Method for processing waste electrode material

Abstract

This invention belongs to the field of waste battery material recycling, specifically disclosing a method for processing waste electrode materials. The method involves ball milling an FeS2 source followed by calcination at a protective atmosphere and a temperature above 550°C to obtain an activated FeS2 source. The waste electrode material containing waste positive electrode material and the activated FeS2 source are then slurried with water, heated and pressurized to a subcritical state, and subjected to heat and pressure holding treatment before depressurization, cooling, and solid-liquid separation to obtain a leachate enriched with metal elements from the positive electrode material. The weight ratio of the activated FeS2 source to the waste electrode material is above 0.5. The subcritical state temperature is above 180°C, and the pressure is above 1 MPa. The waste electrode material can also be black powder. This invention enables the combined processing of positive and negative electrodes, improving the metal recovery rate of the positive electrode. Furthermore, it facilitates the co-production of carbon materials with high electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery recycling technology, and in particular relates to the recycling of waste lithium-ion battery electrode materials. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles due to their unique electrochemical properties. According to EU statistics, the growth rate of electric vehicles is rapid, with production expected to reach 900 million units by 2048. Simultaneously, the end of the lifespan of lithium-ion batteries will lead to a large accumulation of waste lithium-ion batteries; forecasts indicate that 11 million tons of waste lithium-ion batteries will be produced by 2030. Because waste lithium-ion batteries contain large amounts of valuable and toxic metals (Li, Ni, Co, Mn), their effective recycling has attracted widespread attention.

[0003] Waste electrode materials mainly include waste positive electrode materials and waste negative electrode materials. Existing technologies mostly recycle waste positive and negative electrode materials separately. For example, valuable metal elements are separated from waste positive electrode materials through a roasting-leaching process; another example is the acid purification and carbon coating recovery of waste negative electrode materials to obtain carbon materials. Existing recycling processes for waste positive and negative electrodes are relatively long and generate significant amounts of waste. In addition, a few processes exist in the industry that combine waste positive and negative electrodes, but most of these combined processes use the waste as a carbon reducing agent, making it difficult to achieve efficient metal leaching while simultaneously producing high-electrochemical-performance carbon materials. Summary of the Invention

[0004] To address the shortcomings of traditional processes, the present invention aims to provide a FeS2-assisted subcritical treatment method for waste electrode materials, thereby offering a novel and highly efficient dual-efficiency recycling method for both positive and negative electrodes.

[0005] A method for processing waste electrode materials involves ball milling FeS2 source and then calcining and activating it under a protective atmosphere at a temperature above 550°C to obtain activated FeS2 source.

[0006] Waste electrode material containing waste cathode material and activated FeS2 source are slurried with water, heated and pressurized to a subcritical state, and then depressurized and cooled after heat preservation and pressure treatment, and solid-liquid separation is performed to obtain a leachate enriched with metal elements from the cathode material.

[0007] The weight ratio of activated FeS2 source to waste electrode material is above 0.5; the subcritical state temperature is above 180℃ and the pressure is above 1MPa.

[0008] In one embodiment of the present invention, the waste electrode material is waste positive electrode material. After the processing described in the present invention, a leachate enriched with the metal elements of the positive electrode material can be obtained through solid-liquid separation via subcritical treatment.

[0009] In another embodiment of the present invention, the waste electrode material is a mixture (black powder) comprising waste positive electrode material and waste negative electrode material. After subcritical treatment as described in this invention, solid-liquid separation is performed to obtain a leachate enriched with the metal elements of the positive electrode material. The collected solid is then acid-washed, water-washed, and dried to obtain carbon material. The acid used in the acid washing stage is an aqueous solution of an inorganic strong acid, such as an aqueous solution of sulfuric acid, hydrochloric acid, nitric acid, or HF, with a solute concentration of, for example, 0.1–5 M. The amount of acid used in the acid washing is not less than the theoretical amount; for example, acid washing continues until the filtrate is colorless.

[0010] In this invention, the waste electrode material can be obtained by peeling it off from the positive or negative electrode sheet of a waste battery using known methods.

[0011] For example, the positive electrode active material contained in the waste positive electrode material of the present invention can be an oxidizing lithium salt containing at least one metal element selected from Ni, Co, and Mn, which is commonly found in the industry; further, it can be at least one of lithium nickelate, lithium manganese oxide, nickel-manganese binary material, and NCM ternary material.

[0012] In this invention, the waste positive electrode material is also permitted to contain at least one of a conductive agent and a binder;

[0013] In this invention, the content of the positive electrode active material in the waste positive electrode material is above 50 wt.%, and considering the economic efficiency of the processing technology, it can be further 75-95 wt.%.

[0014] In this invention, the waste negative electrode material can be the material stripped from a negative electrode sheet, containing a negative electrode active material, and may also contain conductive agents and binders. The negative electrode active material is, for example, graphite. The content of the negative electrode active material in the waste negative electrode material is above 50 wt.%, and can be further increased to 75-95 wt.% considering the economic efficiency of the processing technology. In the black powder of this invention, there are no particular requirements for the weight ratio between waste positive electrode material and waste negative electrode material; for example, it can be 1-2:1-2.

[0015] This invention innovatively ball-mills and calcines FeS2 sources for activation, and innovatively uses the activated material to assist in the subcritical treatment of waste electrode materials. Furthermore, by jointly controlling the parameters of calcination temperature, FeS2 source ratio, and subcritical temperature and pressure, the process can achieve synergy and realize the efficient recovery of metal elements in cathode materials in one step. In addition, the structure and physicochemical properties of the obtained carbon materials can be repaired, enabling the co-production of carbon materials with high electrochemical performance.

[0016] In this invention, the FeS2 source is at least one of analytically pure materials, minerals, and solid waste containing FeS2;

[0017] In this invention, the FeS2 content in the FeS2 source is not particularly required. For example, it can be above 1 wt.%, and considering the ease of processing and raw material cost, it can be further above 10 wt.%, and even further, it can be 40-60 wt.%.

[0018] Preferably, the weight ratio of activated FeS2 source to waste electrode material is 0.5 to 5:1; more preferably, it is 1 to 2.5:1.

[0019] In this invention, the combined activation of FeS2 source by ball milling and calcination is the key to synergistically improving the effect of subsequent subcritical treatment and the recovery effect of electrode materials.

[0020] In this invention, the ball milling method is either dry ball milling or wet ball milling;

[0021] In this invention, the ball-to-material ratio during the ball milling stage can be adjusted as needed, for example, to 25–50:1. The ball milling speed and time can also be adjusted as needed, for example, the ball milling speed is 200–600 r / min. The ball milling time is more than 1 hour, more preferably 5–10 hours.

[0022] In this invention, the ball milling material is calcined, and the calcination temperature is further adjusted to modify the physicochemical structure of the FeS2 source. This can unexpectedly improve the subcritical treatment effect of the subsequent electrode materials, for example, improve the recovery rate of metal elements in the cathode, and also enable the use of carbon materials with high electrochemical performance.

[0023] Preferably, the temperature during the roasting stage is 600–1000°C;

[0024] Preferably, the roasting stage includes two heat preservation platforms, wherein the temperature of the first heat preservation platform is 600–700°C, and the temperature of the second heat preservation platform is 750–900°C. This invention has found that the two-stage roasting mechanism helps to further synergistically improve the subcritical treatment effect assisted by the activating material, improve the recovery of elements at the cathode, and co-produce carbon materials with high electrochemical performance.

[0025] Further optimization involves conducting the calcination stage under microwave assistance. This invention also found that calcination under optimized microwave assistance can further synergistically improve the recovery effect of the activated material on the electrode material in a subcritical system, improve the recovery of metals from the positive electrode, and improve the electrochemical performance of the recovered negative electrode.

[0026] Preferably, the microwave power is 500–1000W;

[0027] Preferably, the roasting time is 5 to 10 hours. When a two-stage roasting process is used, the holding time for the first and second stages can be 2.5 to 5 hours, respectively.

[0028] In this invention, waste electrode materials and activation materials can be slurried with water and then filled into a pressure-resistant container for heating and pressurization treatment.

[0029] In this invention, the liquid-to-solid ratio during the pulping stage is 20–50 mL / g;

[0030] In this invention, the filling volume of the pulped slurry in the pressure vessel required for subcritical treatment can be adjusted according to the preparation scale, for example, it can be 30-80 vol%.

[0031] In this invention, the subcritical temperature is 180–220°C and the pressure is 1–3.5 MPa.

[0032] In this invention, there are no special requirements for the heat preservation and pressure holding time under subcritical conditions. For example, it can be more than 5 hours. Considering the economic efficiency of the process, it can be further extended to 10 to 24 hours.

[0033] Beneficial effects

[0034] This invention innovatively ball-mills and calcines FeS2 sources for activation, and innovatively uses the activated material to assist in the subcritical treatment of waste electrode materials. Furthermore, it combines the joint control of parameters such as calcination temperature, FeS2 source ratio, and subcritical temperature and pressure. This process enables synergy and allows for the effective recycling of electrode materials in one step. For example, it can efficiently recover metal elements from cathode materials. Moreover, it can also perform physicochemical structural repair on carbon materials and simultaneously produce carbon materials with high electrochemical performance. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0036] In this invention, the terms "temperature" and "proportion" refer to values ​​above a certain value, which include that value.

[0037] In the following examples, pyrite, a widely available source of FeS2, is used as an example. There are no special requirements for the FeS2 content. In the following examples, as typical examples, unless otherwise stated, the FeS2 content is 50.1 wt%.

[0038] In the following examples, the waste cathode materials are obtained by stripping from waste cathode sheets, and the content of active materials therein is 70-85 wt.%. In the following examples, unless otherwise stated, the content of active cathode materials is 80-85 wt%.

[0039] Similarly, the waste negative electrode material is obtained by stripping from waste graphite negative electrode sheets, and the active material therein is graphite active material, the content of which can be 70-85 wt.%. In the following examples, as typical illustrations, unless otherwise stated, the content of the negative electrode active material is 80-85 wt%.

[0040] In the following examples, as typical illustrations, the ball milling method is dry ball milling, and the ball-to-material weight ratio is, for example, 30:1.

[0041] Example 1:

[0042] ① Pretreatment: The waste power nickel-cobalt-manganese lithium batteries were placed in 2mol / L brine for 30h discharge treatment. After discharge, the batteries were dried at 85℃, and the positive and negative electrode sheets were separated. The positive electrode sheets were soaked in N-methylpyrrolidone to remove the current collectors. After filtration, washing and drying, the waste positive electrode powder was obtained. Similarly, the negative electrode sheets were soaked in N-methylpyrrolidone to remove the current collectors. After filtration, washing and drying, the waste negative electrode powder was obtained.

[0043] ② Ball milling: Take 10g of pyrite and place it in a ball mill for mechanical activation. The speed is set to 400r / min and the time is 5h.

[0044] ③ Calcination: After the ball milling process is completed, the ball milled material is taken out and placed in a tube furnace for calcination in an argon atmosphere. The calcination temperature is 800℃ (marked as T1) and the time is 6h.

[0045] ④ Subcritical Leaching: 2g of waste cathode powder and 4g of roasted pyrite were placed together in a 500mL pressure vessel at a mass ratio of 1:2. 180mL of deionized water was added at a liquid-to-solid ratio of 30:1mL / g. The pressure vessel was heated to a subcritical state (temperature 200℃ (labeled T2), pressure controlled at 1.6MPa) and maintained at this temperature and pressure for 20 hours. Subsequently, the pressure was released and the temperature was lowered to room temperature. Solid-liquid separation yielded the leachate, with leaching rates of the following ions: Ni 98.6%, Co 99.2%, Mn 98.7%, and Li 99.7%.

[0046] Example 2

[0047] Compared with Example 1, the only difference is that the waste positive electrode powder and waste negative electrode powder are mixed in a 1:1 ratio to form black powder for processing together. That is, in step ④, the waste positive electrode powder is replaced with an equal amount of the black powder. The other processes are the same as in Example 1. After subcritical treatment, the pressure is released and the temperature is lowered to room temperature, followed by solid-liquid separation. The resulting liquid is the leachate, and the solid is carbon slag. The carbon slag is washed with 1M sulfuric acid until the filtrate is colorless, then washed with water and dried to obtain the regenerated carbon material.

[0048] The leaching rates of each ion in the obtained leachate were: Ni 99.1%, Co 98.7%, Mn 99.2%, and Li 99.5%. The regenerated carbon material obtained after separation and drying exhibited a filtration efficiency of 289.6 mAh g at 1C rate at room temperature (25°C). -1 The capacity.

[0049] Example 3

[0050] Compared with Example 2, the only difference is that in step ③, two-stage firing activation is used, wherein the temperature of the first stage is 600℃ and held for 3 hours; the temperature of the second stage is 800℃ and held for 3 hours. Other processes are the same as in Example 2.

[0051] The leaching rates of each ion in the obtained leachate were: Ni 99.3%, Co 99.8%, Mn 99.1%, and Li 99.3%. The regenerated carbon material obtained after separation and drying exhibited a 298.2 mAh / g ion content at room temperature and a 1C rate of 298.2 g / g. -1 The capacity.

[0052] Example 4

[0053] Compared with Example 3, the only difference is that the second-stage roasting stage is carried out with microwave assistance, wherein the microwave power is 700W, and the other processes are the same as in Example 3.

[0054] The leaching rates of each ion in the obtained leachate were: Ni 99.9%, Co 99.8%, Mn 99.5%, and Li 99.9%. The regenerated carbon material obtained after separation and drying exhibited a 314.7 mAh / g ion content at room temperature and a 1C rate of 314.7 g / g. -1 The capacity.

[0055] Example 5

[0056] Compared to Example 2, the only difference is that the electrode material was changed (the type of active material in the positive electrode powder was changed), and the experimental groups were as follows:

[0057] Group A: Positive electrode powder and negative electrode powder were obtained by stripping from waste lithium cobalt oxide batteries, and the ratio of the two in the black powder was controlled to be 2:1;

[0058] B: Positive electrode powder and negative electrode powder are obtained by stripping from waste lithium manganese oxide batteries, and the ratio of the two in the black powder is controlled to be 1:2;

[0059] Other operations and parameters are the same as in Example 2;

[0060] The test results are as follows:

[0061] Group A: The leaching rates of each ion in the obtained leachate were: Co 99.4%, Li 99.7%. The regenerated carbon material obtained after separation and drying exhibited a 288.5 mAh / g ion content at room temperature and a 1C rate of [value missing]. -1 The capacity.

[0062] Group B: The leaching rates of each ion in the obtained leachate were: Mn 98.8% and Li 99.4%. The regenerated carbon material obtained after separation and drying exhibited a 287.1 mAh / g ion content at room temperature and a 1C rate of 287.1 g / g. -1 The capacity.

[0063] Example 6

[0064] Compared with Example 2, the difference is that the ratio of electrode material (black powder) to pyrite is set to 1:1.5, while the other processes are the same as in Example 2.

[0065] The leaching rates of each ion in the obtained leachate were: Ni 99.1%, Co 99.1%, Mn 99.3%, and Li 99.2%. The regenerated carbon material obtained after separation and drying exhibited a viscosity of 279.8 mAh g at room temperature and a rate of 1C. -1 The capacity.

[0066] Example 7

[0067] Compared with Example 2, the difference is that the calcination temperature is set to 900°C, while the other processes are the same as in Example 2.

[0068] The leaching rates of each ion in the obtained leachate were: Ni 99.9%, Co 99.8%, Mn 99.7%, and Li 99.8%. The regenerated carbon material obtained after separation and drying exhibited a 291.2 mAh / g ion content at room temperature and a 1C rate of 291.2 g / g. -1 The capacity.

[0069] Example 8

[0070] Compared with Example 2, the only difference is that the subcritical conditions are changed (temperature is 220°C, pressure is controlled at 2.5 MPa), and the other processes are the same as in Example 2.

[0071] The leaching rates of each ion in the obtained leachate were: Ni 99.9%, Co 99.9%, Mn 99.9%, and Li 99.8%. The regenerated carbon material obtained after separation and drying exhibited a viscosity of 294.1 mAh g at room temperature and a rate of 1C. -1 The capacity.

[0072] Comparative Example 1:

[0073] All other conditions and steps were the same as in Example 2, except that the ball milling process in step ② was not performed. Under these conditions, the leaching rates of the metals obtained were: Ni 40.1%, Co 43.4%, Mn 51.3%, and Li 58.1%. The regenerated carbon material obtained after separation and drying exhibited a 198.4 mAh / g ion content at room temperature and a 1C rate. -1 The capacity.

[0074] Comparative Example 2:

[0075] All other conditions and steps were the same as in Example 2, except that the calcination treatment in step ③ was not performed. Under these conditions, the leaching rates of the metals obtained were: Ni 20.6%, Co 25.4%, Mn 32.4%, and Li 35.8%. The regenerated carbon material obtained after separation and drying exhibited a 173.2 mAh / g ion content at room temperature and a 1C rate. -1 The capacity.

[0076] Comparative Example 3:

[0077] All other conditions and steps were the same as in Example 2, except that the calcination temperature T1 in step ③ was set to 200°C. Under these conditions, the leaching rates of the metals obtained were: Ni 26.4%, Co 30.7%, Mn 42.3%, and Li 50.4%. The regenerated carbon material obtained after separation and drying exhibited a content of 215.8 mAh g at room temperature and a rate of 1C. -1 The capacity.

[0078] Comparative Example 4:

[0079] All other conditions and steps were the same as in Example 2, except that the temperature T2 of treatment stage ④ was set to 120°C. Under these conditions, the leaching rates of the metals obtained were: Ni 57.8%, Co 61.9%, Mn 62.7%, and Li 69.5%. The regenerated carbon material obtained after separation and drying exhibited a capacity of 230.4 mAh / g at room temperature and a rate of 1C. -1 The capacity.

[0080] Comparative Example 5:

[0081] All other conditions and steps were the same as in Example 2, except that the ratio of waste cathode powder to pyrite was set to 1:0.3. Under these conditions, the leaching rates of the metals obtained were: Ni 60.7%, Co 65.3%, Mn 75.2%, and Li 74.6%. The regenerated carbon material obtained after separation and drying exhibited a filtration efficiency of 210.5 mAh g at room temperature and a rate of 1C. -1 The capacity.

Claims

1. A method for processing waste electrode materials, characterized in that, The FeS2 source was ball-milled and then calcined and activated in a protective atmosphere at a temperature above 550°C to obtain the activated FeS2 source. Waste electrode material containing positive electrode active material and activated FeS2 source are slurried with water, heated and pressurized to a subcritical state, and then depressurized and cooled after heat preservation and pressure treatment, and solid-liquid separation is performed to obtain a leachate enriched with metal elements in the positive electrode material. The weight ratio of activated FeS2 source to waste electrode material is above 0.5; the subcritical state temperature is above 180℃ and the pressure is above 1 MPa.

2. The processing method as described in claim 1, characterized in that, In the aforementioned waste electrode materials, the positive electrode active material is an oxidized lithium salt containing at least one metal element selected from Ni, Co, and Mn.

3. The processing method as described in claim 2, characterized in that, The waste electrode material is wherein the positive electrode active material is at least one of lithium nickel oxide, lithium manganese oxide, nickel-manganese binary material, and NCM ternary material.

4. The processing method as described in claim 2, characterized in that, The waste electrode material also includes at least one of a conductive agent and a binder.

5. The processing method as described in claim 2, characterized in that, The content of the positive electrode active material in the waste electrode material is above 50 wt.%.

6. The processing method as described in claim 1, characterized in that, The waste electrode materials also include waste negative electrode materials, which are subjected to subcritical treatment and solid-liquid separation. The resulting liquid is the leachate, and the resulting solid is acid-washed, water-washed, and dried to obtain carbon materials.

7. The processing method as described in claim 1, characterized in that, The FeS2 source is at least one of analytically pure materials, minerals, and solid waste containing FeS2.

8. The processing method as described in claim 7, characterized in that, The FeS2 source contains more than 1 wt.% FeS2.

9. The processing method as described in claim 8, characterized in that, The FeS2 source contains 10 wt.% or more of FeS2.

10. The processing method as described in claim 1, characterized in that, The weight ratio of activated FeS2 source to waste electrode material is 0.5~5:

1.

11. The processing method as described in claim 1, characterized in that, The weight ratio of activated FeS2 source to waste electrode material is 1~2.5:

1.

12. The processing method as described in claim 1, characterized in that, The ball milling method can be either dry ball milling or wet ball milling.

13. The processing method as described in claim 1, characterized in that, The ball-to-material ratio during the ball milling stage is 25~50:

1.

14. The processing method as described in claim 1, characterized in that, The ball milling speed is 200~600 r / min.

15. The processing method as described in claim 1, characterized in that, The ball milling time is more than 1 hour.

16. The processing method as described in claim 1, characterized in that, The ball milling time is 5-10 hours.

17. The processing method according to any one of claims 1 to 16, characterized in that, The temperature during the roasting stage is 600~1000℃.

18. The processing method as described in claim 17, characterized in that, The roasting stage includes two heat preservation platforms, with the temperature of the first heat preservation platform being 600~700℃ and the temperature of the second heat preservation platform being 750~900℃.

19. The processing method as described in claim 18, characterized in that, The roasting stage is carried out with microwave assistance.

20. The processing method as described in claim 19, characterized in that, The power of microwaves is 500~1000W.

21. The processing method as described in claim 1, characterized in that, The roasting time is 5 to 10 hours.

22. The processing method as described in claim 1, characterized in that, The liquid-to-solid ratio during the pulping stage is 20-50 mL / g.

23. The processing method as described in claim 1, characterized in that, The filling volume of the pulped slurry in the pressure vessel required for subcritical treatment is 30~80v.

24. The processing method as described in claim 1, characterized in that, The subcritical temperature is 180~220℃; the pressure is 1~3.5 MPa.

25. The processing method as described in claim 1, characterized in that, The heat preservation and pressure holding time under subcritical conditions is 10~24h.