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

Abstract

The present invention aims to provide a lithium metal composite oxide that, when used as a positive electrode active material for lithium-ion batteries, enables the production of lithium-ion batteries with high cycle retention, as well as a positive electrode active material for lithium-ion batteries, a positive electrode for lithium-ion batteries, and a lithium-ion battery using the same. The lithium metal composite oxide is a particulate lithium metal composite oxide comprising a first particle with a particle size of 50% or less of the cumulative volume particle size D50 of the lithium metal composite oxide, and a second particle with a particle size exceeding D50, wherein D50 is 2-20 μm, and the average particle strength P of the first particle is... S The average particle strength P of the second particle mentioned above is greater than that of the first particle. B The standard deviation σ of the particle intensity of the first particle mentioned above S The standard deviation σ of the particle intensity of the second particle mentioned above is greater than that of the second particle. B .

Description

Technical Field

[0001] This invention relates to lithium metal composite oxides, positive electrode active materials for lithium secondary batteries, positive electrodes for lithium secondary batteries, and lithium secondary batteries.

[0002] This application claims priority based on Japanese Patent Application No. 2021-015685 filed on February 3, 2021, the contents of which are incorporated herein by reference. Background Art

[0003] A lithium-ion secondary battery has a positive electrode containing a positive electrode active material. Lithium metal composite oxide is used as the positive electrode active material.

[0004] Lithium metal composite oxides contain aggregates of primary particles, i.e., secondary particles. Because lithium ion insertion and extraction reactions occur on the surface of lithium metal composite oxides, their properties affect various performance characteristics of lithium-ion secondary batteries. Therefore, with the aim of improving the performance of lithium-ion secondary batteries, efforts have been made to actively control various properties of lithium metal composite oxides.

[0005] For example, attempts have been made to control the pore distribution and specific surface area of ​​lithium metal composite oxides. Patent Document 1 describes a positive electrode active material for a non-aqueous electrolyte secondary battery, in which the average volume of pores with an average diameter of less than 40 nm was measured using a nitrogen adsorption method, and the average volume was 0.001–0.008 cm³. 3 / g.

[0006] In addition, attempts were made to control the strength of lithium metal composite oxides. Patent document 2 discloses that the positive electrode active material for lithium secondary batteries is formed from secondary particles, and the average compressive strength of the secondary particles is less than 110 MPa.

[0007] Existing technical documents

[0008] Patent Literature

[0009] Patent Document 1: JP-A-2007-257985

[0010] Patent Document 2: JP-A-2004-335152 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] When using lithium metal composite oxides as the positive electrode active material in lithium-ion secondary batteries, small particles may crack during the electrode pressing process, creating voids in the layer containing the positive electrode active material. This can result in poor contact between the positive electrode and the layer containing the positive electrode active material, leading to a decrease in the cycle characteristics of the lithium-ion secondary battery. To date, no efforts have been made to improve the characteristics of lithium metal composite oxides from this perspective.

[0013] The present invention was made in view of the above circumstances, and the object is to provide a lithium metal composite oxide that, when used as a positive electrode active material for lithium secondary batteries, can produce a lithium secondary battery with a high cycle retention rate, as well as a positive electrode active material for lithium secondary batteries, a positive electrode for lithium secondary batteries, and a lithium secondary battery using the same.

[0014] Methods for solving problems

[0015] The present invention has the following solution.

[0016] [1] A lithium metal composite oxide, which is a particulate lithium metal composite oxide comprising a cumulative volume particle size D of 50% of the aforementioned lithium metal composite oxide. 50 The following first particles and particles with a diameter exceeding D above 50 The second particle, the aforementioned D 50 The average particle intensity P of the first particle is 2-20 μm. S The average particle intensity P of the second particle mentioned above is greater than that of the first particle. B The standard deviation σ of the particle intensity of the first particle mentioned above S The standard deviation σ of the particle intensity of the second particle mentioned above is greater than that of the second particle. B .

[0017] [2] According to the lithium metal composite oxide described in [1], wherein the above-mentioned P S With the above P B The difference is P S -P B It is above 15 MPa.

[0018] [3] The lithium metal composite oxide according to [1] or [2], wherein the above σ S With the above σ B The difference is σ S -σ B It is above 5 MPa.

[0019] [4] The lithium metal composite oxide according to any one of [1] to [3], wherein the above-mentioned P S It is 50-110 MPa.

[0020] [5] The lithium metal composite oxide according to any one of [1] to [4], wherein the above-mentioned PB It is 20-60 MPa.

[0021] [6] The lithium metal composite oxide according to any one of [1] to [5], wherein the above σ S It ranges from 20 to 90 MPa.

[0022] [7] The lithium metal composite oxide according to any one of [1] to [6], wherein the above σ B It is 10-30 MPa.

[0023] [8] The lithium metal composite oxide according to any one of [1] to [7] has a BET specific surface area of ​​0.1-2.0 m². 2 / g.

[0024] [9] The lithium metal composite oxide according to any one of [1] to [8] is represented by the composition formula (I).

[0025] Li[Li x (Ni (1-y-z) CO y X z ) 1-x O2 (I)

[0026] (In formula (I), X represents one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, Si, S and P, and satisfying -0.1≤x≤0.2, 0≤y≤0.4 and 0<z≤0.5.)

[0027]

[10] The lithium metal composite oxide according to [9], wherein the above composition formula (I) satisfies 0<y+z≤0.3.

[0028]

[11] A positive electrode active material for lithium secondary batteries, which contains any one of [1] to

[10] lithium metal composite oxide.

[0029]

[12] A positive electrode for a lithium secondary battery, comprising the positive electrode active material for a lithium secondary battery described in

[11] .

[0030]

[13] A lithium secondary battery having the positive electrode for a lithium secondary battery as described in

[12] .

[0031] Invention Effects

[0032] According to the present invention, a lithium metal composite oxide that can produce a lithium secondary battery with a high cycle retention rate when used as a positive electrode active material for a lithium secondary battery, as well as a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery using the same, are provided. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating a method for manufacturing lithium metal composite oxide in one embodiment of this invention.

[0034] Figure 2 This is a schematic diagram illustrating an example of a lithium secondary battery.

[0035] Figure 3 This is a schematic diagram showing the overall structure of the all-solid-state lithium secondary battery according to this embodiment.

[0036] Figure 4 This is a graph showing the relationship between particle size and particle strength of the lithium metal composite oxides of Example 1 and Comparative Example 1. Detailed Implementation

[0037] The following describes a lithium metal composite oxide according to one aspect of the present invention. Preferred embodiments and conditions may also be common in the following various embodiments. Furthermore, the following definitions apply to various terms in this specification.

[0038] In this application specification, the metal composite compound is referred to as "MCC", the lithium metal composite oxide is referred to as "LiMO", and the cathode active material for lithium secondary batteries is referred to as "CAM".

[0039] "Ni" does not refer to nickel metal, but rather to nickel atoms. Similarly, "Co" and "Li" refer to cobalt atoms and lithium atoms, respectively.

[0040] When a numerical range is described as, for example, "1-10μm" or "1~10μm", it refers to the range from 1μm to 10μm, and includes the lower limit of 1μm and the upper limit of 10μm.

[0041] "BET surface area" is a value determined using the BET (Brunauer, Emmett, Teller) method. Nitrogen gas is used as the adsorbent gas in the determination of BET surface area. For example, 1g of the powder to be measured can be dried in a nitrogen atmosphere at 105°C for 30 minutes, and then measured using a BET surface area meter (e.g., Mounttech, Macsorb (registered trademark)). (Unit: m²) 2 / g).

[0042] <Methods for determining cumulative particle size distribution>

[0043] "Cumulative volumetric particle size" is a value determined by laser diffraction scattering. Specifically, 0.1 g of the test object, such as LiMO powder, is added to 50 mL of a 0.2% (w / w) sodium hexametaphosphate aqueous solution to obtain a dispersion containing the powder. Next, the particle size distribution of the obtained dispersion is measured using a laser diffraction particle size distribution measuring device (e.g., Microtrac MT3300EXII, manufactured by MicrotracBEL Co., Ltd.), obtaining a cumulative particle size distribution curve based on volume. In the obtained cumulative particle size distribution curve, the value of the particle size at 50% accumulation from the microparticle side is the 50% cumulative volumetric particle size (hereinafter, sometimes referred to as D). 50 (μm).

[0044] The composition of LiMO can be analyzed by the following methods. For example, LiMO can be dissolved in hydrochloric acid and then analyzed using an inductively coupled plasma atomic emission spectrometer (e.g., SII Nano Technology Co., Ltd., SPS3000).

[0045] "Cycle maintenance rate" refers to the ratio of the discharge capacity of a lithium secondary battery after repeated charge-discharge cycles under specific conditions to its initial discharge capacity.

[0046] In this specification, the value measured by conducting a test under the conditions shown below for 50 repeated charge-discharge cycles is defined as the cycle maintenance rate.

[0047] <Cyclic Test>

[0048] Test temperature: 25℃

[0049] Maximum charging voltage 4.3V, charging current 0.5CA, constant current and constant voltage charging.

[0050] Minimum discharge voltage 2.5V, discharge current 1CA, constant current discharge.

[0051] The discharge capacity of the first cycle is set as the initial cycle capacity. The value obtained by dividing the discharge capacity of the 50th cycle by the initial cycle capacity is calculated and set as the cycle maintenance rate (%).

[0052] <Lithium Metal Composite Oxides>

[0053] The LiMO in this embodiment is particulate LiMO, containing D particles with a particle size of the aforementioned LiMO. 50 The following first particles and particles with a diameter exceeding D above 50 The second particle, the aforementioned D 50The average particle intensity P of the first particle is 2-20 μm. S The average particle intensity P of the second particle mentioned above is greater than that of the first particle. B The standard deviation σ of the particle intensity of the first particle mentioned above S The standard deviation σ of the particle intensity of the second particle mentioned above is greater than that of the second particle. B .

[0054] In this embodiment, LiMO is an aggregate of multiple particles. In other words, in this embodiment, LiMO is in powder form. In this embodiment, the aggregate of multiple particles may contain only primary particles, only secondary particles, or a mixture of primary and secondary particles.

[0055] In this embodiment, "primary particles" refers to particles that do not have grain boundaries when observed using a scanning electron microscope or similar device at a field of view of 5,000x or higher and 20,000x or lower.

[0056] In this embodiment, "secondary particles" are particles condensed from the aforementioned primary particles. That is, secondary particles are condensations of primary particles.

[0057] In this specification, "particle size" refers to the particle size of secondary particles contained in LiMO, or the particle size of primary particles that exist independently of secondary particles.

[0058] The D of LiMO in this embodiment 50 The micrometer size is 2-20 μm, preferably 3-18 μm, more preferably 4-16 μm, and even more preferably 5-15 μm. If the D of LiMO... 50 A particle size of 2-20 μm increases the bulk density of LiMO. If such LiMO is used as a CAM (Conductive Alternating Cell), the LiMO packing density becomes higher. Therefore, the increased contact area between the LiMO in the cathode and the conductive material particles improves conductivity, reduces the DC resistance of the lithium-ion battery, and improves its cycle life.

[0059] In the LiMO of this embodiment, the particle size is D 50 The average particle intensity P of the first particle (hereinafter sometimes referred to as the first particle) S Larger than D 50 The average particle intensity P of the second particle (hereinafter sometimes referred to as the second particle) B The standard deviation σ of the particle intensity of the first particle S The standard deviation σ of the particle intensity higher than that of the second particle B .

[0060] Hereinafter, the average particle intensity P is sometimes referred to as... S Average particle intensity PB Standard deviation σ S and standard deviation σ B Recorded as "P" S “P” B “σ” S "and "σ B ".

[0061] In manufacturing electrodes (i.e., positive electrodes) that use LiMO as CAM, a pressing process is typically performed to form the CAM-containing layer at a high density. The manufacturing process that performs such pressing is referred to below as the "electrode pressing process".

[0062] If P that satisfies the above is used S 、P B σ S and σ B When LiMO is used as a CAM (Conductive Alginate), the first particle is less prone to cracking during the electrode pressing process. Therefore, voids caused by particle cracking are less likely to form, resulting in a higher cathode density and enabling good contact between the LiMO-containing CAM and the conductive material. Consequently, the cycle life of lithium-ion batteries can be improved.

[0063] P S Preferably, the pressure is 50-110 MPa, more preferably 53-105 MPa, and even more preferably 60-100 MPa. If the pressure is 50-110 MPa, the first particle is less likely to crack during the electrode pressing process in the manufacturing of the positive electrode.

[0064] P B Preferably 20-60 MPa, more preferably 30-55 MPa, and even more preferably 40-50 MPa. If P B If the pressure is 20-60 MPa, the second particle is less likely to crack during the electrode pressing process in the manufacturing of the positive electrode. If P B If the lower limit value is below the above value, voids caused by particle cracking are less likely to occur, resulting in a higher density of the obtained positive electrode and enabling good contact between the LiMO-containing CAM and the conductive material. As a result, the cycle retention rate of the lithium secondary battery can be improved. If P B If the upper limit is below the aforementioned value, then compared to the first particle, the second particle preferentially causes particle cracking. However, by entering the voids caused by particle cracking through the first particle, the density of the resulting positive electrode is increased, enabling good contact between the CAM containing LiMO and the conductive material. As a result, the cycle retention rate of the lithium secondary battery can be improved.

[0065] P S With P B The difference is P S -PB Preferably, it is 15 MPa or higher, more preferably 15-75 MPa, even more preferably 17-70 MPa, and particularly preferably 21-65 MPa. If P S -P B If the pressure is 15-75 MPa, the first particle is less likely to crack during the electrode pressing process in the manufacturing of the positive electrode.

[0066] σ S Preferably 20-90 MPa, more preferably 25-85 MPa, and even more preferably 30-85 MPa. If σ S If the pressure is 20-90 MPa, the first particle is less likely to crack during the electrode pressing process in the manufacturing of the positive electrode.

[0067] σ B The pressure is preferably 10-30 MPa, more preferably 13-28 MPa, and even more preferably 15-25 MPa. If it is 10-30 MPa, the first particle is less likely to crack during the electrode pressing process in the manufacturing of the positive electrode.

[0068] σ S With σ B The difference is σ S -σ B Preferably, it is 5 MPa or higher, more preferably 5-70 MPa, and even more preferably 7-70 MPa. If σ S -σ B If the pressure is 5-70 MPa, the first particle is less likely to crack during the electrode pressing process in the manufacturing of the positive electrode.

[0069] <Methods for determining average particle strength and standard deviation of particle strength>

[0070] P S 、P B σ S and σ B The measurements and calculations are performed as follows in this specification. First, 100 particles are randomly selected from LiMO. Using a micro compression testing machine (e.g., Shimadzu MCT-510), the particle size and breaking strength of the selected particles are measured. Here, the breaking strength Cs is calculated using the following formula (II). In formula (II), P is the test force (unit: N, the pressure at which the displacement becomes maximum when the test pressure is kept approximately constant while the test pressure is gradually increased), and d is the particle size (unit: mm, the average value obtained by measuring the diameter in the X and Y directions in the observation image of the micro compression testing machine).

[0071] Cs=2.8P / πd 2 (II)

[0072] Since particle strength is normalized by particle size, if all particles have the same composition, the particle strength is constant. On the other hand, if the particle strengths differ between particles, it can be said that the individual particles have different compositions.

[0073] P S P represents the average fracture strength of the first particle. B This represents the average fracture strength of the second particle.

[0074] σ S σ represents the standard deviation of the fracture strength of the first particle. B This represents the standard deviation of the fracture strength of the second particle.

[0075] Regarding the BET specific surface area of ​​LiMO, the preferred BET specific surface area is 0.1-2.0 m². 2 / g, more preferably 0.5-1.8m 2 / g, preferably 1.0-1.5m 2 / g. If the specific surface area of ​​BET is 0.1-2.0m². 2 A concentration of / g can suppress the reaction between the electrolyte and the surface of CAM containing LiMO. As a result, the cycle retention rate of lithium secondary batteries can be improved.

[0076] LiMO is a metal oxide containing at least Li and Ni, for example represented by formula (I).

[0077] Li[Li x (Ni (1-y-z) CO y X z ) 1-x O2 (I)

[0078] (In formula (I), X represents one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, Si, S and P, and satisfying -0.1≤x≤0.2, 0≤y≤0.2 and 0<z≤0.2.)

[0079] From the viewpoint of obtaining a lithium secondary battery with high cycle retention, x in the above formula (I) is -0.1 or more, more preferably -0.05 or more, and even more preferably more than 0. Furthermore, from the viewpoint of obtaining a lithium secondary battery with higher initial coulombic effect, x in the above formula (I) is 0.2 or less, preferably 0.08 or less, and more preferably 0.06 or less.

[0080] The upper and lower limits of x can be combined arbitrarily. For example, combinations can include x ranging from -0.1 to 0.2, exceeding 0 but below 0.2, from -0.05 to 0.08, exceeding 0 but below 0.06, etc.

[0081] From the viewpoint of obtaining a lithium secondary battery with low internal resistance, y in the above formula (I) is preferably greater than 0, more preferably 0.005 or more, and even more preferably 0.05 or more. y in the above formula (I) is 0.4 or less, preferably 0.35 or less, more preferably 0.33 or less, and even more preferably 0.30 or less.

[0082] The upper and lower limits of y can be combined arbitrarily. Examples of combinations include 0 to 0.4, values ​​greater than 0 but less than 0.35, 0.005 to 0.35, and 0.05 to 0.30.

[0083] From the viewpoint of obtaining a lithium secondary battery with high cycle retention, z in the above formula (I) is preferably 0.01 or more, more preferably 0.02 or more. Furthermore, z in the above formula (I) is 0.5 or less, preferably 0.45 or less, more preferably 0.40 or less.

[0084] The upper and lower limits of z can be combined arbitrarily. Examples of combinations include z being greater than 0 and below 0.4, 0.01 to 0.45, 0.02 to 0.40, etc.

[0085] In the above equation (I), it is preferable to satisfy 0<y+z≤0.3.

[0086] From the viewpoint of obtaining a lithium secondary battery with high cycle retention, X is preferably one or more metals selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, Si, S and P, and more preferably one or more metals selected from the group consisting of Mn, Al, W, B, Nb and Zr.

[0087] The crystal structure of LiMO is a layered structure, more preferably a hexagonal crystal structure or a monoclinic crystal structure.

[0088] The crystal structure of the hexagonal crystal form 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.

[0089] [[ID=***3]]In addition, the crystal structure of the monoclinic crystal 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.

[0090] Among them, in order to obtain a lithium secondary battery with a high discharge capacity, the crystal structure is particularly preferably a hexagonal crystal structure belonging to the space group R-3m or a monoclinic crystal structure belonging to C2 / m.

[0091] The crystal structure of LiMO can be confirmed by observing using a powder X-ray diffractometer (for example, UltimaIV manufactured by Rigaku Corporation).

[0092] As described above, when LiMO is used as CAM, the first particles are not easily cracked in the electrode pressing process performed during the manufacture of the positive electrode. Generally, when stress is externally applied to LiMO during the electrode pressing process, the internal voids present inside the particles are utilized to relieve the stress and prevent particle cracking. However, compared with large particles, small particles have fewer internal voids for relieving stress. Therefore, small particles tend to be easily cracked. However, as described above, since the first particles of LiMO in the present embodiment are not easily cracked, voids caused by particle cracking are not easily generated, and the contact between CAM and the positive electrode becomes good. As a result, the cycle characteristics of the lithium secondary battery are improved.

[0093] <Manufacturing method of LiMO>

[0094] Next, the manufacturing method of LiMO will be described. As the first method, the LiMO of the present embodiment can also simultaneously manufacture the first particles and the second particles. Hereinafter, the first method will be described.

[0095] The method for manufacturing LiMO includes the manufacture of MCC, the mixing of MCC and lithium compounds, the temporary calcination of the mixture of MCC and lithium compounds, and the calcination of the reactants obtained by the temporary calcination.

[0096] (1) Manufacturing of MCC

[0097] MCC can be any of metal complex hydroxides, metal complex oxides, and mixtures thereof. As an example, metal complex hydroxides and metal complex oxides contain Ni, Co, and element X in molar ratios expressed by the following formula (I'), and are represented by the following formula (I”).

[0098] Ni:Co:X=(1-yz):y:z (I')

[0099] Ni (1-y-z) CO y X z O α (OH) 2-β (I”)

[0100] (In equations (I') and (I”), X represents one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, Si, S, and P, satisfying 0 ≤ y ≤ 0.4 and 0 < z ≤ 0.5. Equation (I”) satisfies 0 ≤ α ≤ 3, -0.5 ≤ β ≤ 2, and β - α < 2.)

[0101] The following describes a method for manufacturing MCC containing Ni, Co, and Al as an example. First, a metal composite hydroxide containing Ni, Co, and Al is prepared. The metal composite hydroxide can be manufactured using either a batch co-precipitation method or a continuous co-precipitation method, which are generally known.

[0102] Specifically, Ni is produced by reacting nickel salt solution, cobalt salt solution, aluminum salt solution, and a complexing agent using the continuous co-precipitation method described in Japanese Patent Application Publication No. 2002-201028. (1-y-z) CO y Al z (OH)2 represents a metal complex hydroxide.

[0103] The solute used in the nickel salt solution, namely the nickel salt, is not particularly limited, but at least one of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate can be used, for example.

[0104] The cobalt salt, or cobalt salt solution, can be a solute, and can be any one of cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate.

[0105] The solute in the aluminum salt solution is the aluminum salt, and for example, at least one of aluminum sulfate, aluminum nitrate, aluminum chloride, and aluminum acetate can be used.

[0106] The above metal salts are used in conjunction with the above Ni. (1-y-z) CO y Al z The (OH)₂ is used in proportions corresponding to its composition. That is, the amount of each metal salt is specified such that the molar ratio of Ni, Co, and Al in the mixed solution containing the above metal salts corresponds to (1-yz):y:z in the composition formula (I) of LiMO. Furthermore, water is used as the solvent.

[0107] As a complexing agent, it is a substance that can form complexes with nickel ions, cobalt ions, and aluminum ions in aqueous solution. Examples include ammonium ion donors, hydrazine, ethylenediaminetetraacetic acid, hypozoxytriacetic acid, uracil diacetic acid, and glycine. Examples of ammonium donors include ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, or ammonium fluoride.

[0108] In the manufacturing process of metal complex hydroxides, a complexing agent may or may not be used. When a complexing agent is used, the amount of the complexing agent contained in the mixture comprising the nickel salt solution, cobalt salt solution, aluminum salt solution and the complexing agent is, for example, a molar ratio relative to the total number of moles of the metal salts (nickel salt, cobalt salt and aluminum salt) greater than 0 and less than 2.0.

[0109] In the coprecipitation method, to adjust the pH of the mixture containing nickel salt solution, cobalt salt solution, aluminum salt solution, and complexing agent, an alkali metal hydroxide is added to the mixture before the pH changes from alkaline to neutral. Examples of alkali metal hydroxides include sodium hydroxide or potassium hydroxide.

[0110] It should be noted that the pH value in this specification is defined as the value measured at a temperature of 40°C for the mixture. The pH of the mixture is measured when the temperature of the mixture sampled from the reaction tank reaches 40°C. If the sampled mixture is below 40°C, the mixture is heated to 40°C and the pH is measured. If the sampled mixture is above 40°C, the mixture is cooled to 40°C and the pH is measured.

[0111] If, in addition to the aforementioned nickel salt solution, cobalt salt solution, and aluminum salt solution, a complexing agent is continuously supplied to the reaction vessel, and an appropriate amount of alkali metal hydroxide is added to control the pH within a specific range, then Ni, Co, and Al react to produce Ni. (1-y-z) CO y Al z (OH)2.

[0112] During the reaction, the temperature of the reaction tank is controlled within a range of, for example, 20-80°C, preferably 30-70°C.

[0113] In addition, during the reaction, the pH value in the reaction tank is controlled within a range of, for example, 9-13.

[0114] The reaction tanks used in continuous coprecipitation methods can be of the type that allow overflow in order to separate the reaction precipitates formed.

[0115] In the case of manufacturing metal complex hydroxides by intermittent coprecipitation, the reaction tank can be categorized into a reaction tank without an overflow pipe and a concentration tank connected to an overflow pipe, which has a mechanism for concentrating the overflowing reaction precipitate in the concentration tank and circulating it back into the reaction tank.

[0116] Various gases, such as inert gases like nitrogen, argon, or carbon dioxide, oxidizing gases like air or oxygen, or mixtures thereof, can be supplied to the reaction vessel.

[0117] By appropriately controlling the concentration of the metal salt supplied to the reaction tank, the reaction temperature, and the reaction pH, the final CAM's D can be obtained. 50 The value of the BET specific surface area is controlled within the range of this embodiment.

[0118] After the above reaction, the neutralized reaction precipitate is separated. For separation, for example, a method is used to dewater the slurry containing the reaction precipitate (i.e., the coprecipitate slurry) by centrifugation or filtration.

[0119] The separated reaction precipitate was washed, dehydrated, dried and sieved to obtain a metal complex hydroxide containing Ni, Co and Al.

[0120] The washing of the reaction precipitate is preferably performed using water or an alkaline washing solution. In this embodiment, washing with an alkaline washing solution is preferred, and washing with an aqueous sodium hydroxide solution is more preferred.

[0121] When the MCC is a metal composite oxide, the metal composite oxide is manufactured by heating the metal composite hydroxide. Specifically, the metal composite hydroxide is heated at 400-700°C. Multiple heating steps may be performed if necessary. The heating temperature in this specification refers to the set temperature of the heating device. In cases with multiple heating steps, it refers to the temperature at which heating is performed at the highest holding temperature in each heating step.

[0122] The heating temperature is preferably 400-700℃, more preferably 450-680℃. At a heating temperature of 400-700℃, the metal composite hydroxide is fully oxidized, resulting in a metal composite oxide with a suitable BET specific surface area. If the heating temperature is below 400℃, the metal composite hydroxide may not be fully oxidized. If the heating temperature exceeds 700℃, the metal composite hydroxide may be over-oxidized, resulting in an excessively small BET specific surface area of ​​the metal composite oxide. By appropriately adjusting the above heating temperature, the P0.05 of LiMO can be... S and P B The control is within the range of this embodiment. If the above heating temperature is increased, P of LiMO will exist. S and P B The tendency to grow larger.

[0123] The holding time at the above heating temperature can be 0.1-20 hours, preferably 0.5-10 hours. The heating rate up to the above heating temperature is, for example, 50-400°C / hour. Furthermore, as the heating atmosphere, air, oxygen, nitrogen, argon, or a mixture thereof can be used.

[0124] The heating device can also contain a moderate oxygen atmosphere. This oxygen atmosphere can be a mixture of inert and oxidizing gases, or it can be a state where an oxidant is present in an inert gas atmosphere. By providing a moderate oxygen atmosphere within the heating device, the transition metals contained in the metal composite hydroxide are moderately oxidized, making it easier to control the morphology of the metal composite oxide.

[0125] In an oxygen-containing atmosphere, the oxygen or oxidant only needs to be sufficient to oxidize the transition metal.

[0126] In the case of an oxygen-containing atmosphere that is a mixture of inert and oxidizing gases, the atmosphere inside the heating device can be controlled by methods such as circulating oxidizing gases within the heating device.

[0127] As oxidants, peroxides such as hydrogen peroxide, peroxide salts such as permanganate, perchlorate, hypochlorite, nitric acid, halogens, or ozone can be used.

[0128] The above processes are used to manufacture MCCs.

[0129] (2) Mixing of MCC and lithium compounds

[0130] This process involves mixing a lithium compound with MCC to obtain a mixture.

[0131] After drying the MCC, it is mixed with a lithium compound. Grading can also be performed appropriately after drying the MCC.

[0132] The lithium compound used in this embodiment can be at least one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium oxide, lithium chloride, and lithium fluoride. Preferably, it is one of lithium hydroxide and lithium carbonate, or a mixture thereof. Furthermore, when the lithium hydroxide contains lithium carbonate, the lithium carbonate content in the lithium hydroxide is preferably 5% by mass or less.

[0133] The lithium compound and MCC are mixed to obtain a mixture, taking into account the composition ratio of the final target product. Specifically, the lithium compound and MCC are mixed in a ratio corresponding to the composition ratio of the above-described compositional formula (I). The amount (molar ratio) of lithium atoms relative to the total amount of metal atoms contained in the MCC is preferably 1.00 or more, more preferably 1.02 or more, and even more preferably 1.05 or more. The mixture of lithium compound and MCC is calcined as described below to obtain a calcined product.

[0134] (3) Temporary firing of the mixture

[0135] The mixture of MCC and lithium compound is temporarily fired. In this embodiment, the temporary firing is carried out at a temperature lower than the firing temperature in the firing process described later (the firing temperature of the firing stage performed at the lowest temperature when the firing process has multiple firing stages). Examples of firing temperatures for temporary firing include those in the range of 400°C or higher and below 700°C. Temporary firing can also be performed multiple times. Furthermore, the holding time during temporary firing is preferably 1-10 hours.

[0136] There are no particular limitations on the firing apparatus used for temporary firing; for example, either a continuous firing furnace or a mobile firing furnace can be used. Examples of continuous firing furnaces include tunnel kilns or roller hearth furnaces. As a mobile firing furnace, a rotary kiln can also be used. When using a mobile firing furnace, the apparatus described later can also be used. Figure 1 The firing apparatus shown.

[0137] (4) Firing of the mixture

[0138] This process involves firing the lithium compound obtained in the above temporary firing process with the reactants of MCC to obtain a fired product (hereinafter, sometimes referred to as the firing process). Figure 1 This is a schematic diagram illustrating an example of a sintering apparatus used in a LiMO manufacturing method according to one embodiment of this invention.

[0139] The reactants are fired using a flow-through firing furnace, or firing apparatus 400. In the flow-through firing furnace, the reactants (in this embodiment, the reactants of MCC and lithium compounds) are not placed in a sagger or the like; the reactants are fed into the firing furnace directly. Therefore, the firing speed can be controlled without being affected by the material of the sagger or the like.

[0140] A rotary kiln can be used as a mobile firing furnace. In the following description, the firing apparatus 400 is set to use a rotary kiln, and the firing apparatus 400 will be referred to as "rotary kiln 400" for description.

[0141] exist Figure 1 In this design, the rotary kiln 400 is a device for heating the workpiece X1 inside the drum 43. That is, the drum 43 is a firing furnace, and the workpiece X1 is fired inside the drum 43. At one end of the drum 43, a supply port 41 for the workpiece X1 is connected via a pipe 49. At the other end of the drum 43, a discharge port 42 for the workpiece X1 is connected.

[0142] The roller 43 is a cylindrical shape with an axis A, and can rotate around its axis. The roller 43 is inclined with the supply port 41 as the upper side and the discharge port 42 as the lower side. The inner wall of the roller 43 is preferably an alloy containing Ni, Fe and Cr.

[0143] The volume of drum 43 is, for example, 1-100m³. 3 Preferably 2-99m 3 More preferably 3-98m 3 .

[0144] A heating mechanism 44 is provided on the outer circumferential surface of the roller 43. Multiple heating mechanisms 44 may also be provided.

[0145] A piping 45 and a dust collector 46 are disposed between the supply port 41 and the roller 43. One side of the piping 45 is connected to the roller 43, and the other side is connected to the inlet of the dust collector 46. The dust collector 46 has an exhaust port 50 and an outlet port 47.

[0146] The material to be calcined X1, fed from the supply port 41, is supplied to the drum 43 via a feeding mechanism such as a screw feeder within the piping 49. Due to the tilting and rotation of the drum 43, the material to be calcined X1 is stirred while moving towards the discharge port 42. The material to be calcined X1 is calcined in a region equipped with a heating mechanism 44 (hereinafter sometimes referred to as a heating zone). After passing through the heating zone, the material to be calcined X1 is discharged from the discharge port 42 as calcined material.

[0147] To control the firing atmosphere in drum 43, gas G is introduced from gas inlet 48 located near outlet 42 toward dust collector 46. Gas G can be selected as atmosphere, oxygen, nitrogen, argon, or a mixture thereof, depending on the desired composition. By introducing gas G, small-sized particles P in the fired material X1 within drum 43 are agitated and dispersed. The dispersed particles P are guided into piping 45 by the flow of the introduced gas G and the airflow generated by dust collector 46. The particles P in piping 45 are recovered in dust collector 46. Dust collector 46 exhausts from outlet 50 and discharges the fired material P from outlet 47 to supply port 41. As a result, the fired material P is reintroduced into drum 43.

[0148] That is, the smaller particle size P in the fired material X1 sometimes passes through the heating zone multiple times. The fired material obtained by passing through the heating zone multiple times, through multiple firing processes, has greater particle strength compared to the fired material with larger particle size that does not disperse, for example, obtained by passing through the heating zone only once. As a result, it is possible to simultaneously obtain particles with a particle size D... 50 The following and P S and σ S The first particle within the scope of this embodiment, and particles with a diameter exceeding D 50 And P B and σ B This refers to the second particle within the scope of this embodiment.

[0149] In this embodiment, an example is described where the calcined material P collected by the dust collector 46 is fed into the drum 43 from the supply port 41, but the present invention is not limited thereto. The present invention can be applied to any configuration where the calcined material P collected by the dust collector 46 flows concurrently with the processed material X1 in the area between the supply port 41 and the piping 49. For example, the discharge port 47 of the dust collector 46 can also be connected to the piping 49.

[0150] The average linear velocity of the introduced gas G is preferably 0.001-1 m / sec, more preferably 0.005-0.9 m / sec. If the average linear velocity of the introduced gas G is 0.001 m / sec or higher, the calcined material X1 contains calcined material P with a small particle size, specifically, a particle size of D. 50 The following particles are easily agitated and dispersed within drum 43. If the average linear velocity of the introduced gas G is below 1 m / sec, the calcined material X1 will not disperse as a whole; only the smaller particles P will easily disperse. By appropriately adjusting the average linear velocity of the introduced gas G, the P particles of LiMO can be dispersed. S and σ S Within the range specified in this embodiment. If the average linear velocity of the introduced gas G is increased, then P of LiMO will exist.S Increase, σ S The tendency to grow larger.

[0151] The average linear velocity of gas G is the set value when gas G is introduced into roller 43, which can be calculated by the following formula (III).

[0152] Linear velocity [m / sec] =

[0153] (Gas flow rate [Nm) 3 / h]÷3600) / {π×(inner diameter of the drum) 2 [m 2 [×(100 - Filling rate of the fired material in the drum [vol%])÷100]

[0154] =Gas flow rate [m 3 / sec] / Gas phase cross-sectional area [m 2 (III)

[0155] The firing atmosphere within the drum 43 can be atmosphere, oxygen, nitrogen, argon, or a mixture thereof, depending on the desired composition. In this embodiment, the firing atmosphere is preferably an oxygen-containing atmosphere. When the firing atmosphere is an oxygen-containing atmosphere, the oxygen concentration in the firing atmosphere is preferably 21-100% by volume, more preferably 25-100% by volume.

[0156] As a dust collector, a cyclone dust collector or a gravity dust collector can be used. For the operation of a cyclone dust collector, the average linear velocity of the gas at the inlet is 10-25 m / sec. The average linear velocity of the gas can be adjusted by appropriately selecting the inlet diameter of the cyclone dust collector. For the operation of a gravity dust collector, the average linear velocity of the gas in the settling chamber can be listed as 1-2 m / sec. If these operating conditions are specified as described above, the burned material X1 will not scatter as a whole; only the smaller particles P will scatter and be easily collected into the dust collector 46.

[0157] The firing process can also have multiple firing stages with different firing temperatures. For example, the first firing stage can be carried out independently, and the second firing stage can be carried out at a higher temperature than the first firing stage. Furthermore, there can be firing stages with different firing temperatures and firing times.

[0158] In this embodiment, the firing temperature is 700°C or higher, preferably 700-1100°C, and more preferably 720-1050°C. If the firing temperature is 700°C or higher, LiMO with a robust crystal structure can be obtained. Furthermore, if the firing temperature is 1100°C or lower, the volatilization of lithium on the surface of secondary particles contained in LiMO can be reduced. By appropriately adjusting the firing temperature, the P of LiMO can be reduced.B σ B The control is within the scope of this embodiment. If the firing temperature is increased, P of LiMO will be present. B Increase, σ B The tendency to shrink.

[0159] The firing temperature in this specification refers to the temperature of the atmosphere inside the firing furnace, and is the highest temperature at which the firing temperature is held during the firing process (hereinafter, sometimes referred to as the maximum holding temperature). In the case of a firing process with multiple heating steps, the firing temperature refers to the temperature at which heating occurs in each heating step at the maximum holding temperature. The above-mentioned upper and lower limits of the firing temperature can be combined arbitrarily.

[0160] The preferred holding time during calcination is 3-50 hours. If the holding time is more than 3 hours, crystallization is fully developed, improving battery performance. If the holding time is less than 50 hours, lithium volatilization is less likely, further improving battery performance. By appropriately adjusting the holding time during calcination, the P-type of LiMO can be... B and σ B The control is within the scope of this embodiment. If the holding time during firing is extended, P of LiMO will exist. B Increase, σ B The tendency to shrink.

[0161] In this specification, the holding time during firing is defined as the time from when the object to be fired X is supplied from the supply port 41 to when it reaches the end of the area where the heating mechanism 44 is provided.

[0162] The rotation speed of the drum 43 in the firing process is preferably 0.025-5.0 rpm, more preferably 0.45-4.0 rpm, and even more preferably 0.7-3.0 rpm. If the rotation speed of the drum 43 is 0.025-5.0 rpm, only the small-sized particles P of the fired material are easily scattered. By appropriately adjusting the rotation speed of the drum 43 in the firing process, the P of LiMO can be... S and σ S Within the scope of this embodiment. If the rotation speed of the drum 43 in the firing process is increased, then P of LiMO exists. S Increase, σ S The tendency to grow larger.

[0163] As described above, by appropriately adjusting the heating temperature, the average linear velocity of the introduced gas, the firing temperature, the holding time during firing, and the rotation speed of the drum 43 in the firing process, the P of LiMO can be... S σ S 、P B and σ B Control is the scope of this implementation method.

[0164] Mixtures of MCC and lithium compounds can also be calcined in the presence of an inert flux. The inert flux may remain in the calcined product or may be removed after calcination by washing with a washing solution, as described later. For example, substances described in International Publication No. 2019 / 177032 can be used as inert fluxes.

[0165] LiMO is obtained by calcining the reactants of MCC and lithium compounds as described above.

[0166] (5) Other processes

[0167] After the firing process, LiMO can be washed to remove residual unreacted lithium compounds and inert flux. For washing, pure water or an alkaline washing solution can be used. Examples of alkaline washing solutions include aqueous solutions of one or more anhydrous lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, and ammonium carbonate, or their hydrates. Ammonia water can also be used as an alkaline washing solution.

[0168] The temperature of the washing solution is preferably below 15°C, more preferably below 10°C, and even more preferably below 8°C. By controlling the temperature of the washing solution within the above range to prevent freezing, excessive dissolution of lithium ions from the crystal structure of LiMO into the washing solution during washing can be suppressed.

[0169] One method for bringing the washing solution into contact with LiMO is to add LiMO to each washing solution and stir. Alternatively, the washing solution can be used as a spray water to apply the LiMO. Furthermore, another method involves adding LiMO to the washing solution and stirring, separating the LiMO from each washing solution, and then using the washing solution as a spray water to apply the separated LiMO.

[0170] During washing, it is preferable to allow the washing solution to contact the LiMO for an appropriate time. "Appropriate time" in washing refers to the time required to remove unreacted lithium compounds and inert fluxes remaining on the surface of the LiMO and to disperse the individual LiMO particles. The washing time is preferably adjusted according to the aggregation state of the LiMO. A particularly preferred washing time is, for example, in the range of 5 minutes to 1 hour.

[0171] The ratio of LiMO to the mixture of washing liquid and LiMO (hereinafter, sometimes referred to as slurry) is preferably 10-60% by mass, more preferably 20-50% by mass, and even more preferably more than 30% by mass and less than 50% by mass. When the proportion of LiMO is 10-60% by mass, unreacted lithium compounds and inert fluxing agents can be removed.

[0172] After washing the LiMO, it is preferable to subject the LiMO to heat treatment. The temperature and method of heat treatment are not particularly limited, but from the viewpoint of preventing a decrease in charge capacity, 100°C or higher is preferred, more preferably 130°C or higher, and even more preferably 150°C or higher. Furthermore, although there are no particular limitations, from the viewpoint of preventing lithium volatilization and obtaining LiMO with the composition of this embodiment, 700°C or lower is preferred, more preferably 600°C or lower.

[0173] The amount of lithium volatilization can be controlled by the heat treatment temperature.

[0174] The upper and lower limits of the heat treatment temperature can be combined arbitrarily. For example, the heat treatment temperature is preferably 100-700℃, more preferably 130-600℃, and even more preferably 150-600℃.

[0175] The atmosphere used in heat treatment can include oxygen atmosphere, inert atmosphere, reduced pressure atmosphere, or vacuum atmosphere. By performing heat treatment followed by washing in the above atmospheres, the reaction between LiMO and moisture or carbon dioxide in the atmosphere during heat treatment can be suppressed, resulting in LiMO with fewer impurities.

[0176] The first manufacturing method of this embodiment has been described as above, but the present invention is not limited to this manufacturing method. Any method that can produce a product containing the first particle and the second particle, D... 50 2-20μm, P S Greater than P B σ S Greater than σ B If the manufacturing method is similar to that of LiMO, then any manufacturing method can be applied to this invention.

[0177] For example, as a second manufacturing method in this embodiment, there is a method for manufacturing LiMO by mixing first particles and second particles manufactured using different methods to control particle strength and particle size. In this case, a flow-type calcining furnace or a continuous calcining furnace such as a roller hearth furnace can be used as the calcining furnace.

[0178] For example, except for the multiple firings in the firing furnace without a dust collector in "(4) Firing of the Mixture" described in the first manufacturing method, the first particle is manufactured in the same manner as in the first manufacturing method. Meanwhile, in the aforementioned "(4) Firing of the Mixture", the second particle is manufactured by firing fewer times than the first particle in the aforementioned firing process, for example, by firing once in a firing furnace without a dust collector, except that the operation is the same as in the first manufacturing method. By mixing the obtained first and second particles, LiMO can be obtained.

[0179] <Positive electrode active materials for lithium secondary batteries>

[0180] The CAM of this embodiment contains LiMO manufactured by the method described above. In the CAM of this embodiment, the content of LiMO relative to the total mass (100% by mass) of the CAM is preferably 70-99% by mass, more preferably 80-98% by mass.

[0181] In this embodiment, the proportion of LiMO relative to the total mass of CAM can be determined by observing the CAM using a SEM (e.g., JSM-5510 manufactured by NJEOL Ltd.) irradiated with electron beams at an accelerating voltage of 20 kV. The magnification of the SEM image is adjusted to ensure that there are 200-400 CAM particles of the target in the SEM image. As an example, the magnification can also be 1000-30000 times.

[0182] <Lithium secondary batteries>

[0183] Next, the preferred configuration of a lithium secondary battery using LiMO as a CAM in this embodiment will be described.

[0184] Furthermore, a preferred positive electrode (hereinafter, sometimes referred to as positive electrode) for a lithium secondary battery when using LiMO as the CAM in this embodiment will be described.

[0185] Furthermore, a preferred lithium secondary battery for use as a positive electrode will be described.

[0186] An example of a preferred lithium secondary battery using LiMO as a CAM in this embodiment includes a positive electrode and a negative electrode, a separator sandwiched between the positive and negative electrodes, and an electrolyte disposed between the positive and negative electrodes.

[0187] An example of a lithium secondary battery includes a positive electrode and a negative electrode, a separator sandwiched between the positive and negative electrodes, and an electrolyte disposed between the positive and negative electrodes.

[0188] Figure 2 This is a schematic diagram illustrating an example of a lithium secondary battery. The cylindrical lithium secondary battery 10 of this embodiment is manufactured as follows.

[0189] First, such as Figure 2 As shown, an electrode assembly 4 is formed by stacking and winding a pair of strip-shaped diaphragms 1, a strip-shaped positive electrode 2 with a positive electrode lead 21 at one end, and a strip-shaped negative electrode 3 with a negative electrode lead 31 at one end in the order of diaphragm 1, positive electrode 2, diaphragm 1, and negative electrode 3.

[0190] Next, after accommodating the electrode assembly 4 and an insulator (not shown) in the battery can 5, the bottom of the can is sealed, allowing the electrolyte 6 to permeate the electrode assembly 4, with the electrolyte positioned between the positive electrode 2 and the negative electrode 3. Furthermore, by sealing the upper part of the battery can 5 with a top insulator 7 and a sealing body 8, a lithium secondary battery 10 can be manufactured.

[0191] As for the shape of the electrode assembly 4, for example, the cross-sectional shape when the electrode assembly 4 is cut perpendicularly to the winding axis can be a circle, an ellipse, a rectangle, or a columnar shape such as a rectangle obtained by rounding the corners.

[0192] Furthermore, the shape of the lithium secondary battery having such an electrode assembly 4 can adopt the shape specified in the International Electrotechnical Commission (IEC) battery standards, namely IEC 60086 or JIS C 8500. For example, cylindrical or square shapes can be listed.

[0193] Furthermore, lithium secondary batteries are not limited to the above-mentioned wound type structure, but can also be a stacked type structure obtained by repeatedly overlapping the positive electrode, separator, negative electrode, and separator. Examples of stacked lithium secondary batteries include so-called coin-type batteries, button-type batteries, or paper-type (or sheet-type) batteries.

[0194] The following sections will explain each component in turn.

[0195] (positive electrode)

[0196] The positive electrode can be manufactured by first preparing a positive electrode mixture containing CAM, conductive material and binder, and then loading the positive electrode mixture onto the positive electrode current collector.

[0197] (Conductive materials)

[0198] Carbon materials can be used as the conductive material for the positive electrode. Examples of carbon materials include graphite powder, carbon black (such as acetylene black), and fibrous carbon materials.

[0199] The proportion of conductive material in the positive electrode mixture is preferably 5-20 parts by weight relative to CAM100.

[0200] (Adhesive)

[0201] Thermoplastic resins can be used as the binder in the positive electrode. Examples of such thermoplastic resins include polyimide resins; fluorinated resins such as polyvinylidene fluoride (hereinafter, sometimes referred to as PVdF), and polytetrafluoroethylene; polyolefin resins such as polyethylene and polypropylene; and resins described in WO2019 / 098384A1 or US2020 / 0274158A1.

[0202] (Positive current collector)

[0203] As the positive current collector of the positive electrode, a strip-shaped component made of metal materials such as Al, Ni or stainless steel can be used.

[0204] As a method for loading a positive electrode agent onto a positive current collector, the following methods can be listed: paste the positive electrode agent using an organic solvent, apply the resulting paste of the positive electrode agent to at least one side of the positive current collector and dry it, perform an electrode pressing process and bond it.

[0205] In the case of pasteurizing the positive electrode mixture, N-methyl-2-pyrrolidone (hereinafter, sometimes referred to as NMP) can be listed as a usable organic solvent.

[0206] Methods for applying a paste of positive electrode agent to the positive electrode current collector include, for example, slot extrusion coating, screen coating, curtain coating, scraper coating, gravure coating, and electrostatic spraying.

[0207] The positive electrode can be manufactured using the methods listed above.

[0208] (negative electrode)

[0209] The negative electrode of a lithium secondary battery only needs to be able to dope and dedope lithium ions at a lower potential than the positive electrode. Examples include electrodes formed by a negative electrode mixture containing negative electrode active material supported on a negative electrode current collector and electrodes formed solely by negative electrode active material.

[0210] (Negative electrode active material)

[0211] Examples of negative electrode active materials include carbon materials, chalcogenides (oxides or sulfides, etc.), nitrides, metals or alloys, and materials that can be doped and dedoped with lithium ions at a lower potential than that of the positive electrode.

[0212] Carbon materials that can be used as negative electrode active materials include natural or artificial graphite, coke, carbon black, carbon fibers, and sintered organic polymer compounds.

[0213] As oxides that can be used as negative electrode active materials, examples include SiO2 and SiO (e.g., SiO2). x (where x is a positive real number) represents the oxide of silicon; SnO2 and SnO equation SnO x (where x is a positive real number) represents the tin oxide; Li4Ti5O 12 Metal composite oxides containing lithium and titanium, etc.

[0214] In addition, lithium metal, silicon metal, and tin metal are examples of metals that can be used as negative electrode active materials. Materials described in WO2019 / 098384A1 or US2020 / 0274158A1 can also be used as negative electrode active materials.

[0215] These metals or alloys, for example, after being processed into foil, are primarily used as electrodes on their own.

[0216] Among the aforementioned negative electrode active materials, carbon materials with graphite as the main component, such as natural graphite or artificial graphite, are preferred because the potential of the negative electrode remains essentially unchanged from an uncharged state to a fully charged state during charging (good potential flatness), the average discharge potential is low, and the capacity retention rate during repeated charge and discharge (good cycle characteristics). The shape of the carbon material can be, for example, any of the following: flakes like natural graphite, spheres like mesophase carbon microspheres, fibrous forms like graphitized carbon fibers, or aggregates of micropowder.

[0217] The aforementioned negative electrode compound may also contain an adhesive as needed. Examples of adhesives include thermoplastic resins, specifically PVdF, thermoplastic polyimide, carboxymethyl cellulose (hereinafter, sometimes referred to as CMC), styrene-butadiene rubber (hereinafter, sometimes referred to as SBR), polyethylene, and polypropylene.

[0218] (Negative current collector)

[0219] As a negative electrode current collector, examples include strip-shaped components made of metallic materials such as Cu, Ni, or stainless steel.

[0220] As a method for loading the negative electrode agent onto such a negative electrode current collector, similar to the case of the positive electrode, methods such as press molding, paste formation using solvents and coating onto the negative electrode current collector, or drying followed by pressing and bonding can be listed.

[0221] (Septum)

[0222] As a separator in a lithium-ion secondary battery, materials such as porous membranes, nonwoven fabrics, or woven fabrics formed from polyolefin resins such as polyethylene and polypropylene, fluoropolymers, or nitrogen-containing aromatic polymers can be used. Furthermore, two or more of these materials can be used to form the separator, or these materials can be laminated to form the separator. Additionally, separators described in JP-A-2000-030686 or US20090111025A1 can also be used.

[0223] (electrolyte)

[0224] The electrolyte in a lithium secondary battery contains electrolytes and organic solvents.

[0225] Lithium salts such as LiClO4, LiPF6, and LiBF4 can be used as electrolytes in electrolyte solutions, or mixtures of two or more of these can be used.

[0226] In addition, as organic solvents included in the above-mentioned electrolyte, carbonates such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate can be used.

[0227] As organic solvents, it is preferable to use a mixture of two or more of them. Among them, a mixed solvent containing carbonates is preferred, and a mixed solvent of cyclic carbonates and non-cyclic carbonates and a mixed solvent of cyclic carbonates and ethers is even more preferred.

[0228] Furthermore, to improve the safety of the resulting lithium secondary battery, it is preferable to use an electrolyte containing a fluorine-containing lithium salt such as LiPF6 and an organic solvent with fluorine substituents. The electrolyte and organic solvent described in WO2019 / 098384A1 or US2020 / 0274158A1 may also be used as the electrolyte and organic solvent contained in the electrolyte.

[0229] All-solid-state lithium secondary batteries

[0230] Next, the structure of the all-solid-state lithium secondary battery will be described, and an all-solid-state lithium secondary battery having LiMO as the positive electrode of the CAM in an all-solid-state lithium secondary battery according to one embodiment of the present invention will also be described.

[0231] Figure 3 This is a schematic diagram illustrating an example of an all-solid-state lithium secondary battery according to this embodiment. Figure 3 The all-solid-state lithium secondary battery 1000 shown has a laminate 100 comprising a positive electrode 110, a negative electrode 120, and a solid electrolyte layer 130, and an outer casing 200 for housing the laminate 100. Furthermore, the all-solid-state lithium secondary battery 1000 can also be a bipolar structure with a current collector and a negative electrode active material disposed on both sides of the current collector. As a specific example of a bipolar structure, the structure described in JP-A-2004-95400 can be cited. The materials constituting each component are described below.

[0232] The laminate 100 may also have an external terminal 113 connected to the positive current collector 112 and an external terminal 123 connected to the negative 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.

[0233] The all-solid-state lithium secondary battery 1000 further includes an insulator (not shown) that insulates the laminate 100 from the outer packaging 200, and a seal (not shown) that seals the opening 200a of the outer packaging 200.

[0234] The outer packaging 200 can be a container formed from a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel. Alternatively, the outer packaging 200 can also be a container formed by processing a laminated film with at least one side treated to be corrosion-resistant into a bag shape.

[0235] The shapes of the all-solid-state lithium secondary battery 1000 can include, for example, coin type, button type, paper type (or sheet type), cylindrical type, square type, or laminated type (bag type).

[0236] The all-solid-state lithium secondary battery 1000 is illustrated as an example having a single stack 100, but this embodiment is not limited to this. The all-solid-state lithium secondary battery 1000 may also be configured such that the stack 100 is used as a unit cell and multiple unit cells (stacks 100) are sealed inside the outer packaging 200.

[0237] The following sections will explain each component in turn.

[0238] (positive electrode)

[0239] The positive electrode 110 of this embodiment has a positive electrode active material layer 111 and a positive electrode current collector 112.

[0240] The positive electrode active material layer 111 comprises the LiMO and solid electrolyte described above as one embodiment of the present invention. Furthermore, the positive electrode active material layer 111 may also comprise a conductive material and a binder.

[0241] (Solid electrolyte)

[0242] The solid electrolyte included in the positive electrode active material layer 111 of this embodiment can be a solid electrolyte that is known to be used in all-solid-state lithium secondary batteries and has lithium-ion conductivity. Examples of such solid electrolytes include inorganic electrolytes and organic electrolytes. Examples of inorganic electrolytes include oxide-based solid electrolytes, sulfide-based solid electrolytes, and hydride-based solid electrolytes. Examples of organic electrolytes include polymer-based solid electrolytes. Examples of compounds described in WO2020 / 208872A1, US2016 / 0233510A1, US2012 / 0251871A1, and US2018 / 0159169A1 can be cited as examples.

[0243] (Oxide-based solid electrolyte)

[0244] Examples of oxide-based solid electrolytes include perovskite oxides, NASICON oxides, LISICON oxides, and garnet oxides. Specific examples of each oxide can be found in compounds described in WO2020 / 208872A1, US2016 / 0233510A1, and US2020 / 0259213A1, such as the following compounds.

[0245] As a garnet-type oxide, Li7La3Zr2O can be listed as an example. 12 Li-La-Zr oxides, such as LLZ (also known as LLZ).

[0246] Oxide-based solid electrolytes can be either crystalline or amorphous materials.

[0247] (Sulfide-based solid electrolyte)

[0248] As sulfide-based solid electrolytes, examples include Li₂S-P₂S₅ compounds, Li₂S-SiS₂ compounds, Li₂S-GeS₂ compounds, Li₂S-B₂S₃ compounds, LiI-Si₂S-P₂S₅ compounds, LiI-Li₂S-P₂O₅ compounds, LiI-Li₃PO₄-P₂S₅ compounds, and Li 10 GeP2S 12 wait.

[0249] It should be noted that in this specification, the term "system compound" referring to sulfide-based solid electrolytes is used as a general term for solid electrolytes that mainly contain raw materials such as "Li2S" and "P2S5" as described before "system compound". For example, for Li2S-P2S5 system compounds, it includes solid electrolytes that mainly contain Li2S and P2S5, and further contain other raw materials. The proportion of Li2S contained in Li2S-P2S5 system compounds is, for example, 50 to 90% by mass relative to the total Li2S-P2S5 system compound. The proportion of P2S5 contained in Li2S-P2S5 system compounds is, for example, 10 to 50% by mass relative to the total Li2S-P2S5 system compound. In addition, the proportion of other raw materials contained in Li2S-P2S5 system compounds is, for example, 0 to 30% by mass relative to the total Li2S-P2S5 system compound. Furthermore, for Li2S-P2S5 system compounds, it also includes solid electrolytes with different mixing ratios of Li2S and P2S5.

[0250] As compounds in the Li2S-P2S5 series, examples include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr.

[0251] Examples of Li2S-SiS2 compounds include Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, and Li2S-SiS2-P2S5-LiCl.

[0252] Examples of Li2S-GeS2 compounds include Li2S-GeS2 and Li2S-GeS2-P2S5.

[0253] Sulfide-based solid electrolytes can be either crystalline or amorphous materials.

[0254] Two or more solid electrolytes may be used together without impairing the effectiveness of the invention.

[0255] (Conductive materials and adhesives)

[0256] As the conductive material in the positive electrode active material layer 111, the materials described in the above-described (conductive material) section can be used. Furthermore, the proportion of the conductive material in the positive electrode mixture can also be the proportion described in the above-described (conductive material) section. Additionally, as the binder in the positive electrode, the materials described in the above-described (binder) section can be used.

[0257] (Positive current collector)

[0258] The positive current collector 112 of the positive electrode 110 can be made of the material described above (positive current collector).

[0259] One method for loading the positive electrode active material layer 111 onto the positive electrode current collector 112 is to press-form the positive electrode active material layer 111 onto the positive electrode current collector 112. For press-forming, cold pressing or hot pressing can be used.

[0260] Alternatively, a positive electrode paste can be prepared by using an organic solvent to paste a mixture of CAM, solid electrolyte, conductive material and adhesive. The obtained positive electrode paste is then coated on at least one surface of the positive electrode current collector 112 and dried, pressed and bonded, thereby enabling the positive electrode active material layer 111 to be supported on the positive electrode current collector 112.

[0261] Alternatively, a positive electrode paste can be prepared by using an organic solvent to paste a mixture of CAM, solid electrolyte and conductive material. The obtained positive electrode paste is then coated on at least one surface of the positive electrode current collector 112 and dried and sintered, thereby enabling the positive electrode active material layer 111 to be supported on the positive electrode current collector 112.

[0262] The organic solvent that can be used in the positive electrode mixture is the same organic solvent that can be used in the case of pasteurizing the positive electrode mixture as described above in (positive electrode current collector).

[0263] As a method for coating the positive electrode mixture onto the positive electrode current collector 112, the method described above (positive electrode current collector) can be cited as an example.

[0264] The positive electrode 110 can be manufactured using the methods listed above. The specific combinations of materials used in the positive electrode 110 can be listed in Japanese Patent Application No. 2021-015685.

[0265] (negative electrode)

[0266] 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. The negative electrode active material, negative electrode current collector, solid electrolyte, conductive material, and binder may be the substances described above.

[0267] As a method for loading the negative electrode active material layer 121 onto the negative electrode current collector 122, similar to the case of the positive electrode 110, the following methods can be listed: using a pressure molding method; applying a paste-like negative electrode mixture containing the negative electrode active material onto the negative electrode current collector 122, drying it, pressing and bonding it; and applying a paste-like negative electrode mixture containing the negative electrode active material onto the negative electrode current collector 122, drying it, and then sintering it.

[0268] (Solid electrolyte layer)

[0269] The solid electrolyte layer 130 has the aforementioned solid electrolyte.

[0270] The solid electrolyte layer 130 can be formed by depositing an inorganic solid electrolyte on the surface of the positive electrode active material layer 111 of the positive electrode 110 by sputtering.

[0271] Furthermore, the solid electrolyte layer 130 can be formed by coating the surface of the positive electrode active material layer 111 of the positive electrode 110 with a paste-like mixture containing solid electrolyte and then drying it. Alternatively, after drying, it can be pressed and further pressed by cold isostatic pressing (CIP) to form the solid electrolyte layer 130.

[0272] The laminate 100 can be manufactured by laminating the negative electrode 120 in such a way that the surfaces of the negative electrode active material layer 121 and the solid electrolyte layer 130 are in contact with each other using a known method on the solid electrolyte layer 130 disposed on the positive electrode 110 as described above.

[0273] In the lithium secondary battery with the above configuration, since the CAM uses LiMO manufactured through the above embodiment, the cycle retention rate of the lithium secondary battery using the CAM can be improved.

[0274] Furthermore, the positive electrode with the above-described configuration can improve the cycle life of the lithium secondary battery due to the presence of the aforementioned CAM.

[0275] Furthermore, lithium secondary batteries with the above-described configuration, having the aforementioned positive electrode, become secondary batteries with high cycle retention rates.

[0276] In another aspect, the present invention includes the following solutions.

[0277]

[14] A LiMO, which is a particulate LiMO containing a cumulative volumetric particle size D of 50% of the aforementioned LiMO. 50 The following first particle, and particles with a diameter exceeding D above. 50 The second particle, the aforementioned D 50 The average particle intensity P of the first particle is 2-20 μm. S Compared with the average particle intensity P of the second particle mentioned above B The difference is P S -P B The standard deviation σ of the particle intensity of the first particle is 17-70 MPa. S The standard deviation σ of the particle intensity of the second particle mentioned above is greater than that of the second particle. B .

[0278]

[15] According to the LiMO described in

[14] , wherein the above σ S With the above σ B The difference is σ S -σ B It is 7-70 MPa.

[0279]

[16] According to the LiMO described in

[14] or

[15] , wherein the above-mentioned P S It is 53-105 MPa.

[0280]

[17] The LiMO according to any one of

[14] to

[16] , wherein the above-mentioned P B It is 30-55 MPa.

[0281]

[18] The LiMO according to any one of

[14] to

[17] , wherein the above σ S It is 25-85 MPa.

[0282]

[19] The LiMO according to any one of

[14] to

[18] , wherein the above σ BIt is 13-28 MPa.

[0283]

[20] The LiMO according to any one of

[14] to

[19] , wherein the BET specific surface area is 1.0-1.5 m². 2 / g.

[0284]

[21] The LiMO according to any one of

[14] to

[20] is represented by compositional formula (I).

[0285] Li[Li x (Ni (1-y-z) CO y X z ) 1-x O2 (I)

[0286] (In formula (I), X represents one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, Si, S and P, and satisfying -0.1≤x≤0.2, 0≤y≤0.4 and 0<z≤0.5.)

[0287]

[22] According to the LiMO described in

[21] , the above composition (I) satisfies 0<y+z≤0.3.

[0288]

[23] A CAM containing any one of

[14] to

[22] LiMO.

[0289]

[24] A positive electrode for a lithium secondary battery, comprising the CAM described in

[23] .

[0290]

[25] A lithium secondary battery having the positive electrode for a lithium secondary battery as described in

[24] .

[0291] Example

[0292] The present invention will be described in detail below with reference to embodiments, but the present invention is not limited to the following description.

[0293] Compositional Analysis

[0294] The compositional analysis of the LiMO produced by the method described later was performed by dissolving the obtained LiMO in hydrochloric acid and then using an inductively coupled plasma atomic emission spectrometer (SII Nano Technology Co., Ltd., SPS3000).

[0295] <D 50 >

[0296] As the measurement object, the powder of LiMO was used. As the laser diffraction scattering particle size distribution measuring device, Microtrac MT3300EXII manufactured by MicrotracBEL Co., Ltd. was used, and D was measured by the method described in the above <Measurement method of cumulative particle size distribution>. 50 .

[0297] <Average particle strength and standard deviation of particle strength>

[0298] As the micro compression testing machine, MCT-510 manufactured by Shimadzu Corporation was used, and P was calculated respectively by the method described in the above <Measurement method of average particle strength and standard deviation of particle strength>. S 、P B 、σ S 及σ B . P was calculated from the obtained values. s -P B 和σ s -σ B .

[0299] <BET specific surface area measurement>

[0300] After drying 1 g of the powder of LiMO in a nitrogen atmosphere at 105 °C for 30 minutes, it was measured using a BET specific surface area meter (Macsorb (registered trademark) manufactured by Mountech Co., Ltd.) (unit: m 2 / g).

[0301] <Method for identifying crystal structure>

[0302] Powder X-ray diffraction measurement was carried out using an X-ray diffraction apparatus (UltimaIV manufactured by Rigaku Corporation). By filling the powder of LiMO into a dedicated substrate and using a Cu-Kα ray source, the measurement was carried out under the conditions of diffraction angle 2θ = 10° to 90°, sampling amplitude 0.02°, and scanning speed 4° / min to obtain a powder X-ray diffraction pattern.

[0303] The crystal structure was identified from the above powder X-ray diffraction pattern using the comprehensive powder X-ray analysis software JADE.

[0304] <Fabrication of positive electrode for lithium secondary battery>

[0305] LiMO obtained by the manufacturing method described later, a conductive material (acetylene black), and a binder (PVdF) were added and kneaded in a composition such that LiMO:conductive material:binder = 92:5:3 (mass ratio) to prepare a paste-like positive electrode mixture. When preparing the positive electrode mixture, NMP was used as the organic solvent.

[0306] The obtained positive electrode mixture was coated onto a 40 μm thick Al foil as a current collector and vacuum dried at 150 °C for 8 hours to obtain a positive electrode for lithium secondary batteries. The electrode area of ​​this positive electrode for lithium secondary batteries was set to 1.65 cm². 2 .

[0307] Making a Lithium Secondary Battery (Coin-Shaped Half-Battery)

[0308] Perform the following operations inside a glove box under an argon atmosphere.

[0309] The positive electrode for a lithium-ion secondary battery, prepared in the "Preparation of Positive Electrode for Lithium-ion Secondary Batteries" section, is placed with the aluminum foil side down on the lower cover of a component for a coin-type battery R2032 (manufactured by Hosen Co., Ltd.). A laminated membrane separator (a 16 μm thick laminate of a porous polyethylene membrane with a heat-resistant porous layer) is then placed on top. 300 μl of electrolyte is injected. The electrolyte is prepared by dissolving LiPF6 in a 16:10:74 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate at a concentration of 1.3 mol / L, and dissolving 1.0% ethylene carbonate.

[0310] Next, using metallic lithium as the negative electrode, the negative electrode was placed on top of the laminated membrane separator, and the top cover was placed on top of it with a gasket. The lithium secondary battery (coin-type half-cell R2032, sometimes referred to as "coin-type half-cell") was then fabricated by using a sew-sealing machine.

[0311] <Cyclic Test>

[0312] For the coin-shaped half-cell manufactured by the above method, the cycle maintenance rate is calculated by the method described in the above <Cycling Test>.

[0313] (Example 1)

[0314] After adding water to the reaction tank equipped with a stirrer and an overflow pipe, add an aqueous solution of sodium hydroxide and maintain the liquid temperature at 50°C.

[0315] A mixed raw material solution was prepared by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution and aluminum sulfate aqueous solution in a molar ratio of Ni to Co to Al of 0.88:0.09:0.03.

[0316] Next, the mixed raw material solution and ammonium sulfate aqueous solution were continuously added as complexing agents in the reaction tank under stirring. Sodium hydroxide aqueous solution was added dropwise in a timely manner to make the pH of the solution in the reaction tank 11.6 (measurement temperature: 40℃) to obtain reaction precipitate 1.

[0317] After washing the reaction precipitate 1, it was dehydrated, dried and sieved to obtain a metal composite hydroxide 1 containing Ni, Co and Al.

[0318] Metal composite hydroxide 1 was heated at 650°C for 5 hours in an atmospheric atmosphere and then cooled to room temperature to obtain metal composite oxide 1.

[0319] Lithium hydroxide is weighed such that the amount of Li contained in metal composite oxide 1 is 1.10 relative to the total stoichiometry (molar ratio) of Ni, Co, and Al. Metal composite oxide 1 is mixed with lithium hydroxide to obtain mixture 1.

[0320] The mixture 1 was placed in a rotary kiln and heated at 690°C for 2 hours in an oxygen atmosphere to obtain the reaction product 1 of metal composite oxide 1 and lithium hydroxide.

[0321] Next, the obtained reactant 1 was fed into a rotary kiln connected to a cyclone dust collector and piping. At this time, gas with an oxygen concentration of 100% by volume was introduced from the outlet side of the rotary kiln towards the inlet side at an average linear velocity of 0.062 m / sec. The operating conditions of the cyclone dust collector were as follows: the average linear velocity of the gas at the inlet of the cyclone dust collector was set to 15 m / sec. The rotation speed of the rotary kiln drum was 0.71 rpm. The temperature of the atmosphere inside the calcining furnace was set to 770°C and maintained for 2 hours to calcine reactant 1, obtaining calcined product 1.

[0322] The slurry, prepared by mixing the above-mentioned calcined material 1 with pure water at a liquid temperature of 5°C in a mass ratio of 30% by mass of the calcined material to the total slurry, was stirred for 20 minutes, dehydrated, heat-treated at 250°C, and the residual water was dried after dehydration to obtain LiMO(1).

[0323] The crystal structure of LiMO(1) is a layered rock salt type crystal structure. The compositional analysis of LiMO(1) was performed, and the results are as follows: in the composition formula (I), x = 0.04, y = 0.093, z = 0.024, and element X is Al.

[0324] (Example 2)

[0325] Except that the mass ratio of the calcined material 1 to the total amount of slurry in the washing process is set to 40% by mass, LiMO (2) is obtained by the same steps as in Example 1.

[0326] The crystal structure of LiMO(2) is a layered rock salt type crystal structure. The compositional analysis of LiMO(2) was performed, and the results are as follows: in the composition formula (I), x = 0.05, y = 0.095, z = 0.023, and element X is Al.

[0327] (Example 3)

[0328] Except for adding sodium hydroxide aqueous solution dropwise in a timely manner so that the pH of the solution in the reaction tank becomes 11.5 (measurement temperature: 40°C), calcined product 3 was obtained by the same steps as in Example 1.

[0329] The slurry, prepared by mixing the above-mentioned calcined material 3 and pure water with the liquid temperature adjusted to 5°C at a mass ratio of 40% by mass of the calcined material to the total slurry, was stirred for 20 minutes, dehydrated, heat-treated at 250°C, and the residual water was dried after dehydration to obtain LiMO(3).

[0330] The crystal structure of LiMO(3) is a layered rock salt type. The compositional analysis of LiMO(3) was performed, and the results showed that in the composition formula (I), x = 0.04, y = 0.093, z = 0.022, and element X is Al.

[0331] (Comparative Example 1)

[0332] The mixture 1 obtained in Example 1 was used. The mixture 1 was put into a rotary kiln and heated at 680°C for 2 hours in an oxygen atmosphere to obtain the reaction product C1 of metal composite oxide 1 and lithium hydroxide.

[0333] Next, the obtained reactant C1 was fed into a rotary kiln. At this time, a gas with an oxygen concentration of 100% by volume was introduced from the outlet side of the rotary kiln towards the inlet side at an average linear velocity of 0.036 m / sec. The rotation speed of the rotary kiln drum was 1.22 rpm. The temperature of the atmosphere inside the kiln was set to 760°C and maintained for 2 hours to calcine reactant C1, yielding calcined product C1.

[0334] The slurry, prepared by mixing the above-mentioned calcined material C1 with pure water at a liquid temperature of 5°C in such a way that the mass of the calcined material relative to the total mass of the slurry is 40% by mass, is stirred for 20 minutes, dehydrated, heat-treated at 250°C, and then dried to obtain LiMO(C1).

[0335] The crystal structure of LiMO(C1) is a layered rock salt type. Compositional analysis of LiMO(C1) was performed, and the results showed that in composition formula (I), x = 0.04, y = 0.092, z = 0.022, and element X is Al.

[0336] (Comparative Example 2)

[0337] Mixture 1 obtained in Example 1 was used. Mixture 1 was placed in a roller hearth furnace and heated at 650°C for 5 hours in an oxygen atmosphere to obtain reactant C2.

[0338] Next, the obtained reactant C2 was placed into a roller hearth furnace. At this time, a gas with an oxygen concentration of 100% by volume was introduced. The temperature of the atmosphere inside the furnace was set to 720°C and maintained for 6 hours to calcine the reactant C2, obtaining calcined product C2.

[0339] The slurry, prepared by mixing the above-mentioned calcined material C2 with pure water at a liquid temperature of 5°C in a mass ratio of 30% by mass of the calcined material to the total slurry, was stirred for 20 minutes, dehydrated, and then heat-treated at 250°C. After dehydration, the residual water was dried to obtain LiMO(C2).

[0340] The crystal structure of LiMO(C2) is a layered rock salt type. Compositional analysis of LiMO(C2) was performed, and the results showed that in composition formula (I), x = 0.03, y = 0.092, z = 0.027, and element X is Al.

[0341] (Example 4)

[0342] After adding water to the reaction tank equipped with a stirrer and an overflow pipe, add an aqueous solution of sodium hydroxide and maintain the liquid temperature at 40°C.

[0343] A mixed raw material solution was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of aluminum sulfate in a molar ratio of Ni to Co to Al of 0.91:0.07:0.02.

[0344] Next, the mixed raw material solution and ammonium sulfate aqueous solution were continuously added to the reaction tank under stirring as a complexing agent. Sodium hydroxide aqueous solution was added dropwise at appropriate times to maintain the pH of the solution in the reaction tank at 12.1 (measurement temperature: 40℃) to obtain reaction precipitate 4.

[0345] After washing the reaction precipitate 4, it was dehydrated, dried and sieved to obtain a metal complex hydroxide 4 containing Ni, Co and Al.

[0346] Metal composite hydroxide 4 was heated at 650°C for 5 hours in an atmospheric atmosphere and then cooled to room temperature to obtain metal composite oxide 4.

[0347] Lithium hydroxide is weighed such that the amount of Li contained in metal composite oxide 4 is 1.10 relative to the total stoichiometry (molar ratio) of Ni, Co, and Al. Metal composite oxide 4 is mixed with lithium hydroxide to obtain mixture 4.

[0348] The mixture 4 was placed in an oxidizing atmosphere calcining furnace (manufactured by MOTOYAMA, trade name: SKA-3050F-SP) and heated at 650°C for 5 hours in an oxygen atmosphere to obtain the reaction product 4 of metal composite oxide 4 and lithium hydroxide.

[0349] Next, the obtained reactant 4 was placed into the aforementioned oxidizing atmosphere calcining furnace. At this time, a gas with an oxygen concentration of 100% by volume was introduced. The temperature of the atmosphere inside the calcining furnace was set to 720°C and maintained for 5 hours. This process of calcining reactant 4 was repeated twice to obtain calcined product 4. The 50% cumulative volume particle size D of calcined product 4... 50 It is 9.7 μm.

[0350] The slurry, prepared by mixing the above-mentioned calcined material 4 and pure water with the liquid temperature adjusted to 5°C at a mass ratio of 40% by mass relative to the total mass of the slurry, was stirred for 20 minutes, dehydrated, heat-treated at 250°C, and after drying the residual water, was mixed at a mass ratio of 50% by mass relative to the LiMO (C2) obtained in Comparative Example 2 to obtain LiMO (4).

[0351] The crystal structure of LiMO(4) is a layered rock salt type. The compositional analysis of LiMO(4) was performed, and the results showed that in the composition formula (I), x = 0.04, y = 0.082, z = 0.028, and element X is Al.

[0352] (Comparative Example 3)

[0353] Reactant 4, obtained in Example 4, was used. Reactant 4 was placed in an oxidizing atmosphere firing furnace (MOTOYAMA, trade name: SKA-3050-SP). An oxygen concentration of 100% by volume was introduced. The temperature of the atmosphere inside the firing furnace was set to 720°C and maintained for 5 hours to fire reactant 4, yielding fired product C3.

[0354] The slurry, prepared by mixing the above-mentioned calcined product C3 with pure water at a liquid temperature of 5°C at a mass ratio of 40% by mass relative to the total mass of the slurry, was stirred for 20 minutes, dehydrated, heat-treated at 250°C, and after drying the residual water, was mixed at a mass ratio of 50% by mass relative to the LiMO(C2) obtained in Comparative Example 2 to obtain LiMO(C3).

[0355] The crystal structure of LiMO(C3) is a layered rock salt type. Compositional analysis of LiMO(C3) was performed, and the results showed that in composition formula (I), x = 0.03, y = 0.081, z = 0.029, and element X is Al.

[0356] The firing apparatus and slurry concentration used in Examples 1-3 and Comparative Examples 1-2, and the D of LiMO(1)-(3) in Examples 1-3 and LiMO(C1)-(C2) in Comparative Examples 1-2 were compared. 50 、P S σ S 、P B σ B 、P S -P B σ S -σ B The cycle maintenance rates of coin-type half-cells using various LiMOs are shown in Table 1.

[0357]

[0358] In the firing process of Examples 1-3, small particles of the fired material scattered inside the drum are collected by a cyclone dust collector and reintroduced into the drum. These particles, reintroduced into the drum, undergo multiple firings, resulting in an increase in particle strength. As shown in Table 1, the P values ​​in Examples 1-3... S Become greater than P B , σ S Become greater than σ B In addition, P S -P B For pressures above 15 MPa, σ S -σ B The pressure is above 5 MPa. The cycle maintenance rate of the coin-type half-cell using such LiMO is above 88.7%.

[0359] On the other hand, as shown in Comparative Examples 1-2, in the absence of a cyclone dust collector in the firing apparatus and the failure to recover and re-input the scattered fired material, the cycle retention rate became a lower value than that of Examples 1-3.

[0360] Figure 4 This is a graph showing the relationship between particle size and particle intensity of LiMO in Example 1 and Comparative Example 1. Circles represent the results of LiMO in Example 1. Triangles represent the results of LiMO in Comparative Example 1. In the LiMO of Example 1, regarding D... 50 For particles smaller than 13.1 μm, there is a tendency for the maximum particle strength to be high, and a tendency for the inhomogeneity of particle strength to decrease as the particle size increases. Based on this result, it is believed that at least a portion of D... 50 The following particles are fired multiple times, and their particle strength increases.

[0361] In the case of LiMO in Comparative Example 1, no tendency was observed for particle intensity to vary depending on particle size.

[0362] The firing apparatus used in Example 4 and Comparative Example 3, the slurry concentration during washing, and the D of LiMO (4) in Example 4 and LiMO (C3) in Comparative Example 3 were compared. 50 、P S σ S 、P B σ B 、P S -P B σ S -σ B The cycle retention rates of coin-type half-cells using various LiMOs are shown in Table 2.

[0363]

[0364] The LiMO in Example 4 is a mixture of a first particle that underwent two firing processes and a second particle that underwent one firing process. Regarding this LiMO, P... S Become greater than P B , σ S Become greater than σ B In addition, P S -P B For pressures above 15 MPa, σ S -σ B The pressure is above 5 MPa. The cycle retention rate of the coin-type half-cell using the LiMO of Example 4 is 84.2%.

[0365] Comparative Example 3's LiMO was a mixture of particles that had undergone one calcination process. Regarding this LiMO, P... S Less than P B The cycle retention rate of the coin-type half-cell using the LiMO from Comparative Example 3 was 79.9%.

[0366] Industrial availability

[0367] According to the present invention, a lithium metal composite oxide that can be used as a CAM to obtain a lithium secondary battery with a high cycle retention rate, a CAM using the same, a positive electrode for a lithium secondary battery, and a lithium secondary battery are provided.

[0368] Symbol Explanation

[0369] 1: Separator, 2: Positive electrode, 3: Negative electrode, 4: Electrode assembly, 5: Battery can, 6: Electrolyte, 7: Top insulator, 8: Sealing body, 10: Lithium secondary battery, 21: Positive electrode lead, 31: Negative electrode lead, 400: Firing device, 41: Supply port, 42: Discharge port, 43: Roller, 44: Heating mechanism, 45, 49, 50: Piping, 46: Dust collector, 47: Discharge port, 48: Gas inlet, 100: Laminated body, 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, 200a: Opening, 1000: All-solid-state lithium secondary battery.

Claims

1. A lithium metal composite oxide, which is a particulate lithium metal composite oxide comprising a cumulative volumetric particle size D of 50% of the lithium metal composite oxide. 50 The following first particle and particle size exceed the stated D 50 The second particle, The D 50 2-20μm The average particle fracture strength P of the first particle S Greater than the average particle fracture strength P of the second particle B , The standard deviation σ of the particle fracture strength of the first particle S The standard deviation σ of the particle fracture strength of the second particle is greater than that of the second particle. B , The P S 50-110MPa The P B It is 20-60 MPa. The P S With the P B The difference is P S -P B Above 15MPa The lithium metal composite oxide is represented by formula (I). Li[Li x (Ni (1-y-z) CO y X z ) 1-x ]O2(I) In formula (I), X represents one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, Si, S and P, and satisfying -0.1≤x≤0.2, 0≤y≤0.4 and 0<z≤0.

5.

2. The lithium metal composite oxide according to claim 1, wherein, The P S With the P B The difference is P S -P B It is 17-65 MPa.

3. The lithium metal composite oxide according to claim 1 or 2, wherein, The σ S With the σ B The difference is σ S -σ B It is above 5 MPa.

4. The lithium metal composite oxide according to claim 1 or 2, wherein, The P S It is 60-105 MPa.

5. The lithium metal composite oxide according to claim 1 or 2, wherein, The P B It is 40-50 MPa.

6. The lithium metal composite oxide according to claim 1 or 2, wherein, The σ S It ranges from 20 to 90 MPa.

7. The lithium metal composite oxide according to claim 1 or 2, wherein, The σ B It is 10-30 MPa.

8. The lithium metal composite oxide according to claim 1 or 2, wherein its BET specific surface area is 0.1-2.0 m². 2 / g.

9. The lithium metal composite oxide according to claim 1 or 2, wherein, In the composition formula (I), x is greater than 0 and less than 0.

06.

10. The lithium metal composite oxide according to claim 1 or 2, wherein, The composition (I) satisfies 0 < y + z ≤ 0.

3.

11. A positive electrode active material for lithium secondary batteries, comprising any one of claims 1 to 10 lithium metal composite oxide.

12. A positive electrode for a lithium secondary battery, comprising the positive electrode active material for a lithium secondary battery as described in claim 11.

13. A lithium secondary battery having the positive electrode for a lithium secondary battery as described in claim 12.

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