Method for utilizing biomass to assist in leaching spent ternary lithium battery cathode material

Abstract

The application belongs to the technical field of waste lithium battery recycling and reuse, and discloses a method for leaching positive electrode material of waste ternary lithium battery by using biomass as an auxiliary agent, wherein waste ternary positive electrode powder and biomass reducing agent are mixed, and leaching reaction is carried out under the condition of heating and stirring, and the biomass reducing agent is broadleaf wood hydrolysate and / or coniferous wood hydrolysate; the hydrolysate of agricultural and forestry waste such as broadleaf wood or coniferous wood is used as a green reducing agent, and the leaching rate of Ni, Co, Mn and Li can reach more than 98% under mild conditions at 30 DEG C; the method has the advantages of low cost, environmental friendliness, safety and high efficiency, and realizes resource recycling and utilization by waste treatment.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium battery recycling technology, specifically relating to a method for leaching waste ternary lithium battery cathode materials using biomass-assisted leaching. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Lithium-ion batteries, especially ternary (NCM or NCA) lithium batteries, are widely used in electric vehicles and portable electronic devices due to their high energy density and long cycle life. As these batteries reach the end of their lifespan, the number of used batteries is increasing dramatically. These used batteries not only contain precious metals such as lithium, nickel, cobalt, and manganese, but also hazardous components, posing serious environmental risks if not disposed of properly. Therefore, developing efficient and economical recycling technologies has significant resource value and environmental implications.

[0004] Currently, the mainstream recycling method for spent ternary lithium batteries is hydrometallurgical processing. This process typically uses inorganic acids (such as H2SO4) to leach valuable metals from the cathode material. Because nickel, cobalt, and manganese in ternary cathode materials are usually in a high oxidation state (Ni³⁺),... + Co³ + Mn 4+ In acidic media, it is not easily dissolved directly, so a reducing agent needs to be added during the leaching process to reduce the high-valence metal ions to a low-valence state (Ni²). + Co² + Mn² + This process disrupts the crystal structure and promotes leaching. However, the use of reducing agents in existing processes has significant drawbacks: commonly used hydrogen peroxide (H2O2) poses significant safety hazards during transportation and storage, and is easily decomposed and ineffective under heating conditions; inorganic reducing agents (such as Na2SO3) introduce impurity ions (Na+). + S² - This significantly increases the difficulty and cost of subsequent separation and purification; while organic reducing agents such as glucose are environmentally friendly, their production costs are high, and they are derived from food resources, posing a potential problem of "competing with humans for food." Therefore, there is an urgent need to develop a new reduction system that is widely available, low-cost, and environmentally friendly. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for leaching spent ternary lithium battery cathode materials using biomass-assisted leaching. This method utilizes hydrolysate from forestry or agricultural waste as a green reducing agent, replacing traditional hazardous chemicals, to efficiently leach valuable metals from spent ternary cathode materials under acidic conditions, achieving "waste treatment of waste" and resource utilization.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: A method for leaching spent ternary lithium battery cathode materials using biomass-assisted leaching, characterized by the following steps: (1) The waste ternary lithium battery is separated to obtain the positive electrode sheet, and the positive electrode sheet is pretreated to obtain the waste ternary positive electrode powder. (2) The obtained waste ternary cathode powder and biomass reducing agent are mixed and leached under heating and stirring conditions; (3) After the leaching reaction is completed, solid-liquid separation is performed to obtain ion leachate.

[0007] Furthermore, the biomass reducing agent is a hardwood hydrolysate and / or a softwood hydrolysate. Under acid catalysis, the hardwood or softwood hydrolysate degrades into various reducing sugars such as xylose, mannose, arabinose, and galactose. Lignin degradation produces phenolic compounds, and the phenolic hydroxyl groups act as rapid electron donors, quickly reducing high-valence metals. These various reducing sugars continuously provide reduction sites, forming a highly efficient reduction system that together reduces Ni³⁺. + Co³ + Mn 4+ It is reduced to a low-valence ion that is easily soluble in acid, thereby improving the leaching efficiency of nickel, cobalt, and manganese.

[0008] Furthermore, the broadleaf wood hydrolysate is prepared by the following method: adding the broadleaf wood raw material to pure water, heating it in a high-pressure reactor at 175°C for 1 h, cooling it, centrifuging to collect the supernatant and concentrating it; or adding the broadleaf wood raw material to a 0.5% sulfuric acid solution, heating it in a high-pressure reactor at 140°C for 1 h, cooling it, centrifuging to collect the supernatant and concentrating it.

[0009] Furthermore, the coniferous wood hydrolysate is prepared by adding coniferous wood raw material to pure water, heating it in a high-pressure reactor at 175°C for 1 h, cooling it, centrifuging it to obtain the supernatant and concentrating it; or adding coniferous wood raw material to 0.5% sulfuric acid solution, heating it in a high-pressure reactor at 140°C for 1 h, cooling it, centrifuging it to obtain the supernatant and concentrating it.

[0010] Furthermore, the broadleaf wood hydrolysate contains sulfuric acid and has a xylan content of 30 g / L to 35 g / L, and the coniferous wood hydrolysate contains sulfuric acid and has a polymannose content of 30 g / L to 35 g / L.

[0011] Furthermore, the concentration of the sulfuric acid solution is 0.5 mol / L to 3.5 mol / L, and the mass-to-volume ratio of the waste ternary cathode powder to the sulfuric acid solution is 1:25.

[0012] Furthermore, the mass ratio of xylan in the broadleaf wood hydrolysate to the waste ternary cathode powder is 2-5:5, and the mass ratio of polymannose in the coniferous wood hydrolysate to the waste ternary cathode powder is 2-5:5.

[0013] Furthermore, the leaching reaction is carried out at a temperature of 10~90℃ for a reaction time of 0.5~2 h.

[0014] Furthermore, the preprocessing employs the following specific steps: (1) Manually break the positive electrode sheet, immerse the fragments in a 2.5 mol / L NaOH solution, and stir to dissolve the aluminum foil in a 60℃ water bath; (2) Filter and wash until neutral, place in a forced-air drying oven and dry at 120℃ for 12 h, then calcine at high temperature; (3) The waste ternary cathode powder is obtained by grinding and sieving.

[0015] Furthermore, the waste ternary lithium battery is a nickel-cobalt-manganese ternary lithium battery.

[0016] Furthermore, the calcination temperature is 500 ℃ and the calcination time is 3 h.

[0017] Furthermore, the grinding process employs a planetary ball mill with a grinding frequency of 25 Hz, a grinding time of 40 min, a ball-to-material ratio of 10:1, and sieving using an 80-mesh standard sieve.

[0018] The beneficial effects of the technical solution provided by this invention are: 1. Green and environmentally friendly with high safety: It completely eliminates the use of easily explosive and decomposable hydrogen peroxide and inorganic reducing agents that introduce impurities. The entire process is safe and controllable, with no secondary pollution, and conforms to the concept of green chemistry.

[0019] 2. Wide range of raw materials, “using waste to treat waste”: The reducing agent used in this invention can be directly derived from agricultural and forestry waste such as broad-leaved wood and coniferous wood. This not only avoids competing with humans for food, but also significantly reduces the recycling cost of waste batteries, realizing high-value utilization of biomass waste.

[0020] 3. Extremely high leaching efficiency and mild reaction conditions: Highly efficient leaching can be achieved at a reaction temperature of 30℃. The leaching rates of Ni, Co, Mn and Li in waste ternary cathode materials can all reach more than 98%, which significantly reduces energy consumption. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 SEM image of the cathode material after processing in Example 1 Detailed Implementation The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0023] The broadleaf wood hydrolysate was prepared by either of the following two methods: (1) Hydrothermal method: The broadleaf wood raw material was added to pure water and placed in a high-pressure reactor and heated at 175°C for 1 h. The xylan was degraded by self-hydrolysis under high-temperature hydrothermal conditions. After cooling, the supernatant was collected by centrifugation and concentrated. (2) Acid hydrolysis method: The broadleaf wood raw material was added to 0.5% sulfuric acid solution and placed in a high-pressure reactor and heated at 140°C for 1 h. The xylan was degraded by acid hydrolysis under high-temperature hydrothermal conditions. After cooling, the supernatant was collected by centrifugation and concentrated. The hydrolysate prepared by the above method was adjusted with sulfuric acid to obtain a broadleaf wood hydrolysate with a xylan content of 32 g / L and a sulfuric acid concentration of 2.5 mol / L.

[0024] The coniferous wood hydrolysate was prepared by either of the following two methods: (1) Hydrothermal method: The coniferous wood raw material was added to pure water and placed in a high-pressure reactor and heated at 175°C for 1 h. The xylan was degraded by self-hydrolysis under high-temperature hydrothermal conditions. After cooling, the supernatant was collected by centrifugation and concentrated. (2) Acid hydrolysis method: The coniferous wood raw material was added to 0.5% sulfuric acid solution and placed in a high-pressure reactor and heated at 140°C for 1 h. The xylan was degraded by acid hydrolysis under high-temperature hydrothermal conditions. After cooling, the supernatant was collected by centrifugation and concentrated. The hydrolysate prepared by the above methods was adjusted with sulfuric acid to obtain a coniferous wood hydrolysate with a xylan content of 32 g / L and a sulfuric acid concentration of 2.5 mol / L.

[0025] Example 1 Preparation of positive electrode powder: Waste NCM811 batteries were completely discharged and disassembled to obtain positive electrode sheets. The positive electrode sheets were manually crushed into 1 cm × 1 cm fragments; the fragments were immersed in a 2.5 mol / L NaOH solution and stirred in a 60℃ water bath for 120 min to dissolve the aluminum foil. The solution was then vacuum filtered and washed with pure water until neutral; the solution was placed in a forced-air drying oven and dried at 120℃ for 12 h; the solution was then calcined in a tube furnace at 500℃ for 3 h to remove carbon black and binder; finally, the solution was placed in a planetary ball mill and ball-milled at a frequency of 25 Hz for 40 min with a ball-to-material ratio of 10:1. The solution was then passed through an 80-mesh standard sieve to obtain waste ternary positive electrode powder.

[0026] Weigh 0.2 g of the above-mentioned cathode powder and add 5 ml of broadleaf wood hydrolysate with a xylan content of 32 g / L and a sulfuric acid concentration of 2.5 mol / L. The mass ratio of xylan to cathode powder in the broadleaf wood hydrolysate is 80%. Place the mixture in a 30℃ water bath and continuously stir for 1 h to digest. After the reaction is complete, transfer the mixture to a centrifuge tube and centrifuge at 10000 r / min for 10 min. Take the supernatant, dilute it with pure water to a fixed volume, and use inductively coupled plasma optical emission spectrometry (ICP-OES) to test the concentrations of metal ions Ni, Co, Mn, and Li, and calculate the leaching rate.

[0027] Leaching rate = Content of metal ions Ni, Co, Mn, and Li in the solution / Content of the corresponding metal ions in the battery cathode material * 100%.

[0028] Test results show that the leaching rates of Ni, Co, Mn and Li are all greater than 98.5% under the conditions of 10℃ and 30℃.

[0029] Example 2 The preparation of the positive electrode powder is the same as in Example 1.

[0030] This embodiment included a gradient comparison experiment of xylan to cathode powder mass ratios. To examine the effect of biomass addition ratio on leaching rate, 0.2 g of cathode powder and 5 mL of 2.5 mol / L H₂SO₄ solution were weighed. The xylan content in the broadleaf wood hydrolysate was 32 g / L. The mass ratios of xylan to cathode powder in the added broadleaf wood hydrolysate were 0%, 40%, 60%, 80%, and 100%, respectively. The mixture was placed in a 30℃ water bath and continuously stirred for 1 h for digestion. After the reaction, the mixture was transferred to a centrifuge tube and centrifuged at 10000 r / min for 10 min. The supernatant was collected, diluted with pure water, and the concentrations of metal ions Ni, Co, Mn, and Li were measured using ICP-OES. The leaching rate was then calculated.

[0031] Leaching rate = Content of metal ions Ni, Co, Mn, and Li in the solution / Content of the corresponding metal ions in the battery cathode material * 100%.

[0032] Test results show that without xylan (0%), high-valence Ni, Co, and Mn are extremely difficult to dissolve due to the lack of a reducing agent, resulting in a very low leaching rate of only 20%. When the xylan content is 40%, the leaching rate of each ion is only 97%. As the xylan content increases, the leaching rate of each metal increases significantly. When the mass ratio reaches 80% and 100%, the leaching rates of Ni, Co, Mn, and Li all exceed 99%.

[0033] Example 3 The preparation of the positive electrode powder is the same as in Example 1.

[0034] This embodiment included a gradient comparison experiment with sulfuric acid concentration to examine the effect of sulfuric acid concentration on the leaching rate. 0.2 g of positive electrode powder was weighed and added to 5 ml of a broadleaf wood hydrolysate with a xylan content of 32 g / L. The xylan-to-positive electrode material mass ratio in the broadleaf wood hydrolysate was 80%, and the H₂SO₄ concentrations were 0.5 mol / L, 2.5 mol / L, and 3.5 mol / L, respectively. The mixture was placed in a 30℃ water bath and continuously stirred for 1 h for digestion. After the reaction, the mixture was transferred to a centrifuge tube and centrifuged at 10000 r / min for 10 min. The supernatant was collected, diluted with pure water to a fixed volume, and the concentrations of metal ions Ni, Co, Mn, and Li were measured using ICP-OES. The leaching rate was then calculated.

[0035] Leaching rate = Content of metal ions Ni, Co, Mn, and Li in the solution / Content of the corresponding metal ions in the battery cathode material * 100%.

[0036] Test results show that when the H₂SO₄ concentration is 0.5 mol / L, the leaching rates of all metals are below 55% because the acidity is insufficient to disrupt the crystal structure. When the H₂SO₄ concentration reaches 2.5 mol / L, the leaching rates of Ni, Co, Mn, and Li jump to over 99%. When the concentration is further increased to 3.5 mol / L, the leaching rates do not show a significant increase and even fluctuate slightly.

[0037] Example 4 The preparation of the positive electrode powder is the same as in Example 1.

[0038] Weigh 0.2 g of positive electrode powder and add 5 ml of coniferous wood hydrolysate with a polymannose content of 32 g / L and a sulfuric acid concentration of 2.5 mol / L. The mass ratio of polymannose to positive electrode powder in the coniferous wood hydrolysate is 80%. Place the mixture in a 30℃ water bath and continuously stir for 1 h to digest. After the reaction is complete, transfer the mixture to a centrifuge tube and centrifuge at 10000 r / min for 10 min. Take the supernatant, dilute it with pure water to a fixed volume, and use ICP-OES to test the concentrations of metal ions Ni, Co, Mn, and Li, and calculate the leaching rate.

[0039] Leaching rate = Content of metal ions Ni, Co, Mn, and Li in the solution / Content of the corresponding metal ions in the battery cathode material * 100%.

[0040] Test results show that under mild conditions of 30℃, the leaching rates of Ni, Co, Mn and Li reached over 98%, demonstrating excellent leaching performance.

[0041] Comparative Example 1 The preparation of the positive electrode powder is the same as in Example 1.

[0042] Weigh 0.2 g of positive electrode powder and add 0.16 g of glucose, with a glucose-to-positive electrode powder mass ratio of 80%. Then add 5 mL of 2.5 mol / L H₂SO₄ solution. Place the mixture in a 30℃ water bath and stir continuously for 1 h to digest the reaction. After the reaction is complete, transfer the mixture to a centrifuge tube and centrifuge at 10000 r / min for 10 min. Take the supernatant, dilute it with pure water to a fixed volume, and use ICP-OES to test the concentrations of metal ions Ni, Co, Mn, and Li, and calculate the leaching rate.

[0043] Leaching rate = Content of metal ions Ni, Co, Mn, and Li in the solution / Content of the corresponding metal ions in the battery cathode material * 100%.

[0044] Test results show that at 30℃, the leaching rates of Ni, Co, Mn and Li are 62%, 54%, 68% and 81% respectively, which are poor and cannot achieve efficient recovery.

[0045] Comparative Example 2 The only difference was that the glucose was replaced with an equal mass of sucrose, while all other conditions were exactly the same as in Comparative Example 1.

[0046] Test results show that at 30℃, the leaching rates of Ni, Co, Mn and Li are 59%, 48%, 63% and 77%, respectively, which are low and cannot meet the requirements of industrial recycling.

[0047] The results showed that, regardless of whether xylan from hardwood or polymannose from softwood was used, the leaching rates of Ni, Co, Mn, and Li in waste ternary cathode materials could reach over 98% under mild conditions of 30℃. This indicates that using hardwood hydrolysate and / or softwood hydrolysate as reducing agents can effectively reduce and leach high-valence metal ions (Ni³⁺, Co, Mn, and Li) from waste ternary cathode materials. + Co³ + Mn 4+ The effect is excellent; however, when glucose and sucrose are used as reducing agents at 30℃, they cannot effectively reduce the high-valence metal ions in the ternary cathode material due to their weak reducing ability.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for leaching waste ternary lithium battery cathode materials using biomass-assisted leaching, characterized in that, The following steps are adopted: (1) The waste ternary lithium battery is separated to obtain the positive electrode sheet, and the positive electrode sheet is pretreated to obtain the waste ternary positive electrode powder. (2) The obtained waste ternary cathode powder and biomass reducing agent are mixed and leached under heating and stirring conditions; (3) After the leaching reaction is completed, solid-liquid separation is performed to obtain ion leachate.

2. The method according to claim 1, characterized in that, The waste ternary lithium batteries are nickel-cobalt-manganese lithium batteries.

3. The method according to claim 1, characterized in that, In step (2), the biomass reducing agent is broadleaf wood hydrolysate and / or coniferous wood hydrolysate.

4. The method according to claim 3, characterized in that, The broadleaf wood hydrolysate contains sulfuric acid and has a xylan content of 30 g / L to 35 g / L, while the coniferous wood hydrolysate contains sulfuric acid and has a polymannose content of 30 g / L to 35 g / L.

5. The method according to claim 4, characterized in that, The concentration of the sulfuric acid solution is 0.5 mol / L to 3.5 mol / L, and the mass-to-volume ratio of the waste ternary cathode powder to the sulfuric acid solution is 1:

25.

6. The method according to claim 3, characterized in that, The mass ratio of xylan in the broadleaf wood hydrolysate to the waste ternary cathode powder is 2-5:5, and the mass ratio of polymannose in the coniferous wood hydrolysate to the waste ternary cathode powder is 2-5:

5.

7. The method according to claim 1, characterized in that, In step (2), the leaching reaction is carried out at a temperature of 10~90℃ and for a reaction time of 0.5~2 h.

8. The method according to claim 1, characterized in that, In step (1), the preprocessing adopts the following specific steps: (1) After breaking the positive electrode sheet, immerse it in a sodium hydroxide solution; (2) Filter and wash until neutral, dry and then calcine at high temperature; (3) The waste ternary cathode powder is obtained by grinding and sieving.

9. The method according to claim 8, characterized in that, The calcination temperature is 500 ℃ and the calcination time is 3 h.

10. The method according to claim 8, characterized in that, The grinding process uses a planetary ball mill with a grinding frequency of 25 Hz, a grinding time of 40 min, and a ball-to-material ratio of 10:1.

Images