Method for recovering valuable materials and method for treating solid electrolytes

Abstract

To provide a method for recovering valuable materials that enables efficient and safe recovery of high-quality valuable metals from batteries containing sulfide-based solid electrolytes, and a method for treating solid electrolytes that enables efficient and safe processing of solid electrolytes.SOLUTION: A method for recovering valuable materials includes a heat treatment step of heat-treating a sulfide-based solid electrolyte in a battery having the sulfide-based solid electrolyte under a humid atmosphere with a dew point of -10°C or higher. A method for treating a solid electrolytes includes the step of heat-treating the sulfide-based solid electrolyte under a humid atmosphere with a dew point of -10°C or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for recovering valuable materials and a method for treating solid electrolytes. [Background technology]

[0002] Lithium-ion secondary batteries are lightweight, have a high capacity, and have a high electromotive force compared to conventional lead-acid batteries and nickel-cadmium secondary batteries. They are used as secondary batteries in personal computers, electric vehicles, mobile devices, etc. For example, the positive electrode of a lithium-ion secondary battery contains valuable materials such as cobalt and nickel, lithium cobalt oxide (LiCoO2), ternary positive electrode materials (LiNi x Co y Mn z O2(x+y+z=1)) and so on.

[0003] Conventionally, liquid electrolytes have been used in secondary batteries, but in recent years, solid electrolytes have come to be used to ensure safety during thermal runaway and to improve battery performance. It is known that hydrogen sulfide is generated when sulfide-based solid electrolytes come into contact with moisture in the air, and therefore, there is a need to detoxify discarded sulfide-based solid electrolytes so that they do not generate hydrogen sulfide. Furthermore, like conventional lithium-ion batteries, batteries containing sulfide-based solid electrolytes may contain valuable materials such as cobalt, nickel, lithium, copper, and aluminum, and there is a need to recover valuable materials from batteries containing sulfide-based solid electrolytes after the detoxification process.

[0004] A method for treating battery components is known, which includes a contacting step in which a battery having a sulfide-based solid electrolyte is immersed in water to generate hydrogen sulfide and dissolve Li contained in the sulfide solid electrolyte material in the treatment solution; a positive electrode active material recovery step in which the positive electrode active material, which is an insoluble component, is recovered from the treatment solution in which the Li has been dissolved; and a Li compound recovery step in which Li compounds are recovered from the treatment solution from which the positive electrode active material, which is an insoluble component, has been recovered (Patent Document 1).

[0005] However, in the above-mentioned method, a large amount of hydrogen sulfide reacts rapidly when the sulfide-based solid electrolyte is immersed in water. Furthermore, it is impossible to predict the time when water reaches the sulfide-based solid electrolyte incorporated in the all-solid-state battery and the rapid generation of hydrogen sulfide begins. Furthermore, when battery components such as copper or aluminum are immersed in water, a drying process is required to recover these as valuable materials, making the process complicated. As described above, the above-mentioned method is not sufficiently safe and the process is complicated. A valuable material recovery method that can efficiently and safely recover high-quality valuable metals from batteries containing a sulfide-based solid electrolyte, and a solid electrolyte treatment method that can efficiently and safely treat solid electrolytes have not yet been provided, and there is a strong demand for their prompt provision. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2010 / 106618 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to solve the above-mentioned problems in the prior art and to achieve the following objectives: That is, the present invention aims to provide a valuable resource recovery method that can efficiently and safely recover high-quality valuable metals from batteries having a sulfide-based solid electrolyte, and a solid electrolyte treatment method that can efficiently and safely treat the solid electrolyte. [Means for solving the problem]

[0008] As a result of intensive research by the inventors to achieve the above-mentioned object, it has been found that it is possible to provide a valuable resource recovery method that includes a heat treatment step of heat-treating a sulfide-based solid electrolyte in a battery having a sulfide-based solid electrolyte in a water-containing atmosphere with a dew point of -10°C or higher, and a solid electrolyte treatment method that includes a step of heat-treating a sulfide-based solid electrolyte in a water-containing atmosphere with a dew point of -10°C or higher, thereby enabling high-quality valuable metals to be recovered efficiently and safely from batteries having a sulfide-based solid electrolyte, and a solid electrolyte treatment method that allows solid electrolytes to be treated efficiently and safely.

[0009] The present invention is based on the above findings by the present inventors, and the means for solving the above problems are as follows: <1> The method for recovering valuable resources includes a heat treatment step of heat-treating a sulfide-based solid electrolyte in a battery having the sulfide-based solid electrolyte at a heat treatment temperature of 70°C or higher in a water-containing atmosphere with a dew point of -10°C or higher. <2> The dew point in the water-containing atmosphere is 0°C or higher. <1> This is a method for recovering valuable materials described in the above. <3> The temperature of the water-containing atmosphere is 80°C or higher. <1> This is a method for recovering valuable materials described in the above. <4> The water-containing atmosphere is an atmosphere in which water vapor is present in a roasting furnace. <1> This is a method for recovering valuable materials described in the above. <5> After the heat treatment step, a crushing and classification step in which the heat-treated product obtained in the heat treatment step is crushed and the crushed product is classified to obtain a coarse product and a fine product containing the valuable material; a slurrying step of soaking the fine product in water to form a fine product slurry; a wet magnetic separation step of separating the fine product slurry into a magnetic material slurry and a non-magnetic material slurry by wet magnetic separation; an acid leaching step in which sulfuric acid is added to the non-magnetized material slurry and / or non-magnetized materials obtained by solid-liquid separation of the non-magnetized material slurry, and the non-magnetized materials are leached, followed by solid-liquid separation to obtain an acid leaching solution and an acid leaching residue; a neutralization step of neutralizing the acid leachate; a neutralization cake solid-liquid separation step of separating the liquid obtained in the neutralization step into solid and liquid; The above-mentioned <1> This is a method for recovering valuable materials described in the above. <6> The method for treating a solid electrolyte comprises a step of heat treating a sulfide-based solid electrolyte in a water-containing atmosphere having a dew point of −10° C. or higher. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for recovering valuable materials that can efficiently and safely recover high-quality valuable metals from batteries having a sulfide-based solid electrolyte, and a method for treating a solid electrolyte that can efficiently and safely treat the solid electrolyte. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing an example of the processing flow of the valuable resource recovery method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Method of recovering valuables) The method for recovering valuable materials includes a heat treatment step, and may further include other steps.

[0013] The method for recovering valuable materials of the present invention is a method for recovering valuable materials from a battery having a sulfide-based solid electrolyte. Here, valuables refer to things that can be traded without being discarded, such as various metals, etc. Valuables in batteries having a sulfide-based solid electrolyte include, for example, high-quality carbon (C) concentrate, copper (Cu), aluminum (Al), lithium (Li), cobalt (Co), and nickel (Ni).

[0014] -Batteries with sulfide-based solid electrolytes- The battery having a sulfide-based solid electrolyte is not particularly limited and can be appropriately selected depending on the purpose. Examples include a battery having a sulfide-based solid electrolyte that is a defective product generated during the manufacturing process, a battery having a sulfide-based solid electrolyte that is discarded due to a defect in the equipment used or the end of the life of the equipment, and a used battery having a sulfide-based solid electrolyte that is discarded due to the end of the life of the equipment.

[0015] The shape, structure, size, and material of the battery having the sulfide-based solid electrolyte are not particularly limited and can be appropriately selected depending on the purpose. The shape of the battery having the sulfide-based solid electrolyte is not particularly limited and can be appropriately selected depending on the purpose. Examples include laminate type, cylindrical type, button type, coin type, square type, and flat type. The form of the battery having the sulfide-based solid electrolyte is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a battery cell, a battery module, and a battery pack. Here, a battery module refers to a battery in which a plurality of battery cells, which are unit batteries, are connected and assembled into a single housing, and a battery pack refers to a battery in which a plurality of battery modules are assembled into a single housing. The battery pack may also be equipped with a controller or a cooling device.

[0016] Examples of the battery having the sulfide-based solid electrolyte include a battery including a positive electrode, a negative electrode, a sulfide-based solid electrolyte, and an outer container that is a battery case that houses the positive electrode, the negative electrode, and the sulfide-based solid electrolyte. Note that the battery having the sulfide-based solid electrolyte may be in a state in which the positive electrode, the negative electrode, etc. have fallen off.

[0017] --Positive electrode-- The positive electrode is not particularly limited as long as it contains a positive electrode active material, and can be appropriately selected depending on the purpose. Among these, those having a positive electrode current collector are preferred. The shape of the positive electrode is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a flat plate shape and a sheet shape.

[0018] ---Positive electrode current collector--- The shape, structure, size, material, etc. of the positive electrode current collector are not particularly limited and can be appropriately selected depending on the purpose. The positive electrode current collector may be in the form of, for example, a foil. Examples of the material for the positive electrode current collector include stainless steel, nickel, aluminum, copper, titanium, and tantalum, with aluminum being preferred among these.

[0019] The positive electrode material is not particularly limited and can be appropriately selected depending on the purpose. For example, a positive electrode material containing at least a positive electrode active material containing lithium, and optionally containing a conductive agent and a binder resin, can be used. Examples of the positive electrode active material include lithium manganese oxide (LiMn2O4) called LMO system, lithium cobalt oxide (LiCoO2) called LCO system, and LiNi x Co y Mn z O2(x+y+z=1), LiNi, also known as NCA x Co y Al z (x+y+z=1), lithium iron phosphate (LiFePO4), lithium cobalt nickel oxide (LiCo 1 / 2 Ni 1 / 2 Examples of the positive electrode active material include lithium titanate (Li2TiO3), Li2S, a sulfur / carbon composite, sulfur (S), etc. Furthermore, these materials may be used in combination as the positive electrode active material. The conductive agent is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include carbon black, graphite, carbon fiber, acetylene black, carbon replica, and metal carbide. The binder resin is not particularly limited and can be appropriately selected depending on the purpose. Examples include homopolymers or copolymers of vinylidene fluoride, tetrafluoroethylene, acrylonitrile, ethylene oxide, and the like, and styrene-butadiene rubber.

[0020] --Negative electrode-- The negative electrode is not particularly limited as long as it contains a negative electrode active material, and can be appropriately selected depending on the purpose. Examples of the negative electrode active material include a negative electrode active material containing carbon (C). Among these, those having a negative electrode current collector are preferred. The shape of the negative electrode is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a flat plate shape and a sheet shape.

[0021] ---Negative electrode current collector--- The shape, structure, size, material, etc. of the negative electrode current collector are not particularly limited and can be appropriately selected depending on the purpose. The negative electrode current collector may be in the form of, for example, a foil. Examples of the material for the negative electrode current collector include stainless steel, nickel, aluminum, copper, titanium, and tantalum, with copper being preferred among these.

[0022] The negative electrode active material is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include carbon materials such as graphite and hard carbon, silicon, lithium titanate, metallic lithium (Li), lithium-indium alloy (Li-In), etc. Furthermore, as the negative electrode active material, a non-carbon material such as titanate and silicon may be used in combination with carbon.

[0023] --Sulfide solid electrolyte-- The sulfide-based solid electrolyte is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include those containing Li and S. Among these, those further containing at least one third component selected from the group consisting of P, Ge, B, Si, I, Al, Ga, and As are preferred, and compounds using Li2S and a sulfide MS other than Li2S are preferred. Specific examples include Li2S-P2S5 compounds, Li2S-SiS2 compounds, Li2S-GeS2 compounds, etc. Among these, Li2S-P2S5 compounds are preferred because of their high Li-ion conductivity. Furthermore, when the molar ratio of Li2S to sulfide MS is xLi2S-(100-x)MS, x preferably satisfies the relationship 50≦x≦95, and more preferably 60≦x≦85. The Li2S-P2S5 compound refers to a sulfide solid electrolyte material using Li2S and P2S5. The same applies to other compounds. For example, an amorphous Li2S-P2S5 compound can be obtained by performing mechanical milling or melt quenching using Li2S and P2S5.

[0024] The sulfide solid electrolyte may be amorphous or crystalline. A crystalline sulfide solid electrolyte can be obtained, for example, by firing an amorphous sulfide solid electrolyte material. The sulfide solid electrolyte of the present invention preferably has bridging sulfur, since the sulfide solid electrolyte has high Li ion conductivity. When bridging sulfur is present, hydrogen sulfide is easily generated, which has the advantage of facilitating the dissolution of Li contained in the sulfide solid electrolyte. Furthermore, from the viewpoint of high Li ion conductivity, it is preferable that the sulfide solid electrolyte is Li7P3S 11 It is preferable that Li7P3S 11is a sulfide glass ceramic of the Li2S-P2S5 compound. The sulfide solid electrolyte is preferably a thio-LISICON type compound, such as a compound represented by LiaPbGecSd (2.8≦a≦4.2, 0.1≦b≦1.2, 0.1≦c≦1.2, 3≦d≦5). The average particle size of the sulfide solid electrolyte is, for example, in the range of 1 nm to 100 μm, and preferably in the range of 10 nm to 30 μm.

[0025] --Outer packaging-- The material of the outer container (casing) is not particularly limited and can be appropriately selected depending on the purpose. Examples include aluminum, iron, stainless steel, and resin (plastic).

[0026] Each step in the valuable resource recovery method of the present invention will be described in detail below.

[0027] <Heat treatment process> The heat treatment step is a step of heat treating the sulfide-based solid electrolyte in a battery having the sulfide-based solid electrolyte in a water-containing atmosphere with a dew point of −10° C. or higher. The heat treatment step yields a heat-treated product (roasted product). The heat-treated product (roasted product) means a product obtained by heat-treating a sulfide-based solid electrolyte or a battery having a sulfide-based solid electrolyte.

[0028] The water-containing atmosphere is not particularly limited and can be appropriately selected depending on the purpose, but an atmosphere in which water vapor is present in the roasting furnace is preferred.

[0029] The method of performing the heat treatment in the heat treatment step is not particularly limited and can be appropriately selected depending on the purpose. For example, the heat treatment can be performed by heating the battery having the sulfide-based solid electrolyte in a known roasting furnace in a water-containing atmosphere with a dew point of −10° C. or higher. The roasting furnace is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include batch furnaces such as rotary kilns, fluidized bed furnaces, tunnel furnaces and muffle furnaces, cupola furnaces and stoker furnaces. Among these, a batch furnace and a pusher-type continuous furnace are preferred, and it is also preferred to use a batch furnace and a pusher-type continuous furnace in combination.

[0030] <<Heat treatment conditions>> The conditions (heating conditions) for heat treating (heating) a sulfide-based solid electrolyte or a secondary battery containing a sulfide-based solid electrolyte are 70°C or higher, which is a temperature at which hydrogen sulfide is not released even when the sulfide-based solid electrolyte comes into contact with air after the heat treatment.

[0031] The atmosphere used for the heat treatment is not particularly limited as long as it is a water-containing atmosphere with a dew point of −10° C. or higher, and can be appropriately selected depending on the purpose. Examples include air, an inert atmosphere, a reducing atmosphere, and a low-oxygen atmosphere. The atmospheric atmosphere (air atmosphere) means an atmosphere using atmospheric air (air) containing about 21% by volume of oxygen and about 78% by volume of nitrogen. The inert atmosphere can be exemplified by an atmosphere consisting of nitrogen or argon. The reducing atmosphere means, for example, an atmosphere containing CO, H2, H2S, SO2, or the like in an inert atmosphere such as nitrogen or argon. The low-oxygen atmosphere means an atmosphere in which the oxygen partial pressure is 11% or less. Among these, it is preferable to use a low-oxygen atmosphere, since this can further improve the recovery rate and quality of valuable materials (e.g., aluminum) derived from the positive electrode current collector and valuable materials (e.g., copper) derived from the negative electrode current collector in a secondary battery containing a sulfide-based solid electrolyte.

[0032] The lower limit of the dew point is not particularly limited as long as it is -10°C or higher, and can be appropriately selected depending on the purpose. From the viewpoint of efficient processing, however, it is preferably -5°C or higher, more preferably 0°C or higher, and even more preferably 5°C or higher. The upper limit of the dew point is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficient processing, the upper limit is preferably 40°C or less, more preferably 30°C or less, even more preferably 20°C or less, particularly preferably 15°C or less, and most preferably 10°C or less. It is preferable that the numerical range has a lower limit value and an upper limit value that are either of the numerical values ​​shown as the lower limit value and either of the numerical values ​​shown as the upper limit value.

[0033] Among these, from the viewpoint of efficient processing, -10°C or higher and 40°C or lower are preferred, -10°C or higher and 20°C or lower are more preferred, 0°C or higher and 20°C or lower are even more preferred, and 0°C or higher and 10°C or lower are particularly preferred. The dew point can be measured by measuring the dew point of the atmosphere around the secondary battery during the heat treatment using a dew point meter.

[0034] The lower limit of the temperature of the water-containing atmosphere (heat treatment temperature) is 70°C or higher, but from the viewpoint of efficient treatment, 100°C or higher is preferred, 300°C or higher is more preferred, 500°C or higher is even more preferred, 700°C or higher is particularly preferred, and 800°C or higher is most preferred. The upper limit of the temperature of the water-containing atmosphere (heat treatment temperature) is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of efficient treatment, however, it is preferably 1,085°C or less, more preferably 1,000°C or less, and even more preferably 950°C or less. It is preferable that the numerical range has a lower limit value and an upper limit value that are either of the numerical values ​​shown as the lower limit value and either of the numerical values ​​shown as the upper limit value.

[0035] Among these, from the viewpoint of efficient treatment, 70°C or higher and 1,000°C or lower is preferred, 100°C or higher and 1,000°C or lower is more preferred, 300°C or higher and 1,000°C or lower is even more preferred, 500°C or higher and 1,000°C or lower is even more preferred, 700°C or higher and 1,000°C or lower is particularly preferred, and 800°C or higher and 950°C or lower is most preferred.

[0036] Heat treatment at 100°C or higher can convert the water in the roasting furnace into steam, further accelerating the decomposition of the sulfide-based solid electrolyte. Temperatures above 1,000°C can be disadvantageous in terms of energy efficiency issues in the heat treatment and the promotion of oxidation of valuable materials when treating secondary batteries containing sulfide-based solid electrolytes.

[0037] Furthermore, by raising the temperature of the battery itself containing a sulfide-based solid electrolyte to 660°C or higher, lithium cobalt oxide and lithium nickel oxide contained as positive electrode active materials can be thermally decomposed to form metal particles of cobalt and nickel, which can be easily recovered selectively as magnetic particles by magnetic separation. Furthermore, the copper and carbon binder of the negative electrode current collector can be thermally decomposed, making it easier to separate the carbon from the copper. Furthermore, by raising the temperature of the secondary battery itself containing a sulfide-based solid electrolyte to 660°C or higher, the aluminum of the positive electrode current collector can be embrittled, allowing it to be removed as a fine product by crushing and classification, and allowing the aluminum to be separated from the copper recovered as a coarse product.

[0038] The temperature of the battery itself having a sulfide-based solid electrolyte can be measured by inserting a thermometer such as a couple or a thermistor into the secondary battery at the heat treatment temperature.

[0039] The heat treatment time (the time for performing the heat treatment) is not particularly limited and can be appropriately selected depending on the purpose. For example, it can be a time that allows decomposition of the sulfide-based solid electrolyte and cessation of generation of hydrogen sulfide, and is preferably 1 minute or more and 10 hours or less, more preferably 3 minutes or more and 8 hours or less, and particularly preferably 5 minutes or more and 5 hours or less. The heat treatment time may be, for example, the time required for the sulfide-based solid electrolyte to reach the heat treatment temperature, or the holding time may be shorter. A heat treatment time of 1 minute or more and 10 hours or less is advantageous in that it can reduce the cost of the heat treatment and improve the efficiency of the heat treatment.

[0040] In the present invention, the binder resin and electrolyte in batteries containing a sulfide-based solid electrolyte can be sufficiently thermally decomposed. Additionally, aluminum, an example of a valuable material derived from the positive electrode current collector, can be sufficiently oxidized (embrittled), making it easier to separate from copper, an example of a valuable material derived from the negative electrode current collector, thereby further improving the recovery rate and quality of copper and aluminum. Furthermore, this heat treatment can convert lithium in Li(Ni / Co / Mn)O2 in the positive electrode active material and LiPF6 in the electrolyte into substances in which lithium is soluble in aqueous solutions, such as lithium fluoride (LiF), lithium carbonate (Li2CO3), and lithium oxide (Li2O). Furthermore, when aluminum is used in the outer packaging of secondary battery cells or in components of modules or packs, this aluminum can be melted and recovered. Specifically, by heat treating the secondary battery at 660°C or higher in the heat treatment process, aluminum contained in the secondary battery casing can be easily separated from other parts of the secondary battery (e.g., electrodes), allowing for convenient recovery of the aluminum derived from the casing. Furthermore, by melting and separating the aluminum, the contact efficiency between the sulfide-based solid electrolyte in the secondary battery and the moisture in the atmosphere is increased, and the sulfide-based solid electrolyte can be efficiently decomposed.

[0041] Furthermore, when the positive electrode current collector is aluminum (melting point: 660°C) and the negative electrode current collector is copper (melting point: 1,085°C), for example, by setting the heat treatment temperature to 750°C or higher and lower than 1,085°C, the positive electrode current collector formed of aluminum foil melts and becomes embrittled, making it easier to break down into fine particles in the crushing step described below. On the other hand, the negative electrode current collector formed of copper foil is heat treated at a temperature below the melting point of copper, so it does not melt. Therefore, the copper in the crushed product obtained by crushing the heat-treated product obtained in the heat treatment step remains in a shape similar to foil even after crushing, and can therefore be easily recovered as a coarse product in the classification step.

[0042] In order to heat-treat a sulfide-based solid electrolyte or a sulfide-based solid electrolyte in a battery having a sulfide-based solid electrolyte in a water-containing atmosphere with a dew point of −10° C. or higher, water can be supplied to the atmosphere during the heat treatment. By carrying out heat treatment in the presence of water in the atmosphere, the decomposition of the sulfide-based solid electrolyte (generation of hydrogen sulfide) can be promoted. The method for supplying water is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a method of performing heat treatment while supplying air having a predetermined dew point into a roasting furnace, a method of performing heat treatment while placing water in a roasting furnace, a method of performing heat treatment while spraying water into the roasting furnace, a method of performing heat treatment while supplying steam into the roasting furnace, a method of performing heat treatment in a heated steam atmosphere, and a method of performing heat treatment while immersing the sulfide-based solid electrolyte in a container containing water.

[0043] By performing the heat treatment in a water-containing atmosphere with a dew point of −10° C. or higher, the sudden generation of hydrogen sulfide that occurs when the sulfide-based solid electrolyte is treated by immersing it in water does not occur, and the decomposition reaction of the sulfide-based solid electrolyte can proceed slowly. Furthermore, by adjusting the dew point of the heat treatment atmosphere, the supply amount of a gas with a dew point adjustment, the heating temperature, the holding temperature, and the like, it is possible to perform the treatment while controlling the generation of hydrogen sulfide gas to a predetermined concentration or less. Furthermore, since the heat-treated product is sufficiently dry without coming into contact with water, no drying step is required to recover valuable materials.

[0044] <Other processes> The other steps are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include an exhaust gas treatment step, a crushing and classification step, a dry magnetic separation step, an air separation step, a slurrying step, a wet magnetic separation step, an acid leaching step, a neutralization step, a neutralized cake solid-liquid separation step, a calcium carbonate crystallization step, a calcium carbonate solid-liquid separation step, a concentration step, a calcium adsorption and removal step, and a lithium carbonate crystallization step. Among these, it is preferable to include a crushing and classification step, a slurrying step, a wet magnetic separation step, an acid leaching step, a neutralization step, and a neutralized cake solid-liquid separation step.

[0045] <<Exhaust gas treatment process>> The exhaust gas treatment step is a step of detoxifying harmful gases such as hydrogen sulfide gas, hydrogen fluoride gas, nitrogen oxides, sulfur oxides, dioxins, unburned organic gases, etc., which are generated in the heat treatment step. The exhaust gas treatment step is not particularly limited and can be appropriately selected depending on the purpose. Examples include detoxification treatment using a secondary combustion chamber, a quenching tower, a gas washing tower, a dust removal facility, a deodorization facility, etc. Among these, it is preferable to include a detoxification treatment using a secondary combustion chamber, a quenching tower, a gas washing tower, or a dust removal facility in order to more efficiently remove harmful gases from the exhaust gas.

[0046] <<<Secondary combustion chamber>>> The secondary combustion chamber is a facility that completely burns harmful gases such as H2S and CO contained in the exhaust gas generated from the furnace and converts them into SO2 and CO2, thereby reducing or neutralizing the harmfulness of the exhaust gas. The treatment conditions are not particularly limited and can be selected appropriately depending on the purpose, but it is preferable that the oxygen concentration in the secondary combustion chamber is 15% or more, the temperature is 850° C. or more, and the residence time is 2 seconds or more.

[0047] <<<Quenching Tower>>> The quenching tower is a facility that rapidly cools the exhaust gas generated from the furnace to suppress the generation of dioxins. The cooling method is not particularly limited and can be appropriately selected depending on the purpose. For example, a water spray method or a waste heat boiler method can be used. The treatment conditions are not particularly limited and can be selected appropriately depending on the purpose, but it is preferable to reduce the temperature of the exhaust gas generated from the furnace to 200°C or less at the outlet of the quenching tower within 3 seconds.

[0048] <<<Gas scrubber>>> The gas scrubber is a facility that uses chemicals to remove harmful gases such as SO2, HCl, Cl2, and HF contained in the exhaust gas generated from the furnace. The agent is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include water, an aqueous sodium hydroxide solution, slaked lime powder, activated carbon powder, and the like.

[0049] <<<Dust removal equipment>>> The dust removal equipment is equipment that removes dust components contained in the exhaust gas generated from the furnace. The dust components include S, Cl, F, and the like. The removal method is not particularly limited and can be appropriately selected depending on the purpose. Examples include a bag filter and an electric dust collector.

[0050] <<<Deodorizing equipment>>> The deodorizing device is a facility that removes the odor of exhaust gas generated from the furnace. The deodorizing method is not particularly limited and can be appropriately selected depending on the purpose. Examples include combustion method, biological deodorizing method, ozone oxidation method, catalytic decomposition method, adsorption method, washing method, adsorptive decomposition method, chemical capture method, and deodorizer method.

[0051] <<<Reaction of hydrogen sulfide in exhaust gas treatment processes>>> The hydrogen sulfide gas generated from the furnace is converted into sulfur dioxide, sulfur trioxide, and other SO in the secondary combustion chamber. x is oxidized to produce water. The exhaust gas temperature is cooled to below 200°C in the quenching tower, and the gas is removed using cleaning agents in the washing tower. Generally, SO x is more soluble in water than hydrogen sulfide and can be removed from exhaust gases more efficiently.

[0052] <<Crushing / classification process>> The crushing and classification step is a step of crushing the heat-treated product obtained in the heat treatment step and classifying the crushed product to obtain a coarse product and a fine product containing the valuable material.

[0053] <<<Crushing and classification process (crushing treatment)>>> The crushing and classification step (crushing treatment) includes a treatment of crushing the heat-treated material (secondary batteries that have been heat-treated) to obtain crushed material. The crushing treatment is not particularly limited as long as it can crush the heat-treated product (roasted product) to obtain a crushed product, and can be appropriately selected depending on the purpose. Furthermore, the crushed product means a product obtained by crushing the heat-treated product.

[0054] As a crushing method, for example, it is preferable to crush the heat-treated product by impact to obtain crushed products. Furthermore, if the outer container of the secondary battery does not melt during the heat treatment, it is more preferable to pre-crush the heat-treated product by cutting it with a cutter before applying an impact to the heat-treated product.

[0055] The crushing process may be performed wet. In this case, the loss of positive and negative electrode active materials such as carbon, cobalt, and nickel due to scattering during crushing can be prevented, and the dust collection device required to prevent this loss can be eliminated. Furthermore, all of the water-soluble lithium in the heat-treated product can be recovered in water at the time of the crushing process.

[0056] Examples of methods for crushing by impact include a method in which the heat-treated material is thrown by a rotating striking plate and slammed against a collision plate to apply an impact, and a method in which the heat-treated material is hit by a rotating striker (beater), and this can be done using, for example, a hammer crusher. Another method for crushing by impact is a method in which the heat-treated material is hit by ceramic or other balls, and this method can be done using a ball mill, for example. Impact crushing can also be done using, for example, a biaxial crusher with short blade width and length that crushes by compression. Furthermore, examples of methods for crushing by impact include a method in which the heat-treated material is hit with two rotating chains to apply impact, and this can be done, for example, by a chain mill.

[0057] Crushing the heat-treated material by impact promotes crushing of the positive electrode current collector (e.g., aluminum (Al)), but the negative electrode current collector (e.g., copper (Cu)), whose shape has not changed significantly, exists in a form such as foil. Therefore, in the crushing process, the negative electrode current collector is merely cut into pieces, and thus, in the classification process described below, crushed material can be obtained in a state in which valuable materials derived from the positive electrode current collector (e.g., aluminum) and valuable materials derived from the negative electrode current collector (e.g., copper (Cu)) can be efficiently separated.

[0058] The crushing time in the crushing process is not particularly limited and can be selected appropriately depending on the purpose, but the crushing time per 1 kg of secondary batteries is preferably from 1 second to 30 minutes, more preferably from 2 seconds to 10 minutes, and particularly preferably from 3 seconds to 5 minutes.

[0059] <<<Crushing and classification process (classification treatment)>>> The crushing and classification step (classification treatment) includes a treatment of obtaining a coarse product and a fine product containing valuable materials by classifying the crushed material. The classification treatment is not particularly limited as long as it can classify the crushed material to obtain a coarse product (matter that passes the sieve) and a fine product (matter that passes the sieve), and can be appropriately selected depending on the purpose.

[0060] The classification method is not particularly limited and can be appropriately selected depending on the purpose, and can be carried out using, for example, a vibrating sieve, a multistage vibrating sieve, a cyclone, a standard sieve according to JIS Z8801, etc. By classification, copper (Cu), iron (Fe), etc. can be separated into a coarse-grained product, and lithium, cobalt, nickel, or carbon (graphite) can be concentrated in a fine-grained product.

[0061] The classification process may be performed wet. In this case, it is possible to prevent the scattering of positive and negative electrode active materials such as carbon, cobalt, and nickel during crushing, and it is possible to eliminate the need for a dust collector to prevent this loss. The crushed material may be conditioned to prevent scattering before classification. As a method for humidifying, water may be sprayed in a mist form. This prevents the scattering of carbon, cobalt, and nickel when water is sprayed on the crushed material.

[0062] There are no particular restrictions on the particle size of the classification (classification point, sieve opening) and it can be selected appropriately depending on the purpose. If the purpose of classification is to separate copper, iron, aluminum, etc. into a coarse product and concentrate lithium, cobalt, nickel, etc. into a fine product, the particle size of the classification is preferably 0.6 mm or more and 2.4 mm or less, and more preferably 0.85 mm or more and 1.7 mm or less. If the particle size of the classification is 2.4 mm or less, it is possible to prevent copper, iron, aluminum, etc. from being mixed into the fine product. If the particle size of the classification is 0.6 mm or more, it is possible to prevent lithium, cobalt, nickel, etc. from being mixed into the coarse product.

[0063] Furthermore, when a sieve is used as a classification method, by placing stainless steel balls or alumina balls, for example, on the sieve as a crushing promoter, the small crushed pieces adhering to the large crushed pieces can be separated from the large crushed pieces, thereby enabling more efficient separation of the large crushed pieces from the small crushed pieces, thereby further improving the quality of the recovered metal. The crushing and classification processes can be carried out simultaneously. For example, the heat-treated product obtained in the heat treatment process can be crushed while the crushed product is classified into a coarse product and a fine product in a crushing-classification process (crushing and classification).

[0064] The classification into coarse and fine products may be repeated several times, and this reclassification can further reduce the impurity content of each product. For example, from the viewpoint of improving the quality of cobalt (Co) and nickel (Ni) in the fine product, for example, by performing two-stage sieving at classification points of over 1.2 mm and 0.3 to 1.2 mm, secondary battery components such as copper or iron having a larger average particle size than cobalt and nickel can be separated onto the sieve in the first stage, cobalt and nickel that have not been sufficiently liberated from the copper of the negative electrode current collector or the aluminum of the positive electrode current collector are recovered onto the sieve in the second stage, and cobalt, nickel, and carbon are recovered below the sieve. The second-stage sieve-surface material may be crushed again to promote liberation of the cobalt and nickel from the aluminum, and then sieved again to recover the cobalt and nickel below the sieve.

[0065] <<Dry magnetic separation process>> The dry magnetic separation step is a step in which the coarse-grained product is subjected to dry magnetic separation (dry magnetic separation) after the classification step, thereby separating the coarse-grained product into magnetized and non-magnetized materials. The dry magnetic separation step is not particularly limited as long as it is a step that can separate the coarse product into magnetized matter and non-magnetized matter by dry magnetic separation, and can be appropriately selected depending on the purpose. Among these, it is preferable to subject the coarse product to dry magnetic separation (dry magnetic separation) to recover copper (copper concentrate) from non-magnetic materials.

[0066] The dry magnetic separation step can be carried out using a known magnetic separator (magnetic separator) or the like. The magnetic separator is not particularly limited and can be appropriately selected depending on the purpose. Examples include a bar magnet, a hand magnet, a lattice magnet, a rotary magnet, a magnetic strainer, a high magnetic pulley (magnetic pulley) magnetic separator, and a hanging magnetic separator.

[0067] The magnetic force used in the dry magnetic separation step can be selected appropriately depending on the material to be separated. For example, when separating iron, a magnetic force of 0.01 T (tesla) or more and 0.3 T or less is preferable. When separating stainless steel, a magnetic force higher than the above range may be used. It is also possible to combine different magnetic forces and use them in multiple stages. In this way, it is possible to selectively recover magnetized materials such as iron and stainless steel and non-magnetized materials such as copper.

[0068] <<Wind sorting process>> The wind sorting process is a process in which the valuables separated in the magnetic separation process are separated into one valuable element such as copper and another valuable element such as aluminum by wind power. The wind sorting process is performed, for example, on non-magnetic materials separated in the magnetic separation process and containing multiple types of valuable elements, and separates one valuable element from the other valuable elements by wind power. Note that hereinafter, sorting by wind power may be referred to as "wind sorting."

[0069] Here, the one valuable item sorted in the air sorting process may contain at least one valuable item, and may also contain components other than the one valuable item. Similarly, the other valuable items sorted in the air sorting process may contain at least other valuable items, and may also contain components other than the other valuable items. In other words, when sorting the one valuable item and other valuable items contained in the valuable items sorted in the magnetic sorting process in the air sorting process, it is sufficient that the valuable items can be sorted into those containing at least the one valuable item and those containing the other valuable items. Furthermore, the purity of the one valuable material sorted in the air sorting process is preferably, for example, 80% by mass or more, and more preferably 99% by mass or more. For example, if the purity of the one valuable material is 99% by mass or more, the sorted one valuable material can be sold at a higher price. Furthermore, the purity of the other valuable materials sorted in the air sorting process is preferably, for example, 95% by mass or more.

[0070] The method for carrying out the air separation step is not particularly limited as long as it is a method that can separate one valuable resource from another valuable resource by air force, and can be appropriately selected depending on the purpose.

[0071] In the air sorting step, it is preferable to separate one valuable resource from another valuable resource by, for example, allowing the valuable resources sorted in the magnetic sorting step to fall and blowing air in a direction intersecting the falling direction of the valuable resources as the valuable resources are allowed to fall. In other words, in the valuable resource recovery method of the present invention, it is preferable to separate the valuable resources in the air sorting step by allowing the valuable resources to fall and blowing air in a direction intersecting the falling direction of the valuable resources as the valuable resources are allowed to fall. In this way, the difference in specific gravity and shape between the one valuable item and the other valuable items can be utilized to separate the one valuable item from the other valuable items with higher accuracy.

[0072] When sorting by blowing wind in a direction intersecting the direction in which the valuables fall, more specifically, for example, when the valuables are dropped, it is preferable to blow wind upward in a direction approximately opposite to the direction in which the valuables fall, causing them to come into contact with each other, allowing one valuable item contained in the valuables to fall as is and be sorted (recovered), and then transporting the other valuable items contained in the valuables by the wind and sorting (recovering) them. Here, the angle (crossing angle) between the falling direction of the valuables (direction of falling) and the blowing direction of the wind (direction of wind movement) is not particularly limited as long as the falling direction of the valuables and the blowing direction of the wind intersect, and can be appropriately selected depending on the purpose. Furthermore, by making the crossing angle large, the angle between the respective moving directions of one valuable and another valuable after the wind has been blown can be made large, which is preferable because it allows for efficient separation of both. Specifically, the crossing angle is preferably greater than 0° and 180° or less, more preferably 70° or more and 180° or less, even more preferably 90° or more and 180° or less, and particularly preferably 135° or more and 180° or less. Furthermore, when sorting valuables by blowing wind in a direction intersecting the direction in which the valuables fall, conditions such as the wind speed can be set appropriately depending on the type of valuables, etc., so that one valuable item can be sorted from another valuable item.

[0073] When sorting one valuable resource from another valuable resource by blowing air in a direction intersecting the direction in which the valuable resources fall, for example, a known wind power sorter can be used. The air sorter is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a closed-type air sorter. A diffuser may also be installed as appropriate to control the shape of the blown air.

[0074] <<Slurrying process>> The slurrying step is a step in which the fine product obtained in the crushing and classification step is immersed in water to form a fine product slurry. The slurrying step is not particularly limited as long as it is a step in which the finely divided product recovered in the crushing and classification step can be immersed in water to obtain a slurry, and can be appropriately selected depending on the purpose. When the crushing step or the classification step is carried out in a wet manner, the crushing step or the classification step may be a slurrying step.

[0075] The water for leaching the fine granule product is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include industrial water, tap water, ion-exchanged water, pure water such as ultrafiltrated water, reverse osmosis water, distilled water, and ultrapure water, etc. Among these, it is preferable to use ion-exchanged water because the production cost is relatively low and the concentration of potassium, which becomes an impurity in lithium carbonate, is low.

[0076] The method for forming a fine particle slurry in the slurrying step is not particularly limited and can be selected appropriately depending on the purpose, and examples include a method of simply putting the fine particle product into water, a method of putting the fine particle product into water and stirring, a method of putting the fine particle product into water and gently stirring while applying ultrasonic waves, a method of adding water to the fine particle product, a method of spraying water in a mist on the fine particle product to adjust the humidity before putting it into water, etc. The method of putting the fine particle product into water and stirring is preferred, and the method of spraying water in a mist on the fine particle product to adjust the humidity before putting it into water is more preferred. This method enables magnetic separation while preventing dust generation from the fine particle product.

[0077] The solid-liquid ratio in the slurrying step is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 5% to 67%, more preferably 10% to 40%. If the solid-liquid ratio is less than 5%, the concentration of lithium dissolved in the leachate decreases, which tends to reduce the lithium recovery rate and concentration efficiency. If the solid-liquid ratio exceeds 67%, the lithium leaching rate into water may decrease, and if the slurry is sent to the next step without dilution, problems such as pipe clogging may occur. Furthermore, if the slurry is supplied to the wet magnetic separation step described below, the recovery rate of cobalt and nickel on the magnetized material and the recovery rate of carbon on the non-magnetized material may decrease (i.e., the separation performance of cobalt and nickel from carbon may decrease).

[0078] The stirring speed of the slurry in the slurrying step is not particularly limited and can be appropriately selected depending on the purpose, and can be, for example, 400 rpm. The stirring time in the slurrying step is not particularly limited and can be appropriately selected depending on the purpose, and can be, for example, 1 hour.

[0079] <<Wet magnetic separation process>> The wet magnetic separation step is a step of separating the fine product slurry obtained in the slurrying step into a magnetic material and a non-magnetic material slurry by wet magnetic separation. Note that the "non-magnetic material slurry" refers to a suspension containing non-magnetic materials. The wet magnetic separation step is not particularly limited as long as it is a step that can separate the fine product slurry into a magnetic material slurry and a non-magnetic material slurry by wet magnetic separation, and can be appropriately selected depending on the purpose. In the present invention, by separating the cobalt and nickel as the magnetized materials from the non-magnetized material slurry, the amounts of acid and neutralizing agent used can be reduced by the amounts consumed by the cobalt and nickel during acid leaching.

[0080] The magnetically separated material has high cobalt and nickel grades and low impurity grades, and therefore the cobalt and nickel obtained in the wet magnetic separation process do not require additional Co and Ni concentration processes such as acid leaching, neutralization, or solvent extraction, and can be used as raw materials (e.g., cobalt sulfate, nickel sulfate, etc.) for obtaining secondary battery manufacturing materials or as raw materials for smelting cobalt and nickel. The lithium in the magnetized material may be recovered as lithium carbonate or lithium hydroxide in the process of obtaining the manufacturing materials for these secondary batteries or in the process of obtaining raw materials for smelting cobalt and nickel. By recovering the lithium in the magnetized material, 10 mass % or more of the lithium contained in the secondary battery can be recovered as lithium carbonate or lithium hydroxide.

[0081] The magnetic material refers to an object that can be attracted to a magnetic source (e.g., a magnet, an electromagnet, etc.) by the magnetic force generated by the magnetic source. Examples of the magnetic material include ferromagnetic metals. Examples of ferromagnetic metals include iron (Fe), nickel (Ni), and cobalt (Co).

[0082] The non-magnetic material refers to a material that is not attracted to the magnetic source by the magnetic force generated by the magnetic source. There are no particular limitations on the non-magnetic material, and it can be selected according to the purpose. Examples of non-magnetic metallic materials include paramagnetic or semi-magnetic metals. Examples of paramagnetic or semi-magnetic metals include aluminum (Al), manganese (Mn), gold (Au), silver (Ag), and copper (Cu). Examples of components other than metals include carbon (C) such as graphite, silicon (Si), aluminum oxide, and lithium aluminate.

[0083] The wet magnetic separation step 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 depending on the purpose. Examples include a drum-type magnetic separator and a high-gradient magnetic separator.

[0084] The conditions for wet magnetic separation when carrying out the wet magnetic separation step are not particularly limited and can be appropriately selected depending on the purpose.

[0085] In the wet magnetic separation step, for example, cobalt (Co), nickel (Ni), manganese (Mn) integrated with cobalt, and the like are recovered as magnetic substances. When the fine product obtained in the crushing and classification step is magnetically separated, for example, by dry magnetic separation, the particles may aggregate due to the moisture adhering between the particles, and the metal particles derived from the negative electrode current collector, and the fine particles of negative electrode active material contained in the fine product at 10% or more, and the cobalt and nickel particles may not be sufficiently separated. For this reason, in the present invention, it is preferable to separate the material derived from the negative electrode active material and the metal derived from the negative electrode current collector into a non-magnetized material slurry in the wet magnetic separation step, and recover the cobalt and nickel as magnetized materials.

[0086] The solid-liquid ratio of the slurry supplied to the wet magnetic separation is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 5% to 67%, more preferably 10% to 40%. If the solid-liquid ratio is less than 5%, the recovery rate of cobalt and nickel as magnetic substances in the wet magnetic separator may decrease. If the solid-liquid ratio exceeds 67%, problems such as pump clogging during slurry supply may occur, and the separation performance of cobalt and nickel (magnetic substances) from non-magnetic substances such as carbon may decrease. The slurry may be the fine product slurry obtained in the slurrying step as is, or the fine product slurry obtained in the slurrying step may be concentrated or diluted by solid-liquid separation such as sedimentation to adjust the solid-liquid ratio. Alternatively, the fine product slurry may be diluted with water to adjust the solid-liquid ratio.

[0087] The method for supplying the slurry is not particularly limited and can be appropriately selected depending on the purpose, but the slurry in the tank may be supplied by a pump while being stirred. 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 attract fine cobalt and nickel particles, and the recovery rate of cobalt and nickel into the magnetized material may tend to decrease. On the other hand, if the magnetic field strength exceeds 20,000 G, the recovery rate of impurities other than cobalt and nickel into the magnetized material may increase, and the cobalt and nickel grade in the magnetized material may decrease.

[0088] Since the magnetic material recovered in the wet magnetic separation step contains moisture, the moisture may be removed by solid-liquid separation using filter paper, a filter press, a centrifuge, or the like, by air drying, or by heat drying in a dryer. The obtained magnetized material may be washed with water and then subjected to solid-liquid separation. In this case, the fluorine that was not removed from the magnetized material in the slurrying step can be reduced to, for example, less than 1%. For example, when a filter press is used as the solid-liquid separator, this water washing can be carried out by pouring water into the filter chamber containing the magnetized material in the filter press. As for the weight of water used for water washing, it is preferable to pass 0.1 kg or more of water per 1 kg of acid leaching residue, and it is particularly preferable to pass 1 kg or more of water.

[0089] The wet magnetic separation step may be performed multiple times (multiple stages). For example, the cobalt (Co) quality of the magnetized material can be improved by performing a second stage of wet magnetic separation (cleaning) on ​​the magnetized material recovered in the first stage of wet magnetic separation. In this case, the conditions for the second stage of wet magnetic separation may be different from those for the first stage. By setting conditions that make recovery of the magnetized material more difficult than in the first stage of wet magnetic separation (e.g., low magnetic field strength, high magnetic separator drum rotation speed, high feed rate, etc.), the cobalt (Co) quality of the magnetized material recovered in the second stage of wet magnetic separation can be made higher than the cobalt (Co) quality of the magnetized material recovered in the first stage of wet magnetic separation. Furthermore, the recovery rate of carbon (C) recovered as a non-magnetized material slurry can be improved compared to when a single stage of wet magnetic separation is performed. As another example, the cobalt (Co) content of the non-magnetized material slurry recovered in the first-stage wet magnetic separation step can be reduced by performing a second-stage wet magnetic separation (cleaning separation) on the non-magnetized material slurry. In this case, the conditions for the second-stage wet magnetic separation can be different from those for the first-stage wet magnetic separation. By setting conditions that facilitate easier recovery of magnetized material compared to the first-stage wet magnetic separation (e.g., high magnetic field strength, low magnetic separator drum rotation speed, low feed rate, etc.), the cobalt content of the non-magnetized material slurry recovered in the second-stage wet magnetic separation can be reduced compared to the cobalt content recovered in the first-stage wet magnetic separation. Furthermore, the recovery rate of cobalt recovered as magnetized material can be improved compared to when a single-stage wet magnetic separation is performed. Water may be added to the non-magnetized material slurry obtained in the wet magnetic separation. Adjusting the lithium (Li) concentration can prevent lithium loss to the neutralization residue, as described in the neutralization step below.

[0090] <<Acid leaching process>> The acid leaching step is a step in which sulfuric acid is added to the non-magnetized material slurry and / or the non-magnetized materials obtained by solid-liquid separation of the non-magnetized material slurry, the non-magnetized materials are leached, and then solid-liquid separation is performed to obtain an acid leaching solution and an acid leaching residue. The acid leaching solution contains dissolved lithium from water-soluble sources such as lithium carbonate, lithium fluoride, and lithium oxide, as well as lithium from the poorly water-soluble LiAlO2 (lithium aluminate).The acid leaching residue contains concentrated, high-quality carbon (C), which can be recovered and used as a carbon (C) concentrate. The acid leaching solution and the acid leaching residue (carbon concentrate) are preferably subjected to solid-liquid separation using, for example, filter paper, a filter press, or a centrifuge.

[0091] In the acid leaching step, sulfuric acid is used as the acid solution. The concentration of the added sulfuric acid is preferably 5% by mass or more and 90% by mass or less, more preferably 10% by mass or more and 80% by mass or less. By using sulfuric acid with such a concentration, heat generation from the acid solution (including sulfuric acid derived from the added sulfuric acid as well as hydrofluoric acid derived from the fluorine in the electrolyte of the secondary battery) in the acid leaching step and deterioration of the tank used for leaching can be suppressed.

[0092] The pH of the acid solution used in the acid leaching step is preferably 0 to 3.5, more preferably 0 to 3, even more preferably 1 to 3, and particularly preferably 1.5 to 2.5. If the pH exceeds 3.5, the lithium aluminate in the filtration residue will not dissolve effectively. Here, the pH of the acid solution refers to the pH at the end of the acid leaching step. If the pH of the acid solution is 0 to 3.5, 80% or more of the lithium in the non-magnetized material can be leached, and a carbon concentrate (acid leaching residue) with a carbon content of 80% or more can be obtained. A pH of 0 to 3 is preferable because it allows lithium to be leached with a reduced amount of acid added without decreasing the acid leaching rate of lithium compared to pH 0. A pH of 1.5 to 2.5 is particularly preferable because it allows lithium to be leached without decreasing the acid leaching rate compared to pH 0, and it also suppresses the leaching of copper contained in the non-magnetized material slurry, resulting in an acid leaching solution with a lower impurity concentration. The copper contained in the acid leaching residue (carbon concentrate) may not cause problems when used as a smelting raw material (reducing agent). Furthermore, by performing acid leaching with the addition of an oxidizing agent to the acid leaching residue, copper can be removed into the leachate, making it possible to recover a higher-quality carbon concentrate. If the pH is less than 0, the concentration of sulfate ions in the acid leaching solution will be high, resulting in a large loss of lithium into the neutralization cake produced during the neutralization step.

[0093] The lithium concentration and sulfate ion concentration of the acid leaching solution are preferably less than 4,000 mg / L and 60,000 mg / L or less, respectively, in order to reduce the loss of lithium due to coprecipitation and adsorption caused by the generation of a large amount of neutralization cake in the neutralization step.

[0094] The leaching method in the acid leaching step is not particularly limited and can be selected appropriately depending on the purpose, and examples include a method of simply adding the non-magnetized material slurry to acid, a method of adding the non-magnetized material slurry to acid and stirring, a method of adding the non-magnetized material slurry to acid and stirring, a method of adding acid to the non-magnetized material slurry, and a method of adding acid to the non-magnetized material slurry and then stirring.As an acid leaching method, for example, a method of adding acid to the non-magnetized material slurry is preferred, and a method of adding acid to the non-magnetized material slurry and then stirring is more preferred.By adding acid to the non-magnetized material slurry, it is possible to suppress local temperature increases and bumping due to heat generated when the non-magnetized material reacts with the acid.

[0095] The stirring speed of the sulfuric acid in the acid leaching step is not particularly limited and can be appropriately selected depending on the purpose, and can be, for example, 200 rpm.

[0096] The liquid temperature during acid leaching is preferably 0°C or higher and 80°C or lower, more preferably 10°C or higher and 60°C or lower.

[0097] An oxidizing agent may be added during acid leaching. The addition of an oxidizing agent promotes the dissolution of impurities (e.g., copper) that are difficult to dissolve in acid, such as copper, and can further improve the carbon (C) quality of the carbon (C) concentrate (acid leaching residue). The oxidizing agent is not particularly limited and can be appropriately selected depending on the purpose. Examples of the oxidizing agent include hydrogen peroxide, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, halogens, permanganates, ozone, and air.

[0098] The leaching time in the acid leaching step is not particularly limited and can be appropriately selected depending on the purpose, and can be, for example, 1 hour.

[0099] The carbon (C) content of the acid leaching residue obtained in the acid leaching step is preferably 80% or more, more preferably 90% or more. Furthermore, when the acid leaching residue (carbon (C) concentrate) is used as a reducing agent in smelting, phosphorus (P) is an element that should be avoided in steel smelting, and fluorine (F) is an element that places a burden on the treatment of exhaust gases from smelting. Therefore, it is preferable to remove phosphorus and fluorine as much as possible from the acid leaching residue (carbon (C) concentrate). Furthermore, carbon (C) concentrate contains copper (Cu) as a major impurity, which can be separated by dispersing the carbon with a dispersant and allowing the copper to settle, flotation to recover the copper as tailings, or gravity separation to recover the copper as heavy products.

[0100] Water may be added to the acid leaching solution obtained in the acid leaching step to adjust the lithium (Li) concentration in the acid leaching solution. By reducing the lithium (Li) concentration, it is possible to prevent the loss of lithium (Li) to the purified solution residue, as will be described later in the neutralization step. The acid leaching residue may be washed with water, or may be subjected to solid-liquid separation after washing. The acid leaching residue may contain an acidic solution, and washing with water can reduce the amount of this acidic solution. For example, when sulfuric acid is used as the acidic solution, the sulfuric acid content of the acid leaching residue can be reduced by washing the acid leaching residue with water and then performing solid-liquid separation. When a filter press is used as the solid-liquid separator, this washing can be carried out by pouring water into the filter chamber containing the acid leaching residue within the filter press. The weight of water used for washing is preferably 0.1 kg or more, and more preferably 1 kg or more, of water per 1 kg of acid leaching residue.

[0101] <<Neutralization process>> The neutralization step is a step of neutralizing the acid leaching solution obtained in the acid leaching step. The neutralization step aims to neutralize the acid leachate and solidify (form a neutralized cake) impurity ions other than lithium (Li) (e.g., boron ions, fluorine ions, sulfate ions, cobalt ions, nickel ions, aluminum ions, copper ions, etc.), and separate them by solid-liquid separation.

[0102] The neutralization can be carried out using a neutralizing agent (alkali). The neutralizing agent (alkali) is not particularly limited and can be appropriately selected depending on the purpose. Examples include calcium hydroxide (Ca(OH)2; slaked lime), calcium carbonate, calcium oxide, calcium aluminate, and calcium phosphate. Among these, calcium carbonate is preferred. These may be used alone or in combination of two or more.

[0103] Adding calcium hydroxide to an acid leachate containing sulfate and aluminum ions can reduce the boron ion concentration in the neutralized solution to less than 0.1 mg / L. This is thought to be due to the boron removal mechanism, which involves the ettringite-forming reaction between aluminum sulfate and calcium hydroxide, or the hydroxyapatite-forming reaction between phosphorus and ammonia ions (presumably derived from aluminum nitride generated by heat treatment) in the leachate and calcium hydroxide. To remove boron, the leachate should preferably contain 500 mg / L or more of aluminum ions, 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 product during acid leaching. Furthermore, this reaction can reduce the phosphorus concentration in the neutralized solution to 1 mg / L, thereby reducing the phosphorus content of the recovered lithium carbonate to less than 10 ppm.

[0104] The neutralization step may include neutralization at multiple pH levels and multiple solid-liquid separation steps. For example, the first-stage neutralization may be performed at pH 9, and the liquid obtained by the first-stage solid-liquid separation may be raised in pH to 12 (second-stage neutralization) before undergoing second-stage solid-liquid separation.

[0105] By adding an aluminum compound such as aluminum sulfate, calcium aluminate, aluminum chloride, or aluminum hydroxide before adding the alkali, the amount of boron removed may be further reduced compared to when the alkali is used alone. The alkali may be added in the form of a solid or a slurry.

[0106] Sulfate ions and calcium ions produce calcium sulfate, so the sulfate ions can be separated as a solid (calcium sulfate) by solid-liquid separation.

[0107] The lower limit of the pH after neutralization is not particularly limited as long as it is pH 9.5 or higher, and can be appropriately selected depending on the purpose. However, in order to reliably achieve a zinc content of less than 10 ppm, a manganese content of 10 ppm, and a magnesium content of 10 ppm in the obtained lithium carbonate, the pH is preferably pH 9.8 or higher, more preferably pH 10.0 or higher, and even more preferably pH 10.1 or higher. The upper limit of the pH after neutralization is not particularly limited as long as it is less than pH 11.5, and can be appropriately selected depending on the purpose. However, in order to reduce the loss of lithium to the neutralized precipitate that accompanies an increase in the amount of neutralized precipitate generated in the resulting lithium carbonate, the pH is preferably 11.0 or less, more preferably 10.5 or less, and even more preferably 10.4 or less. It is preferable that the numerical range has a lower limit value and an upper limit value that are either of the numerical values ​​shown as the lower limit value and either of the numerical values ​​shown as the upper limit value.

[0108] Among these, in order to reliably achieve a zinc content of less than 10 ppm, a manganese content of 10 ppm, and a magnesium content of 10 ppm in the obtained lithium carbonate, as well as to reduce the loss of lithium to the neutralized precipitate that accompanies an increase in the amount of neutralized precipitate generated, the pH is preferably 9.8 or higher and 11.0 or lower, more preferably 10.0 or higher and 10.5 or lower, even more preferably 10.0 or higher and 10.4 or lower, and particularly preferably 10.1 or higher and 10.4 or lower. Here, the pH of the solution means the pH at the end of the neutralization step.

[0109] 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, relative to 100% by mass of the lithium content contained in the fine particle product. Water may be added to the slurry obtained in the neutralization step or the liquid obtained by solid-liquid separation of the slurry to adjust the lithium concentration of the slurry or the liquid. By reducing the lithium (Li) concentration, loss of lithium (Li) can be prevented.

[0110] <<Neutralization cake solid-liquid separation process>> The neutralized cake solid-liquid separation step is a step of separating the neutralized liquid obtained in the neutralization step into solid and liquid. The solid-liquid separation method is not particularly limited and can be appropriately selected depending on the purpose, but solid-liquid separation techniques such as 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 are preferred, and among these, pressure filtration is particularly preferred. By using pressure filtration, the water content in the cake can be more efficiently reduced than other filtration methods such as suction filtration, and the loss of lithium into the neutralized cake can be reduced. Furthermore, by passing water through the neutralized cake in the pressure filter, lithium contained in the water in the neutralized cake can be recovered in the passing water.

[0111] <<Calcium carbonate crystallization process>> The calcium carbonate crystallization step is a step of adding CO2 to the liquid obtained in the neutralized cake solid-liquid separation step. The liquid obtained in the neutralized cake solid-liquid separation step contains calcium ions at approximately 100 mg / L to 1,000 mg / L. This dissolved calcium reacts with CO2 in the air, crystallizing calcium carbonate. If this liquid is subjected to a calcium adsorption and removal step, the efficiency of calcium adsorption and removal may decrease due to blockage of the resin tower or adhesion of calcium carbonate to the resin surface. For this reason, in the calcium carbonate crystallization step, CO2 is added to the liquid obtained in the neutralized cake solid-liquid separation step to crystallize calcium as calcium carbonate, thereby reducing the amount of dissolved calcium.

[0112] The method of adding CO2 is not particularly limited and can be selected appropriately depending on the purpose. Examples include a method of adding a gas containing CO2, such as air, to the liquid, or a method of adding a carbonate, such as sodium carbonate. Methods for adding a CO2-containing gas include, for example, simply leaving the liquid standing in a CO2-containing gas, diffusing a CO2-containing gas into the liquid, and stirring the liquid while blowing a CO2-containing gas into it.

[0113] The amount of CO2 added is preferably such that the molar ratio relative to calcium ions in the liquid obtained in the neutralized cake solid-liquid separation step is 0.1 or more and the molar ratio relative to lithium ions is 0.5 or less, more preferably 0.5 or more and 0.25 or less, and particularly preferably 0.8 or more and 0.1 or less. By supplying CO2 at a molar ratio relative to calcium ions of 0.1 or more, calcium ions can be crystallized as calcium carbonate. Furthermore, by supplying CO2 at a molar ratio relative to lithium ions of 0.5 or less, crystallization of lithium carbonate can be prevented in the calcium carbonate crystallization step, calcium adsorption and removal step, and concentration step.

[0114] <<Calcium carbonate solid-liquid separation process>> The calcium carbonate solid-liquid separation step is a step of subjecting the liquid obtained in the calcium carbonate crystallization step to solid-liquid separation and removing calcium carbonate from the liquid. The solid-liquid separation method is not particularly limited and can be appropriately selected depending on the purpose. Examples of solid-liquid separation methods include suction filtration using filter paper or the like, pressure filtration using a filter press or the like, and centrifugation using a centrifuge or the like. Among these, pressure filtration is particularly preferred. By using pressure filtration, the water content in the neutralized cake can be more efficiently reduced than with other filtration methods such as suction filtration, and the loss of lithium in the neutralized cake can be reduced. Water may be added to the neutralized cake during or after solid-liquid separation to leach and recover lithium.

[0115] <<Concentration process>> The method for recovering valuable materials of the present invention may include, after the calcium carbonate crystallization step, a concentration step of concentrating lithium contained in the solution obtained in the calcium carbonate crystallization step by electrodialysis. The concentration step is preferably carried out before the calcium adsorption and removal step described below.

[0116] By including the concentrating step, for example, the lithium concentration in the solution can be increased to a concentration that allows lithium carbonate to be easily crystallized in the lithium carbonate crystallization step. In the concentration step, the concentration is performed by electrodialysis, which can increase the lithium carbonate production rate by more than five times compared to evaporation concentration using equipment of the same scale. In addition, although a small amount of lithium is dissolved in the dilute solution recovered by electrodialysis, by using the lithium again in the slurrying step, it is possible to recover the lithium and reduce the amount of water used.

[0117] When calcium ions are contained in the raw material solution, the calcium ions may be adsorbed onto the ion exchange membrane of the electrodialysis device, causing a problem of clogging the membrane. However, by applying the concentration process to the solution after the calcium carbonate separation process (the solution in which calcium has been reduced to 10 mg / L or less), the occurrence of this problem can be avoided.

[0118] Ion exchange membranes used in electrodialysis may adsorb and retain calcium. Cation exchange membranes have cation exchange groups fixed within them, and cations in the solution pass through as counterions, repeatedly adsorbing and dissociating. Therefore, a certain amount of cations remains retained in the ion exchange membrane even after electrodialysis. By performing the concentration process prior to the calcium adsorption and removal process, even if calcium ions retained in the ion exchange membrane are mixed into the lithium solution, the calcium ion concentration can be reduced in the calcium adsorption and removal process, making it possible to recover lithium carbonate with a calcium content of 100 ppm or less.

[0119] <<Calcium adsorption removal process>> The calcium adsorption and removal step is a step of adsorbing and removing calcium using a chelating resin after the neutralization step. The calcium adsorption and removal step can be carried out after the calcium carbonate solid-liquid separation step. In the calcium adsorption and removal step, multiple types of resin towers may be used.

[0120] By contacting the neutralized solution with the chelating resin, the trace amounts of calcium ions remaining in the neutralized solution can be adsorbed onto the chelating resin and removed. This can further reduce the calcium content in the lithium carbonate. Compared to cation exchange resins, chelating resins can more selectively separate calcium from lithium. In addition, CO3 2- Ca without supplying ions 2+ (Calcium adsorption removal solution is obtained), so CO3 2- ions do not dissolve in the solution after calcium adsorption and removal. As a result, it is possible to concentrate the solution after calcium adsorption and removal to a lithium concentration exceeding 5,000 mg / L without precipitating lithium carbonate. Furthermore, since the lithium concentration can be increased before the lithium carbonate crystallization step, the cost and time required for recovering lithium carbonate in the lithium carbonate crystallization step can be reduced. In addition, in the present invention, slaked lime is used in the neutralization step, and the calcium concentration in the solution after neutralization can be suppressed to 1,000 mg / L or less. Furthermore, the calcium carbonate crystallization step and the calcium carbonate solid-liquid separation step can suppress the calcium concentration in the solution after the calcium carbonate solid-liquid separation step to 10 mg / L or less. Therefore, the amount of chelating resin used per unit amount of neutralization solution is small, and calcium removal can be carried out at low cost (economically).

[0121] The chelating resin is preferably a chelating resin having an aminophosphate group or a chelating resin having an iminodiacetic acid group, and particularly preferably a chelating resin having an iminodiacetic acid group. Although some copper ions may remain in the solution after neutralization, the use of a chelating resin having an iminodiacetic acid group makes it possible to adsorb and remove the copper ions, so that the copper ion concentration in the solution after calcium adsorption and removal can be made less than 0.1 mg / L and the copper content in the recovered lithium carbonate can be made 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 the SV to 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.

[0122] <<Lithium carbonate crystallization process>> 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).

[0123] Carbon dioxide (CO2) is added to the concentrated solution containing lithium after the concentration step. By doing so, lithium carbonate in the concentrated solution containing lithium becomes more likely to precipitate, and lithium carbonate precipitates preferentially over lithium (e.g., lithium fluoride) combined with other impurities (e.g., fluorine), making it possible to recover lithium carbonate of higher quality.

[0124] The method for adding carbon dioxide to the concentrated solution containing lithium is not particularly limited and can be appropriately selected depending on the purpose. The method can be carried out by blowing in a gas containing carbon dioxide or adding a carbonate, with the addition of a carbonate being preferred and the addition of sodium carbonate being particularly preferred. The carbonate ion concentration of the lithium-containing concentrated solution after the supply of carbon dioxide is preferably 2 or more relative to the lithium concentration of 1, more preferably 3 or more relative to the lithium concentration of 1, and particularly preferably 4 to 32.3 relative to the lithium concentration of 1. If the carbonate ion concentration is less than 2 relative to the lithium concentration of 1, the amount of lithium sulfate precipitated in addition to lithium carbonate increases, and it may not be possible to crystallize industrial-grade lithium carbonate (lithium carbonate purity of 99.0% or more). On the other hand, if the carbonate ion concentration exceeds 32.3 relative to the lithium concentration of 1, the lithium carbonate may absorb water from the solution containing dissolved metals derived from carbonates added to dissolve the carbonate ions, and the metal purity derived from carbonates in the lithium carbonate may become excessive.

[0125] It is preferable to continue stirring the liquid during lithium carbonate crystallization. Stirring can make the concentrations of carbonate ions and impurity ions (e.g., fluoride ions and sulfate ions) in the liquid uniform, and also make the particle size of the lithium carbonate precipitate uniform, thereby reducing the generation of impurity crystals or the entrainment of the liquid in the lithium carbonate precipitate, and therefore reducing the quality of impurities in the recovered lithium carbonate. During the crystallization of lithium carbonate, the crystallization process may be started or continued with lithium carbonate crystals added before or during the crystallization. The addition of these crystals (seed crystals) can improve and homogenize the particle size of the lithium carbonate recovered by crystallization, thereby reducing the water content of the crystals and further reducing the quality of impurities derived from water-containing components. The lithium carbonate crystallization step is preferably carried out while heating the lithium-containing concentrated solution. Heating the lithium-containing concentrated solution reduces the solubility of lithium carbonate, thereby enabling a greater recovery amount of lithium carbonate.

[0126] The method for heating the concentrated liquid containing lithium is not particularly limited and can be appropriately selected depending on the purpose. Examples include a method of heating using an electric heater or a pipe made of copper, stainless steel, Teflon (registered trademark), or the like through which heated steam passes. For example, the temperature of the solution when heating a concentrated solution containing lithium to precipitate lithium carbonate is not particularly limited as long as it is a temperature at which lithium carbonate can be precipitated, and can be appropriately selected depending on the purpose. For example, the temperature is preferably 60°C or higher and 105°C or lower.

[0127] <<Recovery of lithium carbonate as a valuable resource>> The lithium carbonate-containing slurry obtained in the lithium carbonate crystallization step is subjected to solid-liquid separation, and lithium carbonate (solid) is separated from the post-crystallization liquid, whereby lithium carbonate can be recovered. The solid-liquid separation method is not particularly limited and can be appropriately selected depending on the purpose, but solid-liquid separation techniques such as 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 are preferred, and among these, pressure filtration is particularly preferred. By using pressure filtration, the water content in the lithium carbonate can be reduced more efficiently than by other filtration methods such as suction filtration. In addition, 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.

[0128] The recovered lithium carbonate is preferably washed (washed with hot water) by supplying hot water. The sulfuric acid contamination in the lithium carbonate recovered in the present invention is due to sulfate ions contained in the hydrated lithium carbonate, not to crystals (lithium sulfate), and can therefore be removed by washing with hot water, thereby further reducing the sulfuric acid quality. In addition, potassium derived from the components of the recovered secondary battery is contained, but this potassium can also be removed by washing with hot water. The temperature of the hot water is preferably 60°C or higher, and more preferably 80°C or higher. The higher the hot water temperature, the more the amount of lithium carbonate dissolved in the hot water can be reduced, thereby reducing the loss of lithium to the hot water.

[0129] (Method for treating solid electrolytes) The method for treating a solid electrolyte includes a step of heat treating a sulfide-based solid electrolyte in a water-containing atmosphere having a dew point of −10° C. or higher, and may further include other steps.

[0130] The method for treating a solid electrolyte of the present invention is a method for treating a sulfide-based solid electrolyte.

[0131] The sulfide-based solid electrolyte is not particularly limited and can be appropriately selected depending on the purpose. Examples include defective sulfide-based solid electrolytes generated during the manufacturing process, sulfide-based solid electrolytes discarded due to defects in the equipment used or the end of the life of the equipment used, and used sulfide-based solid electrolytes discarded due to the end of the life of the equipment. The sulfide-based solid electrolyte may be a sulfide-based solid electrolyte in a battery having a sulfide-based solid electrolyte. The battery having the sulfide-based solid electrolyte is as described above in (Method for recovering valuable materials).

[0132] Each step in the valuable resource recovery method of the present invention will be described in detail below.

[0133] <A step of heat treating the sulfide-based solid electrolyte in a water-containing atmosphere with a dew point of -10°C or higher> A heat-treated product (roasted product) is obtained by the step of heat-treating the sulfide-based solid electrolyte in a water-containing atmosphere having a dew point of −10° C. or higher. The heat-treated product (roasted product) means a product obtained by heat-treating a sulfide-based solid electrolyte or a battery having a sulfide-based solid electrolyte.

[0134] The water-containing atmosphere is not particularly limited and can be appropriately selected depending on the purpose, but an atmosphere in which water vapor is present in the roasting furnace is preferred.

[0135] The method for performing the heat treatment is not particularly limited and can be appropriately selected depending on the purpose. For example, the heat treatment can be performed by heating the sulfide-based solid electrolyte or a battery having a sulfide-based solid electrolyte in a known roasting furnace in a water-containing atmosphere with a dew point of −10° C. or higher. The roasting furnace is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include batch furnaces such as rotary kilns, fluidized bed furnaces, tunnel furnaces and muffle furnaces, cupola furnaces and stoker furnaces. Among these, a batch furnace and a pusher-type continuous furnace are preferred, and it is also preferred to use a batch furnace and a pusher-type continuous furnace in combination.

[0136] <<Heat treatment conditions>> The conditions for the heat treatment are the same as those for the heat treatment in the above-mentioned (method for recovering valuable materials).

[0137] <Other processes> The other steps are the same as the <other steps> in the above-mentioned (method for recovering valuable materials).

[0138] Here, an example of an embodiment of the valuable resource recovery method of the present invention will be described with reference to the drawings. Figure 1 is a diagram showing an example of the process flow of the valuable resource recovery method of the present invention. First, a battery with a sulfide-based solid electrolyte is subjected to a heat treatment (heat treatment process) to generate hydrogen sulfide and obtain a heat-treated product. The generated hydrogen sulfide is converted into SO2 in the exhaust gas treatment process, which is then absorbed into an alkaline solution and recovered. In this way, the toxic gas (H2S) can be converted into a less harmful gas (SO2) for treatment. Next, the heat-treated material is crushed and classified (crushing and classification process) to obtain a coarse product and a fine product. Here, copper (Cu), iron (Fe), etc. can be separated from the coarse product. The fine product is then soaked in water to obtain a fine product slurry.

[0139] The fine product slurry is then subjected to wet magnetic separation to separate it into a magnetic and non-magnetic slurry, where the magnetic slurry contains nickel (Ni), cobalt (Co), and manganese (Mn) combined with cobalt. The non-magnetic slurry contains lithium aluminate, carbon, copper (that could not be recovered in the coarse product), and lithium (aqueous solution). Next, sulfuric acid is added to the non-magnetized material slurry to acid-leach the lithium in the lithium aluminate contained in the non-magnetized material, and then solid-liquid separation is performed to separate the filtrate (acid leachate) and the filtration residue (carbon concentrate).

[0140] Next, a neutralizing agent is added to the acid leachate until the desired pH is reached. After neutralization for 1 to 48 hours from the completion of the addition, solid-liquid separation is carried out to separate the filtrate (neutralized liquid) and the filtration residue (neutralized cake). [Example]

[0141] Examples of the present invention will be described below, but the present invention is not limited to these examples in any way.

[0142] Example 1 <Heat treatment> 50mg of 70L2S·30P2S5(Li7P3S 11 ) The solid electrolyte was heat-treated using an electric furnace with an internal volume of 2 L as the heat treatment device, while supplying air with a dew point of -10°C at 2 L / min at a heat treatment temperature of 80°C (heating from 20°C to 80°C over 30 minutes, and then maintaining the temperature for 3 hours).

[0143] <Method for confirming the stability of solid electrolyte to water vapor after heat treatment> The glass dish containing the heat-treated solid electrolyte and a 100 mL glass beaker containing 50 mL of water were placed in a 2 L sealed glass container containing air at 20°C and left to stand for 24 hours. After leaving it to stand for 24 hours, the H2S gas concentration (ppm) inside the sealed container was measured to evaluate the reactivity of the heat-treated solid electrolyte in terms of H2S generation. The measurement results of this H2S concentration are shown in Table 1. The generated H2S gas was rendered harmless through an exhaust gas treatment process.

[0144] [Table 1]

[0145] Example 2 The procedure was the same as in Example 1, except that the test was carried out in a water-containing atmosphere with a dew point of 0° C. The reactivity of the solid electrolyte after the heat treatment for H2S generation was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0146] Example 3 The procedure was the same as in Example 1, except that the test was carried out in a water-containing atmosphere with a dew point of 10° C. The reactivity of the solid electrolyte after the heat treatment for H2S generation was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0147] Example 4 The same procedures as in Example 1 were carried out except that the heat treatment temperature was set to 100° C., and the reactivity of the solid electrolyte after the heat treatment for H2S generation was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0148] Example 5 The same procedures as in Example 1 were carried out except that the heat treatment temperature was set to 850° C., and the reactivity of the solid electrolyte after the heat treatment for H2S generation was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0149] Example 6 <Heat treatment> 50mg of 70L2S·30P2S5(Li7P3S 11 ) A laminated battery cell containing a solid electrolyte and 117 mg of LiCoO2 positive electrode active material was heat-treated using an electric furnace with an internal volume of 2 L as the heat treatment device, with air with a dew point of -10°C supplied at 2 L / min at a heat treatment temperature of 500°C (heated from 20°C to 500°C over 60 minutes, and then held for 1 hour).

[0150] <Method for confirming the stability of the solid electrolyte of a battery cell against water vapor after heat treatment> The glass dish containing the heat-treated battery cell and a 100 mL glass beaker containing 50 mL of water were placed in a 2 L sealed glass container containing air at 20°C and left to stand for 24 hours. After leaving it to stand for 24 hours, the H2S gas concentration (ppm) inside the sealed container was measured to evaluate the reactivity of the heat-treated battery cell in terms of H2S generation. The measurement results of this H2S concentration are shown in Table 1. The generated H2S gas was rendered harmless through an exhaust gas treatment process.

[0151] Example 7 Except for supplying air with a dew point of 0° C., the same procedures as in Example 6 were carried out, and the reactivity of the battery cells after the heat treatment for H2S generation was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0152] Example 8 Except for changing the heat treatment temperature to 850° C., the same procedures as in Example 6 were carried out, and the reactivity of the battery cells after the heat treatment for H2S generation was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0153] (Comparative Example 1) The procedure was the same as in Example 1, except that the test was carried out in a water-containing atmosphere with a dew point of -20°C, and the reactivity of the battery cells after the heat treatment for H2S generation was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0154] (Comparative Example 2) Except for being carried out in a water-containing atmosphere with a dew point of −29° C., the same procedures as in Example 1 were carried out, and the reactivity of the battery cells after the heat treatment for H2S generation was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0155] (Comparative Example 3) The same procedures as in Example 1 were carried out except that the heat treatment temperature was set to 20°C, and the reactivity of the battery cells after the heat treatment for H2S generation was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0156] Comparative Example 4 The same procedures as in Example 1 were carried out except that the heat treatment temperature was set to 60° C., and the reactivity of the battery cells after the heat treatment in terms of H2S generation was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0157] (Comparative Example 5) The procedure was the same as in Example 6, except that the test was carried out in a water-containing atmosphere with a dew point of -20°C, and the reactivity of the battery cells after the heat treatment for H2S generation was evaluated in the same manner as in Example 6. The results are shown in Table 1.

[0158] (Comparative Example 6) The same procedures as in Example 6 were carried out except that the test was carried out in a water-containing atmosphere with a dew point of -29°C, and the reactivity of the battery cells after the heat treatment for H2S generation was evaluated in the same manner as in Example 6. The results are shown in Table 1.

[0159] As shown in Table 1, in Examples 1 to 8, the amount of hydrogen sulfide generated from the solid electrolyte or all-solid-state battery cell after heat treatment was small, and the residue after heat treatment was sufficiently stabilized. In Comparative Examples 1 to 4, dangerous levels of hydrogen sulfide exceeding 100 ppm were generated from the battery cell after heat treatment, and the battery cell was not sufficiently stabilized after heat treatment. Therefore, it was found that by heat treating a sulfide-based solid electrolyte in a water-containing atmosphere with a dew point of -10°C or higher, the sulfide-based solid electrolyte can be treated efficiently and safely.

Claims

1. A method for recovering valuable resources, comprising a heat treatment step of heat-treating a sulfide-based solid electrolyte in a battery having the sulfide-based solid electrolyte at a heat treatment temperature of 70°C or higher in a water-containing atmosphere having a dew point of -10°C or higher.

2. The method for recovering valuable resources according to claim 1, wherein the dew point in the water-containing atmosphere is 0°C or higher.

3. The method for recovering valuable resources according to claim 1, wherein the temperature of the water-containing atmosphere is 80°C or higher.

4. 2. The method for recovering valuable resources according to claim 1, wherein the water-containing atmosphere is an atmosphere in which water vapor is present inside a roasting furnace.

5. After the heat treatment step, a crushing and classification step in which the heat-treated product obtained in the heat treatment step is crushed and the crushed product is classified to obtain a coarse product and a fine product containing the valuable material; a slurrying step of soaking the fine product in water to form a fine product slurry; a wet magnetic separation step of separating the fine product slurry into a magnetic material slurry and a non-magnetic material slurry by wet magnetic separation; an acid leaching step in which sulfuric acid is added to the non-magnetized material slurry and / or non-magnetized materials obtained by subjecting the non-magnetized material slurry to solid-liquid separation, thereby leaching the non-magnetized 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; a neutralization cake solid-liquid separation step of separating the liquid obtained in the neutralization step into solid and liquid; The method for recovering valuable materials according to claim 1, comprising:

6. A method for treating a solid electrolyte, comprising the step of heat-treating a sulfide-based solid electrolyte at a heat treatment temperature of 70°C or higher in a water-containing atmosphere having a dew point of -10°C or higher.

Images