CN118851215A - A method for recycling waste lithium-ion batteries by sulfurization and roasting - Google Patents

Abstract

The present invention is a method for recycling waste lithium-ion batteries by sulfurization roasting, which can be applied to the recovery of lithium cobalt oxide positive electrode materials. Its main process is mixed grinding + sulfurization roasting + leaching solid-liquid separation + precipitation reaction to produce lithium carbonate. It can achieve the separation of lithium and cobalt in the positive electrode material, thereby recovering the two parts of the material to re-realize the preparation of high-performance positive electrode materials. In the actual implementation of this patent, due to the significant difference in water solubility between Li and the sulfides of most metals (such as Co, Ni, Fe), waste _LiCoO2 positive electrode materials can be recovered by sulfuric acid roasting of pyrite. In the process of lithium cobalt oxide recovery, lithium usually enters the solution in the form of compounds, and other elements enter the slag phase, and then solid-liquid separation is used to achieve the separation of lithium and other elements.

Description

A method for recycling waste lithium-ion batteries by sulfurization and roasting

Technical Field

The invention relates to the technical field of lithium battery recycling, and in particular to a method for recycling waste lithium ion batteries by sulfurization and roasting.

Background Art

As the earliest commercialized lithium-ion battery material, lithium cobalt oxide cathode material has set off a wave of research and commercialization of lithium-ion batteries. However, with the rapid replacement of portable electronic products and the accelerated development of new energy technologies, a large number of lithium-ion batteries are being discarded. The resulting battery recycling problem is becoming increasingly serious.

Pyrometallurgy and hydrometallurgy are the two main methods for recycling waste lithium-ion batteries. In the traditional pyrometallurgical treatment process of waste lithium positive electrode materials, lithium often enters the slag phase or volatilizes into the smoke in the form of lithium halides (LiF and LiCl), which makes it difficult to separate and recover lithium. In the hydrometallurgical recovery process, although the leaching rate of valuable metals is high, the concentration of lithium in the leachate is much lower than that of valuable metals such as nickel and cobalt, so the recovery of lithium is at the back end of the process. After multiple steps such as extraction and precipitation, the final lithium recovery rate is less than 80%. Recent studies have shown that only when the Li ⁺ concentration in the leachate is higher than 20g/ _L , the recovery rate of _Li can reach 80% when _Li2CO3 is produced using _Na2CO3 . The traditional process requires recirculation leaching to increase the concentration of Li ⁺ , resulting in a large loss of Li ⁺ in each cycle. Therefore, it is urgent to achieve selective separation and efficient recovery of lithium.

Salt-assisted roasting processes such as sulfuric acid roasting, chlorination roasting, and nitration roasting can reduce the roasting temperature and achieve the recovery of valuable metals. However, most of the precious metals in the roasting products exist in the form of soluble salts, which makes it challenging to selectively separate and extract lithium by simple water leaching.

Pyrite ( _FeS2 ) is a common sulfide mineral in nature, which produces _S2 gas upon thermal decomposition. This gas can promote the conversion of oxides in ores or silicates in smelting slag into sulfides, which is beneficial for flotation separation and further processing. Since there is a significant difference in water solubility between Li and most metal sulfides (such as Co, Ni, and Fe), the use of pyrite sulfidation to preferentially recover Li from waste _LiCoO2 cathode materials is a feasible approach.

Summary of the invention

The present invention provides a method for recycling waste lithium-ion batteries by sulfurization and roasting, which uses sulfurization and roasting combined with water leaching to achieve the recycling of waste lithium-ion batteries, especially the positive electrode materials of lithium cobalt oxide-based batteries. The technical scheme adopted is: mixed material grinding + sulfurization and roasting + leaching solid-liquid separation + precipitation reaction to prepare lithium carbonate + post-treatment.

Furthermore, the mixing and grinding process requires that the waste lithium cobalt oxide positive electrode and pyrite with ferrous sulfide (FeS ₂ ) as the main component are placed in an agate mortar or a stirring device, and anhydrous ethanol is added and ground and stirred together to obtain a product 1, whose main components are still lithium cobalt oxide and FeS ₂ .

Furthermore, the sulfurization roasting process puts product 1 into a tubular furnace. In this process, pyrite is used as a sulfur source. The recycling of positive electrode materials for lithium-ion batteries is achieved by roasting with nitrogen atmosphere to strengthen heating, and product 2 is obtained, the main components of which are lithium sulfate and cobalt and iron sulfides. In the tubular furnace, the entire roasting process is first purged with a flow rate of 100-350mL/min for 15-60min, and then the gas flow rate is reduced to 10-50mL/min for roasting, and then the roasted material is heated to 700°C at a heating rate of 5°C/min, and maintained for 7-12 hours, and finally slowly cooled at a rate of 5°C/min.

Furthermore, according to the method for recycling waste lithium-ion batteries by sulfurization roasting according to claim 1, in the leaching solid-liquid separation process, the product 2 is ground and leached in deionized water with mechanical stirring for 1 hour at a fixed liquid-solid ratio of 10ml:1g, a leaching temperature of 40°C, and a mechanical stirring speed of 100-230r/min. The leached material is then filtered and separated to selectively separate the liquid containing Li ₂ SO ₄ , while the residue is enriched with sulfides of Co and Fe. The slag obtained in this step is called product 3, and the liquid containing Li ₂ SO ₄ is called product 4.

Furthermore, the step of preparing lithium carbonate by precipitation reaction is to add product 4 into sodium carbonate solution, filter, wash to obtain the final product - filter residue Li ₂ CO ₃ , evaporate and concentrate the filtrate, cool and crystallize to recover Na ₂ SO ₄ ·10H ₂ O.

Furthermore, the post-processing step refers to recovering the Co and Fe sulfides obtained above as non-ferrous minerals by pyrometallurgical method to obtain valuable components therein.

The advantages of this patent are mainly reflected in the following aspects: (1) A method for extracting valuable components of lithium and cobalt from lithium-ion batteries by sulfurization roasting is proposed, which has good environmental and economic benefits. (2) The prepared lithium carbonate has not only a high total yield, but also a high purity, which can reach 98.5%, which can meet the battery grade use standards. (3) The electrochemical performance of high-purity lithium carbonate is better than that of traditional recovery processes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a method for recovering waste lithium-ion batteries by sulfurization and roasting according to a first embodiment of the present invention.

DETAILED DESCRIPTION

The present invention is further described below by means of specific examples, but the present invention is not limited thereto.

Example 1

For the waste lithium cobalt oxide batteries produced by a battery company in Shenzhen, the main element composition of the pyrite used for sulfuric acid roasting was measured after being dissolved in aqua regia: its main component is FeS ₂ , and there are also a small amount of Fe ₇ S ₈ and Si. The recovery rate of lithium carbonate synthesized by sulfuric acid roasting reached 99%, with strip-shaped distribution, small particles, and no other impurities on the surface. To further verify the purity of the synthesized Li ₂ CO ₃ , a small amount of synthetic material was dissolved in nitric acid, and the content of the main element Li and other impurity ions was tested by ICP at a constant volume. The result showed that the purity of the synthesized Li ₂ CO ₃ reached 98.50%, containing a small amount of impurities such as Na ⁺ and SO ₄ ^2- .

Finally, a button-type battery with lithium cobalt oxide positive electrode material prepared using synthesized lithium carbonate has a first-cycle discharge capacity of 155.24 mAh/g, a first-cycle charge capacity of 167.42 mAh/g, and a calculated first-cycle coulombic efficiency of 92.7%. After 100 cycles at 1C, the discharge capacity is 133.42 mAh/g, and the capacity retention rate is 85.9%.

In comparison, the first-cycle discharge capacity of the traditional battery positive electrode recovered by the physical sorting-chemical leaching method is 153.24mAh/g, and the first-cycle charge capacity is 162.42mAh/g, which is also stronger, and the cost of this method is also lower.

Example 2

For the waste lithium cobalt oxide batteries produced by a battery company in Changsha, the same pyrite as in Example 1 was used as the sulfur source, and finally the lithium carbonate with a recovery rate of 99% was synthesized by sulfuric acid roasting. The lithium carbonate was distributed in strips and blocks, with small particles and no other impurities on the surface. To further verify the purity of the synthesized Li ₂ CO ₃ , a small amount of the synthetic material was dissolved in nitric acid, and the content of the main element Li and other impurity ions was tested by ICP at a constant volume. The result showed that the purity of the synthesized Li ₂ CO ₃ reached 97.90%, containing a small amount of impurities such as Na ⁺ and SO ₄ ^2- .

Finally, a button-type battery with lithium cobalt oxide positive electrode material prepared using synthesized lithium carbonate has a first-cycle discharge capacity of 155.24 mAh/g, a first-cycle charge capacity of 167.42 mAh/g, and a calculated first-cycle coulombic efficiency of 92.7%. After 100 cycles at 1C, the discharge capacity is 133.42 mAh/g, and the capacity retention rate is 85.9%.

In comparison, the first-cycle discharge capacity of the traditional battery positive electrode recovered by the physical sorting-chemical leaching method is 153.24mAh/g, and the first-cycle charge capacity is 162.42mAh/g, which is also stronger, and the cost of this method is also lower.

Claims (6)

1. A method for recycling waste lithium ion batteries by vulcanization roasting is characterized in that the waste lithium ion batteries, especially the positive electrode materials of lithium cobalt oxide-based batteries, are recycled by using a vulcanization roasting combined water leaching process. The technical scheme adopted is as follows: mixing grinding, vulcanization roasting, leaching solid-liquid separation and precipitation reaction to prepare lithium carbonate and carrying out aftertreatment.

2. The method for recycling waste lithium ion batteries by vulcanization roasting according to claim 1, wherein the mixing grinding process is to put the waste lithium cobalt oxide anode and pyrite taking ferrous sulfide (FeS ₂) as main components into an agate mortar or stirring equipment, and simultaneously adding absolute ethyl alcohol to grind and stir together to obtain a product I, wherein the components are mainly lithium cobalt oxide and FeS ₂.

3. The method for recycling waste lithium ion batteries through vulcanization roasting, according to claim 1, wherein the first product is placed into a tube furnace in the vulcanization roasting process, pyrite is used as a sulfur source in the process, and the positive electrode material of the lithium ion batteries is recycled by roasting with the aid of intensified heat in a nitrogen atmosphere, so that the second product is obtained, and the main components of the second product are lithium sulfate and cobalt and iron sulfides. In a tube furnace, the whole roasting process is firstly purged for 15-60min by using a flow of 100-350mL/min, then the gas flow is reduced to 10-50mL/min for roasting, the roasted material is heated to 700 ℃ at a heating rate of 5 ℃/min, the temperature is kept for 7-12 hours, and finally the temperature is slowly reduced at a speed of 5 ℃/min.

4. The method for recycling waste lithium ion batteries through vulcanization roasting, according to claim 1, wherein the leaching solid-liquid separation process is to grind the second product, and leaching is carried out in deionized water by mechanically stirring for 1h according to a fixed liquid-solid ratio of 10ml to 1g, wherein the leaching temperature is 40 ℃ and the mechanical stirring speed is 100-230 r/min. And filtering and separating the leached material to separate liquid containing Li ₂SO₄ selectively, wherein Co and Fe sulfide are enriched in the residue, the obtained residue is called product III, and the liquid containing Li ₂SO₄ is called product IV.

5. The method for recycling waste lithium ion batteries by vulcanization roasting according to claim 1, wherein the step of preparing lithium carbonate by precipitation reaction is to add a product IV into sodium carbonate solution, filter, wash and obtain a final product-filter residue Li ₂CO₃, evaporate and concentrate filtrate, cool and crystallize and recycle the filtrate to obtain Na ₂SO₄·10H₂ O.

6. The method for recycling waste lithium ion batteries by vulcanization roasting according to claim 1, wherein the post-treatment step is to recycle sulfide of Co and Fe obtained by the method as colored ore fire to obtain valuable components.