Method for concentrating lithium-containing material

Abstract

This method for concentrating a lithium-containing material involves heating a lithium-containing material containing a lithium compound in a chlorine and / or chloride vapor atmosphere, and volatilizing a material having a vapor pressure higher than that of the lithium compound to obtain a lithium-containing material in which the lithium compound is concentrated. The atmosphere in which temperature is raised to a heating treatment temperature is set to an inert gas atmosphere, and thereafter, the atmosphere is changed to the chlorine and / or chloride vapor atmosphere.

Description

Method for concentrating lithium-containing materials

[0001] TECHNICAL FIELD The present invention relates to a method for concentrating lithium-containing material, and more particularly to a method for concentrating lithium in crushed material obtained by heat-treating used lithium-ion secondary batteries.

[0002] Positive electrode materials using lithium iron phosphate (LFP), which does not contain nickel or cobalt, have a small theoretical electrical capacity, but unlike other positive electrode materials, they are inexpensive because they do not contain nickel or cobalt, and they also have good safety performance.

[0003] Recycling is progressing with regard to the recovery of valuable metals from ternary cathode materials (NMC), which contain large amounts of valuable metals such as nickel, cobalt, and lithium.

[0004] To recycle valuable materials in ternary cathode materials (NMC), used lithium-ion secondary batteries are heat-treated and crushed to obtain crushed material. Valuable metals contained in the crushed material are extracted by dissolving them in a solvent such as acid or pure water, and the valuable metals are separated and recovered from the extracted solution using solvent extraction or other methods.

[0005] When this method is applied to recovering valuable materials from cathode materials using lithium iron phosphate, dissolving the crushed material in acid dissolves iron and phosphorus in high concentrations, making it difficult to selectively recover lithium from the extract at low cost.

[0006] JP 2012-229481 A

[0007] An object of the present invention is to provide a method for concentrating a lithium-containing material that enables selective recovery of lithium from the lithium-containing material in an efficient manner.

[0008] The present invention has the following gist.

[0009] [1] A method for concentrating a lithium-containing material, comprising: heat-treating a lithium-containing material containing a lithium compound in an atmosphere of chlorine and / or chloride vapor (at least one of chlorine and chloride vapor) to volatilize a substance having a vapor pressure higher than that of the lithium compound, thereby obtaining a lithium-containing material in which the lithium compound is concentrated.

[0010] [2] The method for concentrating a lithium-containing material according to [1], wherein the atmosphere is a chlorine gas atmosphere.

[0011] [3] The method for concentrating a lithium-containing material according to [1], wherein the temperature when the lithium-containing material is heat-treated in the atmosphere of chlorine and / or chloride vapor is 200 to 900°C.

[0012] [4] The method for concentrating a lithium-containing material according to [3], wherein the atmosphere is an inert gas atmosphere when the temperature is raised to the heat treatment temperature, and thereafter the atmosphere is a chlorine and / or chloride vapor atmosphere.

[0013] [5] The method for concentrating a lithium-containing material according to any one of [1] to [4], wherein the lithium-containing material is a crushed material obtained by heat-treating and crushing used lithium-ion secondary batteries, or a product discarded from a manufacturing process of lithium-ion secondary batteries.

[0014] In the present invention, lithium-containing materials containing lithium compounds (for example, crushed materials obtained by heat-treating and crushing used lithium ion secondary batteries using LFP) are heat-treated in an atmosphere of chlorine and / or chloride vapor. As a result, iron and phosphorus, which have high vapor pressures of chlorides, volatilize at a relatively low temperature. Carbon is also volatilized by chlorides or CO, CO ２ The lithium compound, which has a low vapor pressure in the low temperature range, remains in the lithium-containing material. This results in a lithium-enriched lithium-containing material.

[0015] The present invention will be described in further detail below.

[0016] In the method for concentrating a lithium-containing material of the present invention, a lithium-containing material containing a lithium compound is heated in an atmosphere containing chlorine and / or chloride vapor to volatilize substances having a vapor pressure higher than that of the lithium compound, thereby obtaining a lithium-containing material in which the lithium compound is concentrated.

[0017] As the lithium-containing material containing a lithium compound, crushed material (so-called black mass) obtained by heating used lithium-ion secondary batteries at about 300 to 900°C, particularly about 400 to 700°C, and then crushing them is preferred, but crushed material obtained by heating and crushing rejected products (which may be battery manufacturing parts, semi-finished products, or finished products) that are discarded as defective products from the manufacturing process of lithium-ion secondary batteries may also be used. In the case of rejected products such as cathode materials, crushing may not be necessary.

[0018] The lithium compound in the black mass is mainly lithium iron phosphate, but may also be a ternary positive electrode material, a nickel-based positive electrode material, a manganese-based positive electrode material, etc. The lithium concentration (lithium content) in the black mass is preferably 1 to 7 wt %, particularly 2 to 4 wt %.

[0019] The average particle size (average particle size measured by JIS sieve) of the lithium-containing material such as black mass is preferably 2 mm or less, particularly preferably 1 mm or less.

[0020] Various crushers such as a jaw crusher can be used as a crusher for crushing used lithium-ion secondary batteries, etc. When the discharged product is a cathode material, it may be subjected to the next step (heat treatment in an atmosphere of chlorine, etc.) without being crushed, or the cathode material and carbon may be mixed and then subjected to the next step.

[0021] The atmosphere in which the lithium-containing material is heated is preferably a chlorine gas atmosphere (particularly a chlorine gas atmosphere with a chlorine concentration of 99 vol % or more). ２ The atmosphere may be a vapor atmosphere of a chloride such as NaCl, or a mixed gas atmosphere of chlorine gas and a chloride gas. The higher the concentration of chlorine gas in this mixed gas, the better.

[0022] The heating temperature when the lithium-containing material is heated in a chlorine gas or chloride gas atmosphere is preferably 200°C or higher, particularly 400°C or higher, and especially 500°C or higher, and is 900°C or lower, particularly 700°C or lower, and especially 600°C or lower.

[0023] The higher the heating temperature, the faster the volatilization rate of iron and phosphorus. However, at temperatures above 700°C, LiCl volatilizes and the LiCl recovery rate decreases slightly, and particularly at temperatures above 900°C, the LiCl recovery rate decreases. At temperatures above 606°C, LiCl melts and forms a solid when the temperature is lowered after the heat treatment. The heating temperature does not need to be constant and may vary within the above heating temperature range.

[0024] The atmosphere may be air or an inert gas atmosphere (e.g., nitrogen or argon atmosphere) until the temperature reaches near the heating temperature range, and then, after the temperature is raised to near the heating temperature range, the atmosphere may be changed to chlorine gas or chloride gas.

[0025] The heat treatment time within the above heating temperature range is preferably 1 min to 5 hr, particularly 1 to 2 hr. The higher the heating temperature, the shorter the heat treatment time within the above heating temperature range. The heating temperature is preferably adjusted depending on the amount of metal in the lithium-containing material and the amount of lithium-containing material to be treated.

[0026] As the heating device for the lithium-containing material, a batch type stoker furnace or fluidized bed furnace, as well as a rotary kiln or fluidized bed furnace that can continuously charge and discharge solids, can be used, but is not limited to these.

[0027] When a lithium-containing material is heated in a chlorine or chloride gas atmosphere, the Fe component contained in the lithium-containing material is converted into FeCl by approximately 500°C. ３ The P component volatilizes as POCl ３ and PCl ３ C is volatilized as CO and CO ２ The Li component remains in the form of solid LiCl up to about 500°C, but becomes liquid or gaseous LiCl at temperatures above 500°C.

[0028] In one embodiment of the present invention, crushed used lithium ion secondary batteries (Li content of about 3 wt%) can be concentrated to a Li content of about 10 to 14 wt%. The Li content in LiCl is 16.4 wt%.

[0029] In the present invention, volatilized FeCl ３、 POCl ３、 PCl３ LiCl in the residue can be recovered by dissolving it in pure water or an acid solution, and then purifying and crystallizing it to obtain LiCl. ２ CO ３ can be recovered as

[0030] [Example 1] A used lithium ion secondary battery using an LFP was heat-treated, and 2 g of crushed material with an average particle size of about 0.6 mm (Li content: 3.0 wt %, hereinafter referred to as black mass) was placed in a porcelain boat and placed in a cylindrical glass tube with an outer diameter of 20 mm and a length of 500 mm. The boat was heated in an electric furnace at a temperature increase rate of 20°C / min while Ar gas was circulated at a rate of 20 mL / min. After the temperature reached 600°C, the atmospheric gas was changed from Ar gas to Cl ２ The atmospheric gas was switched to Ar gas (20 mL / min), and the mixture was treated for 2 hours at 600° C. After 2 hours had passed, the atmospheric gas was switched to Ar gas (20 mL / min), and the temperature was lowered to room temperature.

[0031] Table 1 shows the analytical values ​​of the main components in the initial black mass (before heat treatment) and the residue after the treatment.

[0032] Comparative Example 1 Black mass was treated under the same conditions as in Example 1, except that Ar gas was constantly passed through at a rate of 20 mL / min. Table 1 shows the results of analysis of the main components in the residue.

[0033]

[0034] As shown in Table 1, Fe, P, and C were volatilized and Li was concentrated to 13.6 wt % in Example 1. In contrast, in Comparative Example 1, Li was concentrated to only 3.8 wt %.

[0035] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications are possible within the scope of the invention.

[0036] This application is based on Japanese Patent Application No. 2024-077350, filed on May 10, 2024, the entire contents of which are incorporated by reference.

Claims

1. A method for concentrating a lithium-containing material, in which a lithium-containing material containing lithium compounds is heat-treated in an atmosphere of chlorine and / or chloride vapor to volatilize substances with a higher vapor pressure than the lithium compounds, thereby obtaining a lithium-containing material in which the lithium compounds are concentrated.

2. The method for concentrating lithium-containing materials according to claim 1, wherein the atmosphere is a chlorine gas atmosphere.

3. The method for concentrating a lithium-containing material according to claim 1, wherein the temperature when the lithium-containing material is heat-treated in the atmosphere of chlorine and / or chloride vapor is 200 to 900°C.

4. The method for concentrating a lithium-containing material according to claim 3, wherein the atmosphere is an inert gas atmosphere when the temperature is raised to the heat treatment temperature, and thereafter the atmosphere is changed to a chlorine and / or chloride vapor atmosphere.

5. A method for concentrating a lithium-containing material according to any one of claims 1 to 4, wherein the lithium-containing material is crushed material obtained by heat-treating and crushing used lithium-ion secondary batteries, or is a waste product from the manufacturing process of lithium-ion secondary batteries.

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