using an irreversible material such as a Si-based material. Therefore, in order to suppress the decrease in the capacity retention rate of charge and discharge, a method of supplying a sufficient amount of Li ions to the negative electrode during charging by including Li2NiO2 as a Li compensating agent in the positive electrode has been studied. However, Li2NiO2 has poor reversibility with respect to the absorption and release of Li ions, and including Li2NiO2 in the positive electrode may conversely decrease the charging capacity of the battery. Also, when the charging capacity increases, the thermal decomposition temperature decreases, and it is difficult to achieve both a high charging capacity and thermal stability.

[0011] Therefore, as a result of intensive studies to solve the above problems, the inventors of the present invention have found that by using a lithium metal composite oxide in which Ni is contained at a predetermined content rate and the coordination position of the Li element is specified as a positive electrode active material, it is possible to specifically achieve both a high charging capacity and thermal stability of the battery. The lithium metal composite oxide represented by the general formula xLi y Ni z M 1-z O2-(1-x)Li w Ni z M 1-z O2 has a higher charging capacity as the Ni content rate is higher (as y is larger), but the thermal decomposition temperature decreases. If z is in the range of 0.4 < z ≦ 0.9, it is possible to increase the thermal decomposition temperature while ensuring a sufficient charging capacity, and it is推测 that both the charging capacity and thermal stability can be achieved.

[0012] The following describes in detail an example of an embodiment of a non-aqueous electrolyte secondary battery according to this disclosure. In the following description, a cylindrical battery in which a wound electrode body is housed in a cylindrical outer casing is given as an example, but the electrode body is not limited to the wound type and may be a laminated type in which multiple positive electrodes and multiple negative electrodes are stacked alternately one by one with separators in between. Furthermore, the outer casing is not limited to a cylindrical shape and may be, for example, rectangular, coin-shaped, etc., or may be a battery case made of a laminate sheet including a metal layer and a resin layer.

[0013] Figure 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery 10, which is an example of an embodiment. As illustrated in Figure 1, the non-aqueous electrolyte secondary battery 10 comprises an electrode body 14, a non-aqueous electrolyte (not shown), and a battery case 15 that houses the electrode body 14 and the non-aqueous electrolyte. The electrode body 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound around a separator 13. The battery case 15 consists of a bottomed cylindrical outer casing 16 and a sealing body 17 that closes the opening of the outer casing 16.

[0014] The electrode body 14 consists of a long positive electrode 11, a long negative electrode 12, two long separators 13, a positive electrode tab 20 joined to the positive electrode 11, and a negative electrode tab 21 joined to the negative electrode 12. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in both the longitudinal and width (short-side) directions. The two separators 13 are formed to be at least slightly larger than the positive electrode 11 and are arranged, for example, to sandwich the positive electrode 11.

[0015] The non-aqueous electrolyte secondary battery 10 includes insulating plates 18 and 19 positioned above and below the electrode body 14, respectively. In the example shown in Figure 1, a positive electrode tab 20 attached to the positive electrode 11 extends towards the sealing body 17 through a through-hole in the insulating plate 18, and a negative electrode tab 21 attached to the negative electrode 12 extends towards the bottom of the outer casing 16 through the outside of the insulating plate 19. The positive electrode tab 20 is connected to the lower surface of the bottom plate 23 of the sealing body 17 by welding or the like, and the cap 27 of the sealing body 17, which is electrically connected to the bottom plate 23, becomes the positive electrode terminal. The negative electrode tab 21 is connected to the inner surface of the bottom of the outer casing 16 by welding or the like, and the outer casing 16 becomes the negative electrode terminal.

[0016] The outer container 16 is, for example, a metal container with a bottomed cylindrical shape. A gasket 28 is provided between the outer container 16 and the sealing body 17, sealing the internal space of the battery case 15. The outer container 16 has a grooved portion 22 that supports the sealing body 17, which is formed, for example, by pressing the side portion from the outside. The grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the outer container 16, and its upper surface supports the sealing body 17.

[0017] The sealing body 17 has a structure in which a bottom plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked in order from the electrode body 14 side. Each component constituting the sealing body 17 has, for example, a disc shape or a ring shape, and each component except the insulating member 25 is electrically connected to one another. The lower valve body 24 and the upper valve body 26 are connected to each other at their respective centers, with the insulating member 25 interposed between their respective peripheries. When the internal pressure of the battery rises due to abnormal heat generation, the lower valve body 24 deforms and ruptures, pushing the upper valve body 26 towards the cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure rises further, the upper valve body 26 ruptures, and gas is discharged from the opening of the cap 27.

[0018] The following provides a detailed explanation of the positive electrode 11, negative electrode 12, separator 13, and non-aqueous electrolyte that constitute the non-aqueous electrolyte secondary battery 10, with particular emphasis on the positive electrode active material contained in the positive electrode mixture layer 31 that constitutes the positive electrode 11.

[0019] [Positive electrode] The positive electrode 11 comprises a positive electrode current collector 30 and a positive electrode mixture layer 31 formed on both sides of the positive electrode current collector 30. The positive electrode current collector 30 can be made of a metal foil that is stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The positive electrode mixture layer 31 may contain a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder to the surface of the positive electrode current collector 30, drying the coating, and then compressing it to form the positive electrode mixture layer 31 on both sides of the positive electrode current collector 30.

[0020] Examples of the conductive agent contained in the positive electrode active material layer 31 include carbon-based materials such as carbon black, acetylene black, ketjen black, and graphite. Examples of the binder contained in the positive electrode active material layer 31 include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide, acrylic resin, and polyolefin. These resins may be used in combination with carboxymethyl cellulose (CMC) or its salt, polyethylene oxide (PEO), or the like.

[0021] The positive electrode active material contained in the positive electrode active material layer 31 is represented by the general formula xLi y Ni z M 1-z O2-(1-x)Li w Ni z M 1-z O2 (0.1 < x ≤ 1, 1.5 ≤ y ≤ 2.5, 0.4 < z ≤ 0.9, 0.9 ≤ w ≤ 1.5, M is one or more elements selected from the group consisting of transition metals and Al, Si, Sn, Ge, Sb, Bi, Mg, Ca, and Sr) includes a lithium metal composite oxide (Y). In addition, the positive electrode active material may contain a lithium metal composite oxide other than the lithium metal composite oxide (Y) or other compounds as long as the object of the present disclosure is not impaired.

[0022] The lithium metal composite oxide (Y) is, for example, secondary particles formed by aggregation of a plurality of primary particles. The particle size of the primary particles constituting the secondary particles is, for example, 0.05 to 1 μm. The particle size of the primary particles is measured as the diameter of the circumscribed circle in the particle image observed by a scanning electron microscope (SEM).

[0023] The particle size of the secondary particles of the lithium metal composite oxide (Y) is the median diameter (D50) based on volume, for example, 3 μm to 30 μm. D50 means the particle size at which the frequency cumulative in the particle size distribution based on volume becomes 50% from the smaller particle size side, and is also called the median diameter. The particle size distribution of the lithium metal composite oxide (Y) can be measured using a laser diffraction type particle size distribution measuring device (for example, MT3000II manufactured by Microtrac Bell Co., Ltd.) with water as the dispersion medium.

[0024] In the general formula xLi y Ni z M 1-z O2-(1-x)Li w Ni z M 1-z In O2, M is preferably one or more elements selected from the group consisting of Ni, Co, Mn, Fe, and Al.

[0025] The lithium metal composite oxide (Y) has a layered structure and has a Li element coordinated at the tetrahedral position of oxygen within one primary particle. The layered structure of the lithium metal composite oxide (Y) includes, for example, a transition metal layer, a Li layer, and an oxygen layer. The Li layer is a layer where Li reversibly enters and exits.

[0026] The lithium metal composite oxide (Y) is mainly of the space group R3-m and may have a region of the space group P3-m1 as a stacking defect. By introducing a region of the space group P3-m1 as a stacking defect while mainly having the space group R3-m, it is possible to achieve both charge capacity and thermal stability. In the general formula xLi y Ni z M 1-z O2-(1-x)Li w Ni z M 1-z In O2, x and (1-x) respectively indicate the ratio of the region of the space group P3-m1 and the region of the space group R3-m. x satisfies 0.1 < x ≤ 1, and 0.1 < x < 0.4 is preferable. If x is less than 0.4, the average discharge voltage of the battery can be increased.

[0027] The general formula xLi representing the lithium metal composite oxide (Y) y Ni z M 1-z O2-(1-x)Li w Ni z M 1-z The value of x in O2 can be calculated from the integrated intensity S1 of 17.1° or more and less than 18.1° and the integrated intensity S2 of 18.1° or more and less than 19.1°, which are measured by XRD measurement of CuKα, according to the following formula. x = S1 / (S1 + S2)

[0028] The XRD measurement may be performed under the following conditions using, for example, a powder X-ray diffractometer (manufactured by Rigaku Corporation, trade name "RINT-TTR", radiation source Cu-Kα). Measurement range: 15 - 120° Scan speed: 4° / min Analysis range: 30 - 120° Background: B-spline Profile function: Split pseudo-Voigt function ICSD No.: 98-009-4814

[0029] In the state of being discharged to 1.5V, the lithium metal composite oxide (Y) is the general formula xLi y MO2-(1-x)Li z It may have a composition represented by MO2 (0 < x < 0.4, 1.5 ≤ y ≤ 2.5, 0.9 ≤ z ≤ 1.1, M is the above M). The composition of the lithium metal composite oxide (Y) changes with the charge and discharge of the battery, but recovers to the above composition by discharging to 1.5V.

[0030] The lithium metal composite oxide (Y) contained in the positive electrode active material can be prepared, for example, by immersing a lithium metal composite oxide (X) having space group R3-m and Li metal in a benzophenone 2Me-THF solution, in which benzophenone is dissolved in 2-methyltetrahydrofuran (2-MeTHF), stirring at room temperature for 1 to 24 hours, and then filtering. Through this process, space group P3-m1 is introduced as a stacking fault into the lithium metal composite oxide (X) having space group R3-m. The proportion of space group P3-m1 introduced can be adjusted, for example, by temperature, the concentration of benzophenone in 2-MeTHF, stirring time, etc.

[0031] Lithium metal composite oxides (X) having space group R3-m can be synthesized, for example, by adding a Li source to a metal composite compound that does not contain Li, mixing the mixture, and calcining it at 200°C to 1050°C. Examples of metal composite compounds include oxides, hydroxides, and carbonates containing Ni, Mn, etc. Examples of Li sources include LiOH, etc. For example, increasing the Ni content in the metal composite compound increases the Ni content in the lithium metal composite oxide (Y). Metal composite compounds can be produced, for example, by heat-treating a hydroxide prepared by coprecipitation.

[0032] [Negative electrode] The negative electrode 12 comprises a negative electrode current collector 40 and a negative electrode mixture layer 41 formed on both sides of the negative electrode current collector 40. The negative electrode current collector 40 can be made of a metal foil that is stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal arranged on its surface. The negative electrode mixture layer 41 may contain a negative electrode active material and a binder. The negative electrode 12 can be manufactured, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the surface of the negative electrode current collector 40, drying the coating, and then rolling it to form the negative electrode mixture layer 41 on both sides of the negative electrode current collector 40. In the charged state, lithium metal may be deposited on the negative electrode 12.

[0033] The negative electrode active material contained in the negative electrode mixture layer 41 is not particularly limited as long as it can reversibly intercept and release lithium ions, and generally carbon-based materials such as graphite are used. The graphite may be any of the following: natural graphite such as flake graphite, lump graphite, or clay-like graphite; lump artificial graphite; or artificial graphite such as graphitized mesophase carbon microbeads. In addition, metals that alloy with Li such as Si and Sn, metal compounds containing Si and Sn, or lithium titanium composite oxides may be used as the negative electrode active material. Furthermore, materials with a carbon coating may be used. The negative electrode active material may be Si, SiC, or SiO α (0<α<2), Li β SiO γ It is preferable that the material contains 3% or more of one or more elements selected from the group consisting of (1<β≦4, 1<γ≦4), Sn, SnO2, Sb, and Ge.

[0034] The binder in the negative electrode mixture layer 41 may be a fluororesin such as PTFE or PVdF, PAN, polyimide, acrylic resin, or polyolefin, similar to the case of the positive electrode 11, but styrene-butadiene rubber (SBR) is preferably used. The negative electrode mixture layer 41 may also contain CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, or polyvinyl alcohol (PVA).

[0035] [Separator] For example, a porous sheet having ion permeability and insulating properties can be used for the separator 13. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator include polyethylene, polyolefins such as polypropylene, and cellulose. The separator 13 may have a single-layer structure or a laminated structure. Furthermore, the surface of the separator 13 may be provided with a highly heat-resistant resin layer such as aramid resin, and a filler layer containing an inorganic compound filler.

[0036] [Non-aqueous electrolytes] Non-aqueous electrolytes include, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, and mixtures of two or more of these. The non-aqueous solvent may contain halogen-substituted solvents in which at least some of the hydrogen atoms in the solvent are replaced with halogen atoms such as fluorine. Examples of halogen-substituted solvents include fluorinated cyclic carbonate esters such as fluoroethylene carbonate (FEC), fluorinated linear carbonate esters, and fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP).

[0037] Examples of the above esters include cyclic carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate; linear carbonate esters such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate; cyclic carboxylic acid esters such as γ-butyrolactone (GBL) and γ-valerolactone (GVL); and linear carboxylic acid esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate (EP).

[0038] Examples of the above ethers include cyclic ethers such as 1,3 - dioxolane, 4 - methyl - 1,3 - dioxolane, tetrahydrofuran, 2 - methyltetrahydrofuran, propylene oxide, 1,2 - butylene oxide, 1,3 - dioxane, 1,4 - dioxane, 1,3,5 - trioxane, furan, 2 - methylfuran, 1,8 - cineole, crown ether, etc.; chain ethers such as 1,2 - dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl ether, methoxytoluene, benzyl ethyl ether, diphenyl ether, dibenzyl ether, o - dimethoxybenzene, 1,2 - diethoxyethane, 1,2 - dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,1 - dimethoxymethane, 1,1 - diethoxyethane, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, etc.

[0039] The electrolyte salt is preferably a lithium salt. Examples of lithium salts include LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiAlCl4, LiSCN, LiCF3SO3, LiCF3CO2, Li(P(C2O4)F4), LiPF 6-x (C n F 2n+1 ) x (1 < x < 6, n is either 1 or 2), LiB 10 Cl 10 , LiCl, LiBr, LiI, lithium chloroborane, lithium lower aliphatic carboxylate, borate salts such as Li2B4O7, Li(B(C2O4)F2), etc.; LiN(SO2CF3)2, LiN(C1F 2l+1 SO2)(C m F 2m+1Examples include imide salts such as SO2){l,m are integers greater than or equal to 0}. Lithium salts may be used individually or in mixtures of multiple types. Of these, LiPF6 is preferred from the viewpoint of ionic conductivity and electrochemical stability. The concentration of the lithium salt is, for example, 0.8 moles to 1.8 moles per liter of non-aqueous solvent. Furthermore, vinylene carbonate or propane-sultone additives may be added. [Examples]

[0040] The present disclosure will be further explained below with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0041] <Examples> [Fabrication of positive electrode active material] The composition obtained by coprecipitation is Ni 0.5 Mn 0.5 (OH)2 nickel-manganese composite hydroxide is heat-treated at 500°C, and the composition becomes Ni 0.5 Mn 0.5 A nickel-manganese composite oxide of O2 was obtained. Next, the nickel-manganese composite oxide and LiOH were mixed so that the molar ratio of the total amount of Ni and Mn to Li was 1.02:1. After calcining this mixture at 900°C for 10 hours, it was pulverized to obtain a lithium metal composite oxide (X) having R3-m.

[0042] Lithium metal composite oxide (X) and Li metal were immersed in a 1 mol / L benzophenone 2Me-THF solution, stirred at room temperature for 12 hours, and then filtered to prepare lithium metal composite oxide (Y), which was used as the positive electrode active material. XRD measurement revealed that the x value of this positive electrode active material was 0.49.

[0043] [Fabrication of the positive electrode] The positive electrode active material, acetylene black, and polyvinylidene fluoride (PVdF) were mixed in a solid content mass ratio of 96.3:2.5:1.2. An appropriate amount of N-methyl-2-pyrrolidone (NMP) was added, and the mixture was kneaded to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to both sides of a positive electrode core made of aluminum foil, and after the coating film was dried, the coating film was rolled using a roller and cut to a predetermined electrode size to obtain a positive electrode in which a positive electrode mixture layer was formed on both sides of the positive electrode core.

[0044] [Preparation of non-aqueous electrolytes] Fluoroethylene carbonate (FEC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 1:1:6 to obtain a non-aqueous solvent. LiPF6 was dissolved in this non-aqueous solvent at a concentration of 1.0 mol / L to obtain a non-aqueous electrolyte.

[0045] [Preparation of test cells] Lead wires were attached to the positive electrode and the lithium metal counter electrode, respectively, and the electrode body was fabricated by arranging the positive electrode and the counter electrode opposite each other via a polyolefin separator. This electrode body and the non-aqueous electrolyte were sealed in an outer casing made of aluminum laminate film to create a test cell.

[0046] [Measuring charging capacity] Under a temperature of 25°C, constant current charging was performed at a constant current of 0.2C until the cell voltage reached 4.5V, and then constant voltage charging was performed until the current value was 0.02C at 4.5V. Subsequently, constant current discharge was performed at a constant current of 0.2C until the cell voltage reached 2.5V. The charging capacity at this time was measured.

[0047] [Measurement of pyrolysis temperature] The thermal decomposition temperature of the above-mentioned positive electrode active material (lithium metal composite oxide (Y)) was measured using differential scanning calorimetry (DSC). The measurement conditions were under a nitrogen atmosphere with a heating rate of 10°C / min.

[0048] <Example 2> In the preparation of the positive electrode active material, the composition is Ni0.8 Mn 0.2 A test cell was prepared and evaluated in the same manner as in Example 1, except that an O2 nickel-manganese composite oxide was used. The XRD measurement results showed that the x value of the positive electrode active material was 0.57.

[0049] <Comparative Example> A test cell was prepared and evaluated in the same manner as in Example 1, except that Li2NiO2 with a space group lmmm was used as the positive electrode active material.

[0050] Table 1 shows the charging capacity and thermal decomposition temperature of the examples and comparative examples. Table 1 also shows the crystal structure of the positive electrode active material and the ratio of Ni to the total amount of metal elements excluding Li in the positive electrode active material (Ni content).

[0051] [Table 1]

[0052] As shown in Table 1, the test cell of the example was able to achieve a higher thermal decomposition temperature while securing sufficient charging capacity compared to the test cell of the comparative example, demonstrating that both charging capacity and thermal stability are achieved. [Explanation of symbols]

[0053] 10 Non-aqueous electrolyte secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Battery case, 16 Outer casing, 17 Sealing body, 18,19 Insulating plate, 20 Positive electrode tab, 21 Negative electrode tab, 22 Grooved section, 23 Bottom plate, 24 Lower valve body, 25 Insulating material, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Positive electrode current collector, 31 Positive electrode mixture layer, 40 Negative electrode current collector, 41 Negative electrode mixture layer

Claims

1. A first lithium metal composite oxide having a single-phase structure is immersed in a solution in which benzophenone is dissolved to cause stacking faults in the first lithium metal composite oxide, A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising producing a lithium-2 metal composite oxide represented by the general formula xLi y Ni z M 1-z O 2 - (1-x)Li w Ni z M 1-z O 2 (0.1 < x < 1, 1.5 ≤ y ≤ 2.5, 0.4 < z ≤ 0.9, 0.9 ≤ w ≤ 1.5, where M is a transition metal and one or more elements selected from the group consisting of Al, Si, Sn, Ge, Sb, Bi, Mg, Ca, and Sr), exhibiting a composition in which multiple phases coexist within the same crystal, having a layered structure, and containing a Li element coordinated to the tetrahedral position of oxygen.

2. The second lithium metal composite oxide is a secondary particle formed by the aggregation of a plurality of primary particles, The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the volume-based median diameter (D50) of the secondary particles is 3 μm or more and 30 μm or less.

3. The first lithium metal composite oxide has a space group R3-m, The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the second lithium metal composite oxide mainly consists of space group R3-m and has a region of space group P3-m1 as a stacking fault.

4. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein M is one or more elements selected from the group consisting of Ni, Co, Mn, Fe, and Al.

5. A method for manufacturing a non-aqueous electrolyte secondary battery, comprising manufacturing a positive electrode containing a positive electrode active material for a non-aqueous electrolyte secondary battery as described in any one of claims 1 to 4, and combining it with a negative electrode and a non-aqueous electrolyte, The aforementioned negative electrode includes a negative electrode active material. The negative electrode active material is Si, SiC, SiO α (0 < α < 2, Li β SiO γ (1<β≦4, 1<γ≦4), Sn, SnO ２ A method for producing a non-aqueous electrolyte secondary battery, comprising a mixture containing 3% or more of one or more elements selected from the group consisting of Sb and Ge.

6. A method for manufacturing a non-aqueous electrolyte secondary battery according to claim 5, wherein lithium metal is deposited on the negative electrode when the battery is charged.

7. In the state of being discharged to 1.5 V, the second lithium metal composite oxide has the general formula xLi ｙ Ni ｚ M １－ｚ O ２ -(1 - x)Li ｗ Ni ｚ M １－ｚ O ２ (0.1 < x ≤ 1, 1.5 ≤ y ≤ 2.5, 0.4 < z ≤ 0.9, 0.9 ≤ w ≤ 1.5, M is the above M), the method for manufacturing a non-aqueous electrolyte secondary battery according to claim 6.

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