Method for recycling lithium in positive electrode material of waste lithium ion battery

Abstract

The invention relates to the technical field of waste battery raw material recovery, in particular to a method for recovering lithium in a waste lithium ion battery positive electrode material. The method comprises the following steps of: discharging the waste lithium ion battery, disassembling to obtain a complete positive plate, soaking the positive plate in a stripping agent to separate pole powder from the positive plate to obtain a mixed solution containing the pole powder, screening, roasting and reducing to obtain nickel cobalt manganese, and selectively extracting lithium by alkaline leaching. And concentrating and causticizing the extracted lithium solution to prepare lithium hydroxide. According to the method, the positive plate and the diaphragm are transferred into the stripping agent, and are soaked in the stripping agent for a certain time, so that the pole powder can be quickly and efficiently stripped from the positive plate, and the pole powder, the diaphragm and the aluminum foil are separated, the recovery rate and the recovery speed of the pole powder in the waste lithium battery are improved, and the lithium-containing leaching solution obtained after selective lithium extraction is concentrated and causticized; a lithium hydroxide product is obtained. By adopting the method, the yield of the metal lithium in the whole treatment process reaches 92% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of waste battery raw material recycling, and in particular to a method for recycling lithium in waste lithium-ion battery positive electrode materials. Background Art

[0002] When lithium batteries reach a balanced state as a new energy source, the main source of resources needed to manufacture new lithium batteries will shift from mining resources to recycled resources. The recycling of used lithium batteries and the resource utilization of used lithium-ion batteries will become a very urgent issue. All kinds of retired and scrapped used lithium batteries and used electrodes will become valuable urban mines.

[0003] Scrap lithium battery cathode materials contain valuable metals such as cobalt, nickel, and lithium, which have high recycling value. Lithium is one of the most important components in battery materials, making the harmless treatment of scrap batteries and the recovery of their lithium metal resources of great significance. Currently, wet processing for scrap lithium battery recycling is a well-researched and relatively mature process, consisting of three main stages: pretreatment, leaching, and the separation and recovery of valuable metals from the leachate, typically using solvent extraction and precipitation. Pretreatment involves crushing and sorting the battery, combining the electrode materials with other materials under mechanical action through multiple stages of crushing and screening, achieving material separation and enrichment. Existing technologies often employ mechanical and physical processes in the first stage of pretreatment, which fails to achieve high levels of processing efficiency or nickel, cobalt, manganese, and lithium recovery rates. These processes also result in high energy consumption and low recovery efficiency. Leaching, precipitation, or extraction in wet recovery processes can achieve high nickel, cobalt, and manganese recovery rates, but lithium recovery is low, reagent consumption is high, and the complex process leads to high energy consumption.

[0004] Therefore, it is necessary to develop a method that can efficiently recover lithium from spent batteries. Summary of the Invention

[0005] In order to solve the problems in the prior art, the present invention proposes the following technical solutions:

[0006] A method for recovering lithium from waste lithium-ion battery cathode materials comprises the following steps:

[0007] Step 1: After discharging the used lithium-ion battery, place it in the air and disassemble the positive electrode;

[0008] Step 2: Immerse the positive electrode sheet in an oxidizing stripping agent for 0.5-1 hour to obtain a mixed solution containing electrode powder;

[0009] Step 3: Sieve the mixed solution using a sieve with a pore size greater than 0.5 cm, vacuum filter the sieve and dry it to obtain a mixed powder;

[0010] Step 4: mechanically mixing the mixed electrode powder and the activator and placing them in a calcining furnace for calcination; the activator is sulfate;

[0011] Step 5: The calcined mixed electrode powder is subjected to alkali leaching. After the alkali leaching is completed, the filter is filtered to obtain a filter residue and a filtrate. The nickel, cobalt and manganese in the filter residue enter the wet recovery process;

[0012] Step 6: The filtrate is concentrated on an evaporative crystallizer, and after concentration, sodium hydroxide solution is added for causticization.

[0013] Step 7: The causticized lithium-containing solution is evaporated and crystallized to obtain a lithium hydroxide product.

[0014] Furthermore, the components of the stripping agent are divided into: 1 part of sodium dihydrogen phosphate solution, 2-6 parts of sodium pyrosulfate solution, 2-4 parts of sodium sulfite, and 1 part of 30% hydrogen peroxide; the concentrations of sodium dihydrogen phosphate solution, sodium pyrosulfate solution and sodium sulfite are the same, all 4-6g / L.

[0015] Furthermore, the mass ratio of the activator to the mixed electrode powder in step 4 is 1:1;

[0016] Furthermore, the calcination temperature in step 4 is 450-650° C., and the calcination time is 2-6 hours.

[0017] Furthermore, the concentration of the alkali solution in step 5 is 0.1 mol / L, the solid-liquid ratio of the mixed pole powder and the alkali solution is 1:5-10, the alkali immersion time is 1h-1.5h, and the alkali immersion temperature is 70℃-85℃.

[0018] Furthermore, the concentration temperature of the evaporation crystallizer in step 6 is 75°C-90°C.

[0019] Furthermore, the pH value at the causticization endpoint in step 6 is 13-14.

[0020] Furthermore, the evaporation concentration temperature in step 7 is 75°C-90°C.

[0021] The beneficial effects of the present invention are:

[0022] (1) The stripping agent used in the present invention can quickly and efficiently strip the electrode powder from the positive electrode sheet, thereby separating the electrode powder from the separator and the aluminum foil, thereby improving the recovery rate and recovery speed of the electrode powder in waste lithium batteries, and avoiding the problems of high energy consumption, dust emission, and low metal recovery rate caused by the long process of calcination, crushing, and sorting in lithium battery recycling. The lithium recovery rate of the entire process reaches more than 92%;

[0023] (2) Through the process steps of screening, roasting, alkali leaching, etc., the lithium in the pole powder can be selectively extracted. In particular, through the screening operation, the pole powder and the diaphragm can be completely separated efficiently and quickly, and the separation effect is good. Through the steps of roasting and alkali leaching, it has the advantage of selective extraction of lithium, and the alkali leaching achieves a high leaching rate of lithium. The sulfate added during roasting can play an activation role, so that the lithium is better released, which provides a basis for the subsequent efficient recovery of lithium;

[0024] (3) The present invention has a wide range of applications. By using a method of causticization followed by evaporation and crystallization, lithium in a lithium-containing solution is converted into a lithium hydroxide product, thereby avoiding the problems of low lithium yield and a single product when preparing crude lithium carbonate by precipitation of sodium carbonate. Furthermore, the present invention meets the current market demand for lithium hydroxide in the development of high-nickel cathode materials.

[0025] The present invention fundamentally solves the current problems in the industry such as low metallic lithium yield in waste power lithium battery powder and long processing flow for preparing lithium products, truly realizes efficient recycling and reuse of metallic lithium, and has certain economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0027] Figure 1 Shown is a process flow chart of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] Example 1

[0030] (1) After discharging the waste lithium-ion battery, place it in the air for disassembly to obtain a complete positive electrode sheet.

[0031] (2) The positive electrode sheet is immersed in a stripping agent for 0.5 hours. The components in the stripping agent are divided by weight into: 1 part of 5g / L sodium dihydrogen phosphate solution, 3 parts of 5g / L sodium pyrosulfate solution, 2 parts of 5g / L sodium sulfite solution, and 1 part of 30% hydrogen peroxide. The immersion in the stripping agent can separate the electrode powder on the positive electrode sheet from the positive electrode sheet, that is, the positive electrode sheet is separated into graded powder, diaphragm and aluminum foil to obtain a mixed solution containing electrode powder. The stripping operation is carried out using a stripping agent, which is efficient and fast, and has a good stripping effect. It can effectively separate the electrode powder, diaphragm and aluminum foil, and remove unusable substances.

[0032] (3) Use a large-aperture sieve (aperture greater than 0.5 cm) to screen the mixed solution and screen out the solution containing the pole powder, that is, remove the diaphragm and aluminum foil in the solution, and then vacuum filter the solution containing the pole powder. Vacuum filtration can remove some other impurities in the solution containing the pole powder, and vacuum drying is used to dry the water to obtain a mixed pole powder.

[0033] (4) The mixed electrode powder and the activator sodium sulfate are mixed in a mass ratio of 1:1 and then placed in a calcining furnace for roasting at a temperature of 550°C for 3 hours. The nickel, cobalt and manganese in the electrode powder are reduced by roasting.

[0034] (5) Alkali solution was added to the calcined mixed electrode powder at a liquid-solid ratio of 10:1 for alkaline leaching. The concentration of the alkaline solution was 0.1 mol / L, the alkali leaching time was 1.5 h, and the temperature was 80°C. After the alkaline leaching was completed, the filter residue and filtrate were obtained by filtration. The contents of nickel, cobalt and manganese in the filtrate were all lower than 0.005 g / L after testing. Therefore, it can be judged that nickel, cobalt and manganese elements were all filtered into the filter residue, while the lithium element in the mixed electrode powder was dissolved in the filtrate. Finally, the filtrate was concentrated to increase the concentration of lithium element in the solution.

[0035] (6) The concentrated lithium-containing solution was causticized by adding 150 g / L sodium hydroxide solution (1.0 times the theoretical amount) to the solution, and the end point pH value was 13.

[0036] (7) The causticized liquid was passed into an evaporation crystallizer for evaporation crystallization at a temperature of 85°C. After evaporation crystallization, the lithium hydroxide product was obtained by centrifugation, and the lithium recovery rate reached 92.3%.

[0037] Example 2

[0038] (1) After discharging the waste lithium-ion battery, place it in the air for disassembly to obtain a complete positive electrode sheet.

[0039] (2) The positive electrode sheet is immersed in a stripping agent for 0.6 hours. The components in the stripping agent are divided by weight as follows: 1 part of a sodium dihydrogen phosphate solution with a concentration of 5g / L, 2 parts of a sodium pyrosulfate solution with a concentration of 5g / L, 4 parts of a sodium sulfite solution with a concentration of 5g / L, and 1 part of 30% hydrogen peroxide. The electrode powder on the positive electrode sheet can be separated from the positive electrode sheet by soaking in the stripping agent, that is, the positive electrode sheet is separated into electrode powder, a diaphragm and an aluminum foil to obtain a mixed solution containing electrode powder. The stripping agent is used for stripping, which is efficient and fast, and has a good stripping effect. It can effectively separate the electrode powder, the diaphragm and the aluminum foil, and remove the unusable substances.

[0040] (3) Use a large-aperture sieve (aperture greater than 0.5 cm) to screen the mixed solution and filter out the solution containing the pole powder, that is, remove the diaphragm and aluminum foil in the solution. Then, vacuum filter the solution containing the pole powder to remove impurities, and then dry the water to obtain a mixed pole powder.

[0041] (4) The mixed electrode powder and the activator sodium sulfate were mixed in a mass ratio of 1:1 and placed in a calcining furnace for calcination at a temperature of 600°C for 2 hours.

[0042] (5) Alkali solution was added to the calcined mixed electrode powder at a liquid-solid ratio of 5:1 for alkaline leaching. The concentration of the alkaline solution was 0.1 mol / L. The purpose of alkaline leaching was to achieve a high lithium leaching rate. The alkaline leaching time was 1 h and the alkaline leaching temperature was 85°C. After the alkaline leaching was completed, the filter residue and filtrate were obtained by filtration. The contents of nickel, cobalt and manganese in the filtrate were all lower than 0.005 g / L after testing. Therefore, it can be judged that nickel, cobalt and manganese elements were all filtered into the filter residue, while the lithium element in the mixed electrode powder was dissolved in the filtrate. Finally, the filtrate was concentrated to increase the concentration of lithium element in the solution.

[0043] (6) The concentrated lithium-containing solution was causticized by adding 150 g / L sodium hydroxide solution (1.2 times the theoretical amount) to the solution, and the end point pH value was 14.

[0044] (7) The causticized liquid was passed into an evaporation crystallizer for evaporation crystallization at a temperature of 80°C. After evaporation crystallization, the lithium hydroxide product was obtained by centrifugation, and the lithium recovery rate reached 93.3%.

[0045] Some exemplary embodiments of the present invention are described above. It will be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. The features in these embodiments can be recombined in an appropriate manner, and the solutions obtained thereby are still within the scope of protection claimed by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A method for recovering lithium from waste lithium-ion battery cathode materials, characterized in that: The following steps are involved: Step 1: After discharging the used lithium-ion battery, place it in the air and disassemble the positive electrode; Step 2: Immerse the positive electrode sheet in an oxidizing stripping agent for 0.5-1 hour to obtain a mixed solution containing electrode powder; Step 3: Sieve the mixed solution using a sieve with a pore size greater than 0.5 cm, vacuum filter the sieve material and dry it to obtain a mixed powder; Step 4: mechanically mixing the mixed electrode powder and the activator and placing them in a calcining furnace for calcination; the activator is sulfate; Step 5: The calcined mixed electrode powder is subjected to alkali leaching. After the alkali leaching is completed, the filter is filtered to obtain a filter residue and a filtrate. The nickel, cobalt and manganese in the filter residue enter the wet recovery process; Step 6: The filtrate is concentrated on an evaporative crystallizer, and after concentration, sodium hydroxide solution is added for causticization. Step 7: The causticized lithium-containing solution is evaporated and crystallized to obtain a lithium hydroxide product.

2. The method for recovering lithium from waste lithium-ion battery cathode materials according to claim 1, wherein: The components of the stripping agent are divided into: 1 part of sodium dihydrogen phosphate solution, 2-6 parts of sodium pyrosulfate solution, 2-4 parts of sodium sulfite, and 1 part of 30% hydrogen peroxide; the concentrations of sodium dihydrogen phosphate solution, sodium pyrosulfate solution and sodium sulfite are the same, all 4-6g / L.

3. The method for recovering lithium from waste lithium-ion battery cathode materials according to claim 1, wherein: The mass ratio of the activator to the mixed pole powder in step 4 is 1:

1.

4. The method for recovering lithium from waste lithium-ion battery cathode materials according to claim 1, wherein: The calcination temperature in step 4 is 450-650° C., and the calcination time is 2-6 hours.

5. The method for recovering lithium from waste lithium-ion battery cathode materials according to claim 1, wherein: The concentration of the alkali solution in step 5 is 0.1 mol / L, the solid-liquid ratio of the mixed pole powder and the alkali solution is 1:5-10, the alkali immersion time is 1h-1.5h, and the alkali immersion temperature is 70℃-85℃.

6. The method for recovering lithium from waste lithium-ion battery cathode materials according to claim 1, characterized in that: The concentration temperature of the evaporation crystallizer in step 6 is 75°C-90°C.

7. The method for recovering lithium from waste lithium-ion battery cathode materials according to claim 1, characterized in that: The pH value at the causticization endpoint in step 6 is 13-14.

8. The method for recovering lithium from waste lithium-ion battery cathode materials according to claim 1, wherein: The evaporation concentration temperature in step 7 is 75°C-90°C.

Images