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

Abstract

A positive electrode active material for a non-aqueous electrolyte secondary battery according to one embodiment comprises a lithium transition metal composite oxide represented by the compositional formula LiαNaβNi1-b-cMnbXcOd (where X is at least one element selected from metallic elements other than Li, Na, Ni, and Mn, 0.80≤α≤1.20, 0≤β≤0.05, 0.80≤α+β≤1.20, 0.25<b≤0.65, 0≤c≤0.1, 0.4≤1-b-c<0.75, and d is a value satisfying the valence), and the ratio I108 / I110 of the integrated intensity I108 of the diffraction peak at the (108) plane to the integrated intensity I110 of the diffraction peak at the (110) plane of the x-ray diffraction pattern obtained by powder x-ray diffraction of the lithium transition metal composite oxide is I108 / I110<0.4.

Description

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

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

[0002] In recent years, non-aqueous electrolyte secondary batteries such as lithium ion batteries have attracted attention as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs, PHEVs), etc., and further expansion of their applications is expected. To be used as such power sources, non-aqueous electrolyte secondary batteries must have a higher capacity and improved charge / discharge efficiency.

[0003] Ni-containing lithium transition metal composite oxides have attracted attention as a positive electrode active material that can realize high-capacity non-aqueous electrolyte secondary batteries. For example, Patent Document 1 discloses a Ni-containing lithium transition metal composite oxide in which the half-widths of the diffraction peaks of the (108) and (110) planes are 0.18° or less in powder X-ray diffraction (XRD).

[0004] Japanese Patent Application Laid-Open No. 2005-053764

[0005] In non-aqueous electrolyte secondary batteries, increasing capacity and improving charge / discharge efficiency are important challenges. Conventional techniques including those described in Patent Document 1 have not been able to adequately address these challenges, and there is still much room for improvement.

[0006] An object of the present disclosure is to provide a positive electrode active material that can realize a non-aqueous electrolyte secondary battery with increased capacity and improved charge / discharge efficiency.

[0007] The positive electrode active material for a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure has the composition formula Li α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ(wherein X is at least one element selected from metal elements other than Li, Na, Ni, and Mn, and 0.80≦α≦1.20, 0≦β≦0.05, 0.80≦α+β≦1.20, 0.25<b≦0.65, 0≦c≦0.1, 0.4≦1−b−c<0.75, and d is a value satisfying the valence), and the lithium transition metal composite oxide has an integrated intensity I of a diffraction peak of a (110) plane in an X-ray diffraction pattern obtained by powder X-ray diffraction of the lithium transition metal composite oxide. １１０ The integrated intensity of the diffraction peak of the (108) plane I １０８ Ratio I １０８ / I １１０ But, I １０８ / I １１０ <0.4.

[0008] A non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure includes a positive electrode containing the above-described positive electrode active material, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte.

[0009] According to the positive electrode active material for a non-aqueous electrolyte secondary battery according to one aspect of the present disclosure, it is possible to provide a non-aqueous electrolyte secondary battery with increased capacity and improved charge / discharge efficiency.

[0010] FIG. 1 is a longitudinal cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment; FIG. 2 is a powder X-ray diffraction pattern of the lithium transition metal composite oxide prepared in Example 1; FIG. 3 is a powder X-ray diffraction pattern of the lithium transition metal composite oxide prepared in Example 2; FIG. 4 is a powder X-ray diffraction pattern of the lithium transition metal composite oxide prepared in Example 3; FIG. 5 is a powder X-ray diffraction pattern of the lithium transition metal composite oxide prepared in Example 4; FIG. 6 is a powder X-ray diffraction pattern of the lithium transition metal composite oxide prepared in Example 5; FIG. 7 is a powder X-ray diffraction pattern of the lithium transition metal composite oxide prepared in Example 6; FIG. 8 is a powder X-ray diffraction pattern of the lithium transition metal composite oxide prepared in Example 9; FIG. 9 is a powder X-ray diffraction pattern of the lithium transition metal composite oxide prepared in Example 10; FIG. 11 is a powder X-ray diffraction pattern of the lithium transition metal composite oxide prepared in Example 11; FIG. 12 is a powder X-ray diffraction pattern of the lithium transition metal composite oxide prepared in Example 12. FIG. 1 is a diagram showing a powder X-ray diffraction pattern of the lithium transition metal composite oxide produced in Comparative Example 1. FIG. 2 is a diagram showing a powder X-ray diffraction pattern of the lithium transition metal composite oxide produced in Comparative Example 2. FIG. 3 is a diagram showing a powder X-ray diffraction pattern of the lithium transition metal composite oxide produced in Comparative Example 3. FIG. 4 is a diagram showing a powder X-ray diffraction pattern of the lithium transition metal composite oxide produced in Comparative Example 4. FIG. 5 is a diagram showing a powder X-ray diffraction pattern of the lithium transition metal composite oxide produced in Comparative Example 5. FIG. 6 is a diagram showing a powder X-ray diffraction pattern of the lithium transition metal composite oxide produced in Comparative Example 6. FIG. 7 is a diagram showing a powder X-ray diffraction pattern of the lithium transition metal composite oxide produced in Comparative Example 7. FIG. 8 is a diagram showing an SEM image of the lithium transition metal composite oxide produced in Example 1. FIG. 9 is a diagram showing an SEM image of the lithium transition metal composite oxide produced in Comparative Example 1.

[0011] In the preparation of lithium-transition metal composite oxides containing Ni, the Ni element may be mixed into the Li site, i.e., disorder may occur. This disorder inhibits the diffusion of Li ions in the lithium-transition metal composite oxide, which is one of the causes of a decrease in the charge-discharge capacity and charge-discharge efficiency of the battery.

[0012] Therefore, the present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have found that in a lithium transition metal composite oxide in which Li, Ni, and Mn are essential elements in a positive electrode active material and the ratio of Ni to the total number of moles of metal elements excluding Li and Na is 40 mol % or more and less than 75 mol %, the integrated intensity I of the diffraction peak of the (110) plane in the X-ray diffraction pattern of the composite oxide obtained by X-ray diffraction is １１０ The integrated intensity of the diffraction peak of the (108) plane I １０８ Ratio I １０８ / I １１０ It has been found that by making the ratio of I to be less than 0.4, it is possible to provide a nonaqueous electrolyte secondary battery with improved charge-discharge efficiency while achieving a high capacity. １０８ / I １１０ It is presumed that by making the value of the ratio less than 0.4, the stability of the layered rock salt structure of the lithium transition metal composite oxide is improved, and the amount of disorder generated is specifically reduced.

[0013] Hereinafter, with reference to the drawings, an example of an embodiment of a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present disclosure and a non-aqueous electrolyte secondary battery using the active material will be described in detail. Note that the scope of the present disclosure includes configurations obtained by selectively combining the respective components of the multiple embodiments and modifications described below.

[0014] In the embodiment described below, a cylindrical battery in which a wound electrode assembly 14 is housed in a cylindrical outer can 16 with a bottom is exemplified, but the outer can of the battery is not limited to a cylindrical outer can. Other embodiments of the nonaqueous electrolyte secondary battery according to the present disclosure include a prismatic battery having a prismatic outer can, a coin-shaped battery having a coin-shaped outer can, and a pouch-shaped battery having an outer can made of a laminate sheet including a metal layer and a resin layer. In addition, the electrode assembly is not limited to a wound type, and may be a stacked type electrode assembly in which multiple positive electrodes and multiple negative electrodes are alternately stacked with separators interposed therebetween.

[0015] 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 a wound electrode assembly 14, a nonaqueous electrolyte, and an outer can 16 that accommodates the electrode assembly 14 and the electrolyte. The electrode assembly 14 includes a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The outer can 16 is a cylindrical metal container with a bottom that is open on one axial side, and the opening of the outer can 16 is closed by a sealing member 17. Hereinafter, for convenience of explanation, the sealing member 17 side of the battery will be referred to as the top, and the bottom side of the outer can 16 will be referred to as the bottom.

[0016] The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, 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 of these solvents are substituted with halogen atoms such as fluorine. The electrolyte salt may be, for example, LiPF ６ , LiClO ４ , LiBF ４ The electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte using a gel polymer or the like.

[0017] The positive electrode 11, negative electrode 12, and separator 13 that constitute the electrode assembly 14 are all strip-shaped, long bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium precipitation. 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, for example, to sandwich the positive electrode 11. The electrode assembly 14 has a positive electrode lead 20 connected to the positive electrode 11 by welding or the like, and a negative electrode lead 21 connected to the negative electrode 12 by welding or the like.

[0018] Insulating plates 18 and 19 are disposed above and below the electrode body 14. In the example shown in Fig. 1 , the positive electrode lead 20 passes through a through hole in the insulating plate 18 and extends toward the sealing body 17, and the negative electrode lead 21 passes outside the insulating plate 19 and extends toward the bottom side of the outer can 16. The positive electrode lead 20 is connected to the underside of an internal terminal plate 23 of the sealing body 17 by welding or the like, and a cap 27, which is the top plate of the sealing body 17 and is electrically connected to the internal terminal plate 23, serves as the positive electrode terminal. The negative electrode lead 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.

[0019] A gasket 28 is provided between the exterior can 16 and the sealing body 17 to ensure airtightness inside the battery. The exterior can 16 has a grooved portion 22 formed on its side surface that protrudes inward and supports the sealing body 17. The grooved portion 22 is preferably formed in an annular shape along the circumferential direction of the exterior can 16, and supports the sealing body 17 on its top surface. The sealing body 17 is fixed to the top of the exterior can 16 by the grooved portion 22 and the open end of the exterior can 16 that is crimped to the sealing body 17.

[0020] The sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal 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 one another. The lower valve body 24 and the upper valve body 26 are connected 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.

[0021] The positive electrode 11, the negative electrode 12, and the separator 13 that constitute the nonaqueous electrolyte secondary battery 10 will be described in detail below, with the positive electrode 11 being particularly described below.

[0022] [Positive Electrode] The positive electrode 11 has a positive electrode current collector and a positive electrode composite layer formed on both sides of the positive electrode current collector. The positive electrode current collector 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 the surface. The positive electrode composite layer contains a positive electrode active material, a conductive material, and a binder. The positive electrode 11 can be produced by applying a positive electrode slurry containing a positive electrode active material, a conductive material, a binder, etc. to the surface of the positive electrode current collector (application step), drying the coating (drying step), and rolling the coating to form a positive electrode composite layer on both sides of the positive electrode current collector (rolling step).

[0023] Examples of conductive materials contained in the positive electrode mixture layer include carbon materials such as carbon black, acetylene black, ketjen black, carbon nanotubes (CNT), graphene, and graphite. Examples of binders contained in the positive electrode mixture layer 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 a salt thereof, polyethylene oxide (PEO), or the like.

[0024] The positive electrode active material contained in the positive electrode mixture layer has a layered structure and includes a lithium transition metal composite oxide containing at least Ni and Mn.

[0025] The lithium transition metal composite oxide has the composition formula Li α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ (wherein X is at least one element selected from metal elements other than Li, Na, Ni, and Mn, and 0.80≦α≦1.20, 0≦β≦0.05, 0.80≦α+β≦1.20, 0.25<b≦0.65, 0≦c≦0.1, 0.4≦1−b−c<0.75, and d is a value satisfying the atomic valence.) This composite oxide has Li, Ni, and Mn as essential elements, and the proportion of Ni to the total number of moles of metal elements excluding Li and Na is 40 mol % or more and less than 75 mol %.

[0026] The above composition formula Liα Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ In the formula, the total molar ratio of Li and Na (α + β) is 0.80≦α + β≦1.20, preferably 0.9≦α + β≦1.15. The molar ratio of Ni (1-b-c) is 0.4≦1-b-c<0.75, preferably 0.4≦1-b-c≦0.7, more preferably 0.45≦1-b-c≦0.6, and even more preferably 0.45≦1-b-c≦0.55. The molar ratio of Mn (b) is 0.25<b≦0.65, preferably 0.3≦b≦0.6, more preferably 0.4≦b≦0.55, and even more preferably 0.45≦b≦0.55. If the molar ratios of Li, Ni, and Mn are within these ranges, it becomes easier to increase the charge / discharge capacity and improve the charge / discharge efficiency of the battery. The molar ratio of O (d) is a value that satisfies the atomic valence.

[0027] The above composition formula Li α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ In the above, the molar ratio of Na (β) is 0≦β≦0.05, preferably 0≦β≦0.035. The presence of a trace amount of Na stabilizes the layered structure of the composite oxide, making it easier to achieve a high battery capacity. Furthermore, if the molar ratio of Na exceeds 0.05, Na ions may be extracted from the positive electrode during charging and may be occluded by the negative electrode. This may result in a reaction with the non-aqueous electrolyte during charging and discharging to produce by-products, which may reduce the battery's charge / discharge capacity and charge / discharge efficiency.

[0028] The above composition formula Li α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄIn the formula, X is at least one element selected from metal elements other than Li, Na, Ni, and Mn. Furthermore, X is preferably at least one element selected from Mg, Ca, Sr, Ba, Sn, Ti, Si, V, Cr, Fe, Cu, Zn, Bi, Sb, B, Ga, In, P, Zr, Hf, Nb, Ta, Mo, W, Co, and Al, and more preferably Al, Co, Zr, or P. The molar ratio (c) of X is 0≦c≦0.1, preferably 0≦c≦0.05, and more preferably 0≦c≦0.03. By including X in the lithium transition metal composite oxide, it becomes easier to increase the capacity of the battery.

[0029] The positive electrode active material is mainly composed of a composite oxide represented by the above composition formula. Here, the term "main component" refers to the component with the highest mass ratio among the components of the composite oxide. The positive electrode active material in the mixture layer of the positive electrode 11 may contain a composite oxide other than the composite oxide represented by the above composition formula. However, the content of the composite oxide is preferably 50 mass% or more, and may be substantially 100 mass%. The composition of the composite oxide can be measured using an ICP optical emission spectrometer (e.g., iCAP6300 manufactured by Thermo Fisher Scientific).

[0030] The lithium transition metal composite oxide is, for example, a secondary particle formed by aggregation of a plurality of primary particles. The volume-based median diameter (D50) of the lithium transition metal composite oxide is, for example, 1 to 30 μm, or 3 to 20 μm. D50 is the particle size at which the volume integrated value is 50% in the particle size distribution measured by a laser diffraction scattering method. The BET specific surface area of ​​the lithium transition metal composite oxide is, for example, 0.1 to 10 m ２ / g, or 0.5 to 5m ２ If the BET specific surface area is within this range, it is easy to achieve a high capacity. The BET specific surface area is measured according to the BET method (nitrogen adsorption method) described in JIS R1626.

[0031] The lithium transition metal composite oxide has an integrated intensity I of the diffraction peak of the (110) plane in the X-ray diffraction pattern. １１０ The integrated intensity of the diffraction peak of the (108) plane I １０８Ratio I １０８ / I １１０ But, I １０８ / I １１０ <0.4. １０８ / I １１０ When I is smaller than 0.4, the amount of disorder in the layered rock salt structure of the lithium transition metal composite oxide decreases specifically. １０８ / I １１０ When the value of I is 0.4 or more, the amount of disorder in the layer structure of the lithium transition metal composite oxide increases. １０８ / I １１０ It is presumed that when I is 0.4 or more, the stability of the layered structure of the lithium transition metal composite oxide decreases. １０８ / I １１０ If is smaller than 0.4, the charge / discharge capacity and charge / discharge efficiency of the battery can be increased.

[0032] Here, the X-ray diffraction pattern can be obtained using a desktop X-ray diffractometer (manufactured by Rigaku Corporation, product name "MiniFlex600"). At this time, the diffracted X-rays are detected by a high-speed one-dimensional detector (D / teX Ultra 2). The measurement conditions for the X-ray diffractometer were as follows: CuKα radiation as the X-ray source, tube voltage of 40 kV, tube current of 15 mA, divergence slit (DS) of 0.625°, scattering slit (SS) of 13 mm (open), receiving slit (RS) of 8 mm, scan axis of 2θ / θ, continuous scanning, 2θ scan range of 10-80°, scan speed of 10° / min, and step width of 0.02°. The X-ray diffractometer and X-ray diffraction measurement conditions are not limited to those described above.

[0033] In the data obtained by the X-ray diffraction measurement, the scan angle 2θ is defined as x, and fitting is performed using a pseudo-Voigt function, which is equation (3) consisting of a linear sum of the Lorentz function shown in equation (1) and the Gaussian function shown in equation (2). By fitting, the peak height h, peak position u, standard deviation w, Lorentzian function component η, and Gaussian function component (1-η) are obtained. The product of the peak height h and standard deviation w obtained by fitting is taken as the integrated intensity, and the integrated intensity at each reflection index is calculated. Note that fitting using this pseudo-Voigt function can be achieved, for example, by using a computer (e.g., a personal computer) equipped with a CPU, ROM, RAM, HDD, and various interfaces. For example, the processing can be performed by installing the solver function of Microsoft's Excel or the nonlinear fit function of Lightstone's Origin on this computer. Alternatively, by installing dedicated software for performing the analysis (for example, the X-ray analysis integrated software SmartLab Studio II manufactured by Rigaku Corporation, or the "RIETAN-FP" program (F. Izumi and K. Momma, Solid State Phenom., 130, 15-20 (2007))), the above-mentioned processing can be performed by running this software. Note that the fitting processing is not limited to the above-mentioned method.

[0034] The lithium transition metal composite oxide has an integrated intensity I of the diffraction peak of the (104) plane in the X-ray diffraction pattern obtained by the X-ray diffraction. １０４ The integrated intensity I of the diffraction peak of the (003) plane ００３ Ratio I ００３ / I １０４ But, I ００３ / I １０４ It is preferable that the ratio is >1.0. ００３ / I １０４ If the value is 1.0 or less, the stability of the layered structure of the lithium transition metal composite oxide decreases, and the charge / discharge efficiency of the battery decreases.

[0035] The lithium transition metal composite oxide preferably has a half-width of the diffraction peak of the (108) plane and the (110) plane in the X-ray diffraction pattern obtained by the X-ray diffraction method of 0.2° or more and 0.8° or less. If the half-width is within the above range, the layered structure can be made to have a moderate distortion in the plane direction, thereby achieving a high battery capacity. If the half-width is less than 0.2°, the layered structure is very stable before charge and discharge, but after the charge process, the layered structure becomes unstable compared to those with a half-width in the above range, and after the discharge process, the layered structure becomes even more unstable, resulting in a decrease in charge and discharge capacity and charge and discharge efficiency. Furthermore, if the half-width is greater than 0.8°, the distortion of the layered structure is too large, making the layered structure brittle, and the charge and discharge capacity and charge and discharge efficiency decrease.

[0036] Next, the integrated intensity I of the diffraction peak １０８ / I １１０ A method for producing a lithium transition metal composite oxide (positive electrode active material) having a valence of less than 0.4 will be described.

[0037] A manufacturing process of a positive electrode active material, which is one example of an embodiment, includes: (1) a step of mixing and baking a sodium raw material, a nickel raw material, a manganese raw material, and a raw material of an additional element X to synthesize a sodium composite oxide; and (2) a step of reacting the sodium composite oxide with a lithium compound to ion-exchange at least a portion of Na in the sodium composite oxide with Li.

[0038] This method makes it possible to obtain a layered rock salt structure with a smaller amount of disorder than a method for synthesizing a lithium-containing composite oxide from a lithium raw material.

[0039] As the sodium source, at least one of sodium (metallic sodium) and a sodium compound is used. The sodium compound is not particularly limited as long as it contains sodium, and examples thereof include CH ３ COONa, CH ３ COONa 3H ２ Acetates such as O, NaNO ３ Nitrates, Na etc. ２ SO ４ Sulfates such as Na ２ CO ３Carbonates such as NaHCO ３ Hydrogen carbonates such as NaOH, hydroxides such as Na ２ O, Na ２ O ２ Among these, oxides of Na ２ CO ３ , NaHCO ３ , NaOH, NaNO ３ is preferred.

[0040] As the nickel raw material, at least one of nickel (metallic nickel) and a nickel compound is used. The nickel compound is not particularly limited as long as it contains nickel, and examples thereof include oxides such as NiO, NiOH, and Ni(OH). ２ , hydroxides such as NiOOH, NiNO ３ Nitrates such as NiCO ３ , Ni ４ CO ３ (OH) ６ (H ２ O) ４ Carbonates such as NiSO ４ Among these, particularly Ni(OH) ２ is preferred.

[0041] As the manganese raw material, at least one of manganese (metallic manganese) and a manganese compound is used. The manganese compound is not particularly limited as long as it contains manganese, and examples thereof include MnO, Mn ２ O ３ , Mn ３ O ４ , MnO ２ oxides such as Mn(OH) ２ , hydroxides such as MnOOH, MnCO ３ carbonates such as Mn(NO ３ ) ２ Nitrates such as MnSO ４ Among these, Mn(OH) ２ is preferred.

[0042] As with the nickel raw material and manganese raw material, at least one of X and a compound of X is used as the raw material of the additional element X. The compound is not particularly limited as long as it contains X, and examples thereof include oxides, hydroxides, carbonates, nitrates, and sulfates.

[0043] As the raw materials for nickel, manganese, and X, the above-mentioned compounds can be used, but it is also possible to use a compound containing nickel and manganese, a compound containing nickel, manganese, and X, a compound containing nickel and X, or a compound containing manganese and X.

[0044] The mixing ratio of these raw materials may be set appropriately. γ Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ (wherein 0.8≦γ≦1.20, 0.25<b≦0.65, 0≦c≦0.1, 0.4≦1−b−c<0.75, and d is a value satisfying the valence.) The method for mixing the raw materials is not particularly limited as long as it can mix them uniformly, and examples include mixing using a known mixer such as a mixer.

[0045] The mixture is fired in the air or in an oxygen stream. The firing temperature is preferably 600 to 1100°C, and more preferably 700 to 1000°C. The firing time is preferably 1 to 50 hours when the firing temperature is 600 to 900°C, and preferably 1 to 10 hours when the firing temperature is 900 to 1000°C. The cooling method is not particularly limited, and may be, for example, natural cooling (cooling in a furnace). After cooling, the fired product is pulverized by a known method to obtain a sodium composite oxide.

[0046] A suitable method for the ion-exchange step of Na in the sodium composite oxide with Li includes, for example, a method in which a molten salt bed of a lithium salt is added to the sodium composite transition metal oxide and heated. The lithium salt is preferably at least one selected from the group consisting of lithium nitrate, lithium sulfate, lithium chloride, lithium carbonate, lithium hydroxide, lithium iodide, and lithium bromide.

[0047] The heating temperature during the ion exchange process is preferably 200 to 400°C, more preferably 250 to 350°C. If the heating temperature exceeds 400°C, the reaction may proceed too rapidly, resulting in a non-uniform reaction. Furthermore, if the heating temperature is below 200°C, the reaction may not proceed sufficiently. The treatment time is preferably 1 to 50 hours, more preferably 2 to 20 hours, and even more preferably 2 to 10 hours. The cooling method is not particularly limited, and may be, for example, natural cooling (cooling in a furnace). After cooling, the obtained product is thoroughly washed with water, ethanol, methanol, or the like, and then dried to obtain a lithium transition metal composite oxide. The atmosphere during drying is preferably air or vacuum, and is not particularly limited. After washing, another heat treatment may be performed.

[0048] [Negative Electrode] The negative electrode 12 has a negative electrode current collector and a negative electrode composite layer formed on both sides of the negative electrode current collector. The negative electrode current collector can be a foil of a metal that is stable within the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with such a metal disposed on the surface layer. The negative electrode composite layer contains a negative electrode active material and a binder. The negative electrode 12 can be produced by applying a negative electrode composite slurry containing a negative electrode active material, a binder, etc. to the surface of the negative electrode current collector, drying the coating, and then rolling it to form a negative electrode composite layer on both sides of the negative electrode current collector.

[0049] The negative electrode active material contained in the negative electrode mixture layer is not particularly limited as long as it can reversibly absorb and release lithium ions, and generally, carbon materials such as graphite are used. 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, Sn, and lithium-titanium composite oxides may also be used as the negative electrode active material. Furthermore, those provided with a carbon coating may also be used. For example, SiO ｘ (0.5≦x≦1.6) or Li ２ｙ SiO （２＋ｙ） A Si-containing compound in which fine particles of Si are dispersed in a lithium silicate phase represented by (0<y<2) may be used in combination with graphite.

[0050] As in the case of the positive electrode 11, the binder contained in the negative electrode mixture layer may be a fluorine-containing resin such as PTFE or PVdF, PAN, polyimide, acrylic resin, or polyolefin, but is preferably styrene-butadiene rubber (SBR). The negative electrode mixture layer may also contain CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), or the like.

[0051] [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 13 include polyolefins such as polyethylene and polypropylene, and cellulose. The separator 13 may have a single-layer structure or a laminated structure. Furthermore, a highly heat-resistant resin layer such as an aramid resin, or a filler layer containing an inorganic compound filler may be provided on the surface of the separator 13.

[0052] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to these examples.

[0053] Example 1 Preparation of Positive Electrode Active Material A hydroxide containing Ni and Mn in a molar ratio of 1:1 was mixed with sodium carbonate in a molar ratio of Ni:Mn:Na=0.5:0.5:1.05, and the resulting mixture was heated at a temperature increase rate of 1°C / min, baked in air at 800°C for 24 hours, and then quenched in air to obtain a Na-containing composite oxide. Lithium nitrate and lithium chloride were then mixed to obtain LiNO ３A Li-containing molten salt was prepared by mixing the Li-containing molten salt and the above-mentioned Na-containing compound in a molar ratio of Li:Na=30:1. The resulting mixture was heated at a heating rate of 5°C / min, heated in air at 280°C for 5 hours, and cooled at a heating rate of 2°C / min to obtain a Li-Na mixture. The Li-Na mixture was washed with a sufficient amount of water and heated in vacuum at 160°C for 4 hours to obtain a lithium transition metal composite oxide. As described above, in Example 1, a lithium transition metal composite oxide was obtained by a production method including a step of synthesizing a sodium composite oxide according to the present disclosure and a step of ion-exchanging at least a portion of the Na in the sodium composite oxide with Li.

[0054] X-ray diffraction measurements were carried out on the lithium transition metal composite oxide of Example 1. An overall view of the X-ray diffraction results of the lithium transition metal composite oxide of Example 1 and a 60-70° enlarged view are shown in Figure 2. In addition, the integrated intensity I of the diffraction peak of the (110) plane in the X-ray diffraction pattern obtained by X-ray diffraction was １１０ The integrated intensity of the diffraction peak of the (108) plane I １０８ Ratio I １０８ / I １１０ The integrated intensity I of the diffraction peak of the (104) plane in the X-ray diffraction pattern was 0.39. １０４ The integrated intensity I of the diffraction peak of the (003) plane ００３ Ratio I ００３ / I １０４ The half widths of the diffraction peaks of the (108) and (110) planes in the X-ray diffraction pattern were 0.33° and 0.45°, respectively.

[0055] Furthermore, the amount of disorder was calculated from the results of Rietveld analysis of the X-ray diffraction pattern of the lithium transition metal composite oxide of Example 1. Specifically, the amount of disorder was calculated from the above X-ray diffraction pattern using SmartLab Studio II, an integrated X-ray analysis software manufactured by Rigaku Corporation. As a result, the amount of disorder of the lithium transition metal composite oxide of Example 1 was 5.0%.

[0056] [Fabrication of Positive Electrode] The positive electrode active material, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 92:5:3, and N-methyl-2-pyrrolidone (NMP) was used as a dispersion medium to prepare a positive electrode paste. This positive electrode paste was applied to an aluminum foil, the coating film was dried, and then the coating film was rolled with a rolling roller to prepare a positive electrode having a positive electrode composite layer formed on a positive electrode current collector.

[0057] [Preparation of Non-Aqueous Electrolyte] A mixed solvent of fluoroethylene carbonate (FEC) and methyl propionate (FMP) in a volume ratio of 1:3 was dissolved in lithium hexafluorophosphate (LiPF ６ ) was dissolved in the solution to a concentration of 1 mol / liter to prepare a non-aqueous electrolyte.

[0058] [Preparation of Test Cell] An electrode assembly in which the above-mentioned positive electrode and lithium metal as a negative electrode were stacked so as to face each other with a separator interposed therebetween, and the above-mentioned nonaqueous electrolyte solution were housed in a coin-shaped outer can, and the opening of the outer can was sealed with a gasket and a sealing member to prepare a test cell (nonaqueous electrolyte secondary battery).

[0059] [Evaluation of charge / discharge efficiency] The test cell was charged at a constant current of 0.2 C to 4.5 V at 25°C, and then charged at a constant voltage of 4.5 V until the current value reached 0.02 C. After a 20-minute break, the test cell was discharged at a constant current of 0.2 C to 2.5 V, and then the test cell was left for a 20-minute break. The charge / discharge efficiency was calculated from the charge capacity and discharge capacity measured in the above charge / discharge tests using the following formula: Charge / discharge efficiency (%) = discharge capacity / charge capacity × 100

[0060] Example 2 A test cell was prepared, and measurements and evaluations were carried out in the same manner as in Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, aluminum nitrate nonahydrate, and sodium carbonate were mixed in a molar ratio of Ni:Mn:Al:Na=0.4975:0.4975:0.005:1.05. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 2 are shown in FIG.

[0061] Example 3 A test cell was prepared, and measurements and evaluations were carried out in the same manner as in Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, aluminum nitrate nonahydrate, and sodium carbonate were mixed in a molar ratio of Ni:Mn:Al:Na=0.495:0.495:0.01:1.05. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 3 are shown in FIG.

[0062] Example 4 A test cell was prepared, and measurements and evaluations were carried out in the same manner as in Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, aluminum nitrate nonahydrate, and sodium carbonate were mixed in a molar ratio of Ni:Mn:Al:Na=0.4875:0.4875:0.025:1.05. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 4 are shown in FIG.

[0063] Example 5 A test cell was prepared, and measurements and evaluations were carried out in the same manner as in Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, cobalt nitrate hexahydrate, and sodium carbonate were mixed in a molar ratio of Ni:Mn:Co:Na=0.492:0.492:0.016:1.05. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 5 are shown in FIG.

[0064] Example 6 A test cell was prepared in the same manner as in Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, cobalt nitrate hexahydrate, and sodium carbonate were mixed in a molar ratio of Ni:Mn:Co:Na=0.4845:0.4845:0.031:1.05. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 6 are shown in FIG.

[0065] Example 7 A test cell was prepared, and measurements and evaluations were carried out in the same manner as in Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, zirconium oxide, and sodium carbonate were mixed in a molar ratio of Ni:Mn:Zr:Na=0.4975:0.4975:0.005:1.05. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 7 are shown in FIG.

[0066] Example 8 A test cell was prepared, and measurements and evaluations were carried out in the same manner as in Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, sodium phosphate, and sodium carbonate were mixed in a molar ratio of Ni:Mn:P:Na=0.4975:0.4975:0.005:1.05. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 8 are shown in FIG.

[0067] Example 9 A test cell was prepared, and measurements and evaluations were carried out in the same manner as in Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, sodium phosphate, and sodium carbonate were mixed in a molar ratio of Ni:Mn:P:Na=0.495:0.495:0.01:1.05. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 9 are shown in FIG.

[0068] Example 10 A test cell was prepared, and measurements and evaluations were carried out in the same manner as in Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 46:54 was mixed with sodium carbonate in a molar ratio of Ni:Mn:Na=0.46:0.54:1.05. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 10 are shown in FIG.

[0069] Example 11 A test cell was prepared, and measurements and evaluations were carried out in the same manner as in Example 1, except that in preparing the positive electrode active material, the Li-containing molten salt and the Na-containing compound were mixed in a molar ratio of Li:Na = 5: 1. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 11 are shown in Figure 12.

[0070] Example 12 A test cell was prepared, and measurements and evaluations were carried out in the same manner as in Example 1, except that in preparing a positive electrode active material, a Li-containing molten salt and a Na-containing compound were mixed in a molar ratio of Li:Na=5:1, and the resulting mixture was heated at a temperature increase rate of 5°C / min, heated at 350°C for 5 hours in air, and cooled at a temperature decrease rate of 2°C / min to obtain a Li-Na mixture. The results of X-ray diffraction of the lithium transition metal composite oxide of Example 12 are shown in Figure 13.

[0071] Comparative Example 1 In preparing a positive electrode active material, a hydroxide containing Ni and Mn in a 1:1 molar ratio and lithium hydroxide were mixed in a molar ratio of Ni:Mn:Li = 0.5:0.5:1.05. The resulting mixture was heated at a temperature increase rate of 5°C / min, calcined at 900°C for 10 hours in air, and then cooled at a temperature decrease rate of 10°C / min to obtain a lithium transition metal composite oxide. A test cell was prepared in the same manner as in Example 1, except for the preparation of the positive electrode active material, and measurements and evaluations were performed. The results of X-ray diffraction of the lithium transition metal composite oxide of Comparative Example 1 are shown in Figure 14.

[0072] Comparative Example 2 A test cell was prepared in the same manner as in Comparative Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, aluminum nitrate nonahydrate, and lithium hydroxide were mixed in a molar ratio of Ni:Mn:Al:Li = 0.4975:0.4975:0.005:1.05, and measurements and evaluations were carried out. The results of X-ray diffraction of the lithium transition metal composite oxide of Comparative Example 2 are shown in Figure 15.

[0073] Comparative Example 3 A test cell was prepared in the same manner as in Comparative Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, aluminum nitrate nonahydrate, and lithium hydroxide were mixed in a molar ratio of Ni:Mn:Al:Li = 0.492:0.492:0.016:1.05, and measurements and evaluations were carried out. The results of X-ray diffraction of the lithium transition metal composite oxide of Comparative Example 3 are shown in Figure 16.

[0074] Comparative Example 4 A test cell was prepared in the same manner as in Comparative Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, aluminum nitrate nonahydrate, and lithium hydroxide were mixed in a molar ratio of Ni:Mn:Al:Li = 0.4845:0.4845:0.031:1.05, and measurements and evaluations were carried out. The results of X-ray diffraction of the lithium transition metal composite oxide of Comparative Example 4 are shown in Figure 17.

[0075] Comparative Example 5 A test cell was prepared in the same manner as in Comparative Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1 and lithium hydroxide were mixed in a molar ratio of Ni:Mn:Li = 0.5:0.5:1.01. The results of X-ray diffraction of the lithium transition metal composite oxide of Comparative Example 5 are shown in Figure 18.

[0076] Comparative Example 6 A test cell was prepared in the same manner as in Comparative Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, cobalt nitrate hexahydrate, and lithium hydroxide were mixed in a molar ratio of Ni:Mn:Co:Li=0.4845:0.4845:0.031:1.01. The results of X-ray diffraction of the lithium transition metal composite oxide of Comparative Example 6 are shown in FIG.

[0077] Comparative Example 7 A test cell was prepared in the same manner as in Comparative Example 1, except that in preparing the positive electrode active material, a hydroxide containing Ni and Mn in a molar ratio of 1:1, cobalt nitrate hexahydrate, and lithium hydroxide were mixed in a molar ratio of Ni:Mn:Co:Li = 0.4685:0.4685:0.063:1.01. The results of X-ray diffraction of the lithium transition metal composite oxide of Comparative Example 7 are shown in Figure 20.

[0078] The charge capacity, discharge capacity, and charge / discharge efficiency of the examples and comparative examples are shown in Table 1. Table 1 also shows the proportion of metal elements and the integrated intensity I of the diffraction peak of the (110) plane in the X-ray diffraction pattern obtained by X-ray diffraction. １１０ The integrated intensity of the diffraction peak of the (108) plane I １０８ Ratio I １０８ / I １１０, the integrated intensity I of the diffraction peak of the (104) plane １０４ The integrated intensity I of the diffraction peak of the (003) plane ００３ Ratio I ００３ / I １０４ , the half-widths of the diffraction peaks of the (108) and (110) planes, and the amount of disorder are also shown.

[0079]

[0080] As shown in Table 1, the test cells of Examples 1 to 12 have higher charge capacity, discharge capacity, and charge / discharge efficiency than the test cells of Comparative Examples 1 to 7. Furthermore, Examples 2 to 4, in which Al was added in addition to Ni and Mn, Example 5, in which Co was added, and Examples 8 and 9, in which P was added, tend to have higher charge capacity, discharge capacity, and charge / discharge efficiency than Example 1, in which Al, Co, or P was not added. Furthermore, by changing the conditions for the step of ion-exchanging at least a portion of the Na in the sodium composite oxide with Li, the test cells of Examples 11 and 12 tend to have higher charge capacity, discharge capacity, and charge / discharge efficiency than the test cell of Example 1.

[0081] SEM images of the lithium transition metal composite oxides prepared in Example 1 and Comparative Example 1 are shown in Figures 21 and 22. Note that all SEM images were taken at a magnification of 5000x. As shown in Figures 21 and 22, the lithium transition metal composite oxides prepared in Example 1 and Comparative Example 1 were both composed of particles with a substantially spherical shape. Furthermore, the SEM images confirmed that the lithium transition metal composite oxide of Example 1 had finer primary particles than the lithium transition metal composite oxide of the Comparative Example.

[0082] The present disclosure is further illustrated by the following embodiments: Structure 1: Composition formula Li α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ(wherein X is at least one element selected from metal elements other than Li, Na, Ni, and Mn, and 0.80≦α≦1.2, 0≦β≦0.05, 0.80≦α+β≦1.20, 0.25<b≦0.65, 0≦c≦0.1, 0.4≦1−b−c<0.75, and d is a value satisfying the atomic valence), and the integrated intensity I of the diffraction peak of the (110) plane in the X-ray diffraction pattern obtained by powder X-ray diffraction of the lithium transition metal composite oxide １１０ The integrated intensity of the diffraction peak of the (108) plane I １０８ Ratio I １０８ / I １１０ But, I １０８ / I １１０ <0.4. α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ In the formula (1), X is at least one element selected from Mg, Ca, Sr, Ba, Sn, Ti, Si, V, Cr, Fe, Cu, Zn, Bi, Sb, B, Ga, In, P, Zr, Hf, Nb, Ta, Mo, W, Co, and Al. α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ In the positive electrode active material for a non-aqueous electrolyte secondary battery according to configuration 1 or 2, X is Al, Co, Zr, or P. Configuration 4: The integrated intensity I of the diffraction peak of the (104) plane in the X-ray diffraction pattern １０４ The integrated intensity I of the diffraction peak of the (003) plane ００３ Ratio I ００３ / I １０４ But, I ００３ / I １０４ 1.0>1.0. Aspect 5: The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of Aspects 1 to 4, wherein the half widths of the diffraction peaks of the (108) plane and the (110) plane in the X-ray diffraction pattern are 0.2° or more and 0.8° or less. Aspect 6: The positive electrode active material for a non-aqueous electrolyte secondary battery according to Aspects 1 to 4, wherein the half widths of the diffraction peaks of the (108) plane and the (110) plane in the X-ray diffraction pattern are 0.2° or more and 0.8° or less.α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of configurations 1 to 5, wherein the molar ratio (y) of Na is 0≦y≦0.035. γ Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ (wherein X is at least one element selected from metal elements other than Li, Na, Ni, and Mn, and d is a value satisfying the following conditions: 0.8≦γ≦1.20, 0.25<b≦0.65, 0≦c≦0.1, 0.4≦1−b−c<0.75, and d is a value satisfying the valence), and reacting the sodium composite oxide with a lithium compound to ion-exchange at least a portion of the Na in the sodium composite oxide with Li. Configuration 8: A non-aqueous electrolyte secondary battery comprising: a positive electrode containing the positive electrode active material according to any one of Configurations 1 to 6, a negative electrode, and a non-aqueous electrolyte.

[0083] REFERENCE SIGNS LIST 10 Non-aqueous electrolyte secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Outer can, 17 Sealing body, 18, 19 Insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 22 Grooved portion, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket

Claims

1. Composition formula Li α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ (wherein X is at least one element selected from metal elements other than Li, Na, Ni, and Mn, and 0.80≦α≦1.20, 0≦β≦0.05, 0.80≦α+β≦1.20, 0.25<b≦0.65, 0≦c≦0.1, 0.4≦1−b−c<0.75, and d is a value satisfying the atomic valence), The integrated intensity I of the diffraction peak of the (110) plane of the X-ray diffraction pattern obtained by powder X-ray diffraction of the lithium transition metal composite oxide １１０ The integrated intensity of the diffraction peak of the (108) plane I １０８ Ratio I １０８ / I １１０ But, I １０８ / I １１０ <0.

4.

2. Composition formula Li α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ 2. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1, wherein X is at least one element selected from Mg, Ca, Sr, Ba, Sn, Ti, Si, V, Cr, Fe, Cu, Zn, Bi, Sb, B, Ga, In, P, Zr, Hf, Nb, Ta, Mo, W, Co, and Al.

3. Composition formula Li α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein X is Al, Co, Zr or P.

4. The integrated intensity I of the diffraction peak of the (104) plane in the X-ray diffraction pattern １０４ The integrated intensity I of the diffraction peak of the (003) plane ００３ Ratio I ００３ / I １０４ But, I ００３ / I １０４ The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the positive electrode active material for a non-aqueous electrolyte secondary battery has a molecular weight of 1.0 or more.

5. 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the half-value widths of the diffraction peaks of the (108) and (110) planes in the X-ray diffraction pattern are 0.2° or more and 0.8° or less.

6. Composition formula Li α Na β Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the molar ratio (β) of Na is 0≦β≦0.

035.

7. Composition formula Na γ Ni １－ｂ－ｃ Mn ｂ X ｃ O ｄ (wherein X is at least one element selected from metal elements other than Li, Na, Ni, and Mn, and d is a value satisfying 0.80≦γ≦1.20, 0.25<b≦0.65, 0≦c≦0.1, 0.4≦1−b−c<0.75, and d is a value satisfying the atomic valence); a step of reacting the sodium composite oxide with a lithium compound to ion-exchange at least a portion of Na in the sodium composite oxide with Li; The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery includes the steps of:

8. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 6; A negative electrode; A non-aqueous electrolyte; A non-aqueous electrolyte secondary battery comprising: