Efficient process for preparing lithium carbonate by roasting and leaching waste batteries under assistance of plasma

Abstract

The invention relates to an efficient process for preparing lithium carbonate by roasting and leaching waste batteries under the assistance of plasmas, and belongs to the technical field of recycling of waste batteries. The method comprises the following steps: disassembling, sorting, crushing and screening the waste lithium ion battery, adding a roasting fluxing aid, and mixing to obtain positive electrode material powder; roasting the positive electrode material powder in a plasma roasting furnace to obtain a roasted product; mixing the roasted product with a hydrochloric acid solution, leaching, and filtering to obtain a lithium-containing leachate; adding an impurity removal agent into the lithium-containing leaching solution, and filtering to obtain a purified lithium solution; adding a saturated sodium carbonate solution into the purified lithium solution, stirring to react, filtering, and drying in vacuum to obtain high-purity carbonic acid; the roasting fluxing auxiliary agent is prepared from polyethylene glycol monobutyl ether, triethoxysilane, methylbenzene, a chloroplatinic acid isopropanol solution and 4-amino-3-mercaptopyridine; the lithium leaching rate can be remarkably improved, and the prepared lithium carbonate product is high in purity and can be directly used for preparing the positive electrode material of the lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of waste battery recycling technology, and in particular to a highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles, smartphones, and energy storage devices due to their high energy density, long cycle life, and lack of memory effect. With the rapid expansion of the lithium-ion battery market, a large number of used lithium-ion batteries are generated. These used lithium-ion batteries contain valuable metal resources such as lithium, cobalt, and nickel. Lithium, as a scarce resource, is particularly important because its recycling can alleviate resource shortages and reduce environmental pollution from used batteries.

[0003] Chinese Patent CN120039916A: This invention relates to the field of lithium carbonate preparation technology, specifically to a post-processing method for preparing battery-grade lithium carbonate from waste lithium batteries. The method includes the following steps: first, the waste lithium batteries are made into lithium carbonate precursors; then, 10-15% of the total amount of the lithium carbonate precursors is added to the lithium carbonate precursors for ball milling; after ball milling, the precursors are filtered, dried, and then sintered for improvement; after sintering, battery-grade lithium carbonate is obtained.

[0004] Chinese Patent CN120483196A discloses a method for preparing lithium carbonate from recycled waste batteries, belonging to the field of waste battery recycling. It is used to solve the technical problems of low lithium leaching rate and recovery rate in lithium iron phosphate and the need to further improve the purity of recovered lithium carbonate in the prior art. The method includes the following steps: after discharging and disassembling the lithium iron phosphate battery, the positive electrode material is crushed, pretreated with N-methylpyrrolidone solution, then roasted at high temperature and acid leached, the pH is adjusted and filtered with a COF membrane, and then adsorbed with an aluminum-doped manganese ion sieve.

[0005] Existing waste battery processing technologies suffer from problems such as high energy consumption, significant lithium volatilization loss, low lithium recovery rate, and low lithium leaching rate. The purity of lithium carbonate needs to be further improved. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of spent batteries, the operation steps of which are as follows: S1 Dismantling and Screening: Dismantle and sort waste lithium-ion batteries to obtain positive electrode sheets. After crushing and screening 60-90 parts of the positive electrode sheets, dry them and add 0.5-1 parts of calcination fluxing agent to mix them to obtain positive electrode material powder. S2 Plasma-assisted calcination: The cathode material powder is placed in a plasma calcination furnace, nitrogen gas is introduced, the plasma generator is started, the calcination temperature is controlled at 450-550℃, and the calcination time is 30-60min to obtain the calcined product. S3 acid leaching: Mix the roasted product with 5-10wt% hydrochloric acid solution, stir and leach at 50-70℃ for 60-90 min, and filter to obtain lithium-containing leachate; S4 Purification and Impurity Removal: Add impurity removal agent to 60-90 parts of lithium-containing leachate, adjust the pH value to 4.5-5.5, filter to remove impurity precipitates, and obtain purified lithium solution; S5 Lithium Precipitation: Add 10-15 parts of saturated sodium carbonate solution to the purified lithium liquid, adjust the pH value to 10-11, stir the reaction, filter, and obtain lithium carbonate precipitate. S6 Drying: The lithium carbonate precipitate is vacuum dried at 120-150℃ for 3-5 hours to obtain high-purity carbonic acid.

[0007] In one specific implementation scheme, the drying temperature of S1 is 100-120℃, and the drying time is 2-4 hours.

[0008] In one specific implementation scheme, the power of the S2 plasma generator is 1-3kW, and the distance between the plasma jet and the material is 5-15mm.

[0009] In one specific feasible implementation, the liquid-to-solid ratio of the S3 hydrochloric acid solution to the calcined product is 5-10:1.

[0010] In one specific implementation, the S4 impurity remover consists of 0.05-0.3 parts calcium hydroxide, 0.05-0.2 parts sodium carbonate, and 0.03-0.12 parts sodium sulfide.

[0011] In one specific implementation, the stirring reaction temperature of S5 is 60-80℃ and the time is 30-50min.

[0012] In one specific implementation scheme, the vacuum degree of the S6 vacuum drying is -0.08 to -0.1 MPa.

[0013] In one specific feasible implementation, the method for preparing the calcining flux is as follows: Mix 70-100 parts of polyethylene glycol monobutyl ether, 8-14 parts of triethoxysilane, and 300-500 parts of toluene, add 0.4-0.9 parts of isopropanol chloroplatinic acid solution with a concentration of 10 mg / mL, and 0.2-0.5 parts of 4-amino-3-mercaptopyridine, and heat to react; after the reaction is completed, the solvent is recovered by vacuum distillation, the residue is washed three times with n-hexane, and dried under vacuum to obtain the calcination fluxing agent.

[0014] In one specific feasible implementation, the heating reaction temperature is 80-100℃ and the time is 7-11h.

[0015] In one specific implementation scheme, the vacuum drying temperature is 110-120℃ and the time is 4-6 hours.

[0016] Reaction mechanism: The high energy density of plasma and the synergistic effect of calcination fluxing agents, with the synergistic effect of amino and mercapto functional groups brought by 4-amino-3-mercaptopyridine in the additives, can reduce the calcination melting resistance, accelerate the breaking of the bonding structure between lithium and other elements in the cathode material, and at the same time inhibit the volatilization of lithium, making lithium easier to convert into an easily leached form, thus creating favorable conditions for subsequent acid leaching.

[0017] Technical effect This invention provides a highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of spent batteries. Compared with existing technologies, this invention has the following significant advantages: 1. This invention significantly reduces roasting energy consumption and shortens roasting time, which is in line with the concept of green production.

[0018] 2. This invention significantly improves the lithium leaching rate, removes impurity ions more thoroughly, and results in higher product purity.

[0019] 3. The addition of calcination fluxing agent strengthens the breaking of the bond structure between lithium and other elements, while reducing lithium volatilization loss, further optimizing the overall process efficiency. Attached Figure Description

[0020] Figure 1 This is the SEM image of Example 1. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0022] 1. Lithium leaching rate: The lithium leaching rate was detected by inductively coupled plasma atomic emission spectrometry and calculated by the formula: Lithium leaching rate (%) = (total lithium content of raw material - lithium content of leaching residue) / total lithium content of raw material × 100%.

[0023] 2. Lithium carbonate purity: The purity was determined by acid-base titration according to GB / T11075-2013 standard. Example 1

[0024] A highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries, comprising the following steps: S1 Dismantling and Screening: Dismantle and sort waste lithium-ion batteries to obtain positive electrode sheets. After crushing and screening 60g of positive electrode sheets, dry them, add 0.5g of calcination fluxing agent, and mix to obtain positive electrode material powder. S2 Plasma-assisted calcination: The cathode material powder is placed in a plasma calcination furnace, nitrogen gas is introduced, the plasma generator is started, the calcination temperature is controlled at 450℃, and the calcination time is 30 min to obtain the calcined product. S3 acid leaching: The roasted product is mixed with 5t% hydrochloric acid solution, stirred and leached at 50°C for 60 min, and filtered to obtain lithium-containing leachate; S4 Purification and Impurity Removal: Add impurity removal agent to 60g of lithium-containing leaching solution, adjust the pH value to 4.5, filter to remove impurity precipitates, and obtain purified lithium solution; S5 Lithium Precipitation: Add 10g of saturated sodium carbonate solution to the purified lithium liquid, adjust the pH value to 10, stir the reaction, filter, and obtain lithium carbonate precipitate. S6 Drying: The lithium carbonate precipitate was vacuum dried at 120℃ for 3 hours to obtain high-purity carbonic acid.

[0025] The drying temperature of S1 is 100℃ and the drying time is 2 hours.

[0026] The S2 plasma generator has a power of 1kW and a distance of 5mm between the plasma jet and the material.

[0027] The liquid-to-solid ratio of the S3 hydrochloric acid solution to the calcined product is 5:1.

[0028] The S4 impurity remover consists of 0.05g calcium hydroxide, 0.05g sodium carbonate, and 0.03g sodium sulfide.

[0029] The stirring reaction temperature of S5 is 60℃ and the time is 30min.

[0030] The vacuum degree of the S6 vacuum dryer is -0.08 MPa.

[0031] The preparation method of the calcination flux is as follows: 70g of polyethylene glycol monobutyl ether, 8g of triethoxysilane, and 300g of toluene were mixed, and 0.4g of isopropanol chloroplatinic acid solution with a concentration of 10mg / mL and 0.2g of 4-amino-3-mercaptopyridine (CAS: 52334-54-0) were added. The mixture was heated to a high temperature and reacted. After the reaction was completed, the solvent was recovered by vacuum distillation. The residue was washed three times with n-hexane and dried under vacuum to obtain the calcination fluxing agent.

[0032] The reaction temperature was 80℃ and the reaction time was 7 hours.

[0033] The vacuum drying temperature is 110℃ and the time is 4 hours. Example 2

[0034] A highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries, comprising the following steps: S1 Dismantling and Screening: Dismantle and sort waste lithium-ion batteries to obtain positive electrode sheets. After crushing and screening 70g of positive electrode sheets, dry them, add 0.6g of calcination fluxing agent, and mix to obtain positive electrode material powder. S2 Plasma-assisted calcination: The cathode material powder is placed in a plasma calcination furnace, nitrogen gas is introduced, the plasma generator is started, the calcination temperature is controlled at 480℃, and the calcination time is 40min to obtain the calcined product. S3 acid leaching: The roasted product is mixed with a 6wt% hydrochloric acid solution, stirred and leached at 55°C for 70 min, and filtered to obtain a lithium-containing leachate; S4 purification and impurity removal: Add impurity removal agent to 70g of lithium-containing leaching solution, adjust the pH value to 5, filter to remove impurity precipitate, and obtain purified lithium solution; S5 Lithium precipitation: Add 12g of saturated sodium carbonate solution to the purified lithium liquid, adjust the pH value to 10, stir the reaction, filter, and obtain lithium carbonate precipitate. S6 Drying: The lithium carbonate precipitate was vacuum dried at 130℃ for 4 hours to obtain high-purity carbonic acid.

[0035] The drying temperature of S1 is 105℃ and the drying time is 3h.

[0036] The S2 plasma generator has a power of 2kW and a distance of 8mm between the plasma jet and the material.

[0037] The liquid-to-solid ratio of the S3 hydrochloric acid solution to the calcined product is 6:1.

[0038] The S4 impurity remover consists of 0.1g calcium hydroxide, 0.1g sodium carbonate, and 0.06g sodium sulfide.

[0039] The stirring reaction temperature of S5 is 65℃ and the time is 35min.

[0040] The vacuum degree of the S6 vacuum dryer is -0.09 MPa.

[0041] The preparation method of the calcination flux is as follows: 80g of polyethylene glycol monobutyl ether, 10g of triethoxysilane, and 350g of toluene were mixed, and 0.5g of isopropanol chloroplatinic acid solution with a concentration of 10mg / mL and 0.3g of 4-amino-3-mercaptopyridine (CAS: 52334-54-0) were added. The mixture was heated to a high temperature and reacted. After the reaction was completed, the solvent was recovered by vacuum distillation. The residue was washed three times with n-hexane and dried under vacuum to obtain the calcination fluxing agent.

[0042] The reaction temperature was 85℃ and the reaction time was 8 hours.

[0043] The vacuum drying temperature is 115℃ and the time is 5 hours. Example 3

[0044] A highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries, comprising the following steps: S1 Dismantling and Screening: Dismantle and sort waste lithium-ion batteries to obtain positive electrode sheets. After crushing and screening 80g of positive electrode sheets, dry them, add 0.8g of calcination fluxing agent, and mix to obtain positive electrode material powder. S2 Plasma-assisted calcination: The cathode material powder is placed in a plasma calcination furnace, nitrogen gas is introduced, the plasma generator is started, the calcination temperature is controlled at 530℃, and the calcination time is 50min to obtain the calcined product. S3 acid leaching: The roasted product is mixed with 8wt% hydrochloric acid solution, stirred and leached at 65℃ for 80 min, and filtered to obtain lithium-containing leachate; S4 purification and impurity removal: Add impurity removal agent to 80g of lithium-containing leaching solution, adjust the pH value to 5, filter to remove impurity precipitate, and obtain purified lithium solution; S5 Lithium precipitation: Add 14g of saturated sodium carbonate solution to the purified lithium liquid, adjust the pH value to 11, stir the reaction, filter, and obtain lithium carbonate precipitate. S6 Drying: The lithium carbonate precipitate was vacuum dried at 140℃ for 4 hours to obtain high-purity carbonic acid.

[0045] The drying temperature of S1 is 115℃ and the drying time is 3h.

[0046] The S2 plasma generator has a power of 2kW and a distance of 13mm between the plasma jet and the material.

[0047] The liquid-to-solid ratio of the S3 hydrochloric acid solution to the calcined product is 8:1.

[0048] The S4 impurity remover consists of 0.2g calcium hydroxide, 0.15g sodium carbonate, and 0.09g sodium sulfide.

[0049] The stirring reaction temperature of S5 is 75℃ and the time is 45min.

[0050] The vacuum degree of the S6 vacuum dryer is -0.09 MPa.

[0051] The preparation method of the calcination flux is as follows: 90g of polyethylene glycol monobutyl ether, 12g of triethoxysilane, and 450g of toluene were mixed, and 0.8g of isopropanol chloroplatinic acid solution with a concentration of 10mg / mL and 0.4g of 4-amino-3-mercaptopyridine (CAS: 52334-54-0) were added. The mixture was heated to a high temperature and reacted. After the reaction was completed, the solvent was recovered by vacuum distillation. The residue was washed three times with n-hexane and dried under vacuum to obtain the calcination fluxing agent.

[0052] The reaction temperature was 95℃ and the reaction time was 10 hours.

[0053] The vacuum drying temperature is 115℃ and the time is 5 hours. Example 4

[0054] A highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries, comprising the following steps: S1 Dismantling and Screening: Dismantle and sort waste lithium-ion batteries to obtain positive electrode sheets. After crushing and screening 90g of positive electrode sheets, dry them, add 1g of calcination fluxing agent, and mix to obtain positive electrode material powder. S2 Plasma-assisted calcination: The cathode material powder is placed in a plasma calcination furnace, nitrogen gas is introduced, the plasma generator is started, the calcination temperature is controlled at 550℃, and the calcination time is 60min to obtain the calcined product. S3 acid leaching: The roasted product is mixed with a 10wt% hydrochloric acid solution, stirred and leached at 70℃ for 90 min, and filtered to obtain a lithium-containing leachate; S4 Purification and Impurity Removal: Add impurity removal agent to 90g of lithium-containing leaching solution, adjust the pH value to 5.5, filter to remove impurity precipitates, and obtain purified lithium solution; S5 Lithium Precipitation: Add 15g of saturated sodium carbonate solution to the purified lithium liquid, adjust the pH value to 11, stir the reaction, filter, and obtain lithium carbonate precipitate. S6 Drying: The lithium carbonate precipitate was vacuum dried at 150℃ for 5 hours to obtain high-purity carbonic acid.

[0055] The drying temperature of S1 is 120℃ and the drying time is 4h.

[0056] The S2 plasma generator has a power of 3kW and a distance of 15mm between the plasma jet and the material.

[0057] The liquid-to-solid ratio of the S3 hydrochloric acid solution to the calcined product is 10:1.

[0058] The S4 impurity remover consists of 0.3g calcium hydroxide, 0.2g sodium carbonate, and 0.12g sodium sulfide.

[0059] The stirring reaction temperature of S5 is 80℃ and the time is 50min.

[0060] The vacuum degree of the S6 vacuum dryer is -0.1 MPa.

[0061] The preparation method of the calcination flux is as follows: 100g of polyethylene glycol monobutyl ether, 14g of triethoxysilane, and 500g of toluene were mixed, and 0.9g of isopropanol chloroplatinic acid solution with a concentration of 10mg / mL and 0.5g of 4-amino-3-mercaptopyridine (CAS: 52334-54-0) were added. The mixture was heated to a high temperature and reacted. After the reaction was completed, the solvent was recovered by vacuum distillation. The residue was washed three times with n-hexane and dried under vacuum to obtain the calcination fluxing agent.

[0062] The reaction temperature was 100℃ and the reaction time was 11 hours.

[0063] The vacuum drying temperature is 120℃ and the time is 6 hours.

[0064] Comparative Example 1 A highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries, comprising the following steps: S1 Dismantling and Screening: Dismantle and sort waste lithium-ion batteries to obtain positive electrode sheets. After crushing, screening and drying 60g of positive electrode sheets, positive electrode material powder is obtained. S2 Plasma-assisted calcination: The cathode material powder is placed in a plasma calcination furnace, nitrogen gas is introduced, the plasma generator is started, the calcination temperature is controlled at 450℃, and the calcination time is 30 min to obtain the calcined product. S3 acid leaching: The roasted product is mixed with 5t% hydrochloric acid solution, stirred and leached at 50°C for 60 min, and filtered to obtain lithium-containing leachate; S4 Purification and Impurity Removal: Add impurity removal agent to 60g of lithium-containing leaching solution, adjust the pH value to 4.5, filter to remove impurity precipitates, and obtain purified lithium solution; S5 Lithium Precipitation: Add 10g of saturated sodium carbonate solution to the purified lithium liquid, adjust the pH value to 10, stir the reaction, filter, and obtain lithium carbonate precipitate. S6 Drying: The lithium carbonate precipitate was vacuum dried at 120℃ for 3 hours to obtain high-purity carbonic acid.

[0065] The drying temperature of S1 is 100℃ and the drying time is 2 hours.

[0066] The S2 plasma generator has a power of 1kW and a distance of 5mm between the plasma jet and the material.

[0067] The liquid-to-solid ratio of the S3 hydrochloric acid solution to the calcined product is 5:1.

[0068] The S4 impurity remover consists of 0.05g calcium hydroxide, 0.05g sodium carbonate, and 0.03g sodium sulfide.

[0069] The stirring reaction temperature of S5 is 60℃ and the time is 30min.

[0070] The vacuum degree of the S6 vacuum dryer is -0.08 MPa.

[0071] Comparative Example 2 A highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries, comprising the following steps: S1 Dismantling and Screening: Dismantle and sort waste lithium-ion batteries to obtain positive electrode sheets. After crushing and screening 60g of positive electrode sheets, dry them, add 0.5g of calcination fluxing agent, and mix to obtain positive electrode material powder. S2 Plasma-assisted calcination: The cathode material powder is placed in a plasma calcination furnace, nitrogen gas is introduced, the plasma generator is started, the calcination temperature is controlled at 450℃, and the calcination time is 30 min to obtain the calcined product. S3 acid leaching: The roasted product is mixed with 5t% hydrochloric acid solution, stirred and leached at 50°C for 60 min, and filtered to obtain lithium-containing leachate; S4 Purification and Impurity Removal: Add impurity removal agent to 60g of lithium-containing leaching solution, adjust the pH value to 4.5, filter to remove impurity precipitates, and obtain purified lithium solution; S5 Lithium Precipitation: Add 10g of saturated sodium carbonate solution to the purified lithium liquid, adjust the pH value to 10, stir the reaction, filter, and obtain lithium carbonate precipitate. S6 Drying: The lithium carbonate precipitate was vacuum dried at 120℃ for 3 hours to obtain high-purity carbonic acid.

[0072] The drying temperature of S1 is 100℃ and the drying time is 2 hours.

[0073] The S2 plasma generator has a power of 1kW and a distance of 5mm between the plasma jet and the material.

[0074] The liquid-to-solid ratio of the S3 hydrochloric acid solution to the calcined product is 5:1.

[0075] The S4 impurity remover consists of 0.05g calcium hydroxide, 0.05g sodium carbonate, and 0.03g sodium sulfide.

[0076] The stirring reaction temperature of S5 is 60℃ and the time is 30min.

[0077] The vacuum degree of the S6 vacuum dryer is -0.08 MPa.

[0078] The preparation method of the calcination flux is as follows: 70g of polyethylene glycol monobutyl ether, 8g of triethoxysilane, and 300g of toluene were mixed and 0.4g of isopropanol chloroplatinic acid solution with a concentration of 10mg / mL was added. The mixture was heated to react. After the reaction was completed, the solvent was recovered by vacuum distillation. The residue was washed three times with n-hexane and dried under vacuum to obtain the calcination fluxing agent.

[0079] The reaction temperature was 80℃ and the reaction time was 7 hours.

[0080] The vacuum drying temperature is 110℃ and the time is 4 hours.

[0081] Comparative Example 3 A highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries, comprising the following steps: S1 Dismantling and Screening: Dismantle and sort waste lithium-ion batteries to obtain positive electrode sheets. After crushing and screening 60g of positive electrode sheets, dry them, add 0.5g of calcination fluxing agent, and mix to obtain positive electrode material powder. S2 Plasma-assisted calcination: The cathode material powder is placed in a plasma calcination furnace, nitrogen gas is introduced, the plasma generator is started, the calcination temperature is controlled at 450℃, and the calcination time is 30 min to obtain the calcined product. S3 acid leaching: The roasted product is mixed with 5t% hydrochloric acid solution, stirred and leached at 50°C for 60 min, and filtered to obtain lithium-containing leachate; S4 Purification and Impurity Removal: Add impurity removal agent to 60g of lithium-containing leaching solution, adjust the pH value to 4.5, filter to remove impurity precipitates, and obtain purified lithium solution; S5 Lithium Precipitation: Add 10g of saturated sodium carbonate solution to the purified lithium liquid, adjust the pH value to 10, stir the reaction, filter, and obtain lithium carbonate precipitate. S6 Drying: The lithium carbonate precipitate was vacuum dried at 120℃ for 3 hours to obtain high-purity carbonic acid.

[0082] The drying temperature of S1 is 100℃ and the drying time is 2 hours.

[0083] The S2 plasma generator has a power of 1kW and a distance of 5mm between the plasma jet and the material.

[0084] The liquid-to-solid ratio of the S3 hydrochloric acid solution to the calcined product is 5:1.

[0085] The S4 impurity remover consists of 0.05g calcium hydroxide, 0.05g sodium carbonate, and 0.03g sodium sulfide.

[0086] The stirring reaction temperature of S5 is 60℃ and the time is 30min.

[0087] The vacuum degree of the S6 vacuum dryer is -0.08 MPa.

[0088] The preparation method of the calcination flux is as follows: 70g of polyethylene glycol monobutyl ether and 300g of toluene were mixed, and 0.4g of isopropanol chloroplatinic acid solution with a concentration of 10mg / mL and 0.2g of 4-amino-3-mercaptopyridine (CAS: 52334-54-0) were added. The mixture was heated to a high temperature and reacted. After the reaction was completed, the solvent was recovered by vacuum distillation. The residue was washed three times with n-hexane and dried under vacuum to obtain the calcination flux.

[0089] The reaction temperature was 80℃ and the reaction time was 7 hours.

[0090] The vacuum drying temperature is 110℃ and the time is 4 hours.

[0091] Table 1. Results of lithium leaching rate and lithium carbonate purity testing in the specific implementation plan. Lithium leaching rate (%) Lithium carbonate purity (%) Example 1 99.64 99.78 Example 2 99.67 99.82 Example 3 99.72 99.88 Example 4 99.75 99.91 Comparative Example 1 78.56 88.12 Comparative Example 2 94.73 95.59 Comparative Example 3 95.31 96.26 Results Analysis Based on the above Examples 1-4, Comparative Examples 1-3, and the corresponding lithium leaching rate and lithium carbonate purity test results (testing methods: lithium leaching rate was calculated using inductively coupled plasma atomic emission spectrometry according to the formula "lithium leaching rate (%) = (total lithium content in raw materials - lithium content in leaching residue) / total lithium content in raw materials × 100%"; lithium carbonate purity was tested using acid-base titration according to GB / T11075-2013 standard), the following conclusions can be drawn: The lithium leaching rates of Examples 1-4 all reached 99.64%-99.75%, and the lithium carbonate purity was 99.78%-99.91%, which were significantly better than the test results of Comparative Examples 1-3. This shows that the "plasma-assisted + special roasting fluxing agent" process proposed in this invention can effectively solve the technical problems of "high energy consumption, large lithium volatilization loss, low leaching rate and insufficient purity" in the existing process of preparing lithium carbonate from recycled waste batteries.

[0092] 1. Comparative Analysis of Example 1 and Comparative Example 1 The key difference between Comparative Example 1 and Example 1 is that no calcination flux was added; all other process parameters were identical. Test results showed that the lithium leaching rate of Comparative Example 1 was only 78.56%, and the lithium carbonate purity was 88.12%, far lower than the 99.64% and 99.78% of Example 1, respectively.

[0093] The main reasons for the difference are as follows: Comparative Example 1 relies solely on the high-energy characteristics of plasma to act on the cathode material, lacking the synergistic effect of calcination fluxing agents. Without the synergistic effect of amino and mercapto groups in the fluxing agents, the bonding structure between lithium and other elements in the cathode material is difficult to break efficiently, resulting in a significant increase in lithium volatilization loss during calcination and insufficient lithium leaching in the subsequent acid leaching stage. At the same time, in the calcination system not regulated by fluxing agents, impurity ions are difficult to effectively separate from lithium, ultimately leading to a significant decrease in the purity of lithium carbonate.

[0094] 2. Comparative Analysis of Example 1 and Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that 4-amino-3-mercaptopyridine was not added in the preparation of the calcination flux, while the other conditions remained the same. The test results showed that the lithium leaching rate of Comparative Example 2 was 94.73%, and the lithium carbonate purity was 95.59%, which was better than Comparative Example 1, but still significantly lower than Example 1.

[0095] The difference lies in the fact that 4-amino-3-mercaptopyridine is the core source of the "synergistic functional group of amino and mercapto groups" in the additive. The additive in Comparative Example 2 lacks this component and relies solely on the basic interaction of polyethylene glycol monobutyl ether and triethoxysilane, which cannot effectively reduce the calcination melting resistance or suppress lithium volatilization loss. Therefore, the lithium release efficiency and separation effect in the cathode material are both affected, resulting in lithium leaching rate and product purity failing to reach the level of Example 1.

[0096] 3. Comparative Analysis of Example 1 and Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that triethoxysilane was not added in the preparation of the calcination flux, while the other conditions were the same. The test results showed that the lithium leaching rate of Comparative Example 3 was 95.31%, and the lithium carbonate purity was 96.26%, which were lower than the test results of Example 1.

[0097] The main reason for the difference is that triethoxysilane, as a silicon-containing reagent, forms a stable modified structure with polyethylene glycol monobutyl ether through a hydrosilylation reaction during the preparation of the additive, ensuring the dispersibility and continuous effect of the additive in the calcination system. In Comparative Example 3, the additive lacks triethoxysilane, resulting in an insufficient modification reaction. The additive is difficult to distribute uniformly in the cathode material powder, limiting its synergistic effect with plasma and failing to fully accelerate lithium bond breaking and inhibit lithium volatilization. Consequently, the lithium leaching rate and lithium carbonate purity are lower than in Example 1.

[0098] 4. Advantages of Examples 3-4 The lithium leaching rate (99.72%~99.75%) and lithium carbonate purity (99.88%~99.91%) in Examples 3-4 were the best among all examples, which is closely related to the optimization of process parameters and the full utilization of the additives. Examples 3-4 optimized parameters such as the amount of positive electrode, calcination temperature, acid leaching concentration, and liquid-solid ratio to achieve a precise match between plasma energy and the effect of additives. Under optimal preparation conditions, the calcined fluxing agent achieves the best synergistic effect between amino and mercapto groups and the optimal dispersibility after hydrosilylation modification. This minimizes melting resistance, inhibits lithium volatilization, and promotes efficient separation of impurity ions from lithium, ultimately achieving a dual improvement in lithium leaching rate and product purity. This is the optimal implementation scheme of the present invention.

[0099] In summary, the core innovative value of this invention lies in the synergistic effect of the high energy density characteristics of plasma and the specialized calcination flux: the flux is modified by hydrosilylation of polyethylene glycol monobutyl ether, triethoxysilane, and 4-amino-3-mercaptopyridine to form synergistic functional groups containing amino and mercapto groups. This not only reduces calcination melting resistance and accelerates lithium bond breaking but also inhibits lithium volatilization loss. Combined with the high-efficiency energy input of plasma, the lithium leaching rate is significantly improved. After subsequent purification, impurity removal, and lithium precipitation steps, high-purity lithium carbonate is finally obtained. This process effectively overcomes the shortcomings of existing technologies and provides a green and efficient solution for the efficient recycling of lithium resources from waste lithium-ion batteries. The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A highly efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries, the operation steps of which are as follows, in parts by mass: S1 Dismantling and Screening: Dismantle and sort waste lithium-ion batteries to obtain positive electrode sheets. After crushing and screening 60-90 parts of the positive electrode sheets, dry them and add 0.5-1 parts of calcination fluxing agent to mix them to obtain positive electrode material powder. S2 Plasma-assisted calcination: The cathode material powder is placed in a plasma calcination furnace, nitrogen gas is introduced, the plasma generator is started, the calcination temperature is controlled at 450-550℃, and the calcination time is 30-60min to obtain the calcined product. S3 acid leaching: Mix the roasted product with 5-10wt% hydrochloric acid solution, stir and leach at 50-70℃ for 60-90 min, and filter to obtain lithium-containing leachate; S4 Purification and Impurity Removal: Add impurity removal agent to 60-90 parts of lithium-containing leachate, adjust the pH value to 4.5-5.5, filter to remove impurity precipitates, and obtain purified lithium solution; S5 Lithium Precipitation: Add 10-15 parts of saturated sodium carbonate solution to the purified lithium liquid, adjust the pH value to 10-11, stir the reaction, filter, and obtain lithium carbonate precipitate. S6 Drying: The lithium carbonate precipitate is vacuum dried at 120-150℃ for 3-5 hours to obtain high-purity carbonic acid; The calcination fluxing agent is prepared by reacting polyethylene glycol monobutyl ether, triethoxysilane, isopropanol chloroplatinate solution, and 4-amino-3-mercaptopyridine.

2. The efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries according to claim 1, characterized in that: The drying temperature of S1 is 100-120℃, and the drying time is 2-4 hours.

3. The efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries according to claim 1, characterized in that: The S2 plasma generator has a power of 1-3kW and a distance of 5-15mm between the plasma jet and the material.

4. The efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries according to claim 1, characterized in that: The liquid-to-solid ratio of the S3 hydrochloric acid solution to the calcined product is 5-10:

1.

5. The efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries according to claim 1, characterized in that: The S4 impurity remover is composed of 0.05-0.3 parts calcium hydroxide, 0.05-0.2 parts sodium carbonate, and 0.03-0.12 parts sodium sulfide.

6. The efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries according to claim 1, characterized in that: The stirring reaction temperature of S5 is 60-80℃, and the time is 30-50 min.

7. The efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries according to claim 1, characterized in that: The vacuum degree of the S6 vacuum dryer is -0.08 to -0.1 MPa.

8. The efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries according to claim 1, characterized in that: The preparation method of the calcination flux is as follows: Mix 70-100 parts of polyethylene glycol monobutyl ether, 8-14 parts of triethoxysilane, and 300-500 parts of toluene, add 0.4-0.9 parts of isopropanol chloroplatinic acid solution with a concentration of 10 mg / mL, and 0.2-0.5 parts of 4-amino-3-mercaptopyridine, and heat to react; after the reaction is completed, the solvent is recovered by vacuum distillation, the residue is washed three times with n-hexane, and dried under vacuum to obtain the calcination fluxing agent.

9. The efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries according to claim 8, characterized in that: The heating reaction temperature is 80-100℃, and the time is 7-11 hours.

10. The efficient process for preparing lithium carbonate by plasma-assisted roasting and leaching of waste batteries according to claim 8, characterized in that: The vacuum drying temperature is 110-120℃, and the time is 4-6 hours.

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