Lithium leaching method

Abstract

The present invention provides a method for leaching lithium, the method enabling the achievement of a lithium compound that has a purity sufficient for use in batteries by leaching lithium from lithium titanium oxide that is contained, as a negative electrode active material or the like, in waste lithium ion batteries. A method for leaching lithium according to the present invention leaches lithium from a powder that contains lithium titanium oxide that is obtained from waste lithium ion batteries, and is characterized in that the powder is immersed in a mineral acid that is at a specific concentration and is heated to a temperature of not less than 80°C but less than 95°C.

Description

[Technical Field]

[0001] The present invention relates to a method for leaching lithium. [Background technology]

[0002] Conventionally, a method for recovering lithium titanium oxide, which is used as a negative electrode active material in lithium ion batteries, has been known which includes the steps of heat-treating and pulverizing used lithium ion batteries to obtain a pulverized material, dispersing the pulverized material in a solvent to obtain a dispersion, separating the dispersion into a precipitate layer and a supernatant liquid, and adding a flocculating sedimentation agent to the supernatant liquid to precipitate the lithium titanium oxide powder (see, for example, Patent Document 1).

[0003] However, the method described in Patent Document 1 has the problem that although it is possible to obtain lithium titanium oxide as an active material for a regenerated negative electrode, it is not possible to obtain a lithium compound with battery-grade purity. Meanwhile, a known method for acid leaching lithium from lithium manganate, lithium cobaltate, lithium nickelate, and the like contained as positive electrode active materials in used lithium ion batteries involves roasting (heat treating) used lithium ion batteries or pulverizing and classifying them without heat treating them to obtain a sintered powder, which is then immersed in sulfuric acid heated to about 50 to 70°C (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-130474 [Patent Document 2] Japanese Patent Application Publication No. 2019-169309 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is no known method for acid leaching lithium from lithium titanium oxide. In view of the above circumstances, an object of the present invention is to provide a lithium leaching method capable of leaching lithium from lithium-titanium oxide contained as a negative electrode active material in waste lithium-ion batteries to obtain a lithium compound having battery-grade purity. [Means for solving the problem]

[0006] In order to achieve this object, the lithium leaching method of the present invention is a method for leaching lithium from a powder containing lithium-titanium oxide obtained from a waste lithium-ion battery, the powder comprising: 90 The method is characterized by immersing the material in a mineral acid of a predetermined concentration heated to a temperature in the range of 95°C or higher and lower than 95°C.

[0007] According to the lithium leaching method of the present invention, a powder containing lithium-titanium oxide obtained from waste lithium-ion batteries can be dissolved in a mineral acid, and as a result, lithium can be leached from the lithium-titanium oxide.

[0008] Here, if the time for immersing the powder of used lithium ion batteries containing lithium titanium oxide in the mineral acid is too short, the leaching of lithium from the powder into the mineral acid is not completed, whereas if the immersion time is too long, the leaching will not proceed any further and the cost of heating will increase.

[0009] Furthermore, the temperature of the mineral acid 90 If the temperature is lower than 95°C, the powder cannot be efficiently dissolved in the mineral acid. If the temperature of the mineral acid is higher than 95°C, gases will volatilize violently, which may deteriorate the working environment or corrode the equipment.

[0010] before The mineral acid , hydrochloric acid . The immersion 、2 The time period is in the range of 20 hours to 25 hours. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram showing the results of immersing powder of used lithium ion batteries containing lithium titanium oxide according to the method of the present invention in hydrochloric acid. [Figure 2] FIG. 2 shows the results of immersing powder of waste lithium ion batteries containing lithium titanium oxide according to the method of the present invention in sulfuric acid. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, the embodiment of the present invention will be described in more detail. The lithium leaching method of the present embodiment can be used when leaching lithium from a powder containing lithium titanium oxide obtained from waste lithium ion batteries. In the lithium leaching method of this embodiment, the waste lithium ion batteries refer to used lithium ion batteries that have reached the end of their life as battery products, lithium ion batteries that have been discarded as defective products in the manufacturing process, and residual positive electrode materials that have been used in the manufacturing process to produce products.

[0013] In the lithium leaching method of this embodiment, the used lithium ion batteries are subjected to, for example, the following pretreatment. In the pretreatment, if the used lithium ion batteries are used lithium ion batteries that have reached the end of their life as battery products or lithium ion batteries that have been discarded as defective products during the manufacturing process, the used lithium ion batteries are first discharged in salt water to discharge all remaining charge. Next, the used lithium ion batteries are disassembled, and the casings, current collectors, and other components that constitute the used lithium ion batteries are removed to obtain an electrode foil containing lithium titanium oxide.

[0014] The lithium titanium oxide in this embodiment is a spinel-structure lithium titanium oxide (for example, a lithium titanium oxide having the general formula Li 4+x Ti5O 12 (x is -1≦x≦3)), ramsdellite-structure lithium titanium oxide (e.g., Li 2+x Ti3O7(-1≦x≦3)), Li 1+x Ti2O4(0≦x≦1), Li1.1+x Ti 1.8 O4 (0 ≦ x ≦ 1), Li 1.07+x Ti 1.86 O4 (0 ≦ x ≦ 1), Li x It includes TiO2 (0 < x ≦ 1). The lithium titanate is typically Li4Ti5O 12 and is. Further, the lithium titanate in this embodiment may be doped with at least one selected from the group consisting of Co, V, Mn, Fe, Ni, Cu, Zn, Al, B, Mg, Ca, Sr, Ba, Zr, Nb, Mo, W, Bi, Na, Ga, and rare earth elements.

[0015] Next, the electrode foil is heat-treated (calcined) at a temperature in the range of 300 to 400 °C. And after the heat treatment, or without heat-treating the electrode foil, it is pulverized with a pulverizer such as a biaxial crusher or a hammer crusher, and the electrode foil base material and the like constituting the electrode foil are removed (classified) by sieving to obtain a powder containing lithium titanate.

[0016] In the lithium leaching method of this embodiment, next, the powder is immersed in a mineral acid of a predetermined concentration to dissolve the lithium titanate, thereby leaching lithium with the mineral acid. The powder is immersed in a mineral acid of a predetermined concentration heated to a temperature in the range of 80 °C or more and less than 95 °C. As a result, lithium can be leached from the lithium titanate. The immersion time can preferably be in the range of 2 hours or more and 20 hours or less. Also, in the lithium leaching method of this embodiment, it is preferable that the powder is immersed in a mineral acid heated to a temperature in the range of 90 °C or more and less than 95 °C.

[0017] The mineral acid preferably contains at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, and more preferably contains at least one selected from the group consisting of hydrochloric acid and sulfuric acid.

Example

[0018] Example 1 1000 g of electrode foil from a used lithium-ion battery was placed in an electric furnace and heated (roasted) at 400°C for 10 minutes. After the heating process, the foil was cut into squares measuring approximately 2 cm in length and width, crushed in a crusher, and sieved through a 1 mm mesh sieve. The powder that passed through the sieve was collected to obtain Li4Ti5O 12 780 g of powder containing lithium titanium oxide containing the above as the main component was obtained.

[0019] 100 g of the powder was immersed in 170 mL of hydrochloric acid to leach lithium from the lithium-titanium oxide. The concentration of the hydrochloric acid used for the immersion, the immersion time, and the temperature of the hydrochloric acid were varied, and the lithium concentration in the leachate was measured to determine the amount of lithium leached under each condition. Furthermore, the ratio of the amount of leached lithium to the theoretical amount of lithium contained in the powder was calculated as the lithium leaching rate (mass%). The results are shown in Figure 1.

[0020] Example 2 100 g of the powder was immersed in 170 mL of sulfuric acid to leach lithium from the lithium-titanium oxide. The sulfuric acid concentration, immersion time, and sulfuric acid temperature were varied, and the lithium concentration in the leachate was measured to determine the amount of lithium leached under each condition. Furthermore, the ratio of the amount of leached lithium to the theoretical amount of lithium contained in the powder was calculated as the lithium leaching rate (mass%). The results are shown in Figure 2.

[0021] 1 and 2, to make the effect easier to understand, the range of conditions where the lithium leaching rate exceeds 60% is enclosed in a bold frame as a guideline. It is clear that when the temperature of the mineral acid is 80°C or higher, preferably 90°C or higher, the lithium leaching rate is higher and lithium can be leached more efficiently. Furthermore, since the increase in the leaching rate plateaus over time, a immersion time of about 2 to 20 hours is preferable, and any extension of the immersion time beyond that requires consideration of the increase in heating costs, etc.

Claims

[Claim 1] 1. A method for leaching lithium from a powder containing lithium titanium oxide obtained from waste lithium ion batteries, comprising: Immersing the powder in a mineral acid having a concentration of 6 mol / L or more heated to a temperature in the range of 90°C or more but less than 95°C for a period of time in the range of 2 hours to 20 hours; 1. A method for leaching lithium, wherein the mineral acid is hydrochloric acid.

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