Method for producing positive electrode active material precursor and method for producing positive electrode active material

Abstract

A method for producing a positive electrode active material precursor, the method comprising a coprecipitation step for supplying an alkali component and a metal-containing solution containing Ni, Mn, and Mg to a reaction vessel to perform a coprecipitation reaction, wherein in the coprecipitation step, the alkali component is added under an atmosphere containing an oxidizing gas so that the pH of a reaction solution in the reaction vessel is 7.0 or higher and less than 11.0.

Description

Method for producing a positive electrode active material precursor and method for producing a positive electrode active material

[0001] This disclosure relates to a method for producing a cathode active material precursor and a method for producing a cathode active material.

[0002] The positive electrode active material used in non-aqueous electrolyte secondary batteries is produced by mixing a positive electrode active material precursor containing Ni, Mn, etc., with a lithium-containing compound and calcining the mixture. The positive electrode active material precursor is produced by supplying a metal-containing solution containing Ni, Mn, etc., and an alkaline component to a reaction vessel and carrying out a coprecipitation reaction (see, for example, Patent Document 1). Patent Document 1 discloses a technique for carrying out the above coprecipitation reaction under an inert gas atmosphere.

[0003] Japanese Patent Publication No. 2014-99299

[0004] Incidentally, metal-containing solutions containing Ni, Mn, etc., used in coprecipitation reactions may contain Mg. In particular, when using black mass, or mixed hydroxide precipitate (MHP) obtained by precipitating Ni, Mn, etc. as hydroxides from black mass or ore through a wet refining process, the metal-containing solution used in the coprecipitation reaction tends to contain Mg. If the metal-containing solution contains a large amount of Mg, the Mg content in the resulting positive electrode active material precursor increases, which may reduce the battery capacity.

[0005] Furthermore, improving the recovery rate of Mn during coprecipitation reactions is important because it reduces material waste, leading to cost reductions and a decrease in environmental impact. Therefore, there is a need for technology that reduces the Mg content in the cathode active material precursor while improving the recovery rate of Mn.

[0006] A method for producing a positive electrode active material precursor according to one aspect of the present disclosure includes a coprecipitation step in which a metal-containing solution containing Ni, Mn, and Mg and an alkaline component are supplied to a reaction vessel to carry out a coprecipitation reaction, characterized in that in the coprecipitation step, the alkaline component is added under an atmosphere containing an oxidizing gas so that the pH of the reaction solution in the reaction vessel is 7.0 or higher and less than 11.0.

[0007] Furthermore, a method for producing a positive electrode active material, which is one aspect of the present disclosure, is characterized by comprising: a precursor production step of producing a positive electrode active material precursor by the above-described method for producing a positive electrode active material precursor; a mixing step of mixing the positive electrode active material precursor with a lithium-containing compound; and a calcination step of calcining the mixture obtained in the mixing step.

[0008] According to a method for producing a positive electrode active material precursor, which is one aspect of this disclosure, the Mg content in the positive electrode active material precursor can be reduced and the recovery rate of Mn can be improved.

[0009] The present disclosure provides a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: a precursor production step of obtaining a positive electrode active material precursor by a coprecipitation reaction; a mixing step of mixing the positive electrode active material precursor with a lithium-containing compound; and a firing step of firing the mixture obtained in the mixing step. A non-aqueous electrolyte secondary battery to which the positive electrode active material produced by the production method of this embodiment is applied is obtained, for example, by housing an electrode body in which electrodes (positive electrode, negative electrode) and a separator are laminated or wound together with a non-aqueous electrolyte in an outer casing such as an outer can or laminate.

[0010] [Precursor Preparation Process] The precursor preparation process includes a coprecipitation step in which a metal-containing solution containing Ni, Mn, and Mg, along with an alkaline component, is supplied to a reaction vessel to carry out a coprecipitation reaction. The coprecipitation step yields a metal composite hydroxide containing at least Ni and Mn.

[0011] A metal-containing solution containing Ni, Mn, and Mg is, for example, a solution obtained by dissolving a mixed hydroxide precipitate (MHP) in an aqueous sulfuric acid solution, which is obtained by precipitating Ni, Mn, etc. as hydroxides from black mass, or black mass or ore, through a wet smelting process. The raw materials for the metal-containing solution are not particularly limited, as long as the solution contains Ni, Mn, and Mg.

[0012] When metal-containing solutions are prepared using black mass or MHP as raw materials, the metal-containing solutions tend to contain other elements such as Mg in addition to Ni and Mn. In particular, if the metal-containing solution contains a large amount of Mg, the Mg content in the final positive electrode active material precursor increases, which may reduce the battery capacity. Therefore, when the metal-containing solution contains Mg, there is a need for a technique to reduce the Mg content in the final positive electrode active material precursor. As will be described in detail later, the Mg content in the positive electrode active material precursor can be reduced by controlling the pH in the coprecipitation process to a predetermined range.

[0013] If the concentrations of Ni, Mn, and Mg in the metal-containing solution are M1 mol / L, M2 mol / L, and M3 mol / L, respectively, it is preferable that M1, M2, and M3 satisfy M1 + M2 + M3 ≤ 3. When M1 + M2 + M3 ≤ 3 is satisfied, each metal element becomes more easily soluble in the sulfuric acid aqueous solution. Furthermore, it is preferable that M1, M2, and M3 satisfy 0 < M3 / (M1 + M2) ≤ 0.3. In this case, when Mg is contained in the metal-containing solution, the Mg content in the final positive electrode active material precursor can be further reduced. As a result, the battery capacity can be improved. It is more preferable that M1, M2, and M3 satisfy 0.01 ≤ M3 / (M1 + M2) ≤ 0.25, and even more preferable that M1, M2, and M3 satisfy 0.03 ≤ M3 / (M1 + M2) ≤ 0.2. The concentrations of metal elements such as Ni, Mn, and Mg in metal-containing solutions can be measured using inductively coupled plasma atomic emission spectrometer (ICP-AES).

[0014] The metal-containing solution may contain metal elements other than Ni, Mn, and Mg. Examples of metal elements other than Ni, Mn, and Mg include Co, Ca, Sr, Ba, Ti, Zr, V, Nb, Cr, Mo, W, Fe, Ru, Cu, Zn, Al, Ga, Sn, and Bi. In particular, the metal-containing solution may contain Co. When Co is present in the metal-containing solution, the crystal structure of the final positive electrode active material tends to be more stable, and for example, the battery capacity tends to increase.

[0015] If the concentration of Co in the metal-containing solution is M4 mol / L, then it is preferable that M1, M2, M3, and M4 satisfy M4 / (M1+M2+M3) ≥ 0.025, and more preferably that 0.03 ≤ M4 / (M1+M2+M3) ≤ 0.2. When M4 / (M1+M2+M3) ≥ 0.025 is satisfied, an appropriate amount of Co is contained in the final positive electrode active material, and the crystal structure becomes more stable.

[0016] If the metal-containing solution is an aqueous sulfuric acid solution, then the sulfate ions (SO) contained in the metal-containing solution are present. ４ ２－ The concentration of sulfate ions (SO4) in the metal-containing solution is, for example, 4.0 mol / L or less, preferably 2.0 mol / L or less, and more preferably 1.5 mol / L or less. By setting the concentration of sulfate ions in the metal-containing solution to 2.0 mol / L or less, the Mg content in the positive electrode active material precursor can be reduced, and the recovery rate of Mn can be further improved. The lower limit of the concentration of sulfate ions in the metal-containing solution is not particularly limited, for example, 0.01 mol / L. ４ ２－ The concentration of ) is calculated by measuring the amount of S using an inductively coupled plasma atomic emission spectrometer (ICP-AES).

[0017] In the coprecipitation step, as described above, the metal-containing solution and the alkaline component are supplied to the reaction vessel to carry out the coprecipitation reaction. The alkaline component is added to adjust the pH of the reaction solution in the reaction vessel. Examples of alkaline components include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. However, the alkaline component is not limited to alkali metal hydroxides as long as it can adjust the pH of the reaction solution in the reaction vessel.

[0018] In the coprecipitation step, a complexing agent may be added. The complexing agent is not particularly limited as long as it can form a complex with metal element ions in aqueous solution, and examples include ammonium ion suppliers, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine. Examples of ammonium ion suppliers include ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride.

[0019] In the coprecipitation step, an alkaline component is added to the reaction solution in the reaction vessel so that its pH is between 7.0 and 11.0. By adding an alkaline component to the reaction solution in the reaction vessel so that its pH is between 7.0 and 11.0, the recovery rate of Mn can be improved while suppressing the precipitation of Mg. In other words, if the pH is less than 7.0, Mn will not precipitate sufficiently, and the recovery rate of Mn will decrease. Also, if the pH is 11.0 or higher, Mg precipitation is more likely to occur. Note that the pH values ​​in this specification are those measured when the liquid temperature of the reaction solution in the reaction vessel is 30°C.

[0020] From the viewpoint of suppressing Mg precipitation and further reducing the Mg content in the final positive electrode active material precursor, the pH is preferably 7.0 or higher and less than 9.2. Furthermore, from the viewpoint of improving the recovery rate of Mn, the pH is more preferably 8.0 or higher and less than 9.2. In addition, if the positive electrode active material precursor contains Co, from the viewpoint of precipitating Co, the pH is preferably 8.2 or higher and less than 9.2, and more preferably 8.5 or higher and less than 9.2.

[0021] Furthermore, in the coprecipitation process, an alkaline component is added under an atmosphere containing an oxidizing gas. This oxidizes a portion of the Mn, making it easier to precipitate even at lower pH levels. As a result, Mn precipitates even at low pH levels where Mg is less likely to precipitate, improving the recovery rate of Mn.

[0022] Examples of oxidizing gases include oxygen, ozone, and chlorine dioxide, with oxygen being preferred. When using oxygen, it is preferable to add the alkaline component in an atmosphere containing 10 mol% or more of oxygen, and more preferable to add the alkaline component in an atmosphere containing 10 mol% or more and 80 mol% or less of oxygen. By adding the alkaline component in an atmosphere containing 10 mol% or more of oxygen, Mn is appropriately oxidized, making it easier to improve the recovery rate of Mn. The alkaline component may also be added in the atmosphere.

[0023] In the coprecipitation step, the reaction vessel is neutralized while being stirred. The neutralization time for the reaction precipitate is, for example, 1 hour to 20 hours. Stirring is preferably carried out with a rotary stirring device equipped with stirring blades. Stirring makes it easier for oxidizing gases to be incorporated into the reaction solution in the reaction vessel.

[0024] Examples of reaction vessels used in the coprecipitation process include continuous reaction vessels that allow the obtained precipitate to overflow from an overflow pipe to separate it from the reaction vessel, and batch reaction vessels that do not discharge the precipitate from the system until the reaction is complete.

[0025] In the precursor preparation process, the slurry containing the precipitate obtained in the coprecipitation process is filtered and then washed with water or an alkaline aqueous solution to remove impurities (e.g., SO ４ The components are removed. Then, the solid phase and liquid phase are separated in a solid-liquid separation step, and the solid phase is washed with water. The resulting reaction product is then heat-treated at a predetermined temperature (for example, a temperature of 80°C or higher and 250°C or lower) and dried to obtain a powdered positive electrode active material precursor (Ni-containing composite hydroxide).

[0026] In the finally obtained positive electrode active material precursor, the ratio of the number of moles of Mg to the total number of moles of Ni and Mn (Mg content) is preferably 0.03 or less, and more preferably 0.02 or less. In this case, higher capacity of the battery can be achieved. As described above, the Mg content can be controlled by the pH value in the coprecipitation step, and the Mg content can be reduced as the pH value is lowered. The lower limit of the Mg content is not particularly limited, and for example, the ratio of the number of moles of Mg to the total number of moles of Ni and Mn is 0.0001. The content of metal elements such as Ni, Mn, and Mg in the positive electrode active material precursor can be measured by inductively coupled plasma optical emission spectrometry (ICP-AES).

[0027] Furthermore, in the finally obtained positive electrode active material precursor, the ratio of the number of moles of S to the total number of moles of Ni and Mn is, for example, 0 mol% or more and 30 mol% or less. In this case, the content of Mg in the positive electrode active material precursor can be reduced, and the recovery rate of Mn can be further improved. The content of S element in the positive electrode active material precursor can be measured by inductively coupled plasma optical emission spectrometry (ICP-AES).

[0028] [Mixing Step] In the mixing step, the positive electrode active material precursor obtained in the precursor production step is mixed with a lithium-containing compound. Examples of the lithium-containing compound include Li ２ CO ３ , LiOH, Li ２ O ２ , Li ２ O, LiNO ３ , LiNO ２ , Li ２ SO ４ , LiOH·H ２ O, LiH, LiF, etc. The mixing ratio of the positive electrode active material precursor and the lithium-containing compound is preferably such that the molar ratio of the total amount of metal elements in the positive electrode active material precursor to Li is in the range of 1:0.8 to 1.2, and particularly preferably 1:1.0 to 1.1.

[0029] Furthermore, in the mixing step, the positive electrode active material precursor (Ni-containing composite hydroxide) obtained in the precursor production step may be heat-treated, and the oxidized compound (Ni-containing composite oxide) may be mixed with a lithium-containing compound. The heating temperature is, for example, 300°C or higher and 700°C or lower, and may be 350°C or higher and 650°C or lower. Further, the heating time may be 0.5 hours or more and 20 hours or less, or may be 1 hour or more and 15 hours or less. Note that the heating time means the holding time at the maximum temperature. Examples of the heating atmosphere include air and oxygen.

[0030] Furthermore, in the mixing step, other compounds may be added in addition to the positive electrode active material precursor and the lithium-containing compound. Examples of the other compound include compounds containing at least one selected from the group consisting of phosphates, sulfates, oxides, hydroxides and chlorides containing at least one element selected from the group consisting of Sr, Ti, Bi, Zr, Ba, Mg, Ca, Ti, V, Al, Zr, Mo and W. Examples of the compound include SrO, SrCl ２ , Nb ２ O ５ , MgO, MgCl ２ , CaO, CaCl ２ , Ca(OH) ２ , TiO ２ , VO, V ２ O ５ , Al ２ O ３ , Al(OH) ３ , Al ２ (SO) ４、 NaAl(OH) ４ , AlPO ４ , ZrSO ４ , ZrO ２ , MoO ２ , WO ３ , WS ２ and the like. One of these compounds may be used alone, or two or more of them may be used in combination.

[0031] [Firing step] In the firing step, the mixture obtained in the mixing step is heat-treated to obtain a fired product. Firing of the mixture is performed, for example, in an oxygen stream having an oxygen concentration of 60% or more, and the flow rate of the oxygen stream is set per 10 cm of the firing furnace ３The mixture is fired at a rate of 0.1 L / min or more and 4 L / min or less per unit area, or at a rate of 1 L / min or more per kg of mixture.

[0032] The maximum temperature during firing is preferably between 650°C and 900°C, and more preferably between 700°C and 900°C. In this case, the crystallinity of the final cathode active material (lithium transition metal composite oxide) is further improved. As a result, it becomes easier to achieve higher battery capacity.

[0033] The heating rate during firing may be, for example, 0.2°C / min or more and 10.0°C / min or less, or 0.3°C / min or more and 4.5°C / min or less. The firing time (holding time) at the maximum temperature may be, for example, 1 hour or more and 10 hours or less, or 2 hours or more and 8 hours or less.

[0034] The firing conditions in the firing process may be a multi-stage firing process that includes, for example, a first firing process in which the product is fired at a temperature of 300°C or higher and 680°C or lower, and a second firing process in which the product obtained in the first firing process is fired at a maximum temperature exceeding 680°C. In the first firing process, the temperature is raised to a first set temperature of 680°C or lower at a first heating rate of 0.2°C / min or higher and 10°C / min or lower. In the second firing process, the temperature is raised to a second set temperature (maximum temperature) of 900°C or lower at a rate of 0.5°C / min or higher and 10°C / min or lower. The first heating rate and the second heating rate may be set multiple times for each temperature range, as long as they are within the ranges specified above, and there may be one or more uniform temperatures within each temperature range.

[0035] The holding time at the first set temperature in the first firing process is preferably 5 hours or less, and more preferably 3 hours or less. The holding time at the second set temperature (maximum temperature) in the second firing process is preferably 1 hour or more and 10 hours or less, and more preferably 1 hour or more and 8 hours or less.

[0036] The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to this disclosure may further include a washing step of washing the calcined product obtained in the calcination step with water, and a drying step of drying the wet powder obtained in the washing step to obtain a positive electrode active material (lithium transition metal composite oxide).

[0037] [Water Washing Process] In the water washing process, the slurry obtained by mixing the calcined material obtained in the calcination process with an aqueous solution is stirred and washed with water. Before the water washing process, unreacted lithium-containing compounds (e.g., lithium carbonate, etc.) used during mixing may remain on the particle surface of the calcined material. By performing the water washing process, unreacted lithium-containing compounds remaining on the particle surface of the positive electrode active material can be removed.

[0038] Washing is carried out by known methods. For example, the calcined material and water or an aqueous solution are placed in a reaction vessel equipped with a stirring device and stirred. In the washing process, the slurry produced in the washing process is separated into solid and liquid to obtain a cake-like wet powder. The method of solid-liquid separation is not particularly limited and is carried out by known methods. For example, a suction filter, centrifuge, or filter press can be used for solid-liquid separation.

[0039] [Drying Process] In the drying process, the wet powder obtained in the washing process is dried to obtain dry powder (lithium transition metal composite oxide). In the drying process, for example, from the viewpoint of suppressing deterioration of battery characteristics when used as a positive electrode active material, it is preferable to dry until the moisture content is 1.0% by mass or less. The drying conditions are preferably such that the drying is performed at a temperature of 100°C or higher and 300°C or lower. The drying time is preferably 0.5 hours or more.

[0040] The positive electrode active material obtained by this manufacturing method is preferably subjected to a sieving process to remove coarse particles, if necessary. This results in positive electrode active material adjusted to a predetermined particle size. Examples of equipment used for the sieving process include vibrating screens and centrifugal classifiers. Furthermore, the positive electrode active material before the sieving process may be crushed using a jet mill, roll mill, muscoloider, or the like, if necessary.

[0041] As described above, the method for producing the positive electrode active material precursor of this embodiment includes a coprecipitation step in which a metal-containing solution containing Ni, Mn, and Mg and an alkaline component are supplied to a reaction vessel to carry out a coprecipitation reaction. In the coprecipitation step, the alkaline component is added under an atmosphere containing an oxidizing gas so that the pH of the reaction solution in the reaction vessel is 7.0 or higher and less than 11.0. This makes it easier for some of the Mn to be oxidized and precipitate, while suppressing the precipitation of Mg. As a result, the recovery rate of Mn can be improved while reducing the Mg content of the positive electrode active material precursor. Thus, it is possible to realize a high-capacity battery while reducing costs and environmental impact.

[0042] The present disclosure will be further explained below with reference to examples and comparative examples, but the present disclosure is not limited to the following examples. <Example 1-1> [Preparation of positive electrode active material precursor] MHP (Sample 1) containing at least Ni hydroxide, Mn hydroxide, Co hydroxide, and Mg hydroxide was dissolved in an aqueous sulfuric acid solution to prepare a first metal-containing solution containing at least Ni, Mn, Co, and Mg. At this time, the molar ratios of Ni, Mn, Mg, and Co to the total number of moles of Ni, Mn, Mg, and Co in the first metal-containing solution were 83.7 mol%, 6.9 mol%, 6.0 mol%, and 3.4 mol%, respectively. In addition, the molar ratio of sulfate ions to the total number of moles of Ni and Mn in the first metal-containing solution was 59 mol%. Furthermore, the molar concentrations of Ni, Mn, Mg, and Co in the first metal-containing solution were 1.8 mol / L, 0.15 mol / L, 0.13 mol / L, and 0.074 mol / L, respectively. The concentration of sulfate ions in the first metal-containing solution was 1.2 mol / L.

[0043] The first metal-containing solution described above and sodium hydroxide as an alkaline component were added dropwise to a reaction vessel containing a complexing agent (ammonia water), and a coprecipitation process was carried out. During this process, the alkaline component was added under atmospheric conditions (an atmosphere containing 21 mol% oxygen) so that the pH of the reaction solution in the reaction vessel became 9.0. The precipitate obtained in the coprecipitation process was then washed, dehydrated, and dried to prepare a cathode active material precursor (Ni-containing composite hydroxide).

[0044] [Evaluation of Mn Recovery Rate] The ratio of Mn content to Ni content in the first metal-containing solution was defined as A1. The ratio of Mn content to Ni content in the prepared cathode active material precursor was defined as A2. The ratio of A2 to A1 (A2 / A1) was evaluated as the Mn recovery rate.

[0045] <Comparative Example 1-1> Except that an alkaline component was added under a nitrogen atmosphere in the coprecipitation step so that the pH of the reaction solution in the reaction vessel was 9.0, the cathode active material precursor was prepared and evaluated in the same manner as in Example 1-1.

[0046] <Comparative Example 1-2> Except that an alkaline component was added under an atmospheric environment in the coprecipitation step so that the pH of the reaction solution in the reaction vessel was 11.0, the cathode active material precursor was prepared and evaluated in the same manner as in Example 1-1.

[0047] Table 1 shows the Mn recovery rate in the positive electrode active material precursors for Examples 1-1 to 3 and Comparative Examples 1-1 and 2, and the ratio of moles of Mg to the total number of moles of Ni and Mn in the positive electrode active material precursors (Mg content).

[0048]

[0049] As shown in Table 1, the Mn recovery rate in the examples is improved compared to the Mn recovery rate in Comparative Example 1-1. This is presumed to be because the addition of an alkaline component to achieve a predetermined pH in an atmosphere containing an oxidizing gas moderately oxidizes the Mn, making it easier for Mn precipitation to occur. Furthermore, the Mg content of the positive electrode active material precursor in the examples where the pH in the coprecipitation process was 7.0 or higher and less than 11.0 is lower than the Mg content of the positive electrode active material precursor in Comparative Example 1-2 where the pH in the coprecipitation process was 11.0. This is because the precipitation of Mg was suppressed by setting the pH to less than 11.0.

[0050] Next, in order to evaluate the battery capacity of a non-aqueous electrolyte secondary battery using the positive electrode active material produced by the manufacturing method of this disclosure, the positive electrode active material precursors of Example 1-1 and Comparative Example 1-1 were mixed with a lithium-containing compound (LiOH) and calcined to produce positive electrode active materials (lithium transition metal composite oxides), respectively. Then, a positive electrode and a negative electrode using these positive electrode active materials were wound together with a separator to produce a non-aqueous electrolyte secondary battery, and the discharge capacity was evaluated. As a result, the discharge capacity of the non-aqueous electrolyte secondary battery using the positive electrode active material precursor of Example 1-1 and the discharge capacity of the non-aqueous electrolyte secondary battery using the positive electrode active material precursor of Comparative Example 1-1 were substantially the same. Therefore, it can be said that the manufacturing method of this disclosure, which involves adding an alkaline component in an atmosphere containing an oxidizing gas, can improve the recovery rate of Mn while ensuring battery capacity.

[0051] <Example 2-1> [Preparation of Cathode Active Material Precursor] A cathode active material precursor was prepared and evaluated in the same manner as in Example 1-1, except that the first metal-containing solution was replaced with the second metal-containing solution described below. Specifically, MHP (Sample 2), which contains at least Ni hydroxide, Mn hydroxide, Co hydroxide, and Mg hydroxide, was dissolved in an aqueous sulfuric acid solution to prepare a second metal-containing solution containing at least Ni, Mn, Co, and Mg. At this time, the molar ratios of Ni, Mn, Mg, and Co to the total number of moles of Ni, Mn, Mg, and Co in the second metal-containing solution were 77.4 mol%, 11.8 mol%, 4.7 mol%, and 6.1 mol%, respectively. In addition, the molar ratio of sulfate ions to the total number of moles of Ni and Mn in the second metal-containing solution was 66 mol%. Furthermore, the molar concentrations of Ni, Mn, Mg, and Co in the second metal-containing solution were 0.98 mol / L, 0.15 mol / L, 0.059 mol / L, and 0.077 mol / L, respectively. The concentration of sulfate ions in the second metal-containing solution was 0.74 mol / L.

[0052] <Comparative Example 2-1> Except that an alkaline component was added under a nitrogen atmosphere in the coprecipitation step so that the pH of the reaction solution in the reaction vessel was 9.0, the cathode active material precursor was prepared and evaluated in the same manner as in Example 2-1.

[0053] <Comparative Example 2-2> Except that an alkaline component was added under an atmospheric environment in the coprecipitation step so that the pH of the reaction solution in the reaction vessel was 11, a cathode active material precursor was prepared and evaluated in the same manner as in Example 2-1.

[0054] Table 2 shows the Mn recovery rate in the positive electrode active material precursor of Example 2-1 and Comparative Example 2-1, and the ratio of moles of Mg to the total number of moles of Ni and Mn in the positive electrode active material precursor (Mg content).

[0055]

[0056] As shown in Table 2, even when the concentrations of metal elements in the metal-containing solution differ, it can be said that by adding an alkaline component to achieve a predetermined pH in an atmosphere containing an oxidizing gas, the Mg content in the positive electrode active material precursor can be reduced and the recovery rate of Mn can be improved.

[0057] This disclosure is further illustrated by the following embodiments. Configuration 1: A method for producing a positive electrode active material precursor, comprising a coprecipitation step of supplying a metal-containing solution containing Ni, Mn, and Mg and an alkaline component to a reaction vessel to carry out a coprecipitation reaction, wherein in the coprecipitation step, the alkaline component is added under an atmosphere containing an oxidizing gas so that the pH of the reaction solution in the reaction vessel is 7.0 or higher and less than 11.0. Configuration 2: The method for producing a positive electrode active material precursor according to Configuration 1, wherein in the final positive electrode active material precursor, the ratio of the number of moles of Mg to the total number of moles of Ni and Mn is 0.03 or less. Configuration 3: The method for producing a positive electrode active material precursor according to Configuration 1 or 2, wherein, if the concentrations of Ni, Mn, and Mg in the metal-containing solution are M1 mol / L, M2 mol / L, and M3 mol / L, respectively, M1 + M2 + M3 ≤ 3 and 0 < M3 / (M1 + M2) ≤ 0.3. Configuration 4: A method for producing a positive electrode active material precursor according to any one of Configurations 1 to 3, wherein in the coprecipitation step, an alkaline component is added under an atmosphere containing an oxidizing gas so that the pH of the reaction solution in the reaction vessel is 7.0 or higher and less than 9.2. Configuration 5: A method for producing a positive electrode active material precursor according to any one of Configurations 1 to 4, wherein in the coprecipitation step, an alkaline component is added under an atmosphere containing an oxidizing gas so that the pH of the reaction solution in the reaction vessel is 8.0 or higher and less than 9.2. Configuration 6: A method for producing a positive electrode active material precursor according to any one of Configurations 1 to 5, wherein the metal-containing solution further contains Co, and when the concentrations of Ni, Mn, Mg, and Co in the metal-containing solution are M1 mol / L, M2 mol / L, M3 mol / L, and M4 mol / L, respectively, the condition M4 / (M1 + M2 + M3) ≥ 0.025 is satisfied. Configuration 7: A method for producing a positive electrode active material precursor according to any one of Configurations 1 to 6, wherein the oxidizing gas is oxygen. Configuration 8: A method for producing a positive electrode active material precursor according to Configuration 7, wherein an alkaline component is added in the coprecipitation step under an atmosphere containing 10 mol% or more of oxygen. Configuration 9: A method for producing a positive electrode active material precursor according to Configuration 7 or 8, wherein an alkaline component is added in the coprecipitation step under an atmosphere containing 10 mol% or more and 80 mol% or less of oxygen.Configuration 10: A method for producing a positive electrode active material precursor according to any one of Configurations 1 to 9, wherein the concentration of sulfate ions in the metal-containing solution is 4 mol / L or less. Configuration 11: A method for producing a positive electrode active material precursor according to any one of Configurations 1 to 10, wherein in the final positive electrode active material precursor, the ratio of moles of S to the total number of moles of Ni and Mn is 0 mol% or more and 30 mol% or less. Configuration 12: A method for producing a positive electrode active material, comprising: a precursor production step of producing a positive electrode active material precursor by the method for producing a positive electrode active material precursor according to Configurations 1 to 11; a mixing step of mixing the positive electrode active material precursor with a lithium-containing compound; and a calcination step of calcining the mixture obtained in the mixing step. Configuration 13: A method for producing a positive electrode active material according to Configuration 12, comprising a water washing step of washing the calcined product obtained in the calcination step with an aqueous solution.

Claims

1. A method for producing a positive electrode active material precursor, comprising a coprecipitation step of supplying a metal-containing solution containing Ni, Mn, and Mg and an alkaline component to a reaction vessel and carrying out a coprecipitation reaction, wherein in the coprecipitation step, the alkaline component is added under an atmosphere containing an oxidizing gas so that the pH of the reaction solution in the reaction vessel is 7.0 or higher and less than 11.

0.

2. The method for producing a positive electrode active material precursor according to claim 1, wherein the ratio of moles of Mg to the total number of moles of Ni and Mn in the final positive electrode active material precursor is 0.03 or less.

3. The method for producing a positive electrode active material precursor according to claim 1, wherein the concentrations of Ni, Mn, and Mg in the metal-containing solution are M1 mol / L, M2 mol / L, and M3 mol / L, respectively, satisfying M1 + M2 + M3 ≤ 3 and 0 < M3 / (M1 + M2) ≤ 0.

3.

4. The method for producing a cathode active material precursor according to claim 1, wherein in the coprecipitation step, an alkaline component is added under an atmosphere containing an oxidizing gas so that the pH of the reaction solution in the reaction vessel is 7.0 or higher and less than 9.

2.

5. The method for producing a cathode active material precursor according to claim 1, wherein in the coprecipitation step, an alkaline component is added under an atmosphere containing an oxidizing gas so that the pH of the reaction solution in the reaction vessel is 8.0 or higher and less than 9.

2.

6. The method for producing a positive electrode active material precursor according to claim 1, wherein the metal-containing solution further contains Co, and when the concentrations of Ni, Mn, Mg, and Co in the metal-containing solution are M1 mol / L, M2 mol / L, M3 mol / L, and M4 mol / L, respectively, the formula satisfies M4 / (M1 + M2 + M3) ≥ 0.

025.

7. The method for producing a positive electrode active material precursor according to claim 1, wherein the oxidizing gas is oxygen.

8. The method for producing a cathode active material precursor according to claim 7, wherein in the coprecipitation step, an alkaline component is added in an atmosphere containing 10 mol% or more of oxygen.

9. The method for producing a cathode active material precursor according to claim 7, wherein in the coprecipitation step, an alkaline component is added in an atmosphere containing 10 mol% or more and 80 mol% or less of oxygen.

10. The method for producing a positive electrode active material precursor according to claim 1, wherein the concentration of sulfate ions in the metal-containing solution is 4 mol / L or less.

11. The method for producing a positive electrode active material precursor according to claim 1, wherein the ratio of moles of S to the total number of moles of Ni and Mn in the final positive electrode active material precursor is 0 mol% or more and 30 mol% or less.

12. A method for producing a positive electrode active material, comprising: a precursor production step of producing a positive electrode active material precursor by the method for producing a positive electrode active material precursor described in claims 1 to 11; a mixing step of mixing the positive electrode active material precursor with a lithium-containing compound; and a calcination step of calcining the mixture obtained in the mixing step.

13. A method for producing a positive electrode active material according to claim 12, comprising a water washing step of washing the calcined product obtained in the calcination step with an aqueous solution.

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