Method for producing nickel sulfate and method for producing positive electrode active material for secondary battery

Abstract

To provide a method for producing nickel particles suitable for use as a raw material for a cathode active material for a secondary battery.SOLUTION: A production process of nickel particles as an example of an embodiment includes: a process of melting a nickel source to obtain a molten metal; and a process of powderizing the molten nickel contained in the molten metal to obtain nickel particles having a purity of 90% or higher by an atomization method in which a gas or a water-based medium is sprayed on the molten metal. In the production process, a metal that is more easily oxidized than nickel may be melted together with the nickel source to remove an oxide of the metal formed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This disclosure , sulfur The present invention relates to a method for producing nickel oxide and a method for producing a positive electrode active material for a secondary battery. [Background technology]

[0002] As a measure to comply with fuel economy regulations and protect the environment, there are high expectations for electric vehicles (xEVs), such as electric cars and hybrid cars, and the production volume of electric vehicles is expected to increase in the future. Accordingly, it is expected that the production volume of secondary batteries, such as lithium-ion batteries, which serve as the power source, will also increase. Meanwhile, nickel-containing composite oxides, such as nickel cobalt manganese oxide (NCM) and nickel cobalt aluminate (NCA), are used as the positive electrode active material for secondary batteries (see, for example, Patent Document 1).

[0003] A nickel-containing composite oxide can generally be produced by preparing a nickel-containing hydroxide by a crystallization method using a nickel salt such as nickel sulfate or nickel nitrate, mixing the hydroxide with a lithium compound, and firing at a high temperature. Nickel salts can be obtained by dissolving high-purity nickel bullion in sulfuric acid or the like, so it is preferable to use nickel bullion that is easily dissolved in acids such as sulfuric acid in the production of a positive electrode active material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 084346 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it is predicted that it will become difficult to obtain nickel bullion suitable as a raw material for the positive electrode active material as the production volume of secondary batteries increases in the future. The object of the present disclosure is to provide a method for producing nickel bullion (nickel particles) suitable as a raw material for the positive electrode active material for secondary batteries. [Means for solving the problem]

[0006] It is an aspect of the present disclosure. sulfuric acid Nickel Le The manufacturing method includes a step of melting a nickel source to obtain a molten metal, and a step of adding Sulfuric acid aqueous solution The molten nickel contained in the molten metal is sprayed onto the The nickel sulfate dissolved in the sulfuric acid aqueous solution and a process for obtaining the El .

[0008] A method for producing a positive electrode active material for a secondary battery according to one aspect of the present disclosure includes the steps of obtaining a nickel-containing hydroxide by a crystallization method using nickel sulfate produced by the above-described production method, and mixing the hydroxide with a lithium compound and calcining the mixed particles. Effect of the Invention

[0009] According to the method for producing nickel particles which is one aspect of the present disclosure, nickel particles suitable as a raw material for a positive electrode active material for a secondary battery can be produced. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram for explaining a method for producing nickel particles according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] As mentioned above, securing nickel ingots suitable for the raw material of the positive electrode active material is an important issue in the production of secondary batteries. Currently, high-purity nickel ingots that can be used as the raw material of the positive electrode active material mainly include briquettes made by compressing nickel particles and plate-shaped cathodes. Briquettes are preferred for the production of positive electrode active materials because they have a higher solubility in sulfuric acid than cathodes. However, the production volume of briquettes is limited, and it is predicted that they will become difficult to obtain if the production volume of secondary batteries increases in the future. Although cathodes are produced in greater quantities than briquettes, they dissolve slowly in acids such as sulfuric acid, and it is not easy to use cathodes to efficiently produce positive electrode active materials.

[0012] Therefore, there is a need for a new manufacturing technology for nickel bullion suitable as a raw material for positive electrode active materials, or a technology to process nickel cathodes to efficiently manufacture positive electrode active materials. In order to increase the dissolution rate of nickel cathodes in sulfuric acid, it is effective to increase the surface area of ​​the raw material by powdering or pelletizing it, but because cathodes are strong, if they are crushed using a crushing device, impurities from the device will be mixed in and the quality (purity) will decrease. Thus, processing cathodes is not easy.

[0013] As a result of intensive research into the above-mentioned problems, the present inventors have found that by blowing a gas or an aqueous medium onto a molten metal obtained by melting a nickel source, the nickel source can be pulverized to produce nickel particles with high purity. The nickel particles are highly soluble in acids such as sulfuric acid, and therefore are suitable as a raw material for a positive electrode active material. The above-mentioned cathode can be used as the nickel source.

[0014] Hereinafter, a method for producing nickel particles, which is one example of an embodiment of the present disclosure, and a method for producing nickel sulfate and a positive electrode active material for a secondary battery using the nickel particles will be described in detail with reference to the drawings. Fig. 1 is a diagram for explaining one example of the method for producing nickel particles.

[0015] 1, a manufacturing process of nickel particles 12, which is one example of the embodiment, includes a step of melting a nickel source 10 to obtain a molten metal 11 (hereinafter, sometimes referred to as a "first step"), and a step of powdering the molten nickel contained in the molten metal 11 by an atomization method in which a gas or an aqueous medium is sprayed onto the molten metal 11 (hereinafter, sometimes referred to as a "second step"). In this manufacturing process, a melting furnace 20 for melting the nickel source 10, a nozzle 21 for spraying a high-pressure gas or an aqueous medium onto the molten metal 11, and a chamber (not shown) for storing the powdered nickel particles 12 are used.

[0016] In this embodiment, a nickel cathode is used as the nickel source 10. The nickel cathode is obtained by using a nickel plate (seed plate) as the cathode and electrodepositing nickel on its surface. The nickel cathode is a plate-like body having a thickness of, for example, 5 mm to 15 mm, and is also called electrolytic nickel. As described above, the cathode is difficult to dissolve in an acid such as sulfuric acid, and is not suitable as a raw material for a positive electrode active material as it is. By powdering the nickel source 10 using the nickel cathode, nickel particles 12 that are high in purity and highly soluble in an acid and are suitable as a raw material for a positive electrode active material can be obtained.

[0017] However, the nickel source 10 is not limited to the nickel cathode. For example, nickel ingots with low purity such as ferro-nickel and nickel pig iron (NPI), or ores containing nickel, may be used as the nickel source 10. In addition, a raw material mainly composed of a hydrate such as crude nickel hydroxide, or a positive electrode composite material separated and concentrated from recycled secondary batteries may be used.

[0018] The nickel source 10 is melted in a melting furnace 20, and a molten metal 11 containing molten nickel is obtained. For example, an induction furnace is used as the melting furnace 20. The melting furnace 20 heats the nickel source 10 to a temperature at least equal to or higher than the melting point of nickel, and drops (flows) the molten metal 11 from a tapping port 20a provided on the bottom surface. In the first step of obtaining the molten metal 11, it is preferable to remove slag (impurities) floating in the molten metal 11 stored in the melting furnace 20. The inner wall material of the melting furnace 20 is preferably a heat-resistant ceramic material to prevent the inclusion of impurities. As the ceramic material, at least one selected from SiO2, Al2O3, MgO2, and ZrO2 is particularly preferable.

[0019] In this manufacturing process, a metal 13 that is more easily oxidized than nickel may be melted together with the nickel source 10, and the oxide of the metal 13 that is produced may be removed. The metal 13 is preferably charged into the melting furnace 20 together with the nickel source 10. By using the metal 13, the metal 13 is oxidized preferentially over nickel in the first step, and therefore the oxidation of nickel can be suppressed. The oxide of the metal 13 floats in the molten metal 11 stored in the melting furnace 20, for example, and can be separated from the molten metal 11 containing molten nickel.

[0020] For the metal 13, it is preferable to use a metal that is located below nickel in the Ellingham diagram of oxides. Specific examples include chromium (Cr), manganese (Mn), silicon (Si), titanium (Ti), aluminum (Al), magnesium (Mg), calcium (Ca), and iron (Fe). Among these, Cr, Mn, Si, Ti, Al, and Mg are preferable because they are unlikely to affect the battery characteristics and safety even if they are mixed into the battery. These function as deoxidizers, reacting with dissolved oxygen to become oxides, and suppress the oxidation of nickel.

[0021] The molten metal 11 containing molten nickel obtained in the first step flows out from the tapping port 20a and is supplied to the second step. The molten metal 11 may have a temperature equal to or higher than the melting point of nickel, but since the molten metal 11 undergoes a certain amount of cooling before being pulverized by the atomization method, it is preferable to set the temperature so that the molten metal 11 does not experience a significant increase in viscosity, etc., in consideration of the cooling. The content of molten nickel in the molten metal 11 flowing out from the tapping port 20a is, for example, substantially 100% (molten metal 11 ≒ molten nickel).

[0022] As shown in Fig. 1, a nozzle 21 for spraying gas or an aqueous medium is provided below the tapping port 20a. In general, the higher the pressure of the gas or aqueous medium sprayed from the nozzle 21, the greater the shear force acting on the molten metal 11, and the smaller the particle size of the nickel particles 12. The nozzle 21 preferably sprays the high-pressure gas or aqueous medium obliquely downward, so as to spray the gas or aqueous medium approximately uniformly over the entire outer periphery of the molten metal 11 dropping from the tapping port 20a. The nozzle 21 is, for example, arranged concentrically so as to surround the dropping molten metal 11.

[0023] In the second step, as described above, high-pressure gas or an aqueous medium is sprayed onto the molten metal 11 dropping from the tapping port 20a, thereby pulverizing the molten nickel and obtaining nickel particles 12. The method of powdering the molten metal 11 by spraying gas onto the molten metal 11 is generally called gas atomization. On the other hand, the method of using an aqueous medium is generally called water atomization. An inert gas such as argon, helium, or nitrogen is used as the gas. According to the gas atomization method, it is easier to suppress surface oxidation of the nickel particles 12 compared to the general water atomization method. The atomization method is performed, for example, in an air atmosphere or an inert gas atmosphere such as argon.

[0024] The water atomization method, in which an aqueous medium is sprayed onto the molten metal 11 to powder the molten metal 11, is more productive than the gas atomization method and easily produces nickel particles 12 with small particle diameters. The aqueous medium is, for example, high-pressure water with a water pressure of 90 MPa or more. By spraying the high-pressure water onto the molten metal 11 (molten nickel), the molten nickel is rapidly cooled and solidified, and nickel particles 12 with small particle diameters are obtained by the large shear force. According to the water atomization method, a slurry in which the nickel particles 12 are dispersed in water is obtained and stored in a chamber. The slurry is filtered to recover the nickel particles 12, which may then be subjected to treatments such as washing with water, drying, crushing, and classification.

[0025] When the water atomization method is applied in the second step, the aqueous medium may be water containing a surfactant. By using high-pressure water containing a surfactant, it is possible to suppress surface oxidation of the nickel particles 12. The concentration of the surfactant is, for example, 0.01 to 5 mass % or 0.05 to 1 mass % with respect to the mass of the aqueous medium. The surfactant may be any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant, but is preferably a nonionic surfactant.

[0026] The aqueous medium may be an aqueous sulfuric acid solution. In this case, the surface oxidation of the nickel particles 12 can be suppressed, as in the case of using a surfactant. When an aqueous sulfuric acid solution is used, for example, the nickel particles 12 are dispersed in the aqueous sulfuric acid solution, and a slurry in which the nickel particles 12 are partially dissolved is obtained. In this case, the concentration of the slurry is appropriately adjusted without performing solid-liquid separation, and the slurry can be used as nickel sulfate used in the production of a positive electrode active material. The concentration of sulfuric acid is, for example, 0.05 to 5 mol / L, or 0.1 to 1 mol / L, relative to the mass of the aqueous medium.

[0027] The entire amount of the nickel particles 12 obtained may be dissolved in the aqueous sulfuric acid solution, or only a portion of the nickel particles 12 may be dissolved as described above. If undissolved nickel particles 12 remain, an aqueous sulfuric acid solution may be added in a later step to dissolve all of the nickel particles 12. When an aqueous sulfuric acid solution is used in the water atomization method, the nickel particles 12 dissolve in the aqueous sulfuric acid solution immediately after the water atomization, and the particle size of the nickel particles 12 becomes small, so that the nozzle diameter of the outlet 20a can be increased, and productivity can be improved.

[0028] The volumetric median diameter of the nickel particles 12 is preferably 500 μm or less, particularly preferably 100 μm or less, from the viewpoint of improving solubility in acid. The volumetric median diameter of the nickel particles 12 is a particle diameter at which the volumetric integrated value is 50% in the particle size distribution measured by a laser diffraction scattering method, and is also called the 50% particle diameter (D50) or median diameter. The particle diameter of the nickel particles 12 can be controlled by the viscosity of the molten metal 11 dropping from the outlet 20a, the pressure of the gas or aqueous medium sprayed from the nozzle 21, and the like. In addition, the oxygen concentration on the particle surface of the nickel particles 12 is 10% or less, preferably 6% or less, and more preferably 3% or less.

[0029] The nickel particles 12 have a purity of 90% by mass or more. That is, the content of nickel is 90% by mass or more with respect to all components contained in the nickel particles 12. Nickel particles 12 with a purity of 90% by mass or more are suitable as a raw material for a positive electrode active material. The nickel particles 12 may contain metal elements such as Si, Ti, Fe, Mg, Al, and oxides thereof in an amount of less than 5% by mass, and may contain oxygen in an amount of less than 3% by mass. The nickel particles 12 contain, for example, 98% by mass or more of metal components. Particularly preferably, the content of nickel among the metal components contained in the nickel particles 12 is 98% by mass or more. It is preferable that the nickel particles 12 do not substantially contain lanthanum (La) as an impurity.

[0030] A positive electrode active material for a secondary battery can be manufactured using nickel particles 12 obtained by the above-mentioned manufacturing method. First, nickel sulfate is obtained by dissolving nickel particles 12 in an aqueous sulfuric acid solution. The concentration of sulfuric acid is, for example, 3 to 15 mol / L. Since nickel particles 12 are small particles with a small particle size, they have high solubility in an aqueous sulfuric acid solution, and nickel sulfate can be easily manufactured using nickel particles 12.

[0031] The manufacturing process of the positive electrode active material includes a step of obtaining a hydroxide containing nickel by a crystallization method using nickel sulfate, and a step of mixing the hydroxide with a lithium compound and firing the mixed particles. When an aqueous sulfuric acid solution is used in the water atomization method, nickel sulfate can be prepared by adding an aqueous sulfuric acid solution to a slurry of nickel particles 12 stored in a chamber without performing solid-liquid separation of the slurry. In the water atomization method using an aqueous sulfuric acid solution, nickel sulfate may be obtained by completely dissolving the nickel particles 12 in the aqueous sulfuric acid solution.

[0032] The positive electrode active material is a composite oxide containing lithium (Li) in addition to nickel (Ni) and further containing metal elements such as cobalt (Co), manganese (Mn), and aluminum (Al). The composite oxide may also contain Mg, Ti, Cr, Fe, copper (Cu), zinc (Zn), gallium (Ga), strontium (Sr), zirconium (Zr), niobium (Nb), indium (In), tin (Sn), tantalum (Ta), tungsten (W), boron (B), vanadium (V), and the like. When producing a composite oxide (NCM) containing Li, Ni, Co, and Mn, nickel cobalt manganese hydroxide is produced by a coprecipitation method using nickel sulfate, cobalt sulfate, and manganese sulfate.

[0033] The positive electrode active material is obtained by mixing at least Ni-containing hydroxide (e.g., nickel cobalt manganese hydroxide) with a lithium compound, firing the mixed particles at a temperature of 500 to 1000°C, and pulverizing and classifying the fired product. An example of the lithium compound is lithium carbonate. The D50 of the positive electrode active material is, for example, 1 μm to 30 μm, and preferably 3 μm to 10 μm. EXAMPLES

[0034] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to these examples.

[0035] < reference Example 1> A 101.6 mm square nickel cathode was placed in a high-frequency induction furnace and melted at a temperature of 1600°C. The molten nickel was allowed to flow (fall) out of the induction furnace and powdered by a water atomization method in which high-pressure water was sprayed onto the molten nickel, obtaining nickel particles with a D50 of 100 μm. The surfaces of the nickel particles were observed with a scanning electron microscope (SEM), and composition analysis was performed by energy dispersive X-ray analysis (EDS), revealing that the oxygen concentration on the particle surfaces was 6 mass%.

[0036] < reference Example 2> The other than adding 0.1% by mass of Si to the nickel cathode and removing the oxides that floated to the surface of the molten nickel as slag, reference Nickel particles having a D50 of 100 μm were obtained in the same manner as in Example 1. In this case, the oxygen concentration on the particle surface was 3 mass %.

[0037] <Example 3> In the water atomization method, except that a sulfuric acid solution (0.3 mol / L) was used instead of water, reference The treatment was carried out in the same manner as in Example 1. In this case, an aqueous sulfuric acid solution (aqueous nickel sulfate solution) in which all of the nickel particles were dissolved was obtained.

[0038] < reference Example 4> In the water atomization method, a 0.1% by mass aqueous solution of a nonionic surfactant was used instead of water. reference Nickel particles having a D50 of 100 μm were obtained in the same manner as in Example 1. In this case, the oxygen concentration on the particle surface was 1.5 mass %.

[0039] As described above, according to the above-mentioned manufacturing method, nickel particles suitable as a raw material for a positive electrode active material can be manufactured using a nickel source such as a nickel cathode, which has high purity and high solubility in acids such as sulfuric acid. In particular, by adding a metal such as Si, which is more easily oxidized than Ni, to the molten metal ( reference Example 2) Water containing a surfactant is used as the aqueous medium for the water atomization method ( reference By using Example 4), it is possible to obtain a nickel raw material with a higher purity and a lower oxygen concentration on the particle surface. In addition, when an aqueous sulfuric acid solution was used as the aqueous medium (Example 3), the entire amount of the nickel particles was dissolved in the aqueous sulfuric acid solution, and nickel sulfate was obtained. [Explanation of symbols]

[0040] 10 nickel source, 11 molten metal, 12 nickel particles, 13 metal, 20 melting furnace, 20a tapping hole, 21 nozzle

Claims

1. Melting a nickel source to obtain a molten metal; a step of obtaining nickel sulfate in which molten nickel contained in the molten metal is dissolved in the sulfuric acid aqueous solution by an atomization method of spraying the sulfuric acid aqueous solution onto the molten metal; A method for producing nickel sulfate comprising the steps of:

2. 2. The method for producing nickel sulfate according to claim 1, further comprising melting a metal that is more easily oxidized than nickel together with the nickel source, and removing the oxide of the metal that is produced.

3. A step of obtaining nickel-containing hydroxide by a crystallization method using nickel sulfate produced by the production method according to claim 1; mixing the hydroxide and the lithium compound and calcining the mixed particles; The method for producing a positive electrode active material for a secondary battery comprises the steps of:

4. A method for producing nickel sulfate as described in claim 1, wherein the nickel source is at least one selected from nickel cathode, ferro-nickel, nickel pig iron, and crude nickel hydroxide.

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