Positive electrode active material for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery

Abstract

Provided is a positive electrode active material for a non-aqueous electrolyte secondary battery, the material contributing to both charge capacity and discharge voltage. This positive electrode active material contains a lithium metal composite oxide represented by general formula xLiyMO2-(1-x)LizMO2 (where 0<x<0.4, 1.5≤y≤2.5, and 0.9≤z≤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 structurer, and has, in a single secondary particle, Li occupying an oxygen tetrahedral site and Li occupying an oxygen octahedral site.

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 technology]

[0002] Non-aqueous electrolyte secondary batteries, which are charged and discharged by transferring Li ions between a positive electrode and a negative electrode, have been widely used for some time, and in recent years, there has been a demand for further improvements in battery characteristics. Patent Document 1 discloses a secondary battery that contains Li2NiO2 in the positive electrode, thereby supplying a sufficient amount of Li ions to the negative electrode during charging, thereby improving overdischarge characteristics and suppressing a decrease in battery capacity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2005-521220 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as the charge capacity (battery capacity) increases, the discharge voltage may decrease. Li2NiO2 has poor reversibility in absorbing and releasing Li ions, and the technology disclosed in Patent Document 1 may actually decrease the charge capacity of the battery by including Li2NiO2 in the positive electrode. Therefore, there is still room for improvement in achieving both charge capacity and discharge voltage.

[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 a high charge capacity and a high discharge voltage. [Means for solving the problem]

[0006] The positive electrode active material for a nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure is a material represented by the general formula xLi y MO2-(1-x)Li zIt contains a lithium metal composite oxide represented by MO2 (0 < x < 0.4, 1.5 ≤ y ≤ 2.5, 0.9 ≤ z ≤ 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). The lithium metal composite oxide has a layered structure and has Li elements coordinated at the tetrahedral positions of oxygen and Li elements coordinated at the octahedral positions of oxygen within one secondary particle.

[0007] A non-aqueous electrolyte secondary battery, which is an aspect of the present disclosure, includes a positive electrode containing the above positive electrode active material for a 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 one or a mixture of two 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 an aspect of the present disclosure, it is possible to improve the discharge voltage while improving the charge capacity of the battery.

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 charging and discharging of the non-aqueous electrolyte secondary battery, a part of the Li ions that have 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 phenomenon where the capacity retention rate of the battery decreases. This phenomenon is also observed when using a carbon-based material such as common 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 charging and discharging, a method of supplying a sufficient amount of Li ions to the negative electrode during charging by including Li2NiO2 as a Li compensator 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 reduce the charging capacity of the battery. Further, when the charging capacity increases, the discharge voltage decreases, and it is difficult to achieve both the charging capacity and the discharge voltage.

[0011] Therefore, as a result of intensive studies to solve the above problems, the present inventors have found that by using a lithium metal composite oxide having a specific composition and specifying the coordination position of Li elements as a positive electrode active material, it is possible to specifically achieve both the charging capacity and the discharge voltage of the battery. The lithium metal composite oxide is represented by the general formula xLi y MO2-(1-x)Li z MO2. If it is in the range of 0 < x < 0.4, since the ratio of the Li element coordinated at the tetrahedral position of oxygen and the Li element coordinated at the octahedral position of oxygen can be set within a preferable range, it is推测 that the charging capacity and the discharge voltage are compatible.

[0012] Hereinafter, an example of an embodiment of a non-aqueous electrolyte secondary battery according to the present disclosure will be described in detail. Hereinafter, a cylindrical battery in which a wound electrode body is housed in a cylindrical outer casing will be exemplified, but the electrode body is not limited to a wound type, and may be a laminated type in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated one by one through a separator. Further, the outer casing is not limited to a cylindrical shape, and may be, for example, a rectangular shape, a coin shape, etc., or may be a battery case composed of a laminate sheet including a metal layer and a resin layer.

[0013] Fig. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery 10 according to an embodiment. As illustrated in Fig. 1, the nonaqueous electrolyte secondary battery 10 includes an electrode assembly 14, a nonaqueous electrolyte (not shown), and a battery case 15 that accommodates the electrode assembly 14 and the nonaqueous electrolyte. The electrode assembly 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound with a separator 13 interposed therebetween. The battery case 15 includes a cylindrical outer can 16 with a bottom, and a sealing member 17 that closes the opening of the outer can 16.

[0014] The electrode assembly 14 is composed 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 the longitudinal direction and width direction (short direction). The two separators 13 are formed to be at least slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11, for example.

[0015] The nonaqueous electrolyte secondary battery 10 includes insulating plates 18 and 19 disposed above and below the electrode assembly 14. In the example shown in Fig. 1 , a positive electrode tab 20 attached to the positive electrode 11 passes through a through-hole in the insulating plate 18 and extends toward the sealing body 17, and a negative electrode tab 21 attached to the negative electrode 12 passes outside the insulating plate 19 and extends toward the bottom of the outer can 16. The positive electrode tab 20 is connected to the underside of a bottom plate 23 of the sealing body 17 by welding or the like, and a cap 27 of the sealing body 17 electrically connected to the bottom plate 23 serves as the positive electrode terminal. The negative electrode tab 21 is connected to the inner bottom surface of the outer can 16 by welding or the like, and the outer can 16 serves as the negative electrode terminal.

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

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

[0018] The positive electrode 11, negative electrode 12, separator 13, and nonaqueous electrolyte that constitute the nonaqueous electrolyte secondary battery 10 will be described in detail below, particularly 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 has 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 a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed 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 produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and the like 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 fluorine resins 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), and the like.

[0021] The positive electrode active material contained in the positive electrode active material layer 31 is a lithium metal composite oxide (Y) represented by the general formula xLi y MO2-(1-x)Li z MO2 (0 < x < 0.4, 1.5 ≤ y ≤ 2.5, 0.9 ≤ z ≤ 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). 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, and is, for example, 3 μm to 30 μm. D50 means the particle size at which the cumulative frequency in the volume-based particle size distribution becomes 50% from the smaller particle size, 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 Corporation) with water as a dispersion medium.

[0024] The general formula xLi representing the lithium metal composite oxide (Y) yMO₂-(1-x)Li z In MO₂, M is preferably at least one element 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 Li elements coordinated at the tetrahedral positions of oxygen and Li elements coordinated at the octahedral positions of oxygen within one secondary 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 can reversibly enter and exit.

[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 being mainly of the space group R3-m, the charge capacity is improved and the crystal structure is stabilized. By having a region of the space group P3-m1 as a stacking defect, the discharge voltage is improved. The general formula representing the lithium metal composite oxide (Y) is xLi y MO₂-(1-x)Li z In MO₂, x and (1 - x) each represent the ratio of the region of the space group P3-m1 to the region of the space group R3-m.

[0027] The lithium metal composite oxide (Y) has peaks at 17.1° or more and less than 18.1° and at 18.1° or more and less than 19.1° in the XRD measurement of CuKα, and 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° may satisfy 0 < S1 / (S1 + S2) < 0.4. S1 / (S1 + S2) represents the ratio of the region of the space group P3-m1.

[0028] The XRD measurement may be performed under the following conditions, for example, using 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: Divided pseudo-Voigt function ICSD No.: 98-009-4814

[0029] In the state of being discharged up to 1.5 V, the lithium metal composite oxide (Y) may have a composition represented by the general formula xLi y MO2-(1-x)Li z MO2(0 < x < 0.4, 1.5 ≤ y ≤ 2.5, 0.9 ≤ z ≤ 1.5, 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 up to 1.5 V.

[0030] The lithium metal composite oxide (Y) contained in the positive electrode active material can be produced, for example, by immersing a lithium metal composite oxide (X) having a 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. By the above process, a space group P3-m1 is introduced as a stacking defect into the lithium metal composite oxide (X) having a space group R3-m. The ratio of introducing the space group P3-m1 can be adjusted, for example, by temperature, the concentration of benzophenone in 2-MeTHF, stirring time, etc.

[0031] The lithium metal composite oxide (X) having a space group R3-m can be synthesized, for example, by adding a Li source to a metal composite compound containing no Li, mixing them, and firing at 200°C to 1050°C. Examples of the metal composite compound include oxides, hydroxides, carbonate compounds, etc. containing Ni, Mn, etc. Examples of the Li source include LiOH, etc.

[0032] [Negative electrode] 0000156The negative electrode 12 has 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 a foil of a metal, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film with such a metal disposed 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 produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material, a binder, and the like to the surface of the negative electrode current collector 40, drying the coating, and then rolling the coating to form the negative electrode mixture layer 41 on both sides of the negative electrode current collector 40. Note that lithium metal may be precipitated on the negative electrode 12 in a charged state.

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

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

[0035] [Separator] The separator 13 may be, for example, a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator include polyolefins such as polyethylene and 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 an aramid resin, or a filler layer containing an inorganic compound filler.

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

[0037] Examples of the esters include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate; chain carbonates 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 chain 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.; and 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 the lithium salt 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 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 of the lithium salt include imide salts such as PF6 (LiPF2) (where l and m are integers of 0 or more). The lithium salt may be used alone or in combination. Among these, LiPF6 is preferred from the viewpoints of ionic conductivity, electrochemical stability, etc. The concentration of the lithium salt is, for example, 0.8 mol to 1.8 mol per liter of the non-aqueous solvent. Furthermore, vinylene carbonate or a propane sultone-based additive may be added. [Example]

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

[0041] <Example> [Preparation of positive electrode active material] Co-precipitation of Ni 0.8 Mn 0.2 A nickel-manganese composite hydroxide of (OH)2 was heat-treated at 500°C to obtain a nickel-manganese composite oxide. 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. This mixture was fired at 900°C for 10 hours and then pulverized to obtain a lithium metal composite oxide (X) having R3-m.

[0042] The 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 a lithium metal composite oxide (Y), which was used as the positive electrode active material. As a result of XRD measurement, the S1 / (S1+S2) ratio of the lithium metal composite oxide (Y) was 0.21.

[0043] [Preparation of positive electrode] The positive electrode active material, acetylene black, and polyvinylidene fluoride (PVdF) were mixed in a solids mass ratio of 96.3:2.5:1.2, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added. The mixture was then 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 the coating was dried. The coating was then rolled using a roller and cut to a predetermined electrode size, resulting in a positive electrode having a positive electrode mixture layer formed on both sides of the positive electrode core.

[0044] [Preparation of non-aqueous electrolyte] A non-aqueous solvent was prepared by mixing fluoroethylene carbonate (FEC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:6. LiPF6 was dissolved in the non-aqueous solvent at a concentration of 1.0 mol / L to prepare a non-aqueous electrolyte.

[0045] [Test cell construction] An electrode assembly was fabricated by attaching lead wires to the positive electrode and the counter electrode made of Li metal, and arranging the positive electrode and the counter electrode facing each other with a polyolefin separator in between. This electrode assembly and the non-aqueous electrolyte were enclosed in an exterior body made of an aluminum laminate film to fabricate a test cell.

[0046] [Charge capacity and average discharge voltage measurement] In a temperature environment of 25°C, the battery was charged at a constant current of 0.2 C until the cell voltage reached 4.5 V, and then at 4.5 V, it was charged at a constant voltage of 0.02 C. It was then discharged at a constant current of 0.2 C until the cell voltage reached 2.5 V. The charge capacity and average discharge voltage were measured.

[0047] <Comparative Example 1> A test cell was produced and evaluated in the same manner as in Example 1, except that in the preparation of the positive electrode active material, the stirring time of the lithium metal composite oxide (X) in the benzophenone 2Me-THF solution was changed to 24 hours.

[0048] <Comparative Example 2> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except that the stirring conditions for the lithium metal composite oxide (X) in the benzophenone 2Me-THF solution were changed to 45°C for 24 hours, and evaluation was carried out.

[0049] <Comparative Example 3> A test cell was prepared and evaluated in the same manner as in Example 1, except that in the preparation of the positive electrode active material, the lithium metal composite oxide (X) was not immersed in the benzophenone 2Me-THF solution, and the lithium metal composite oxide (X) was used as the positive electrode active material.

[0050] <Comparative Example 4> In the preparation of the positive electrode active material, a test cell was prepared in the same manner as in Example 1, except that the stirring conditions for the lithium metal composite oxide (X) in the benzophenone 2Me-THF solution were changed to 45°C for 48 hours, and evaluation was carried out.

[0051] The charge capacities and average discharge voltages of the examples and comparative examples are shown in Table 1. Table 1 also shows the S1 / (S1+S2) value of each positive electrode active material calculated by XRD measurement.

[0052] [Table 1]

[0053] As shown in Table 1, the test cells of the example have a better balance between charge capacity and average discharge voltage than the test cells of comparative examples 1 to 4, and are able to improve the discharge voltage while improving the charge capacity. [Explanation of symbols]

[0054] 10 non-aqueous electrolyte secondary battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 15 battery case, 16 outer can, 17 sealing body, 18, 19 insulating plate, 20 positive electrode tab, 21 negative electrode tab, 22 grooved portion, 23 bottom plate, 24 lower valve body, 25 insulating member, 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 non-aqueous electrolyte secondary battery comprising a positive electrode containing a positive electrode active material for a non-aqueous electrolyte secondary battery, a negative electrode, and a non-aqueous electrolyte, General formula xLi ｙ MO ２ -(1-x)Li ｚ MO ２ (0<x<0.4, 1.5≦y≦2.5, 0.9≦z≦1.5, 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), and the lithium metal composite oxide exhibits a composition in which the lithium metal composite oxide coexists as a multiphase structure in the same crystal, and the multiphase structure has two different layer structures, The lithium metal composite oxide has a layered structure, and each secondary particle contains Li elements coordinated to tetrahedral oxygen positions and Li elements coordinated to octahedral oxygen positions. When discharged to 1.5 V, the lithium metal composite oxide recovers to a composition represented by the general formula xLi y MO 2 -(1-x)Li z MO 2 (0<x<0.4, 1.5≦y≦2.5, 0.9≦z≦1.1, and M is the M).

2. 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium metal composite oxide is mainly composed of space group R3-m and has a region of space group P3-m1 as stacking faults.

3. 3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein, in CuKα XRD measurement, the lithium metal composite oxide has peaks at angles of 17.1° or more and less than 18.1° and 18.1° or more and less than 19.1°, respectively, and an integrated intensity S1 at 17.1° or more and less than 18.1° and an integrated intensity S2 at 18.1° or more and less than 19.1° satisfy the relationship 0<S1 / (S1+S2)<0.

4.

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

5. A secondary battery comprising a positive electrode containing the positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, a negative electrode, and a non-aqueous electrolyte, the 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 1. A non-aqueous electrolyte secondary battery comprising 3% or more of a mixture of one or more elements selected from the group consisting of Sb, Sb, and Ge.

6. 6. The nonaqueous electrolyte secondary battery according to claim 5, wherein lithium metal is deposited on the negative electrode in a charged state.

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