Positive electrode active material, method for producing positive electrode active material, positive electrode mixture, non-aqueous lithium ion secondary battery, and all-solid-state lithium ion secondary battery

Abstract

To provide a positive electrode active material capable of improving the reversible capacity of a lithium-ion secondary battery, and a manufacturing method thereof.SOLUTION: A disclosed positive electrode active material is a positive electrode active material is expressed by the composition formula LixFeyO2 (where, 0<x<2 and 0<y<2), and the crystallite diameter is less than 200 angstrom. The disclosed manufacturing method includes the steps of: obtaining mixture powder by mixing Fe2O3 and Li2CO3 by the first ball mill method; baking the mixture powder; and grinding the fired mixture powder by a second ball milling method.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a positive electrode active material, a method for producing a positive electrode active material, a positive electrode mixture, a nonaqueous lithium ion secondary battery, and an all-solid-state lithium ion secondary battery. [Background technology]

[0002] Patent Document 1 describes a compound having the composition formula Li 2-x Ti 1-z Fe z O 3-y (0≦x<2, 0≦y≦1, 0.05≦z≦0.95) and has a cubic rock salt structure.

[0003] Patent Document 2 discloses a cathode active material layer having a current collector and a cathode active material layer provided on the current collector, the cathode active material being represented by the composition formula Li 2-x (Mn 1-m-n Fe n Ni m )O 3-y (where 0≦x<2, 0≦y≦1, 0.01≦m≦0.30, 0.05≦n≦0.75, 0.06≦m+n<1) and having a layered rock salt structure, the binder is a polymer containing polymerization units of a (meth)acrylic acid ester monomer, polymerization units of a vinyl monomer having an acid component, and polymerization units of an α,β-unsaturated nitrile monomer, and the content of the polymerization units of the vinyl monomer having an acid component is 1.0 to 3.0 wt % of all polymerization units of the polymer.

[0004] Patent Document 3 discloses a method for producing LiFeO2 having a layered rock salt structure, which is characterized by hydrothermally treating at least one of water-soluble iron salt, iron hydroxide, iron oxide hydroxide, and metallic iron in an aqueous solution containing lithium hydroxide and sodium hydroxide and / or potassium hydroxide at 130 to 300°C.

[0005] Patent Document 4 includes: (a) a step of subjecting a mixed solution containing iron(III) ions and Ni(II) ions to an alkali treatment, (b) a step of air-oxidizing the produced coprecipitate, (c) a step of aging the produced oxide at 100°C or lower, and (d) a step of subjecting the aged product to hydrothermal treatment in an alkali solution containing a Li compound at 400°C or lower, and is characterized in that the composition formula is LiFe 1-x Ni x A method for producing a layered rock salt type lithium iron oxide represented by O2 (0 < x < 0.5) is disclosed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] There is a demand to improve the reversible capacity of lithium ion secondary batteries.

[0008] The present disclosure aims to provide a positive electrode active material capable of improving the reversible capacity of a lithium ion secondary battery and a method for producing the same.

Means for Solving the Problems

[0009] The present disclosure has found that the above problems can be achieved by the following means: 《Aspect 1》 A composition formula Li x Fe y O2 (where 0 < x < 2 and 0 < y < 2), and a positive electrode active material having a crystallite size of 200 Å or less. <<Aspect 2>> 2. The cathode active material of embodiment 1, wherein 0.95≦x≦1.05 and 0.95≦y≦1.05. Aspect 3 3. The positive electrode active material of claim 1 or 2, having a cubic rock salt structure. Aspect 4 A positive electrode active material according to any one of Aspects 1 to 3, having a crystallite diameter of 170 Å or less. Aspect 5 Mixing Fe2O3 and Li2CO3 by a first ball mill method to obtain a mixed powder; Calcining the powder mixture; and pulverizing the fired mixture powder by a second ball mill method; 4. A method for producing a positive electrode active material according to any one of aspects 1 to 3, comprising: Aspect 6 A positive electrode mixture for a lithium ion secondary battery, comprising the positive electrode active material according to any one of aspects 1 to 4. Aspect 7 The positive electrode body, separator, and negative electrode body are housed in this order in an exterior body filled with a non-aqueous electrolyte solution, and The positive electrode body contains the positive electrode active material according to any one of aspects 1 to 4. Non-aqueous lithium-ion secondary battery. Aspect 8 a positive electrode layer, a solid electrolyte layer, and a negative electrode layer stacked in this order; The positive electrode layer contains the positive electrode active material according to any one of aspects 1 to 4. All-solid-state lithium-ion secondary battery. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a positive electrode active material that can improve the reversible capacity of a lithium ion secondary battery, and a method for producing the same. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is a schematic diagram of a non-aqueous lithium-ion secondary battery 100 according to the first embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram of an all-solid-state lithium-ion secondary battery 200 according to the first embodiment of the present disclosure. [Figure 3] FIG. 3 is a graph showing the X-ray crystal diffraction spectra of the positive electrode active materials of each example. [Figure 4] FIG. 4 is a graph showing the relationship between the crystallite size of the positive electrode active material of each example and the discharge capacity of the non-aqueous lithium-ion secondary battery of each example. [Figure 5] FIG. 5 is a graph showing the charge-discharge test results of the non-aqueous lithium-ion secondary battery of Comparative Example 1. [Figure 6] FIG. 6 is a graph showing the charge-discharge test results of the non-aqueous lithium-ion secondary battery of Example 1.

MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist of the disclosure.

[0013] 《Positive electrode active material》 The positive electrode active material of the present disclosure has a composition formula Li x Fe y O2 (where 0 < x < 2 and 0 < y < 2), and is a positive electrode active material having a crystallite size of 200 Å or less.

[0014] As means for improving the reversible capacity of the positive electrode active material represented by the composition formula Li x Fe y O2 (where 0 < x < 2 and 0 < y < 2), conventionally, attempts have been made such as substitution with different elements and changing the crystal structure.

[0015] On the other hand, the positive electrode active material of the present disclosure has a composition formula Li x Fe yO2 (where 0 < x < 2 and 0 < y < 2) represents a cathode active material with a crystallite size of 200 Å or less, which improves the reversible capacity. This is considered to be because the diffusion distance of lithium ions becomes shorter as the crystallite size decreases.

[0016] In general, for a cathode active material that is an intercalation compound, it is considered that the larger the crystallite size, the larger the reversible capacity, from the perspective of intercalating lithium ions between the layers.

[0017] Composition formula Li x Fe y In O2, 0 < x < 2 and 0 < y < 2. Here, x may be greater than 0, 0.05 or more, 0.10 or more, 0.50 or more, or 0.95 or more, and may be less than 2.00, 1.95 or less, 1.50 or less, or 1.05 or less. It is preferably 0.95 ≤ x ≤ 1.05. Similarly, y may be greater than 0, 0.05 or more, 0.10 or more, 0.50 or more, or 0.95 or more, and may be less than 2.00, 1.95 or less, 1.50 or less, or 1.05 or less. It is preferably 0.95 ≤ y ≤ 1.05.

[0018] Moreover, the cathode active material of the present disclosure can have a cubic rock salt structure.

[0019] The crystallite size of the cathode active material of the present disclosure is 200 Å or less.

[0020] Composition formula Li x Fe y When the crystallite size of the cathode active material represented by O2 (where 0 < x < 2 and 0 < y < 2) is 200 Å or less, a high discharge capacity can be obtained.

[0021] The crystallite size of the cathode active material may be 200 Å or less, 170 Å or less, 150 Å or less, 120 Å or less, or 100 Å or less, and may be 10 Å or more, 30 Å or more, 40 Å or more, or 50 Å or more.

[0022] 《Method for manufacturing cathode active material》 The method for producing a positive electrode active material of the present disclosure includes the following steps (A) to (C). (A) mixing FeO and LiCO by a first ball mill method to obtain a mixed powder; (B) calcining the powder mixture; and (C) Milling the fired mixture powder by a second ball milling method.

[0023] <Process (A)> Step (A) is to mix Fe2O3 and Li2CO3 by a first ball mill method to obtain a mixed powder.

[0024] The first ball milling method may be either a wet ball milling method or a dry ball milling method, but from the viewpoint of preventing the mixed powder from adhering to the container, a wet ball milling method is preferred.

[0025] In the first ball mill method, the rotation speed, rotation time, and the size and number of balls are not particularly limited.

[0026] The rotation speed may be, for example, 200 rpm to 2000 rpm. The rotation speed may be 200 rpm or more, 300 rpm or more, or 500 rpm or more, and may be 2000 rpm or less, 1500 rpm or less, 1000 rpm or less, or 500 rpm or less.

[0027] The rotation time may be 5 minutes to 10 hours. The rotation time may be 5 minutes or more, 10 minutes or more, 15 minutes or more, 30 minutes or more, or 1 hour or more, and may be 10 hours or less, 5 hours or less, 2 hours or less, 1 hour or less, or 30 minutes or less.

[0028] The size of the balls that can be used is, for example, 0.1 mm to 50 mm in diameter. The size of the balls may be 0.1 mm or more, 1 mm or more, or 5 mm or more, and may be 50 mm or less, 25 mm or less, or 10 mm or less.

[0029] Balls of different sizes may be used in combination, for example, balls with diameters of 10 mm, 5 mm, and 1 mm may be used in combination.

[0030] <Process (B)> Step (B) is to calcinate the mixture powder.

[0031] The firing may be carried out in an atmosphere inert to the powder mixture, such as a nitrogen atmosphere or a rare gas atmosphere, more specifically, an Ar atmosphere.

[0032] The firing temperature may be 600° C. to 1200° C. The firing temperature may be 600° C. or higher, 750° C. or higher, or 900° C. or higher, and may be 1200° C. or lower, 1000° C. or lower, or 900° C. or lower.

[0033] <Positive electrode mixture> The positive electrode mixture of the present disclosure is a positive electrode mixture for a lithium ion secondary battery that contains the positive electrode active material of the present disclosure.

[0034] The positive electrode mixture of the present disclosure may optionally contain a solid electrolyte, a conductive additive, and a binder, and may be obtained, for example, by mixing the positive electrode active material of the present disclosure with these optional materials.

[0035] <Solid electrolyte> The solid electrolyte is preferably an inorganic solid electrolyte, such as a sulfide solid electrolyte, an oxide solid electrolyte, or a nitride solid electrolyte.

[0036] Examples of sulfide solid electrolytes include, but are not limited to, sulfide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, and argyrodite-type solid electrolytes. Specific examples of sulfide solid electrolytes include Li2S-P2S5-based (Li7P3S 11, Li3PS4, Li8P2S9, etc.), Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-P2S5-GeS2(Li 13 GeP3S 16 , Li 10 GeP2S 12 ), LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 7-x PS 6-x Cl x etc.; or combinations thereof, but are not limited to these.

[0037] An example of an oxide solid electrolyte is Li7La3Zr2O 12、 Li 7-x La3Zr 1-x Nb x O 12、 Li 7-3x La3Zr2Al x O 12 , Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, or Li 3+x PO 4-x N x (LiPON), but is not limited to these.

[0038] The solid electrolyte may be glass, glass ceramics, or a crystalline material. Glass can be obtained by amorphous processing of a raw material composition (e.g., a mixture of Li2S and P2S5). Examples of amorphous processing include mechanical milling. Mechanical milling may be dry mechanical milling or wet mechanical milling, with the latter being preferred. This is because it can prevent the raw material composition from adhering to the wall surface of a container or the like. Glass ceramics can be obtained by heat treating glass. Crystalline materials can be obtained, for example, by solid-phase reaction processing of the raw material composition.

[0039] The solid electrolyte is preferably in the form of particles. The average particle size (D50) of the solid electrolyte is, for example, 0.01 μm or more. On the other hand, the average particle size (D50) of the solid electrolyte is, for example, 10 μm or less, and may be 5 μm or less. The lithium ion conductivity of the solid electrolyte at 25° C. is, for example, 1×10 -4 S / cm or more, 1×10 -3 It is preferably S / cm or more.

[0040] <Conductive additive> Known conductive additives can be used, such as carbon materials and metal particles. Examples of the carbon material include at least one selected from the group consisting of carbon black (e.g., acetylene black and furnace black), vapor-grown carbon fiber (VGCF), carbon nanotubes, and carbon nanofibers. From the viewpoint of electronic conductivity, at least one selected from the group consisting of VGCF, carbon nanotubes, and carbon nanofibers may be used. Examples of the metal particles include nickel, copper, iron, and stainless steel particles.

[0041] <Binder> The binder may be, for example, but not limited to, materials such as polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC), butadiene rubber (BR) or styrene butadiene rubber (SBR), or combinations thereof.

[0042] <<Non-aqueous lithium-ion secondary battery>> The nonaqueous lithium ion secondary battery of the present disclosure is a nonaqueous lithium ion secondary battery in which a positive electrode body, a separator, and a negative electrode body are housed in this order in an exterior body filled with a nonaqueous electrolyte solution, and the positive electrode body contains the positive electrode active material of the present disclosure.

[0043] FIG. 1 is a schematic diagram of a nonaqueous lithium-ion secondary battery 100 according to a first embodiment of the present disclosure.

[0044] As shown in Fig. 1, a nonaqueous lithium-ion secondary battery 100 according to the first embodiment of the present disclosure includes a positive electrode assembly 110, a separator 120, and a negative electrode assembly 130, arranged in this order, housed in an exterior case 150 filled with a nonaqueous electrolyte solution 140. The positive electrode assembly 110 has a shape in which both sides of a positive electrode current collector layer 111 are covered with positive electrode active material layers 112. The negative electrode assembly 130 has a shape in which both sides of a negative electrode current collector layer 131 are covered with negative electrode active material layers 132. The positive electrode active material layers 112 contain the positive electrode active material of the present disclosure.

[0045] <Positive electrode body> The positive electrode body includes a positive electrode current collector and a positive electrode active material. The positive electrode body may be, for example, a layer or rod-shaped positive electrode body, the surface of which is partially or entirely covered with a layer containing the positive electrode active material, i.e., a positive electrode active material layer.

[0046] The positive electrode body contains the positive electrode active material of the present disclosure. More specifically, the positive electrode active material of the present disclosure can be contained in a positive electrode active material layer that constitutes the positive electrode body.

[0047] (Positive electrode current collector layer) The material used for the positive electrode current collector layer may be, but is not limited to, stainless steel (SUS), aluminum, copper, nickel, iron, titanium, carbon, etc. Among these, the material for the positive electrode current collector layer is preferably aluminum.

[0048] The shape of the positive electrode current collector layer is not particularly limited, and examples thereof include a rod shape, a foil shape, a plate shape, a mesh shape, etc. Among these, the foil shape is preferred.

[0049] (Cathode active material layer) The positive electrode active material layer may contain the positive electrode active material of the present disclosure. The positive electrode active material layer may be formed from the positive electrode mixture of the present disclosure and optionally other materials.

[0050] <Separator layer> The separator layer may be a porous resin layer, for example a polypropylene or polyethylene layer.

[0051] The separator layer can be a porous polymer membrane such as a porous polyethylene membrane (PE), a porous polypropylene membrane (PP), a porous polyolefin membrane, or a porous polyvinyl chloride membrane. Alternatively, a lithium ion conductive polymer electrolyte membrane can be used. These separator layers can be used alone or in combination. From the perspective of increasing battery output, it is preferable to use a triple-layer coated separator layer in which a porous polyethylene membrane (PE) is sandwiched between upper and lower layers of porous polypropylene membrane (PP).

[0052] <Negative electrode body> The negative electrode body has a negative electrode current collector and a negative electrode active material. The negative electrode body may have a shape in which the surface of a layered or rod-shaped negative electrode body is partially or entirely covered with a layer containing the negative electrode active material, i.e., a negative electrode active material layer.

[0053] (negative electrode current collector layer) The material used for the negative electrode current collector layer may be the same as the material used for the positive electrode current collector layer, but is preferably copper.

[0054] (Negative electrode active material layer) The negative electrode active material layer contains a negative electrode active material and, optionally, a solid electrolyte, and may further contain additives used in negative electrode active material layers of lithium ion batteries, such as a conductive additive or a binder, depending on the intended use or purpose.

[0055] The negative electrode active material may be, for example, metallic lithium, or may be a material capable of absorbing and releasing metal ions such as lithium ions. Examples of materials capable of absorbing and releasing metal ions such as lithium ions include, but are not limited to, alloy-based negative electrode active materials and carbon materials.

[0056] The alloy-based negative electrode active material is not particularly limited, and examples thereof include Si alloy-based negative electrode active materials and Sn alloy-based negative electrode active materials. Examples of Si alloy-based negative electrode active materials include silicon, silicon oxide, silicon carbide, silicon nitride, and solid solutions thereof. The Si alloy-based negative electrode active material may contain elements other than silicon, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, or Ti. Examples of Sn alloy-based negative electrode active materials include tin, tin oxide, tin nitride, and solid solutions thereof. The Sn alloy-based negative electrode active material may contain elements other than tin, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, or Si. Among these, Si alloy-based negative electrode active materials are preferred.

[0057] The carbon material is not particularly limited, and examples thereof include hard carbon, soft carbon, and graphite.

[0058] The conductive additive and binder may be any of those described above in relation to the positive electrode mixture.

[0059] (Non-aqueous electrolyte) The non-aqueous electrolyte may be a composition in which a supporting salt is contained in a non-aqueous solvent. The non-aqueous solvent may be a material selected from the group consisting of an organic electrolyte, a fluorine-based solvent, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and a combination of two or more thereof.

[0060] The non-aqueous solvent is preferably a fluorine-based solvent, such as a fluorinated carbonate. Specific examples of the fluorinated carbonate include methyl 2,2,2-trifluoroethyl ester (MFEC; CAS 156783-95-8) and / or difluorodimethyl carbonate (DFDMC), and a 50:50 volume mixture of these is particularly preferred.

[0061] Examples of the supporting salt include materials selected from the group consisting of lithium compounds (lithium salts) of LiPF, LiBF, LiClO, LiAsF, LiCF, SO, LiC, F, SO, LiN(CF, SO), LiC(CF, SO), LiI, and combinations of two or more of these. From the viewpoints of improving the battery voltage and durability, LiPF is preferred as the supporting salt.

[0062] (exterior body) The exterior body can be made of a material that is inactive to the non-aqueous electrolyte solution, such as a resin.

[0063] <<All-solid-state lithium-ion secondary battery>> The all-solid-state lithium ion secondary battery according to the present disclosure is an all-solid-state lithium ion secondary battery in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated in this order, and the positive electrode layer contains the positive electrode active material according to the present disclosure.

[0064] FIG. 2 is a schematic diagram of an all-solid-state lithium-ion secondary battery 200 according to a first embodiment of the present disclosure.

[0065] 2, an all-solid-state lithium-ion secondary battery 200 according to the first embodiment of the present disclosure includes a positive electrode current collector layer 210, a positive electrode active material layer 220, a solid electrolyte layer 230, a negative electrode active material layer 240, and a negative electrode current collector layer 250 laminated in this order, and the positive electrode active material layer 220 contains the positive electrode active material of the present disclosure. Here, the positive electrode active material layer 220 and the positive electrode current collector layer 210 are collectively referred to as the positive electrode layer, and the negative electrode active material layer 240 and the negative electrode current collector layer 250 are collectively referred to as the negative electrode layer.

[0066] In the all-solid-state lithium-ion secondary battery of the present disclosure, the positive electrode layer and the negative electrode layer can be determined by reference to the description in the above "Nonaqueous Lithium-ion Secondary Battery."

[0067] The solid electrolyte layer may contain the solid electrolyte described above in the "Positive Electrode Mixture" section, and may optionally contain a binder. [Example]

[0068] Examples 1 to 3 and Comparative Examples 1 and 2 <Preparation of Positive Electrode Active Material> For Examples 1 to 3 and Comparative Example 1, Fe2O3 and Li2CO3 were mixed in ethanol by a wet ball mill method under the conditions shown in the following Table 1. The resulting mixed powder was molded into pellets (step (A)).

[0069] Next, the boat-shaped aluminum boat containing the molded pellets was wrapped in Cu foil and fired in an Ar atmosphere at 900°C for 12 hours (step (B)).

[0070] Finally, the obtained powder was pulverized by a dry ball mill method under the conditions shown in Table 1 (step (C)). The crystallite size was controlled by adjusting the ball milling time. Specifically, as shown in Table 1, the number of sets in the dry ball mill method differed depending on the example.

[0071] [Table 1]

[0072] In Comparative Example 2, ball milled LiCoO2 was used as the positive electrode active material.

[0073] <X-ray diffraction test> For each example of the positive electrode active material, an X-ray diffraction test was performed using a non-reflective sample plate, and the X-ray diffraction spectrum was analyzed. The results are shown in Figure 3. The crystallite diameter was calculated from the half-width of the peak representing the (200) plane in the obtained X-ray diffraction spectrum.

[0074] More specifically, the crystallite diameter (nm) was defined as D, the Scherrer constant as K, the wavelength of the X-ray as λ, the half-width as B, and the Bragg angle as θ, and the calculation was performed using the following formula: D=Kλ / BCosθ

[0075] The calculation results are shown in Figure 4.

[0076] The half-value width is the width of the diffraction line at half the height of the diffraction line intensity.

[0077] <Evaluation of charge / discharge characteristics> A coin-type lithium-ion battery cell (CR2032) was prepared using the positive electrode active material of each example. Specifically, the positive electrode active material of each example was weighed out in a weight ratio of 85 / 15 / 5 of AB / PVdF and dispersed and mixed in N-methyl-2-pyrrolidone to form a slurry. The slurry was applied to an aluminum current collector foil as a positive electrode current collector layer and dried in a vacuum at 120°C overnight to form a positive electrode active material layer on the positive electrode current collector layer. This was used as a positive electrode body.

[0078] TDDK-217 (Daikin) was used as the electrolyte, and metallic Li foil was used as the negative electrode body.

[0079] The charge / discharge characteristics were evaluated in a thermostatic chamber maintained at 60° C., in a voltage range of 1.5-5 V, and at a 0.1 C rate (1 C=185 mA / g). The evaluation results of Comparative Example 1 and Example 1 are shown in FIGS. 5 and 6, respectively.

[0080] <result> Table 2 shows the relationship between the crystallite size (Å) and the discharge capacity (mAh / g) for each example.

[0081] [Table 2]

[0082] As shown in Table 2, the composition is Li x Fe y In the lithium ion batteries using the positive electrode active materials of Examples 1 to 3, which were O2 and had crystallite diameters of 55 Å, 109 Å, and 167 Å, respectively, the discharge capacities were 180 mAh / g, 98 mAh / g, and 81 mAh / g, respectively. x Fe y In the lithium ion battery using the positive electrode active material of Comparative Example 1, which was O2 and had a crystallite diameter of 830 Å, the discharge capacity was 5 mAh / g, which was much lower than that of the lithium ion batteries using the positive electrode active materials of Examples 1 to 3.

[0083] In addition, the composition is Li x Co y In the lithium ion battery using the positive electrode active material of Comparative Example 2, which was O2 and had a crystallite diameter of 200 or less, the discharge capacity was 5 mAh / g, which was much lower than that of the lithium ion batteries using the positive electrode active materials of Examples 1 to 3. [Explanation of symbols]

[0084] 100 Non-aqueous lithium-ion secondary battery 110 Positive electrode body 111 Positive electrode current collector layer 112 Cathode active material layer 120 Separator 130 negative electrode body 131 Negative electrode current collector layer 132 Negative electrode active material layer 140 Nonaqueous electrolyte 150 exterior body 200 All-solid-state lithium-ion secondary battery 210 Positive electrode current collector layer 220 Cathode active material layer 230 Solid Electrolyte Layer 240 Negative electrode active material layer 250 Negative electrode collector layer

Claims

[Claim 1] Composition formula Li ｘ Fe ｙ O ２ (wherein 0<x<2 and 0<y<2), and having a crystallite diameter of 50 Å or more and 100 Å or less, mixing Fe 2 O 3 and Li 2 CO 3 by a first ball mill method to obtain a mixed powder; Calcining the powder mixture; and pulverizing the fired mixture powder by a second ball mill method; A method for producing a positive electrode active material, comprising:

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