Metal composite compound and method for producing positive electrode active material for lithium secondary battery

Abstract

To provide a metal composite compound that enables production of a lithium secondary battery with high initial charge and discharge efficiency.SOLUTION: A metal composite compound comprising at least Ni, wherein in a differential pore volume distribution determined by the Barrett-Joyner-Halenda method from a nitrogen gas adsorption isotherm, A / B is 0.05 or more and less than 1.5 where A denotes an integrated area of a region having a pore diameter of 1 nm or more and 50 nm or less and B denotes an integrated area of a region having a pore diameter of more than 50 nm and 200 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] The positive electrode active material contained in the positive electrode of a lithium secondary battery can be obtained, for example, by mixing a lithium compound and a metal composite compound containing a metal element other than Li and baking the mixture.

[0003] As a technique for improving the battery performance of lithium secondary batteries, attempts have been made to control the physical properties of metal composite compounds that serve as raw materials for the positive electrode active material.

[0004] For example, Patent Document 1 discloses a method for producing a high-density hydroxide precursor as a metal composite compound and using the precursor to produce a lithium transition metal composite oxide. Patent Document 1 also discloses that the positive electrode active material produced using such a hydroxide precursor has a large discharge capacity (energy density) per volume. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP-B-7004959 Summary of the Invention [Problem to be solved by the invention]

[0006] As the application fields of lithium secondary batteries expand, further improvements in initial charge / discharge efficiency are required.

[0007] An object of the present invention is to provide a metal composite compound that can be used to produce a lithium secondary battery with high initial charge-discharge efficiency, and a method for producing a positive electrode active material for a lithium secondary battery using the same. [Means for solving the problem]

[0008] The present invention encompasses the following [1] to [8]. [1] A metal composite compound containing at least Ni, wherein, in a differential pore volume distribution obtained from a nitrogen gas adsorption isotherm by the Barrett-Joyner-Halenda method, when the integrated area of ​​a region having a pore diameter of 1 nm or more and 50 nm or less is defined as A and the integrated area of ​​a region having a pore diameter of more than 50 nm and 200 nm or less is defined as B, the ratio A / B is 0.05 or more and less than 1.5. [2] The metal complex compound according to [1], wherein the differential pore volume distribution has two or more maximum points in a region where the pore diameter is 20 nm or more and 150 nm or less. [3] The metal complex compound according to [1] or [2], wherein the differential pore volume distribution has one or more maximum points in the pore diameter region of 20 nm or more and 50 nm or less, and one or more maximum points in the region of more than 50 nm and 200 nm or less. [4] Among the maximum points present in the differential pore volume distribution, the differential pore volume value X of the first maximum point having the largest differential pore volume is 0.15 cm 3 The metal complex compound according to any one of [1] to [3], wherein the metal complex compound has a molecular weight of 1 / g or less. [5] The metal composite compound according to any one of [1] to [4], wherein, among the local maximum points present in the differential pore volume distribution, a differential pore volume value X of a first local maximum point having the largest differential pore volume, and a differential pore volume value Y of a second local maximum point having the second largest differential pore volume after the first local maximum point, X / Y is 7 or less. [6] The metal complex compound according to any one of [1] to [5], which is represented by the following formula (I): Ni (1-x-y) M1 x M2 y O z (OH) 2-α (I) (In formula (I), 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 0.2, 0 ≦ x + y < 1, 0 ≦ z ≦ 3, -0.5 ≦ α ≦ 2, and α - z < 2, M1 is one or more elements selected from the group consisting of Co, Mn, and Al, and M2 is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.) [7] The metal composite compound according to [6], wherein the formula (I) satisfies 0 < x + y ≦ 0.6. [8] A method for producing a cathode active material for a lithium secondary battery, comprising a step of firing a mixture of the metal composite compound according to any one of [1] to [7] and a lithium compound. [Advantages of the Invention]

[0009] According to the present invention, a metal composite compound capable of producing a lithium secondary battery with high initial charge-discharge efficiency can be obtained. Furthermore, a method for producing a cathode active material for a lithium secondary battery using such a metal composite compound can be provided. [Brief Description of the Drawings]

[0010] [Figure 1] It is a schematic diagram showing an example of a lithium secondary battery. [Figure 2] It is a schematic diagram showing an example of an all-solid-state lithium secondary battery. [Embodiments for Carrying Out the Invention]

[0011] In the present specification, the metal composite compound (Metal Composite Compound) is hereinafter referred to as "MCC", and the cathode active material for a lithium secondary battery (Cathode Active Material for lithium secondary batteries) is hereinafter referred to as "CAM".

[0012] "Ni" does not refer to nickel metal, but refers to nickel atoms. Similarly, "Co", "Li", etc. refer to cobalt atoms, lithium atoms, etc., respectively. The lithium secondary battery refers to a lithium-ion secondary battery.

[0013] When a numerical range is stated as, for example, "1-10 μm" or "1 to 10 μm," it means a range from 1 μm to 10 μm, including the lower limit of 1 μm and the upper limit of 10 μm.

[0014] [Measurement of initial charge / discharge efficiency] A lithium secondary battery is produced by the following method, and the initial charge / discharge efficiency is measured.

[0015] 1. Fabrication of Lithium Secondary Batteries (CAM creation) MCC and lithium hydroxide monohydrate powder are weighed and mixed in a ratio such that the molar ratio of Li contained in the lithium hydroxide monohydrate powder to the total amount of elements other than oxygen atoms contained in MCC (e.g., Ni, element M1 or element M2 described below) is 1.05, to obtain a mixture. The resulting mixture is calcined in an oxygen atmosphere at 650°C for 5 hours, and then calcined in an oxygen atmosphere at 750°C for 5 hours to obtain CAM.

[0016] (Production of positive electrodes for lithium secondary batteries) The resulting CAM, a conductive material (acetylene black), and a binder (PVdF) were mixed in a mass ratio of CAM:conductive material:binder = 92:5:3 and kneaded to prepare a paste-like positive electrode mixture. N-methyl-2-pyrrolidone was used as the organic solvent when preparing the positive electrode mixture.

[0017] The resulting positive electrode mixture is applied to a 40 μm thick Al foil as a current collector and dried in a vacuum at 150°C for 8 hours to obtain a positive electrode for a lithium secondary battery. The electrode area of ​​this positive electrode for a lithium secondary battery is 1.65 cm2. 2 Let's say.

[0018] (Fabrication of lithium secondary batteries) The following operations are carried out in a glove box under an argon atmosphere. The lithium secondary battery positive electrode prepared in (Preparation of a lithium secondary battery positive electrode) is placed on the bottom cover of a coin-type battery R2032 part (for example, manufactured by Hosen Co., Ltd.) with the aluminum foil side facing down, and a separator (porous polyethylene film) is placed on top of that. 300 μL of electrolyte is poured into this. The electrolyte is a mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 30:35:35, with LiPF6 dissolved at a concentration of 1.0 mol / L.

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

[0020] 2. Charge / discharge test Using the lithium secondary battery produced by the above method, tests are carried out as described in the following (Measurement Method).

[0021] (Measurement method) First, the lithium secondary battery fabricated as described above is left standing at room temperature for 12 hours to allow the separator and the positive electrode mixture layer to be sufficiently impregnated with the electrolyte. Next, at a test temperature of 25°C, the current setting for both charging and discharging was 0.2 CA, and constant current / constant voltage charging and constant current discharging were performed, respectively. The maximum charging voltage was 4.3 V, and the minimum discharging voltage was 2.5 V. The charging capacity was measured, and the obtained value was designated as the "initial charging capacity" (mAh / g). The discharging capacity was then measured, and the obtained value was designated as the "initial discharging capacity" (mAh / g).

[0022] Then, the initial charge / discharge efficiency is calculated using the obtained initial discharge capacity value and initial charge capacity value according to the following formula (a). Initial charge / discharge efficiency (%) = Initial discharge capacity (mAh / g) / Initial charge capacity (mAh / g) × 100 (a)

[0023] <Metal composite compounds> MCC contains at least Ni. One example of MCC is a hexagonal compound with a layered structure. MCC may be a metal composite oxide, a metal composite hydroxide, or a mixture thereof. The metal composite hydroxide may also include a partially oxidized compound. One aspect of MCC is secondary particles that are aggregates of primary particles.

[0024] MCC may further contain elements M1 and M2. Element M1 is one or more elements selected from the group consisting of Co, Mn, and Al, and element M2 is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.

[0025] [How to obtain differential pore volume distribution] The "differential pore volume distribution" can be determined by analyzing the nitrogen adsorption isotherm obtained by measuring the MCC powder at liquid nitrogen temperature using the Barrett-Joyner-Halenda (BJH) method. The nitrogen adsorption isotherm can be measured using an automatic specific surface area / pore size distribution analyzer (Tristar II 3020, manufactured by Shimadzu Corporation), for example.

[0026] First, 1 g of MCC powder is degassed with nitrogen at 105°C for 30 minutes using a degassing apparatus (VacPrep061, Shimadzu Corporation). After the treatment, the amount of nitrogen adsorbed by the MCC powder at liquid nitrogen temperature (77 K) is measured using the above-mentioned measuring apparatus, and a nitrogen adsorption isotherm is created.

[0027] The nitrogen adsorption isotherm is plotted as follows: the horizontal axis is the ratio of the adsorption equilibrium pressure to the saturated vapor pressure (relative pressure (ρ / ρ0)), and the vertical axis is the adsorption amount of gaseous nitrogen (cm) at standard temperature and pressure (STP). 3 The values ​​are plotted as (STP) / g.

[0028] The obtained nitrogen adsorption isotherm is analyzed by the BJH method to determine the differential pore volume distribution in the region of pore diameters of 200 nm or less. The differential pore volume distribution is plotted with the pore diameter (nm) on the horizontal axis and the differential pore volume (cm) on the vertical axis. 3 / g).

[0029] In the differential pore volume distribution obtained by the above method, the integrated area of ​​the region where the pore diameter is 1-50 nm is defined as A, and the integrated area of ​​the region where the pore diameter is more than 50 nm and is 200 nm or less is defined as B.

[0030] The A / B ratio of the MCC is 0.05 or more and less than 1.5, preferably 1.3 or less, more preferably 1.2 or less, and even more preferably 1.0 or less. Furthermore, A / B is preferably 0.07 or more, and more preferably 0.10 or more. The above lower limit and upper limit of A / B can be combined arbitrarily. A / B is preferably 0.07 to 1.3, more preferably 0.10 to 1.2, and even more preferably 0.10 to 1.0.

[0031] MCC with an A / B ratio within the above range has a non-uniform pore size distribution. When mixed with a lithium compound, this MCC allows the lithium compound to easily penetrate the interior of the particles. When the mixture of MCC and lithium compound is sintered, the reaction between the MCC and the lithium compound is likely to occur evenly on the surface and interior of the MCC. As a result, CAM is obtained in which Li is uniformly distributed from the center to near the surface. CAM with Li uniformly distributed throughout the particles tends to have a large capacity, making it possible to produce lithium secondary batteries with high initial charge / discharge efficiency.

[0032] A is preferably 0.3 or more, more preferably 0.4 or more. A is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. The above lower and upper limits of A can be arbitrarily combined. A is preferably 0.3-5.0, more preferably 0.4-4.0, and even more preferably 0.4-3.0. When A is in the above range, the initial charge-discharge efficiency can be further increased.

[0033] B is preferably 0.5 or more, more preferably 1.0 or more. B is preferably 15.0 or less, more preferably 12.0 or less. The above lower and upper limits of B can be combined arbitrarily. B is preferably 0.5 to 15.0, more preferably 1.0 to 12.0. When B is in the above range, the initial charge / discharge efficiency can be further increased.

[0034] The differential pore volume distribution of an MCC in which A / B satisfies the above range has a broad peak.

[0035] The MCC preferably has two or more maximum points in the differential pore volume distribution in the pore diameter range of 20-150 nm. Here, the maximum points are the points where the differential coefficient changes from positive to negative in the distribution curve of the differential pore volume distribution. The distribution curve of the differential pore volume distribution used has 30 or more differential pore volume plots in the pore diameter range of 200 nm or less.

[0036] The number of maximum points in the pore diameter range of 20 to 150 nm is more preferably 3 or more, and the number of maximum points in the pore diameter range of 20 to 150 nm is preferably 5 or less, more preferably 4 or less. The maximum point in the pore diameter range of 20 to 150 nm is preferably 2 to 5 points, more preferably 3 to 4 points.

[0037] Under the condition that A / B satisfies the above range, MCC with a maximum point in the pore diameter region of 20-150 nm satisfies the above range means that there is variation in pore diameter and the pore distribution is more non-uniform. Such MCC allows lithium compounds to easily penetrate into the interior of the particles, and as mentioned above, it is possible to produce lithium secondary batteries with higher initial charge / discharge efficiency.

[0038] In the differential pore volume distribution, the MCC preferably has one or more maximum points in the pore diameter range of 20 to 50 nm, and one or more maximum points in the range of more than 50 nm and not more than 200 nm. The maximum point in the pore diameter range of 20-50 nm is more preferably point 1-3, and even more preferably point 1-2. The maximum point in the region of pore diameters exceeding 50 nm and not exceeding 200 nm is more preferably point 1-4, and even more preferably point 2-3.

[0039] When A / B satisfies the above range, MCCs with pore diameters in the 20-50 nm region and the maximum points in the region exceeding 50 nm and 200 nm satisfy the above ranges have pore sizes ranging from fine to large, making it easier for lithium compounds to penetrate into the particles. As a result, lithium secondary batteries with higher initial charge / discharge efficiency can be manufactured, as explained above.

[0040] Among the maximum points present in the differential pore volume distribution of MCC, the differential pore volume value X of the first maximum point where the differential pore volume is the largest is 0.15 cm 3 / g or less is preferable, and 0.12 cm 3 / g or less is more preferable, and 0.10cm 3 / g or less is more preferable. The lower limit of X is 0.01 cm 3 / g or more is preferable, and 0.02 cm 3 / g or more is more preferable. The above lower and upper limits of X can be arbitrarily combined. X is 0.01 to 0.15 cm 3 / g is preferred, 0.02-0.12cm 3 / g is more preferable, 0.02-0.10cm 3 / g is more preferred.

[0041] Under the condition that A / B satisfies the above range, an MCC with X satisfying the above range means that the number of pores with a specific pore size is not excessive, and there is variation in the pore size. Such an MCC allows lithium compounds to easily penetrate into the interior of the particles, and as explained above, it is possible to produce a lithium secondary battery with higher initial charge / discharge efficiency.

[0042] Among the maximum points present in the differential pore volume distribution, the ratio X / Y of the differential pore volume value Y of the second maximum point having the next largest differential pore volume after the first maximum point is preferably 7 or less, more preferably 5 or less. X / Y is preferably 1 or more. The above lower and upper limits of X / Y can be arbitrarily combined. X / Y is preferably 1-7, more preferably 1-5.

[0043] This means that MCCs with X / Y satisfying the above ranges when A / B satisfies the above ranges have variations in pore size. Such MCCs allow lithium compounds to easily penetrate into the interior of the particles, and as explained above, lithium secondary batteries with higher initial charge / discharge efficiency can be manufactured.

[0044] The MCC is preferably represented by the following formula (I): Ni (1-x-y) M1 x M2 y O z (OH) 2-α (I) (In formula (I), 0≦x≦0.8, 0≦y≦0.2, 0≦x+y<1, 0≦z≦3, −0.5≦α≦2, and α−z<2; M1 is one or more elements selected from the group consisting of Co, Mn, and Al; and M2 is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.)

[0045] (x) x is preferably 0.05 or more, more preferably 0.10 or more. x is preferably 0.5 or less, more preferably 0.4 or less, and even more preferably 0.3 or less. The above lower and upper limits of x can be combined arbitrarily. From the viewpoint of improving the initial charge / discharge efficiency of the battery, x is preferably 0 to 0.5, more preferably 0.05 to 0.4, and even more preferably 0.10 to 0.3.

[0046] (y) y is preferably 0.15 or less, more preferably 0.1 or less, and even more preferably 0.05 or less. The above lower limit and upper limit of y can be arbitrarily combined. From the viewpoint of improving the initial charge-discharge efficiency of the battery, y is preferably 0 - 0.15, more preferably 0 - 0.1, and even more preferably 0 - 0.05.

[0047] (x + y) x + y preferably exceeds 0, more preferably is 0.03 or more, and even more preferably is 0.05 or more. x + y is preferably 0.7 or less, more preferably 0.6 or less, even more preferably 0.4 or less, and particularly preferably 0.3 or less. The above lower limit and upper limit of x + y can be arbitrarily combined. From the viewpoint of improving the initial charge-discharge efficiency of the battery, x + y preferably exceeds 0 and is 0.7 or less, more preferably exceeds 0 and is 0.6 or less, even more preferably is 0.03 - 0.4, and particularly preferably is 0.05 - 0.3.

[0048] From the viewpoint of improving the initial charge-discharge efficiency of the battery, it is preferable that the formula (I) satisfies 0 < x + y ≦ 0.6.

[0049] <000023�>From the viewpoint of obtaining a lithium secondary battery with a high initial charge-discharge efficiency, the element M2 is preferably at least one element selected from the group consisting of Ti, Mg, W, Nb, and Zr.

[0050] [Composition analysis] The composition of MCC is measured using an ICP emission spectrometer after dissolving MCC in hydrochloric acid. As the ICP emission spectrometer, for example, Optima8300 (manufactured by PerkinElmer, Inc.) can be used.

[0051] ≪Method for manufacturing MCC≫ MCC can be manufactured by a batch-type coprecipitation method or a continuous-type coprecipitation method. Hereinafter, taking a metal composite hydroxide containing Ni and the element M1 as an example, the manufacturing method will be described in detail.

[0052] First, by a co-precipitation method, particularly the continuous co-precipitation method described in JP-A-2002-201028, for example, a nickel salt solution, a metal salt solution of element M1, an alkaline aqueous solution, and, if necessary, a complexing agent are mixed in a reaction tank to produce a metal composite hydroxide containing Ni and element M1.

[0053] As the nickel salt that is the solute of the nickel salt solution, for example, one or more of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate can be used.

[0054] As the metal salt that is the solute of the metal salt solution of element M1, for example, cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt acetate, manganese sulfate, manganese nitrate, manganese chloride, manganese acetate, aluminum sulfate, sodium aluminate, etc. can be used.

[0055] The above metal salts are used in proportions corresponding to the composition ratio of the above formula (I), and water is used as the solvent.

[0056] When a nickel salt solution, a metal salt solution of element M1, an alkaline aqueous solution, and optionally a complexing agent are continuously supplied to a reaction vessel, Ni and element M1 react to form Ni (1-x) M1 x (OH) 2-α Crystal nuclei are generated. Furthermore, by continuously supplying these raw materials, the nuclei grow. In this case, the nickel salt solution and the metal salt solution of element M1 may be mixed to prepare a mixed solution before being supplied to the reaction vessel, and the mixed solution may be supplied to the reaction vessel. Furthermore, the nickel salt solution, the metal salt solution of element M1, and the mixed solution may each be supplied to the reaction vessel from multiple supply ports.

[0057] The complexing agent is a compound capable of forming a complex with Ni and ions of element M1 in an aqueous solution, such as ammonium ion donors, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine.

[0058] Examples of the ammonium ion donor include ammonium salts such as ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride.

[0059] The complexing agent may not be included. When the complexing agent is included, the amount of the complexing agent contained in the mixed solution containing the nickel salt solution, the metal salt solution of the element M1, and the complexing agent is, for example, such that the molar ratio of the amount of the complexing agent to the total number of moles of the nickel salt and the metal salt of the element M1 in the mixed solution is greater than 0 and less than or equal to 2.0.

[0060] In the coprecipitation method, an alkaline aqueous solution is added to the mixed solution before the pH of the mixed solution changes from alkaline to neutral in order to adjust the pH value of the mixed solution. Examples of alkaline aqueous solutions include an aqueous solution of sodium hydroxide and an aqueous solution of potassium hydroxide.

[0061] The pH value in this specification is defined as the value measured when the temperature of the mixed solution is 40° C. If the temperature of the mixed solution sampled from the reaction tank is not 40° C., the pH is measured after heating or cooling the mixed solution to 40° C.

[0062] During the reaction, the temperature of the liquid raw material supplied to the reaction vessel is controlled within a predetermined range. Here, the liquid raw material refers to a nickel salt solution, a metal salt solution of element M1, or a mixed solution thereof supplied to a reaction vessel. During the reaction, the temperature of the liquid raw materials is adjusted to 10-40° C. When multiple types of liquid raw materials are used, the temperatures of the liquid raw materials may be different or the same as long as they are within the above temperature range. Furthermore, the set temperature of the reaction vessel is adjusted to 70°C or higher, preferably within the range of 70-75°C. The set temperature of the reaction vessel and the temperature of the liquid raw material are adjusted so that the temperature difference between the set temperature of the reaction vessel and the temperature of the liquid raw material is 30°C or more.

[0063] By adjusting the set temperature of the reaction vessel within the above range and adjusting the temperature difference between the set temperature of the reaction vessel and the temperature of the liquid raw material to 30°C or more, the solubility of the metal salt contained in the liquid raw material supplied to the reaction vessel is improved, making it difficult for crystals to precipitate. As a result, under the above temperature difference conditions, the nucleus growth rate tends to be faster than the nucleus generation rate. Under these conditions, the size of the primary particles varies, and the size of the pores formed when the primary particles aggregate also varies. As a result, an MCC having an A / B ratio within the above range can be obtained. Furthermore, by performing the process under these conditions, an MCC can be obtained in which the number of maximum pore diameters in each range, X, and X / Y, are within the above ranges.

[0064] It is preferable to carry out the process under conditions where the total flow rate (L / h) of the liquid raw materials supplied to the reaction vessel is 0.10 or less relative to the reaction vessel volume (L). By supplying the liquid raw materials within this range, even if a liquid raw material with a temperature significantly different from the reaction vessel's set temperature is supplied to the reaction vessel, the temperature of the liquid in the reaction vessel after supply is unlikely to deviate from the reaction vessel's set temperature. Therefore, the temperature difference between the reaction vessel's set temperature and the liquid raw material can be maintained at 30°C or more. When multiple liquid raw materials are supplied to the reaction vessel from multiple supply ports, the total flow rate (L / h) of the liquid raw materials supplied to the reaction vessel refers to the sum of the flow rates (L / h) of all liquid raw materials supplied to the reaction vessel. For example, when a mixed solution V consisting of a nickel salt and a metal salt of a certain element M1 and a metal salt solution W of another element M1 are supplied to the reaction vessel from two supply ports, respectively, the total flow rate of the liquid raw materials supplied to the reaction vessel is the sum of the flow rates of the mixed solution V and the metal salt solution W.

[0065] During the reaction, the pH value of the mixture in the reaction vessel is controlled within the range of 9 to 13, preferably 10.5 to 13.

[0066] The materials in the reaction vessel are mixed by suitable stirring. As a reaction vessel used in the continuous coprecipitation method, an overflow type reaction vessel can be used in order to separate the formed reaction precipitate.

[0067] In order to control the atmosphere inside the reaction vessel to the desired level, a predetermined gas may be passed through the reaction vessel or the liquid present in the reaction vessel may be directly bubbled. After the reaction, the resulting reaction precipitate is washed with water and then isolated, for example, by dehydrating a slurry containing the reaction precipitate by centrifugation or suction filtration. The isolated reaction precipitate is washed, dehydrated, dried and sieved as necessary to obtain a metal composite hydroxide. After drying, classification may be carried out as appropriate.

[0068] The reaction precipitate is preferably washed with a washing liquid such as water, weak acid water, or alkaline washing liquid, etc. As the washing liquid, an alkaline washing liquid is preferred, and an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is more preferred. It is preferable to wash with a washing solution having a mass of 10 times or more the mass of the reaction precipitate. The temperature of the washing solution used is preferably 30° C. or higher. Furthermore, it is preferable to wash at least once. After washing with a washing liquid other than water, it is preferable to further wash with water to prevent compounds derived from the washing liquid from remaining in the reaction precipitate.

[0069] The drying temperature is preferably 80 to 250° C., more preferably 90 to 230° C. The drying time is preferably 0.5 to 30 hours, more preferably 1 to 25 hours. The drying pressure may be either normal pressure or reduced pressure.

[0070] When producing a metal composite oxide as MCC, the metal composite oxide can be obtained by heating a metal composite hydroxide. If necessary, multiple heating steps may be performed. In this specification, the heating temperature refers to the set temperature of the heating device. In the case of multiple heating steps, the heating temperature refers to the temperature at the highest holding temperature in each heating step.

[0071] The heating temperature is, for example, 300 to 700°C, preferably 400 to 700°C, and more preferably 450 to 680°C. The time for maintaining the heating temperature is, for example, 0.1 to 20 hours, preferably 0.5 to 10 hours. The rate of temperature increase to the heating temperature is, for example, 50 to 400°C / hour. The heating atmosphere may be air, oxygen, nitrogen, argon, or a mixed gas thereof.

[0072] <Method of manufacturing a positive electrode active material for lithium secondary batteries> CAM can be produced using the above-mentioned MCC as a raw material.

[0073] The method for producing CAM includes a calcination step of calcining a mixture of MCC and a lithium compound. The method for producing CAM may include a mixing step of mixing MCC and a lithium compound before the calcination step, and a washing step of washing the calcined product obtained after the calcination step.

[0074] [Mixing process] MCC and a lithium compound are mixed. 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.

[0075] The lithium compound and MCC are mixed in consideration of the composition ratio of the final target product to obtain a mixture of the lithium compound and MCC. The amount (molar ratio) of Li contained in the lithium compound relative to the total amount of elements other than oxygen atoms contained in MCC, 1, is preferably 0.96 to 1.20, more preferably 0.98 to 1.18, and even more preferably 1.00 to 1.16.

[0076] [Firing process] The resulting mixture is fired. By firing the mixture, CAM crystals grow. The firing process may include multiple firing stages with different firing temperatures.

[0077] The firing temperature in this specification refers to the temperature of the atmosphere in the firing furnace, and means the maximum temperature that can be maintained (maximum maintenance temperature). When the firing process has a plurality of firing stages, the firing temperature means the temperature of the stage in which firing is carried out at the highest holding temperature among the firing stages.

[0078] The firing temperature is preferably 400 to 1000°C, more preferably 500 to 980°C, and even more preferably 600 to 960°C.

[0079] The time for which the firing temperature is maintained is, for example, 0.1 to 30 hours, preferably 0.5 to 20 hours.

[0080] In the firing step, firing is preferably carried out in an oxygen-containing atmosphere. Specifically, oxygen gas is preferably introduced into the firing furnace to create an oxygen-containing atmosphere.

[0081] [Cleaning process] In this embodiment, the fired product may be washed with a cleaning solution such as pure water or an alkaline cleaning solution, and the fired product after washing may be dried as appropriate.

[0082] The fired product, which has been washed and dried as appropriate, may be crushed and sieved as appropriate. Through the above steps, a CAM is obtained.

[0083] According to the MCC having the above-mentioned structure, it is possible to manufacture a CAM that can improve the initial charge-discharge efficiency of a lithium secondary battery.

[0084] Furthermore, according to the above-described method for producing CAM, by using the above-described MCC as a raw material, CAM that can improve the initial charge-discharge efficiency of a lithium secondary battery can be obtained.

[0085] <Lithium secondary battery> A positive electrode for a lithium secondary battery suitable for use with the above-mentioned CAM will be described below. Hereinafter, the positive electrode for a lithium secondary battery may be referred to as the positive electrode. Furthermore, a lithium secondary battery suitable for use as a positive electrode will be described.

[0086] An example of a suitable lithium secondary battery for use with 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.

[0087] 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.

[0088] First, as shown in the partially enlarged view of 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 stacked in this order: separator 1, positive electrode 2, separator 1, negative electrode 3, and then wound to form an electrode group 4.

[0089] The positive electrode 2 includes, for example, a positive electrode active material layer 2a containing CAM and a positive electrode current collector 2b having the positive electrode active material layer 2a formed on one surface thereof. Such a positive electrode 2 can be manufactured by first preparing a positive electrode mixture containing CAM, a conductive material, and a binder, and then supporting the positive electrode mixture on one surface of the positive electrode current collector 2b to form the positive electrode active material layer 2a.

[0090] Examples of the negative electrode 3 include an electrode in which a negative electrode mixture containing a negative electrode active material (not shown) is supported on a negative electrode current collector, and an electrode made of a negative electrode active material alone, and can be manufactured in the same manner as the positive electrode 2.

[0091] Next, the electrode group 4 and an insulator (not shown) are placed 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 top of the battery can 5 is sealed with a top insulator 7 and a sealing member 8, whereby a lithium secondary battery 10 can be manufactured.

[0092] The shape of the electrode group 4 can be, for example, a columnar shape such that the cross section of the electrode group 4 cut perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners.

[0093] The shape of a lithium secondary battery having such an electrode group 4 can be any shape specified by IEC60086, a standard for batteries established by the International Electrotechnical Commission (IEC), or JIS C 8500. Examples of shapes include a cylindrical shape and a rectangular shape.

[0094] 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 laminated lithium secondary batteries include so-called coin type batteries, button type batteries, and paper type (or sheet type) batteries.

[0095] The positive electrode, separator, negative electrode, and electrolyte constituting the lithium secondary battery can be, for example, the configuration, materials, and manufacturing method described in

[0113] to

[0140] of WO2022 / 113904A1.

[0096] <All-solid-state lithium secondary battery> The CAM can be used as a CAM for an all-solid-state lithium secondary battery.

[0097] 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 includes 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 also have a bipolar structure in which a CAM and a negative electrode active material are disposed on both sides of a current collector. A specific example of a bipolar structure is the structure described in JP-A-2004-95400.

[0098] The positive electrode 110 has a positive electrode active material layer 111 and a positive electrode current collector 112. The positive electrode active material layer 111 contains the above-mentioned CAM and solid electrolyte. The positive electrode active material layer 111 may also contain a conductive material and a binder.

[0099] 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.

[0100] 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.

[0101] 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 .

[0102] A container molded from a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel can be used as exterior body 200. Alternatively, a container formed into a bag shape from a laminate film with corrosion resistance applied to at least one surface can also be used as exterior body 200.

[0103] The all-solid-state lithium secondary battery 1000 may have any shape, such as a coin shape, a button shape, a paper shape (or a sheet shape), a cylindrical shape, a square shape, or a laminate shape (pouch shape).

[0104] 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.

[0105] For the all-solid-state lithium secondary battery, for example, the configuration, materials, and manufacturing method described in

[0151] to

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

[0106] The present invention encompasses the following

[11] to

[18] .

[11] An MCC containing at least Ni, wherein A / B is 0.10 - 1.2, the MCC.

[12] The MCC according to

[11] , having two or more maximum points in the region where the pore diameter is 20 - 150 nm in the differential pore volume distribution.

[13] The MCC according to

[11] or

[12] , having one or more maximum points in the region where the pore diameter is 20 - 50 nm and one or more maximum points in the region where the pore diameter exceeds 50 nm and is 200 nm or less in the differential pore volume distribution.

[14] X is 0.02 - 0.12 cm 3 / g or less, the MCC according to any one of

[11] to

[13] .

[15] X / Y is 1 - 5, the MCC according to any one of

[11] to

[14] .

[16] The MCC according to any one of

[11] to

[15] , represented by the above formula (I).

[17] The above formula (I) satisfies 0 < x + y ≤ 0.6, the MCC according to

[16] .

[18] A method for producing CAM, comprising a step of firing a mixture of the MCC according to any one of

[11] to

[17] and a lithium compound.

[0107] As described above, the preferred embodiments of the present invention have been described while referring to the accompanying drawings, but the present invention is not limited to such examples. The various shapes, combinations, etc. of the constituent members shown in the above examples are merely examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

Examples

[0108] Next, the present invention will be described in more detail with reference to examples.

[0109] <Composition analysis> The composition of the MCC was analyzed by the method described in the above <Composition analysis>.

[0110] <Obtaining differential pore volume distribution> As described above in [Method for obtaining differential pore volume distribution], the differential pore volume distribution of MCC was obtained, and the values ​​of A and B defined above and the positions of the maximum points were determined. From the obtained values, A / B, the number of maximum points in each pore diameter range, X, and X / Y were calculated.

[0111] <Measurement of initial charge / discharge efficiency> The initial charge-discharge efficiency was measured by the method described in [Measurement of initial charge-discharge efficiency] above.

[0112] Example 1 Water was placed in a reaction vessel equipped with a rotary stirring device with stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was supplied, and the liquid temperature was maintained at 70°C (the set temperature of the reaction vessel). A mixed solution was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate so that the molar ratio of Ni:Co:Mn was 83.0:12.1:4.9, and the mixed solution was maintained at 25°C (temperature of the liquid raw materials).

[0113] Next, the mixed solution was continuously fed into the reaction vessel under stirring so that the total flow rate (L / h) of the mixed solution relative to the volume (L) of the reaction vessel was 0.10 or less, and at the same time, an aqueous solution of ammonium sulfate was continuously fed as a complexing agent. At this time, while maintaining the liquid temperature at 70°C (the set temperature of the reaction vessel), an aqueous solution of sodium hydroxide was added dropwise at appropriate times so that the pH of the mixed solution in the reaction vessel became 11.2 (measurement temperature: 40°C), and reaction precipitate 1 was obtained.

[0114] Reaction precipitate 1 was washed using a 20-fold mass of aqueous sodium hydroxide solution (sodium hydroxide concentration: 5 mass%) relative to the mass of reaction precipitate 1. After washing, the precipitate was dehydrated using a filter press, washed with water, dehydrated, isolated, and dried at 105°C for 20 hours to obtain metal composite hydroxide 1. When the composition of metal composite hydroxide 1 is represented by the above formula (I), x was 0.17, y was 0, and M1 was Co and Mn.

[0115] <Example 2> Water was placed in a reaction vessel equipped with a rotary stirring device with stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was supplied, and the liquid temperature was maintained at 70°C (the set temperature of the reaction vessel). A mixed solution was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of manganese sulfate, and an aqueous solution of aluminum sulfate so that the molar ratio of Ni:Mn:Al was 93.0:1.0:6.0, and the mixed solution was maintained at 25°C (temperature of the liquid raw materials).

[0116] Next, the mixed solution was continuously fed into the reaction vessel under stirring so that the total flow rate (L / h) of the mixed solution relative to the volume (L) of the reaction vessel was 0.10 or less, and at the same time, an aqueous solution of ammonium sulfate was continuously fed as a complexing agent. At this time, while maintaining the liquid temperature at 70°C (the set temperature of the reaction vessel), an aqueous solution of sodium hydroxide was added dropwise at appropriate times so that the pH of the mixed solution in the reaction vessel became 10.8 (measurement temperature: 40°C), and reaction precipitate 2 was obtained.

[0117] Reaction precipitate 2 was washed using a 20-fold mass of aqueous sodium hydroxide solution (sodium hydroxide concentration: 5 mass%) relative to the mass of reaction precipitate 2. After washing, the precipitate was dehydrated using a filter press, washed with water, dehydrated, isolated, and dried at 125°C for 24 hours to obtain metal composite hydroxide 2. When the composition of metal composite hydroxide 2 was represented by the above formula (I), x was 0.07, y was 0, and M1 was Mn and Al.

[0118] Example 3 Water was placed in a reaction vessel equipped with a rotary stirring device with stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was supplied, and the liquid temperature was maintained at 70°C (the set temperature of the reaction vessel). A mixed solution was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate so that the molar ratio of Ni:Co:Mn was 82.5:5.1:12.4, and the mixed solution was maintained at 25°C (temperature of the liquid raw materials).

[0119] Next, the mixed solution was continuously fed into the reaction vessel under stirring so that the total flow rate (L / h) of the mixed solution relative to the volume (L) of the reaction vessel was 0.10 or less, and at the same time, an aqueous solution of ammonium sulfate was continuously fed as a complexing agent. At this time, while maintaining the liquid temperature at 70°C (the set temperature of the reaction vessel), an aqueous solution of sodium hydroxide was added dropwise at appropriate times so that the pH of the mixed solution in the reaction vessel became 11.1 (measurement temperature: 40°C), and reaction precipitate 3 was obtained.

[0120] Metal composite hydroxide 3 was obtained in the same manner as in Example 1, except that reaction precipitate 3 was used instead of reaction precipitate 1. When the composition of metal composite hydroxide 3 is represented by the above formula (I), x was 0.18, y was 0, and M1 was Co and Mn.

[0121] Example 4 Water was placed in a reaction vessel equipped with a rotary stirring device with stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was supplied, and the liquid temperature was maintained at 70°C (the set temperature of the reaction vessel). A mixed solution was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of aluminum sulfate so that the molar ratio of Ni:Co:Al was 88.0:9.0:3.0, and the mixed solution was maintained at 35°C (temperature of the liquid raw materials).

[0122] Next, the mixed solution was continuously fed into the reaction vessel under stirring so that the total flow rate (L / h) of the mixed solution relative to the volume (L) of the reaction vessel was 0.10 or less, and at the same time, an aqueous solution of ammonium sulfate was continuously fed as a complexing agent. At this time, while maintaining the liquid temperature at 70°C (the set temperature of the reaction vessel), an aqueous solution of sodium hydroxide was added dropwise at appropriate times so that the pH of the mixed solution in the reaction vessel became 11.5 (measurement temperature: 40°C), and reaction precipitate 4 was obtained.

[0123] Metal composite hydroxide 4 was obtained in the same manner as in Example 2, except that reaction precipitate 4 was used instead of reaction precipitate 2. When the composition of metal composite hydroxide 4 is represented by the above formula (I), x was 0.12, y was 0, and M1 was Co and Al.

[0124] <Comparative Example 1> Water was placed in a reaction vessel equipped with a rotary stirring device with stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was supplied, and the liquid temperature was maintained at 45°C (the set temperature of the reaction vessel). A mixed solution was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of manganese sulfate, and an aqueous solution of aluminum sulfate so that the molar ratio of Ni:Mn:Al was 93.0:3.5:3.5, and was maintained at 25°C (temperature of the liquid raw materials).

[0125] Next, the mixed solution was continuously fed into the reaction vessel under stirring so that the total flow rate (L / h) of the mixed solution relative to the volume (L) of the reaction vessel was 0.10 or less, and at the same time, an aqueous solution of ammonium sulfate was continuously fed as a complexing agent. At this time, while maintaining the liquid temperature at 45°C (the set temperature of the reaction vessel), an aqueous solution of sodium hydroxide was added dropwise at appropriate times so that the pH of the mixed solution in the reaction vessel became 12.0 (measurement temperature: 40°C), and reaction precipitate 5 was obtained.

[0126] Metal composite hydroxide 5 was obtained in the same manner as in Example 2, except that reaction precipitate 5 was used instead of reaction precipitate 2. When the composition of metal composite hydroxide 5 is represented by the above formula (I), x was 0.07, y was 0, and M1 was Mn and Al.

[0127] <Comparative Example 2> Water was placed in a reaction vessel equipped with a rotary stirring device with stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was supplied, and the liquid temperature was maintained at 40°C (the set temperature of the reaction vessel). A mixed solution was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate so that the molar ratio of Ni:Co:Mn was 83.5:5.1:11.4, and the mixed solution was maintained at 25°C (temperature of the liquid raw materials).

[0128] Next, the mixed solution was continuously fed into the reaction vessel under stirring so that the total flow rate (L / h) of the mixed solution relative to the volume (L) of the reaction vessel was 0.10 or less, and at the same time, an aqueous solution of ammonium sulfate was continuously fed as a complexing agent. At this time, while maintaining the liquid temperature at 40°C (the set temperature of the reaction vessel), an aqueous solution of sodium hydroxide was added dropwise at appropriate times so that the pH of the mixed solution in the reaction vessel became 10.6 (measurement temperature: 40°C), and reaction precipitate 6 was obtained.

[0129] Metal composite hydroxide 6 was obtained in the same manner as in Example 2, except that reaction precipitate 6 was used instead of reaction precipitate 2. When the composition of metal composite hydroxide 6 is represented by the above formula (I), x was 0.17, y was 0, and M1 was Co and Mn.

[0130] [Table 1]

[0131] Table 1 shows A, B, A / B, the number of maximum points in each range of pore diameter, X, and X / Y of the metal composite hydroxides of Examples 1 to 4 and Comparative Examples 1 and 2, as well as the initial charge-discharge efficiency values ​​of the lithium secondary batteries fabricated using the metal composite hydroxides as MCC. As shown in Table 1, the metal composite hydroxides of Examples 1 to 4, in which A / B was less than 1.5, had higher initial charge-discharge efficiency than those of Comparative Examples 1 and 2. The metal composite hydroxides of Examples 1 to 4 had variations in pore size and non-uniform pore distribution, so when mixed with a lithium compound, the lithium compound easily penetrated into the interior of the particles, and when MCC and the lithium compound were mixed and fired, the reaction between MCC and the lithium compound occurred evenly on the surface and inside of the MCC. Furthermore, CAM was obtained in which Li was uniformly distributed from the center to near the surface of the particle, which is thought to have resulted in high initial charge / discharge efficiency of the battery.

[0132] The metal composite hydroxides of Comparative Examples 1 and 2 had an A / B ratio of 1.5 or more, and had lower initial charge-discharge efficiency than those of Examples 1 to 4. This is thought to be because the metal composite hydroxides of Comparative Examples 1 and 2 had many fine pores, making it difficult for the lithium compound to penetrate into the interior of the particles, and CAMs were obtained in which Li was distributed non-uniformly compared to the Examples. [Explanation of symbols]

[0133] 1: separator, 2: positive electrode, 2a: positive electrode active material layer, 2b: positive electrode current collector layer, 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, 31: negative 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

Claims

1. A metal composite compound containing at least Ni, In the differential pore volume distribution obtained from the nitrogen gas adsorption isotherm by the Barrett-Joyner-Halenda method, when the integrated area of ​​the region where the pore diameter is 1 nm or more and 50 nm or less is defined as A and the integrated area of ​​the region where the pore diameter is more than 50 nm and 200 nm or less is defined as B, the metal composite compound has A metal complex compound in which A / B is 0.05 or more and less than 1.

5.

2. 2. The metal complex compound according to claim 1, wherein the differential pore volume distribution has two or more maximum points in a region where the pore diameter is 20 nm or more and 150 nm or less.

3. 3. The metal complex compound according to claim 1, wherein the differential pore volume distribution has one or more maximum points in a pore diameter range of 20 nm to 50 nm, and one or more maximum points in a range of more than 50 nm to 200 nm.

4. Among the maximum points present in the differential pore volume distribution, the differential pore volume value X of the first maximum point having the largest differential pore volume is 0.15 m ３ The metal complex compound according to claim 1 or 2, wherein the metal complex compound has a molecular weight of 1 / g or less.

5. 3. The metal composite compound according to claim 1, wherein a ratio X / Y of a differential pore volume value X of a first maximum point having the largest differential pore volume among the maximum points present in the differential pore volume distribution to a differential pore volume value Y of a second maximum point having the second largest differential pore volume after the first maximum point is 7 or less.

6. The metal complex compound according to claim 1 or 2, which is represented by the following formula (I): Ni （１－ｘ－ｙ） M1 ｘ M2 ｙ O ｚ (OH) ２－α (I) (In formula (I), 0≦x≦0.8, 0≦y≦0.2, 0≦x+y<1, 0≦z≦3, −0.5≦α≦2, and α−z<2; M1 is one or more elements selected from the group consisting of Co, Mn, and Al; and M2 is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Zn, Sn, Zr, Nb, Ga, W, Mo, B, and Si.)

7. The metal complex compound according to claim 6 , wherein the formula (I) satisfies 0<x+y≦0.

6.

8. A method for producing a positive electrode active material for a lithium secondary battery, comprising a step of firing a mixture of the metal composite compound according to claim 1 or 2 and a lithium compound.

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