Positive electrode active material for lithium ion batteries, positive electrode material, positive electrode, solid-state battery, and method for producing positive electrode active material for lithium ion batteries

Abstract

To provide a positive electrode active material for a lithium-ion battery, positive electrode material, positive electrode layer, and solid-state battery that can produce a battery with a large discharge capacity in a potential range including a high potential range and excellent rapid discharge performance, a positive electrode active material for a sodium-ion battery, and a manufacturing method for a positive electrode active material for a lithium-ion battery.SOLUTION: There are provided positive electrode active material, positive electrode material, positive electrode layer, and solid-state battery for a lithium-ion battery having a core portion having an O3-type crystal structure and a shell portion covering the core portion and having at least one crystal structure selected from the group consisting of an O2-type structure, a T#2-type structure, and an O6-type structure, a positive electrode active material for a sodium-ion battery, and a manufacturing method for a positive electrode material for a lithium-ion battery.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a cathode active material for a lithium - ion battery, a cathode material, a cathode, a solid - state battery, a cathode active material for a sodium - ion battery, and a method for manufacturing a cathode active material for a lithium - ion battery. relates to.

Background Art

[0002] A cathode active material having at least one crystal structure selected from the group consisting of an O2 - type structure, a T#2 - type structure, and an O6 - type structure is stable up to a high potential, and thus has a large charge - discharge capacity in the charge - discharge of a potential region including a high - potential region. Patent Document 1 proposes "a cathode active material used in a non - aqueous electrolyte secondary battery, which has a layered structure and contains a lithium - containing transition metal oxide in which the main arrangement of transition metal, oxygen, and lithium is represented by an O2 structure, and the lithium - containing transition metal oxide has Li, Mn, and element M in the lithium - containing transition metal layer in the layered structure, and has a general composition formula Li x [Li α (Mn a M b ) 1-α O2, where 0.5 < x < 1.1, 0.1 < α < 0.33, 0.67 < a < 0.97, 0.03 < b < 0.33, and M contains at least one element selected from the group consisting of Ni, Mg, Ti, Fe, Sn, Zr, Nb, Mo, W, and Bi, which is a cathode active material for a non - aqueous electrolyte secondary battery." Also, Patent Document 2 proposes "a lithium - containing layered oxide Li a N ab M c O 2±αThe proposed positive electrode active material is characterized in that, in the following range, the potential P (V) of (0.5≦a≦1.3, 0≦b≦0.01, 0.90≦c≦1.10, 0≦α≦0.3, M=at least one element selected from manganese, cobalt, nickel, iron, aluminum, molybdenum, zirconium, and magnesium) is 4.8≦P≦5.0 (vs. Li / Li+), the molar ratios of lithium and M are a and c, respectively, and when c is converted to 1.0, the ratio of a is in the range of 0.08≦a≦0.12. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-186937 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-92824 Summary of the Invention [Problem to be solved by the invention]

[0004] Positive electrode active materials having at least one crystal structure selected from the group consisting of an O2 type structure, a T#2 type structure, and an O6 type structure tend to have poor rapid charge / discharge performance due to the slow internal diffusion rate of lithium ions. In recent years, there has been a demand for improved rapid charge-discharge performance, and there is a need for the development of a positive electrode active material for lithium-ion batteries that has at least one crystal structure selected from the group consisting of an O2-type structure, a T#2-type structure, and an O6-type structure, and that can provide batteries with excellent rapid charge-discharge performance and large discharge capacity in a potential range including a high potential range.

[0005] Therefore, an object of one embodiment of the present disclosure is to provide a positive electrode active material for a lithium ion battery that can provide a battery having excellent rapid charge and discharge performance and a large discharge capacity in a potential range including a high potential range. Another problem to be solved by another embodiment of the present disclosure is to provide a positive electrode material that can provide a battery having excellent rapid charge and discharge performance and a large discharge capacity in a potential region including a high potential region. Another problem to be solved by another embodiment of the present disclosure is to provide a positive electrode that can provide a battery that has excellent rapid charge and discharge performance and a large discharge capacity in a potential region including a high potential region. Another problem to be solved by another embodiment of the present disclosure is to provide a solid-state battery that has excellent rapid charge and discharge performance and a large discharge capacity in a potential range including a high potential range. Another embodiment of the present disclosure aims to solve a problem by providing a positive electrode active material for a sodium ion battery, which can provide a battery having excellent rapid charge and discharge performance and a large discharge capacity in a potential range including a high potential range. Another embodiment of the present disclosure aims to solve a problem by providing a method for producing a positive electrode active material for a lithium ion battery, which can provide a battery that has excellent rapid charge and discharge performance and a large discharge capacity in a potential range including a high potential range.

[0006] The "potential region including the high potential region" refers to a region of 2.0V or more and 4.8V or less. [Means for solving the problem]

[0007] The means for solving the above problems include the following means. <1> a core portion having an O3-type crystal structure; a shell portion covering the core portion and having at least one crystal structure selected from the group consisting of an O2 type structure, a T#2 type structure, and an O6 type structure. <2> The diameter R1 of the core portion and the diameter R2 of the positive electrode active material for a lithium ion battery satisfy the following formula A and the following formula B: <1> The positive electrode active material for a lithium ion battery according to claim 1. Formula A: (R2-R1) / 2≧10nm Formula B: (R2-R1) / R2≧0.01 <3> <1> or <2> A positive electrode material comprising the positive electrode active material for a lithium ion battery according to claim 1. <4> <3> A positive electrode comprising the positive electrode material described in <5> <1> or <2> A solid-state battery comprising the positive electrode active material for a lithium ion battery according to claim 1. <6> a core portion having an O3-type crystal structure; A positive electrode active material for a sodium ion battery, comprising: a shell portion that covers the core portion and has a P2 type crystal structure. <7> A method for producing a positive electrode active material for a lithium-ion battery, comprising the steps of heating a sodium-containing transition metal oxide having an O3-type crystal structure to 800°C or higher and maintaining the temperature at that temperature for a time t that satisfies the following formula C: Formula C: 0.04×t / r2<0.1 (In formula C, t is time in minutes. In formula C, r2 is the median diameter R2 of the resulting positive electrode active material for lithium-ion batteries in nm.) <8> The temperature increase and maintenance are carried out by laser irradiation. <7> A method for producing the positive electrode active material for a lithium ion battery according to claim 1. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, there is provided a positive electrode active material for a lithium ion battery that can provide a battery with excellent rapid charge and discharge performance and large discharge capacity in a potential range including a high potential range. According to another embodiment of the present disclosure, there is provided a positive electrode material that can provide a battery having excellent rapid charge and discharge performance and a large discharge capacity in a potential region including a high potential region. According to another embodiment of the present disclosure, there is provided a positive electrode that can provide a battery that has excellent rapid charge and discharge performance and a large discharge capacity in a potential region including a high potential region. According to another embodiment of the present disclosure, there is provided a solid-state battery that has excellent rapid charge and discharge performance and a large discharge capacity in a potential range including a high potential range. According to another embodiment of the present disclosure, there is provided a positive electrode active material for a sodium ion battery that can provide a battery that has excellent rapid charge and discharge performance and a large discharge capacity in a potential range including a high potential range. According to another embodiment of the present disclosure, there is provided a method for producing a positive electrode active material for a lithium ion battery, which enables the production of a battery having excellent rapid charge and discharge performance and a large discharge capacity in a potential range including a high potential range. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a solid-state battery. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0011] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified. The term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved.

[0012] <Positive electrode active material for lithium-ion batteries> The positive electrode active material for a lithium ion battery according to the present disclosure has a core portion having an O3-type crystalline structure, and a shell portion covering the core portion and having at least one crystalline structure selected from the group consisting of an O2-type structure, a T#2-type structure, and an O6-type structure.

[0013] The positive electrode active material for a lithium ion battery according to the present disclosure has the above-described configuration, and is capable of providing a battery having excellent rapid charge / discharge performance and a large discharge capacity in a potential range including a high potential range. The reason for this is presumed to be as follows.

[0014] The positive electrode active material for a lithium ion battery according to the present disclosure has a shell portion having at least one crystal structure selected from the group consisting of an O2-type structure, a T#2-type structure, and an O6-type structure, and therefore has a large discharge and charge capacity in a potential range including a high potential range. The positive electrode active material for a lithium-ion battery according to the present disclosure has a core portion having an O3-type crystal structure, which is advantageous for improving rapid charge / discharge performance due to the fast internal diffusion rate of lithium ions.

[0015] From the above, it is presumed that the positive electrode active material for a lithium ion battery according to the present disclosure will be a positive electrode active material for a lithium ion battery that can provide a battery having excellent rapid charge and discharge performance and a large discharge capacity in a potential range including a high potential range.

[0016] (Core part) The core has an O3-type crystal structure. Here, the O3-type crystal structure refers to a crystal structure that belongs to the space group R-3m, in which lithium and a transition metal are present at the center of an oxygen octahedron, and in which there are three types of overlapping patterns between oxygen and transition metal oxide per unit cell. A crystal structure in which six oxygen layers, three Li layers, and three transition metal layers form one period is preferred.

[0017] (shell part) The shell portion covers the core portion and has at least one crystal structure selected from the group consisting of an O2 type structure, a T#2 type structure, and an O6 type structure. Here, the O2-type crystal structure refers to a crystal structure that belongs to the space group P63mc, in which lithium and a transition metal are present at the center of an oxygen octahedron, and there are two types of overlapping of the oxygen and the transition metal per unit cell. A crystal structure in which one period consists of four oxygen layers, two Li layers, and two transition metal layers is preferred. The T#2 type crystal structure is a crystal structure that belongs to the space group Cmca, in which lithium is present at the center of an oxygen tetrahedron, a transition metal is present at the center of an oxygen octahedron, and there are two types of overlapping of the oxygen and transition metal per unit cell. A crystal structure in which one period consists of four oxygen layers, two Li layers, and two transition metal layers is preferred. The O6-type crystal structure is a crystal structure that belongs to the space group R-3m, in which lithium and a transition metal are present at the center of an oxygen octahedron, and there are six different ways in which oxygen and the transition metal overlap per unit cell. A crystal structure that forms one period with an O12 layer, an Me6 layer, and a Li6 layer is preferred.

[0018] (Composition formula of positive electrode active material for lithium-ion batteries) In the positive electrode active material for a lithium ion battery according to the present disclosure, the core and shell may have different compositions or may be the same. From the viewpoints of rapid charge / discharge performance and discharge capacity, it is preferable that the core and shell have the same composition.

[0019] From the viewpoint of rapid charge / discharge performance and discharge capacity, the positive electrode active material for a lithium ion battery according to the present disclosure is preferably a compound represented by the following formula 1. Formula 1: Li a Na b Mn x-p Ni y-q Co z-r M p+q+r O2 In the above formula 1, a, b, x, y, z, p, q, and r are numbers that satisfy 0≦a≦1 (preferably 0.6≦a≦1), 0≦b≦0.05 (preferably 0≦b≦0.01), and x+y+z=1 and 0≦p+q+r≦0.20 (preferably 0≦p+q+r≦0.10), and M represents at least one element selected from the group consisting of B, Mg, Al, K, Ca, Ti, Cr, Ga, Zr, Nb, Mo, and W. M preferably represents at least one selected from the group consisting of B, Mg, Al, K, Ca, Ti, Cr, Ga, Zr, Nb, Mo and W, and more preferably represents Al.

[0020] x is preferably a number that satisfies 0≦x≦1, and more preferably a number that satisfies 0.1≦x≦1. y is preferably a number that satisfies 0≦y≦0.5, and more preferably a number that satisfies 0≦y≦0.33. It is preferable that z is a number that satisfies 0≦z≦1, and it is more preferable that z is a number that satisfies 0≦z≦0.67. It is preferable that p is a number that satisfies 0≦p≦0.10. It is preferable that q is a number that satisfies 0≦q≦0.10. It is preferable that r is a number that satisfies 0≦r≦0.10.

[0021] The composition formula of the positive electrode active material for a lithium ion battery according to the present disclosure is specifically Li 0.70 Na 0.00 Mn 0.50 Ni 0.20 Co 0.30 O2, Li 0.60 Na 0.00 Mn 0.50 Ni 0.20 Co 0.30 O2, Li 1.0 Na 0.00 Mn 0.50 Ni 0.20 Co 0.30 O2, Li 0.70 Na 0.05 Mn 0.50 Ni 0.20 Co 0.30 O2, Li 0.7 Na 0.00 Mn 0.67 Ni 0.33 O2, Li 0.70 Na 0.00 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10 Examples include O2.

[0022] (Diameter R1 of the core and diameter R2 of the positive electrode active material for lithium-ion batteries) From the viewpoint of rapid charge / discharge performance and discharge capacity, in the positive electrode active material for a lithium ion battery according to the present disclosure, the diameter R1 of the core portion and the diameter R2 of the positive electrode active material for a lithium ion battery preferably satisfy the following formula A and formula B, more preferably satisfy the following formula A2 and formula B2, and further preferably satisfy the following formula A3 and formula B3. Formula A: (R2-R1) / 2≧10nm Formula B: (R2-R1) / R2≧0.01

[0023] Formula A2:(R2-R1) / 2≧30nm Formula B2:(R2-R1) / R2≧0.05

[0024] Formula A3:(R2-R1) / 2≧40nm Formula B3:(R2-R1) / R2≧0.06

[0025] Measurement procedure for the diameter R1 of the core and the diameter R2 of the positive electrode active material for lithium-ion batteries The diameter R1 of the core portion and the diameter R2 of the positive electrode active material for a lithium ion battery are measured using a transmission electron microscope. The measurement procedure is described below. Using a transmission electron microscope, a lithium-ion battery cathode active material was observed by annular bright-field scanning transmission electron microscopy (ABF-STEM) under conditions of an acceleration voltage of 200 kV or higher and a resolution of 0.2 nm or lower. The interface between a region where a consistent structure is observed in the space group P63mc and a region where a consistent structure is observed in the space group R-3m was defined as the interface between the core and shell (hereinafter, this interface is referred to as the "core-shell interface"). If there was a region between the region where a consistent structure is observed in the space group P63mc and the region where a consistent structure is observed in the space group R-3m, the midpoint of the region was defined as the core-shell interface. The longest distance from one core-shell interface to another within the region where a consistent structure is observed in the space group P63mc is defined as the diameter R1 of the core. Furthermore, the longest distance of a line segment connecting any two points within a region where a consistent structure is observed as space group R-3m is defined as the diameter R2 of the positive electrode active material for a lithium ion battery.

[0026] Here, the measurement directions for the diameter R1 of the core portion and the diameter R2 of the positive electrode active material for a lithium ion battery are determined as follows. Planes perpendicular to the crystal lattice (001) (e.g. <100> , <010> , <110> For each of the surfaces, the measurement direction is determined so that the diameter R2 of the positive electrode active material for a lithium ion battery measured in the direction perpendicular to each surface using the above procedure is maximized. Also, the diameter R1 of the core portion is measured using the above procedure so that the axis of the diameter R2 of the positive electrode active material for a lithium ion battery is shared. In the direction parallel to (001), it is sufficient that (diameter R2 of positive electrode active material for lithium ion batteries - diameter R1 of core portion)>0.

[0027] From the viewpoint of rapid charge / discharge performance and discharge capacity, the diameter R1 of the core portion is preferably 10 nm or more and 3000 nm or less, more preferably 20 nm or more and 2000 nm or less, and even more preferably 20 nm or more and 1000 nm or less. From the viewpoint of rapid charge / discharge performance and discharge capacity, the diameter R2 of the positive electrode active material for a lithium ion battery is preferably 30 nm or more and 3600 nm or less, more preferably 40 nm or more and 2400 nm or less, and even more preferably 40 nm or more and 1200 nm or less.

[0028] <Method of manufacturing positive electrode active material for lithium-ion batteries> The method for producing a positive electrode active material for a lithium ion battery according to the present disclosure includes a step of heating a Na-containing transition metal oxide having an O3-type crystal structure to 800°C or higher and maintaining the temperature after heating for a time t that satisfies the following formula C (shell formation step). Formula C: 0.04×t / r2<0.1 In formula C, t is time in minutes, and r2 is the median diameter R2 of the resulting positive electrode active material for lithium ion batteries in nm.

[0029] (Na-containing transition metal oxide production process) The method for producing a positive electrode active material for a lithium ion battery according to the present disclosure preferably includes, before the shell formation step, a step of producing a Na-containing transition metal oxide having an O3-type crystal structure (Na-containing transition metal oxide production step). Specific examples of the Na-containing transition metal oxides having an O3-type crystal structure include Na 0.75 Mn 0.5 Ni 0.2 Co 0.3 O2, Na 0.65 Mn 0.5 Ni 0.2 Co 0.3 O2, Na 0.75 Mn 0.67 Ni 0.33 O2, Na 0.75 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10 O2, Na 0.75 Mn 0.40 Ni 0.20 Co 0.30 Cr 0.10 O2, Na 0.75 Mn 0.50 Ni 0.10 Co 0.30 Mg 0.20 Examples include O2.

[0030] The sodium-containing transition metal oxide having an O3-type crystal structure is preferably obtained by using salts containing the constituent metals as raw materials, mixing these salts and causing a reaction. Examples of the salt include sodium-containing carbonates, manganese-containing nitrates, nickel-containing nitrates, cobalt-containing nitrates, manganese-containing sulfates, nickel-containing sulfates, cobalt-containing sulfates, manganese-containing oxalates, nickel-containing oxalates, cobalt-containing oxalates, sodium-containing hydroxides, and sodium-containing hydrogen carbonates.

[0031] (Shell forming process) The shell formation process is a process in which a Na-containing transition metal oxide having an O3-type crystal structure is heated to 800°C or higher and held at the temperature after heating (hereinafter, this temperature is referred to as the "holding temperature") for a time t that satisfies the following formula C. Formula C: 0.04×t / r2<0.1 In formula C, t is time in minutes, and r2 is the median diameter R2 of the resulting positive electrode active material for lithium ion batteries in nm.

[0032] This process produces a Na-containing transition metal oxide having a core portion with an O3-type crystalline structure and a shell portion covering the core portion and having a P2-type crystalline structure (hereinafter, this Na-containing transition metal oxide is also referred to as a "Na-doped precursor").

[0033] In formula C, r2 is the median value of the diameter R2 of the positive electrode active material for a lithium ion battery obtained by the method for producing a positive electrode active material for a lithium ion battery according to the present disclosure. The median diameter R2 refers to the n / 2th R2 value when the R2 values ​​measured for n particles are sorted in ascending order. However, if n is an even number, it refers to the average of the (n-1) / 2th and (n+1) / 2nd R2 values.

[0034] The temperature rise rate of the Na-containing transition metal oxide having an O3-type crystal structure is preferably 50°C / min or more and 200°C / min or less, more preferably 80°C / min or more and 150°C / min or less, and even more preferably 90°C / min or more and 110°C / min or less.

[0035] The holding temperature is preferably 800°C or higher and 1100°C or lower, more preferably 850°C or higher and 1050°C or lower, and even more preferably 900°C or higher and 1000°C or lower. The time (holding time) t at the holding temperature is preferably 2 minutes or more and 10 minutes or less, more preferably 3 minutes or more and 8 minutes or less, and even more preferably 4 minutes or more and 6 minutes or less.

[0036] After being held at the holding temperature, the Na-doped precursor is preferably cooled at a cooling rate of preferably 50°C / min to 200°C / min, more preferably 80°C / min to 150°C / min, and even more preferably 90°C / min to 110°C / min.

[0037] Here, the temperatures of the Na-containing transition metal oxide having an O3-type crystal structure and the Na-doped precursor in this step are measured using a thermometer. As the thermometer, for example, a platinum-Rh-based R-type thermocouple connected to a temperature indicator SK-EM-01 manufactured by Sato Keiryoki Seisakusho Co., Ltd. can be used.

[0038] The shell formation process is not particularly limited as long as it can heat a Na-containing transition metal oxide having an O3-type crystal structure under the above conditions, but it is preferably carried out by laser irradiation from the viewpoint of easily forming the shell portion. When laser irradiation is used, it is preferable to heat the Na-containing transition metal oxide having an O3-type crystal structure by irradiating the Na-containing transition metal oxide having an O3-type crystal structure with a laser from a laser irradiator.

[0039] The wavelength of the irradiated laser light can be in the range of 300 nm to 1000 nm. The laser irradiator can be appropriately selected as long as it is an irradiator equipped with a semiconductor laser light source, and for example, a product name manufactured by ExLASER, manufactured by Sakaguchi Electric Heating Co., Ltd., can be used.

[0040] (Ion exchange process) The method for producing a positive electrode active material for a lithium ion battery according to the present disclosure preferably includes a step of ion-exchanging Na contained in the Na-doped precursor with Li. Ion exchange of the Na-doped precursor can be performed using a molten salt bed containing a mixture of lithium nitrate and lithium chloride. The temperature conditions during ion exchange are preferably in the range of not less than the temperature at which the molten salt bed melts but less than 320°C.

[0041] <Cathode active material for sodium ion batteries> The positive electrode active material for a sodium ion battery according to the present disclosure has a core portion having an O3-type crystalline structure and a shell portion covering the core portion and having a P2-type crystalline structure. Here, the positive electrode active material for a sodium ion battery according to the present disclosure can be used as a Na-doped precursor in the method for producing a positive electrode active material for a lithium ion battery according to the present disclosure.

[0042] The positive electrode active material for a sodium ion battery according to the present disclosure is preferably produced through the Na-containing transition metal oxide production step and the shell formation step in the above-described method for producing a positive electrode active material for a lithium ion battery.

[0043] The core and shell portions of the positive electrode active material for a sodium ion battery are distinguished using a transmission electron microscope. The method for distinguishing between the core and shell portions is described below. Using a transmission electron microscope, a lithium-ion battery cathode active material is observed by annular bright-field scanning transmission electron microscopy (ABF-STEM) under conditions of an acceleration voltage of 200 kV or higher and a resolution of 0.2 nm or lower. The interface between a region where a consistent structure is observed in the space group P63 / mmc and a region where a consistent structure is observed in the space group R-3m is defined as the interface between the core and shell (hereinafter, this interface is referred to as the "core-shell interface"). If there is a region between the region where a consistent structure is observed in the space group P63 / mmc and the region where a consistent structure is observed in the space group R-3m, the midpoint of the region is defined as the core-shell interface.

[0044] Specific examples of the positive electrode active material for a sodium ion battery according to the present disclosure include Na 0.75 Mn 0.5 Ni 0.2 Co 0.3 O2, Na 0.65 Mn 0.5 Ni 0.2 Co 0.3 O2, Na 0.75 Mn0.67 Ni 0.33 O2, Na 0.75 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10 O2, Na 0.75 Mn 0.40 Ni 0.20 Co 0.30 Cr 0.10 O2, Na 0.75 Mn 0.50 Ni 0.10 Co 0.30 Mg 0.20 Examples include O2.

[0045] The positive electrode material according to the present disclosure contains a positive electrode active material for lithium ion batteries, and may contain a conductive additive, a solid electrolyte, a binder, and other components as needed.

[0046] (Positive electrode active material for lithium-ion batteries) The positive electrode active material for lithium ion batteries contained in the positive electrode material according to the present disclosure is the positive electrode active material for lithium ion batteries according to the present disclosure, and preferred aspects are also the same.

[0047] The positive electrode active material for lithium ion batteries contained in the positive electrode material according to the present disclosure may contain a positive electrode active material for lithium ion batteries other than the positive electrode active material for lithium ion batteries according to the present disclosure. Another positive electrode active material for a lithium ion battery preferably contains a lithium composite oxide. The lithium composite oxide may contain at least one element selected from the group consisting of F, Cl, N, S, Br, and I. The lithium composite oxide may have a crystal structure belonging to at least one space group selected from the space groups R-3m, Immm, and P63-mmc (also referred to as P63mc or P6 / mmc). The lithium composite oxide may have an O2-type structure in which the transition metal, oxygen, and lithium are primarily arranged.

[0048] Examples of lithium composite oxides having a crystal structure belonging to R-3m include Li x Me y O αX β (Me represents at least one selected from the group consisting of Mn, Co, Ni, Fe, Al, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, B, Si, and P, and X represents at least one selected from the group consisting of F, Cl, N, S, Br, and I, and satisfy the conditions 0.5≦x≦1.5, 0.5≦y≦1.0, 1≦α<2, and 0<β≦1.)

[0049] Examples of lithium composite oxides having a crystal structure belonging to Immm include Li x1 M 1 A 1 2(1.5≦x1≦2.3, M 1 contains at least one selected from the group consisting of Ni, Co, Mn, Cu and Fe, and A 1 contains at least oxygen, and A 1 The ratio of oxygen in the oxide is 85 atomic % or more. x1 M 1A 1-x2 M 1B x2 O 2-y A 2 y (0≦x2≦0.5, 0≦y≦0.3, and at least one of x2 and y is not 0, M 1A represents at least one selected from the group consisting of Ni, Co, Mn, Cu, and Fe, and M 1B represents at least one selected from the group consisting of Al, Mg, Sc, Ti, Cr, V, Zn, Ga, Zr, Mo, Nb, Ta and W, and A2 represents at least one selected from the group consisting of F, Cl, Br, S and P.

[0050] Examples of lithium composite oxides having a crystal structure belonging to P63-mmc include M1 x M2 yComposite oxides represented by O2 (where M1 represents an alkali metal (preferably at least one of Na and K), M2 represents a transition metal (preferably at least one selected from the group consisting of Mn, Ni, Co, and Fe), and x + y satisfies 0 < x + y ≤ 2).

[0051] As the lithium composite oxide having a crystal structure of the O2 type, for example, Li x [Li α (Mn a Co b M c ) 1-α O2 (where 0.5 < x < 1.1, 0.1 < α < 0.33, 0.17 < a < 0.93, 0.03 < b < 0.50, 0.04 < c < 0.33, and M represents at least one selected from the group consisting of Ni, Mg, Ti, Fe, Sn, Zr, Nb, Mo, W, and Bi). Examples of such composite oxides include Li 0.744 [Li 0.145 Mn 0.625 Co 0.115 Ni 0.115 O2 and the like.

[0052] A more preferred embodiment is that at least a part of the surface of other cathode active materials is coated with a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte. As the halide solid electrolyte for coating at least a part of the surface of the cathode active material, Li 6-(4-x)b (Ti 1-x Al x ) b F6 (where 0 < x < 1, 0 < b ≤ 1.5) [LTAF electrolyte] is preferred.

[0053] (Conductive aid) Examples of the conductive aid include carbon materials, metal materials, and conductive polymer materials. Examples of the carbon materials include carbon black (e.g., acetylene black, furnace black, ketjen black, etc.), fibrous carbon (e.g., vapor-grown carbon fiber, carbon nanotube, carbon nanofiber, etc.), graphite, carbon fluoride, etc. Examples of the metal materials include metal powder (e.g., aluminum powder, etc.), conductive whisker (e.g., zinc oxide, potassium titanate, etc.), conductive metal oxide (e.g., titanium oxide, etc.), etc. Examples of the conductive polymer materials include polyaniline, polypyrrole, polythiophene, etc. The conductive aid may be used alone as only one type, or two or more types may be mixed and used.

[0054] (Solid electrolyte) As the solid electrolyte, it is preferable to contain at least one solid electrolyte species selected from the group of solid electrolytes consisting of sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes.

[0055] As the sulfide solid electrolyte, it preferably contains sulfur (S) as the main component of the anion element, and further contains, for example, Li element and A element. The A element is at least one selected from the group consisting of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In. The sulfide solid electrolyte may further contain at least one of O and halogen elements. Examples of the halogen element (X) include F, Cl, Br, I, etc. The composition of the sulfide solid electrolyte is not particularly limited, and examples include xLi2S·(100-x)P2S5 (70≦x≦80), yLiI·zLiBr·(100-y-z)(xLi2S·(1-x)P2S5) (0.7≦x≦0.8, 0≦y≦30, 0≦z≦30). The sulfide solid electrolyte may have a composition represented by the following general formula (1). Li 4-x Ge 1-x P x S4(0<x<1) ··· Formula (1) In formula (1), at least a portion of the Ge may be substituted with at least one selected from the group consisting of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. At least a portion of the P may be substituted with at least one selected from the group consisting of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. At least a portion of the Li may be substituted with at least one selected from the group consisting of Na, K, Mg, Ca, and Zn. At least a portion of the S may be substituted with a halogen. The halogen is at least one of F, Cl, Br, and I.

[0056] The oxide solid electrolyte contains oxygen (O) as the main anion element, and may also contain Li and Q elements (Q represents at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S). Examples of the oxide solid electrolyte include garnet-type solid electrolytes, perovskite-type solid electrolytes, Nasicon-type solid electrolytes, Li-PO-based solid electrolytes, and Li-BO-based solid electrolytes. Examples of the garnet-type solid electrolyte include Li7La3Zr2O 12 , Li 7-x La3(Zr 2-x Nb x )O 12 (0≦x≦2), Li5La3Nb2O 12 Examples of perovskite-type solid electrolytes include (Li,La)TiO3, (Li,La)NbO3, (Li,Sr)(Ta,Zr)O3, etc. Examples of Nasicon-type solid electrolytes include Li(Al,Ti)(PO4)3, Li(Al,Ga)(PO4)3, etc. Examples of Li-PO-based solid electrolytes include Li3PO4 and LIPON (a compound in which part of the O in Li3PO4 is substituted with N), and examples of Li-BO-based solid electrolytes include Li3BO3 and a compound in which part of the O in Li3BO3 is substituted with C, etc.

[0057] As the halide solid electrolyte, a solid electrolyte containing Li, M, and X (M represents at least one of Ti, Al, and Y, and X represents F, Cl, or Br) is suitable. 6-3z Y zX6 (where X represents Cl or Br, and 0 < z < 2), Li 6-(4-x)b (Ti 1-x Al x ) b F6 (0 < x < 1, 0 < b ≤ 1.5) is preferred. Li 6-3z Y z Among X6, Li3YX6 (where X represents Cl or Br) is more preferred in terms of excellent lithium ion conductivity, and further Li3YCl6 is preferred. Also, Li 6-(4-x)b (Ti 1-x Al x ) b F6 (0 < x < 1, 0 < b ≤ 1.5) is preferably included together with a solid electrolyte such as a sulfide solid electrolyte from the viewpoint of, for example, suppressing the oxidative decomposition of the sulfide solid electrolyte.

[0058] (Binder) Examples of the binder include vinyl halide resins, rubbers, polyolefin resins, etc. Examples of the vinyl halide resin include polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), etc. Examples of the polyolefin resin include butadiene rubber (BR), acrylate butadiene rubber (ABR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butyl rubber (isobutylene-isoprene rubber), etc. Examples of the polyolefin resin include polyethylene, polypropylene, etc. The binder may be a diene-based rubber containing a double bond in the main chain, for example, a butadiene-based rubber in which butadiene occupies 30 mol% or more of the whole.

[0059] (Other components) Examples of other components include oxide solid electrolytes, halide solid electrolytes, thickeners, surfactants, dispersants, wetting agents, defoamers, solvents, etc.

[0060] <Solid battery> The solid battery according to the present disclosure contains the positive electrode active material for a lithium ion battery according to the present disclosure. The solid-state battery according to the present disclosure preferably includes a positive electrode layer, a negative electrode layer, and an electrolyte layer or a separator disposed between the positive electrode layer and the negative electrode layer, and the positive electrode layer preferably contains the positive electrode material according to the present disclosure.

[0061] (Battery structure) Solid-state batteries include so-called all-solid-state batteries (in which the content of electrolytic solution as electrolyte is less than 10 mass % of the total amount of electrolyte) that use an inorganic solid electrolyte as the electrolyte. Fig. 1 is a schematic cross-sectional view showing an example of a solid-state battery according to the present disclosure. The solid-state battery shown in Fig. 1 includes an anode including an anode current collector 113 and an anode layer A, a solid electrolyte layer B, and a cathode including a cathode current collector 115 and a cathode layer C. The anode layer A includes an anode active material 101, a conductive additive 105, a binder 109, and a solid electrolyte 102. The cathode layer C includes a cathode active material 103, a binder 111, and a solid electrolyte 102.

[0062] When a set of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer is defined as a power generation unit, the solid-state battery may have only one power generation unit or may have two or more power generation units. When the solid-state battery has two or more power generation units, the power generation units may be connected in series or in parallel.

[0063] The solid-state battery may be configured by sealing the end faces (side faces) of the stacked structure of the positive electrode layer / solid electrolyte layer / negative electrode layer with resin. The electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on the surface. The shape of the solid-state battery is not particularly limited, and may be, for example, a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, or a laminate type.

[0064] (Electrolyte layer and separator) A solid-state battery includes an electrolyte layer or separator.

[0065] The electrolyte layer may be a layer containing a solid electrolyte. In the case of a layer containing a solid electrolyte (solid electrolyte layer), the solid electrolyte layer preferably contains one selected from the group consisting of a sulfide solid electrolyte, an oxide solid electrolyte, and a halide solid electrolyte. Specific examples of the sulfide solid electrolyte, oxide solid electrolyte, and halide solid electrolyte are the same as those described above.

[0066] The solid electrolyte layer may have a single layer structure or a multi-layer structure of two or more layers.

[0067] The solid electrolyte layer may contain a binder, or may not contain a binder. The binder that can be contained in the solid electrolyte layer is the same as the binder described above.

[0068] As the separator, a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, or polyamide can be used.

[0069] (positive electrode layer) The solid-state battery includes a positive electrode layer, which includes the positive electrode material of the present disclosure.

[0070] (Positive electrode current collector) The solid-state battery may further include a positive electrode current collector. The positive electrode current collector collects current from the positive electrode layer. The positive electrode current collector is disposed on the opposite side of the positive electrode layer from the electrolyte layer (or separator). The positive electrode current collector may be made of, for example, stainless steel, aluminum, copper, nickel, iron, titanium, or carbon, and is preferably an aluminum alloy foil or aluminum foil. The aluminum alloy foil or aluminum foil may be manufactured using powder. The positive electrode current collector may be, for example, in the form of a foil or a mesh. The positive electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on the surface thereof.

[0071] (negative electrode layer) The solid-state battery includes a negative electrode layer. The negative electrode layer contains a negative electrode active material. The negative electrode layer may contain at least one of a negative electrode solid electrolyte, a conductive additive, and a binder, as needed. Examples of negative electrode active materials include Li-based active materials such as metallic lithium, carbon-based active materials such as graphite, oxide-based active materials such as lithium titanate, and Si-based active materials such as elemental Si. The conductive additive, negative electrode solid electrolyte, and binder used in the negative electrode layer may be the same as those exemplified as the conductive additive contained in the positive electrode layer, the solid electrolyte contained in the solid electrolyte layer, and the binder.

[0072] (Negative electrode current collector) The solid-state battery may further include a negative electrode current collector. The negative electrode current collector collects current from the negative electrode layer. The negative electrode current collector is disposed on the opposite side of the negative electrode layer from the electrolyte layer (or separator). The negative electrode current collector may be made of, for example, stainless steel, aluminum, copper, nickel, iron, titanium, or carbon, with copper being preferred. The negative electrode current collector may be in the form of, for example, a foil or mesh. The negative electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on the surface thereof.

[0073] (positive and negative electrodes) The solid-state battery according to the present disclosure has a positive electrode. The positive electrode may have the above-described positive electrode layer and positive electrode current collector, or may be composed of only a positive electrode layer. From the viewpoint of rapid charge / discharge performance and discharge capacity, the positive electrode preferably contains the positive electrode material according to the present disclosure. The solid-state battery according to the present disclosure has a negative electrode. The negative electrode may have the above-described negative electrode layer and negative electrode current collector, or may be composed of only the negative electrode layer.

[0074] <Solid-state battery manufacturing method> A method for manufacturing a solid-state battery according to the present disclosure includes: a step of preparing a positive electrode layer, a negative electrode layer, and an electrolyte layer or a separator (preparation step); and a step of laminating a positive electrode layer, an electrolyte layer or a separator, and a negative electrode layer in this order (lamination step).

[0075] (preparation process) The preparation step is a step of preparing a positive electrode layer, a negative electrode layer, and an electrolyte layer or a separator.

[0076] The method for producing the positive electrode layer, the negative electrode layer, and the electrolyte layer is not particularly limited, and they are preferably produced by kneading components that can be contained in the positive electrode layer, the negative electrode layer, and the electrolyte layer to obtain a slurry, applying the slurry to a substrate, and pressing the dried film obtained by drying. The method for kneading the components that can be contained in the positive electrode layer when obtaining the slurry is not particularly limited, and examples thereof include a method of kneading using a kneading device, such as an ultrasonic homogenizer, a shaker, a thin film rotary mixer, a dissolver, a homomixer, a kneader, a roll mill, a sand mill, an attritor, a ball mill, a vibrator mill, or a high-speed impeller mill.

[0077] Methods for pressing the dried film include roll pressing and cold isostatic pressing (CIP).

[0078] The pressure during pressing is preferably 0.1 t / cm 2 More than 0.5t / cm 2 More preferably, 1 t / cm 2 The pressure during pressing is preferably 10 t / cm 2 Less than 8t / cm, preferably 8t / cm 2 Less than 6t / cm, more preferably 2 The following is the result.

[0079] A commercially available porous sheet (film) can be used as the separator.

[0080] (Lamination process) The lamination step is a step of laminating a positive electrode layer, an electrolyte layer or a separator, and a negative electrode layer in this order. In the lamination step, the positive electrode layer prepared in the preparation step, the electrolyte layer or separator, and the negative electrode layer are preferably laminated in this order, and pressed as necessary to obtain a laminate (electrode body).

[0081] It is preferable to fabricate the solid state battery according to the present disclosure through the above steps. [Example]

[0082] Examples will be described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, all "parts" and "%" are by mass.

[0083] Example 1 [Manufacturing positive electrode active materials for lithium-ion batteries] (Na-containing transition metal oxide production process) Mn(NO3)2·6H2O, Ni(NO3)2·6H2O, and Co(NO3)2·6H2O were used as raw materials and dissolved in pure water to a molar ratio of Mn, Ni, and Co of 5:2:3. A 12% by mass Na2CO3 solution was prepared, and these two solutions were simultaneously titrated into a beaker. The titration rate was controlled so that the pH was between 7.0 and 7.1. After the titration, the mixed solution was stirred at 50°C and 300 rpm for 24 hours. The resulting reaction product was washed with pure water, and the precipitated powder was separated by centrifugation. The resulting powder was dried at 120°C for 48 hours and then crushed in an agate mortar to obtain a powder (hereinafter referred to as the "intermediate powder"). The obtained intermediate powder was mixed with Na2CO3 in a composition ratio of Na 0.75 Mn 0.5 Ni 0.2 Co 0.3 The mixed powder was pressed under a load of 2 tons by cold isostatic pressing to produce pellets. The pellets obtained were pre-fired in air at 600°C for 6 hours and then fired at 700°C for 24 hours, after which they were cooled to room temperature to produce a Na-containing transition metal oxide (Na) with an O3-type crystal structure. 0.75 Mn 0.5 Ni 0.2 Co0.3 O2) was obtained.

[0084] (Shell forming process) The Na-containing transition metal oxide having an O3-type crystal structure was irradiated with a laser using a laser irradiator (ExLASER manufactured by Sakaguchi Electric Heating Co., Ltd.) to raise the temperature at a rate of 100°C / min up to 900°C. The temperature was maintained at 900°C for a holding time t of 5 minutes. Thereafter, the product was cooled to 250°C at a cooling rate of 100°C / min and allowed to cool to room temperature. This produced a Na-containing transition metal oxide (Na-doped precursor) (Na) having a core having an O3-type crystal structure and a shell covering the core and having a P2-type crystal structure. 0.75 Mn 0.5 Ni 0.2 Co 0.3 O2) was obtained.

[0085] (Ion exchange process) LiNO3 and LiCl were mixed at a mass ratio of 88:12 to obtain a mixed powder. The Na-doped precursor was weighed so that the ratio of the number of moles of Li contained in the mixed powder was 10 times the number of moles of Na-doped precursor. The Na-doped precursor and the mixed powder were mixed, and ion exchange was carried out in air at 280°C for 1 hour. After the ion exchange, water was added to dissolve the salt, and the mixture was further washed with water to obtain a positive electrode active material for lithium-ion batteries 1 (Li 0.66 Mn 0.50 Ni 0.20 Co 0.30 O2) was obtained.

[0086] [Solid-state battery manufacturing] (preparation process) -Preparation of the positive electrode layer- 85 g of lithium-ion battery positive electrode active material 1 (powdered by ball milling) and 10 g of conductive additive carbon black were added to 125 mL of n-methylpyrrolidone solution containing 5 g of binder polyvinylidene fluoride (PVDF), and the mixture was kneaded until uniformly mixed to prepare a slurry. This slurry was applied to a 15 μm thick Al positive electrode current collector substrate with a basis weight of 6 mg / cm. 2The electrode was then pressed to a thickness of 45 μm and a density of 2.4 g / cm. 3 Finally, this electrode was cut into a piece having a diameter of 16 mm to obtain a positive electrode having a positive electrode layer and a positive electrode current collector.

[0087] -Preparation of the negative electrode layer- The Li foil was cut to a diameter of 19 mm to obtain a negative electrode layer.

[0088] -Preparing the separator- A porous PP sheet was prepared as a separator.

[0089] (Lamination process) A positive electrode, a separator, and a negative electrode layer were stacked in this order to obtain a laminate. The positive electrode was stacked so that the positive electrode layer faced the separator. The laminate and a nonaqueous electrolyte (a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate) in a volume ratio of 3:7, with lithium hexafluorophosphate (LiPF6) dissolved at a concentration of 1 mol / L as a supporting electrolyte) were placed in a coin cell to prepare a CR2032 coin cell battery.

[0090] <Example 2> [Manufacturing positive electrode active materials for lithium-ion batteries] A positive electrode active material for a lithium ion battery was obtained in the same procedure as in Example 1, except that the holding time t in the shell formation step was set to 0.5 minutes. This positive electrode active material for a lithium ion battery was designated as positive electrode active material 2 for a lithium ion battery (Li 0.68 Mn 0.50 Ni 0.20 Co 0.30 O2).

[0091] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries 2 in the (preparation step) - preparation of the positive electrode layer.

[0092] <Comparative Example 1> [Manufacturing positive electrode active materials for lithium-ion batteries] A positive electrode active material for a lithium ion battery was obtained in the same procedure as in Example 1, except that the shell formation step was not performed and the ion exchange step was performed using a Na-doped precursor, a Na-containing transition metal oxide having an O3-type crystal structure obtained through the Na-containing transition metal oxide preparation step. This positive electrode active material for a lithium ion battery was designated as positive electrode active material C1 for a lithium ion battery (Li 0.70 Na 0.02 Mn 0.50 Ni 0.20 Co 0.30 O2).

[0093] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that in the (preparation step) - preparation of the positive electrode layer -, the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries C1.

[0094] <Comparative Example 2> [Manufacturing positive electrode active materials for lithium-ion batteries] A positive electrode active material for a lithium ion battery was obtained in the same manner as in Example 1, except that the shell formation step was changed to the following procedure. 0.68 Mn 0.50 Ni 0.20 Co 0.30 O2).

[0095] (Shell forming process) The Na-containing transition metal oxide having an O3-type crystal structure was irradiated with a laser using a laser irradiator to raise the temperature at a rate of 3°C / min up to 900°C. The temperature was maintained at 900°C for a holding time t of 1440 minutes (i.e., 24 hours). Thereafter, the temperature was cooled to 250°C at a cooling rate of 5°C / min and allowed to cool to room temperature. This resulted in the formation of a Na-doped precursor (Na 0.75 Mn 0.5 Ni 0.2 Co 0.3 O2) was obtained.

[0096] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that in the (preparation step) - preparation of the positive electrode layer -, the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries C2.

[0097] Example 3 A positive electrode active material for a lithium ion battery was obtained in the same procedure as in Example 1, except that the holding time t in the shell formation step was set to 0.083 minutes (i.e., 5 seconds). This positive electrode active material for a lithium ion battery was designated as positive electrode active material 3 for a lithium ion battery (Li 0.69 Mn 0.50 Ni 0.20 Co 0.30 O2).

[0098] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries 3 in the (preparation step) - preparation of the positive electrode layer.

[0099] <Comparative Example 3> A positive electrode active material for a lithium ion battery was obtained in the same procedure as in Example 1, except that in the shell formation step, the holding temperature was set to 700°C and the holding time t was set to 5 minutes. This positive electrode active material for a lithium ion battery was designated as positive electrode active material C3 for a lithium ion battery (Li 0.65 Mn 0.50 Ni 0.20 Co 0.30 O2).

[0100] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that in the (preparation step) - preparation of the positive electrode layer -, the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries C3.

[0101] <Evaluation> (R1 and R2) The "core diameter R1 and diameter R2 of the lithium-ion battery positive electrode active material" of the lithium-ion battery positive electrode active material obtained in each example were measured according to the above-mentioned "Procedure for measuring core diameter R1 and diameter R2 of the lithium-ion battery positive electrode active material." The results are shown in Table 1.

[0102] (Initial discharge capacity) A charge-discharge test was carried out using a galvanostat under the conditions of a current of 0.1 C, a charge cut-off voltage of 4.8 V, and a discharge cut-off voltage of 2.0 V. Starting with charging, after the first charge was completed, the amount of current required for discharging down to 2.0 V was calculated, and the initial discharge capacity was calculated by dividing this by the weight of the active material used in the measurement.

[0103] (Discharge capacity at 5C) A charge-discharge test was carried out using a galvanostat under the conditions of a current of 5 C, a charge cut-off voltage of 4.8 V, and a discharge cut-off voltage of 2.0 V. Starting with charging, after the first charge was completed, the amount of current required for discharging down to 2.0 V was calculated, and the discharge capacity at 5 C was calculated by dividing this by the weight of the active material used in the measurement.

[0104] (Capacity retention rate after 50 cycles) A charge-discharge test was performed under the same conditions as for the initial discharge capacity, and the first discharge capacity and the 50th discharge capacity were calculated. The 50th discharge capacity was divided by the first discharge capacity to obtain the capacity retention rate after 50 cycles.

[0105] [Table 1]

[0106] In Table 1, the column under "shell forming step" for Comparative Example 1 is marked with "-", which means that the shell forming step was not carried out. In Table 1, in Comparative Examples 1 and 2, there are some places where "-" is written under "Positive electrode active material for lithium ion batteries." This is because in Comparative Example 1, the obtained positive electrode active material for lithium ion batteries has only an O3-type crystalline structure and does not have a core portion or a shell portion. In Comparative Example 2, the obtained positive electrode active material for lithium ion batteries has only an O2-type crystalline structure and does not have a core portion or a shell portion.

[0107] From the above results, it is understood that the positive electrode active material for a lithium ion battery of this example has excellent rapid charge and discharge performance, and can provide a battery with a large discharge capacity in a potential range including a high potential range. [Explanation of symbols]

[0108] A negative electrode layer B Solid electrolyte layer C positive electrode layer 101 Negative electrode active material 102 Solid electrolyte 103 Cathode active material 105 Conductive additives 109,111 binders 113 Negative electrode current collector 115 Positive electrode current collector

Claims

1. a core portion having an O3 type crystal structure; A positive electrode active material for a lithium ion battery, comprising: a shell portion covering the core portion and having an O2-type crystal structure.

2. The positive electrode active material for a lithium ion battery according to claim 1 , wherein a diameter R1 of the core portion and a diameter R2 of the positive electrode active material for a lithium ion battery satisfy the following formula A and the following formula B: Formula A: (R2-R1) / 2≧10nm Formula B: (R2-R1) / R2≧0.01

3. A positive electrode material comprising the positive electrode active material for a lithium ion battery according to claim 1 or 2.

4. A positive electrode comprising the positive electrode material of claim 3.

5. A solid-state battery comprising the positive electrode active material for a lithium ion battery according to claim 1 or 2.

6. a step of heating a Na-containing transition metal oxide having an O3-type crystal structure to 800°C or higher and maintaining the temperature after heating for a time t that satisfies the following formula C; and a step of ion-exchanging Na contained in the Na-containing transition metal oxide obtained by carrying out the step with Li. Formula C: 0.04×t / r2<0.1 (In Formula C, t is time in minutes. In Formula C, r2 is the median diameter R2 of the resulting positive electrode active material for a lithium ion battery in nm.)

7. The method for producing a positive electrode active material for a lithium ion battery according to claim 6 , wherein the temperature is increased and maintained by laser irradiation.

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