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

Abstract

To provide a method for producing a metal complex compound that enables production of a lithium secondary battery exhibiting high rate characteristics, and a method for producing a positive electrode active material for a lithium secondary battery.SOLUTION: A method for producing a metal complex compound containing at least Ni, the method comprising a neutralization step for adding at least a nickel 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 less than 10 mg / L.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 rate characteristics.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a metal composite compound that can provide a lithium secondary battery with high rate characteristics, and a method for producing a positive electrode active material for a lithium secondary battery. [Means for solving the problem]

[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, comprising a neutralization step of adding at least a nickel salt solution and an alkaline aqueous solution to a reaction tank to obtain a metal composite hydroxide, wherein in the neutralization step, the concentration of dissolved Ni in the reaction slurry present in the reaction tank is less than 10 mg / L. [2] The method for producing a metal composite compound according to [1], wherein an ammonium ion donor is further added in the neutralization step, and the ratio of the dissolved Ni concentration to the ammonium ion concentration in the reaction slurry is 0.01 or less. [3] The method for producing a metal complex compound according to [2], wherein the ammonium ion concentration is 1.0 g / L or more and 10 g / L or less. [4] The method for producing a metal composite compound according to any one of [1] to [3], wherein the pH of the reaction slurry is 10.0 or more and 12.5 or less. [5] The method for producing a metal composite compound according to any one of [1] to [4], wherein the metal composite compound 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.] [6] In the formula (I), the production method of the metal composite compound according to [5], where 0 < x + y ≤ 0.3. [7] A production method of a cathode active material for a lithium secondary battery, comprising a firing step of firing a mixture of the metal composite compound obtained by the production method of the metal composite compound according to any one of [1] to [6] and a lithium compound. [Advantages of the Invention]

[0009] According to the present invention, a production method of a metal composite compound capable of obtaining a lithium secondary battery with high rate characteristics, and a production method of a cathode active material for a lithium secondary battery 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. [Modes 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 to nickel atoms. Similarly, "Al", "Co", "Li", etc. 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, and a numerical range including the lower limit value of 1 μm and the upper limit value of 10 μm.

[0014] [Method for Measuring Rate Characteristics] The "rate characteristics" in this specification are values measured by fabricating a lithium secondary battery by the following method and performing a discharge rate test on the lithium secondary battery under the conditions shown below.

[0015] [Fabrication 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 + M1 + M2)) is 1.02 to obtain a mixture. Bake the obtained mixture at 740 °C for 5 hours in an oxygen-containing atmosphere to obtain CAM.

[0016] [Fabrication of Positive Electrode for Lithium Secondary Battery] Prepare a paste-like positive electrode mixture by adding and kneading CAM, a conductive material (acetylene black), and a binder (PVdF) at a ratio such that the composition is CAM:conductive material:binder = 92:5:3 (mass ratio). When preparing the positive electrode mixture, use N-methyl-2-pyrrolidone as an organic solvent. Apply the obtained positive electrode mixture to an Al foil with a thickness of 20 μm serving as a current collector and perform vacuum drying 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] [Fabrication of Lithium Secondary Battery] Perform the following operations inside a glove box under an argon atmosphere. Place the positive electrode for a lithium secondary battery fabricated in "[Fabrication of Positive Electrode for Lithium Secondary Battery]" with the Al foil side facing down on the lower lid of a coin-type battery R2032 part (for example, manufactured by Takahata Shoten), and place a separator (porous polyethylene film) thereon. Inject 300 μL of an electrolytic solution here. The electrolytic solution used is a solution in which LiPF6 is dissolved at a ratio of 1.0 mol / L in a mixed solution containing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate at a volume ratio of 30:35:35. 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] <Discharge rate test> Test temperature: 25℃ Maximum charging voltage 4.3V, charging current 0.2CA, constant current constant voltage charging Minimum discharge voltage 2.5V, discharge current 0.2CA or 3CA, constant current discharge The discharge capacity when discharged at a constant current of 0.2 CA and the discharge capacity when discharged at a constant current of 3 CA were used to calculate the 3CA / 0.2CA discharge capacity ratio using the following formula, which was used as an index of rate characteristics. 3CA / 0.2CA discharge capacity ratio (%) = Discharge capacity at 3 CA / Discharge capacity at 0.2 CA × 100 (Formula) "High rate characteristics" means that the 3CA / 0.2CA discharge capacity ratio obtained by the above-mentioned discharge rate test is 66% or more. The higher this ratio, the more the discharge capacity is maintained even when a large current is passed, which is preferable in terms of battery performance.

[0019] (MCC manufacturing method) The method for producing MCC of this embodiment includes a neutralization step of adding at least a nickel salt solution and an alkaline aqueous solution to a reaction vessel to obtain a metal composite hydroxide. MCC contains at least Ni. 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 less than 10 mg / L. Here, the "reaction slurry" refers to a mixture of solids and liquids present in the reaction tank, specifically a mixture of solids including precipitates formed by the reaction of a mixed liquid containing at least a nickel salt solution and an alkaline aqueous solution, and liquid. Furthermore, the "dissolved Ni concentration" refers to the concentration of Ni dissolved in the liquid of the reaction slurry, and does not include Ni in precipitates that may be present as solids in the reaction slurry.

[0021] The concentration of dissolved Ni in the reaction slurry is preferably 8 mg / L or less, more preferably 6 mg / L or less, even more preferably 4 mg / L or less, and particularly preferably 3 mg / L or less. The lower limit of the dissolved Ni concentration in the reaction slurry is not particularly limited, and may be 0 mg / L (below the detection limit). When the dissolved Ni concentration in the reaction slurry is less than 10 mg / L, nucleation proceeds uniformly in the reaction slurry, improving the internal homogeneity of the MCC. Furthermore, when the dissolved Ni concentration in the reaction slurry is equal to or less than the above-mentioned preferred upper limit, the internal homogeneity of the primary particle size of the MCC is further improved. The CAM obtained by firing such an MCC has no uneven crystallinity within the particles and suppresses the occurrence of locally high-resistance regions, which tends to improve the rate characteristics of lithium secondary batteries.

[0022] [Measurement of dissolved Ni concentration] The concentration of dissolved Ni in the reaction slurry can be measured by removing the solid content (precipitate) from the reaction slurry, extracting the remaining liquid, and using an ICP emission spectrometer. As the ICP emission spectrometer, for example, Optima 8300 manufactured by PerkinElmer can be used.

[0023] The neutralization step is preferably carried out by a batch co-precipitation method or a continuous co-precipitation method.

[0024] 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.

[0025] In the neutralization step, a metal salt solution other than the nickel salt solution 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, Mn, and Al, 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. For example, aluminum sulfate, sodium aluminate, etc. can be used as the aluminum salt that is the solute of the aluminum salt solution. As a solvent for the nickel salt solution and the metal salt solution, for example, water can be used. In the neutralization step, the nickel salt solution and part or all of the metal salt solution may be mixed in advance to obtain a mixed solution, and then the mixed solution may be added to the reaction vessel.

[0026] 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 and one optional metal salt solution are supplied to the reaction vessel in the neutralization step, the concentrations of Ni, element M1, or element M2 contained in the nickel 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 reaction vessel in the neutralization step, the concentrations of element M1 or element M2 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, element M1, or element M2 contained in the mixed solution is preferably adjusted to 20 to 150 g / L.

[0027] 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. The complexing agent preferably contains an ammonium ion donor. The complexing agent may be used alone or in combination of two or more.

[0028] Examples of the alkaline aqueous solution include an aqueous sodium hydroxide solution and an aqueous potassium hydroxide solution.

[0029] <Method for controlling dissolved Ni concentration> The dissolved Ni 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 in the reaction slurry can be adjusted to the above-mentioned range, and the resulting MCC can improve the rate characteristics of the battery.

[0030] Temperature of reaction slurry The temperature of the reaction slurry is preferably 20 to 80°C, more preferably 30 to 75°C.

[0031] pH of reaction slurry The pH of the reaction slurry is preferably 10.0 to 12.5, more preferably 10.5 to 12.0. 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.

[0032] 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, metal salt solution, and 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") is preferably 1.0 or more, more preferably 1.2 or more, and even more preferably 1.5 or more. The flow rate ratio a is preferably 6.5 or less, more preferably 4.5 or less, and even more preferably 3.2 or less. The above upper and lower limit values ​​of the flow rate ratio a can be arbitrarily combined. The flow rate ratio a is preferably 1.0 to 6.5, more preferably 1.2 to 4.5, and even more preferably 1.5 to 3.2. When producing an MCC containing Ni and another element (element M1 or element M2), the flow ratio a is adjusted depending on the type of the other element. For example, when producing MCC containing at least Mn, the flow ratio a is preferably 1.0-6.5, more preferably 1.2-4.5, and even more preferably 1.5-3.2. When producing MCC containing elements other than Mn, the flow ratio a is preferably 1.0-3.2, more preferably 1.2-3.0, and even more preferably 1.5-2.8.

[0033] When a continuous coprecipitation method using a complexing agent is used in the neutralization step, the ratio (L / min) of the total flow rate (L / min) of the nickel salt solution, metal salt solution, and mixed solution to the flow rate (L / min) of the complexing agent supplied to the reaction vessel (hereinafter sometimes referred to as "flow rate ratio b") is preferably 2.0 or more, more preferably 3.0 or more, and even more preferably 4.0 or more. The flow rate ratio b is preferably 80.0 or less, more preferably 50.0 or less, and even more preferably 40.0 or less. The above upper and lower limit values ​​of the flow rate ratio b can be arbitrarily combined. The flow rate ratio b is preferably 2.0 to 80.0, more preferably 3.0 to 50.0, and even more preferably 4.0 to 40.0. When producing an MCC containing Ni and another element (element M1 or element M2), the flow ratio b is adjusted depending on the type of the other element. For example, when producing an MCC containing at least elements other than Al, the flow ratio b is preferably 2.0 to 80.0, more preferably 3.0 to 50.0, and even more preferably 4.0 to 40.0. When producing an MCC containing at least Al, the flow ratio b is preferably 2.0 to 10.0, more preferably 3.0 to 8.0, and even more preferably 4.0 to 6.0.

[0034] Ammonium ion concentration When an ammonium ion donor is added, the ammonium ion concentration in the reaction slurry in the neutralization step is preferably 1.0 g / L or more, more preferably 1.5 g / L or more, and even more preferably 1.8 g / L or more. On the other hand, the ammonium ion concentration is preferably 10 g / L or less, more preferably 9.5 g / L or less, and even more preferably 9.0 g / L or less. The upper and lower limits of the ammonium ion concentration can be arbitrarily combined. The ammonium ion concentration is preferably 1.0 to 10 g / L, more preferably 1.5 to 9.5 g / L, and even more preferably 1.8 to 9.0 g / L.

[0035] [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.

[0036] The relationship between the ammonium ion concentration and the dissolved Ni concentration (Ni / NH4 + ) is preferably 0.01 or less, more preferably 0.007 or less, and even more preferably 0.001 or less.

[0037] 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.

[0038] 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.

[0039] In the method for producing MCC, the dissolved Ni concentration in the reaction slurry is in the above range, and preferably Ni / NH4 + Because the temperature is within the above range, the balance between nucleation and growth in the reaction vessel is appropriate, and there is little variation in the size of the nuclei. Therefore, when the nuclei (primary particles) aggregate to form secondary particles, there is little difference in size between the aggregated particles, so they are easily packed densely, and the resulting MCC is less likely to have voids. The MCC has high internal homogeneity, which reduces the variation in crystallinity of the CAM obtained by the CAM manufacturing method described below. This allows the reaction in the CAM to proceed uniformly, which tends to reduce charge transfer resistance. Therefore, a lithium secondary battery using the CAM has a small charge transfer resistance, which makes charging and discharging easy, and the rate characteristics are likely to be improved.

[0040] MCC is preferably represented by the following formula (I): As the metal salt solution, it is preferable to use a metal salt solution necessary to obtain a compound having this composition. 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 the element M1, and M2 is the element M2.]

[0041] From the viewpoint of obtaining a lithium secondary battery with high rate characteristics, x in the formula (I) is preferably 0.01 or more, more preferably 0.02 or more, and is preferably 0.4 or less, more preferably 0.2 or less.

[0042] The upper and lower limit values of x can be arbitrarily combined. It is preferable that x is from 0.01 to 0.4, and more preferably from 0.02 to 0.2.

[0043] When containing element M2, 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 still more preferably is 0.005 or more. y is preferably 0.08 or less, and more preferably 0.05 or less.

[0044] The upper and lower limit values of y can be arbitrarily combined. It is preferable that y exceeds 0 and is 0.08 or less, more preferably from 0.001 to 0.08, and still more preferably from 0.005 to 0.05.

[0045] From the viewpoint of obtaining a lithium secondary battery with high rate characteristics, the value of x + y 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 the resistance of the battery after repeating charge and discharge cycles, the value of x + y preferably exceeds 0, more preferably is 0.01 or more, and still more preferably is 0.02 or more.

[0046] The upper and lower limit values of x + y can be arbitrarily combined. The formula (I) preferably satisfies 0 < x + y ≤ 0.3, more preferably satisfies 0.01 ≤ x + y ≤ 0.3, and still more preferably satisfies 0.02 ≤ x + y ≤ 0.2.

[0047] From the viewpoint of obtaining a lithium secondary battery with a high cycle retention rate, element M2 is preferably at least one element selected from the group consisting of Ti, Mg, W, Nb, and Zr.

[0048] [Composition analysis] For the composition analysis of MCC, after dissolving the MCC powder in hydrochloric acid, it is measured using an ICP emission spectroscopic analyzer. As the ICP emission spectrometer, for example, Optima 8300 manufactured by PerkinElmer Co., Ltd. can be used.

[0049] (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.

[0050] [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.

[0051] 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.

[0052] [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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] <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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The positive electrode 2, for example, has a positive electrode active material layer 2a containing CAM and a positive electrode current collector 2b on one surface of which the positive electrode active material layer 2a is formed. 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] <All-solid-state lithium secondary battery> The CAM can be used as a CAM for an all-solid-state lithium secondary battery.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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 .

[0076] 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.

[0077] 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).

[0078] 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.

[0079] Regarding all-solid-state lithium secondary batteries, for example, the configurations, materials, and manufacturing methods described in

[0151] to

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

[0080] In the lithium secondary battery having the above configuration, since the above-mentioned CAM is used, a lithium secondary battery with high rate characteristics can be provided.

[0081] In order to solve the above problems, the present invention further includes the following aspects.

[11] A method for producing MCC containing at least Ni, comprising a neutralization step of adding at least a nickel 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 8.0 mg / L or less.

[12] In the neutralization step, an ammonium ion donor is further added, and the dissolved Ni concentration with respect to the ammonium ion concentration in the reaction slurry is 0.001 or less. The method for producing MCC according to

[11] .

[13] The ammonium ion concentration is 1.8 - 9.0 g / L. The method for producing MCC according to

[12] .

[14] The pH of the reaction slurry is 10.5 - 12.0. The method for producing MCC according to any one of

[11] to

[13] .

[15] The MCC is represented by the above formula (I). The method for producing MCC according to any one of

[11] to

[14] .

[16] The formula (I) satisfies 0 < x + y ≤ 0.3. The method for producing MCC according to

[15] .

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

[11] to

[16] and a lithium compound.

Examples

[0082] 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.

[0083] <Composition> The composition of MCC was measured by the method described in [Composition Analysis] above.

[0084] <Dissolved Ni concentration> The dissolved Ni concentration was measured by the method described above in [Measurement of Dissolved Ni Concentration].

[0085] <Method for measuring ammonium ion concentration> The ammonium ion concentration was measured as described above in [Measurement of ammonium ion concentration].

[0086] <Method for measuring rate characteristics> The rate characteristics of the lithium secondary battery produced using the MCC obtained by the production method described below were measured by producing the lithium secondary battery as described in the above [Method for measuring rate characteristics].

[0087] 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 manganese sulfate so that the molar ratio of Ni:Co:Mn was 83.0:12.1:4.9. Next, into the reaction tank, the mixed solution 1, 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 1. At this time, while maintaining the temperature of the reaction slurry 1 at 70°C, each solution was added so that the mixed solution 1 / aqueous sodium hydroxide solution (flow ratio a) was 3.11, the mixed solution 1 / aqueous ammonium sulfate solution (flow ratio b) was 34.29, the pH of the reaction slurry 1 was 11.2, and the ammonium ion concentration of the reaction slurry 1 was 2.1 g / L. The dissolved Ni concentration in the reaction slurry 1 was 0 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 105°C for 20 hours to obtain metal composite hydroxide 1. When the composition of metal composite hydroxide 1 was expressed by the above formula (I), x was 0.17 (Co:Mn=0.121:0.049) and y was 0. In Table 1, the dissolved Ni concentration in the reaction slurry, the pH of the reaction slurry, and the ammonium ion concentration, Ni / NH4 + The values ​​of the 3CA / 0.2CA discharge capacity ratio of the lithium secondary battery fabricated using the metal composite hydroxide as MCC are also shown in Table 1. The values ​​of the 3CA / 0.2CA discharge capacity ratio of the lithium secondary battery fabricated using the metal composite hydroxide as MCC are also shown in Table 1.

[0088] <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 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 93.0:3.5:3.5. 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 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 2 / aqueous sodium hydroxide solution (flow ratio a) was 2.55, the above mixed solution 2 / aqueous ammonium sulfate solution (flow ratio b) was 5.65, 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. 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 is represented by the above formula (I), x was 0.07 (Mn:Al = 0.035:0.035) and y was 0.

[0089] 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 3 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 3, an aqueous ammonium sulfate solution as a complexing agent, and an aqueous sodium hydroxide solution were continuously added under stirring 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 mixed solution 3 / aqueous sodium hydroxide solution (flow ratio a) was 2.44, the mixed solution 3 / aqueous ammonium sulfate solution (flow ratio b) was 4.97, 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 2, except that reaction precipitate 3 was used. When the composition of metal composite hydroxide 3 is represented by the above formula (I), x was 0.07 (Co:Al=0.046:0.024) and y was 0.

[0090] Example 4 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 4 was prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, an aqueous solution of manganese sulfate, and an aqueous solution of zirconium sulfate so that the molar ratio of Ni:Co:Mn:Zr was 90.5:7.0:2.0:0.5. Next, the mixed solution 4 and the aqueous sodium hydroxide solution were continuously added to the reaction tank under stirring to obtain a reaction slurry 4. At this time, while maintaining the temperature of the reaction slurry 4 at 70°C, each solution was added so that the mixed solution 4 / aqueous sodium hydroxide solution (flow rate ratio a) was 3.33 and the pH and ammonium ion concentration of the reaction slurry 4 became the values ​​shown in Table 1. A reaction precipitate 4 was obtained from the reaction slurry 4. Metal composite hydroxide 4 was obtained in the same manner as in Example 1, except that reaction precipitate 4 was used. When the composition of metal composite hydroxide 4 is represented by the above formula (I), x was 0.09 (Co:Mn=0.07:0.02) and y was 0.005.

[0091] <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. 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 5. At this time, while maintaining the temperature of reaction slurry 5 at 70°C, each solution was added so that the mixed solution 3 / aqueous sodium hydroxide solution (flow ratio a) was 3.30, the mixed solution 3 / aqueous ammonium sulfate solution (flow ratio b) was 5.80, 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 2, except that reaction precipitate 5 was used. When the composition of metal composite hydroxide 5 is represented by the above formula (I), x was 0.07 (Co:Al=0.046:0.024) and y was 0.

[0092] <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 6 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, the mixed solution 6, 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 70°C, each solution was added so that the mixed solution 6 / aqueous sodium hydroxide solution (flow ratio a) was 2.84, the mixed solution 6 / aqueous ammonium sulfate solution (flow ratio b) was 10.36, and the pH and ammonium ion concentration of the reaction slurry 6 became the values ​​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 2, except that reaction precipitate 6 was used. When the composition of metal composite hydroxide 6 is represented by the above formula (I), x was 0.07 (Mn:Al=0.01:0.06) and y was 0.

[0093] [Table 1]

[0094] 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 higher rate characteristics than the comparative example. [Explanation of symbols]

[0095] 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, comprising: The method includes a neutralization step of adding at least a nickel salt solution and an alkaline aqueous solution to a reaction vessel to obtain a metal composite hydroxide, In the neutralization step, the concentration of dissolved Ni in the reaction slurry present in the reaction tank is less than 10 mg / L.

2. In the neutralization step, an ammonium ion donor is further added, 2. The method for producing a metal complex compound according to claim 1, wherein the ratio of the concentration of dissolved Ni to the concentration of ammonium ions in the reaction slurry is 0.01 or less.

3. The method for producing a metal complex compound according to claim 2 , wherein the ammonium ion concentration is 1.0 g / L or more and 10 g / L or less.

4. The method for producing a metal complex compound according to claim 1 or 2, wherein the pH of the reaction slurry is 10.0 or more and 12.5 or less.

5. The method for producing a metal complex compound according to claim 1 or 2, wherein the metal complex compound 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; 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.

6. The method for producing a metal complex compound according to claim 5 , wherein in formula (I), 0<x+y≦0.

3.

7. 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.

Images