Lithium metal composite oxide, positive electrode active material for lithium secondary battery, positive electrode for lithium secondary battery, and lithium secondary battery

Abstract

A lithium metal composite oxide containing at least Li, Ni, and an element M1, which is an alkaline earth metal element, and satisfying (1) and (2). (1) The Me site occupancy in the lithium sites of a layered rock salt crystal structure as determined by Rietveld analysis of a diffraction peak obtained by powder X-ray diffraction using a CuK [alpha] ray is 4.0% or less, and (2) the particle strength of the lithium metal composite oxide is more than 100 MPa and less than 200 MPa.

Description

Technical Field

[0001] The present invention relates to a lithium metal composite oxide, a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery.

[0002] This application claims priority based on Japanese Patent Application No. 2022-188173 filed on November 25, 2022, and incorporates its content herein. Background Art

[0003] As a positive electrode active material for a lithium secondary battery, a lithium metal composite oxide is used. For the purpose of improving the performance of a lithium secondary battery, research has been conducted on controlling the physical properties of the lithium metal composite oxide.

[0004] For example, in Patent Document 1, as a positive electrode active material capable of further improving battery characteristics, a lithium nickel manganese cobalt composite oxide having a Me site occupancy of 93.0% or more is disclosed.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: JP-A-2020-176051 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] In the process of the progress of the application field of lithium secondary batteries, further improvement in rate performance is required for lithium secondary batteries.

[0010] In this specification, the "rate performance" refers to the ratio of the discharge capacity at 3CA to the discharge capacity at 0.2CA, where the discharge capacity at 0.2CA is set to 100%. The higher this ratio, the more the discharge capacity is maintained even when a large current flows, and the more preferable it is as battery performance.

[0011] There is room for improvement in the lithium metal composite oxide used in lithium secondary batteries from the viewpoint of improving rate performance.

[0012] The present invention has been made in view of the above circumstances, and an object thereof is to provide a lithium metal composite oxide, a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery that can improve the rate performance of a lithium secondary battery.

[0013] Means for Solving the Problems

[0014] The present invention includes the following [1] to [9].

[0015] [1]A lithium metal composite oxide, which contains at least Li, Ni, and an element M1 as an alkaline earth metal element, and satisfies the following (1) and (2).

[0016] (1) The occupancy of the Me position in the lithium site of the layered rock salt-type crystal structure, obtained by Rietveld analysis of the diffraction peaks from powder X-ray diffraction using CuKα radiation, is 4.0% or less.

[0017] (2) The particle strength of the above lithium metal composite oxide exceeds 100 MPa and is lower than 200 MPa.

[0018] [2] The lithium metal composite oxide according to [1] is represented by the following compositional formula (A).

[0019] Li a Ni b M1 c M2 (1-b-c) O2(A)

[0020] (The compositional formula (A) satisfies 0.98 ≤ a ≤ 1.10, 0.60 ≤ b ≤ 0.95, and 0 < c ≤ 0.05, M1 is the above element M1, and M2 is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Al, Zn, Sn, Zr, B, Si, Nb, W, Mo, Ta, S, and P.)

[0021] [3] The lithium metal composite oxide according to [1] or [2], wherein the content ratio of the above element M1 contained in the above lithium metal composite oxide is greater than 0 mol% and 5 mol% or less relative to the total molar number of elements other than Li and oxygen atoms constituting the above lithium metal composite oxide.

[0022] [4] The lithium metal composite oxide according to any one of [1] to [3], the BET specific surface area of which is less than 1.0 m 2 / g.

[0023] [5] The lithium metal composite oxide according to any one of [1] to [4], wherein the 50% cumulative volume particle size D obtained from the cumulative particle size distribution curve based on volume measured by the laser diffraction scattering method 50 exceeds 5 μm and is less than 20 μm.

[0024] [6] The lithium metal composite oxide according to any one of [1] to [5], which has a peak showing the maximum heat release at 400 °C or higher in differential thermal-thermogravimetric simultaneous analysis.

[0025] [7] A positive electrode active material for a lithium secondary battery, which contains the lithium metal composite oxide described in any one of [1] to [6].

[0026] [8] A positive electrode for a lithium secondary battery, which contains the positive electrode active material for a lithium secondary battery described in [7].

[0027] [9] A lithium secondary battery, which contains the positive electrode for a lithium secondary battery described in [8].

[0028] Advantages of the Invention

[0029] According to the present invention, it is possible to provide a lithium metal composite oxide, a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery that can improve the rate characteristics of the lithium secondary battery. Description of the Drawings

[0030] Figure 1 It is a schematic configuration diagram showing an example of a lithium secondary battery.

[0031] Figure 2 It is a schematic configuration diagram showing an example of a lithium secondary battery. Detailed Description

[0032] The definitions of the terms in this specification are as follows.

[0033] The metal composite compound will also be referred to as "MCC" hereinafter.

[0034] The lithium metal composite oxide will also be referred to as "LiMO" hereinafter.

[0035] The positive electrode active material for a lithium secondary battery will also be referred to as "CAM" hereinafter.

[0036] "Ni" does not represent elemental nickel metal, and the same applies to the descriptions of other elements such as Co and Mn.

[0037] For a numerical range, "A to B" means "A or more and B or less". For example, when it is described as "5 to 15 μm", it means a range of 5 μm or more and 15 μm or less, and it means a numerical range including 5 μm as the lower limit value and 15 μm as the upper limit value.

[0038] A lithium secondary battery means a lithium ion secondary battery.

[0039] The method for measuring the rate performance in this specification is as follows.

[0040] [Measurement of Rate Performance]

[0041] (Fabrication of the Positive Electrode for Lithium Secondary Battery)

[0042] Use LiMO of this embodiment as the CAM. Mix the CAM, conductive material, and binder at a ratio of CAM:conductive material:binder = 92:5:3 (mass ratio) to prepare a paste-like positive electrode mixture. When preparing the positive electrode mixture, use N-methyl-2-pyrrolidone as the organic solvent. Use acetylene black as the conductive material. Use polyvinylidene fluoride as the binder.

[0043] Apply the obtained positive electrode mixture onto an Al foil with a thickness of 20 μm serving as the current collector, and perform vacuum drying at 150 °C for 8 hours to obtain the positive electrode for lithium secondary battery. The area of this positive electrode for lithium secondary battery is set to 1.65 cm 2 .

[0044] (Fabrication of Lithium Secondary Battery)

[0045] Perform the following operations inside a glove box under an argon atmosphere.

[0046] Place the positive electrode for lithium secondary battery fabricated in (Fabrication of the Positive Electrode for Lithium Secondary Battery) face down with the Al foil side on the lower cover of the component for coin-type battery R2032 (manufactured by Takizawa Co., Ltd.), and place a separator (porous polyethylene membrane) thereon. Inject 300 μl of electrolyte. Use a solution obtained by dissolving LiPF6 at a ratio of 1.0 mol / l in a mixed solution containing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate at a volume ratio of 30:35:35 as the electrolyte.

[0047] Next, use metallic lithium as the negative electrode, place the negative electrode on the upper side of the above-mentioned separator, cover the upper cover through a gasket, and perform caulking with a caulking machine to fabricate a lithium secondary battery (coin-type half-cell R2032).

[0048] Use the lithium secondary battery fabricated by the above method to measure the rate performance by the following method.

[0049] (Rate Performance)

[0050] "High rate performance" means that the ratio of the discharge capacity obtained through the following discharge rate test is 80% or more.

[0051] (Discharge Rate Test)

[0052] Test temperature: 25 °C

[0053] Maximum charging voltage 4.3 V, charging current 0.2 CA, constant current and constant voltage charging

[0054] The minimum discharge voltage is 2.5V, the discharge current is 0.2CA or 3CA, and the discharge is at a constant current.

[0055] Using the discharge capacity at a constant current of 0.2CA and the discharge capacity at a constant current of 3CA, calculate the 3CA / 0.2CA discharge capacity ratio obtained by the following formula as an index of the rate performance.

[0056] 3CA / 0.2CA discharge capacity ratio (%)

[0057] = Discharge capacity at 3CA / Discharge capacity at 0.2CA × 100 (formula)

[0058] <limo>

[0059] The elements constituting LiMO include at least Li, Ni, and element M1. LiMO may further include element M2.

[0060] Element M1 is an alkaline earth metal element. Specifically, element M1 is one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, and Ra. Element M2 is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Al, Zn, Sn, Zr, B, Si, Nb, W, Mo, Ta, S, and P.

[0061] Element M1 is preferably one or more elements selected from the group consisting of Mg, Ca, and Ba, and preferably Mg. Element M2 is preferably one or more elements selected from the group consisting of Co, Mn, Ti, Al, Zr, B, Nb, and W. In addition, element M2 must include one or more elements selected from the group consisting of Co, Mn, and Al, and may also include one or more elements selected from the group consisting of Fe, Cu, Ti, Zn, Sn, Zr, B, Si, Nb, W, Mo, Ta, S, and P.

[0062] "Crystal Structure"

[0063] LiMO has a layered rock salt-type crystal structure.

[0064] The layered rock salt-type crystal structure refers to a crystal structure in which a lithium layer and a transition metal layer other than lithium sandwich an oxygen layer and are alternately stacked. The transition metal layer is composed of transition metal ions, and the oxygen layer is composed of oxygen ions. The layered rock salt-type crystal structure is typically an α-NaFeO2-type crystal structure.

[0065] LiMO is more preferably a hexagonal crystal structure or a monoclinic crystal structure.

[0066] The hexagonal crystal structure belongs to any space group selected from the group consisting of P3, P31, P32, R3, P-3, R-3, P312, P321, P3112, P3121, P3212, P3221, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P61, P65, P62, P64, P63, P-6, P6 / m, P63 / m, P622, P6122, P6522, P6222, P6422, P6322, P6mm, P6cc, P63cm, P63mc, P-6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P63 / mcm, and P63 / mmc.

[0067] In addition, the crystal structure of the monoclinic form belongs to any space group selected from the group consisting of P2, P21, C2, Pm, Pc, Cm, Cc, P2 / m, P21 / m, C2 / m, P2 / c, P21 / c, and C2 / c.

[0068] Among them, in order to obtain a lithium secondary battery with a high initial discharge capacity and rate performance, LiMO is further preferably a hexagonal crystal structure belonging to the space group R-3m, or a monoclinic crystal structure belonging to C2 / m.

[0069] [Method for confirming crystal structure]

[0070] The crystal structure of LiMO can be confirmed by observing using a powder X-ray diffractometer.

[0071] Powder X-ray diffraction measurement can be performed using an X-ray diffractometer, such as UltimaIV manufactured by Rigaku Corporation.

[0072] LiMO contains an element M1 as an alkaline earth metal element. In the layered rock salt-type crystal structure, the element M1 contained in LiMO is dissolved in the transition metal layer. The element M1 present in the transition metal layer can make the oxygen atoms in the crystal structure unevenly distributed by existing with a valence of 2. Therefore, the affinity with the transition metal element is increased, Ni becomes less mobile, and thus nickel ions are less likely to migrate to the lithium site. Therefore, the ratio of cation mixing is reduced, and LiMO satisfying the above (1) is obtained.

[0073] LiMO is in particle form and satisfies the following (1) and (2). (1)

[0075] The occupancy of the Me position in the lithium site of the layered rock salt-type crystal structure obtained by Rietveld analysis of the diffraction peaks obtained by powder X-ray diffraction using CuKα rays in LiMO is 4.0% or less.

[0076] The above Me is an element other than Li and oxygen atoms constituting LiMO. Specifically, the above Me is Ni, the above element M1, and element M2.

[0077] The occupancy of the Me position is preferably 3.9% or less, more preferably 3.6% or less.

[0078] If the occupancy of the Me position is below the above upper limit value, the ratio of cation mixing is small, and lithium ions remain in the lithium site, so the rate performance is likely to be high.

[0079] The occupancy of the Me site described above is preferably low, but the lower limit value can be, for example, 1.0% or more, 2.0% or more, or 3.0% or more.

[0080] The occupancy of the above-mentioned Me is preferably 1.0 to 4.0%, more preferably 2.0 to 3.9%, and still more preferably 3.0 to 3.6%.

[0081] [Method for measuring the occupancy of the Me site]

[0082] The occupancy of the Me site in the lithium site can be calculated by performing Rietveld analysis on the diffraction peaks obtained from powder X-ray diffraction. Rietveld analysis refers to a method of optimizing the crystal structure parameters in the crystal structure model in such a way that the difference between the measured powder X-ray diffraction pattern and the simulated pattern from the crystal structure model becomes the smallest by comparing them.

[0083] The above-mentioned diffraction peaks can be obtained by performing powder X-ray diffraction measurement using an X-ray diffraction apparatus. The X-ray diffraction apparatus used is D8 Advance manufactured by Bruker Corporation. Specifically, LiMO is filled in a dedicated substrate, and using a CuKα ray source, measurement is performed under the conditions of diffraction angle 2θ = 10° to 90° and sampling amplitude 0.02°, and a powder X-ray diffraction pattern is obtained.

[0084] Next, Rietveld analysis is performed on the diffraction peaks in the powder X-ray diffraction pattern, and LiMO is represented by the crystal structure of the initial crystal structure model, i.e., the layered rock salt type crystal structure (Li 1-n Me n )(Me 1-n Li n )O2, and n as the occupancy of the Me site is optimized. Rietveld analysis uses the powder X-ray analysis software TOPAS manufactured by Bruker Corporation. (2)

[0086] The particle strength of LiMO exceeds 100 MPa and is lower than 200 MPa.

[0087] [Method for measuring the particle strength]

[0088] The particle strength of LiMO is measured by the following method.

[0089] First, select LiMO particles having a size of D 50 (unit: μm) ± about 2 μm. When selecting, avoid particles with extremely deformed shapes. Specifically, select particles having a ratio of the minor axis to the major axis (minor axis / major axis) of 0.7 or more and 1.3 or less. D 50 As described later in [D 50 It is measured as described in the measurement method.

[0090] Here, the "major axis" refers to the longest diameter of the particle. The "minor axis" refers to the shortest diameter of the particle. Next, a test pressure (load) is applied to one particle of LiMO selected above, and the displacement amount of the LiMO particle is measured.

[0091] For the measurement, "Micro Compression Tester MCT-510" manufactured by Shimadzu Corporation is used.

[0092] When the test pressure is slowly increased, the pressure value at which the displacement amount becomes the maximum in a state where the test pressure is substantially constant is set as the test force (P) (unit: MPa).

[0093] From the obtained test force (P), the compressive strength (St) (unit: MPa) is calculated by the following formula (X) (refer to Journal of the Mining Society of Japan, Vol. 81, (1965)). This operation is performed a total of 7 times, and the average value of 5 times excluding the maximum and minimum values of the compressive strength is calculated as the particle strength. In the following formula (X), d is the secondary particle diameter of LiMO (unit: μm).

[0094] St = 2.8 × P / (π × d × d) Formula (X)

[0095] The particle strength of LiMO is preferably 105 MPa or more, more preferably 110 MPa or more.

[0096] The particle strength of LiMO can be, for example, 190 MPa or less, or 180 MPa or less.

[0097] The particle strength is preferably 105 to 190 MPa, more preferably 110 to 180 MPa.

[0098] If LiMO having a particle strength in the above range is used as the CAM, the particles of the CAM are less likely to crack in the pressing process during the manufacture of the electrode. Therefore, cracks that can become resistance are less likely to occur, and the rate performance is less likely to deteriorate.

[0099] LiMO is preferably represented by the following compositional formula (A).

[0100] Li a Ni b M1 c M2 (1-b-c) O2 (A)

[0101] (The compositional formula (A) satisfies 0.98 ≤ a ≤ 1.10, 0.60 ≤ b ≤ 0.95, and 0 < c ≤ 0.05, M1 is the above element M1, and M2 is the above element M2.)

[0102] (a)

[0103] In the compositional formula (A), a is preferably 0.98 or more, more preferably 0.99 or more, and still more preferably 1.00 or more. a is preferably 1.09 or less, more preferably 1.08 or less, and still more preferably 1.07 or less. From the viewpoint of improving the rate characteristics of the lithium secondary battery, a preferably satisfies 0.98 ≤ a ≤ 1.09, more preferably satisfies 0.99 ≤ a ≤ 1.08, still more preferably satisfies 1.00 ≤ a ≤ 1.08, and particularly preferably satisfies 1.00 ≤ a ≤ 1.07.

[0104] (b)

[0105] In the compositional formula (A), b is preferably 0.65 or more, more preferably 0.70 or more, and still more preferably 0.75 or more. b is preferably 0.93 or less. From the viewpoint of improving the rate characteristics of the lithium secondary battery, b preferably satisfies 0.65 ≤ b ≤ 0.95, more preferably satisfies 0.70 ≤ b ≤ 0.95, and still more preferably satisfies 0.75 ≤ b ≤ 0.93.

[0106] (c)

[0107] In the compositional formula (A), c is preferably 0.001 or more, more preferably 0.002 or more. c is preferably 0.04 or less. From the viewpoint of improving the rate characteristics of the lithium secondary battery, c preferably satisfies 0.001 ≤ c ≤ 0.05, and more preferably satisfies 0.002 ≤ c ≤ 0.04.

[0108] LiMO is preferably represented by the following compositional formula (A1).

[0109] Li a Ni b M1 c M2 (1-b-c) O2(A1)

[0110] (The compositional formula (A1) satisfies 1.00 ≤ a ≤ 1.08, 0.75 ≤ b ≤ 0.93, and 0.001 ≤ c ≤ 0.05. M1 is one or more elements selected from the group consisting of Mg, Ca, and Ba. M2 must contain one or more elements selected from the group consisting of Co, Mn, and Al, and may also contain one or more elements selected from the group consisting of Fe, Cu, Ti, Zn, Sn, Zr, B, Si, Nb, W, Mo, Ta, S, and P.)

[0111] From the viewpoint of improving the rate characteristics, the content ratio of the element M1 in LiMO is preferably more than 0 mol% and 5 mol% or less, and more preferably more than 0 mol% and 2 mol% or less, relative to the total number of moles of the elements other than Li and oxygen atoms constituting LiMO (for example, Ni, element M1, and element M2).

[0112] [Component analysis]

[0113] The component analysis of LiMO (the above compositional formula (A) and the content ratio of the above element M1) can be determined by dissolving the obtained LiMO powder in hydrochloric acid and then using an ICP emission spectroscopic analyzer.

[0114] As the ICP emission spectroscopic analyzer, for example, SPS3000 manufactured by SII NanoTechnology Inc. can be used.

[0115] The BET specific surface area of LiMO is preferably less than 1.0 m 2 / g, more preferably 0.99 m 2 / g or less, and even more preferably 0.98 m 2 / g or less.

[0116] The BET specific surface area of LiMO is preferably 0.5 m 2 / g or more, more preferably 0.6 m 2 / g or more, and even more preferably 0.7 m 2 / g or more.

[0117] The BET specific surface area is preferably 0.5 m 2 / g or more and less than 1.0 m 2 / g, more preferably 0.6 - 0.99 m 2 / g, and even more preferably 0.7 - 0.98 m 2 / g.

[0118] If the BET specific surface area satisfies the above range, the rate performance of the lithium secondary battery is likely to be high.

[0119] [BET specific surface area measurement]

[0120] The BET specific surface area of LiMO can be measured using a BET specific surface area analyzer. As the BET specific surface area analyzer, for example, Macsorb (registered trademark) manufactured by Mountech Co., Ltd. can be used. As a pretreatment, it is preferable to dry LiMO in a nitrogen atmosphere at 105 °C for 30 minutes.

[0121] The D of LiMO 50 is preferably more than 5 μm, more preferably 10 μm or more. The D 50 is preferably less than 20 μm, more preferably 15 μm or less. The D 50 is preferably more than 5 μm and less than 20 μm, more preferably 10 - 15 μm. The D 50 The 50% cumulative volume particle size obtained from the cumulative particle size distribution curve of the volume standard measured by the laser diffraction scattering method.

[0122] D 50 LiMO satisfying the above range means that crystal growth progresses. In such LiMO, a large amount of surfaces where the deintercalation and intercalation of lithium ions proceed well are exposed, and the deintercalation and intercalation of lithium ions proceed smoothly, so the rate performance is easily improved.

[0123] [D 50 Measurement method]

[0124] In this specification, the D of LiMO 50 can be measured by the following method.

[0125] First, 2 g of powdery LiMO is put into 50 ml of an aqueous solution of 0.2 mass% sodium hexametaphosphate to disperse LiMO and obtain a dispersion.

[0126] Next, for the obtained dispersion, the particle size distribution is measured using a laser diffraction particle size distribution analyzer to obtain a cumulative particle size distribution curve on a volume basis. Then, in the obtained cumulative particle size distribution curve, the value of the particle diameter when 50% is accumulated from the fine particle side is D 50 (μm).

[0127] As the laser diffraction particle size distribution analyzer, for example, MS2000 manufactured by Malvern can be used.

[0128] LiMO preferably has a peak showing the maximum heat release amount at 400 °C or higher in the differential thermal - thermogravimetric simultaneous analysis. The peak temperature showing the maximum heat release amount is more preferably 400 - 500 °C, and further preferably 400 - 450 °C. If the peak temperature showing the maximum heat release amount is in the above range, the rate performance of the lithium secondary battery is easily improved. It should be noted that the peak showing the maximum heat release amount refers to the peak with the highest peak height in the DTA curve described later. The differential thermal - thermogravimetric simultaneous analysis of LiMO is carried out by the following method.

[0129] [Method of differential thermal - thermogravimetric simultaneous analysis]

[0130] As the measuring device for the differential thermal - thermogravimetric simultaneous analysis, STA7300 manufactured by Hitachi High - Tech Science Corporation can be used.

[0131] The weighing of the sample is carried out on the balance beam of STA7300.

[0132] Put about 5 mg of LiMO into a platinum measuring container, place it in the above-mentioned measuring device, and heat it at a rate of 5 °C / min under a nitrogen gas flow of 5 ml / min from 20 to 700 °C to obtain a DTA curve. Determine the peak showing the maximum heat release amount from the height of the peak of the obtained DTA curve. It should be noted that considering the measurement amount, heating rate, and measurement temperature range, the influence of the particle size on the weight reduction rate is very small, so the particle size of the sample is not limited in this embodiment.

[0133] <Manufacturing method of LiMO>

[0134] The manufacturing method of LiMO preferably includes a step of obtaining MCC and a step of obtaining LiMO. Hereinafter, the step of obtaining MCC and the step of obtaining LiMO will be described in sequence.

[0135] [Manufacturing process of MCC]

[0136] First, prepare MCC containing at least Ni.

[0137] MCC can be manufactured by the batch coprecipitation method or the continuous coprecipitation method. Hereinafter, taking a metal composite oxide containing Ni and the above element M2 as an example, its manufacturing method will be described in detail.

[0138] First, by the coprecipitation method, especially the continuous coprecipitation method described in JP-A-2002-201028, react a nickel salt solution, a metal salt solution containing element M2, and an optional complexing agent to manufacture Ni b M2 (1-b) (OH)2 (where b is the same as b in the above compositional formula (A)) representing a metal composite hydroxide.

[0139] As the nickel salt which is the solute of the above nickel salt solution, for example, one or more of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate can be used.

[0140] As the metal salt which is the solute of the metal salt solution containing element M2, sulfates, chlorides, acetates, hydroxide salts, etc. of element M2 can be cited.

[0141] As the cobalt salt which is the solute of the cobalt salt solution, for example, one or more of cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate can be used.

[0142] As the manganese salt which is the solute of the manganese salt solution, for example, one or more of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate can be used.

[0143] As the aluminum salt which is the solute of the aluminum salt solution, for example, aluminum sulfate, sodium aluminate, etc. can be used.

[0144] The above metal salts are in the same ratio as the above Ni b M2 (1-b) It is used in a proportion corresponding to the composition ratio of (OH)2. In addition, water is used as the solvent.

[0145] The complexing agent is a compound that can form a complex with nickel ions and ions of element M2 in an aqueous solution. Examples thereof include ammonium ion donors, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine.

[0146] Examples of the ammonium ion donor include ammonium salts such as ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride.

[0147] The complexing agent may also be absent. When the complexing agent is included, the amount of the complexing agent contained in the nickel salt solution, the metal salt solution containing element M2, and the solution containing the complexing agent is, for example, greater than 0 and 2.0 or less in terms of the molar ratio to the total number of moles of the metal salts contained in the solution.

[0148] In the coprecipitation method, in order to adjust the pH value of the above solution, an alkaline aqueous solution is added to the solution before the pH of the solution changes from alkaline to neutral. As the alkaline aqueous solution, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution can be used.

[0149] It should be noted that the pH value in this specification is defined as the value measured when the temperature of the solution is 40°C. When the temperature of the solution sampled from the reaction tank is higher or lower than 40°C, the pH of the solution is measured when the solution is heated or cooled to reach 40°C.

[0150] During the reaction, the temperature of the reaction tank is controlled within a range of, for example, 20 to 80°C, preferably 30 to 70°C.

[0151] In addition, during the reaction, the pH value of the solution in the reaction tank is controlled within a range of, for example, 9 to 13, preferably 11 to 13.

[0152] The substances in the reaction tank are appropriately stirred and mixed.

[0153] As the reaction tank used in the continuous coprecipitation method, a reaction tank of the type that overflows to separate the formed reaction precipitate can be used.

[0154] In order to control the reaction tank to the target atmosphere, it is only necessary to introduce a specified gas into the reaction tank or directly bubble the reaction solution.

[0155] After the above reaction, if the obtained reaction precipitate is washed with water, dehydrated, separated, and dried, a metal composite hydroxide is obtained. In addition, if necessary, the reaction precipitate can also be washed with weak acid water or an alkaline solution containing sodium hydroxide or potassium hydroxide.

[0156] After drying the metal composite hydroxide, classification can also be appropriately performed.

[0157] The obtained metal composite hydroxide is oxidized (oxidation step) to obtain MCC as a metal composite oxide. By using the metal composite oxide, the Me site occupancy of the obtained LiMO can be adjusted to the range of the present embodiment.

[0158] The oxidation time is preferably set so that the total time from the start of heating to the end of temperature holding after reaching the temperature is 2 to 10 hours.

[0159] The oxidation temperature is preferably set to 500 to 800 °C.

[0160] In the oxidation step, various gases such as inert gases such as nitrogen, argon, and carbon dioxide, oxidizing gases such as air and oxygen, or a mixed gas thereof can be supplied into the reaction tank to control the oxidation state of the metal composite oxide.

[0161] In addition, in the oxidation step, oxidants such as peroxides such as hydrogen peroxide, peroxide salts such as permanganates, perchlorates, hypochlorites, nitric acid, halogens, and ozone can also be used.

[0162] By appropriately adjusting the manufacturing conditions of MCC, the D of the obtained LiMO 50 can be adjusted to the range of the present embodiment.

[0163] [Process for obtaining LiMO]

[0164] The process for obtaining LiMO includes a mixing step of mixing MCC, a lithium compound, and a compound containing element M1, and a firing step of firing the obtained mixture.

[0165] · Mixing step

[0166] MCC, a lithium compound, and a compound containing element M1 are mixed.

[0167] As the above lithium compound, at least one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, lithium oxide, lithium chloride, and lithium fluoride can be used. Among them, any one or a mixture of lithium hydroxide, lithium hydroxide hydrate, and lithium carbonate is preferred.

[0168] The compound containing element M1 is preferably a hydroxide, and for example, at least one of barium hydroxide, calcium hydroxide, magnesium hydroxide, strontium hydroxide, and radium hydroxide can be used. The compound containing element M1 is preferably a compound mainly containing element M1, and "mainly containing element M1" means that element M1 is contained in an amount exceeding 50 mass% relative to the total amount of the compound containing element M1.

[0169] The particle size calculated from the BET specific surface area of the compound containing element M1 is preferably 2000 nm or less. In addition, the particle size calculated from the BET specific surface area is preferably 200 nm or more.

[0170] [Measurement of the particle size of the compound containing element M1]

[0171] The particle size calculated from the BET specific surface area of the compound containing element M1 can be determined by the following method.

[0172] First, in a nitrogen atmosphere, after drying the compound containing element M1 at 105 °C for 30 minutes, it can be measured using a BET specific surface area measuring device. As the BET specific surface area measuring device, for example, Macsorb (registered trademark) manufactured by Mountech Co., Ltd. can be used.

[0173] From the obtained BET specific surface area, the particle size is calculated using the following formula.

[0174] Particle size (nm) = 6 / (S × P) (formula)

[0175] In the formula, P is the density (g / m 3 ) of the compound containing element M1, and S is the BET specific surface area (m 2 / g) of the compound containing element M1.

[0176] The lithium compound and MCC are mixed in consideration of the composition ratio of the final target product to obtain a mixture of the lithium compound and MCC. The amount of Li contained in the lithium compound is preferably 0.90 to 1.10, more preferably 0.91 to 1.10, and further preferably 0.92 to 1.10 with respect to the total amount 1 (molar ratio) of elements other than oxygen atoms (such as Ni, element M1, and element M2) contained in MCC.

[0177] The compound containing element M1 is mixed in a proportion such that the element M1 contained in the compound containing element M1 preferably exceeds 0 mol% and is 5 mol% or less, more preferably exceeds 0 mol% and is 2 mol% or less, with respect to the total number of moles of elements other than oxygen atoms (such as Ni, element M1, and element M2) contained in MCC. The larger the atomic number of the element in the periodic table, the smaller the proportion of element M1 is preferably.

[0178] When the compound containing element M1 is a compound mainly containing Mg, it is mixed in a proportion such that the Mg contained in the compound containing Mg preferably exceeds 0.3 mol% and is less than 1 mol%, more preferably 0.3 to 0.9 mol%, with respect to the total number of moles of elements other than oxygen atoms contained in MCC.

[0179] When the compound containing element M1 is a compound mainly containing Ca, it is preferably mixed in a proportion such that the molar ratio of Ca contained in the Ca-containing compound to the total molar amount of elements other than oxygen atoms contained in MCC is 0.1 to 2 mol%, more preferably 0.3 to 1.5 mol%.

[0180] When the compound containing element M1 is a compound mainly containing Ba, it is preferably mixed in a proportion such that the molar ratio of Ba contained in the Ba-containing compound to the total molar amount of elements other than oxygen atoms contained in MCC exceeds 0.5 mol% and is 5 mol% or less, more preferably 0.6 to 5 mol%.

[0181] By controlling the particle size of the compound containing element M1, the addition amount of the compound containing element M1, the addition amount of the lithium compound, and the firing conditions described below, the present invention can manufacture LiMO satisfying (1) and (2). Further, by controlling these conditions, LiMO having a peak showing the maximum heat release amount at 400 °C or higher in the simultaneous differential thermal-thermogravimetric analysis can be manufactured.

[0182] · Firing process

[0183] The mixture of MCC, lithium compound, and the compound containing element M1 is fired to obtain LiMO. If firing is carried out in the presence of the compound containing element M1, sintering is promoted, and LiMO satisfying (2) is obtained. For firing, dry air, an oxygen atmosphere, an inert atmosphere, etc. are used according to the desired composition. In the present embodiment, firing is preferably carried out in an oxygen atmosphere.

[0184] The firing process can be a single firing or can have multiple firing stages.

[0185] In the case of having multiple firing stages, the process of firing at the highest temperature is recorded as the formal firing. It is also possible to carry out a preliminary firing at a temperature lower than the formal firing before the formal firing.

[0186] In the present embodiment, it is preferable to first carry out the preliminary firing and then carry out the formal firing. In addition, both the preliminary firing and the formal firing are preferably carried out in an oxygen atmosphere.

[0187] The firing temperature during the preliminary firing is preferably 600 to 900 °C, more preferably 610 to 850 °C, and further preferably 620 °C or higher and lower than 700 °C. If the firing temperature is within the above range, LiMO satisfying (1) and (2) can be manufactured.

[0188] The firing temperature during formal firing is preferably 600 to 900 °C, more preferably 650 to 850 °C, and further preferably 700 to 820 °C. If the firing temperature is within the above range, LiMO satisfying (1) and (2) can be manufactured.

[0189] The holding time during temporary firing and formal firing is preferably 1 to 50 hours, more preferably 2 to 20 hours. If the holding time is within the above range, LiMO satisfying (1) and (2) can be manufactured.

[0190] The firing temperature in this specification refers to the temperature of the atmosphere in the firing furnace and is the maximum temperature. Examples of the firing furnace used include a continuous firing furnace or a fluidized firing furnace. Examples of the continuous firing furnace include a tunnel furnace or a roller hearth furnace. Examples of the fluidized firing furnace include a rotary furnace.

[0191] By adjusting the firing conditions in the firing process, the BET specific surface area of LiMO can be adjusted to the range of this embodiment.

[0192] Through the above process, LiMO is obtained.

[0193] <cam>

[0194] The CAM of this embodiment contains LiMO manufactured by the above method. In the CAM, the content ratio of the above LiMO relative to the total mass (100% by mass) of the CAM is preferably 70 to 99% by mass, more preferably 80 to 98% by mass.

[0195] The content ratio of LiMO relative to the total mass of the CAM is determined by performing SEM observation on the CAM by irradiating electron rays with an acceleration voltage of 20 kV using SEM (for example, JSM-5510 manufactured by JEOL Ltd.). The magnification of the SEM photograph is adjusted so that there are 200 to 400 CAM particles as objects in the SEM photograph. As an example, the magnification can also be 1000 to 30000 times.

[0196] <Lithium secondary battery>

[0197] The positive electrode for a lithium secondary battery that is preferable when using the above LiMO as the CAM will be described. Hereinafter, the positive electrode for a lithium secondary battery may sometimes be referred to as the positive electrode.

[0198] Furthermore, a lithium secondary battery that is preferable for use as the positive electrode will be described.

[0199] An example of a preferable lithium secondary battery in the case of using the above LiMO as the CAM has a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode.

[0200] Figure 1 It is a schematic diagram showing an example of a lithium secondary battery. For example, a cylindrical lithium secondary battery 10 is manufactured as follows.

[0201] First, as Figure 1 shown in the partial enlarged view of, an electrode group 4 is formed by laminating and winding a pair of belt-shaped separators 1, a belt-shaped positive electrode 2 having a positive electrode lead 21 at one end, and a belt-shaped negative electrode 3 having a negative electrode lead 31 at one end in the order of separator 1, positive electrode 2, separator 1, negative electrode 3.

[0202] As an example, the positive electrode 2 has a positive electrode active material layer 2a containing CAM and a positive electrode current collector 2b having the positive electrode active material layer 2a formed on one side. Such a positive electrode 2 can be manufactured by first preparing a positive electrode mixture containing CAM, a conductive material, and a binder, and forming the positive electrode active material layer 2a by supporting the positive electrode mixture on one side of the positive electrode current collector 2b.

[0203] As an example, the negative electrode 3 may include an electrode in which a negative electrode mixture containing a negative electrode active material (not shown) is supported on a negative electrode current collector, and an electrode composed of only the negative electrode active material, and can be manufactured by the same method as the positive electrode 2.

[0204] Next, after the electrode group 4 and an insulator (not shown) are housed in the battery can 5, the bottom of the can is sealed, the electrolyte 6 is impregnated into the electrode group 4, and an electrolyte is disposed between the positive electrode 2 and the negative electrode 3. Further, by sealing the upper part of the battery can 5 with the top insulator 7 and the sealing body 8, the lithium secondary battery 10 can be manufactured.

[0205] As the shape of the electrode group 4, for example, a columnar shape can be cited in which the cross-sectional shape when the electrode group 4 is cut along a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners.

[0206] In addition, as the shape of the lithium secondary battery having such an electrode group 4, the shapes specified in IEC60086 or JIS C 8500, which are standards for batteries specified by the International Electrotechnical Commission (IEC), can be adopted. For example, shapes such as a cylindrical shape or a square shape can be cited.

[0207] Furthermore, the lithium secondary battery is not limited to the above-described wound type configuration, and may also be a stacked type configuration in which a stacked structure of a positive electrode, a separator, a negative electrode, and a separator is repeatedly stacked. As examples of the stacked type lithium secondary battery, so-called coin type batteries, button type batteries, or paper type (or sheet type) batteries can be cited.

[0208] For the positive electrode, separator, negative electrode, and electrolyte constituting the lithium secondary battery, for example, the configurations, materials, and manufacturing methods described in

[0113] to

[0140] of WO2022 / 113904A1 can be used.

[0209] <All-solid-state lithium secondary battery>

[0210] The above LiMO can be used as the CAM of an all-solid-state lithium secondary battery.

[0211] Figure 2 is a schematic diagram showing an example of an all-solid-state lithium secondary battery. Figure 2 The all-solid-state lithium secondary battery 1000 shown in has a laminate 100 including a positive electrode 110, a negative electrode 120, and a solid electrolyte layer 130, and an outer package 200 housing the laminate 100. In addition, the all-solid-state lithium secondary battery 1000 may also have a bipolar structure in which a CAM and a negative electrode active material are disposed on both sides of the current collector. As a specific example of the bipolar structure, for example, the structure described in JP-A-2004-95400 can be cited.

[0212] The positive electrode 110 has a positive electrode active material layer 111 and a positive electrode current collector 112. The positive electrode active material layer 111 contains the above-mentioned CAM and a solid electrolyte. In addition, the positive electrode active material layer 111 may also contain a conductive material and a binder.

[0213] The negative electrode 120 has a negative electrode active material layer 121 and a negative electrode current collector 122. The negative electrode active material layer 121 contains a negative electrode active material. In addition, the negative electrode active material layer 121 may also contain a solid electrolyte and a conductive material.

[0214] The laminate 100 may also have an external terminal 113 connected to the positive electrode current collector 112 and an external terminal 123 connected to the negative electrode current collector 122. In addition, the all-solid-state lithium secondary battery 1000 may also have a separator between the positive electrode 110 and the negative electrode 120.

[0215] The all-solid-state lithium secondary battery 1000 further has an insulator (not shown) that insulates the laminate 100 from the outer package 200 and a sealing body (not shown) that seals the opening 200a of the outer package 200.

[0216] As the outer package 200, a container formed by shaping a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel can be used. In addition, as the outer package 200, a container obtained by processing a laminated film having corrosion-resistant processing applied to at least one surface into a bag shape can also be used.

[0217] Examples of the shape of the all-solid-state lithium secondary battery 1000 include a coin shape, a button shape, a paper shape (or sheet shape), a cylindrical shape, a square shape, or a laminated shape (bag shape).

[0218] For the all-solid-state lithium secondary battery 1000, a form having one laminate 100 is illustrated as an example, but the present embodiment is not limited thereto. The all-solid-state lithium secondary battery 1000 may also have a configuration in which the laminate 100 is used as a unit cell and a plurality of unit cells (laminates 100) are sealed inside the outer package 200.

[0219] For the all-solid-state lithium secondary battery, for example, the configuration, materials, and manufacturing method described in

[0141] to

[0181] of WO2022 / 113904A1 can be used.

[0220] Examples

[0221] Next, the present invention will be further described in detail by way of examples.

[0222] <Measurement of various parameters>

[0223] The measurement of various parameters of LiMO produced by the method described below is carried out as described in the above [Method for Measuring Me Site Occupancy], [Composition Analysis], [Method for Measuring Particle Strength], [BET Specific Surface Area Measurement], [Method for Simultaneous Differential Thermal-Thermogravimetric Analysis], and [D 50 The particle sizes of barium hydroxide, calcium hydroxide, and magnesium hydroxide calculated from the BET specific surface area are measured as described in the above [Measurement of Particle Size of Compound Containing Element M1].

[0224] <Method for Measuring Rate Performance>

[0225] The rate performance of the lithium secondary battery is evaluated using LiMO obtained by the manufacturing method described below as the CAM, and is carried out as described in the above [Measurement of Rate Performance].

[0226] <Example 1>

[0227] After adding water into a reaction tank equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution is added, and the liquid temperature (temperature of the reaction tank) is maintained at 70 °C.

[0228] An aqueous nickel sulfate solution, an aqueous manganese sulfate solution, and an aqueous aluminum sulfate solution are mixed in a ratio such that the molar ratio of Ni:Mn:Al is 93:3.5:3.5 to prepare a mixed solution 1.

[0229] Under a nitrogen flow, the mixed solution 1 and an aqueous ammonium sulfate solution as a complexing agent are continuously added to the reaction tank with stirring. An aqueous sodium hydroxide solution is added dropwise as appropriate so that the pH of the solution in the reaction tank becomes 10.7 (measurement temperature: 40 °C) to obtain a reaction precipitate 1.

[0230] Using 20 times the mass of a 5 mass% aqueous sodium hydroxide solution with respect to the mass of the reaction precipitate 1, the reaction precipitate 1 is washed. After washing, dehydration is carried out using a centrifuge, and further washing, dehydration, and separation are carried out with water, and drying is carried out at 105 °C for 20 hours to obtain a metal composite hydroxide 1 containing Ni, Mn, and Al.

[0231] The metal composite hydroxide 1 is oxidized at 650 °C for 5 hours in an air atmosphere to obtain MCC-1 as a metal composite oxide.

[0232] Lithium hydroxide monohydrate is weighed in a ratio such that the amount of Li is 1.02 with respect to the total amount of Ni, Mn, and Al contained in MCC-1 (molar ratio).

[0233] Barium hydroxide is weighed in a ratio such that the amount of Ba is 5.0 mol% with respect to the total amount of Ni, Mn, and Al contained in MCC-1.

[0234] Mix MCC-1, lithium hydroxide monohydrate, and barium hydroxide to obtain Mixture 1. The particle size of the barium hydroxide used, calculated from the BET specific surface area, is 1202 nm.

[0235] Next, subject the obtained Mixture 1 to a preliminary firing at 650 °C for 5 hours in an oxygen atmosphere. Thereafter, conduct a full firing at 770 °C for 5 hours in an oxygen atmosphere to obtain powdered LiMO-1.

[0236] <Example 2>

[0237] Manufacture MCC-1 in the same manner as in Example 1.

[0238] Weigh lithium hydroxide monohydrate such that the amount of Li is 1.03 (molar ratio) relative to the total amount of Ni, Mn, and Al contained in MCC-1.

[0239] Weigh calcium hydroxide such that the amount of Ca is 1.0 mol% relative to the total amount of Ni, Mn, and Al contained in MCC-1.

[0240] Mix MCC-1, lithium hydroxide monohydrate, and calcium hydroxide to obtain Mixture 2. The particle size of the calcium hydroxide used, calculated from the BET specific surface area, is 690 nm.

[0241] Subject Mixture 2 to a preliminary firing at 650 °C for 5 hours in an oxygen atmosphere. Thereafter, conduct a full firing at 750 °C for 5 hours in an oxygen atmosphere to obtain powdered LiMO-2.

[0242] <Example 3>

[0243] Manufacture MCC-1 in the same manner as in Example 1.

[0244] Weigh lithium hydroxide monohydrate such that the amount of Li is 1.03 (molar ratio) relative to the total amount of Ni, Mn, and Al contained in MCC-1.

[0245] Weigh magnesium hydroxide such that the amount of Mg is 0.3 mol% relative to the total amount of Ni, Mn, and Al contained in MCC-1.

[0246] Mix MCC-1, lithium hydroxide monohydrate, and magnesium hydroxide to obtain Mixture 3. The particle size of the magnesium hydroxide used, calculated from the BET specific surface area, is 980 nm.

[0247] Fire Mixture 3 under the same firing conditions as in Example 2 to obtain powdered LiMO-3.

[0248] <Comparative Example 1>

[0249] Manufacture MCC-1 in the same manner as in Example 1.

[0250] Weigh lithium hydroxide monohydrate such that the amount of Li is 1.02 with respect to the total amount of Ni, Mn, and Al contained in MCC-1 (molar ratio).

[0251] Mix MCC-1 and lithium hydroxide monohydrate to obtain Mixture 4.

[0252] Fire Mixture 4 under the same firing conditions as in Example 1 to obtain powdery LiMO-4.

[0253] <Comparative Example 2>

[0254] Manufacture MCC-1 in the same manner as in Example 1.

[0255] Weigh lithium hydroxide monohydrate such that the amount of Li is 1.02 with respect to the total amount of Ni, Mn, and Al contained in MCC-1 (molar ratio).

[0256] Weigh barium hydroxide such that the amount of Ba is 0.5 mol% with respect to the total amount of Ni, Mn, and Al contained in MCC-1.

[0257] Mix MCC-1, lithium hydroxide monohydrate, and barium hydroxide to obtain Mixture 5. The particle size of the barium hydroxide used, calculated from the BET specific surface area, is 1202 nm.

[0258] Fire Mixture 5 under the same conditions as in Example 1 to obtain powdery LiMO-5.

[0259] <Comparative Example 3>

[0260] Manufacture MCC-1 in the same manner as in Example 1.

[0261] Weigh lithium hydroxide monohydrate such that the amount of Li is 1.02 with respect to the total amount of Ni, Mn, and Al contained in MCC-1 (molar ratio).

[0262] Weigh magnesium hydroxide such that the amount of Mg is 1.0 mol% with respect to the total amount of Ni, Mn, and Al contained in MCC-1.

[0263] Mix MCC-1, lithium hydroxide monohydrate, and magnesium hydroxide to obtain Mixture 6. The particle size of the magnesium hydroxide used, calculated from the BET specific surface area, is 980 nm.

[0264] Fire Mixture 6 under the same conditions as in Example 2 to obtain powdery LiMO-6.

[0265] <Comparative Example 4>

[0266] Manufacture MCC-1 in the same manner as in Example 1.

[0267] Weigh lithium hydroxide monohydrate such that the amount of Li is 1.09 with respect to the total amount of Ni, Mn, and Al contained in MCC-1 (molar ratio).

[0268] Mix MCC-1 and lithium hydroxide monohydrate to obtain Mixture 7.

[0269] Fire Mixture 7 under the same conditions as in Example 2 to obtain powdery LiMO-7.

[0270] <Comparative Example 5>

[0271] Manufacture MCC-1 in the same manner as in Example 1.

[0272] Weigh lithium hydroxide monohydrate such that the amount of Li is 1.02 with respect to the total amount of Ni, Mn, and Al contained in MCC-1 (molar ratio).

[0273] Weigh barium hydroxide such that the amount of Ba is 5.0 mol% with respect to the total amount of Ni, Mn, and Al contained in MCC-1.

[0274] Mix MCC-1, lithium hydroxide monohydrate, and barium hydroxide to obtain Mixture 8. The particle size of the barium hydroxide used, calculated from the BET specific surface area, is 2106 nm.

[0275] Fire Mixture 8 under the same conditions as in Example 2 to obtain powdery LiMO-8.

[0276] The various parameters of LiMO obtained in Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1. In addition, the results of the rate characteristics of lithium secondary batteries using LiMO obtained in Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1. In Table 1 below, the "content ratio of element M1 (%)" is the content ratio of element M1 with respect to the total number of moles of Ni, Mn, Al, and element M1 constituting LiMO.

[0277]

[0278] The rate characteristics of lithium secondary batteries using LiMO of Examples 1 to 3 that satisfy (1) and (2) are 80% or more. It is considered that this is because: cracks are less likely to occur during electrode manufacturing, and sufficient capacity is maintained.

[0279] It is considered that in Comparative Example 1, since it does not contain element M1 and the occupancy rate of the Me position exceeds 4.0%, the capacity is likely to decrease. Since the particle strength is 100 MPa or less, cracks are generated during electrode manufacturing, and as a result, the rate performance is low.

[0280] It is considered that although Comparative Examples 2 to 3 and 5 satisfy (2), since the occupancy rate of the Me position exceeds 4.0%, the capacity is likely to decrease, and as a result, the rate performance is low.

[0281] It is considered that although Comparative Example 4 satisfies (2), since it does not contain element M1 and the particle strength is also 100 MPa or less, cracks are generated during electrode manufacturing, and as a result, the rate performance is low.

[0282] Explanation of symbols

[0283] 1: separator, 2... positive electrode, 2a... positive electrode active material layer, 2b... positive electrode current collector, 3: negative electrode, 4: electrode group, 5: battery can, 6: electrolyte, 7: top insulator, 8: sealing body, 10: lithium secondary battery, 21: positive electrode lead, 100: laminate, 110: positive electrode, 111: positive electrode active material layer, 112: positive electrode current collector, 113: external terminal, 120: negative electrode, 121: negative electrode active material layer, 122: negative electrode current collector, 123: external terminal, 130: solid electrolyte layer, 200: outer packaging body, 200a: opening, 1000: all-solid-state lithium secondary battery< / cam> < / limo>

Claims

1. A lithium metal composite oxide, which contains at least Li, Ni, and an element M1 as an alkaline earth metal element, and satisfies the following (1) and (2). (1) The occupancy of the Me position in the lithium site of the layered rock salt-type crystal structure, obtained by Rietveld analysis of the diffraction peaks obtained by powder X-ray diffraction using CuKα radiation, is 4.0% or less. (2) The particle strength of the lithium metal composite oxide exceeds 100 MPa and is less than 200 MPa.

2. The lithium metal composite oxide according to claim 1, which is represented by the following compositional formula (A). Li a Ni b M1 c M2 (1-b-c) O2(A) The compositional formula (A) satisfies 0.98 ≤ a ≤ 1.10, 0.60 ≤ b ≤ 0.95, and 0 < c ≤ 0.

05. M1 is the element M1, and M2 is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Al, Zn, Sn, Zr, B, Si, Nb, W, Mo, Ta, S, and P.

3. The lithium metal composite oxide according to claim 1 or 2, wherein The content ratio of the element M1 contained in the lithium metal composite oxide is greater than 0 mol% and 5 mol% or less with respect to the total molar amount of the elements other than Li and oxygen atoms constituting the lithium metal composite oxide.

4. The lithium metal composite oxide according to claim 1 or 2 has a BET specific surface area of less than 1.0 m 2 / g.

5. The lithium metal composite oxide according to claim 1 or 2, wherein the 50% cumulative volume particle size D obtained from the cumulative particle size distribution curve based on volume measured by the laser diffraction scattering method 50 exceeds 5 μm and is less than 20 μm.

6. The lithium metal composite oxide according to claim 1 or 2, wherein In the differential thermal-thermogravimetric simultaneous analysis, there is a peak showing the maximum heat release amount at 400 °C or higher.

7. A positive electrode active material for a lithium secondary battery, wherein, It contains the lithium metal composite oxide according to claim 1 or 2.

8. A positive electrode for a lithium secondary battery, which contains the positive electrode active material for a lithium secondary battery according to claim 7.

9. A lithium secondary battery, which contains the positive electrode for a lithium secondary battery according to claim 8.

Images