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

Abstract

To provide a lithium metal composite oxide from which a lithium secondary battery with high rate characteristics and cycle characteristics can be obtained.SOLUTION: A lithium metal composite oxide includes: secondary particles that are aggregates of primary particles; and single particles that exist independently of the secondary particles. The lithium metal composite oxide has a layered rock salt structure, and is represented by the composition formula (I), and satisfies (1) and (2) below. (1): 1.2≤LA / LB<1.60 (where LA is a crystallite diameter obtained from a diffraction peak within a range of 2θ=18.8±1° in powder X-ray diffraction using CuKα rays, and LB is a crystallite diameter determined from a diffraction peak within a range of 2θ=38.3±1°.) (2): An Me occupancy at an Li site of the layered rock salt structure, which is obtained by analyzing the diffraction peaks by the Rietveld analysis method, is 2.5% or less. Me is Ni, Co, Mn or the element X1.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Lithium metal composite oxides are used as the positive electrode active material in the positive electrodes of lithium secondary batteries. The crystal shape and crystal structure of the particles of the lithium metal composite oxide affect various battery characteristics.

[0003] Lithium metal composite oxides have specific crystal faces that can contribute to the desorption and insertion of lithium ions. Lithium metal composite oxides having a crystal shape with a large proportion of such crystal faces tend to provide good battery characteristics as a positive electrode active material.

[0004] It is also known that a phenomenon called cation mixing occurs in lithium metal composite oxides having a layered rock-salt type crystal structure. Cation mixing refers to the site where Li should be, being occupied by a transition metal other than Li. Cation mixing is a phenomenon caused by the ionic radius of lithium ion and transition metal ion being similar. Here, transition metals are, for example, Ni, Co, Mn, etc.

[0005] A lithium metal composite oxide having a crystal structure with a small proportion of cation mixing is rich in lithium ions, and therefore the capacity of a lithium secondary battery is less likely to decrease.

[0006] As an attempt to focus on the crystal shape and crystal structure of lithium metal composite oxides, for example, Patent Document 1 describes a lithium nickel-containing composite oxide having octahedral primary particles and a layered rock salt type crystal structure. Patent Document 1 also discloses that the Li site occupancy rate in the 3a site of the layered rock salt type crystal structure is set to 96.0% or more, thereby reducing the proportion of cation mixing. Patent Document 1 also discloses that such a lithium nickel-containing composite oxide improves the cycle characteristics of lithium secondary batteries. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP-A-2017-226576 Summary of the Invention [Problem to be solved by the invention]

[0008] The crystal shape and crystal structure of the lithium metal composite oxide affect various battery characteristics, and therefore there is room for further study and improvement. The present invention has been made in view of the above circumstances, and aims to provide a lithium metal composite oxide that focuses on the crystal shape and crystal structure of the lithium metal composite oxide and that can provide a lithium secondary battery with excellent rate characteristics and cycle characteristics, as well as to provide 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. [Means for solving the problem]

[0009] An aspect of the present invention includes [1] to [9]. [1] A lithium metal composite oxide comprising secondary particles which are aggregates of primary particles and single particles which exist independently of the secondary particles, the lithium metal composite oxide having a layered rock-salt structure and represented by the following composition formula (I), and satisfying the following (1) and (2): Li x Ni 1-y-z-w Coy Mn z X1 w O 2 (I) (wherein 0.9≦x≦1.2, 0≦y≦0.4, 0≦z≦0.4, 0≦w≦0.1, y+z+w≦1, and X1 represents one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.) (1): 1.2≦L A / L B <1.60 (L A is the crystallite size determined from the diffraction peak 1 within the range of 2θ=18.8±1° in the powder X-ray diffraction obtained using CuKα radiation, and L B is the crystallite diameter determined from the diffraction peak 2 within the range of 2θ=38.3±1°. (2): The Me occupancy rate at the Li site of the layered rock-salt structure is 2.5% or less, as determined by analyzing the diffraction peaks by Rietveld analysis, and the Me is Ni, Co, Mn, or the element X1. [2] The lithium metal composite oxide according to [1], wherein z is 0≦z≦0.2. [3] BET specific surface area is 1.0m 2 / g or less. [4] The lithium metal composite oxide according to any one of [1] to [3], wherein the average particle size of the single particle is 2.0 μm or more and 10 μm or less. [5] The lithium metal composite oxide according to any one of [1] to [4], which satisfies the following (3): (3): 0.30≦P1 / D 50 (P1 is the average particle size (μm) of the single particle. D 50 is the 50% cumulative volume particle size (μm) of the lithium metal composite oxide obtained from a volume-based cumulative particle size distribution curve measured by a laser diffraction scattering method. [6] Said LB The lithium metal composite oxide according to any one of [1] to [5], wherein the thickness of the lithium metal composite oxide is 1000 Å or less. [7] A positive electrode active material for a lithium secondary battery, comprising the lithium metal composite oxide according to any one of [1] to [6]. [8] A positive electrode for a lithium secondary battery, comprising the positive electrode active material for a lithium secondary battery according to [7]. [9] A lithium secondary battery comprising the positive electrode for lithium secondary batteries according to [8]. Effect of the Invention

[0010] According to the present invention, it is possible to provide a lithium metal composite oxide which enables a lithium secondary battery having excellent rate characteristics and cycle characteristics to be obtained. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a lithium secondary battery. [Diagram 2] FIG. 1 is a schematic diagram illustrating an example of an all-solid-state lithium secondary battery. [Diagram 3] 1 is a SEM photograph of the lithium metal composite oxide produced in Example 1. [Figure 4] 3 is a SEM photograph of the lithium metal composite oxide produced in Example 2. [Diagram 5] 1 is a SEM photograph of a single particle of the lithium metal composite oxide produced in Example 3. [Figure 6] 1 is a SEM photograph including secondary particles of the lithium metal composite oxide produced in Example 3. [Figure 7] 1 is a SEM photograph of the lithium metal composite oxide produced in Example 4. [Figure 8] 2 is a SEM photograph of the lithium metal composite oxide produced in Comparative Example 1. [Figure 9] 3 is a SEM photograph of the lithium metal composite oxide produced in Comparative Example 2. [Figure 10] 1 is a SEM photograph of the lithium metal composite oxide produced in Comparative Example 3. [Figure 11] 1 is a SEM photograph of the lithium metal composite oxide produced in Comparative Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention relates to a lithium metal composite oxide that includes secondary particles that are aggregates of primary particles and single particles that exist independently of the secondary particles, has a layered rock-salt structure, is represented by composition formula (I), and satisfies (1) and (2). Details will be described later.

[0013] In this specification, the metal composite compound will be hereinafter referred to as "MCC". Lithium metal composite oxide is hereinafter referred to as "LiMO." Cathode active material for lithium secondary batteries is hereinafter referred to as "CAM."

[0014] "Ni" refers to nickel atoms, not nickel metal. Similarly, "Co" and "Li" refer to cobalt atoms and lithium atoms, etc., respectively.

[0015] In this specification, the rate characteristics and cycle characteristics of a lithium secondary battery are measured by the following methods.

[0016] [Measurement of rate characteristics and cycle characteristics] (Preparation of positive electrodes for lithium secondary batteries) The LiMO of this embodiment is used as the CAM. The CAM, conductive material, and binder are mixed in a ratio of CAM:conductive material:binder=92:5:3 (mass ratio) to prepare a paste-like positive electrode mixture. When preparing the positive electrode mixture, N-methyl-2-pyrrolidone is used as an organic solvent. Acetylene black is used as the conductive material. Polyvinylidene fluoride is used as the binder.

[0017] The obtained positive electrode mixture is applied to 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 a lithium secondary battery. The positive electrode area of ​​this positive electrode for a lithium secondary battery is 1.65 cm 2 Let us assume that.

[0018] (Production of lithium secondary batteries) The following operations are carried out in a glove box under an argon atmosphere. The positive electrode for lithium secondary batteries prepared in (Preparation of positive electrode for lithium secondary batteries) is placed on the bottom cover of a part for coin-type battery R2032 (manufactured by Hosen Co., Ltd.) with the aluminum foil side facing down, and a separator (porous film made of polyethylene) is placed on top of it. 300 μl of electrolyte is poured here. The electrolyte is a mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 30:35:35, with LiPF 6 A solution in which the above is dissolved at a ratio of 1.0 mol / l is used.

[0019] Next, metallic lithium is used as the negative electrode, and the negative electrode is placed on the top of the laminated film separator. The top lid is then placed on the laminated film separator via a gasket, and the battery is crimped with a crimping machine to produce a lithium secondary battery (coin-type half cell R2032).

[0020] The lithium secondary battery produced by the above method is used to measure the rate characteristics and cycle characteristics by the following methods.

[0021] (Rate characteristics) "Rate characteristics" refers to the ratio of the discharge capacity at 5 CA to the discharge capacity at 1 CA, which is taken as 100%. The higher this ratio, the higher the battery's output, which is preferable in terms of battery performance. In this specification, "rate characteristics" refers to the value obtained by performing a discharge rate test under the following conditions, and is evaluated as an index of discharge rate characteristics. "High rate characteristics" means that the ratio of the discharge capacity obtained by the following method exceeds 85%.

[0022] (Discharge rate test) Test temperature: 25℃ Maximum charging voltage 4.35V, charging current 1CA, constant current constant voltage charging Minimum discharge voltage 2.8V, discharge current 1CA or 5CA, constant current discharge

[0023] The discharge capacity when discharged at a constant current of 1 CA and the discharge capacity when discharged at a constant current of 5 CA were used to calculate the 5CA / 1CA discharge capacity ratio using the following formula, and this ratio was used as an index of discharge rate characteristics. (5CA / 1CA discharge capacity ratio) 5CA / 1CA discharge capacity ratio (%) = Discharge capacity at 5 CA / Discharge capacity at 1 CA x 100

[0024] (Cycle characteristics) The term "cycle characteristic" refers to the characteristic that the battery capacity decreases due to repeated charging and discharging. In this specification, the cycle retention rate measured by the following method is used as an index of the cycle characteristic. Moreover, "high cycle characteristic" refers to a cycle retention rate of more than 85%.

[0025] First, a coin-type half-cell lithium secondary battery is left standing at room temperature for 10 hours to allow the separator and the positive electrode mixture layer to be sufficiently impregnated with the electrolyte.

[0026] Next, constant current / constant voltage charging was performed at room temperature by charging at a constant current of 0.5 CA up to 4.35 V, followed by constant voltage charging at 4.35 V, and then constant current discharging was performed at 1 CA down to 2.8 V, thereby performing initial charging / discharging. The discharge capacity is measured, and the obtained value is regarded as the "initial discharge capacity" (mAh / g). The charge capacity is measured, and the obtained value is regarded as the "initial charge capacity" (mAh / g).

[0027] After the initial charge and discharge, charge at 0.5 CA and discharge at 1 CA are repeated under the same conditions as the initial charge and discharge. Then, measure the discharge capacity (mAh / g) at the 50th cycle.

[0028] The cycle retention rate is calculated from the initial discharge capacity and the discharge capacity at the 50th cycle using the following formula. The higher the cycle retention rate, the more desirable the battery performance is, since the decrease in capacity of the battery after repeated charging and discharging is suppressed. Cycle retention rate (%) = 50th cycle discharge capacity (mAh / g) ÷ initial discharge capacity (mAh / g) × 100

[0029] <limo> LiMO includes secondary particles and single particles. In this embodiment, a primary particle that does not aggregate and exists independently from other particles is referred to as a "single particle." In this embodiment, a primary particle that constitutes a secondary particle is referred to as a "primary particle." A primary particle that does not constitute a secondary particle is referred to as a "single particle."

[0030] In this specification, the term "primary particle" refers to a particle that does not have grain boundaries in appearance and that constitutes a secondary particle. More specifically, the term "primary particle" refers to a particle that constitutes a secondary particle and that does not have clear grain boundaries on the particle surface when the particle is observed at a magnification of 5,000 to 20,000 times using a scanning electron microscope or the like.

[0031] In this specification, the term "secondary particle" refers to a particle in which a plurality of the primary particles are three-dimensionally bonded together. The secondary particle has a spherical or nearly spherical shape. The "secondary particle" is a particle that has grain boundaries on its appearance. Generally, the secondary particles are formed by agglomeration of 10 or more primary particles.

[0032] In this specification, the term "single particle" refers to a particle that does not have grain boundaries in appearance and does not constitute a secondary particle. More specifically, the term "single particle" refers to a particle that exists independently of secondary particles and has no clear grain boundaries on the particle surface when the particle is observed in a field of view of 5000 times or more and 20000 times or less with a scanning electron microscope or the like.

[0033] In this specification, when two or more particles are adjacent to or overlapping each other, if no clear grain boundary is observed on the particle surface and if the particle does not have a spherical or approximately spherical shape, it is considered to be a "single particle."

[0034] The LiMO preferably has a single particle content of 20% or more in terms of number in the entire particle. When LiMO having a single particle content of 20% or more in the entire particle is used as a positive electrode active material for a lithium secondary battery, the proportion of the surface contributing to the desorption and insertion of lithium ions tends to be large, and lithium ion conduction tends to be smooth.

[0035] Moreover, LiMO with a single particle content of 20% or more in the entire particle means that the proportion of particles without grain boundaries is high among the entire particles. Such LiMO particles are less likely to break even when used in the positive electrode of a lithium secondary battery and are repeatedly charged and discharged. When particles are less likely to break, the conductive path is more likely to be maintained, and poor contact between particles and poor diffusion of lithium ions are less likely to occur. This makes it less likely that the rate characteristics and cycle characteristics will deteriorate.

[0036] The average particle size of the single particle is preferably 2.0 μm or more, more preferably 2.2 μm or more, and even more preferably 3.0 μm or more, and is preferably 10 μm or less, and more preferably 5.0 μm or less.

[0037] The upper limit and the lower limit of the average particle size of the single particles can be combined in any desired manner. The average particle size of the single particles is preferably from 2.0 μm to 10 μm, more preferably from 2.2 μm to 5.0 μm, and even more preferably from 3.0 μm to 5.0 μm.

[0038] The average particle size of the secondary particles is preferably 3.0 μm or more, more preferably 5.0 μm or more, and is preferably 15 μm or less, more preferably 10 μm or less.

[0039] The upper limit and the lower limit of the average particle size of the secondary particles can be combined in any desired manner. The average particle size of the secondary particles is preferably 3.0 μm or more and 15 μm or less, and more preferably 5.0 μm or more and 10 μm or less.

[0040] [Method for measuring the average particle size of single particles] The average particle size of the single particles can be measured by the following method.

[0041] First, LiMO is placed on a conductive sheet attached to a sample stage, and then a scanning electron microscope is used to irradiate the LiMO with an electron beam at an accelerating voltage of 15 kV for SEM observation. As a scanning electron microscope, for example, JSM-5510 manufactured by JEOL Ltd. can be used.

[0042] Next, 50 or more single particles are extracted from the obtained electron microscope image (SEM photograph) by the following method. At this time, particles in which no grain boundaries are visible are extracted as single particles. When two or more particles are adjacent to each other or overlap, particles in which no clear grain boundaries are visible on the particle surface and which do not have a spherical or nearly spherical shape are regarded as single particles.

[0043] (Single particle extraction method) When measuring the average particle size of single particles, all single particles included in one visual field are measured. If there are fewer than 50 single particles in one visual field, measurements are continued until the total number of single particles included in multiple visual fields is 50 or more.

[0044] For the image of the extracted single particle, a rectangle circumscribing the single particle is assumed, and the longitudinal dimension of the rectangle is taken as the particle diameter of the single particle.

[0045] The arithmetic mean value of the particle diameters of the obtained single particles is the average particle diameter of the single particles contained in LiMO.

[0046] (Secondary particle extraction method) When measuring the average particle size of secondary particles, all secondary particles included in one field of view are the measurement target. If the number of secondary particles included in one field of view is less than 50, measurements are continued until the total number of secondary particles included in multiple fields of view becomes 50 or more.

[0047] The average particle size of the secondary particles is measured in the same manner as for the single particles.

[0048] [Method for measuring the content of single particles based on number] The content of single particles based on the number of particles can be measured by observation using a scanning electron microscope (SEM). Specifically, first, an SEM photograph of one or more fields of view is taken, and then the total number of particles (the sum of single particles and secondary particles) and the number of single particles per field of view are counted. Next, the ratio of the number of single particles to the total number of particles is calculated as a percentage.

[0049] <Crystal structure> LiMO has a layered rock-salt type crystal structure. The layered rock-salt type crystal structure is a crystal structure in which lithium layers and transition metal layers other than lithium are alternately stacked with oxygen layers in between. That is, the layered rock-salt type crystal structure is a crystal structure in which transition metal ion layers and lithium only layers are alternately stacked with oxide ions interposed therebetween. Typically, α-NaFeO 2 This is the crystal structure of the type.

[0050] LiMO with this crystal structure has a (003) surface where lithium ions are difficult to desorb and insert, and a surface where lithium ions are easily desorbed and inserted. Surfaces where lithium ions are easily desorbed and inserted are surfaces other than the (003) surface, such as the (012) surface and the (104) surface. If the (012) surface and the (104) surface are exposed to the electrolyte, lithium ions can be desorbed and inserted more smoothly, which tends to improve the battery characteristics.

[0051] [How to confirm the crystal structure] The crystal structure of LiMO can be confirmed by observation using a powder X-ray diffraction measurement device. For the powder X-ray diffraction measurement, an X-ray diffraction device such as Ultima IV manufactured by Rigaku Corporation can be used.

[0052] ≪Composition formula≫ LiMO is represented by the following composition formula (I). Li x Ni 1-y-z-w Co y Mn z X1 w O 2 (I) (wherein 0.9≦x≦1.2, 0≦y≦0.4, 0≦z≦0.4, 0≦w≦0.1, y+z+w≦1, and X1 represents one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.)

[0053] (x) From the viewpoint of obtaining a lithium secondary battery having high cycle characteristics, x is preferably 0.9 or more, and more preferably 0.95 or more, and from the viewpoint of obtaining a lithium secondary battery having high initial coulombic efficiency, x is preferably 1.1 or less, and more preferably 1.05 or less. The upper and lower limits of x can be combined in any way. Examples of combinations of x include 0.9≦x≦1.1 and 0.95≦x≦1.05.

[0054] (y) From the viewpoint of obtaining a lithium secondary battery having a low internal resistance, y is preferably 0.005 or more, more preferably 0.01 or more, and even more preferably 0.05 or more. From the viewpoint of obtaining a lithium secondary battery having high thermal stability, y is preferably 0.4 or less, more preferably 0.35 or less, and even more preferably 0.33 or less. The upper and lower limits of y can be combined in any way. Examples of combinations of y include 0.005≦y≦0.4, 0.01≦y≦0.35, and 0.05≦y≦0.33.

[0055] (z) From the viewpoint of obtaining a lithium secondary battery having high cycle characteristics, z is preferably 0 or more, more preferably 0.01 or more, and even more preferably 0.02 or more. From the viewpoint of obtaining a lithium secondary battery having high storage characteristics at high temperatures (for example, in a 60° C. environment), z is preferably 0.2 or less, more preferably 0.19 or less, and even more preferably 0.18 or less. The upper and lower limits of z can be combined in any desired manner. As an example of a combination, z is preferably 0≦z≦0.2, more preferably 0.01≦z≦0.19, and further preferably 0.02≦z≦0.18.

[0056] From the viewpoint of obtaining a lithium secondary battery with high cycle characteristics, X1 is preferably one or more elements selected from the group consisting of Ti, Mg, Al, W, B, Zr, and Nb, and from the viewpoint of obtaining a lithium secondary battery with high thermal stability, X1 is preferably one or more elements selected from the group consisting of Al, W, B, Zr, and Nb.

[0057] (w) From the viewpoint of obtaining a lithium secondary battery having high cycle characteristics, w is preferably 0.01 or more, more preferably 0.02 or more, and even more preferably 0.03 or more. Also, from the viewpoint of obtaining a lithium secondary battery having high storage characteristics at high temperatures (e.g., in a 60°C environment), w is preferably 0.09 or less, more preferably 0.08 or less, and even more preferably 0.07 or less. The upper and lower limits of z can be combined in any desired manner. Examples of combinations of w include 0.01≦w≦0.09, 0.02≦w≦0.08, and 0.03≦w≦0.07.

[0058] [Composition analysis] The composition of LiMO can be analyzed by dissolving the obtained LiMO powder in hydrochloric acid and then measuring it using an ICP optical emission spectrometer. As an ICP emission spectrometer, for example, SPS3000 manufactured by SII NanoTechnology Inc. can be used.

[0059] (1) LiMO satisfies the following (1). (1): 1.2≦L A / L B <1.60 (L A is the crystallite size determined from the diffraction peak 1 within the range of 2θ=18.8±1° in the powder X-ray diffraction obtained using CuKα radiation, and L B is the crystallite diameter determined from the diffraction peak 2 within the range of 2θ=38.3±1°.

[0060] L A is the crystallite diameter of the (003) plane, and L B is the crystallite size of the (012) plane.

[0061] [Crystallite diameter L A and L B Measurement method] Crystallite size L A and L B can be measured by powder X-ray diffraction measurement. The powder X-ray diffraction measurement may be carried out using an X-ray diffraction device, for example, Ultima IV manufactured by Rigaku Corporation.

[0062] Specifically, first, LiMO powder is filled into a dedicated substrate and measured using a Cu-Kα radiation source to obtain a powder X-ray diffraction pattern. An example of the measurement conditions is described below.

[0063] (Measurement conditions) Diffraction angle 2θ=10°~90° Sampling width 0.02° Scan speed: 4° / min

[0064] Using the integrated powder X-ray analysis software JADE, the crystallite diameter L was calculated from the diffraction peak 1 in the range of 2θ = 18.8 ± 1° from the obtained powder X-ray diffraction pattern. A and the crystallite diameter L obtained from the diffraction peak 2 within the range of 2θ=38.3±1° B Request.

[0065] The obtained L A and L B From the comparison, A / L B Request.

[0066] LiMO is 1.21≦L A / L B ≦1.59, and 1.22≦L A / L B It is more preferable that the ratio satisfies ≦1.55.

[0067] As described above, the (012) plane is a plane from which lithium ions can be desorbed and inserted. Ratio L A / L B When the surface area is equal to or less than the upper limit, the ratio of the (012) plane to the (003) plane is large, which means that there are many planes from which lithium ions can be desorbed and inserted. In this case, the rate characteristics and cycle characteristics are likely to be improved.

[0068] Ratio L A / L B is equal to or greater than the lower limit, this means that the particles have grown to an appropriate shape and size. As the crystal growth progresses, the crystal shape changes from a hexagonal flat plate shape to an octahedral shape. LiMO with an octahedral crystal shape allows lithium ions to enter and exit more easily than LiMO with a hexagonal flat plate shape. On the other hand, as seen in Patent Document 1, octahedral particles with significant particle growth tend to cause poor contact between particles, resulting in a decrease in rate characteristics and cycle characteristics. In addition, such excessive particle growth tends to cause poor diffusion of lithium ions. For this reason, the ratio L A / L B LiMO having a valence rate of 100% or more is less susceptible to deterioration in rate characteristics and cycle characteristics.

[0069] (1) specifies the ratio of the (003) plane to the (012) plane. As mentioned above, the planes that facilitate the desorption and insertion of lithium ions are other than the (003) plane, such as the (012) plane and the (104) plane. The (012) plane is the plane that is most likely to contribute to the desorption and insertion of lithium ions.

[0070] For example, although the (104) plane can contribute to the desorption and insertion of lithium ions, it is known that when a large proportion of the (104) plane is exposed on the surface, Ni is more likely to segregate on the surface of LiMO.

[0071] The inventors focused on the crystallite size of the (012) plane among the multiple crystal planes, and found that when the ratio to the (003) plane satisfies a specific range, both cycle characteristics and rate characteristics can be achieved.

[0072] The L in LiMO B is preferably 1000 Å or less, more preferably 980 Å or less, and even more preferably 950 Å or less. B The lower limit of the thickness is, for example, 100 Å or more, 200 Å or more, or 300 Å or more. L B The upper and lower limits of the above can be arbitrarily combined. An example of the combination is 100 Å≦L B ≦1000Å, 200Å≦L B ≦980Å, 300Å≦L B ≦950 Å.

[0073] The L in LiMO B When is equal to or less than the upper limit, it means that the crystal growth of LiMO has progressed moderately and the (012) plane is likely to appear on the surface of the particle.

[0074] (2) LiMO satisfies the following (2). (2): The Me occupancy rate at the Li site of the layered rock-salt structure, as determined by analyzing the diffraction peaks by Rietveld analysis, is 2.5% or less, preferably 2.0% or less, and more preferably 1.7% or less. The lower limit of the Me occupancy rate at the Li site is, for example, more than 0%, such as 0.1% or more and 0.2% or more. The Me occupancy rate at the Li site may be more than 0% and not more than 2.5%, 0.1% or more and 2.0% or less, or 0.2% or more and 1.7% or less.

[0075] Me is Ni, Co, Mn, or the above element X1.

[0076] (2) is specifically, LiMO (Li 1-n Me n )(Me 1-n Li n )O 2 This means that n, the Me occupancy rate obtained from the Rietveld analysis of powder X-ray diffraction, is 0.25 or less.

[0077] LiMO that satisfies (2) has a low occupancy rate of Me, i.e., a high occupancy rate of Li. In such LiMO, the rate characteristics are less likely to deteriorate because Me does not inhibit the movement (desorption and insertion) of Li during charging and discharging. In addition, in LiMO that satisfies (2), cation mixing is not progressing, so the crystal structure is not easily disturbed and the layered rock-salt structure is easily maintained, so that the cycle characteristics are not easily deteriorated.

[0078] As cation mixing progresses, the layered rock-salt structure is likely to change to a rock-salt structure. In the rock-salt structure, the cations are arranged irregularly, which means there are fewer diffusion paths for lithium ions, and the electrochemical properties, such as rate characteristics and cycle characteristics, are likely to deteriorate.

[0079] [Rietveld refinement method] The Me occupancy rate at the Li site can be obtained by performing Rietveld analysis on the diffraction peaks obtained from the X-ray diffraction data, setting the Me occupancy rate in the layered rock salt crystal structure as n and the Li occupancy rate as 1-n. For the Rietveld analysis, for example, Bruker TOPAS can be used.

[0080] (3) It is preferable that LiMO satisfies the following (3). (3): 0.30≦P1 / D 50 (P1 is the average particle size of a single particle (μm). D 50 is the 50% cumulative volume particle size (μm) of the lithium metal composite oxide obtained from the volume-based cumulative particle size distribution curve measured by the laser diffraction scattering method.

[0081] P1 / D 50 is preferably 0.25 or more, more preferably 0.30 or more, and even more preferably 0.40 or more. 50 is preferably 1.40 or less, more preferably 1.30 or less, and even more preferably 1.20 or less. P1 / D 50 0.25≦P1 / D 50 ≦1.40 is preferable, and 0.30≦P1 / D 50 ≦1.30 is more preferable, and 0.40≦P1 / D 50 ≦1.20 is even more preferred.

[0082] The larger the particle size of the secondary particles of LiMO, the greater the P1 / D 50 P1 / D is a small value. 50 When the ratio is 0.3 or more, the particle size of the secondary particles is not too large, and therefore, even if the primary particles of LiMO expand or contract due to the absorption and desorption reactions of lithium ions during repeated charging and discharging of the lithium secondary battery, cracks are unlikely to occur at the grain boundaries between the primary particles of LiMO, and good cycle characteristics can be obtained.

[0083] (3) is preferably, for example, (3)-1. (3)-1:0.30≦P1 / D 50 ≦1.40

[0084] [Method for measuring cumulative volumetric particle size] The "volume-based cumulative particle size distribution" can be measured by a measurement method using a laser diffraction scattering method as its measurement principle. A particle size distribution measurement using a laser diffraction scattering method as its measurement principle is called a "laser diffraction particle size distribution measurement." Specifically, the cumulative particle size distribution of the metal composite hydroxide or LiMO described below is measured by the following measurement method.

[0085] First, 0.1 g of a metal composite hydroxide or LiMO is added to 50 ml of a 0.2 mass % aqueous solution of sodium hexametaphosphate to obtain a dispersion in which the metal composite hydroxide or LiMO is dispersed.

[0086] Next, the particle size distribution of the obtained dispersion is measured using a laser diffraction scattering particle size distribution measuring device to obtain a volume-based cumulative particle size distribution curve. The measurement range of the particle size distribution is 0.02 μm or more and 2000 μm or less.

[0087] As a laser diffraction scattering particle size distribution measuring device, for example, Microtrack MT3300EXII manufactured by Microtrack Bell Co., Ltd. can be used.

[0088] In the obtained cumulative particle size distribution curve, the particle size value at the point where the cumulative volume from the fine particle side is 10% when the whole is 100% is called the 10% cumulative volume particle size D 10 (μm), the particle size at the 50% point is the 50% cumulative volumetric particle size D 50 (μm), the particle size at the 90% point is the 90% cumulative volumetric particle size D 90 (μm).

[0089] (4) LiMO has a BET specific surface area of ​​1.0 m 2 / g or less is preferable.

[0090] The lower limit of the BET specific surface area is 0.20 m 2 / g or more is preferable, and 0.30m 2 / g or more is more preferable, and 0.35m 2 / g or more is particularly preferred.

[0091] The upper limit of the BET specific surface area is 0.99 m 2 / g or less is preferable, and 0.80m 2 / g or less is more preferable, and 0.70m 2 / g or less is particularly preferred.

[0092] The above upper and lower limits of the BET specific surface area can be combined in any desired manner. As an example of a combination, the BET specific surface area is 0.20 m 2 / g or more 0.99m 2 / g or less, 0.30m 2 / g or more 0.80m 2 / g or less, 0.35m 2 / g or more 0.70m 2 / g or less.

[0093] LiMO having a BET specific surface area in the above range is likely to have improved electrical conductivity, and therefore is less likely to experience a decrease in cycle characteristics.

[0094] [Method for measuring BET specific surface area] The BET specific surface area can be measured by the following method. 1 g of LiMO is dried in a nitrogen atmosphere at 105°C for 30 minutes, and then measured using a BET specific surface area measuring device. As a BET specific surface area measuring device, for example, Macsorb (registered trademark) manufactured by Mountec Co., Ltd. can be used.

[0095] <Method of manufacturing lithium metal composite oxide> The method for producing LiMO preferably includes a step of obtaining MCC and a step of obtaining LiMO. Hereinafter, the step of obtaining MCC and the step of obtaining LiMO will be described in this order.

[0096] <Process to obtain MCC> First, an MCC containing a metal element other than lithium, that is, Ni, and optional metals Co, Mn, and element X1 is prepared. In preparing MCC, a metal composite hydroxide is first produced. The metal composite hydroxide can be produced by a commonly known batch coprecipitation method, a semi-continuous method (semi-batch method), or a continuous coprecipitation method. In this embodiment, the metal composite hydroxide is preferably produced by a semi-continuous method. Hereinafter, the production method will be described in detail using a metal composite hydroxide containing Ni, Co, and Mn as metals as an example.

[0097] [Semi-continuous method] A method for producing the precursor in a semi-continuous manner will now be described. Specifically, first, nuclei of precursor particles are generated, and then the nuclei are grown.

[0098] The precursor may be a metal composite hydroxide containing Ni, Co, and Al, or a metal composite hydroxide containing Ni, Co, and Mn.

[0099] Examples of metal source liquids for producing a precursor containing Ni, Co, and Mn include a nickel salt solution, a cobalt salt solution, and a manganese salt solution.

[0100] Examples of metal source liquids for producing a precursor containing Ni, Co, and Al include a nickel salt solution, a cobalt salt solution, and an aluminum salt solution.

[0101] Hereinafter, an example of producing a metal composite hydroxide containing Ni, Co, and Mn as a precursor will be described. The metal composite hydroxide containing Ni, Co, and Mn is sometimes referred to as nickel-cobalt-manganese metal composite hydroxide.

[0102] [Nucleation process] The metal raw material mixture, complexing agent and alkaline aqueous solution are reacted to produce Ni 1-x-y Co x Mn y (OH) 2 The mixed metal source solution is a mixed solution of a nickel salt solution, a cobalt salt solution, and a manganese salt solution.

[0103] The metal raw material mixture, the complexing agent, and the alkaline aqueous solution are each continuously and simultaneously fed into a reaction vessel equipped with a stirrer, whereby nuclei are formed.

[0104] In the semi-continuous method, in order to adjust the pH value of the metal raw material mixture and the mixture containing the complexing agent, an alkaline aqueous solution is added to the mixture before the pH of the mixture becomes neutral from alkaline. The alkaline aqueous solution may be sodium hydroxide or potassium hydroxide. The complexing agent is a compound capable of forming a complex with nickel ions and cobalt ions in an aqueous solution. Examples of the complexing agent include ammonium ion donors, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine. Examples of the ammonium ion donors include ammonium salts such as ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride.

[0105] In this specification, the pH value is defined as the value measured when the temperature of the mixed liquid is 40° C. The pH of the mixed liquid is measured when the temperature of the mixed liquid sampled from the reaction tank reaches 40° C.

[0106] If the temperature of the sampled mixed liquid is lower than 40°C, heat the mixed liquid and measure the pH when it reaches 40°C. If the temperature of the sampled mixed liquid is higher than 40°C, cool the mixed liquid and measure the pH when it reaches 40°C.

[0107] During the reaction, the temperature of the reaction vessel is controlled within the range of, for example, 20°C or higher and 80°C or lower, preferably 30°C or higher and 70°C or lower.

[0108] In the nucleation step, the pH value in the reaction tank is controlled within the range of, for example, pH 10 or more and pH 13 or less, preferably pH 11 or more and pH 13 or less.

[0109] During the nucleation step, the materials in the reaction vessel are mixed by stirring. As an example of the stirring rotation speed, the stirring rotation speed is preferably more than 1000 rpm, more preferably 1100 rpm or more, and even more preferably 11500 rpm or more. By stirring under such stirring conditions, the supplied raw material liquids are likely to be mixed uniformly.

[0110] In the nucleation step, the concentration of the complexing agent in the reaction tank is controlled within the range of, for example, 0.1 g / L to 15.0 g / L, preferably 1.0 g / L to 12.0 g / L.

[0111] After a certain time has elapsed from the start of the nucleation step, various conditions are changed to the reaction conditions of the nucleus growth step described below. The certain time is preferably adjusted appropriately depending on the amount of the raw material liquid fed and the slurry concentration in the reaction tank. In general, it is preferably 0.1 hours or more and 10 hours or less.

[0112] [Nuclear growth process] After the nucleation step is completed, the metal raw material mixture, the complexing agent, and the alkaline aqueous solution are continuously fed into the same reaction vessel as that in which the nucleation step was carried out, thereby growing the nuclei.

[0113] The concentration of the complexing agent in the reaction vessel in the nucleus growth step is preferably in the same range as in the nucleation step, and the pH in the nucleus growth step is controlled, for example, within the range of pH 9 to 12, preferably pH 9 to 11.5.

[0114] In the nucleus growth step, the materials in the reaction vessel are preferably stirred and mixed under the same stirring conditions as those in the nucleation step.

[0115] An overflow type reaction tank is used to separate the generated nuclei. The generated nuclei overflow from the reaction tank and are concentrated by settling in a settling tank connected to the overflow pipe. The concentrated nuclei-containing slurry is returned to the reaction tank, where the nuclei are grown again.

[0116] In the nucleus growth step, the nucleus-containing slurry in the reaction tank is sampled as appropriate, and the supply of the metal raw material mixture, the complexing agent, and the alkaline aqueous solution is stopped when the desired physical properties are achieved. The slurry in the reaction tank at the time when the supply of each liquid is stopped becomes a slurry containing the target nickel-cobalt-manganese metal composite hydroxide.

[0117] Through the above-mentioned steps, a slurry containing nickel-cobalt-manganese metal composite hydroxide is obtained as the metal composite hydroxide-containing slurry.

[0118] [Dehydration process] After the above reaction, the obtained slurry containing the nickel-cobalt-manganese metal composite hydroxide is washed and then dried to obtain a precursor of the nickel-cobalt-manganese metal composite hydroxide.

[0119] When isolating the precursor, a method in which the slurry containing the metal composite hydroxide is dehydrated by centrifugation, suction filtration, or the like is preferable.

[0120] The precursor obtained by dehydration is preferably washed with a washing solution containing water or an alkali. In this embodiment, washing with a washing solution containing an alkali is preferable, and washing with a sodium hydroxide solution is more preferable.

[0121] [Drying process] The precursor obtained by the above dehydration step is dried in an air atmosphere at a temperature of 105° C. to 200° C. for 1 hour to 20 hours.

[0122] In the above example, a metal composite hydroxide is produced as a precursor, but a metal composite oxide may be prepared by heating a metal composite hydroxide.

[0123] [Continuous co-precipitation method] The precursors can also be prepared using sequential co-precipitation techniques.

[0124] Specifically, there is mentioned a method for producing a metal composite hydroxide by the continuous coprecipitation method described in JP-A-2002-201028.

[0125] When producing a precursor by the continuous coprecipitation method, the same raw material liquid, alkali, and complexing agent as those in the semi-continuous method are preferably used. During the reaction, the pH value in the reaction vessel is preferably set within a range of, for example, 9 to 13, and is preferably controlled within a range of ±0.03 of the set pH value.

[0126] The reaction vessel used in the continuous coprecipitation method may be an overflow type reaction vessel for separating the reaction precipitate formed.

[0127] By appropriately controlling the concentration of the metal salt supplied to the reaction tank, the reaction temperature, the reaction pH, etc., the physical properties of the obtained precursor can be controlled within a desired range.

[0128] By the above steps, a slurry containing nickel-cobalt-manganese metal composite hydroxide is obtained as a slurry containing metal composite hydroxide. As for the dehydration step and the drying step, the same method as in the semi-continuous method is preferably used.

[0129] [Crushing and classification process] If necessary, the obtained nickel-cobalt-manganese metal composite hydroxide is crushed and classified to obtain the particle size distribution (D H90 -D H10 ) / D H50 It is also possible to adjust H50 is the 50% cumulative volume particle size of the metal complex hydroxide obtained from the volume-based cumulative particle size distribution curve measured by the laser diffraction scattering method, and D H10 is the 10% cumulative volumetric grain size, and D H90 is the 90% cumulative volumetric grain size.

[0130] Metal complex hydroxides are H50 , D H10 , and D H90 It is preferable that the particle size distribution satisfies the following formula: (D H90 -D H10 ) / D H50 <= 1.0

[0131] Metal composite hydroxides that satisfy the above particle size distribution tend to react uniformly with lithium compounds. In this case, cation mixing is unlikely to occur, making it easier to produce LiMO that satisfies the above (2).

[0132] Next, the nickel-cobalt-manganese metal composite hydroxide is oxidized to prepare a metal composite oxide, that is, a nickel-cobalt-manganese metal composite oxide. Specifically, it is preferable to oxidize the nickel-cobalt-manganese metal composite hydroxide by heating it. The heating temperature for oxidation is preferably 400° C. or more and 700° C. or less, and more preferably 450° C. or more and 680° C. or less. If necessary, a plurality of heating steps may be performed.

[0133] When a metal composite hydroxide is heated at a temperature of 800°C or higher, the calcination proceeds excessively, and the transition metals tend to be arranged irregularly. When such a metal composite oxide is mixed with a lithium compound and calcined, cation mixing tends to proceed.

[0134] On the other hand, metal composite oxides produced by heating at temperatures below 800°C tend to have a crystal structure in which transition metals are regularly arranged. When such metal composite oxides are mixed with lithium compounds and sintered, cation mixing is unlikely to occur, making it easier to produce LiMO that satisfies the above (2).

[0135] The retention time for oxidation may be 0.1 hours or more and 20 hours or less, preferably 0.5 hours or more and 10 hours or less. The rate of temperature increase to the heating temperature is, for example, 50° C. / hour or more and 400° C. / hour or less, and the rate of temperature decrease from the heating temperature to room temperature is, for example, 10° C. / hour or more and 400° C. / hour or less. The heating atmosphere may be air, oxygen, nitrogen, argon, or a mixture of these gases.

[0136] The inside of the heating device may be an atmosphere containing a moderate amount of oxygen. The oxidizing atmosphere may be an oxygen-containing atmosphere in which an oxidizing gas is mixed with an inert gas, or an oxidizing agent may be present in an inert gas atmosphere. By providing a moderate oxidizing atmosphere inside the heating device, the transition metal contained in the metal composite hydroxide is appropriately oxidized, making it easier to control the form of the metal composite oxide.

[0137] The oxygen or oxidizing agent in the oxidizing atmosphere should be sufficient to contain oxygen atoms sufficient to oxidize the transition metal.

[0138] When the oxidizing atmosphere is an oxygen-containing atmosphere, the atmosphere in the reaction vessel can be controlled by, for example, passing an oxidizing gas through the reaction vessel or bubbling an oxidizing gas through the mixed liquid.

[0139] As the oxidizing agent, peroxides such as hydrogen peroxide, peroxide salts such as permanganate, perchlorates, hypochlorites, nitric acid, halogens, ozone, or the like can be used.

[0140] <<The process of obtaining LiMO>> The metal composite oxide obtained by the above method is mixed with a lithium compound to obtain a mixture of the metal composite oxide and the lithium compound. As the lithium compound, one or more compounds selected from the group consisting of lithium carbonate, lithium hydroxide, and lithium hydroxide monohydrate can be used.

[0141] The lithium compound and the metal composite oxide are mixed in consideration of the composition ratio of the final target product to obtain a mixture. Specifically, the lithium compound and the metal composite oxide are preferably mixed in a ratio corresponding to the composition ratio of the composition formula (I) above.

[0142] In this embodiment, when the metal composite oxide and the lithium compound are mixed, it is preferable to mix an inactive flux at the same time.

[0143] By firing the mixture containing the metal composite oxide, the lithium compound, and the inert flux, the mixture of the metal composite oxide and the lithium compound is fired in the presence of the inert flux.

[0144] By firing the mixture of the metal composite oxide and the lithium compound in the presence of an inert flux, the formation of secondary particles in which primary particles are sintered together is prevented, and the growth of single particles can be promoted.

[0145] Furthermore, by sintering a mixture of a metal composite oxide and a lithium compound in the presence of an inert flux, the particles tend to grow, making it possible to produce LiMO that satisfies (1).

[0146] LiMO is obtained by firing the mixture of the metal composite oxide and the lithium compound. Dry air, an oxygen atmosphere, an inert atmosphere, etc. are used for firing. The firing process may have multiple firing stages with different firing temperatures. For example, it may have a first firing stage and a second firing stage in which firing is performed at a higher temperature than the first firing stage. It may also have firing stages with different firing temperatures and firing times.

[0147] In this specification, the firing temperature means the temperature of the atmosphere in the firing furnace, and also means the maximum holding temperature in the main firing step. Hereinafter, the "maximum holding temperature" may be referred to as the maximum holding temperature. When the main firing step has a plurality of heating steps, the firing temperature means the temperature when heated at the maximum holding temperature in each heating step.

[0148] The firing time is preferably 1 hour or more and 30 hours or less in total time from the start of temperature rise to the end of temperature hold after reaching the maximum holding temperature. The temperature rise rate in the firing process to reach the maximum holding temperature is usually 50°C / hour or more and 400°C / hour or less, and the temperature drop rate from the holding temperature to room temperature is usually 10°C / hour or more and 400°C / hour or less. In particular, the temperature rise rate is preferably 80°C / hour or more, more preferably 100°C / hour or more, and particularly preferably 150°C / hour or more. The temperature rise rate is calculated from the time from the start of temperature rise in the firing device to the time when the maximum holding temperature is reached and the temperature difference from the temperature at the start of temperature rise in the firing furnace of the firing device to the maximum holding temperature.

[0149] By adjusting the holding temperature during sintering, the particle size of the resulting LiMO single particles can be controlled within the preferred range of this embodiment.

[0150] Generally, the higher the holding temperature, the larger the particle size of the single particle and the smaller the BET specific surface area. The holding temperature during firing may be appropriately adjusted depending on the type and amount of the transition metal element, precipitant, and inert flux used.

[0151] The holding temperature may be set taking into consideration the melting point of the inactive melting agent described below, and is preferably set within the range of from 200° C. below the melting point of the inactive melting agent to 200° C. above the melting point of the inactive melting agent.

[0152] Specifically, the holding temperature can be in the range of 200° C. or higher and 1150° C. or lower, preferably 300° C. or higher and 1050° C. or lower, and more preferably 500° C. or higher and 1000° C. or lower.

[0153] The time for holding at the holding temperature is, for example, from 0.1 hours to 20 hours, and preferably from 0.5 hours to 10 hours. The firing atmosphere may be air, oxygen, nitrogen, argon, or a mixture of these gases.

[0154] In the above firing, a commercially available inactive flux may be used.

[0155] The inactive flux is not particularly limited as long as it is unlikely to react with the mixture during firing. In this embodiment, the inactive flux may be one or more selected from the group consisting of fluorides of one or more elements (hereinafter referred to as "A") selected from the group consisting of Na, K, Rb, Cs, Ca, Mg, Sr, and Ba, chlorides of A, carbonates of A, sulfates of A, nitrates of A, phosphates of A, hydroxides of A, molybdates of A, and tungstates of A.

[0156] The fluorides of A are NaF (melting point: 993°C), KF (melting point: 858°C), RbF (melting point: 795°C), CsF (melting point: 682°C), CaF 2 (Melting point: 1402℃), MgF 2 (Melting point: 1263℃), SrF 2 (melting point: 1473°C) and BaF 2 (melting point: 1355°C).

[0157] The chlorides of A include NaCl (melting point: 801°C), KCl (melting point: 770°C), RbCl (melting point: 718°C), CsCl (melting point: 645°C), CaCl2 (melting point: 782°C), MgCl 2 (Melting point: 714℃), SrCl 2 (melting point: 857°C) and BaCl 2 (melting point: 963°C).

[0158] The carbonate of A is Na 2 CO 3 (Melting point: 854℃), K 2 CO 3 (Melting point: 899℃), Rb 2 CO 3 (Melting point: 837℃), Cs 2 CO 3 (Melting point: 793°C), CaCO 3 (Melting point: 825℃), MgCO 3 (Melting point: 990℃), SrCO 3 (Melting point: 1497°C) and BaCO 3 (melting point: 1380°C).

[0159] The sulfate of A is Na 2 SO 4 (Melting point: 884℃), K 2 SO 4 (Melting point: 1069℃), Rb 2 SO 4 (Melting point: 1066℃), Cs 2 SO 4 (Melting point: 1005°C), CaSO 4 (Melting point: 1460℃), MgSO 4 (Melting point: 1137°C), SrSO 4 (Melting point: 1605°C) and BaSO 4 (melting point: 1580°C).

[0160] The nitrate of A is NaNO 3 (Melting point: 310℃), KNO 3 (Melting point: 337°C), RbNO 3 (Melting point: 316°C), CsNO 3 (Melting point: 417°C), Ca(NO 3 ) 2 (Melting point: 561°C), Mg(NO 3 ) 2 , Sr(NO 3 ) 2 (Melting point: 645°C) and Ba(NO 3 ) 2 (melting point: 596°C).

[0161] The phosphate salt of A is Na 3 PO 4 , K 3 PO 4 (Melting point: 1340℃), Rb 3 PO 4 , Cs 3 PO 4 , Ca 3 (PO 4 ) 2 , Mg 3 (PO 4 ) 2 (Melting point: 1184℃), Sr 3 (PO 4 ) 2 (Melting point: 1727℃) and Ba 3 (PO 4 ) 2 (melting point: 1767°C).

[0162] The hydroxides of A are NaOH (melting point: 318°C), KOH (melting point: 360°C), RbOH (melting point: 301°C), CsOH (melting point: 272°C), and Ca(OH). 2 (Melting point: 408°C), Mg(OH) 2 (Melting point: 350°C), Sr(OH) 2 (Melting point: 375°C) and Ba(OH) 2 (melting point: 853°C).

[0163] The molybdate salt of A is Na 2 MoO 4 (Melting point: 698℃), K 2 MoO 4 (Melting point: 919℃), Rb 2 MoO 4 (Melting point: 958℃), Cs 2 MoO 4 (Melting point: 956℃), CaMoO 4 (Melting point: 1520℃), MgMoO 4 (Melting point: 1060℃), SrMoO 4 (Melting point: 1040℃) and BaMoO 4 (melting point: 1460°C).

[0164] The tungstate salt of A is Na 2 WO 4 (Melting point: 687℃), K 2 WO 4 , Rb 2 WO 4 , Cs 2 WO 4 , CaWO 4 , MgWO 4 , SrWO 4 and BaWO 4 The following can be mentioned.

[0165] In the present embodiment, two or more of these inactive fluxes may be used. When two or more of them are used, the melting point of the entire inactive flux may be lowered.

[0166] Among these inert fluxes, one or more salts selected from the group consisting of carbonates of A, sulfates of A, and chlorides of A are preferred as inert fluxes for obtaining a lithium metal composite oxide with higher crystallinity.

[0167] Also, A is preferably either or both of sodium (Na) and potassium (K).

[0168] That is, among the above inert fluxes, particularly preferred inert fluxes are NaCl, KCl, Na 2 CO 3 , K 2 CO 3 , Na 2 SO 4 , and K 2 SO 4 Preferably, one or more selected from the group consisting of 2 SO 4 and K 2 CO 3 It is more preferable to use either one or both of the above.

[0169] The amount of the inactive flux used during firing is preferably such that the ratio of the number of moles of the inactive flux to the total number of moles of the lithium compound and the inactive flux is 0.06 or more and 30 or less, more preferably 0.10 or more and 20 or less, and even more preferably 0.10 or more and 15 or less.

[0170] In addition, in order to optionally accelerate the crystal growth, an inactive melting agent other than the inactive melting agents listed above may be used in combination. Such an inactive melting agent may be NH 4 Cl, NH 4 Examples of the ammonium salt include ammonium salts of F.

[0171] The inactive flux may remain in the LiMO after the calcination, or may be removed by washing with water or alcohol after the calcination. It is preferable to wash the LiMO after the calcination with water or alcohol.

[0172] <Positive electrode active material for lithium secondary batteries> The LiMO produced by the production method of this embodiment can be suitably used as CAM. The CAM of the present embodiment contains LiMO. The CAM may contain LiMO other than that of the present invention as long as the effects of the present invention are not impaired.

[0173] <Lithium secondary battery> The configuration of a lithium secondary battery suitable for the case where LiMO manufactured by the manufacturing method of this embodiment is used as a CAM will be described. Furthermore, a description will be given of a positive electrode for a lithium secondary battery suitable for the case where the LiMO produced by the production method of this embodiment is used as a CAM. Hereinafter, the positive electrode for a lithium secondary battery may be referred to as a positive electrode. Furthermore, a lithium secondary battery suitable for use as a positive electrode will be described.

[0174] An example of a suitable lithium secondary battery when LiMO manufactured by the manufacturing method of this embodiment is used as a CAM has a positive electrode, a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolyte solution disposed between the positive electrode and the negative electrode.

[0175] An example of a lithium secondary battery has a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode.

[0176] 1 is a schematic diagram showing an example of a lithium secondary battery. For example, a cylindrical lithium secondary battery 10 is manufactured as follows.

[0177] First, as shown in FIG. 1 , a pair of strip-shaped separators 1, a strip-shaped positive electrode 2 having a positive electrode lead 21 at one end, and a strip-shaped negative electrode 3 having a negative electrode lead 31 at one end are laminated in the order of separator 1, positive electrode 2, separator 1, and negative electrode 3, and then wound to form an electrode group 4.

[0178] Next, the electrode group 4 and an insulator (not shown) are housed in the battery can 5, the bottom of the can is sealed, the electrode group 4 is impregnated with an electrolyte solution 6, and the electrolyte is disposed between the positive electrode 2 and the negative electrode 3. Furthermore, the upper part of the battery can 5 is sealed with a top insulator 7 and a sealing body 8, whereby a lithium secondary battery 10 can be manufactured.

[0179] The shape of the electrode group 4 can be, for example, a columnar shape such that the cross-sectional shape when the electrode group 4 is cut perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners.

[0180] The shape of a lithium secondary battery having such an electrode group 4 can be any shape defined by IEC60086, which is a standard for batteries defined by the International Electrotechnical Commission (IEC), or JIS C 8500. For example, cylindrical or rectangular shapes can be used.

[0181] Furthermore, the lithium secondary battery is not limited to the above-mentioned wound type configuration, and may be a laminated type configuration in which a laminated structure of a positive electrode, a separator, a negative electrode, and a separator is repeatedly stacked. Examples of the laminated type lithium secondary battery include a so-called coin type battery, a button type battery, and a paper type (or sheet type) battery.

[0182] Each component will be described in order below. (positive electrode) The positive electrode can be produced by first preparing a positive electrode mixture containing CAM, a conductive material, and a binder, and then supporting the positive electrode mixture on a positive electrode current collector.

[0183] (Conductive material) The conductive material of the positive electrode may be a carbon material, such as graphite powder, carbon black (e.g., acetylene black), or a fibrous carbon material.

[0184] The proportion of the conductive material in the positive electrode mixture is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of CAM.

[0185] (binder) The binder of the positive electrode can be a thermoplastic resin. Examples of the thermoplastic resin include polyimide resin, fluororesin, polyolefin resin, and resins described in WO2019 / 098384A1 or US2020 / 0274158A1.

[0186] The polyimide resin is, for example, polyvinylidene fluoride (hereinafter sometimes referred to as PVdF).

[0187] The fluororesin is, for example, polytetrafluoroethylene.

[0188] The polyolefin resin is, for example, polyethylene or polypropylene.

[0189] (Positive electrode current collector) The positive electrode current collector of the positive electrode can be a strip-shaped member made of a metal material such as Al, Ni, or stainless steel.

[0190] As a method for supporting the positive electrode mixture on the positive electrode current collector, there can be mentioned a method in which the positive electrode mixture is made into a paste using an organic solvent, the obtained paste of the positive electrode mixture is applied to at least one side of the positive electrode current collector, dried, and fixed by performing an electrode pressing process.

[0191] When the positive electrode mixture is made into a paste, an example of an organic solvent that can be used is N-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP).

[0192] Examples of methods for applying the positive electrode mixture paste to the positive electrode current collector include slit die coating, screen coating, curtain coating, knife coating, gravure coating, and electrostatic spraying.

[0193] The positive electrode can be produced by the above-mentioned methods.

[0194] (Negative electrode) The negative electrode of the lithium secondary battery may be capable of doping and dedoping lithium ions at a lower potential than the positive electrode, for example, an electrode in which a negative electrode mixture containing a negative electrode active material is supported on a negative electrode current collector, and an electrode made of a negative electrode active material can be given.

[0195] (Negative electrode active material) Examples of the negative electrode active material contained in the negative electrode include carbon materials, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals, and alloys that can be doped and dedoped with lithium ions at a lower potential than the positive electrode.

[0196] Examples of carbon materials that can be used as the negative electrode active material include graphite such as natural graphite and artificial graphite, cokes, carbon black, carbon fiber, and fired organic polymer compounds.

[0197] The oxides that can be used as the negative electrode active material are SiO 2 , SiO, etc. x (where x is a positive real number) 2 , SnO etc. x (where x is a positive real number); Li 4 Ti 5 O 12 and metal composite oxides containing lithium and titanium, such as:

[0198] The negative electrode mixture may contain a binder. Examples of the binder 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.

[0199] Examples of electrodes made of anode active materials include electrodes made of metals that can be used as anode active materials, such as lithium metal, silicon metal, and tin metal. Materials that can be used as the negative electrode active material may be materials described in WO2019 / 098384A1 or US2020 / 0274158A1.

[0200] These metals and alloys are mainly used alone as electrodes after being processed into, for example, a foil.

[0201] Among the above negative electrode active materials, carbon materials mainly composed of graphite, such as natural graphite and artificial graphite, are preferably used. This is because the potential of the negative electrode hardly changes 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 when repeatedly charged and discharged is high (good cycle characteristics). The shape of the carbon material may be, for example, a flake like natural graphite, a sphere like mesocarbon microbeads, a fiber like graphitized carbon fiber, or an aggregate of fine powder.

[0202] (Negative electrode current collector) The negative electrode current collector of the negative electrode can be a strip-shaped member made of a metal material such as Cu, Ni, or stainless steel.

[0203] Methods for supporting the negative electrode mixture on such a negative electrode current collector include, as in the case of the positive electrode, a method using pressure molding, a method in which a paste is made using a solvent or the like, which is then applied to the negative electrode current collector, dried, and then pressed to bond the mixture to a negative electrode current collector.

[0204] (Separator) The separator of the lithium secondary battery may be, for example, a material having a form such as a porous film, a nonwoven fabric, or a woven fabric, made of a material such as a polyolefin resin, such as polyethylene or polypropylene, a fluororesin, or a nitrogen-containing aromatic polymer. The separator may be formed by using two or more of these materials, or may be formed by laminating these materials. The separator described in JP-A-2000-030686 or US20090111025A1 may also be used.

[0205] (electrolyte) The electrolyte solution in the lithium secondary battery contains an electrolyte and an organic solvent.

[0206] The electrolyte contained in the electrolyte solution is LiClO 4 , LiPF 6 , LiBF 4 , etc., and a mixture of two or more of these may be used.

[0207] The organic solvent contained in the electrolytic solution may be, for example, a carbonate such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate.

[0208] As the organic solvent, it is preferable to use a mixture of two or more of these. Among them, a mixed solvent containing a carbonate is preferable, and a mixed solvent of a cyclic carbonate and an acyclic carbonate and a mixed solvent of a cyclic carbonate and an ether are more preferable.

[0209] In addition, LiPF is used as the electrolyte because it enhances the safety of the resulting lithium secondary battery. 6 It is preferable to use an electrolyte solution containing a fluorine-containing lithium salt such as those described above and an organic solvent having a fluorine substituent. The electrolyte and organic solvent contained in the electrolytic solution may be the electrolyte and organic solvent described in WO2019 / 098384A1 or US2020 / 0274158A1.

[0210] <All-solid-state lithium secondary battery> Next, while explaining the configuration of the all-solid-state lithium secondary battery, a positive electrode using LiMO manufactured by the manufacturing method of this embodiment as the CAM of the all-solid-state lithium secondary battery and an all-solid-state lithium secondary battery having this positive electrode will be described.

[0211] FIG. 2 is a schematic diagram showing an example of an all-solid-state lithium secondary battery. The all-solid-state lithium secondary battery 1000 shown in FIG. 2 has a laminate 100 having a positive electrode 110, a negative electrode 120, and a solid electrolyte layer 130, and an exterior body 200 that houses the laminate 100. The all-solid-state lithium secondary battery 1000 may have a bipolar structure in which a CAM and a negative electrode active material are arranged on both sides of a current collector. A specific example of the bipolar structure is the structure described in JP-A-2004-95400. The materials constituting each member will be described later.

[0212] The laminate 100 may have an external terminal 113 connected to the positive electrode current collector 112 and an external terminal 123 connected to the negative electrode current collector 122. In addition, the all-solid-state lithium secondary battery 1000 may have a separator between the positive electrode 110 and the negative electrode 120.

[0213] The all-solid-state lithium secondary battery 1000 further includes an insulator (not shown) that insulates the laminate 100 from the exterior body 200 , and a sealing body (not shown) that seals the opening 200 a of the exterior body 200 .

[0214] A container molded from a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel can be used as the exterior body 200. Also, a container formed into a bag shape from a laminate film having at least one surface treated to be corrosion-resistant can be used as the exterior body 200.

[0215] Examples of the shape of the all-solid-state lithium secondary battery 1000 include a coin type, a button type, a paper type (or a sheet type), a cylindrical type, a square type, and a laminate type (pouch type).

[0216] The all-solid-state lithium secondary battery 1000 is illustrated as having one laminate 100 as an example, but the present embodiment is not limited to this. The all-solid-state lithium secondary battery 1000 may have a configuration in which the laminate 100 is used as a unit cell, and a plurality of unit cells (laminated bodies 100) are sealed inside an exterior body 200.

[0217] Each component will be described in order below.

[0218] (positive electrode) The positive electrode 110 includes a positive electrode active material layer 111 and a positive electrode current collector 112 .

[0219] The positive electrode active material layer 111 contains the above-mentioned CAM and solid electrolyte. The positive electrode active material layer 111 may also contain a conductive material and a binder.

[0220] (solid electrolyte) A solid electrolyte having lithium ion conductivity and used in a known all-solid-state lithium secondary battery can be used as the solid electrolyte contained in the positive electrode active material layer 111. Examples of such a solid electrolyte include inorganic electrolytes and organic electrolytes.

[0221] Examples of the inorganic electrolyte include oxide-based solid electrolytes, sulfide-based solid electrolytes, and hydride-based solid electrolytes.

[0222] Examples of the organic electrolyte include polymer-based solid electrolytes.

[0223] Examples of each electrolyte include the compounds described in WO2020 / 208872A1, US2016 / 0233510A1, US2012 / 0251871A1, and US2018 / 0159169A1. For example, the following compounds are included.

[0224] (Oxide-based solid electrolyte) Examples of the oxide-based solid electrolyte include perovskite-type oxides, NASICON-type oxides, LISICON-type oxides, and garnet-type oxides. Specific examples of each oxide include the compounds described in WO2020 / 208872A1, US2016 / 0233510A1, and US2020 / 0259213A1. For example, the following compounds are included.

[0225] Examples of the perovskite-type oxide include Li a La 1-a TiO 3 (0 < a < 1) and other Li-La-Ti-based oxides, Li b La 1-b TaO 3 (0 < b < 1) and other Li-La-Ta-based oxides, and Li c La 1-c N b O 3 (0 < c < 1) and other Li-La-Nb-based oxides.

[0226] Examples of the NASICON-type oxide include Li 1+d Al d Ti 2-d (PO 4 ) 3 (0 ≤ d ≤ 1) and the like. The NASICON-type oxide refers to Li m M 1n M 2o P p O q (In the formula, M1 is at least one element selected from the group consisting of B, Al, Ga, In, C, Si, Ge, Sn, Sb, and Se. M2 is at least one element selected from the group consisting of Ti, Zr, Ge, In, Ga, Sn, and Al. m, n, o, p, and q are any positive numbers.)

[0227] LISICON-type oxides include Li 4 M 3 O 4 -Li 3 M 4 O 4 (M3 is at least one element selected from the group consisting of Si, Ge, and Ti. M4 is at least one element selected from the group consisting of P, As, and V).

[0228] Garnet-type oxides include Li 7 La 3 Zr 2 O 12 (LLZ) and other Li-La-Zr oxides.

[0229] The oxide-based solid electrolyte may be a crystalline material or an amorphous material.

[0230] (Sulfide solid electrolyte) As a sulfide-based solid electrolyte, Li 2 SP 2 S 5 based compounds, Li 2 S-SiS 2 based compounds, Li 2 S-GeS 2 based compounds, Li 2 S.B. 2 S 3 based compounds, LiI-Si 2 SP 2 S 5 system compound, LiI-Li 2 SP 2 O 5 system compound, LiI-Li 3 PO 4 -P 2 S 5 Compounds and Li 10 GeP 2 S 12 Some examples include:

[0231] In this specification, the term "sulfide-based solid electrolyte" refers to the "Li-based compound" described before "sulfide-based compound". 2 S" "P 2 S 5 It is used as a general term for solid electrolytes that mainly contain raw materials such as Li. 2 SP 2 S 5 Li 2 S and P 2 S 5 Solid electrolytes mainly containing Li and other materials. 2 SP 2 S 5 Li contained in the compounds 2 The ratio of S is, for example, Li 2 SP 2 S 5 It is 50 to 90 mass% of the total Li-based compound. 2 SP 2 S 5 P contained in the compound 2 S 5 The ratio of Li 2 SP 2 S 5 The content of the Li-based compound is 10 to 50 mass %. 2 SP 2 S 5 The ratio of other raw materials contained in the system compound is, for example, Li 2 SP 2 S 5 The content of the Li-based compound is 0 to 30 mass%. 2 SP 2 S 5 Li 2 S and P 2 S 5 Also included are solid electrolytes having different mixture ratios of

[0232] Li 2 SP 2 S 5 Li 2 SP 2 S 5 , Li 2 SP 2 S 5 - LiI, Li 2 SP 2 S 5 -LiCl, Li 2 SP 2 S 5 -LiBr, Li 2 SP 2 S 5 -LiI-LiBr, Li 2 SP 2 S 5 -Li 2 O, Li 2 SP 2 S 5 -Li 2 O-LiI and Li 2 SP 2 S 5 -Z m S n (m and n are positive numbers. Z is Ge, Zn or Ga.)

[0233] Li 2 S-SiS 2 Li 2 S-SiS 2 , Li 2 S-SiS 2 - LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B 2 S 3 - LiI, Li 2 S-SiS 2 -P 2 S 5 - LiI, Li 2 S-SiS 2 -P 2 S 5 -LiCl, Li 2 S-SiS 2 -Li 3 PO 4 , Li 2 S-SiS 2 -Li 2 SO 4 and Li 2 S-SiS 2 -Li x MO y (x and y are positive numbers. M is P, Si, Ge, B, Al, Ga, or In.)

[0234] Li 2 S-GeS 2 Li 2 S-GeS 2 and Li 2 S-GeS 2 -P 2 S 5 Some examples include:

[0235] The sulfide-based solid electrolyte may be a crystalline material or an amorphous material.

[0236] (Hydride-based solid electrolyte) LiBH is a hydride-based solid electrolyte material. 4 , LiBH 4 -3KI, LiBH 4 -PI 2 , LiBH 4 -P 2 S 5 , LiBH 4 -LiNH 2 , 3LiBH 4 - LiI, LiNH 2 , Li 2 AlH 6 , Li(NH 2 ) 2 I, Li 2 NH, LiGd(BH 4 ) 3 Cl, Li 2 (BH 4 )(NH 2 ), Li 3 (NH 2 )I and Li 4 (BH 4 )(NH 2 ) 3 Some examples include:

[0237] (Polymer-based solid electrolyte) Examples of the polymer solid electrolyte include organic polymer electrolytes such as polyethylene oxide polymer compounds and polymer compounds containing at least one selected from the group consisting of polyorganosiloxane chains and polyoxyalkylene chains. Also, so-called gel-type electrolytes in which a non-aqueous electrolyte solution is held in a polymer compound can be used.

[0238] Two or more solid electrolytes can be used in combination as long as the effects of the invention are not impaired.

[0239] (Conductive materials and binders) The conductive material of the positive electrode active material layer 111 may be the material described in the above (Conductive material). The proportion of the conductive material in the positive electrode mixture may be the same as that described in the above (Conductive material). The binder of the positive electrode may be the material described in the above (Binder).

[0240] (Positive electrode current collector) For the positive electrode current collector 112 of the positive electrode 110, the materials explained in the (positive electrode current collector) explanation of FIG. 1 can be used.

[0241] An example of a method for supporting the positive electrode active material layer 111 on the positive electrode current collector 112 is a method for pressure molding the CAM layer 111 on the positive electrode current collector 112. Cold pressing or hot pressing can be used for pressure molding.

[0242] Alternatively, a mixture of the CAM, the solid electrolyte, the conductive material, and the binder may be made into a paste using an organic solvent to prepare a positive electrode mixture, and the obtained positive electrode mixture may be applied onto at least one surface of the positive electrode current collector 112, dried, and pressed to adhere, thereby causing the positive electrode active material layer 111 to be supported on the positive electrode current collector 112.

[0243] Alternatively, a mixture of the CAM, the solid electrolyte, and the conductive material may be made into a paste using an organic solvent to prepare a positive electrode mixture, and the obtained positive electrode mixture may be applied onto at least one surface of the positive electrode current collector 112, dried, and sintered to cause the positive electrode active material layer 111 to be supported on the positive electrode current collector 112.

[0244] As the organic solvent that can be used for the positive electrode mixture, the same organic solvent that can be used when making the positive electrode mixture into a paste as described above in (positive electrode current collector) can be used.

[0245] The method for applying the positive electrode mixture to the positive electrode current collector 112 includes the methods described above in (Positive electrode current collector).

[0246] The positive electrode 110 can be manufactured by the above-mentioned method. Specific combinations of materials used for the positive electrode 110 include combinations of the above-mentioned CAM with the solid electrolyte, binder, and conductive material shown in Tables 1 to 3.

[0247] [Table 1]

[0248] [Table 2]

[0249] [Table 3]

[0250] (Negative electrode) 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. The negative electrode active material layer 121 may also contain a solid electrolyte and a conductive material. The negative electrode active material, the negative electrode current collector, the solid electrolyte, the conductive material, and the binder may be those described above. is preferably used.

[0251] Methods for supporting the negative electrode active material layer 121 on the negative electrode current collector 122 include, as in the case of the positive electrode 110, a method using pressure molding, a method in which a paste-like negative electrode mixture containing a negative electrode active material is applied onto the negative electrode current collector 122, dried, and then pressed and bonded, and a method in which a paste-like negative electrode mixture containing a negative electrode active material is applied onto the negative electrode current collector 122, dried, and then sintered.

[0252] (Solid electrolyte layer) The solid electrolyte layer 130 includes the solid electrolyte described above.

[0253] 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 above-mentioned positive electrode 110 by a sputtering method.

[0254] The solid electrolyte layer 130 can be formed by applying a paste-like mixture containing a solid electrolyte to the surface of the positive electrode active material layer 111 of the above-mentioned positive electrode 110, and drying the mixture. After drying, the mixture may be press-molded and further pressed by cold isostatic pressing (CIP) to form the solid electrolyte layer 130.

[0255] The laminate 100 can be produced by laminating the negative electrode 120 on the solid electrolyte layer 130 provided on the positive electrode 110 as described above, using a known method, in such a manner that the negative electrode active material layer 121 is in contact with the surface of the solid electrolyte layer 130.

[0256] The LiMO of the present embodiment has a predetermined crystal structure and crystal shape, and thus can improve the rate characteristics and cycle characteristics of a lithium secondary battery. The reason for this is that the cycle retention rate is unlikely to decrease because the LiMO has a predetermined crystal structure and is therefore likely to be able to maintain the crystal structure even when charging and discharging are repeated. In addition, the LiMO has a predetermined crystal shape, and thus the Li desorption and insertion surfaces are large, and therefore the rate characteristics are unlikely to decrease. EXAMPLES

[0257] Next, the present invention will be described in more detail with reference to examples.

[0258] <Composition analysis> The composition analysis of LiMO was carried out by the method described in the above <Composition analysis>.

[0259] <Method for measuring the average particle diameter of single particles> The average particle diameter of single particles of LiMO was measured by the method described in the above <Method for measuring the average particle diameter of single particles>.

[0260] <Method for measuring the average particle diameter of secondary particles> The average particle diameter of secondary particles of LiMO was measured by the same method as the method described in the above <Method for measuring the average particle diameter of single particles>.

[0261] <Method for measuring the content rate of single particles based on the number> The content rate of single particles of LiMO based on the number was measured by the method described in the above <Method for measuring the content rate of single particles based on the number>.

[0262] <Method for confirming the crystal structure> The crystal structure of LiMO was confirmed by the method described in the above <Method for confirming the crystal structure>.

[0263] <Crystallite size L A and L B measurement method> The crystallite size L A and L B of LiMO was measured by the method described in the above <Crystallite size L A and L B measurement method>. The obtained crystallite sizes L A and L B were used to calculate the ratio L A / L B .

[0264] <Measurement of Me occupancy> The Me occupancy of the Li site in LiMO was measured by the method described in the above <Rietveld analysis method>.

[0265] <Measurement Method of Cumulative Volume Particle Size> The cumulative volume particle sizes of the metal composite hydroxide and LiMO were measured by the method described in the above [Measurement Method of Cumulative Volume Particle Size]. The obtained D of the metal composite hydroxide H10 , D H50 , D H90 From, (D H90 - D H10 ) / D H50 was calculated.

[0266] <Calculation of P1 / D 50 > From the average particle diameter P1 of the single particles obtained by the above method and the 50% cumulative volume particle size D of LiMO 50 , P1 / D 50 was determined.

[0267] <Measurement Method of BET Specific Surface Area> The BET specific surface area of LiMO was determined by the method described in the above [Measurement Method of BET Specific Surface Area].

[0268] <Measurement of Rate Characteristics and Cycle Characteristics of Lithium Secondary Battery> The rate characteristics and cycle characteristics of the lithium secondary battery were measured by the method described in the above [Measurement of Rate Characteristics and Cycle Characteristics].

[0269] <Example 1> [Nucleation Step] Using a device having a reaction tank equipped with a stirrer and an overflow pipe, a concentrating tank connected to the overflow pipe, and a mechanism for circulating from the concentrating tank to the reaction tank, after adding water to the reaction tank, an aqueous sodium hydroxide solution was added and the liquid temperature was maintained at 50 °C.

[0270] An aqueous nickel sulfate solution and an aqueous cobalt sulfate solution were mixed at a ratio such that the atomic ratio of Ni to Co was 0.89:0.11 to prepare a metal raw material mixture solution.

[0271] Next, 3 g of ammonium sulfate crystals as a complexing agent was added to the reaction tank per 1 L of the reaction tank volume, and the concentration of the complexing agent in the reaction tank was adjusted to 3 g / L. Under stirring, the metal raw material mixture and an aqueous solution of ammonium sulfate as a complexing agent were continuously added.

[0272] Aqueous sodium hydroxide solution was added dropwise at appropriate times so that the pH of the solution in the reaction vessel became 11.5 (measurement temperature: 40° C.).

[0273] [Nuclear growth process] Next, an aqueous sodium hydroxide solution was added dropwise at appropriate times so that the pH of the solution in the reaction tank became 11.2 (measurement temperature: 40° C.). After 33 hours had passed since the start of the nucleus growth process, all liquid transfer was stopped and the crystallization reaction was terminated.

[0274] The obtained nickel-cobalt metal composite hydroxide-containing slurry was washed and dehydrated, and then dried at 105°C for 24 hours and sieved to obtain nickel-containing metal composite hydroxide 1. H90 -D H10 ) / D H50 was 1.00.

[0275] Nickel-containing metal composite hydroxide 1 was heated at 650° C. for 5 hours to obtain nickel-containing metal composite oxide 1.

[0276] The nickel-containing metal composite oxide 1, lithium hydroxide powder, and potassium carbonate powder as an inert flux were mixed at a temperature of Li / (Ni+Co)=1.1, K 2 CO 3 / (LiOH+K 2 CO 3 After weighing and mixing in a ratio of K = 0.1 (mol / mol), the mixture was calcined at 790 °C for 10 hours in an oxygen atmosphere (calcination step) to obtain a mixture 1 containing LiMO-1. 2 CO 3 The amount of added is expressed as 10 mol %. The same will be used hereinafter.

[0277] Mixture 1 and pure water (water temperature: 5° C.) were mixed in such a ratio that the ratio of mixture 1 to the total amount of mixture 1 and pure water was 30 mass %, and the resulting slurry was stirred for 10 minutes.

[0278] The slurry was dehydrated, and the obtained solid was rinsed with pure water (liquid temperature: 5°C) of twice the mass of the mixture 1 used to prepare the slurry (rinsing step). The solid was dehydrated again and heat-treated at 760°C for 5 hours in an oxygen atmosphere to obtain LiMO-1.

[0279] (Evaluation of LiMO-1) The composition of LiMO-1 was analyzed and corresponded to the composition formula (I), where x=1.01, y=0.105, z=0, and w=0.

[0280] SEM observation of LiMO-1 confirmed that it contains single particles and secondary particles. Figure 3 shows an SEM image of a single particle of LiMO-1.

[0281] The crystal structure of LiMO-1 is a layered rock-salt type crystal structure. A / L B , Me occupancy rate, BET specific surface area, average particle size of single particles, P1 / D 50 , L B The rate characteristics and cycle characteristics are shown in Table 5.

[0282] <Example 2> The same operation as in Example 1 was carried out except that the calcination step was changed to two steps, 760° C. for 5 hours and 790° C. for 5 hours in an oxygen atmosphere, to obtain LiMO-2.

[0283] (Evaluation of LiMO-2) The composition of LiMO-2 was analyzed and corresponded to the composition formula (I), which was x=0.98, y=0.106, z=0, and w=0.

[0284] SEM observation of LiMO-2 confirmed that it contains single particles and secondary particles. Figure 4 shows an SEM image of a single particle of LiMO-2.

[0285] The crystal structure of LiMO-2 is a layered rock-salt type crystal structure. A / L B , Me occupancy rate, BET specific surface area, average particle size of single particles, P1 / D 50 , L B The rate characteristics and cycle characteristics are shown in Table 5.

[0286] <Example 3> Nickel-containing metal composite hydroxide 2 was obtained in the same manner as in Example 1, except that the metal raw material mixture was supplied in a ratio of Ni:Co:Mn=88.5:9:2.5, the pH in the nucleus generation process was set to 11.3, and the pH in the nucleus growth process was set to 10.9. Nickel-containing metal complex hydroxide 2 (D H90 -D H10 ) / D H50 was 0.95.

[0287] The nickel-containing metal composite hydroxide 2 was heated at 650° C. for 5 hours to obtain a nickel-containing metal composite oxide 2. The same operation as in Example 1 was carried out except that the nickel-containing metal composite oxide 2 was used instead of the nickel-containing metal composite oxide 1, to obtain LiMO-3.

[0288] (Evaluation of LiMO-3) The composition of LiMO-3 was analyzed and corresponded to the composition formula (I), where x=1.03, y=0.089, z=0.026, and w=0.

[0289] As a result of SEM observation of LiMO-3, it was confirmed that LiMO-3 contains single particles and secondary particles. Figure 5 shows an SEM image of a single particle of LiMO-3, and Figure 6 shows an SEM image of LiMO-3 containing secondary particles.

[0290] The crystal structure of LiMO-3 is a layered rock-salt type crystal structure. A / L B , Me occupancy rate, BET specific surface area, average particle size of single particles, P1 / D 50 , L B The rate characteristics and cycle characteristics are shown in Table 5.

[0291] <Example 4> The same procedure as in Example 3 was carried out except that the calcination step was changed to 820° C. for 10 hours, to obtain LiMO-4.

[0292] (Evaluation of LiMO-4) The composition of LiMO-4 was analyzed and corresponded to the composition formula (I), where x=1.01, y=0.089, z=0.025, and w=0.

[0293] SEM observation of LiMO-4 confirmed that it contains single particles and secondary particles. Figure 7 shows an SEM image of a single particle of LiMO-4.

[0294] The crystal structure of LiMO-4 is a layered rock-salt type crystal structure. A / L B , Me occupancy rate, BET specific surface area, average particle size of single particles, P1 / D 50 , L B The rate characteristics and cycle characteristics are shown in Table 5.

[0295] <Comparative Example 1> A mixed raw material liquid was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, an aqueous solution of manganese sulfate, and an aqueous solution of zirconium sulfate in such a ratio that the atomic ratio of Ni, Co, Mn, and Zr was 87.5:8:4:0.5.

[0296] Next, this mixed raw material liquid and an aqueous solution of ammonium sulfate were continuously added to the reaction vessel under stirring. An aqueous solution of sodium hydroxide was added dropwise at appropriate times so that the pH of the solution in the reaction vessel became 11.2 (measured at a liquid temperature of 40°C), and a reaction product was obtained.

[0297] The reaction product was washed, dehydrated using a centrifuge, isolated, and dried at 105° C. to obtain nickel-containing metal composite hydroxide 3. Nickel-containing metal complex hydroxide 3 (D H90 -D H10 ) / D H50 was 1.07.

[0298] The nickel-containing metal composite hydroxide 3 was heated at 650° C. for 5 hours to obtain a nickel-containing metal composite oxide 3.

[0299] The same procedure as in Example 1 was carried out except that nickel-containing metal composite oxide 3 was used instead of nickel-containing metal composite oxide 1, to obtain LiMO-5.

[0300] (LiMO-5 evaluation) The composition of LiMO-5 was analyzed and corresponded to the composition formula (I), where x = 0.99, y = 0.076, z = 0.040, and w = 0.002.

[0301] SEM observation of LiMO-5 confirmed that it contains single particles and secondary particles. Figure 8 shows an SEM image of a single particle of LiMO-5.

[0302] The crystal structure of LiMO-5 is a layered rock-salt type crystal structure. A / L B , Me occupancy rate, BET specific surface area, average particle size of single particles, P1 / D 50 , L B The rate characteristics and cycle characteristics are shown in Table 5.

[0303] <Comparative Example 2> The same operation as in Example 1 was carried out except that the heating temperature of the nickel-containing metal composite hydroxide 1 was changed from 650° C. to 800° C., to obtain LiMO-6.

[0304] (Evaluation of LiMO-6) The composition of LiMO-6 was analyzed and corresponded to the composition formula (I), where x=0.89, y=0.105, z=0, and w=0.

[0305] As a result of SEM observation of LiMO-6, it was confirmed that LiMO-6 contains single particles and secondary particles. Figure 9 shows an SEM image of a single particle of LiMO-6.

[0306] The crystal structure of LiMO-6 is a layered rock-salt type crystal structure. A / L B , Me occupancy rate, BET specific surface area, average particle size of single particles, P1 / D 50 , L B The rate characteristics and cycle characteristics are shown in Table 5.

[0307] <Comparative Example 3> A mixed raw material liquid was prepared by mixing an aqueous nickel sulfate solution, an aqueous cobalt sulfate solution, and manganese sulfate in such a ratio that the atomic ratio of Ni, Co, and Mn was 91:5:4.

[0308] Next, this mixed raw material liquid and an aqueous solution of ammonium sulfate were continuously added to the reaction vessel under stirring. An aqueous solution of sodium hydroxide was added dropwise at appropriate times so that the pH of the solution in the reaction vessel became 11.2 (measured at a liquid temperature of 40°C), and a reaction product was obtained. The reaction product was washed, dehydrated using a centrifuge, isolated, and dried at 105° C. to obtain nickel-containing metal composite hydroxide 4.

[0309] Using an elbow jet classifier (Matsubo EJ-L-3 type), the nickel-containing metal composite hydroxide 4 was classified into small particle size classification particles, medium particle size classification particles, and large particle size classification particles (weight % ratio) of 20:50:30. The medium-sized particles of nickel-containing metal composite hydroxide 4 (D H90 -D H10 ) / D H50 was 0.93.

[0310] The medium particle-classified particles were heated at 650° C. for 5 hours to obtain nickel-containing metal composite oxide 4.

[0311] LiMO-7 was obtained by the same procedure as in Example 1, except that nickel-containing metal composite oxide 4, lithium hydroxide powder, and potassium hydroxide powder were weighed and mixed in a ratio of Li / (Ni+Co+Mn)=1.1 and KOH / (LiOH+KOH)=0.1 (mol / mol).

[0312] (LiMO-7 evaluation) The composition of LiMO-7 was analyzed and corresponded to the composition formula (I), where x=1.02, y=0.049, z=0.033, and w=0.

[0313] SEM observation of LiMO-7 confirmed that LiMO-7 contains single particles and secondary particles. Figure 10 shows an SEM image of a single particle of LiMO-7.

[0314] The crystal structure of LiMO-7 is a layered rock-salt type crystal structure. A / L B , Me occupancy rate, BET specific surface area, average particle size of single particles, P1 / D 50 , L B The rate characteristics and cycle characteristics are shown in Table 5.

[0315] <Comparative Example 4> Nickel-containing metal composite hydroxide 5 was obtained in the same manner as in Example 1, except that the metal raw material mixture was supplied in a ratio of Ni:Co:Mn=88:8:4, the pH was set to 11.6 in the nucleus generation step, and the pH was set to 11.0 in the nucleus growth step. H90 -D H10 ) / D H50 The nickel-containing metal composite hydroxide 5 was heated at 650° C. for 5 hours to obtain nickel-containing metal composite oxide 5.

[0316] The nickel-containing metal composite oxide 5, lithium hydroxide powder, and potassium carbonate powder were mixed at a temperature of Li / (Ni+Co+Mn)=1.1, K 2 CO 3 / (LiOH+K 2 CO 3 The same operation as in Example 1 was carried out except that the components were weighed and mixed in a ratio such that LiMO-8 was obtained.

[0317] (LiMO-8 evaluation) The composition of LiMO-8 was analyzed and corresponded to the composition formula (I), where x=1.06, y=0.050, z=0.043, and w=0.

[0318] As a result of SEM observation of LiMO-8, it was confirmed that LiMO-8 does not contain single particles, but is composed only of secondary particles. Figure 11 shows an SEM image of secondary particles of LiMO-8.

[0319] The crystal structure of LiMO-8 is a layered rock-salt type crystal structure. A / L B , Me occupancy rate, BET specific surface area, average particle size of single particles, P1 / D 50 , L B The rate characteristics and cycle characteristics are shown in Table 5.

[0320] Table 4 below shows the Ni / Co / Mn ratio and the (D H90 -D H10 ) / D H50 , the oxidation temperature and the inert flux are described.

[0321] [Table 4]

[0322] [Table 5]

[0323] As shown in the above results, L A / L B In Examples 1 to 4, in which the Me occupancy rate was within the range of the present invention, both the rate characteristics and cycle characteristics were excellent. [Explanation of symbols]

[0324] 1: separator, 3: negative electrode, 4: electrode group, 5: battery can, 6: electrolyte, 7: top insulator, 8: sealing body, 10: lithium secondary battery, 21: positive electrode lead, 100: laminate, 110: positive electrode, 111: positive electrode active material layer, 112: positive electrode current collector, 113: external terminal, 120: negative electrode, 121: negative electrode active material layer, 122: negative electrode current collector, 123: external terminal, 130: solid electrolyte layer, 200: exterior body, 200a: opening, 1000: all-solid-state lithium secondary battery< / limo>

Claims

1. secondary particles which are aggregates of primary particles; A lithium metal composite oxide comprising: a single particle that exists independently of the secondary particle, It has a layered rock salt structure. Represented by the following composition formula (I): A lithium metal composite oxide that satisfies the following (1) and (2): Li ｘ Ni １－ｙ－ｚ－ｗ Co ｙ Mn ｚ X1 ｗ O ２ ・・・(I) (wherein 0.9≦x≦1.2, 0≦y≦0.4, 0≦z≦0.4, 0≦w≦0.1, y+z+w≦1, and X1 represents one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.) (1):1.2≦L Ａ / L Ｂ <1.60 (L Ａ is the crystallite size determined from the diffraction peak 1 in the range of 2θ=18.8±1° in the powder X-ray diffraction obtained using CuKα radiation, and L Ｂ is the crystallite diameter determined from the diffraction peak 2 within the range of 2θ = 38.3 ± 1 °.) (2): The Me occupancy rate at the Li site of the layered rock salt structure, which is determined by analyzing the diffraction peaks by Rietveld analysis, is 2.5% or less. The Me is Ni, Co, Mn or the element X1.

2. The lithium metal composite oxide according to claim 1 , wherein z satisfies 0≦z≦0.

2.

3. BET specific surface area is 1.0 m ２ The lithium metal composite oxide according to claim 1 or 2, wherein the Li-ion concentration is 0.1 to 0.5% by mass.

4. The lithium metal composite oxide according to any one of claims 1 to 3, wherein the average particle size of the single particles is 2.0 µm or more and 10 µm or less.

5. The lithium metal composite oxide according to any one of claims 1 to 4, which satisfies the following (3): (3):0.30≦P1 / D ５０ (P1 is the average particle diameter (μm) of the single particle. D ５０ is the 50% cumulative volume particle size (μm) of the lithium metal composite oxide obtained from a volume-based cumulative particle size distribution curve measured by a laser diffraction scattering method.

6. Said L Ｂ The lithium metal composite oxide according to any one of claims 1 to 5, wherein the surface roughness is 1000 Å or less.

7. A positive electrode active material for a lithium secondary battery, comprising the lithium metal composite oxide according to any one of claims 1 to 6.

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

9. A lithium secondary battery comprising the positive electrode for lithium secondary batteries according to claim 8.

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