A short-range cleaning method for recycling key metals from retired lithium batteries

Abstract

The present invention relates to a method for short-range clean recovery of key metals from retired lithium batteries, and belongs to the field of waste battery treatment and resource utilization. The method provided by the present invention comprises the following steps: discharging, disassembling, and stripping retired lithium batteries to obtain positive electrode powder, then mixing the positive electrode powder, oxalate ester, and water to carry out a leaching reaction to obtain a slurry, subjecting the slurry to solid-liquid separation to obtain a leachate and leach residue, adding sodium carbonate to the leachate to carry out a lithium precipitation reaction to obtain a lithium precipitation slurry, subjecting the lithium precipitation slurry to solid-liquid separation to obtain a lithium-containing solid, and finally washing and drying the lithium-containing solid to obtain a battery-grade lithium carbonate product. The present invention adopts oxalate ester as a leaching medium, which greatly reduces the harm of inorganic acids and alkalis to the environment. The provided method is simple to operate, has low energy consumption, and can achieve short-range clean and efficient recovery of lithium from retired lithium batteries.

Description

Technical Field

[0001] The present invention relates to the field of waste battery processing and resource utilization, and in particular to a method for short-range cleaning and recycling of key metals from retired lithium batteries. Background Art

[0002] With the increasing population and demand for electric vehicles, a large amount of lithium-ion batteries are produced and consumed annually. In 2022, national lithium-ion battery production is expected to reach 750GWh, a year-on-year increase of over 130%, with energy storage lithium battery production exceeding 100GWh. Currently, the raw materials for lithium-ion battery production primarily come from natural mineral resources. However, these resources are subject to uneven distribution, high mining costs, and severe environmental pollution, hindering their development. Therefore, the recycling of retired lithium batteries is a key strategy for the sustainable development of lithium-ion batteries. Recycling retired lithium-ion batteries can both reduce dependence on natural mineral resources and significantly reduce the environmental pollution caused by waste.

[0003] The positive electrode materials of lithium-ion batteries include lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, and lithium iron phosphate. Currently, the main methods for recovering lithium from waste lithium-ion batteries are heat treatment and acid leaching. For example, according to the national patent application number CN201910312235.7, the retired lithium iron phosphate battery positive electrode powder is first calcined at 600-700°C in an oxygen-containing atmosphere, then an acidic mixture is added, and then calcined at 400-500°C in an inert atmosphere. Finally, the powdered positive electrode active material is washed with DMF to obtain lithium iron phosphate material. The high-temperature calcination method increases energy consumption. At the same time, the decomposition of the fluorine-containing binder PVDF and organic matter in the lithium battery positive electrode sheet will produce fluoride and carcinogenic dioxin gas, which poses great harm to the environment and operators. In addition, invention patent CN113603120A first uses excess acid to acid-leach waste lithium iron phosphate powder, filters out insoluble matter, and then uses the alkalinity of waste lithium iron phosphate powder to adjust the pH value of the filtrate, filters, and uses calcium carbonate to preliminarily adjust the pH of the filtrate to 5, and then uses lime to continue to adjust the pH to 10, filters, adds saturated lithium carbonate to the filtrate to remove calcium, filters, and passes carbon dioxide through the filtrate to recover battery-grade lithium carbonate. Invention patent CN112981107A separates and recovers the lithium in waste ternary lithium batteries through crushing separation, sulfuric acid primary leaching, sulfuric acid secondary leaching, primary leachate aluminum and iron removal, filtration, extraction, and lithium precipitation. However, the acid leaching method not only uses a large amount of acid and alkali to cause environmental pollution in the process of recovering lithium elements, but also has a long recovery process and a cumbersome process, resulting in low lithium recovery efficiency.

[0004] In response to the series of problems encountered in the actual production of resource recycling of retired lithium batteries, the present invention provides a method with simple operation, low energy consumption, and short-range efficient and selective recovery of lithium elements. The leaching medium used is clean and environmentally friendly, and will not cause secondary pollution due to the use of strong inorganic acids. At the same time, it can achieve efficient and selective recovery of lithium from retired lithium batteries. Summary of the Invention

[0005] In light of this, the present invention provides a short-range clean recovery method for key metals from retired lithium batteries. The method is simple to operate and uses oxalate as the leaching medium, avoiding the use of strong inorganic acids and helping to reduce secondary pollution.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A method for short-range cleaning and recycling of key metals from retired lithium batteries, comprising the following steps:

[0008] Discharging, disassembling and stripping retired lithium batteries to obtain positive electrode powder;

[0009] subjecting the positive electrode powder, oxalate and water to a leaching reaction to obtain a slurry;

[0010] performing solid-liquid separation on the slurry to obtain leachate and leach residue;

[0011] adding sodium carbonate to the leachate to carry out lithium precipitation reaction to obtain lithium precipitation slurry;

[0012] Separating the lithium precipitated slurry into a solid-liquid state to obtain a lithium-containing solid;

[0013] The lithium-containing solid is washed and dried to obtain a battery-grade lithium carbonate product.

[0014] Preferably, the retired lithium batteries include one or more of retired lithium iron phosphate batteries, retired ternary lithium batteries, retired lithium cobalt oxide batteries and retired lithium manganese oxide batteries.

[0015] Preferably, the oxalate ester includes one or more of dimethyl oxalate, diethyl oxalate and dipropyl oxalate.

[0016] Preferably, the mass ratio of the positive electrode powder to the oxalate ester is 1:0.1-15, and the solid-to-liquid ratio of the positive electrode powder to the oxalate ester aqueous solution is 10-700 g / L.

[0017] Preferably, the leaching reaction is carried out by stirring and heating, more preferably by stirring and heating in an oil bath, the temperature being 30 to 200° C., the stirring rate being 50 to 600 rpm, and the stirring time being 0.5 to 8 h.

[0018] Preferably, the lithium precipitation reaction is carried out by stirring and heating in an oil bath at a temperature of 60 to 100° C. for 1 to 3 hours.

[0019] The present invention provides a short-range clean recovery method for key metals of retired lithium batteries, comprising the following steps: discharging, disassembling and stripping retired lithium batteries to obtain positive electrode powder; stirring and heating the retired lithium battery positive electrode powder, oxalate and water to carry out a leaching reaction to obtain a slurry; performing solid-liquid separation on the slurry to obtain a leachate and a leach residue; adding sodium carbonate to the leachate to carry out a lithium precipitation reaction to obtain a lithium precipitation slurry; performing solid-liquid separation on the lithium precipitation slurry to obtain a lithium-containing solid; and washing and drying the lithium-containing solid to obtain a battery-grade lithium carbonate product.

[0020] The present invention utilizes environmentally friendly oxalate as a reaction medium, which can be hydrolyzed into oxalic acid and methanol under mild conditions. The hydrolyzed components play a synergistic role, and the lithium leaching rate is high. Therefore, the present invention has the advantages of simple operation, low energy consumption, high selective recovery rate of lithium, and closed-loop circulation of the leaching solution after lithium recovery. In particular, in some environments where the reaction conditions require relatively strict requirements, the use of oxalate is more suitable, environmentally friendly, and highly applicable. DETAILED DESCRIPTION

[0021] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention.

[0022] Example 1

[0023] Discharge and disassemble retired lithium iron phosphate batteries to collect positive electrode powder;

[0024] Mix retired lithium iron phosphate battery positive electrode powder, diethyl oxalate and water and place them in a magnetic stirring oil bath. Heat them in an oil bath at 30°C at a rate of 50 rpm for 8 hours. The mass ratio of retired lithium iron phosphate battery positive electrode powder to oxalate is 1:15, and the solid-liquid ratio of lithium iron phosphate positive electrode powder to aqueous solution is 700 g / L.

[0025] The leached slurry was filtered and separated to obtain a leachate and a leach residue, and sodium carbonate with a molar ratio of 1.6 times that of lithium was added to the leachate, and the mixture was placed in a magnetic stirring oil bath pot and heated at 80° C. for 2 h to obtain a lithium precipitation slurry;

[0026] The obtained lithium precipitated slurry was filtered and separated to obtain lithium-containing solids, which were washed three times with deionized water and then dried to obtain a battery-grade lithium carbonate product with a purity of 99.51%.

[0027] Example 2

[0028] Discharge and disassemble retired lithium iron phosphate batteries to collect positive electrode powder;

[0029] Mix retired lithium iron phosphate battery positive electrode powder, dipropyl oxalate and water and place them in a magnetic stirring oil bath, and heat them in an oil bath at 200°C at a rate of 600 rpm for 0.5 h. The mass ratio of retired lithium iron phosphate battery positive electrode powder to oxalate is 1:0.1, and the solid-liquid ratio of lithium iron phosphate positive electrode powder to aqueous solution is 10 g / L.

[0030] The leached slurry was filtered and separated to obtain a leachate and a leach residue, and sodium carbonate with a molar ratio of 1.2 times that of lithium was added to the leachate, and the mixture was placed in a magnetic stirring oil bath pot and heated at 90° C. for 1.5 h to obtain a lithium precipitation slurry;

[0031] The obtained lithium precipitated slurry is filtered and separated to obtain lithium-containing solids, which are washed three times with deionized water and then dried to obtain a battery-grade lithium carbonate product with a purity of 99.56%.

[0032] Example 3

[0033] Discharge and disassemble retired lithium iron phosphate batteries to collect positive electrode powder;

[0034] Mix retired lithium iron phosphate battery positive electrode powder, dimethyl oxalate and water and place them in a magnetic stirring oil bath, and heat them in an oil bath at 60°C at a rate of 400 rpm for 4 hours. The mass ratio of retired lithium iron phosphate battery positive electrode powder to oxalate is 1:1, and the solid-liquid ratio of lithium iron phosphate positive electrode powder to aqueous solution is 200 g / L.

[0035] The leached slurry was filtered and separated to obtain a leachate and a leach residue, and sodium carbonate with a molar ratio of 1.5 times that of lithium was added to the leachate, and the mixture was placed in a magnetic stirring oil bath pot and heated at 95° C. for 2 h to obtain a lithium precipitation slurry;

[0036] The obtained lithium precipitated slurry is filtered and separated to obtain lithium-containing solids, which are washed three times with deionized water and then dried to obtain a battery-grade lithium carbonate product with a purity of 99.69%.

[0037] Example 4

[0038] Discharge and disassemble retired lithium cobalt oxide batteries to collect positive electrode powder;

[0039] A mixture of retired lithium cobalt oxide battery positive electrode powder, dimethyl oxalate and water was placed in a magnetic stirring oil bath and heated at 80°C for 7 hours at a rate of 500 rpm. The mass ratio of retired lithium cobalt oxide battery positive electrode powder to oxalate was 1:1.2, and the solid-liquid ratio of retired lithium cobalt oxide positive electrode powder to aqueous solution was 100 g / L.

[0040] The leached slurry was filtered and separated to obtain a leachate and a leach residue, and sodium carbonate with a lithium molar ratio of 1.6 times was added to the leachate, and the mixture was placed in a magnetic stirring oil bath pot and heated at 90° C. for 3 h to obtain a lithium precipitation slurry;

[0041] The obtained lithium precipitated slurry was filtered and separated to obtain lithium-containing solids, which were washed three times with deionized water and then dried to obtain a battery-grade lithium carbonate product with a purity of 99.61%.

[0042] Example 5

[0043] Discharge and disassemble retired ternary lithium batteries to collect positive electrode powder;

[0044] Mix retired ternary lithium battery positive electrode powder, dimethyl oxalate and water and place them in a magnetic stirring oil bath, and heat them in an oil bath at 90°C at a rate of 300 rpm for 6 hours. The mass ratio of retired ternary lithium battery positive electrode powder to oxalate is 1:1.5, and the solid-liquid ratio of retired lithium cobalt oxide positive electrode powder to aqueous solution is 120 g / L.

[0045] The leached slurry was filtered and separated to obtain a leachate and a leach residue, and sodium carbonate with a lithium molar ratio of 1.4 times was added to the leachate, and the mixture was placed in a magnetic stirring oil bath pot and heated at 100° C. for 3 h to obtain a lithium precipitation slurry;

[0046] The obtained lithium precipitated slurry is filtered and separated to obtain lithium-containing solids, which are washed three times with deionized water and then dried to obtain a battery-grade lithium carbonate product with a purity of 99.6%.

[0047] Comparative Example 1

[0048] A mixture of retired lithium iron phosphate battery positive electrode powder, oxalate and water was placed in a magnetic stirring oil bath and heated at 20°C for 5 h at a rate of 50 rpm. The other preparation conditions were the same as those in Example 2.

[0049] Comparative Example 2

[0050] The mass ratio of retired lithium cobalt oxide battery positive electrode powder and oxalate was adjusted to 1:20, and the other preparation conditions were the same as those in Example 2.

[0051] Comparative Example 3

[0052] The solid-to-liquid ratio of the ternary lithium battery positive electrode powder to the aqueous solution was adjusted to 900 g / L, and the other preparation conditions were the same as those in Example 2.

[0053] Comparative Example 4

[0054] The retired lithium iron phosphate battery positive electrode powder, oxalic acid and water were mixed and placed in a magnetic stirring oil bath. The other preparation conditions were the same as those in Example 2.

[0055] The leaching rate of lithium in Examples 1 to 5 and Comparative Examples 1 to 4 was statistically analyzed, and the statistical results are shown in Table 1. The leaching rate of lithium is calculated according to Formula I:

[0056] μ=R / R0×100% Formula I;

[0057] In formula I, μ is the leaching rate of lithium, R0 is the mass of lithium in the retired lithium iron phosphate powder, and R is the mass of lithium in the leachate obtained after filtration and separation.

[0058] Table 1 Lithium leaching rate results in Examples 1 to 5 and Comparative Examples 1 to 4

[0059]

[0060]

[0061] As can be seen from Table 1, in Examples 1-5, the lithium leaching rate was above 85%, while the leaching rates of iron, phosphorus, aluminum, nickel, cobalt, and manganese were extremely low, with the highest lithium leaching rate reaching 99.99%. This demonstrates that the method provided by the present invention can fully recycle retired lithium battery positive electrode powder while avoiding the use of strong inorganic acids and reducing secondary pollution. However, in Comparative Examples 1-4, the lithium leaching rate was lower, possibly due to the following reasons: in Comparative Example 1, the temperature was not high enough to meet the reaction conditions; in Comparative Example 2, the mass ratio of positive electrode powder to oxalate ester was too small (the amount of oxalate ester was insufficient); and in Comparative Example 3, the solid-liquid ratio was too high, which slowed the diffusion between the reactants and affected the reaction effect. In Comparative Example 4, oxalic acid was used for acid leaching, which only utilized the effect of single oxalic acid leaching. In contrast, the present invention utilizes oxalate ester hydrolyzed into oxalic acid and methanol during the acid leaching reaction, with methanol also playing a very important role. Therefore, the embodiment is more effective than single oxalic acid leaching (Comparative Example 4).

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A short-range cleaning method for recycling key metals from retired lithium batteries, characterized in that: The following steps are involved: Discharging, disassembling and stripping retired lithium batteries to obtain positive electrode powder; subjecting the positive electrode powder, oxalate and water to a leaching reaction to obtain a slurry; performing solid-liquid separation on the slurry to obtain leachate and leach residue; adding sodium carbonate to the leachate to carry out lithium precipitation reaction to obtain lithium precipitation slurry; After solid-liquid separation of the lithium precipitated slurry, a lithium-containing solid is obtained; After washing and drying the lithium-containing solid, a battery-grade lithium carbonate product is obtained; The mass ratio of the positive electrode powder to the oxalate ester is 1:0.1-15, the solid-liquid ratio of the positive electrode powder to the oxalate ester aqueous solution is 10-700 g / L, and the leaching reaction temperature is 30-200°C.

2. The method according to claim 1, characterized in that The retired lithium batteries include one or more of retired lithium iron phosphate batteries, retired ternary lithium batteries, retired lithium cobalt oxide batteries and retired lithium manganese oxide batteries.

3. The method according to claim 1, characterized in that The oxalate ester includes one or more of dimethyl oxalate, diethyl oxalate and dipropyl oxalate.

4. The method according to claim 1, wherein The method comprises at least one of the following technical features: the leaching reaction is carried out by stirring and heating, the stirring rate is 50-600 rpm, and the stirring time is 0.5-8 h.

5. The method according to claim 1, wherein The method comprises at least one of the following technical features: the lithium precipitation reaction is carried out by stirring and heating, the temperature is 60-100°C, and the stirring time is 1-3 hours.

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