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

Abstract

To provide a method for producing a metal composite compound that enables production of a lithium secondary battery exhibiting a high cycle retention rate, and a method for producing a positive electrode active material for a lithium secondary battery.SOLUTION: A method for producing a metal composite compound containing at least Ni and Al, the method comprising a neutralization step for adding at least a nickel salt solution, an aluminum salt solution, and an alkaline aqueous solution to a reaction tank to obtain a metal composite hydroxide, wherein in the neutralization step, the dissolved Ni concentration in a reaction slurry present in the reaction tank is 10 mg / L or more and 150 mg / L or less, and the dissolved Al concentration is more than 0 mg / L and 10 mg / L or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] As a method for producing a positive electrode active material for a lithium secondary battery, for example, there is a method in which a lithium compound and a metal composite compound containing a metal element other than Li are mixed and fired.

[0003] In order to obtain the metal complex compound, the production conditions have been investigated.

[0004] For example, Patent Document 1 discloses a method for producing a nickel-manganese composite hydroxide, which includes a crystallization step of neutralizing salts containing at least nickel and manganese in an aqueous reaction solution to produce a nickel-manganese composite hydroxide, and is characterized in that in the crystallization step, the dissolved oxygen concentration, the dissolved nickel concentration, and the stirring power applied to the aqueous reaction solution are adjusted to control the volume average particle size and the coarse-grain density, which is expressed as [(void area inside the secondary particles / cross-sectional area of ​​the secondary particles)×100] (%), within desired ranges. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP-A-2018-024570 Summary of the Invention [Problem to be solved by the invention]

[0006] As the range of applications for lithium secondary batteries expands, there is a demand for further improvements in cycle retention.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to provide a method for producing a metal composite compound capable of obtaining a lithium secondary battery having a high cycle retention rate, and a method for producing a positive electrode active material for a lithium secondary battery.

Means for Solving the Problems

[0008] In order to solve the above problems, the present invention includes the following aspects. [1] A method for producing a metal composite compound containing at least Ni and Al, comprising a neutralization step of adding at least a nickel salt solution, an aluminum salt solution, and an alkaline aqueous solution to a reaction tank to obtain a metal composite hydroxide, wherein in the neutralization step, the dissolved Ni concentration in the reaction slurry present in the reaction tank is 10 mg / L or more and 150 mg / L or less, and the dissolved Al concentration is more than 0 mg / L and 10 mg / L or less. A method for producing a metal composite compound. [2] The method for producing a metal composite compound according to [1], wherein the metal composite compound is represented by the following formula (I). Ni (1-x-y-w) Al w M1 x M2 y O z (OH) 2-α ···(I) [In formula (I), 0 < w ≦ 0.4, 0 ≦ x ≦ 0.4, 0 ≦ y ≦ 0.2, 0 < x + y + w < 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 and Mn, 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.] [3] The method for producing a metal composite compound according to [2], wherein in the formula (I), 0 < x + y + w ≦ 0.3. [4] The method for producing a metal composite compound according to any one of [1] to [3], wherein the dissolved Ni concentration with respect to the dissolved Al concentration is 50 or more. [5] The method for producing a metal complex compound according to any one of [1] to [4], wherein an ammonium ion donor is further added in the neutralization step, and the ammonium ion concentration in the reaction slurry is 2.5 g / L or more and 20 g / L or less. [6] A method for producing a positive electrode active material for a lithium secondary battery, comprising: a calcination step of calcining a mixture of the metal composite compound obtained by the method for producing a metal composite compound according to any one of [1] to [5] and a lithium compound. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for producing a metal composite compound that can provide a lithium secondary battery with a high cycle retention rate, and a method for producing a positive electrode active material for a lithium secondary battery. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a lithium secondary battery. [Figure 2] FIG. 1 is a schematic diagram showing the overall configuration of an all-solid-state lithium secondary battery. DETAILED DESCRIPTION OF THE INVENTION

[0011] In this specification, a metal composite compound is hereinafter referred to as "MCC," and a cathode active material for lithium secondary batteries is hereinafter referred to as "CAM."

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

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

[0014] [Method for Measuring Cycle Retention Rate] In this specification, the "cycle retention rate" is a value measured by manufacturing a lithium secondary battery by the following method and performing a test of repeating charge and discharge cycles 50 times under the conditions shown below for the lithium secondary battery.

[0015] [Manufacture of CAM] Weigh and mix MCC and lithium hydroxide monohydrate powder at 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 (for example, Li / (Ni + Al + M1 + M2)) is 1.02 to obtain a mixture. The obtained mixture is fired at 740 °C for 5 hours in an oxygen-containing atmosphere to obtain CAM.

[0016] [Manufacture of Positive Electrode for Lithium Secondary Battery] CAM, a conductive material (acetylene black), and a binder (PVdF) are added and kneaded at a ratio such that the composition is 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. The obtained positive electrode mixture is applied to an Al foil with a thickness of 20 μm serving as a current collector and vacuum dried 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 cm 2 shall be.

[0017] [Manufacture of Lithium Secondary Battery] The following operations are performed inside a glove box in 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. 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 (coin-type half cell R2032).

[0018] <Charge-discharge cycle test> Test temperature: 25℃ Maximum charging voltage 4.3V, charging current 0.5CA, constant current constant voltage charging Minimum discharge voltage 2.5V, discharge current 1CA, constant current discharge The discharge capacity at the 50th cycle is divided by the discharge capacity at the 1st cycle to calculate the cycle retention rate (%).

[0019] (MCC manufacturing method) The method for producing MCC of this embodiment includes a neutralization step of adding at least a nickel salt solution, an aluminum salt solution, and an alkaline aqueous solution to a reaction vessel to obtain a metal composite hydroxide. MCC contains at least Ni and Al. Examples of MCC include metal composite oxides, metal composite hydroxides, and mixtures thereof. Note that the metal composite hydroxide may contain a partially oxidized compound.

[0020] [Neutralization process] In the neutralization step, the dissolved Ni concentration in the reaction slurry present in the reaction tank is 10 to 150 mg / L, and the dissolved Al concentration is more than 0 mg / L and 10 mg / L or less. Here, the term "reaction slurry" refers to a mixture of solids and liquids present in a reaction vessel, specifically a mixture of liquids and solids, including precipitates, produced by the reaction of a mixed solution containing a nickel salt solution, an aluminum salt solution, and an alkaline aqueous solution. The term "dissolved Ni concentration" refers to the concentration of Ni dissolved in the liquid of the reaction slurry, and does not include Ni present in precipitates that may be present as solids in the reaction slurry. The term "dissolved Al concentration" refers to the concentration of Al dissolved in the liquid of the reaction slurry, and does not include Al present in precipitates that may be present as solids in the reaction slurry.

[0021] The concentration of dissolved Ni in the reaction slurry is preferably 12 mg / L or more, and more preferably 14 mg / L or more. On the other hand, the dissolved Ni concentration in the reaction slurry is preferably 100 mg / L or less, more preferably 80 mg / L or less, even more preferably 50 mg / L or less, and particularly preferably 30 mg / L or less.

[0022] If the dissolved Ni concentration in the reaction slurry is 10 mg / L or higher, nucleation in the reaction tank tends to be unstable and non-uniform. By steadily generating a non-uniform reaction, it is possible to produce an MCC with pores of a wide range of diameters inside. Furthermore, if the dissolved Ni concentration in the reaction slurry is equal to or higher than the above-mentioned preferred lower limit, it is possible to produce an MCC with more voids. Using such an MCC makes it easier to obtain a battery with a high cycle retention rate. On the other hand, when the dissolved Ni concentration in the reaction slurry is 150 mg / L or less, preferably below the upper limit, nucleation and growth occur in a well-balanced manner, which tends to improve the internal homogeneity of the MCC. In the CAM obtained by firing such an MCC, lithium ion intercalation and deintercalation occur uniformly throughout the particle, which tends to suppress localized degradation and particle cracking. Therefore, it is easy to obtain a battery with a high cycle retention rate.

[0023] The upper and lower limits of the dissolved Ni concentration in the reaction slurry can be arbitrarily combined. The dissolved Ni concentration in the reaction slurry is preferably 12 to 100 mg / L, more preferably 12 to 80 mg / L, even more preferably 12 to 50 mg / L, and particularly preferably 14 to 30 mg / L.

[0024] The dissolved Al concentration in the reaction slurry is preferably 8.0 mg / L or less, more preferably 5.0 mg / L or less, even more preferably 1.0 mg / L or less, even more preferably 0.50 mg / L or less, and particularly preferably 0.20 mg / L or less. On the other hand, the dissolved Al concentration in the reaction slurry is preferably 0.05 mg / L or more, more preferably 0.08 mg / L or more, even more preferably 0.10 mg / L or more, and particularly preferably more than 0.10 mg / L. The upper and lower limits of the dissolved Al concentration in the reaction slurry can be arbitrarily combined. The dissolved Al concentration in the reaction slurry is preferably 0.05-8.0 mg / L, more preferably 0.08-5.0 mg / L, even more preferably 0.10-1.0 mg / L, still more preferably 0.10-0.50 mg / L, and particularly preferably greater than 0.10 mg / L and not greater than 0.20 mg / L.

[0025] When the dissolved Al concentration in the reaction slurry is 10 mg / L or less, nucleation and growth occur in a good balance, and the homogeneity inside the MCC is easily improved. Furthermore, when the dissolved Al concentration in the reaction slurry is equal to or less than the above-mentioned preferable upper limit, the homogeneity inside the MCC is easily improved. Using such an MCC makes it easy to obtain a battery with a high cycle retention rate. On the other hand, if the dissolved Al concentration in the reaction slurry exceeds 0 mg / L, preferably equal to or greater than the lower limit, nucleation in the reaction vessel tends to be unstable and non-uniform. By steadily generating a non-uniform reaction, MCC with pores of a wide range of diameters can be produced. In the CAM obtained by firing such MCC, lithium ions are inserted and extracted uniformly throughout the particles, which tends to suppress localized degradation and particle cracking. Therefore, batteries with high cycle retention rates are likely to be obtained.

[0026] The ratio of the dissolved Ni concentration to the dissolved Al concentration in the reaction slurry (hereinafter sometimes referred to as dissolved Ni / Al) is preferably 50 or more, more preferably 60 or more, and even more preferably 70 or more. On the other hand, the dissolved Ni / Al is preferably 1000 or less, more preferably 900 or less, even more preferably 800 or less, and particularly preferably 760 or less.

[0027] When the dissolved Ni / Al is equal to or greater than the lower limit, the composition of the resulting MCC is less likely to deviate from the desired composition. On the other hand, when the dissolved Ni / Al ratio is equal to or less than the upper limit, the compositional variation between particles in the resulting MCC can be suppressed. The CAM obtained by firing such an MCC has small compositional variation between particles and improves the uniformity inside the electrode, making it easier to obtain a battery with a high cycle retention rate.

[0028] The upper and lower limits of the dissolved Ni / Al can be combined in any desired manner. The dissolved Ni / Al is preferably 50-1000, more preferably 50-900, even more preferably 60-800, and particularly preferably 70-760.

[0029] [Measurement of dissolved Ni and Al concentrations] The dissolved Ni concentration and dissolved Al concentration in the reaction slurry can be measured by removing the solid content (precipitate) from the reaction slurry and measuring the remaining liquid using an ICP emission spectrometer. As the ICP emission spectrometer, for example, Optima 8300 manufactured by PerkinElmer can be used.

[0030] The neutralization step is preferably carried out by a batch co-precipitation method or a continuous co-precipitation method.

[0031] 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.

[0032] As the aluminum salt that is the solute of the aluminum salt solution, for example, aluminum sulfate or sodium aluminate can be used.

[0033] In the neutralization step, a metal salt solution other than the nickel salt solution and the aluminum salt solution, or a complexing agent may be added. Examples of the metal salt that is the solute of the metal salt solution include sulfates, chlorides, acetates, hydroxides, etc. of element M1 or element M2. the element M1 is one or more elements selected from the group consisting of Co and Mn, The 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. For example, the cobalt salt that is the solute of the cobalt salt solution may be one or more of cobalt sulfate, cobalt nitrate, and cobalt chloride. For example, the manganese salt that is the solute of the manganese salt solution may be one or more of manganese sulfate, manganese nitrate, and manganese chloride. As a solvent for the nickel salt solution, aluminum salt solution, and metal salt solution, for example, water can be used. In the neutralization step, a mixed solution may be obtained by previously mixing some or all of the nickel salt solution, the aluminum salt solution, and the metal salt solution, and then the mixed solution may be added to the reaction vessel.

[0034] In the neutralization step, the concentration of the metal element in each solution supplied to the reaction vessel is preferably adjusted to 20 to 150 g / L. For example, when a nickel salt solution, an aluminum salt solution, and one optional metal salt solution are supplied to the reaction vessel in the neutralization step, the concentrations of Ni, Al, element M1, or element M2 contained in the nickel salt solution, aluminum salt solution, or metal salt solution are preferably adjusted to 20 to 150 g / L. When two or more metal salt solutions are supplied to the neutralization step, the concentrations of the metal elements contained in each metal salt solution are preferably adjusted to 20 to 150 g / L. When the mixed solution is supplied to the reaction vessel in the neutralization step, the total concentration of Ni, Al, element M1, or element M2 contained in the mixed solution is preferably adjusted to 20 to 150 g / L.

[0035] The neutralization step preferably uses a complexing agent, such as an ammonium ion donor, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine. Examples of the ammonium ion donor include ammonium salts such as ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride. Of the above, the complexing agent is preferably an ammonium ion donor. The complexing agent may be used alone or in combination of two or more.

[0036] Examples of the alkaline aqueous solution include an aqueous sodium hydroxide solution and an aqueous potassium hydroxide solution.

[0037] <Method for controlling dissolved Ni and Al concentrations> The dissolved Ni concentration and dissolved Al concentration in the reaction slurry can be controlled by adjusting the temperature of the reaction slurry, the pH of the reaction slurry, the flow rate of the alkaline aqueous solution, the flow rate of the complexing agent if a complexing agent is added, and the ammonium ion concentration if an ammonium ion donor is added. In other words, by adjusting these conditions, the dissolved Ni concentration and dissolved Al concentration in the reaction slurry can be adjusted to fall within the above-mentioned ranges, and the resulting MCC can improve the cycle retention rate of the battery.

[0038] Temperature of reaction slurry The temperature of the reaction slurry is preferably 20 to 80°C, more preferably 30 to 75°C.

[0039] pH of reaction slurry The pH of the reaction slurry is preferably 9.0 to 13.0, more preferably 9.5 to 12.5. The pH value in this specification is defined as the value measured when the temperature of the reaction slurry is 40°C. The pH of the reaction slurry is measured when the temperature of the solution sampled from the reaction tank reaches 40°C. If the temperature of the sampled solution is not 40°C, the pH is measured after heating or cooling the reaction slurry to 40°C.

[0040] Alkaline aqueous solution flow rate When a continuous coprecipitation method is used for the neutralization step, the ratio (L / min.) of the total flow rate (L / min.) of the nickel salt solution, aluminum salt solution, metal salt solution, and the mixed solution to the flow rate (L / min.) of the alkaline aqueous solution supplied to the reaction tank (hereinafter, sometimes referred to as "flow rate ratio a") preferably exceeds 2.5. The flow rate ratio a is preferably 6.5 or less, more preferably 6.0 or less, and even more preferably 5.5 or less. The above upper and lower limit values ​​of the flow rate ratio a can be combined in any manner. The flow rate ratio a is preferably greater than 2.5 and equal to or less than 6.5, more preferably greater than 2.5 and equal to or less than 6.0, and even more preferably greater than 2.5 and equal to or less than 5.5.

[0041] Complexing agent flow rate When a continuous coprecipitation method using a complexing agent is used as the neutralization step, the ratio (L / min.) of the total flow rate (L / min.) of the nickel salt solution, aluminum salt solution, metal salt solution, and the mixed solution to the flow rate (L / min.) of the complexing agent supplied to the reaction tank (hereinafter, sometimes referred to as "flow rate ratio b") is preferably 6.0 or more, more preferably 6.5 or more, and even more preferably 7.0 or more. The flow rate ratio b is preferably 35 or less, more preferably 30 or less, and even more preferably 25 or less. The upper and lower limits of the flow rate ratio b can be arbitrarily combined. The flow rate ratio b is preferably 6.0-35, more preferably 6.5-30, and even more preferably 7.0-25.

[0042] Ammonium ion concentration When an ammonium ion donor is added in the neutralization step, the ammonium ion concentration in the reaction slurry in the neutralization step is preferably 2.5 g / L or more, more preferably 4 g / L or more, and even more preferably 5 g / L or more. On the other hand, the ammonium ion concentration is preferably 20 g / L or less, more preferably 16 g / L or less, and even more preferably 14 g / L or less. The upper and lower limits of the ammonium ion concentration can be arbitrarily combined. The ammonium ion concentration is preferably 2.5 to 20 g / L, more preferably 4 to 16 g / L, and even more preferably 5 to 14 g / L.

[0043] [Measurement of ammonium ion concentration] The ammonium ion concentration is determined by adding hydrochloric acid and aqueous sodium hydroxide to the reaction slurry and performing neutralization titration. When hydrochloric acid is added to the reaction slurry, ammonia and hydrochloric acid react to produce ammonium chloride. When formaldehyde is added to this ammonium chloride, hexamethylenetetramine and free acid, which are not involved in the titration, are produced. This free acid is titrated with aqueous sodium hydroxide, and the ammonium concentration is calculated from the amount of aqueous sodium hydroxide used. A titration device such as the COM-A19 (manufactured by Hiranuma Corporation) can be used.

[0044] When the neutralization step is carried out by a continuous co-precipitation method, an overflow type reaction vessel can be used for separating the reaction precipitate formed. In order to control the atmosphere inside the reaction vessel to a desired level, a predetermined gas may be passed through the reaction vessel or the reaction solution may be directly bubbled through the reaction vessel.

[0045] In the method for producing MCC, any steps may be carried out after the neutralization step described above. For example, a washing step of washing the metal composite hydroxide obtained in the neutralization step with water or the like, a drying step of drying the washed metal composite hydroxide, a sieving step of sieving the dried metal composite hydroxide, and an oxidation step of oxidizing the sieved metal composite hydroxide to obtain a metal composite oxide may be carried out. The oxidation step may involve, for example, heating the metal composite hydroxide at 300 to 700° C. for 0.1 to 10 hours in an oxygen or air atmosphere.

[0046] In the MCC production method, the dissolved Ni and Al concentrations in the reaction slurry are within the above-mentioned ranges in the neutralization step, which makes it possible to make nuclei generation in the reaction tank moderately unstable and non-uniform, and the size of the nuclei tends to vary. Therefore, when the nuclei (primary particles) aggregate to form secondary particles, voids tend to occur due to the difference in the size of the aggregated particles. Since the MCC has a plurality of voids with a relatively large pore diameter and different pore diameters from each other, the reactivity with a lithium compound can be enhanced in the method for producing a CAM described below. Therefore, a CAM with uniformly distributed lithium ions can be obtained. As a result, the cycle retention rate of the lithium secondary battery can be improved.

[0047] The MCC is preferably a compound represented by the following formula (I). Ni (1-x-y-w) Al w M1 x M2 y O z (OH) 2-α ···(I) [In formula (I), 0 < w ≦ 0.4, 0 ≦ x ≦ 0.4, 0 ≦ y ≦ 0.2, 0 < x + y + w < 1, 0 ≦ z ≦ 3, -0.5 ≦ α ≦ 2, and α - z < 2, M1 is the above element M1, and M2 is the above element M2.]

[0048] From the viewpoint of obtaining a lithium secondary battery with a high cycle retention rate, w in the formula (I) is preferably 0.01 or more, and more preferably 0.02 or more. Further, from the viewpoint of obtaining a lithium secondary battery with a high cycle retention rate, w is preferably 0.2 or less, more preferably 0.15 or less, and even more preferably 0.10 or less.

[0049] The upper and lower limit values of w can be arbitrarily combined. w is preferably 0.01 to 0.2, more preferably 0.02 to 0.15, and even more preferably 0.02 to 0.10.

[0050] From the viewpoint of obtaining a lithium secondary battery with a high cycle retention rate, x in the formula (I) is preferably 0.005 or more, and more preferably 0.01 or more. Further, x is preferably 0.2 or less, and more preferably 0.15 or less.

[0051] The upper and lower limit values of x can be arbitrarily combined. Preferably, x is from 0.005 to 0.2, and more preferably from 0.01 to 0.15.

[0052] When the element M2 is included, from the viewpoint of obtaining a lithium secondary battery with low internal resistance, in the formula (I), y preferably exceeds 0, more preferably is 0.001 or more, and even more preferably is 0.005 or more. Preferably, y is 0.08 or less, and more preferably is 0.05 or less.

[0053] The upper and lower limit values of y can be arbitrarily combined. Preferably, y exceeds 0 and is 0.08 or less, more preferably is from 0.001 to 0.08, and even more preferably is from 0.005 to 0.05.

[0054] From the viewpoint of obtaining a lithium secondary battery with a high cycle retention rate, the value of x + y + w in the formula (I) is preferably 0.3 or less, and more preferably 0.2 or less. From the viewpoint of suppressing the increase in battery resistance after repeating charge and discharge cycles, the value of x + y + w is preferably 0.01 or more, more preferably 0.02 or more, and even more preferably 0.05 or more.

[0055] The upper and lower limit values of x + y + w can be arbitrarily combined. Preferably, the formula (I) satisfies 0 < x + y + w ≤ 0.3, more preferably satisfies 0.01 ≤ x + y + w ≤ 0.3, even more preferably satisfies 0.02 ≤ x + y + w ≤ 0.2, and particularly preferably satisfies 0.05 ≤ x + y + w ≤ 0.2.

[0056] From the viewpoint of obtaining a lithium secondary battery with a high cycle retention rate, the element M2 is preferably at least one element selected from the group consisting of Ti, Mg, W, Nb, and Zr.

[0057] [Composition analysis] For the composition analysis of MCC, after dissolving the MCC powder in hydrochloric acid, it is measured using an ICP emission spectrometer. As the ICP emission spectrometer, for example, Optima 8300 manufactured by PerkinElmer Co., Ltd. can be used.

[0058] (CAM manufacturing method) The method for producing CAM of this embodiment includes a calcination step of calcining the mixture of MCC and a lithium compound, and may include a mixing step of mixing the MCC and the lithium compound before the calcination step.

[0059] [Mixing process] The lithium compound used in the mixing step may be at least one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide monohydrate, lithium oxide, lithium chloride, and lithium fluoride. Among these, at least one of lithium hydroxide, lithium hydroxide monohydrate, and lithium carbonate is preferred.

[0060] MCC and a lithium compound are mixed in consideration of the composition ratio of the final target product to obtain a mixture of MCC and a lithium compound. 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.

[0061] [Firing process] The firing temperature is preferably 400 to 1000°C, more preferably 500 to 950°C, and even more preferably 600 to 900°C. When the firing temperature is equal to or higher than the above lower limit, a CAM having a stronger crystal structure can be obtained. Furthermore, when the firing temperature is equal to or lower than the upper limit, the volatilization of lithium ions on the particle surfaces of CAM can be further reduced.

[0062] 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.

[0063] The retention time during firing is preferably 0.1 to 30 hours, more preferably 0.5 to 20 hours. When the holding time during firing is equal to or less than the upper limit, the volatilization of lithium ions is further suppressed, and the deterioration of battery performance is further suppressed. When the holding time during firing is equal to or longer than the lower limit, the growth of crystals is further promoted, and the deterioration of battery performance is further suppressed.

[0064] The firing step preferably has 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. Furthermore, it may have firing stages with different firing temperatures and firing times.

[0065] The firing atmosphere may be air, oxygen, nitrogen, argon, or a mixture of these gases, depending on the desired composition, and is preferably an oxygen-containing atmosphere.

[0066] In the firing step, the mixture may be fired in the presence of an inert flux. The inert flux may be added to an extent that the initial capacity of the battery using the CAM is not impaired, and may remain in the fired product. Examples of inert fluxes that can be used include those described in WO2019 / 177032A1.

[0067] The calcination apparatus used in the calcination step is not particularly limited, and may be, for example, a continuous calcination furnace or a fluidized bed calcination furnace. Examples of continuous calcination furnaces include tunnel kilns and roller hearth kilns. Examples of fluidized bed calcination furnaces include rotary kilns.

[0068] <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.

[0069] An example of a suitable lithium secondary battery for use with the above-mentioned 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] The shape of the electrode group 4 can be, for example, a columnar shape such that the cross section of the electrode group 4 when cut perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] <All-solid-state lithium secondary battery> The CAM can be used as a CAM for an all-solid-state lithium secondary battery.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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 .

[0085] 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.

[0086] 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).

[0087] 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.

[0088] Regarding the all-solid-state lithium secondary battery, for example, the configurations, materials, and manufacturing methods described in

[0151] to

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

[0089] In the lithium secondary battery configured as described above, since the above-mentioned CAM is used, a lithium secondary battery with a high cycle retention rate can be provided.

[0090] In order to solve the above problems, the present invention further includes the following aspects.

[11] A method for manufacturing MCC containing at least Ni and Al, comprising a neutralization step of adding at least a nickel salt solution, an aluminum salt solution, and an alkaline aqueous solution to a reaction tank to obtain a metal composite hydroxide, wherein in the neutralization step, the dissolved Ni concentration in the reaction slurry present in the reaction tank is 12 - 80 mg / L, and the dissolved Al concentration is 0.10 - 0.50 mg / L. A method for manufacturing MCC.

[12] The MCC is represented by the above formula (I). The method for manufacturing MCC according to

[11] .

[13] In the above formula (I), 0 < x + y + w ≤ 0.3. The method for manufacturing MCC according to

[12] .

[14] The ratio of the dissolved Ni concentration to the dissolved Al concentration is 70 - 760. The method for manufacturing MCC according to any one of

[11] to

[13] .

[15] In the neutralization step, an ammonium ion donor is further added, and the ammonium ion concentration in the reaction slurry is 5 - 14 g / L. The method for manufacturing MCC according to any one of

[11] to

[14] .

[16] A method for manufacturing CAM, comprising a firing step of firing a mixture of the MCC obtained by the method for manufacturing MCC according to any one of

[11] to

[15] and a lithium compound.

Examples

[0091] Hereinafter, the present invention will be described in more detail with specific examples. However, the present invention is not limited to the examples shown below.

[0092] <Composition> The composition of MCC was measured by the method described in [Composition Analysis] above.

[0093] <Dissolved Ni concentration and dissolved Al concentration> The dissolved Ni concentration and the dissolved Al concentration were measured by the method described above in [Measurement of dissolved Ni concentration and dissolved Al concentration], and the dissolved Ni / Al ratio was calculated from these values.

[0094] <Method for measuring ammonium ion concentration> The ammonium ion concentration was measured as described above in [Measurement of ammonium ion concentration].

[0095] [Method for measuring cycle retention rate] The cycle retention rate of the lithium secondary battery produced using the MCC obtained by the production method described below was measured by producing the lithium secondary battery as described above in [Method for measuring cycle retention rate].

[0096] Example 1 Water was placed in a reaction vessel equipped with a rotary stirring device having stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was added. A mixed solution 1 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. Next, the mixed solution 1, an aqueous ammonium sulfate solution as a complexing agent, and an aqueous sodium hydroxide solution were continuously added to the reaction vessel under stirring to obtain a reaction slurry 1. At this time, while maintaining the temperature of the reaction slurry 1 at 54°C, each solution was added so that the mixed solution 1 / aqueous sodium hydroxide solution (flow ratio a) was 2.59, the mixed solution 1 / aqueous ammonium sulfate solution (flow ratio b) was 7.81, the pH of the reaction slurry 1 was 12.2, and the ammonium ion concentration of the reaction slurry 1 was 8.5 g / L. The dissolved Ni concentration in the reaction slurry 1 was 15.0 mg / L, and the dissolved Al concentration was 0.18 mg / L. A reaction precipitate 1 was obtained from the reaction slurry 1. 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 125°C for 24 hours to obtain metal composite hydroxide 1. When the composition of metal composite hydroxide 1 is represented by the above formula (I), x was 0.09, y was 0, and w was 0.03. The dissolved Ni concentration, dissolved Al concentration, and dissolved Ni / Al in the reaction slurry, the pH and ammonium ion concentration of the reaction slurry, and the cycle retention rate of the lithium secondary battery produced using the metal composite hydroxide as MCC are shown in Table 1. Table 1 also shows the results for Examples 2 and 3 and Comparative Examples 1 to 3.

[0097] <Example 2> Water was placed in a reaction vessel equipped with a rotary stirring device having stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was added. Next, into the reaction tank, under stirring, the above mixed solution 1, an aqueous ammonium sulfate solution as a complexing agent, and an aqueous sodium hydroxide solution were continuously added to obtain reaction slurry 2. At this time, while maintaining the temperature of reaction slurry 2 at 70°C, each solution was added so that the above mixed solution 1 / aqueous sodium hydroxide solution (flow ratio a) was 2.67, the above mixed solution 1 / aqueous ammonium sulfate solution (flow ratio b) was 8.33, and the pH and ammonium ion concentration of reaction slurry 2 became the values ​​in Table 1. Reaction precipitate 2 was obtained from reaction slurry 2. Metal composite hydroxide 2 was obtained in the same manner as in Example 1, except that reaction precipitate 2 was used. When the composition of metal composite hydroxide 2 is represented by the above formula (I), x was 0.09, y was 0, and w was 0.03.

[0098] Example 3 Water was placed in a reaction vessel equipped with a rotary stirring device having stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was added. A mixed solution 2 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. Next, into the reaction tank, under stirring, the above mixed solution 2, an aqueous ammonium sulfate solution as a complexing agent, and an aqueous sodium hydroxide solution were continuously added to obtain reaction slurry 3. At this time, while maintaining the temperature of reaction slurry 3 at 70°C, each solution was added so that the above mixed solution 2 / aqueous sodium hydroxide solution (flow ratio a) was 2.84, the above mixed solution 2 / aqueous ammonium sulfate solution (flow ratio b) was 10.36, and the pH and ammonium ion concentration of reaction slurry 3 became the values ​​in Table 1. Reaction precipitate 3 was obtained from reaction slurry 3. Metal composite hydroxide 3 was obtained in the same manner as in Example 1, except that reaction precipitate 3 was used. When the composition of metal composite hydroxide 3 is represented by the above formula (I), x was 0.01, y was 0, and w was 0.06.

[0099] <Comparative Example 1> Water was placed in a reaction vessel equipped with a rotary stirring device having stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was added. Mixed solution 3 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. Next, into the reaction tank, under stirring, the mixed solution 3, an aqueous ammonium sulfate solution as a complexing agent, and an aqueous sodium hydroxide solution were continuously added to obtain reaction slurry 4. At this time, while maintaining the temperature of reaction slurry 4 at 70°C, each solution was added so that the mixed solution 3 / aqueous sodium hydroxide solution (flow ratio a) was 3.11, the mixed solution 3 / aqueous ammonium sulfate solution (flow ratio b) was 34.29, and the pH and ammonium ion concentration of reaction slurry 4 became the values ​​in Table 1. Reaction precipitate 4 was obtained from reaction slurry 4. Reaction precipitate 4 was washed using a 20-fold mass of aqueous sodium hydroxide solution (sodium hydroxide concentration: 5 mass%) relative to the mass of reaction precipitate 4. 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 4. When the composition of metal composite hydroxide 4 is represented by the above formula (I), x was 0.17, y was 0, and w was 0.

[0100] <Comparative Example 2> Water was placed in a reaction vessel equipped with a rotary stirring device having stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was added. A mixed solution 4 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 93.0:4.6:2.4. Next, into the reaction tank, the mixed solution 4, an aqueous ammonium sulfate solution as a complexing agent, and an aqueous sodium hydroxide solution were continuously added under stirring to obtain reaction slurry 5. At this time, while maintaining the temperature of reaction slurry 5 at 70°C, each solution was added so that the mixed solution 4 / aqueous sodium hydroxide solution (flow ratio a) was 3.41, the mixed solution 4 / aqueous ammonium sulfate solution (flow ratio b) was 5.67, and the pH and ammonium ion concentration of reaction slurry 5 became the values ​​shown in Table 1. Reaction precipitate 5 was obtained from reaction slurry 5. Metal composite hydroxide 5 was obtained in the same manner as in Example 1, except that reaction precipitate 5 was used. When the composition of metal composite hydroxide 5 is represented by the above formula (I), x was 0.046, y was 0, and w was 0.024.

[0101] <Comparative Example 3> Water was placed in a reaction vessel equipped with a rotary stirring device having stirring blades and an overflow pipe, and then an aqueous sodium hydroxide solution was added. A mixed solution 5 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. Next, into the reaction tank, the mixed solution 5, an aqueous ammonium sulfate solution as a complexing agent, and an aqueous sodium hydroxide solution were continuously added under stirring to obtain a reaction slurry 6. At this time, while maintaining the temperature of the reaction slurry 6 at 45°C, each solution was continuously added so that the mixed solution 5 / aqueous sodium hydroxide solution (flow ratio a) was 2.50, the mixed solution 5 / aqueous ammonium sulfate solution (flow ratio b) was 7.88, and the pH and ammonium ion concentration of the reaction slurry 6 became the values ​​shown in Table 1. A reaction precipitate 6 was obtained from the reaction slurry 6. Metal composite hydroxide 6 was obtained in the same manner as in Example 1, except that reaction precipitate 6 was used. When the composition of metal composite hydroxide 6 is represented by the above formula (I), x was 0.035, y was 0, and w was 0.035.

[0102] [Table 1]

[0103] As shown in Table 1, it was confirmed that the lithium secondary battery using the metal composite hydroxide produced by the production method of the example had a higher cycle retention rate than the comparative example. [Explanation of symbols]

[0104] 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 method for producing a metal composite compound containing at least Ni and Al, The method includes a neutralization step of adding at least a nickel salt solution, an aluminum salt solution, and an alkaline aqueous solution to a reaction vessel to obtain a metal composite hydroxide, In the neutralization step, the reaction slurry present in the reaction tank has a dissolved Ni concentration of 10 mg / L or more and 150 mg / L or less, and a dissolved Al concentration of more than 0 mg / L and 10 mg / L or less.

2. The method for producing a metal complex compound according to claim 1 , wherein the metal complex compound is represented by the following formula (I): <h2 style=";text-align:left;direction:ltr">Ni<h2 style=";text-align:left;direction:ltr"> （１－ｘ－ｙ－ｗ） <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> ｗ <h2 style=";text-align:left;direction:ltr"> 11<h2 style=";text-align:left;direction:ltr"> ｘ <h2 style=";text-align:left;direction:ltr"> 12<h2 style=";text-align:left;direction:ltr"> ｙ <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> ｚ <h2 style=";text-align:left;direction:ltr"> (OH)<h2 style=";text-align:left;direction:ltr"> ２－α <h2 style=";text-align:left;direction:ltr">・・・(I) [In formula (I), 0<w≦0.4, 0≦x≦0.4, 0≦y≦0.2, 0<x+y+w<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 and Mn, 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.

3. The method for producing a metal complex compound according to claim 2, wherein in formula (I), 0<x+y+w≦0.

3.

4. 3. The method for producing a metal composite compound according to claim 1, wherein the ratio of the dissolved Ni concentration to the dissolved Al concentration is 50 or more.

5. In the neutralization step, an ammonium ion donor is further added, 3. The method for producing a metal complex compound according to claim 1, wherein the reaction slurry has an ammonium ion concentration of 2.5 g / L or more and 20 g / L or less.

6. 3. A method for producing a positive electrode active material for a lithium secondary battery, comprising: a calcination step of calcining a mixture of the metal composite compound obtained by the method for producing a metal composite compound according to claim 1 or 2 and a lithium compound.

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