Method for recovering valuable

Abstract

To provide a method for recovering a valuable which can recover high-quality lithium carbonate having a zinc grade of less than 10 ppm, a manganese grade of less than 10 ppm and a magnesium grade of less than 10 ppm from a lithium ion secondary battery by a simple process.SOLUTION: A method for recovering a valuable that recovers lithium carbonate having a zinc grade of less than 10 ppm, a manganese grade of less than 10 ppm, and a magnesium grade of less than 10 ppm from a lithium ion secondary battery includes: a heat treatment step of heat treating the lithium ion secondary battery; a crushing / classifying step of classifying a crushed material obtained by crushing a heat-treated material; a slurry step of converting a fine particle product into a slurry; a wet magnetic separation step; an acid leaching step of adding a sulfuric acid to a magnetically unattracted material obtained by solid-liquid separation of a magnetically attracted slurry and / or a magnetically unattracted slurry, and leaching a magnetically unattracted material; a neutralization step of neutralizing an acid leachate so as to become a pH of 9.6 or more and less than 11.5; and a neutralization cake solid-liquid separation step of solid-liquid separating a liquid obtained in the neutralization step.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for recovering valuable substances from a lithium-ion secondary battery.

Background Art

[0002] A lithium-ion secondary battery is a secondary battery that is lightweight, has a high capacity, and a high electromotive force compared to conventional lead-acid batteries, nickel-cadmium secondary batteries, etc., and is used as a secondary battery for personal computers, electric vehicles, portable devices, etc. For example, valuable substances such as cobalt and nickel are used in the positive electrode of a lithium-ion secondary battery as lithium cobaltate (LiCoO2), a ternary cathode material (LiNi x Co y Mn z O2 (x + y + z = 1)), etc.

[0003]

[0004] Since the use of lithium-ion secondary batteries is expected to expand in the future, it is desirable from the viewpoint of resource recycling to recover valuable substances such as lithium from defective products generated in the manufacturing process or lithium-ion secondary batteries discarded due to the life of used devices and batteries. When recovering valuable substances such as lithium from a lithium-ion secondary battery, it is important to separate and recover various metals or impurities used in the lithium-ion secondary battery in order to increase the value of the recovered product.A method for recovering valuable substances by recovering lithium carbonate having a boron content of less than 1 ppm and a calcium content of 100 ppm or less from a lithium-ion secondary battery, comprising: a heat treatment step of obtaining a heat-treated product by heat-treating the lithium-ion secondary battery at a temperature of 660 °C or higher; a crushing and classification step of obtaining a coarse-grained product and a fine-grained product containing the valuable substances by classifying the crushed product obtained by crushing the heat-treated product; a slurrying step of immersing the fine-grained product in water to obtain a fine-grained product slurry; a wet magnetic separation step of separating the fine-grained product slurry by wet magnetic separation into an adhered material and a non-adhered material slurry; an acid leaching step of adding sulfuric acid to the non-adhered material slurry and / or the non-adhered material obtained by solid-liquid separation of the non-adhered material slurry, leaching the non-adhered material with the pH adjusted to 0 or higher and 3.5 or lower, and then performing solid-liquid separation to obtain an acid leaching solution and an acid leaching residue; a neutralization step of neutralizing the acid leaching solution with calcium hydroxide; a neutralization cake solid-liquid separation step of performing solid-liquid separation on the solution obtained in the neutralization step; a calcium carbonate crystallization step of adding CO2 to the solution obtained in the neutralization cake solid-liquid separation step; a calcium carbonate solid-liquid separation step of performing solid-liquid separation on the solution obtained in the calcium carbonate crystallization step; and a calcium adsorption and removal step of adsorbing and removing calcium with a chelating resin after the calcium carbonate solid-liquid separation step. A method for recovering valuable substances characterized by including these steps has been proposed (Patent Document 1).

[0005] Also, a method for recovering lithium from battery slag obtained by roasting lithium-ion battery waste, comprising: a leaching step of leaching the battery slag containing lithium aluminate in an acidic solution; and a neutralization step of increasing the pH of the post-leaching solution obtained in the leaching step, neutralizing it, and performing solid-liquid separation to obtain a lithium dissolution solution. A lithium recovery method including these steps has been proposed (Patent Document 2).

[0006] Also, a method for producing lithium hydroxide from lithium carbonate is proposed, which includes a hydroxylation step of reacting the lithium carbonate with calcium hydroxide in a liquid to obtain a lithium hydroxide solution, a calcium removal step of removing calcium ions in the lithium hydroxide solution using a cation exchange resin and / or a chelating resin, and a crystallization step of precipitating lithium hydroxide with the lithium hydroxide solution that has undergone the calcium removal step (Patent Document 3).

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in the prior art of the above Patent Document 1, the zinc grade in the recovered lithium carbonate may be 10 ppm or more. The battery slag obtained by roasting a lithium-ion secondary battery contains zinc presumably derived from the plating of the exterior member of the battery pack or module, magnesium contained in trace amounts in the members of the lithium-ion battery pack, module, and cell, and manganese derived from the positive electrode active material. The inventor has found that when the battery slag is acid-leached, almost all of it transfers to the acidic solution. The lithium carbonate recovered from this acidic solution contains zinc, manganese, and magnesium, and the inventor has found that this causes a decrease in specific capacity and cycle characteristics when the lithium carbonate is reused as a material for lithium-ion secondary batteries and the like. In the prior art of the above Patent Document 2, magnesium and manganese may remain in the lithium dissolution solution in the neutralization step, and the magnesium and manganese grades in the lithium carbonate recovered from the lithium dissolution solution may be 10 ppm or more. In the prior art of the above Patent Document 3, a solvent extraction step is required to remove manganese, resulting in a high-cost and complex treatment process.

[0009] An object of the present invention is to solve various conventional problems and achieve the following object. That is, the present invention aims to provide a method for recovering valuable substances that can recover high-quality lithium carbonate with a zinc grade of less than 10 ppm, a manganese grade of less than 10 ppm, and a magnesium grade of less than 10 ppm from a lithium-ion secondary battery by a simple process.

Means for Solving the Problems

[0010] Means for solving the above problems are as follows. That is, <1> A method for recovering valuable substances for recovering lithium carbonate with a zinc grade of less than 10 ppm, a manganese grade of less than 10 ppm, and a magnesium grade of less than 10 ppm from a lithium-ion secondary battery, A heat treatment step of obtaining a heat-treated product by heat-treating the lithium-ion secondary battery at a temperature of 660 ° C or higher, A crushing and classification step of classifying the crushed product obtained by crushing the heat-treated product to obtain a coarse-grained product and a fine-grained product containing the valuable substances, A slurrying step of immersing the fine-grained product in water to obtain a fine-grained product slurry, A wet magnetic separation step of separating the fine-grained product slurry by wet magnetic separation into an adhered material and a non-adhered material slurry, Sulfuric acid is added to the non-adhered material slurry and / or the non-adhered material obtained by solid-liquid separation of the non-adhered material slurry, and the non-adhered material is leached with the pH adjusted to 0 or more and 3.5 or less, followed by solid-liquid separation to obtain an acid leachate and an acid leach residue. Acid leaching step, A neutralization step of neutralizing the acid leachate to a pH of 9.6 or more and less than 11.5, A calcium hydroxide cake solid-liquid separation step of solid-liquid separating the liquid obtained in the neutralization step; A valuable substance recovery method characterized by including the following. <2> The valuable substance recovery method according to <1>, wherein in the neutralization step, the pH is adjusted to 9.6 or higher and 11.0 or lower. <3> The valuable substance recovery method according to <1>, wherein in the neutralization step, the pH is adjusted to 9.7 or higher and 10.9 or lower. <4> A calcium carbonate crystallization step of adding CO2 to the liquid obtained in the calcium hydroxide cake solid-liquid separation step; A calcium carbonate solid-liquid separation step of solid-liquid separating the liquid obtained in the calcium carbonate crystallization step; The valuable substance recovery method according to <1>, including the following. <5> The valuable substance recovery method according to <4>, wherein the addition amount of CO2 in the calcium carbonate crystallization step is 0.1 or more in terms of the molar ratio to calcium ions and 0.5 or less in terms of the molar ratio to lithium ions in the liquid obtained in the calcium hydroxide cake solid-liquid separation step. <6> The valuable substance recovery method according to <4>, including a concentration step of concentrating lithium contained in the liquid obtained after the calcium carbonate solid-liquid separation step by electrodialysis after the calcium carbonate solid-liquid separation step. <7> The valuable substance recovery method according to <4>, including a calcium adsorption and removal step of adsorbing and removing calcium with a chelating resin after the calcium carbonate solid-liquid separation step. <8> The valuable substance recovery method according to <7>, wherein the chelating resin is a chelating resin having an iminodiacetic acid group. <9> The valuable substance recovery method according to <1>, wherein calcium hydroxide is used as the neutralizing agent in the neutralization step. <10> The valuable substance recovery method according to any one of <1> to <9>, wherein both the sulfuric acid grade and the sodium grade of the lithium carbonate are 0.5% by mass or less. <11> The valuable substance recovery method according to any one of <1> to <9>, wherein the potassium grade of the lithium carbonate is 50 ppm or less. <12> The method for recovering valuable substances according to any one of <1> to <9>, wherein the boron content of the lithium carbonate is less than 1 ppm. <13> The method for recovering valuable substances according to any one of <1> to <9>, wherein the lithium-ion secondary battery is a lithium-ion battery pack or a lithium-ion battery module.

Advantages of the Invention

[0011] According to the present invention, various conventional problems can be solved, and a method for recovering valuable substances capable of recovering high-quality lithium carbonate having a zinc content of less than 10 ppm, a manganese content of less than 10 ppm, and a magnesium content of less than 10 ppm from a lithium-ion secondary battery by a simple process can be provided.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0013] (Method for Recovering Valuable Substances) The method for recovering valuable substances of the present invention includes a heat treatment step, a crushing and classification step, a slurrying step, a wet magnetic separation step, an acid leaching step, a neutralization step, and a neutralization cake solid-liquid separation step, and further includes other steps as necessary. According to the method for recovering valuable substances of the present invention, high-quality lithium carbonate having a zinc content of less than 10 ppm, a manganese content of less than 10 ppm, and a magnesium content of less than 10 ppm can be recovered from a lithium-ion secondary battery. Further, according to the method for recovering valuable substances, high-quality lithium carbonate can be efficiently recovered with a small number of steps and in a short time.

[0014] The method for recovering valuable substances of the present invention is a method for recovering valuable substances from a lithium-ion secondary battery. Here, the valuable substances mean those having value that can be a transaction target without being discarded, and examples include various metals. Examples of valuable substances in a lithium-ion secondary battery include, for example, high-quality carbon (C) concentrate, copper (Cu), aluminum (Al), lithium (Li), cobalt (Co), nickel (Ni), etc. Among these, high-quality lithium carbonate with a zinc grade of less than 10 ppm, a manganese grade of less than 10 ppm, and a magnesium grade of less than 10 ppm is applicable, and preferably, further, high-quality lithium carbonate with a boron grade of less than 1 ppm is applicable.

[0015] Regarding the zinc grade of the lithium carbonate, as long as it is less than 10 ppm, there is no particular limitation, and it can be appropriately selected according to the purpose. However, 5 ppm or less is preferable, 3 ppm or less is more preferable, and 1 ppm or less is even more preferable.

[0016] Regarding the manganese grade of the lithium carbonate, as long as it is less than 10 ppm, there is no particular limitation, and it can be appropriately selected according to the purpose. However, 5 ppm or less is preferable, 3 ppm or less is more preferable, and 1 ppm or less is even more preferable.

[0017] Regarding the magnesium grade of the lithium carbonate, as long as it is less than 10 ppm, there is no particular limitation, and it can be appropriately selected according to the purpose. However, 5 ppm or less is preferable, 3 ppm or less is more preferable, and 1 ppm or less is even more preferable.

[0018] Regarding the boron grade of the lithium carbonate, there is no particular limitation, and it can be appropriately selected according to the purpose. However, 1 ppm or less is preferable, and less than 1 ppm is more preferable.

[0019] -Lithium-ion secondary battery- The lithium-ion secondary battery is not particularly limited and can be appropriately selected according to the purpose. For example, it can be a defective lithium-ion secondary battery generated during the manufacturing process of the lithium-ion secondary battery, a lithium-ion secondary battery discarded due to a defect in the equipment in use, the life of the equipment in use, etc., a used lithium-ion secondary battery discarded due to its life, a lithium-ion battery pack, a lithium-ion battery module, and the like. Among these, a lithium-ion battery pack or a lithium-ion battery module is preferable.

[0020] It is possible to suppress the oxidation of copper and aluminum used for the current collector and the cell case, etc., and increase the recovery rate of these to the molten metal and the coarse product. As a result, the content of components other than lithium such as cobalt, nickel, copper, and aluminum in the non-magnetized material can be reduced, and the treatment efficiency of the acid leaching step and the neutralization step can be increased.

[0021] The shape, structure, size, and material of the lithium-ion secondary battery are not particularly limited and can be appropriately selected according to the purpose. The shape of the lithium-ion secondary battery is not particularly limited and can be appropriately selected according to the purpose. For example, it includes a laminate type, a cylindrical type, a button type, a coin type, a square type, a flat type, and the like. Also, the form of the lithium-ion secondary battery is not particularly limited and can be appropriately selected according to the purpose. For example, it includes a battery cell, a battery module, a battery pack, and the like. Here, a battery module means a unit in which a plurality of battery cells, which are unit cells, are connected and put together in one housing, and a battery pack means a unit in which a plurality of battery modules are put together in one housing. Also, the battery pack may be provided with a control controller or a cooling device.

[0022] Examples of lithium-ion secondary batteries include those equipped with a positive electrode, a negative electrode, a separator, an electrolytic solution containing an electrolyte and an organic solvent, and an exterior container that is a battery case for housing the positive electrode, negative electrode, separator, and electrolytic solution. Note that the lithium-ion secondary battery may be in a state where the positive electrode and negative electrode have fallen off, etc.

[0023] --Positive Electrode-- The positive electrode is not particularly limited as long as it has a positive electrode active material, and can be appropriately selected according to the purpose. The shape of the positive electrode is not particularly limited and can be appropriately selected according to the purpose. Examples include a flat plate shape and a sheet shape.

[0024] ---Positive Electrode Current Collector--- The positive electrode current collector is not particularly limited in terms of its shape, structure, size, and material, etc., and can be appropriately selected according to the purpose. Examples of the shape of the positive electrode current collector include a foil shape. Examples of the material of the positive electrode current collector include stainless steel, nickel, aluminum, copper, titanium, tantalum, etc. Among these, aluminum is preferred.

[0025] The positive electrode material is not particularly limited and can be appropriately selected according to the purpose. Examples include a positive electrode material containing at least a positive electrode active material containing lithium, and optionally a conductive agent and a binder resin. Examples of the positive electrode active material include lithium manganate (LiMn2O4) called the LMO system, lithium cobaltate (LiCoO2) called the LCO system, LiNi x Co y Mn z O2 (x + y + z = 1) called the ternary and NCM systems, LiNi x Co y Al z (x + y + z = 1), lithium iron phosphate (LiFePO4), lithium cobalt nickelate (LiCo 1 / 2 Ni 1 / 2Examples include O2), lithium titanate (Li2TiO3), etc. Also, as the positive electrode active material, these materials may be used in combination. There are no particular restrictions on the conductive agent, and it can be appropriately selected according to the purpose. For example, carbon black, graphite, carbon fiber, metal carbide, etc. can be mentioned. There are no particular restrictions on the binder resin, and it can be appropriately selected according to the purpose. For example, homopolymers or copolymers such as vinylidene fluoride, tetrafluoroethylene, acrylonitrile, ethylene oxide, etc., styrene-butadiene rubber, etc. can be mentioned.

[0026] --Negative electrode-- There are no particular restrictions on the negative electrode as long as it has a negative electrode active material containing carbon (C), and it can be appropriately selected according to the purpose. There are no particular restrictions on the shape of the negative electrode, and it can be appropriately selected according to the purpose. For example, flat plate shape, sheet shape, etc. can be mentioned.

[0027] ---Negative electrode current collector--- There are no particular restrictions on the shape, structure, size, and material of the negative electrode current collector, etc., and it can be appropriately selected according to the purpose. Examples of the shape of the negative electrode current collector include foil shape, etc. Examples of the material of the negative electrode current collector include stainless steel, nickel, aluminum, copper, titanium, tantalum, etc. Among these, copper is preferred.

[0028] There are no particular restrictions on the negative electrode active material as long as it contains carbon (C), and it can be appropriately selected according to the purpose. For example, carbon materials such as graphite, hard carbon, etc. can be mentioned. Also, as the negative electrode active material, non-carbon materials such as titanate, silicon, etc. may be used in combination with carbon.

[0029] In addition, the material of the outer container (housing) of the lithium-ion secondary battery is not particularly limited and can be appropriately selected according to the purpose. For example, aluminum, iron, stainless steel, resin (plastic), etc. can be mentioned.

[0030] Hereinafter, each step in the method for recovering valuable substances of the present invention will be described in detail.

[0031] <Heat treatment step> The heat treatment step is a step of obtaining a heat-treated product by heat-treating a lithium-ion secondary battery. The heat-treated product (roasted product) means a product obtained by heat-treating a lithium-ion secondary battery. The method for performing the heat treatment in the heat treatment step is not particularly limited and can be appropriately selected according to the purpose. For example, heat treatment can be performed by heating an object with a known roasting furnace. The roasting furnace is not particularly limited and can be appropriately selected according to the purpose. For example, batch furnaces such as rotary kilns, fluidized bed furnaces, tunnel furnaces, muffle furnaces, cupolas, stoker furnaces, etc. can be mentioned.

[0032] The atmosphere used for the heat treatment is not particularly limited and can be appropriately selected according to the purpose. For example, an air atmosphere, an inert atmosphere, a reducing atmosphere, a low-oxygen atmosphere, etc. can be mentioned. The air atmosphere (air atmosphere) means an atmosphere using air with about 21% by volume of oxygen and about 78% by volume of nitrogen. The inert atmosphere can be exemplified by an atmosphere composed of nitrogen or argon. The reducing atmosphere means, for example, an atmosphere containing CO, H2, H2S, SO2, etc. in an inert atmosphere such as nitrogen or argon. The low-oxygen atmosphere means an atmosphere with an oxygen partial pressure of 11% or less.

[0033] <<Heat treatment conditions>> The conditions for heat-treating (heating) the object (heat treatment conditions) are not particularly limited as long as each component of the object can be separated and made into a state where it can be crushed in the crushing and classification steps described later, and can be appropriately selected according to the purpose. Here, examples of the heat treatment conditions include the heat treatment temperature, the heat treatment time, and the like.

[0034] The heat treatment temperature means the temperature of the lithium-ion secondary battery that is the object during heat treatment. The heat treatment temperature can be measured by inserting a thermometer such as a couple or a thermistor into the object during heat treatment.

[0035] The temperature in the heat treatment (heat treatment temperature) is not particularly limited as long as it is 660°C or higher, and can be appropriately selected according to the purpose. However, it is preferably 700°C or higher and 1,080°C or lower, and more preferably 750°C or higher and 900°C or lower. By setting the heat treatment temperature to 660°C or higher, the aluminum (Al) member used for the outer container or the like can be melted and separated from other lithium-ion secondary battery components. On the other hand, by embrittling the foil-like Al used for the positive electrode current collector and recovering it as a fine-grained product in the subsequent crushing step and classification step, the Al in this fine-grained product can be used for boron removal in the neutralization step. Further, by setting the heat treatment temperature to 660°C or higher, reduction of cobalt oxide and nickel oxide contained in the positive electrode active material to metal occurs. In addition, these metals can be grown to a particle size at which they are easily magnetically attracted in the subsequent magnetic separation. This increase in particle size is more likely to occur with heat treatment at higher temperatures. Also, by decomposing Li in the positive electrode active material into LiF, Li2O, Li2CO3, etc., the loss of lithium to the magnetically attracted side (when the undecomposed positive electrode active material is involved and recovered in the cobalt oxide) can be reduced.

[0036] In addition, for the outer container of the lithium-ion secondary battery, it is preferable to use a material having a melting point higher than the heat treatment temperature. When a material having a melting point lower than the heat treatment temperature is used for the outer container of a lithium ion secondary battery, it is preferable to perform heat treatment in a low oxygen atmosphere with an oxygen concentration of 11% by volume or less, or in an atmosphere where the oxygen concentration is 11% by volume or less at least inside the lithium ion secondary battery during baking (particularly, the positive electrode current collector and the negative electrode current collector disposed inside the outer container of the lithium ion secondary battery).

[0037] Also, as a method for realizing a low oxygen atmosphere, for example, the lithium ion secondary battery, the positive electrode, or the negative electrode may be housed in an oxygen shielding container and heat treated. The material of the oxygen shielding container is not particularly limited as long as it has a melting point equal to or higher than the heat treatment temperature, and can be appropriately selected according to the purpose. For example, when the heat treatment temperature is 800 °C, iron, stainless steel, etc. having a melting point higher than this heat treatment temperature can be mentioned. In order to release the gas pressure due to the combustion of the electrolytic solution in the lithium ion secondary battery or the laminate, it is preferable to provide an opening in the oxygen shielding container. The opening area of the opening is preferably provided so as to be 12.5% or less with respect to the surface area of the outer container in which the opening is provided. The opening area of the opening is more preferably 6.3% or less with respect to the surface area of the outer container in which the opening is provided. The opening is not particularly limited with respect to its shape, size, formation location, etc., and can be appropriately selected according to the purpose. By heat treating with the lithium ion secondary battery housed in the oxygen shielding container, the carbon of the negative electrode active material can be left without being burned, and the carbon recovery rate can be improved.

[0038] The time for heat-treating the lithium-ion secondary battery (heat-treatment time) is not particularly limited and can be appropriately selected according to the purpose, but is preferably 1 minute or more and 10 hours or less, more preferably 1 minute or more and 6 hours or less, and particularly preferably 1 minute or more and 4 hours or less. The heat-treatment time only needs to be the heat-treatment time for the compound containing lithium to reach the desired temperature. However, by gently increasing the heating rate, the decomposition of the positive electrode active material can be promoted, the loss of lithium to the magnetically attached material side can be reduced, and in addition, the amount of acid used in the acid leaching of the non-magnetically attached material described later can be reduced. Also, after the temperature is raised, the time for maintaining the temperature can be short. If the heat-treatment time exceeds 5 hours, losses due to carbon combustion occur, metals such as copper recovered as coarse-grained products in the classification process are oxidized, the quality as valuable substances deteriorates, and the fuel and power costs for heat treatment increase. Therefore, the heat-treatment time is preferably 5 hours or less. When the heat-treatment time is the above-preferred time, it is advantageous from the viewpoints of the cost and productivity of the heat treatment.

[0039] In addition, in the method for recovering valuable substances of the present invention, by setting the heat-treatment temperature to 660 °C or higher, aluminum derived from the exterior container can be melted and separated. In addition, in the method for recovering valuable substances of the present invention, by the heat-treatment step, the positive electrode active material is sufficiently decomposed into a form of lithium carbonate and lithium oxide that are easily soluble in water, and the leaching rate in water increases. On the other hand, aluminum contained in the exterior container, the positive electrode current collector, etc. reacts to form lithium aluminate (LiAlO2) that is hardly soluble in water. Even in this case, since lithium aluminate can be dissolved in the acid leaching step, lithium (Li) can be recovered at a high recovery rate.

[0040] <Crushing and classification step (crushing treatment)> The crushing and classification step (crushing treatment) includes a treatment of obtaining crushed materials by crushing the heat-treated material (the lithium-ion secondary battery heat-treated). The crushing treatment is not particularly limited as long as the heat-treated material (roasted material) can be crushed to obtain crushed materials, and can be appropriately selected according to the purpose. Also, the crushed material means the material obtained by crushing the heat-treated material. As the crushing treatment, for example, it is preferable to obtain crushed materials by crushing the heat-treated product by impact. Further, when the outer container of the lithium-ion secondary battery does not melt during the heat treatment, it is more preferable to perform preliminary crushing by cutting the heat-treated product with a cutting machine before applying an impact to the heat-treated product. The crushing treatment may be performed wet. In this case, it is possible to prevent losses due to scattering of the positive and negative electrode active materials such as carbon, cobalt, and nickel during crushing, and it is possible to reduce the dust collection device for preventing this loss. Further, all the water-soluble lithium in the heat-treated product can be recovered in water at the time of the crushing treatment.

[0041] Examples of the method of performing crushing by impact include a method of throwing the heat-treated product onto a rotating striking plate and hitting it against a collision plate to apply an impact, a method of hitting the heat-treated product with a rotating beater, etc., and for example, it can be performed by a hammer crusher or the like. Further, as a method of performing crushing by impact, for example, a method of hitting the heat-treated product with balls such as ceramics may be used, and this method can be performed by a ball mill or the like. Further, crushing by impact can also be performed using, for example, a twin-shaft crusher with a blade width and blade length for performing crushing by compression. Furthermore, examples of the method of performing crushing by impact include a method of hitting the heat-treated product with two rotated chains to apply an impact, etc., and for example, it can be performed by a chain mill or the like.

[0042] By crushing the heat-treated product by impact, the crushing of the positive electrode current collector (for example, aluminum (Al)) is promoted, but the negative electrode current collector (for example, copper (Cu)) whose form has not changed significantly exists in the form of a foil or the like. Therefore, in the crushing treatment, the negative electrode current collector is only cut, so that in the classification treatment described later, it is possible to obtain crushed materials in a state where the valuable substances derived from the positive electrode current collector (for example, aluminum) and the valuable substances derived from the negative electrode current collector (for example, copper (Cu)) can be efficiently separated.

[0043] The crushing time in the crushing process is not particularly limited and can be appropriately selected according to the purpose. However, as the crushing time per 1 kg of the lithium-ion secondary battery, it is preferably 1 second or more and 30 minutes or less, more preferably 2 seconds or more and 10 minutes or less, and particularly preferably 3 seconds or more and 5 minutes or less.

[0044] <Crushing and Classification Process (Classification Treatment)> The above-mentioned crushing and classification process (classification treatment) includes a process of obtaining a coarse-grained product and a fine-grained product containing valuable substances by classifying the crushed material. The above-mentioned classification treatment is not particularly limited as long as the crushed material can be classified to obtain a coarse-grained product (oversize) and a fine-grained product (undersize), and can be appropriately selected according to the purpose.

[0045] The classification method is not particularly limited and can be appropriately selected according to the purpose. For example, it can be carried out using a vibrating screen, a multi-stage vibrating screen, a cyclone, a standard screen of JIS Z8801, etc. By classification, copper (Cu), iron (Fe), etc. can be separated into the coarse-grained product, and lithium, cobalt, nickel, or carbon can be concentrated into the fine-grained product. The above-mentioned classification treatment may be carried out wet. In this case, it is possible to prevent losses due to the scattering of the positive and negative electrode active materials such as carbon, cobalt, and nickel during crushing, and it is possible to reduce the dust collection device for preventing this loss. The crushed material may be humidified before classification for the purpose of preventing scattering. As the humidification method, spraying water in a mist form may be used. By doing so, it is possible to prevent the scattering of carbon, cobalt, and nickel when watering the crushed material.

[0046] The classification granularity (classification point, sieve aperture) is not particularly limited and can be appropriately selected according to the purpose. By classification, copper (Cu), iron (Fe), aluminum (Al), etc. are separated into the coarse-grained product, and carbon (C), lithium (Li), cobalt (Co), nickel (Ni), manganese (Mn), etc. are concentrated into the fine-grained product. When the purpose is to do so, the classification granularity is preferably 0.15 mm or more and 2.4 mm or less, and more preferably 0.3 mm or more and 1.7 mm or less. When the classification granularity is 2.4 mm or less, the mixing of copper (Cu), iron (Fe), aluminum (Al), etc. into the fine-grained product can be suppressed. When the classification granularity is 0.15 mm or more, the mixing of carbon (C), lithium (Li), cobalt (Co), nickel (Ni), manganese (Mn), etc. into the coarse-grained product can be suppressed.

[0047] Also, when using a sieve as the classification method, by placing, for example, stainless steel balls or alumina balls on the sieve as a crushing acceleration material and performing classification, small crushed materials adhering to large crushed materials can be separated from the large crushed materials, and the large crushed materials and small crushed materials can be separated more efficiently. By doing so, the grade of the metal to be recovered can be further improved. Note that the crushing process and the classification process can also be carried out simultaneously. For example, it may be carried out as a crushing and classification process (crushing and classification) in which the heat-treated product obtained in the heat treatment step is crushed while classifying the crushed product into a coarse-grained product and a fine-grained product.

[0048] Note that the classification of the coarse-grained product and the fine-grained product may be repeated multiple times. By this repeated classification, the impurity grade of each product can be further reduced. For example, from the perspective of increasing the grades of cobalt (Co) and nickel (Ni) in the fine-grained product, for example, by performing two-stage screening at each classification point of more than 1.2 mm and 0.3 mm or more and 1.2 mm or less, in the first stage, components of a lithium-ion secondary battery with an average particle size larger than that of cobalt and nickel such as copper or iron can be separated onto the screen, and cobalt and nickel with insufficient separation from copper of the negative electrode current collector and aluminum of the positive electrode current collector are recovered onto the screen of the second stage, and cobalt, nickel, and carbon are recovered under the screen of the second stage. The material on the screen of this second stage can be crushed again to promote the separation of cobalt and nickel from aluminum, and then screened again to recover cobalt and nickel under the screen.

[0049] <Slurrying step> The slurrying step is a step of immersing the fine-grained product obtained in the crushing and classification step in water to obtain a fine-grained product slurry. The slurrying step is not particularly limited as long as it is a step capable of obtaining a slurry by immersing the fine-grained product recovered in the crushing and classification step in water, and can be appropriately selected according to the purpose. When the crushing step or the classification step is performed wet, the crushing step or the classification step may be used as the slurrying step.

[0050] The water for leaching the fine-grained product is not particularly limited and can be appropriately selected according to the purpose. Examples include industrial water, tap water, ion-exchanged water, ultrafiltration water, reverse osmosis permeate, pure water such as distilled water, and ultrapure water. Among these, it is preferable to use ion-exchanged water because the manufacturing cost is relatively low and the concentration of potassium, which is an impurity in lithium carbonate, is low.

[0051] Here, the fine particle slurrying method in the slurrying step is not particularly limited and can be appropriately selected according to the purpose. For example, there are methods such as simply putting the fine particle product into water, putting the fine particle product into water and stirring, putting the fine particle product into water and gently stirring while applying ultrasonic waves, adding water to the fine particle product, spraying water onto the fine particle product in a mist form to adjust the humidity and then putting it into water, and the like. The method of putting the fine particle product into water and stirring is preferred, and the method of spraying water onto the fine particle product in a mist form to adjust the humidity and then putting it into water is more preferred. By this method, magnetic separation can be performed while preventing dust generation from the fine particle product.

[0052] The solid-liquid ratio in the slurrying step is not particularly limited and can be appropriately selected according to the purpose, but it is preferably 5% or more and 67% or less, and more preferably 10% or more and 40% or less. When the solid-liquid ratio is less than 5%, the concentration of lithium dissolved in the leachate decreases, and the lithium recovery rate and concentration efficiency are likely to decrease. When the solid-liquid ratio exceeds 67%, the leaching rate of lithium into water may decrease. When the slurry is sent to the next step without dilution, problems such as pipe blockage may occur. Also, when the slurry is supplied to the wet magnetic separation step described below, the recovery rate of cobalt and nickel to the magnetized product and the recovery rate of carbon to the non-magnetized product may decrease (that is, the separation performance of cobalt and nickel from carbon may decrease).

[0053] The stirring speed of the slurry in the slurrying step is not particularly limited and can be appropriately selected according to the purpose. For example, it can be set to 400 rpm. The stirring time in the slurrying step is not particularly limited and can be appropriately selected according to the purpose. For example, it can be set to 1 hour.

[0054] <Wet Magnetic Separation Step> The wet magnetic separation step is a step of separating the fine particle product slurry obtained in the slurrying step into a magnetized product and a non-magnetized product slurry by wet magnetic separation. Note that the "non-magnetized product slurry" means a suspension containing non-magnetized products. The wet magnetic separation process is not particularly limited as long as it can separate the fine-grained product slurry into an adhered material and a non-adhered material slurry by wet magnetic separation, and can be appropriately selected according to the purpose. In the present invention, by separating cobalt and nickel from the non-adhered material slurry as the adhered material, the amounts of acid and neutralizing agent consumed by cobalt and nickel during acid leaching can be reduced.

[0055] The adhered material has a higher cobalt and nickel grade and a lower impurity grade compared to the fine-grained product. Therefore, the cobalt and nickel obtained in the wet magnetic separation process do not require additional concentration processes for Co and Ni such as acid leaching, neutralization, and solvent extraction, and can be directly used as raw materials (for example, cobalt sulfate, nickel sulfate, etc.) for obtaining manufacturing materials for secondary batteries, or as smelting raw materials for cobalt and nickel. Also, lithium in the adhered material may be recovered as lithium carbonate or lithium hydroxide in the process of obtaining these manufacturing materials for secondary batteries, or in the process of obtaining smelting raw materials for cobalt and nickel. By recovering lithium in the adhered material, 10 mass% or more of the lithium contained in the lithium-ion secondary battery can be recovered as lithium carbonate or lithium hydroxide.

[0056] Here, the adhered material means something that can generate an attractive force with the magnetic force source (for example, a magnet, an electromagnet, etc.) that generates a magnetic force (magnetic field), and can be adsorbed to the magnetic force source side. Examples of the adhered material include ferromagnetic metals. Examples of ferromagnetic metals include iron (Fe), nickel (Ni), cobalt (Co), etc. The non-adhered material means something that is not adsorbed to the magnetic force source side by the magnetic force generated by the magnetic force source. The non-adhered material is not particularly limited and can be selected according to the purpose. Also, examples of the non-adhered material of metal include paramagnetic or semi-magnetic metals. Examples of paramagnetic or semi-magnetic metals include aluminum (Al), manganese (Mn), gold (Au), silver (Ag), copper (Cu), etc.

[0057] The wet magnetic separation process is not particularly limited and can be carried out using a known wet magnetic separator (magnetic separator) or the like. The wet magnetic separator that can be used in the present invention is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include a drum type magnetic separator and a high gradient magnetic separator.

[0058] The conditions for wet magnetic separation when performing the wet magnetic separation process are not particularly limited and can be appropriately selected according to the purpose.

[0059] In the wet magnetic separation process, for example, cobalt (Co), nickel (Ni), manganese (Mn) integrated with cobalt, etc. are recovered as magnetic adherents. Here, when magnetic separating the fine particle product obtained in the crushing and classification process, for example, when performing magnetic separation in a dry state, aggregation of particles occurs due to the adhering moisture between the particles, and the metal particles derived from the negative electrode current collector and the fine particle product may not be able to sufficiently separate the fine particles of the negative electrode active material contained in an amount of 10% or more and cobalt and nickel particles. Therefore, in the present invention, in the wet magnetic separation process, it is preferable to separate the substance derived from the negative electrode active material and the metal derived from the negative electrode current collector into a non-magnetic adherent slurry and recover cobalt and nickel as magnetic adherents.

[0060] The solid-liquid ratio of the slurry supplied for wet magnetic separation is not particularly limited and can be appropriately selected according to the purpose, but is preferably 5% or more and 67% or less, and more preferably 10% or more and 40% or less. If the solid-liquid ratio is less than 5%, the recovery rate of cobalt and nickel as magnetic adherents in the wet magnetic separator may decrease. If the solid-liquid ratio exceeds 67%, problems such as clogging of the pump during slurry supply are likely to occur, and the separation performance of cobalt and nickel (magnetic adherents) and non-magnetic adherents such as carbon may decrease. The slurry may be supplied as it is the fine particle product slurry obtained in the slurrying process, or the fine particle product slurry obtained in the slurrying process may be concentrated or diluted by solid-liquid separation such as sedimentation separation to adjust the solid-liquid ratio. Also, water may be added to the fine particle product slurry for dilution to adjust the solid-liquid ratio.

[0061] The method for supplying the slurry is not particularly limited and can be appropriately selected according to the purpose. However, it may be supplied by a pump while stirring the slurry in the tank. The magnetic field strength of the magnetic separator used in wet magnetic separation is preferably 500 G or more and 20,000 G or less, more preferably 1,000 G or more and 10,000 G or less, and particularly preferably 1,500 G or more and 8,000 G or less. If the magnetic field strength is less than 500 G, it is difficult to magnetically attach fine cobalt and nickel particles, and the recovery rate of the magnetic deposits of cobalt and nickel may easily decrease. On the other hand, if the magnetic field strength exceeds 20,000 G, the recovery rate of impurities other than cobalt and nickel to the magnetic deposits increases, and the cobalt and nickel grades in the magnetic deposits may decrease.

[0062] Since the magnetic deposits recovered in the wet magnetic separation process contain moisture, the moisture may be removed by solid-liquid separation using filter paper, a filter press, a centrifuge, etc., air drying, or heat drying with a dryer. The obtained magnetic deposits may be subjected to solid-liquid separation after being washed with water. In this case, fluorine that could not be removed from the magnetic deposits in the slurrying process can be reduced to, for example, less than 1%. This water washing can be carried out, for example, by pouring water into the filter chamber containing the magnetic deposits in the filter press when using a filter press as the solid-liquid separation device. As the weight of water used for water washing, it is preferable to pass 0.1 kg or more of water per 1 kg of the acid leaching residue, and particularly preferably to pass 1 kg or more of water. Also, since lithium is leached into the passed water, it may be recovered.

[0063] The wet magnetic separation process may perform wet magnetic separation multiple times (in multiple stages). For example, by performing a second-stage wet magnetic separation (purification) on the magnetic adherends recovered in the first-stage wet magnetic separation process, the cobalt (Co) grade of the magnetic adherends can be improved. In this case, the conditions of the second-stage wet magnetic separation may be different from those of the first stage, and by setting conditions that make it more difficult to recover magnetic adherends than in the first-stage wet magnetic separation (for example, low magnetic field intensity, high magnetic separator drum rotation speed, high feed rate, etc.), the cobalt (Co) grade of the magnetic adherends recovered in the second-stage wet magnetic separation can be made higher than the cobalt (Co) grade of the magnetic adherends recovered in the first-stage wet magnetic separation, and the recovery rate of carbon (C) recovered as non-magnetic adherend slurry can be improved compared to the case of performing a single-stage wet magnetic separation. Also, as another example, by performing a second-stage wet magnetic separation (cleaning separation) on the non-magnetic adherend slurry recovered in the first-stage wet magnetic separation process, the cobalt (Co) grade of the non-magnetic adherend slurry can be reduced. In this case, the conditions of the second-stage wet magnetic separation may be different from those of the first stage, and by setting conditions that make it easier to recover magnetic adherends than in the first-stage wet magnetic separation (for example, high magnetic field intensity, low magnetic separator drum rotation speed, low feed rate, etc.), the cobalt grade of the non-magnetic adherend slurry recovered in the second-stage wet magnetic separation can be reduced compared to the cobalt grade recovered in the first-stage wet magnetic separation, and the recovery rate of cobalt recovered as magnetic adherends can be improved compared to the case of performing a single-stage wet magnetic separation. Water may be added to the non-magnetic adherend slurry obtained by wet magnetic separation. By adjusting the lithium (Li) concentration, as shown in the neutralization process described later, the loss of lithium to the neutralization residue can be prevented.

[0064] <Acid Leaching Process> The acid leaching process is a process in which sulfuric acid is added to the non-magnetic adherend slurry and / or the non-magnetic adherends obtained by solid-liquid separation of the non-magnetic adherend slurry, the pH is set to 0 or more and 3.5 or less to leach the non-magnetic adherends, and then solid-liquid separation is performed to obtain an acid leaching solution and acid leaching residue. The obtained acid leaching solution contains dissolved water-soluble lithium such as lithium carbonate, lithium fluoride, and lithium oxide, as well as lithium derived from hardly water-soluble LiAlO2 (lithium aluminate). On the other hand, since carbon (C) is concentrated in high grade in the obtained acid leaching residue, it can be recovered and utilized as a carbon (C) concentrate. For the acid leaching solution and the acid leaching residue (carbon concentrate), a method of solid-liquid separation using, for example, filter paper, a filter press, or a centrifuge is preferable.

[0065] In the acid leaching step, sulfuric acid is used as the acidic solution. The concentration of the sulfuric acid to be added is preferably 5% by mass or more and 90% by mass or less, and more preferably 10% by mass or more and 80% by mass or less. By using sulfuric acid of such a concentration, heat generation and bumping of the acidic solution in the acid leaching step (including hydrofluoric acid derived from fluorine in the electrolyte of the lithium ion secondary battery in addition to sulfuric acid derived from the added sulfuric acid), and deterioration of the tank used for leaching can be suppressed.

[0066] As long as the pH of the acidic solution used in the acid leaching step is 0 or more and 3.5 or less, there is no particular limitation, and it can be appropriately selected according to the purpose. However, 0 or more and 3 or less is more preferable, 1 or more and 3 or less is even more preferable, and 1.5 or more and 2.5 or less is particularly preferable. When the pH exceeds 3.5, lithium aluminate in the filter residue is not effectively dissolved. Here, the pH of the acidic solution means the pH at the end of the acid leaching step. When the pH of the acidic solution is 0 or more and 3.5 or less, 80% or more of the lithium in the non-magnetically attached material can be leached, and a carbon concentrate (acid leaching residue) with a carbon grade of 80% or more can be obtained. When the pH is 0 or more and 3 or less, it is preferable because the lithium can be leached while suppressing the amount of acid added without reducing the acid leaching rate of lithium compared to the case of pH 0. When the pH is 1.5 or more and 2.5 or less, the lithium can be leached without reducing the acid leaching rate of lithium compared to the case of pH 0, and the leaching of copper contained in the non-magnetically attached material slurry can be suppressed, and an acid leaching solution with a lower impurity concentration can be obtained, which is particularly suitable. Incidentally, copper contained in the acid leaching residue (carbon concentrate) may not cause problems when used as a smelting raw material (reducing agent), and by performing acid leaching with an oxidizing agent added to the acid leaching residue, the copper can be removed from the leaching solution, and a higher grade carbon concentrate can be recovered. When the pH is less than 0, the sulfate ion concentration in the acid leaching solution increases, and the loss of lithium into the neutralization cake generated in the neutralization step becomes large.

[0067] For the lithium concentration and sulfate ion concentration of the acid leaching solution, in order to reduce the coprecipitation and adsorption loss of lithium due to the large generation of neutralization cake in the neutralization step, it is preferable that the lithium concentration is less than 4,000 mg / L and the sulfate ion concentration is 60,000 mg / L or less.

[0068] Here, the leaching method in the acid leaching step is not particularly limited and can be appropriately selected according to the purpose. For example, there are methods such as simply putting the non-magnetic material slurry into acid, putting the non-magnetic material slurry into acid and stirring, adding acid to the non-magnetic material slurry, and adding acid to the non-magnetic material slurry and then stirring. As the acid leaching method, for example, the method of adding acid to the non-magnetic material slurry is preferable, and the method of adding acid to the non-magnetic material slurry and then stirring is more preferable. By adding acid to the non-magnetic material slurry, local temperature rise and bumping due to heat generation during the reaction between the non-magnetic material and the acid can be suppressed.

[0069] The stirring speed of sulfuric acid in the acid leaching step is not particularly limited and can be appropriately selected according to the purpose. For example, it can be set to 200 rpm.

[0070] The liquid temperature during acid leaching is preferably 0°C or higher and 80°C or lower, and more preferably 10°C or higher and 60°C or lower. In the acid leaching solution, fluorine derived from LiPF6 (lithium hexafluorophosphate), which is an electrolyte in the electrolyte of the lithium-ion secondary battery, is dissolved as hydrofluoric acid. By setting the liquid temperature during acid leaching to 60°C or lower, the generation of harmful and corrosive hydrofluoric acid vapor can be suppressed.

[0071] In the acid leaching step, an oxidizing agent may be added. By adding an oxidizing agent, the dissolution of impurities (such as copper) that are difficult to dissolve in acid can be promoted, and the carbon (C) grade of the carbon (C) concentrate (acid leaching residue) can be further improved. The oxidizing agent is not particularly limited and can be appropriately selected according to the purpose. For example, hydrogen peroxide, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, halogen, permanganate, ozone, air, etc. can be mentioned.

[0072] The leaching time in the acid leaching step is not particularly limited and can be appropriately selected according to the purpose. For example, it can be set to 1 hour.

[0073] The carbon (C) grade of the acid leaching residue obtained in the acid leaching step is preferably 80% or higher, and more preferably 90% or higher. In addition, when using the acid leaching residue (carbon (C) concentrate) as a reducing agent for smelting, since phosphorus (P) is an element to be avoided in steelmaking and fluorine (F) is an element that imposes a load on the exhaust gas treatment in smelting, it is preferable to remove phosphorus and fluorine from the acid leaching residue (carbon (C) concentrate) as much as possible. Furthermore, the carbon (C) concentrate contains copper (Cu) as a main impurity. The separation of this copper can be carried out by dispersion of carbon by a dispersant and precipitation of copper, recovery of copper into tailings by flotation, recovery of copper into heavy products by specific gravity separation, etc.

[0074] For the purpose of adjusting the lithium (Li) concentration of the acid leaching solution obtained in the acid leaching step, water may be added to the acid leaching solution. By reducing the lithium (Li) concentration, as shown in the neutralization step described later, the loss of lithium (Li) to the purification residue can be prevented. The acid leaching residue may be washed with water and may be subjected to solid-liquid separation after washing. The acid leaching residue may be attached with an acidic solution, and the amount of the attached acidic solution can be reduced by washing with water. For example, when sulfuric acid is used as the acidic solution, the sulfuric acid grade of the acid leaching residue can be reduced by washing the acid leaching residue with water and then performing solid-liquid separation. This washing can be carried out, for example, by pouring water into the filter chamber containing the acid leaching residue in the filter press as a solid-liquid separation device. As the weight of water used for washing, it is preferable to pass 0.1 kg or more of water per 1 kg of the acid leaching residue, and more preferably to pass 1 kg or more of water. Also, since lithium is leached into the passed water, it may be recovered.

[0075] <Neutralization Step> The neutralization step is a step of neutralizing the acid leaching solution obtained in the acid leaching step to a pH of 9.6 or more and less than 11.5. The neutralization step aims at neutralization of the acid leaching solution and solidification (neutralization caking) and separation by solid-liquid separation of impurity ions other than lithium (Li) (for example, boron ions, fluorine ions, sulfate ions, cobalt ions, nickel ions, aluminum ions, copper ions, etc.).

[0076] The neutralization can be carried out using a neutralizing agent (alkali). There are no particular restrictions on the neutralizing agent (alkali), and it can be appropriately selected according to the purpose. For example, calcium hydroxide (Ca(OH)2; slaked lime), sodium hydroxide, potassium hydroxide, calcium carbonate, calcium oxide, calcium aluminate, calcium phosphate, etc. can be mentioned. Among these, calcium hydroxide is preferred. These may be used alone or in combination of two or more.

[0077] The inventor has found that when calcium hydroxide is added to an acid leachate containing sulfate ions and aluminum ions, the boron ion concentration in the post-neutralization solution can be reduced to less than 0.1 mg / L, and the boron content in the recovered lithium carbonate can be reduced to less than 1 ppm. As for this mechanism, it is considered that boron is removed by the ettringite formation reaction between aluminum sulfate and calcium hydroxide and the hydroxyapatite formation reaction between phosphorus and ammonium ions (considered to be derived from aluminum nitride generated by heat treatment) in the leachate and calcium hydroxide. For boron removal, it is preferable to contain aluminum ions at 500 mg / L or more, and more preferably 1,000 mg / L or more. This aluminum ion concentration can be adjusted by dissolving aluminum (mainly derived from the positive electrode current collector) contained in the fine-grained product during acid leaching. Also, by the above reaction, the phosphorus concentration in the post-neutralization solution can be reduced to 1 mg / L, and the phosphorus content in the recovered lithium carbonate can be reduced to less than 10 ppm.

[0078] The neutralization step may include neutralization at multiple pH levels and multi-stage solid-liquid separation. For example, after the first-stage neutralization is carried out at a pH of 7 or more and less than 10.0, the liquid separated by solid-liquid separation in the first stage may be again raised to a pH of 9.6 or more and less than 11.5 (second-stage neutralization), and then the second-stage solid-liquid separation may be carried out.

[0079] Before adding the alkali, adding aluminum compounds such as aluminum sulfate, calcium aluminate, aluminum chloride, and aluminum hydroxide may reduce the removal amounts of boron and phosphorus more than when using the alkali alone. The alkali may be added in solid form or in slurry form. Before adding the alkali, adding a calcium salt such as calcium chloride can enhance the removal performance of sulfate ions.

[0080] Since sulfate ions and calcium ions form calcium sulfate, sulfate ions can be separated as a solid (calcium sulfate) by solid-liquid separation.

[0081] The pH after neutralization is not particularly limited as long as it is 9.6 or more and less than 11.5, and can be appropriately selected according to the purpose.

[0082] As the lower limit value of the pH after neutralization, as long as it is 9.6 or more, there is no particular limitation and it can be appropriately selected according to the purpose. However, in lithium carbonate obtained by treating the neutralized solution after neutralization, for reliable achievement of a zinc grade of less than 10 ppm, a manganese grade of less than 10 ppm, and a magnesium grade of less than 10 ppm, a pH of 9.7 or more is preferable, a pH of 9.8 or more is more preferable, and a pH of 10.0 or more is even more preferable. As the upper limit value of the pH after neutralization, as long as it is less than 11.5, there is no particular limitation and it can be appropriately selected according to the purpose. However, in the obtained lithium carbonate, for reliable achievement of a zinc grade of less than 10 ppm, a pH of 11.4 or less is preferable, and a pH of 11.2 or less is more preferable. Also, in the obtained lithium carbonate, for reduction of the loss of lithium to the neutralized precipitate due to an increase in the amount of neutralized precipitate generated, the pH can be set to 11 or less, can be set to 10.9 or less, can be set to 10.8 or less, can be set to 10.7 or less, and can be set to 10.4 or less. Note that a numerical range having any of the numerical values shown as the lower limit value and any of the numerical values shown as the upper limit value as the lower limit value and the upper limit value is preferable.

[0083] Among these, in the lithium carbonate obtained, in addition to reliably achieving a zinc content of less than 10 ppm, a manganese content of less than 10 ppm, and a magnesium content of less than 10 ppm, in order to reduce the loss of lithium to the neutralization precipitate due to an increase in the amount of neutralization precipitate (neutralization cake) generated in the neutralization step, a pH of 9.6 or more and 11.4 or less is preferable, a pH of 9.6 or more and 11.0 or less is more preferable, a pH of 9.7 or more and 10.9 or less is further preferable, a pH of 9.8 or more and 10.8 or less is even more preferable, and a pH of 10.0 or more and 10.8 or less is particularly preferable. Here, the pH of the solution means the pH at the end of the neutralization step.

[0084] The stirring time in the neutralization step is not particularly limited and can be appropriately selected according to the purpose, but is preferably 0.5 hours or more and 48.0 hours or less, and more preferably 1.0 hours or more and 24.0 hours or less. If the neutralization time is less than 0.5 hours, cake formation by neutralization may be insufficient, and there is a risk that the neutralization cake containing impurities cannot be sufficiently removed in the neutralization cake solid-liquid separation step, or there is a risk of an increase in the filtration resistance due to flocs. On the other hand, if the stirring time exceeds 48 hours, the production rate of lithium carbonate may decrease.

[0085] The lithium content in the liquid obtained by solid-liquid separation of the slurry obtained in the neutralization step is preferably 50% by mass or more, and more preferably 70% by mass or more, based on 100% by mass of the lithium content contained in the fine particle product. For the purpose of adjusting the lithium concentration of the slurry obtained in the neutralization step or the liquid obtained by solid-liquid separation of the slurry, water may be added to these slurries or liquids. By reducing these lithium (Li) concentrations, the loss of lithium (Li) can be prevented.

[0086] <Neutralization Cake Solid-Liquid Separation Step> The neutralization cake solid-liquid separation step is a step of performing solid-liquid separation on the post-neutralization liquid obtained in the neutralization step. The solid-liquid separation method is not particularly limited and can be appropriately selected according to the purpose. However, methods such as suction filtration using filter paper or the like, pressure filtration using a filter press or the like, or centrifugal separation using a centrifuge or the like for solid-liquid separation are preferred. Among these, pressure filtration is particularly preferred. By using pressure filtration, the water content in the cake can be efficiently reduced compared to other filtration methods such as suction filtration, and the loss of lithium into the neutralization cake can be reduced. Further, by passing water through the neutralization cake in the pressure filter, lithium in the water contained in the neutralization cake can be recovered into the water passing solution.

[0087] <Other processes> The other processes are not particularly limited and can be appropriately selected according to the purpose. For example, a calcium carbonate crystallization process, a calcium carbonate solid-liquid separation process, a concentration process, a calcium adsorption and removal process, a lithium carbonate crystallization process, and the like can be mentioned.

[0088] <Calcium carbonate crystallization process> The calcium carbonate crystallization process is a process of adding CO2 to the liquid obtained in the neutralization cake solid-liquid separation process. Here, "adding CO2" is a general term for the supply of CO2, HCO3 - , or CO3 2- to the liquid. The liquid obtained in the neutralization cake solid-liquid separation process contains about 100 mg / L to 1,000 mg / L of calcium ions. This dissolved calcium reacts with CO2 in the air, and calcium carbonate crystallizes. When a calcium adsorption and removal process is carried out on this liquid, a decrease in the calcium adsorption and removal efficiency may occur due to blockage of the resin tower or adhesion of calcium carbonate on the resin surface. Therefore, in the calcium carbonate crystallization process, CO2 is added to the liquid obtained in the neutralization cake solid-liquid separation process to crystallize calcium as calcium carbonate and reduce the dissolved amount of calcium.

[0089] The method for adding CO2 is not particularly limited and can be appropriately selected according to the purpose. For example, methods such as adding a gas containing CO2 such as air to the liquid, and adding a carbonate such as sodium carbonate can be mentioned. As the method for adding a gas containing CO2, for example, methods such as simply leaving the liquid in a state of being stationary in a gas containing CO2, diffusing a gas containing CO2 into the liquid, and stirring while blowing a gas containing CO2 into the liquid can be mentioned.

[0090] The addition amount of CO2 is preferably 0.1 or more in terms of the molar ratio to calcium ions in the liquid obtained in the neutralization cake solid-liquid separation step and 0.5 or less in terms of the molar ratio to lithium ions. More preferably, it is 0.5 or more in terms of the molar ratio to calcium ions and 0.25 or less in terms of the molar ratio to lithium ions. Particularly preferably, it is 0.8 or more in terms of the molar ratio to calcium ions and 0.1 or less in terms of the molar ratio to lithium ions. By supplying CO2 with a molar ratio to calcium ions of 0.1 or more, calcium ions can be crystallized as calcium carbonate. Also, by supplying CO2 with a molar ratio to lithium ions of 0.5 or less, crystallization of lithium carbonate in the calcium carbonate crystallization step, calcium adsorption removal step, and concentration step can be prevented.

[0091] <Calcium carbonate solid-liquid separation step> The calcium carbonate solid-liquid separation step is a step of solid-liquid separating the liquid obtained in the calcium carbonate crystallization step and removing calcium carbonate from the liquid. The solid-liquid separation method is not particularly limited and can be appropriately selected according to the purpose. For example, methods of solid-liquid separation such as suction filtration using filter paper etc., pressure filtration using a filter press etc., and centrifugal separation using a centrifuge etc. can be mentioned. Among these, pressure filtration is particularly preferred. By using pressure filtration, the water content in the neutralization cake can be efficiently reduced compared to other filtration methods such as suction filtration, and the loss of lithium into the neutralization cake can be reduced. When performing solid-liquid separation or after solid-liquid separation, water may be added to the neutralization cake to leach and recover lithium.

[0092] <Concentration process> The concentration process is a process of concentrating lithium contained in the liquid obtained after the calcium carbonate solid-liquid separation process by electrodialysis. The concentration process is preferably carried out before the calcium adsorption and removal process described later.

[0093] By including the concentration process, for example, the lithium concentration contained in the solution can be increased to a concentration at which it can be easily crystallized as lithium carbonate in the lithium carbonate crystallization process. In the concentration process, since the concentration is carried out by electrodialysis, the production rate of lithium carbonate can be increased by more than five times with the same scale of equipment compared to the case of performing evaporation concentration. Also, although a small amount of lithium is dissolved in the dilute solution recovered by electrodialysis, by using the lithium again in the slurrying process, the recovery of the lithium and the reduction of the water consumption can be achieved.

[0094] When calcium ions are contained in the raw material liquid, there may be a problem that calcium ions are adsorbed on the ion exchange membrane of the electrodialysis device and block the membrane. However, by applying the concentration process to the liquid after the calcium carbonate separation process (the liquid in which calcium is reduced to 10 mg / L or less), the occurrence of the above problem can be avoided.

[0095] The ion exchange membrane used in electrodialysis may adsorb and retain calcium. The cation exchange membrane has cation exchange groups fixed in the membrane, and the cations in the liquid pass through while repeating adsorption and dissociation with the counter ions. Therefore, a certain amount of cations remains retained in the ion exchange membrane even after electrodialysis. By making the concentration process the previous process of the calcium adsorption and removal process, even when the calcium ions retained in this ion exchange membrane are mixed into the lithium solution, the calcium ion concentration can be reduced in the calcium adsorption and removal process, and it becomes possible to recover lithium carbonate.

[0096] <Calcium adsorption and removal process> The calcium adsorption and removal step is a step of adsorbing and removing calcium using a chelating resin after the neutralization cake solid-liquid separation step, after the calcium carbonate solid-liquid separation step, or after the concentration step. The calcium adsorption and removal step can be carried out after the calcium carbonate solid-liquid separation step. Multiple types of resin towers may be used in the calcium adsorption and removal step.

[0097] By bringing the chelating resin into contact with the post-neutralization liquid, the post-calcium carbonate solid-liquid separation liquid, or the post-concentration liquid, calcium ions remaining in trace amounts in these liquids can be adsorbed and removed by the chelating resin. By doing so, the calcium grade in lithium carbonate can be further reduced. Compared with cation exchange resins, chelating resins can separate calcium from lithium more selectively. Also, without supplying CO3 2- ions, Ca 2+ is removed (to obtain a post-calcium adsorption and removal liquid), so CO3 2- ions do not dissolve in the post-calcium adsorption and removal liquid. As a result, it becomes possible to concentrate the post-calcium adsorption and removal liquid to a lithium concentration exceeding 5,000 mg / L without precipitating lithium carbonate. Also, since the lithium concentration can be increased before the lithium carbonate crystallization step, the cost and time required for the recovery of lithium carbonate in the lithium carbonate crystallization step can be reduced. Also, when using calcium hydroxide in the neutralization step, the calcium concentration in the post-neutralization liquid can be suppressed to 1,000 mg / L or less. Furthermore, by the calcium carbonate crystallization step and the calcium carbonate solid-liquid separation step, the calcium concentration in the liquid after the calcium carbonate solid-liquid separation step can be suppressed to 10 mg / L or less. From this, the amount of chelating resin used per unit amount of the post-neutralization liquid is small, and calcium removal can be carried out at low cost (economically).

[0098] The chelating resin is not particularly limited and can be appropriately selected according to the purpose. However, a chelating resin having an aminophosphoric acid group or a chelating resin having an iminodiacetic acid group is preferred, and a chelating resin having an iminodiacetic acid group is particularly preferred. Although a part of copper ions may remain in the liquid after neutralization, the use of a chelating resin having an iminodiacetic acid group can adsorb and remove copper ions, making the copper ion concentration in the liquid after calcium adsorption and removal less than 0.1 mg / L and the copper grade in the recovered lithium carbonate less than 10 ppm. The liquid passing rate through the chelating resin is preferably SV 0.5 or more and 15 or less, more preferably SV 1 or more and 10 or less, and particularly preferably SV 2 or more and 5 or less. By setting it to SV 0.5 or more and 15 or less, the calcium concentration in the liquid after calcium adsorption and removal can be made less than 0.1 mg / L.

[0099] <Lithium carbonate crystallization step> In the lithium carbonate crystallization step, lithium carbonate is selectively crystallized by utilizing the difference in solubility between lithium carbonate and other lithium salts (for example, lithium sulfate and lithium fluoride).

[0100] Lithium carbonate crystallization is carried out by adding carbon dioxide (CO2) to the concentrated liquid containing lithium after the concentration step. By doing so, lithium carbonate in the concentrated liquid containing lithium is more likely to precipitate, and lithium carbonate precipitates preferentially over lithium (for example, lithium fluoride) combined with other impurities (for example, fluorine), so that higher-grade lithium carbonate can be recovered.

[0101] Also, the method of adding carbon dioxide to the concentrated liquid containing lithium is not particularly limited and can be appropriately selected according to the purpose. However, it can be carried out by blowing a gas containing carbon dioxide or adding a carbonate, and adding a carbonate is preferred, and adding sodium carbonate is particularly preferred. The carbonate ion concentration of the concentrated liquid containing lithium after supplying carbon dioxide is preferably 2 or more with respect to a lithium concentration of 1, more preferably 3 or more with respect to a lithium concentration of 1, and particularly preferably 4 or more and 32.3 or less with respect to a lithium concentration of 1. When the carbonate ion concentration is less than 2 with respect to a lithium concentration of 1, the precipitation amount of lithium sulfate in addition to lithium carbonate may increase, and industrial grade (lithium carbonate grade 99.0% or more) lithium carbonate may not be crystallized. On the other hand, when the carbonate ion concentration exceeds 32.3 with respect to a lithium concentration of 1, the liquid in which the metal derived from the carbonate added to dissolve the carbonate ion is dissolved may contain water in lithium carbonate, and the metal grade derived from the carbonate in lithium carbonate may become excessive.

[0102] It is preferable to continuously stir the liquid during the crystallization of lithium carbonate. By stirring, the concentrations of carbonate ions and impurity ions (for example, fluoride ions and sulfate ions) in the liquid can be made uniform, and the particle size of the precipitate of lithium carbonate can be made uniform. As a result, the formation of impurity crystals or the entrainment of the liquid into the lithium carbonate precipitate can be reduced, so that the impurity grade in the recovered lithium carbonate can be reduced. During the crystallization of lithium carbonate, the crystallization step may be started or continued in a state where crystals of lithium carbonate are added in advance or during crystallization. By adding this crystal (seed crystal), the particle size of the lithium carbonate recovered by crystallization can be improved and homogenized, so that the water content of the crystal can be reduced, and the impurity grade derived from the water-containing component can be further reduced. The lithium carbonate crystallization step is preferably carried out while heating the concentrated liquid containing lithium. By heating the concentrated liquid containing lithium, the solubility of lithium carbonate can be reduced, and the recovery amount of lithium carbonate can be further increased.

[0103] The method of heating the concentrated liquid containing lithium is not particularly limited and can be appropriately selected according to the purpose. For example, methods such as heating with an electric heater or heating with a pipe made of copper, stainless steel, Teflon (registered trademark), etc. through which heating steam passes can be mentioned. For example, when heating a concentrated solution containing lithium to precipitate lithium carbonate, the temperature of the solution is not particularly limited as long as it is a temperature at which lithium carbonate can be precipitated, and it can be appropriately selected according to the purpose. For example, a temperature of 60°C or higher and 105°C or lower is preferable.

[0104] <<Recovery of Lithium Carbonate as a Valuable Substance>> The lithium carbonate contained in the slurry obtained in the lithium carbonate crystallization step can be recovered by solid-liquid separation of the slurry to separate lithium carbonate (solid) and the post-crystallization liquid. The solid-liquid separation method is not particularly limited and can be appropriately selected according to the purpose. However, a method of solid-liquid separation by suction filtration using filter paper or the like, pressure filtration using a filter press or the like, or centrifugation using a centrifuge or the like is preferable. Among these, pressure filtration is particularly preferable. By using pressure filtration, the water content in lithium carbonate can be efficiently reduced compared to other filtration methods such as suction filtration. Further, by passing water through the lithium carbonate cake in the pressure filter, sulfate ions, sodium ions, and potassium ions in the lithium carbonate cake can be recovered in the passing water.

[0105] It is preferable to wash (rinse with hot water) the recovered lithium carbonate by supplying warm water. In the present invention, the mixing of sulfuric acid in the recovered lithium carbonate is due to sulfate ions contained in the water content of lithium carbonate rather than crystals (lithium sulfate), so it can be removed by rinsing with hot water, and the sulfuric acid grade can be further reduced. In addition, potassium derived from the constituent members of the recovered lithium-ion secondary battery is contained, but this potassium can also be removed by rinsing with hot water. The temperature of the warm water is preferably 60°C or higher, more preferably 80°C or higher. The higher the temperature of the warm water, the lower the dissolution amount of lithium carbonate in the warm water and the lower the loss of lithium in the warm water.

[0106] By washing the lithium carbonate with warm water, for example, lithium carbonate with a sulfuric acid content and a sodium content of both 0.5% by mass or less, lithium carbonate with a potassium content of 50 ppm or less, or lithium carbonate with a sulfuric acid content and a sodium content of both 0.5% by mass or less and a potassium content of 50 ppm or less can be obtained. The post-crystallization liquid (post-crystallization liquid) after recovering lithium carbonate contains lithium ions, fluoride ions, and sulfate ions. By repeatedly processing this again in the neutralization step, the recovery rate of lithium can be further improved. As described above, from a lithium-ion secondary battery, lithium carbonate with a zinc content of less than 10 ppm, a manganese content of less than 10 ppm, and a magnesium content of less than 10 ppm can be recovered. Preferably, lithium carbonate with a boron content of less than 1 ppm can also be recovered.

[0107] <First Embodiment> Here, with reference to the drawings, an example of an embodiment in the method for recovering valuable substances of the present invention will be described. FIG. 1 is a diagram showing an example of the flow of processing in the first embodiment of the method for recovering valuable substances of the present invention. First, a heat treatment (heat treatment step) is performed on a lithium-ion secondary battery (LIB; Lithium Ion Battery) to obtain a LIB heat-treated product. Next, the LIB heat-treated product is subjected to crushing and classification (crushing and classification step) to obtain a coarse-grained product and a fine-grained product. Here, as the coarse-grained product, copper (Cu) or iron (Fe) etc. can be separated. Subsequently, the fine-grained product is immersed in water to obtain a fine-grained product slurry.

[0108] Next, the fine-grained product slurry is subjected to wet magnetic separation to be separated into a magnetic attachment and a non-magnetic attachment slurry. The magnetic attachment contains nickel (Ni), cobalt (Co), and manganese (Mn) integrated with cobalt. The non-magnetic attachment slurry contains lithium aluminate, carbon, copper (the one that could not be recovered in the coarse-grained product), and lithium (water-soluble). Next, sulfuric acid is added to the non-magnetized material slurry to acid-leach lithium in the lithium aluminate contained in the non-magnetized material, and then solid-liquid separation is performed to separate the slurry into a filtrate (acid leachate) and a filtration residue (carbon concentrate).

[0109] Next, a neutralizing agent is added to the acid leachate to any pH, and after neutralization for 1 hour to 48 hours after the addition is completed, solid-liquid separation is performed to separate the slurry into a filtrate (post-neutralization liquid) and a filtration residue (neutralization cake).

[0110] In the first embodiment, a lithium-ion secondary battery is heat-treated, crushed and classified, and the obtained fine-grained product is immersed in water to obtain a fine-grained product slurry. The obtained fine-grained product slurry is subjected to wet magnetic separation, sulfuric acid is added to the obtained non-magnetized material slurry for acid leaching, and then a neutralization step is performed. Pressure filtration is performed with a filter press for solid-liquid separation to recover the post-neutralization liquid, whereby lithium carbonate having a zinc grade of less than 10 ppm, a manganese grade of less than 10 ppm, and a magnesium grade of less than 10 ppm can be recovered from the lithium-ion secondary battery.

[0111] <Second Embodiment> FIG. 2 is a diagram showing an example of the flow of processing in the second embodiment of the method for recovering valuable materials of the present invention. First, a heat treatment (heat treatment step) is performed on a lithium-ion secondary battery (LIB; Lithium Ion Battery) to obtain a heat-treated LIB product. Next, crushing and classification (crushing / classification step) are performed on the heat-treated LIB product to obtain a coarse-grained product and a fine-grained product. Here, copper (Cu), iron (Fe), etc. can be separated as the coarse-grained product. Subsequently, the fine-grained product is immersed in water to obtain a fine-grained product slurry.

[0112] Next, the fine-grained product slurry is subjected to wet magnetic separation to be separated into a magnetized material and a non-magnetized material slurry. The magnetized material contains nickel (Ni), cobalt (Co), and manganese (Mn) integrated with cobalt. The non-magnetic substance slurry contains lithium aluminate, carbon, copper (the part that could not be recovered in the coarse product), and lithium (water-soluble). Next, sulfuric acid is added to the non-magnetic substance slurry to acid-leach lithium in the lithium aluminate contained in the non-magnetic substance, and then solid-liquid separation is performed to separate it into a filtrate (acid leachate) and a filtration residue (carbon concentrate).

[0113] Next, a neutralizing agent or calcium salt containing calcium is added to the acid leachate, and solid-liquid separation is performed by pressure filtration using a filter press to separate it into a liquid containing lithium (post-neutralization liquid) and a solidified product containing impurities such as boron, fluorine, and aluminum. Sodium carbonate is added to the post-neutralization liquid for calcium carbonate crystallization, and then solid-liquid separation is performed by pressure filtration. The liquid after calcium carbonate solid-liquid separation is concentrated by electrodialysis to obtain a lithium concentrate. Trace amounts of calcium ions in the lithium concentrate that could not be completely removed by calcium carbonate crystallization are adsorbed and removed by chelating resin to obtain a liquid after calcium adsorption and removal. Lithium carbonate serving as a seed crystal is added to the liquid after calcium adsorption and removal, heated, and then sodium carbonate is added to crystallize and recover lithium as lithium carbonate (Li2CO3).

[0114] In the second embodiment, a lithium-ion secondary battery is heat-treated, crushed and classified, and the obtained fine product is immersed in water to obtain a fine product slurry. The obtained fine product slurry is subjected to wet magnetic separation, sulfuric acid is added to the obtained non-magnetic substance slurry for acid leaching, a neutralizing agent is added for neutralization, and pressure filtration is performed using a filter press for solid-liquid separation to recover the post-neutralization liquid. After adding CO2 to the obtained post-neutralization liquid, solid-liquid separation is performed to recover the liquid with calcium removed as calcium carbonate, and trace amounts of calcium ions remaining in the liquid are adsorbed and removed by chelating resin, whereby lithium carbonate with a zinc grade of less than 10 ppm, a manganese grade of less than 10 ppm, and a magnesium grade of less than 10 ppm can be recovered from the lithium-ion secondary battery. Preferably, lithium carbonate with a zinc grade of less than 10 ppm, a manganese grade of less than 10 ppm, a magnesium grade of less than 10 ppm, and a boron grade of less than 1 ppm can also be recovered.

Example

[0115] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments at all.

[0116] (Example 1) <Heat treatment> For an in-vehicle lithium-ion secondary battery pack of 300 kg in which the exterior case (housing) is made of aluminum (including iron in some parts) (the lithium-ion secondary battery has an aluminum foil as the positive electrode current collector, a copper foil as the negative electrode current collector, a carbon material as the negative electrode active material, and the electrolyte contains fluorine), as shown in the processing flow of FIG. 1, a heat treatment step, a crushing step, a classification step, a magnetic separation step, and a wet separation step were performed to recover valuable materials. Specifically, it is as follows. For the lithium-ion secondary battery pack, a fixed-bed furnace with a cylindrical furnace interior (diameter 4,300 mm × height 6,500 mm) was used as the heat treatment apparatus, and heat treatment was performed under the conditions of a heat treatment temperature of 800 °C (heated from 20 °C to 800 °C over 15 minutes and then held for 2 hours) in an air atmosphere. In the heat treatment, the in-vehicle lithium-ion secondary battery pack was placed on a tray for recovering aluminum derived from the housing, and the aluminum derived from the housing was melted and recovered in the tray as a melt.

[0117] <Crushing and classification> Next, in the crushing step, as the crushing device, a hammer crusher (Makino type swing hammer crusher HC-20-3.7, manufactured by Makino Sangyo Co., Ltd.) was used, and the lithium-ion secondary battery subjected to heat treatment was crushed under the conditions of 50 Hz (hammer peripheral speed 38 m / s) and a punching metal hole diameter of 10 mm at the outlet portion to obtain crushed materials of the lithium-ion secondary battery. Subsequently, using a sieve with a mesh opening of 1.2 mm (diameter 200 mm, manufactured by Tokyo Screen Co., Ltd.), the crushed materials of the lithium-ion secondary battery were sieved. The material on the 1.2 mm sieve (coarse-grained product) and the material under the sieve (fine-grained product) after sieving were collected respectively. When the lithium content contained in the lithium-ion secondary battery was set to 100%, the loss amount of lithium in the coarse-grained product was 1%, and 99% could be recovered in the fine-grained product.

[0118] <Slurrying and Solid-Liquid Separation> Regarding the obtained fine-grained product, 50 kg of the fine-grained product was immersed in 250 L of water, and lithium was leached into the water under the conditions of a solid-liquid ratio of 20%, a stirring speed of 400 rpm, and a leaching time of 1 hour to obtain a fine-grained product slurry.

[0119] <Wet Magnetic Separation> The obtained fine-grained product slurry was subjected to wet magnetic separation using a drum-type magnetic separator (product name: WD L-8 Lab Model, manufactured by Eriez Magnetics Co., Ltd.) at a magnetic force of 1500 G, a drum rotation speed of 45 rpm, a solid-liquid ratio of 20%, and a slurry supply speed of 100 L / h, and 250 L of magnetic adherents (containing water) and non-magnetic adherent slurry were recovered. The magnetic adherents (containing water) were pressure-filtered at a pressure of 0.6 MPa using a filter press with a filter cloth (product name: PP934K, manufactured by Nakao Filter Industry Co., Ltd.) to obtain magnetic adherents (dehydrated). These magnetic adherents (dehydrated) were dried at 105 °C for 24 hours using a dryer (product name: DRM620DD, manufactured by Advantec Toyo Co., Ltd.) to obtain magnetic adherents.

[0120] <Acid Leaching> Acid leaching with sulfuric acid was performed on the non-magnetic adherent slurry (250 L). While adding 75% concentrated sulfuric acid to the non-magnetic adherent slurry in a 1,000 L FRP tank (product, diameter 1,084 mm, height 1,500 mm) and adjusting the pH to 1.5, stirring was carried out at a stirring speed of 200 rpm for 1 hour using a stirrer (product name: Super Agitator, model number: TTF-2V, manufactured by Toyoki Kogyo Co., Ltd.) to leach lithium. The lithium concentration in the acid leaching solution was 2,400 mg / L, and the sulfate ion concentration was 41,000 mg / L.

[0121] <Neutralization> The obtained acid leaching solution was prepared in an FRP tank (product, diameter 1,084 mm, height 1,500 mm). While stirring this with a stirrer (product name: HP-5006, manufactured by Sakwa Chemical Machinery Co., Ltd.) at a stirring speed of 200 rpm, slaked lime slurry with a slurry concentration of 10% was automatically added until the pH reached 10.0, and stirring was carried out for 16 hours while maintaining the pH.

[0122] <Neutralization Cake Solid-Liquid Separation> The liquid obtained in the neutralization step was subjected to solid-liquid separation by pressure filtration at a pressure of 0.6 MPa using a filter press with a filter cloth (product name: PP934K, manufactured by Nakao Filter Industry Co., Ltd.), and the filtrate was recovered as the post-neutralization liquid.

[0123] <Concentration Step> The liquid after solid-liquid separation of the neutralization cake was concentrated 5-fold using an electrodialysis apparatus (product name: AC-10, manufactured by Asahi Kasei Corporation).

[0124] <Lithium Carbonate Crystallization Step> With the concentrated liquid heated to 90 °C, 10 mass% of lithium carbonate as seed crystals and 1.5 equivalents of sodium carbonate relative to the amount of lithium in the concentrated liquid were added, followed by stirring for 1 hour. After that, solid-liquid separation was performed using a filter press to obtain lithium carbonate crystallized product and post-crystallization liquid.

[0125] <Evaluation of Liquid Composition of Li Acid Leaching Solution and Post-Neutralization Liquid> For the Li acid leaching solution before adding calcium hydroxide and the post-neutralization liquid, analysis was performed using a high-frequency inductively coupled plasma optical emission spectrometer (iCaP6300, manufactured by Thermo Fisher Scientific), and the concentrations of the items shown in Table 1 were determined. The results of the post-neutralization liquid are shown in Table 1. Regarding fluorine, analysis was performed by ion chromatography based on JIS K0202:2008.

[0126] <Evaluation of Lithium Carbonate Quality> The mass of lithium carbonate was measured using an electromagnetic balance (product name: GX-8K, manufactured by A&D Company, Ltd.) after drying at 105 °C for 1 hour. Thereafter, the dried sample was heated and dissolved in aqua regia (manufactured by Fujifilm Wako Pure Chemical Corporation), and analysis was performed using a high-frequency inductively coupled plasma optical emission spectrometer (product name: iCaP6300, manufactured by Thermo Fisher Scientific), and the content ratios of various impurities other than fluorine in lithium carbonate were determined. The results are shown in Table 2. Regarding the fluorine quality, analysis was performed by ion chromatography based on JIS K0202:2008.

[0127]

Table 1

[0128]

Table 2

[0129] (Example 2) In the neutralization step of Example 1, except that slaked lime slurry with a slurry concentration of 10% was automatically added until the pH reached 10.4, the procedure was the same as in Example 1, evaluated in the same manner as in Example 1, and the results are shown in Table 1 and Table 2.

[0130] (Example 3) In the neutralization step of Example 1, except that slaked lime slurry with a slurry concentration of 10% was automatically added until the pH reached 11.0, the procedure was the same as in Example 1, evaluated in the same manner as in Example 1, and the results are shown in Table 1 and Table 2.

[0131] (Example 4) In the neutralization step of Example 1, except that slaked lime slurry with a slurry concentration of 10% was automatically added until the pH reached 9.7, the procedure was the same as in Example 1, evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0132] (Example 5) In the neutralization step of Example 1, except that slaked lime slurry with a slurry concentration of 10% was automatically added until the pH reached 10.9, the procedure was the same as in Example 1, evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0133] (Comparative Example 1) In the neutralization step of Example 1, except that slaked lime slurry with a slurry concentration of 10% was automatically added until the pH reached 9.0, the procedure was the same as in Example 1, evaluated in the same manner as in Example 1, and the results are shown in Table 1 and Table 2.

[0134] (Comparative Example 2) In the neutralization step of Example 1, except that slaked lime slurry with a slurry concentration of 10% was automatically added until the pH reached 11.5, the procedure was the same as that of Example 1, and the evaluation was carried out in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0135] (Comparative Example 3) In the neutralization step of Example 1, except that slaked lime slurry with a slurry concentration of 10% was automatically added until the pH reached 12.3, the procedure was the same as that of Example 1, and the evaluation was carried out in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0136] From the results in Table 1, it was found that by the method for recovering valuable substances of the present invention including a neutralization step for neutralizing to a pH of 9.6 or more and less than 11.5, the concentrations of zinc, manganese, and magnesium in the post-neutralization liquid can be sufficiently reduced. A concentration step and a lithium carbonate crystallization step were performed on the post-neutralization liquids shown in Examples 1 to 3 in Table 1 to recover lithium carbonate. The recovered lithium carbonate was high-quality lithium carbonate with a zinc grade of less than 10 ppm, a manganese grade of less than 10 ppm, and a magnesium grade of less than 10 ppm as described in Table 2. Furthermore, it was found that the loss of lithium to the neutralization precipitate was also reduced. From the results in Table 1, zinc could not be sufficiently removed from the post-neutralization liquid at a pH of 11.5 or more. Also, at a pH of less than 9, manganese and magnesium could not be sufficiently removed from the post-neutralization liquid. By performing a concentration step and a lithium carbonate crystallization step on the post-neutralization liquids shown in Comparative Examples 1 to 3 in Table 1, the recovered lithium carbonate had a zinc grade of 10 ppm or more, or both the manganese grade and the magnesium grade exceeded 10 ppm as described in Table 2.

Claims

1. A method for recovering valuable materials, comprising recovering lithium carbonate having a zinc content of less than 10 ppm, a manganese content of less than 10 ppm, and a magnesium content of less than 10 ppm from a lithium ion secondary battery, the method comprising: a heat treatment step of heat-treating the lithium ion secondary battery at a temperature of 660° C. or higher to obtain a heat-treated product; a crushing and classification step of crushing the heat-treated product and classifying the crushed product to obtain a coarse product and a fine product containing the valuable material; a slurrying step of forming the fine product into a fine product slurry by soaking the fine product in water; A wet magnetic separation step of separating the fine product slurry into a magnetic material and a non-magnetic material slurry by wet magnetic separation; an acid leaching step of adding sulfuric acid to the non-magnetic material slurry and / or non-magnetic materials obtained by solid-liquid separation of the non-magnetic material slurry, adjusting the pH to 0 to 3.5 to leach the non-magnetic materials, and then performing solid-liquid separation to obtain an acid leaching solution and an acid leaching residue; a neutralization step of neutralizing the acid leachate to a pH of 9.6 or more but less than 11.5; a neutralization cake solid-liquid separation step of performing solid-liquid separation of the liquid obtained in the neutralization step; A method for recovering valuable materials, comprising:

2. The method for recovering valuable materials according to claim 1 , wherein the pH is neutralized to 9.6 or more and 11.0 or less in the neutralization step.

3. The method for recovering valuable materials according to claim 1 , wherein the pH is neutralized to 9.7 or more and 10.9 or less in the neutralization step.

4. The liquid obtained in the neutralized cake solid-liquid separation step is treated with CO ２ a calcium carbonate crystallization step of adding a calcium carbonate solid-liquid separation step of performing solid-liquid separation of the liquid obtained in the calcium carbonate crystallization step; The method for recovering valuable materials according to claim 1, comprising:

5. In the calcium carbonate crystallization process, ２ 5. The method for recovering valuable materials according to claim 4, wherein the amount of added is 0.1 or more in terms of a molar ratio to calcium ions in the liquid obtained in the neutralized cake solid-liquid separation step, and 0.5 or less in terms of a molar ratio to lithium ions.

6. 5. The method for recovering valuable materials according to claim 4, further comprising, after the calcium carbonate solid-liquid separation step, a concentration step of concentrating lithium contained in the liquid obtained in the calcium carbonate solid-liquid separation step by electrodialysis.

7. 5. The method for recovering valuable resources according to claim 4, further comprising a calcium adsorption and removal step of adsorbing and removing calcium with a chelating resin after the calcium carbonate solid-liquid separation step.

8. 8. The method for recovering valuable materials according to claim 7, wherein the chelating resin is a chelating resin having an iminodiacetic acid group.

9. 2. The method for recovering valuable materials according to claim 1, wherein calcium hydroxide is used as a neutralizing agent in the neutralization step.

10. The method for recovering valuable resources according to any one of claims 1 to 9, wherein the lithium carbonate has a sulfuric acid grade and a sodium grade of 0.5 mass% or less.

11. The method for recovering valuable materials according to any one of claims 1 to 9, wherein the potassium content of the lithium carbonate is 50 ppm or less.

12. The method for recovering valuable materials according to any one of claims 1 to 9, wherein the lithium carbonate has a boron content of less than 1 ppm.

13. The method for recovering valuable materials according to claim 1 , wherein the lithium ion secondary battery is a lithium ion battery pack or a lithium ion battery module.

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