Method for recycling high value lithium cobalt oxide cathode material

Abstract

This invention relates to the field of waste lithium battery recycling technology, specifically disclosing a method for high-value recycling of lithium cobalt oxide battery cathode materials. The method includes the following steps: adding oxalic acid, hydrogen peroxide, and nano-zirconia to the fully discharged and de-aluminum-foil-removed lithium cobalt oxide cathode material, and grinding it in a zirconia ball mill; after grinding, leaching and filtration to separate cobalt oxalate residue and lithium-containing filtrate; adding potassium fluoride to the filtrate to convert it into lithium fluoride, and then regenerating the oxalic acid using Amberlyst-15 ion exchange resin for recycling. This method achieves efficient separation, high-purity recovery, and is economical and environmentally friendly through the synergistic effect of mechanical and chemical action and reagent regeneration technology, providing a feasible path for the high-value recycling of lithium cobalt oxide battery cathode materials.

Description

Technical Field

[0001] This invention relates to the field of waste lithium battery recycling technology, and in particular to a method for recycling high-value lithium cobalt oxide battery cathode materials. Background Technology

[0002] LCO batteries, as the earliest commercially available lithium-ion batteries, are widely used in consumer electronics devices such as smartphones, laptops, and tablets. With the increasing prevalence and rapid replacement of these devices, the amount of discarded lithium cobalt oxide batteries is also increasing year by year. Retired lithium cobalt oxide batteries contain high-value metals such as cobalt and lithium, indicating a huge market potential for their recycling.

[0003] If these retired LCO batteries can be effectively recycled, it will not only reduce potential environmental hazards but also enable the resource reuse of valuable metals such as cobalt and lithium, resulting in significant economic and environmental benefits. However, due to the complex chemical structure of LCO cathode materials, their recycling process faces many technical challenges. How to efficiently and environmentally recycle the valuable metals in retired LCO cathode materials and transform them into high-value-added products is a key issue that urgently needs to be addressed.

[0004] Currently, the most common method for recycling decommissioned LCO cathode materials is hydrometallurgy. HCl, HNO3, and H2SO4 have all been shown to dissolve Li and Co in decommissioned LCO cathode materials into solution, but subsequent separation of Li and Co often requires additional steps. Studies have shown that Co... 3+ Co dominates in cathode materials, but at room temperature, 2+ Compared to Co 3+ It dissolves more readily in the aqueous phase. In the absence of a reducing agent, the leaching efficiency of Co in HCl is higher than that in HNO3 and H2SO4 because HCl has a relatively higher reducing power. Common reducing agents include H2O2, Na2S2O3, and NaHSO3. For example, in the H2SO4-H2O2 system, Co is successfully leached, and from Co… 3+ Converted to Co 2+ In recent years, organic acids such as malic acid, formic acid, tartaric acid, citric acid, and salicylic acid have also been used for leaching valuable metal elements from decommissioned LCO cathode materials. However, traditional wet recycling processes generate large amounts of saline wastewater after the reaction. If this wastewater is discharged directly without proper treatment, it will cause serious pollution to water bodies and soil. In addition to wastewater pollution, traditional wet processes also produce some harmful gases, such as acid mist released during the acid leaching process, which pollutes the air.

[0005] Regarding the aforementioned technologies, the inventors believe that it is necessary to develop a recycling method that can achieve near-full recovery of retired LCO cathode materials and high-value recycling of the products. Summary of the Invention

[0006] To address the technical shortcomings of existing technologies, this application provides a method for high-value recycling of lithium cobalt oxide battery cathode materials.

[0007] In a first aspect, this application provides a method for high-value recycling of lithium cobalt oxide battery cathode materials, employing the following technical solution: A method for high-value recycling of lithium cobalt oxide battery cathode materials includes the following specific steps: S1: Place the lithium cobalt oxide cathode material into a ball mill, add oxalic acid and hydrogen peroxide for grinding, control the ball-to-material ratio to be (30-70):1, the ball mill speed to be 200-700 rpm, and the grinding time to be 90-150 min; wherein, the mass ratio of oxalic acid to lithium cobalt oxide cathode material is (1.5-3):1, and the volume mass ratio of hydrogen peroxide to lithium cobalt oxide cathode material is (15-30):1 mL / g; S2: After grinding, wash the mixture out of the ball mill jar with deionized water, and then perform leaching treatment, controlling the leaching temperature at 20-70℃ and the leaching time at 10-120 min; S3: After leaching, filter to obtain filter residue and filtrate; The filter residue was washed, dried and ground and then used for characterization experiments; the filtrate was shaken and then brought to a final volume to determine the oxalicization efficiency of cobalt and lithium. S4: Add potassium fluoride, a lithium precipitant, to the filtrate obtained in step S3 to convert lithium oxalate to lithium fluoride. The filtered residue is washed, dried, and ground to obtain lithium fluoride, which is then used for characterization experiments. S5: Use acidic ion exchange resin to exchange potassium ions in the lithium fluoride conversion residue to regenerate oxalic acid.

[0008] By employing the above-mentioned scheme, the synergistic effect of oxalic acid and hydrogen peroxide, combined with precise control of ball milling and leaching processes, achieved efficient separation of lithium and cobalt. Oxalic acid, acting as a complexing agent and acid source, can break the Li-O and Co-O bonds in lithium cobalt oxide, providing a chemical environment for ion release; hydrogen peroxide, acting as a reducing agent, breaks the Co... 3+ Restored to Co 2+ Inhibits [Co(C2O4)3] 3- The formation of soluble complexes causes Co to precipitate as CoC₂O₄·2H₂O in the filter residue. Simultaneously, optimized parameters such as the ball-to-powder ratio and rotation speed enhance the transmission of mechanical force, accelerate lattice breakage, and synergize with chemical reactions. This ensures complete lithium recovery while significantly reducing cobalt leaching and lowering subsequent separation costs. Furthermore, KF, acting as a lithium precipitant, efficiently separates Li from the leachate, while the acidic ion exchange resin recovers oxalic acid, greatly improving economic efficiency.

[0009] Preferably, the steps include: S1: Place the lithium cobalt oxide cathode material into a ball mill, add oxalic acid and hydrogen peroxide for grinding, control the ball-to-material ratio at 50:1, the ball mill speed at 300 rpm, and the grinding time at 120 min; wherein, the mass ratio of oxalic acid to lithium cobalt oxide cathode material is 2:1, and the volume mass ratio of hydrogen peroxide to lithium cobalt oxide cathode material is 20:1 mL / g; S2: After grinding, the mixture is washed out of the ball mill jar with deionized water, and then leaching is performed. The leaching temperature is controlled at 50℃ and the leaching time is 50 min. S3: After leaching, filter to obtain filter residue and filtrate; The filter residue was washed, dried and ground and then used for characterization experiments; the filtrate was shaken and then brought to a final volume to determine the oxalicization efficiency of cobalt and lithium. S4: Add potassium fluoride, a lithium precipitant, to the filtrate obtained in step S3 to convert lithium oxalate to lithium fluoride. The filtered residue is washed, dried, and ground to obtain lithium fluoride, which is then used for characterization experiments. S5: Use acidic ion exchange resin to exchange potassium ions in the lithium fluoride conversion residue to regenerate oxalic acid.

[0010] By adopting the above scheme, the separation of lithium and cobalt can be further improved, the cobalt in the leachate can be reduced, thereby improving the conversion rate of Li and the purity of the precipitate during the lithium precipitation recovery process, and increasing economic benefits.

[0011] Preferably, the lithium cobalt oxide cathode material in step S1 is obtained by sequentially fully discharging and removing the aluminum foil from a waste lithium cobalt oxide battery.

[0012] By adopting the above scheme, complete discharge avoids the safety hazards of residual battery power, and removing aluminum foil reduces the interference of impurities on the subsequent leaching reaction, ensuring the purity of the lithium cobalt oxide cathode material and laying the foundation for efficient leaching.

[0013] Preferably, the lithium cobalt oxide cathode material in step S1 is subjected to low-temperature plasma pretreatment before being added to the ball mill. The low-temperature plasma pretreatment involves placing the lithium cobalt oxide cathode material in a low-temperature plasma surface treatment instrument for pretreatment. The plasma is an Ar / H2 mixed gas (volume ratio 9:1), with a power of 100-150 W and a treatment time of 5-10 min.

[0014] By adopting the above scheme, low-temperature plasma pretreatment promotes the breaking of lithium-oxygen bonds by creating surface defects, while reducing surface cobalt ions and reducing complex formation. Compared with no pretreatment, the cobalt leaching efficiency is further reduced, thus improving the lithium-cobalt separation efficiency.

[0015] Preferably, the ball mill is a zirconia ball mill.

[0016] By adopting the above scheme, the zirconia ball mill has high chemical stability, does not react with the reagents, avoids the introduction of impurities, and the high hardness of the zirconia balls can effectively transmit mechanical force. Combined with the optimized ball-to-material ratio, it ensures the full breakage of the lithium cobalt oxide lattice and improves the lithium leaching efficiency.

[0017] Preferably, nano-zirconia is added before grinding in step S2, and the mass ratio of nano-zirconia to lithium cobalt oxide cathode material is 1:10, with a particle size of 20-50 nm.

[0018] By adopting the above scheme, nano-zirconia can uniformly transmit mechanical force, avoid local over-grinding, and its surface hydroxyl groups can competitively bind oxalate, reducing the formation of soluble complexes between cobalt and oxalate, and further improving the separation selectivity of lithium and cobalt.

[0019] Preferably, the acidic defluorination resin is Amberlyst-15 type ion exchange resin.

[0020] By adopting the above scheme, Amberlyst-15 ion exchange resin can selectively exchange potassium ions in the residual liquid. Combined with potassium fluoride precipitation of lithium, it achieves efficient lithium recovery. The generated lithium fluoride has high purity and can also regenerate oxalic acid. Nearly half of the oxalic acid can be recycled, reducing raw material consumption.

[0021] Preferably, the resin needs to be packed into a column and pretreated before use.

[0022] By adopting the above scheme, the resin packing ensures uniform resin distribution and avoids channeling. The pretreatment removes impurities and activates sulfonic acid groups, ensuring the resin's exchange capacity with potassium ions and providing a guarantee for the efficient regeneration of oxalic acid.

[0023] Preferably, the pretreatment involves treating the resin with a sulfuric acid solution in a forward column feed manner.

[0024] By adopting the above scheme, the sulfuric acid forward treatment completely converts the resin into the H form, enhances the exchange efficiency of hydrogen ions and potassium ions, ensures that potassium ions in the residual liquid are fully adsorbed, and improves the regeneration rate of oxalic acid.

[0025] Secondly, this invention application protects the application of the above-mentioned method for recycling high-value lithium cobalt oxide battery cathode materials in the recycling of lithium cobalt oxide battery cathode materials.

[0026] In summary, this application has the following beneficial effects: 1. This invention achieves efficient separation and high-purity recovery of lithium and cobalt. The solution utilizes a synergistic process of "pretreatment-mechanical oxalic acid treatment-leaching-lithium precipitation-oxalic acid regeneration," with the core being the use of the mechanical force of ball milling and the chemical reaction between oxalic acid and hydrogen peroxide to break the Li-O / Co-O bonds in LCO and reduce Co. 3+ Cheng Co 2+ Meanwhile, low-temperature plasma pretreatment and nano-zirconia grinding aid can increase Li active sites and prevent Co from accumulating in the early stage of ball milling. 3+ The formation of a complex with oxalate ions not only facilitates more uniform ball milling but also works synergistically with mechanical oxalation to efficiently separate Li and Co from LCO. The lithium precipitation and oxalate regeneration steps are specifically designed for the aforementioned steps. Based on the leachate obtained from these steps, lithium is converted to the maximum extent possible while maintaining purity. Furthermore, oxalate regeneration reduces costs and improves economic efficiency. In summary, this invention, based on the novel mechanism of mechanical oxalation, utilizes a synergistic process involving pretreatment, nano-zirconia grinding aids, lithium precipitation, and oxalate regeneration to completely leach Li. 99.23% of the Li is converted into high-value LiF precipitate with a purity of 99.71%. Moreover, the vast majority of Co is converted into cobalt oxalate precipitate, with only 0.97% of Co remaining in the leachate. In addition, by using Amberlyst-15 strong acid cation exchange resin for treatment, every 0.1g of decommissioned LCO cathode material recovered can regenerate 127.12mg of H2C2O4·2H2O, and nearly half of the oxalic acid can be regenerated and reused in the mechanical oxalization stage. Thus, near-full recovery of decommissioned LCO cathode material and high-value utilization of the products are achieved.

[0027] 2. This invention combines economic efficiency with environmental friendliness. By optimizing process parameters to reduce energy consumption, and using Amberlyst-15 resin to regenerate oxalic acid, the consumption of chemical reagents is reduced. Low-pollution reagents such as oxalic acid and hydrogen peroxide are used throughout the process, avoiding corrosion and waste liquid treatment problems caused by strong acids such as hydrochloric acid. Furthermore, the discharge and aluminum foil removal steps in the pretreatment stage improve the stability of raw materials and reduce the risk of subsequent process fluctuations, providing an efficient, low-cost, and environmentally friendly end-to-end solution for large-scale recycling. Attached Figure Description

[0028] Figure 1 This is a schematic diagram showing the leaching efficiency results of Li and Co in Examples 1-4 and Experiments 1-5.

[0029] Figure 2 This is a schematic diagram showing the leaching efficiency results of Li and Co in Examples 5-6 and Experimental Examples 6-7.

[0030] Figure 3 This is a schematic diagram showing the leaching efficiency results of Li and Co in Experiment Example 8.

[0031] Figure 4 This is a schematic diagram showing the absorbance measurement results of the leachate under different ball milling times.

[0032] Figure 5 FT-IR spectra of retired LCO samples and samples before and after mechanical oxalic acidification in each reaction system of Experiment 8.

[0033] Figure 6 XPS spectra of H2O2-H2C2O4 before and after mechanical oxalic acidification.

[0034] Figure 7 XRD patterns of LiF and regenerated H2C2O4·2H2O.

[0035] Figure 8 A schematic diagram of the mechanical oxalization mechanism of retired LCO cathode materials. Detailed Implementation

[0036] The present application will be further described in detail below with reference to the embodiments.

[0037] Experimental materials 1. Chemical reagents Hydrogen peroxide (H2O2) was purchased from Guangdong Guangshi Reagent Technology Co., Ltd. Oxalic acid (H2C2O4), purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Potassium fluoride (KF), purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Sulfuric acid (H2SO4), purchased from Guangdong Guangshi Reagent Technology Co., Ltd. Amberlyst-15 resin was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Nano-zirconia was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0038] 2. Instruments and equipment Planetary ball mill, model F-P400, purchased from Hunan Fukas Experimental Instrument Co., Ltd. Inductively coupled plasma optical emission spectrometer (ICP-OES, Perkin Elmer Avio 550 Max, USA); Low-temperature plasma surface treatment instrument, purchased from Beijing Taifengrui Technology Co., Ltd., model TFR02-PL-3500; X-ray diffractometer (XRD, Malvern Panalytical Empyrean, Netherlands); Fourier transform infrared spectrometer (FT-IR, Thermo Fisher Scientific Nicolet iS20, USA); Ultraviolet spectrophotometer (UV-Vis, Shimadzu UV-2600, Japan); X-ray photoelectron spectroscopy (XPS, Thermo Fisher Escalab Xi+, USA).

[0039] 3. Lithium-ion battery cathode materials The decommissioned LCO cathode material used in this embodiment was provided by a new energy and environmental protection technology company in Shenzhen, Guangdong Province.

[0040] After complete discharge, the aluminum foil on the surface of the decommissioned LCO cathode material was removed, and 0.1g of lithium cobalt oxide cathode material (hereinafter referred to as LCO) was taken as a sample and used for experiments in the examples and comparative examples.

[0041] Example 1 A method for high-value recycling of lithium cobalt oxide battery cathode materials includes the following specific steps: S1: Add 0.1g LCO to a 100mL zirconia ball mill, along with 0.15g H2C2O4 and 2mL H2O2 for grinding. Control the ball-to-material ratio at 30:1, the ball mill speed at 600rpm, and the grinding time at 120min. The mass ratio of H2C2O4 to LCO is 1.5:1. S2: After grinding, wash the mixture from the ball mill jar with deionized water to 100 mL, and then perform leaching treatment, controlling the leaching temperature at 30℃ and the leaching time at 120 min; S3: After leaching, the residue and filtrate were obtained by suction filtration using 0.22 µm filter paper. The filter residue, after washing, drying, and grinding, was used for characterization experiments; the filtrate, after being shaken well and brought to a final volume, was then analyzed for Co using ICP-OES. 2+ / Co 3+ and Li + oxalization efficiency; S4: Add lithium precipitant KF to the filtrate obtained in step S3 to achieve the conversion of LiHC2O4 to LiF. The filtered residue is washed, dried and ground to obtain LiF, which is then used for characterization experiments. S5: Use regenerable Amberlyst-15 ion exchange resin to exchange K in the LiF conversion residue. + This process regenerates H₂C₂O₄. The main component in the solution is converted to H₂C₂O₄, which is then characterized after evaporation and crystallization.

[0042] To verify the effect of the ball-to-material ratio on the leaching efficiency of Li and Co, Experimental Example 1 was set up based on Example 1.

[0043] Experimental Example 1 A method for high-value recycling of lithium cobalt oxide battery cathode materials differs from Example 1 in that the ball-to-material ratio in step S1 is adjusted to 40:1, 50:1, 60:1, and 70:1, respectively.

[0044] The leaching efficiencies of Li and Co in Example 1 and Experimental Example 1 are as follows: Figure 1 As shown in Figure a, when the ball-to-material ratio is 30, the leaching efficiencies of Li and Co are 91.91% and 4.13%, respectively. When the ball-to-material ratio is increased to 40, the leaching efficiencies of Li and Co increase to 95.69% and 4.41%, respectively. When the ball-to-material ratio is increased to 50, the leaching efficiency of Li reaches 100%, while the leaching efficiency of Co decreases to 4.16%. Further increases in the ball-to-material ratio lead to a decrease in the leaching efficiencies of both Li and Co. Excessive zirconium oxide balls cause agglomeration during the mechanical oxalicization process, preventing the reaction from proceeding completely and thus causing a decrease in the leaching efficiencies of Li and Co. It is noteworthy that in the series of experiments affecting the ball-to-material ratio, the leaching efficiency of Co is approximately 4%, and the leachate is green. Studies have shown that soluble [Co(C2O4)3]... 3- The complex is green, which to some extent increases the solubility of Co in solution. Therefore, a ball-to-material ratio of 50 is more suitable.

[0045] Example 2 A method for high-value recycling of lithium cobalt oxide battery cathode materials includes the following specific steps: S1: Add 0.1g LCO to a 100mL zirconia ball mill, along with 0.15g H2C2O4 and 2mL H2O2 for grinding. Control the ball-to-material ratio at 50:1, the ball mill speed at 600rpm, and the grinding time at 120min. The mass ratio of H2C2O4 to LCO is 1.5:1. S2: After grinding, wash the mixture from the ball mill jar with deionized water to 100 mL, and then perform leaching treatment, controlling the leaching temperature at 30℃ and the leaching time at 120 min; S3: After leaching, the residue and filtrate were obtained by suction filtration using 0.22 µm filter paper. The filter residue, after washing, drying, and grinding, was used for characterization experiments; the filtrate, after being shaken well and brought to a final volume, was then analyzed for Co using ICP-OES. 2+ / Co 3+ and Li + oxalization efficiency; S4: Add lithium precipitant KF to the filtrate obtained in step S3 to achieve the conversion of LiHC2O4 to LiF. The filtered residue is washed, dried and ground to obtain LiF, which is then used for characterization experiments. S5: Use regenerable Amberlyst-15 ion exchange resin to exchange K in the LiF conversion residue. + This process regenerates H₂C₂O₄. The main component in the solution is converted to H₂C₂O₄, which is then characterized after evaporation and crystallization.

[0046] To verify the effect of the mass ratio of H2C2O4 to LCO on the leaching efficiency of Li and Co, Experimental Example 2 was set up based on Example 2.

[0047] Experiment Example 2 A method for high-value recycling of lithium cobalt oxide battery cathode material differs from Example 2 in that the mass ratio of H2C2O4 and LCO in step S1 is adjusted to 0.5:1, 1:1, 2:1, 2.5:1 and 3:1, respectively, and H2C2O4 is not added.

[0048] The leaching efficiencies of Li and Co in Example 2 and Experiment 2 are as follows: Figure 1 As shown in b, before the H₂C₂O₄ to LCO mass ratio is 1, the leaching efficiency of both Li and Co increases with the increase of the mass ratio. The addition of more H₂C₂O₄ provides excellent conditions for the breaking of Li-O and Co-O bonds. When the H₂C₂O₄ to LCO mass ratio is increased to 1.5, the leaching efficiency of Li reaches 100%, while the leaching efficiency of Co decreases to 4.16%. This is because when the H₂C₂O₄ to LCO mass ratio is 1.5, the amount of H₂C₂O₄ added is excessive, achieving complete leaching of Li. The decrease in Co leaching efficiency is due to the increased interaction with oxalate ions, which promotes the formation of CoC₂O₄·2H₂O. When the mass ratio is increased to 2.0, the leaching efficiency of Li is 100%, and the leaching efficiency of Co is 2.54%. Further increasing the mass ratio of H₂C₂O₄ to LCO resulted in an increase in the leaching efficiency of Co. This is because the addition of excessive H₂C₂O₄ led to a reaction shifting towards [Co(C₂O₄)₃]. 3- The direction of the complex is considered. Taking into account material consumption and economic costs, a mass ratio of H₂C₂O₄ to LCO of 2 is chosen as the optimal condition.

[0049] Example 3 A method for high-value recycling of lithium cobalt oxide battery cathode materials includes the following specific steps: S1: Add 0.1g LCO to a 100mL zirconia ball mill, and add 0.2g H2C2O4 and 2mL H2O2 for grinding. Control the ball-to-material ratio to be 50:1, the ball mill speed to be 600rpm, and the grinding time to be 120min. The mass ratio of H2C2O4 to LCO is 2:1. S2: After grinding, wash the mixture from the ball mill jar with deionized water to 100 mL, and then perform leaching treatment, controlling the leaching temperature at 30℃ and the leaching time at 120 min; S3: After leaching, the residue and filtrate were obtained by suction filtration using 0.22 µm filter paper. The filter residue, after washing, drying, and grinding, was used for characterization experiments; the filtrate, after being shaken well and brought to a final volume, was then analyzed for Co using ICP-OES. 2+ / Co 3+ and Li + oxalization efficiency; S4: Add lithium precipitant KF to the filtrate obtained in step S3 to achieve the conversion of LiHC2O4 to LiF. The filtered residue is washed, dried and ground to obtain LiF, which is then used for characterization experiments. S5: Use regenerable Amberlyst-15 ion exchange resin to exchange K in the LiF conversion residue. + This process regenerates H₂C₂O₄. The main component in the solution is converted to H₂C₂O₄, which is then characterized after evaporation and crystallization.

[0050] To verify the effect of H2O2 addition on the leaching efficiency of Li and Co, Experiment 3 was set up based on Example 3.

[0051] Experimental Example 3 A method for high-value recycling of lithium cobalt oxide battery cathode materials differs from Example 3 in that the amount of H2O2 added in step S1 is adjusted to 0.5 mL, 1 mL, 1.5 mL, 2.5 mL and 3 mL, respectively, and no H2O2 is added.

[0052] The leaching efficiencies of Li and Co in Example 3 and Experiment 3 are as follows: Figure 1As shown in -c, appropriately increasing the amount of H2O2 added helps to lower the reaction energy barrier and accelerate the reaction rate. Furthermore, the liquid medium prevents LCO from adhering to the inner wall of the mill jar and the surface of the mill balls, thus improving the leaching efficiency of Li and Co by promoting complete reaction. When the amount of H2O2 added is 0.5 mL, the leaching efficiencies of Li and Co are 83.26% and 3.12%, respectively. The leaching efficiency of Li and Co increases with increasing H2O2 addition, up to 1.5 mL. At this point, the leaching efficiency of Li reaches 99.56%, and the leaching efficiency of Co is 3.04%. When the amount of H2O2 added is increased to 2.0 mL, the leaching efficiency of Li reaches 100%, while the leaching efficiency of Co decreases to 2.54%. Further increasing the amount of H2O2 adds further increases the leaching efficiency of Co. This is because excessive liquid reduces energy transfer during the milling impact process, causing the reaction to proceed towards the formation of [Co(C2O4)3]. 3- Therefore, the amount of H2O2 added was chosen to be 2 mL, with a volume-to-mass ratio of 20:1 mL / g to LCO.

[0053] To verify the effect of ball milling speed on the leaching efficiency of Li and Co, Experiment 4 was set up based on Example 3.

[0054] Experiment Example 4 A method for high-value recycling of lithium cobalt oxide battery cathode materials differs from Example 3 in that the ball milling speed in step S1 is adjusted to 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm and 700 rpm respectively.

[0055] The leaching efficiencies of Li and Co in Example 3 and Experiment 4 are as follows: Figure 1 As shown in Figure -d, within the ball milling speed range (100-700 rpm), the leaching efficiency of Li and Co increases with increasing ball milling speed. At a ball milling speed of 100 rpm, the leaching efficiency of Li is 76.84%, and that of Co is 2.13%. At a ball milling speed of 200 rpm, the leaching efficiency of Li is 97.88%, and that of Co is 2.18%. When the ball milling speed is increased to 300 rpm, the leaching efficiency of Li reaches 100%, and that of Co is 2.19%. Further increasing the ball milling speed does not change the leaching efficiency of Li, which remains at 100%, while the leaching efficiency of Co continues to increase. Considering energy consumption, a ball milling speed of 300 rpm is preferred.

[0056] Example 4 A method for high-value recycling of lithium cobalt oxide battery cathode materials includes the following specific steps: S1: Add 0.1g LCO to a 100mL zirconia ball mill, and add 0.2g H2C2O4 and 2mL H2O2 for grinding. Control the ball-to-material ratio to be 50:1, the ball mill speed to be 300rpm, and the grinding time to be 120min. The mass ratio of H2C2O4 to LCO is 2:1. S2: After grinding, wash the mixture from the ball mill jar with deionized water to 100 mL, and then perform leaching treatment, controlling the leaching temperature at 30℃ and the leaching time at 120 min; S3: After leaching, the residue and filtrate were obtained by suction filtration using 0.22 µm filter paper. The filter residue, after washing, drying, and grinding, was used for characterization experiments; the filtrate, after being shaken well and brought to a final volume, was then analyzed for Co using ICP-OES. 2+ / Co 3+ and Li + oxalization efficiency; S4: Add lithium precipitant KF to the filtrate obtained in step S3 to achieve the conversion of LiHC2O4 to LiF. The filtered residue is washed, dried and ground to obtain LiF, which is then used for characterization experiments. S5: Use regenerable Amberlyst-15 ion exchange resin to exchange K in the LiF conversion residue. + This process regenerates H₂C₂O₄. The main component in the solution is converted to H₂C₂O₄, which is then characterized after evaporation and crystallization.

[0057] To verify the effect of ball milling time on the leaching efficiency of Li and Co, Experiment 5 was set up based on Example 4.

[0058] Experimental Example 5 A method for high-value recycling of lithium cobalt oxide battery cathode materials differs from Example 4 in that the ball milling time in step S1 is adjusted to 10 min, 30 min, 60 min, 90 min, and 150 min, respectively.

[0059] The leaching efficiencies of Li and Co in Example 4 and Experimental Example 5 are as follows: Figure 1As shown in Figure -e, when the ball milling time is 10 min, the leaching efficiencies of Li and Co are 13.21% and 3.61%, respectively. Within the ball milling time range of 10-120 min, the leaching efficiency of Li increases with increasing ball milling time, while the opposite is true for Co. This is because longer ball milling time allows for a more complete reaction and reduces the amount of [Co(C2O4)3]3- generated. When the ball milling time is 120 min, the leaching efficiency of Li reaches 100%, while the leaching efficiency of Co is 2.19%. Further extending the ball milling time does not significantly change the leaching efficiency of Li, but the leaching efficiency of Co begins to increase again. Excessively long ball milling times may negatively impact the leaching efficiency of [Co(C2O4)3]3-. 3- The formation of [something] has a certain promoting effect. Considering time and economic costs, a ball milling time of 120 min was selected.

[0060] Based on the above embodiments and experimental examples, the optimal process conditions for the mechanical oxalicization of LCO were determined to be: a ball-to-material ratio of 50, a H₂C₂O₄ to LCO mass ratio of 2:1, a H₂O₂ to LCO ratio of 20:1 mL / g, a ball milling speed of 300 rpm, and a ball milling time of 120 min. Under these optimal process conditions, the leaching efficiencies of Li and Co were 100% and 2.19%, respectively.

[0061] Example 5 A method for high-value recycling of lithium cobalt oxide battery cathode materials includes the following specific steps: S1: Add 0.1g LCO to a 100mL zirconia ball mill, and add 0.2g H2C2O4 and 2mL H2O2 for grinding. Control the ball-to-material ratio to be 50:1, the ball mill speed to be 300rpm, and the grinding time to be 120min. The mass ratio of H2C2O4 to LCO is 2:1. S2: After grinding, wash the mixture from the ball mill jar with deionized water to 100 mL, and then perform leaching treatment, controlling the leaching temperature at 30℃ and the leaching time at 60 min; S3: After leaching, the residue and filtrate were obtained by suction filtration using 0.22 µm filter paper. The filter residue, after washing, drying, and grinding, was used for characterization experiments; the filtrate, after being shaken well and brought to a final volume, was then analyzed for Co using ICP-OES. 2+ / Co 3+ and Li + oxalization efficiency; S4: Add lithium precipitant KF to the filtrate obtained in step S3 to achieve the conversion of LiHC2O4 to LiF. The filtered residue is washed, dried and ground to obtain LiF, which is then used for characterization experiments. S5: Use regenerable Amberlyst-15 ion exchange resin to exchange K in the LiF conversion residue. + This process regenerates H₂C₂O₄. The main component in the solution is converted to H₂C₂O₄, which is then characterized after evaporation and crystallization.

[0062] To verify the effect of leaching temperature on the leaching efficiency of Li and Co, Experimental Example 6 was set up based on Example 5.

[0063] Experimental Example 6 A method for high-value recycling of lithium cobalt oxide battery cathode materials differs from Example 4 in that the leaching temperatures in step S2 are adjusted to 20°C, 40°C, 50°C, 60°C, and 70°C, respectively.

[0064] The leaching efficiency results of Li and Co in Example 5 and Experimental Example 6 are as follows: Figure 2 As shown in Figure a, within the temperature range of 20-70 °C, the leaching efficiency of Li remains at 100%, while the leaching efficiency of Co shows a trend of first slightly decreasing and then slightly increasing. Under high-temperature conditions, [Co(C2O4)3] 3- The decomposition of the compound into CoC₂O₄·2H₂O slightly reduces the leaching efficiency of Co. The increase in Co leaching efficiency in the later stages is due to the increased solubility of CoC₂O₄·2H₂O with increasing temperature. The leaching effect is optimal at a leaching temperature of 50℃. At this temperature, the leaching efficiencies of Li and Co are 100% and 1.73%, respectively.

[0065] Example 6 A method for high-value recycling of lithium cobalt oxide battery cathode materials includes the following specific steps: S1: Add 0.1g LCO to a 100mL zirconia ball mill, and add 0.2g H2C2O4 and 2mL H2O2 for grinding. Control the ball-to-material ratio to be 50:1, the ball mill speed to be 300rpm, and the grinding time to be 120min. The mass ratio of H2C2O4 to LCO is 2:1. S2: After grinding, wash the mixture from the ball mill jar with deionized water to 100 mL, and then perform leaching treatment, controlling the leaching temperature at 50℃ and the leaching time at 60 min; S3: After leaching, the residue and filtrate were obtained by suction filtration using 0.22 µm filter paper. The filter residue, after washing, drying, and grinding, was used for characterization experiments; the filtrate, after being shaken well and brought to a final volume, was then analyzed for Co using ICP-OES. 2+ / Co 3+ and Li + oxalization efficiency; S4: Add lithium precipitant KF to the filtrate obtained in step S3 to achieve the conversion of LiHC2O4 to LiF. The filtered residue is washed, dried and ground to obtain LiF, which is then used for characterization experiments. S5: Use regenerable Amberlyst-15 ion exchange resin to exchange K in the LiF conversion residue. + This process regenerates H₂C₂O₄. The main component in the solution is converted to H₂C₂O₄, which is then characterized after evaporation and crystallization.

[0066] To verify the effect of leaching time on the leaching efficiency of Li and Co, Experiment 7 was set up based on Example 6.

[0067] Experimental Example 7 A method for high-value recycling of lithium cobalt oxide battery cathode materials differs from Example 4 in that the leaching time in step S2 is adjusted to 10 min, 20 min, 30 min, 40 min, 50 min, and 70 min, respectively.

[0068] The leaching efficiency results of Li and Co in Example 6 and Experimental Example 7 are as follows: Figure 2 As shown in b, within the leaching time range of 10-70 min, the leaching efficiency of Li remained at 100%. The leaching efficiency of Co decreased slightly and then stabilized. The leaching effect was optimal when the leaching time was 50 min, with leaching efficiencies of 100% for Li and 1.70% for Co.

[0069] In summary, the optimal leaching temperature was determined to be 50 ℃ and the leaching time to be 50 min.

[0070] Under optimal process conditions, the leaching efficiencies of Li and Co are 100% and 1.70%, respectively. Although the leaching efficiency of Li reaches 100%, the leaching efficiency of Co is still greater than 1%. In practical applications, further separation of Co from the leachate is required, increasing unnecessary costs. To further reduce the leaching efficiency of Co while maintaining the same leaching efficiency of Li, the inventors designed a new recovery method based on the aforementioned optimal process conditions.

[0071] Example 7 A method for high-value recycling of lithium cobalt oxide battery cathode materials includes the following specific steps: S1: Take 0.1g of LCO for pretreatment, the pretreatment being low-temperature plasma treatment; The low-temperature plasma pretreatment specifically involves placing LCO into a low-temperature plasma surface treatment instrument for pretreatment. The plasma is an Ar / H2 mixed gas (volume ratio 9:1), the power is 100-150 W, and the treatment time is 5-10 min. S2: Add the pretreated LCO to a 100mL zirconia ball mill, along with 0.2g H2C2O4, 2mL H2O2, and nano ZrO2 for grinding. Control the ball-to-material ratio at 50:1, the ball mill speed at 300rpm, and the grinding time at 120min. The mass ratio of H2C2O4 to LCO is 2:1, and the mass ratio of nano ZrO2 to LCO is 1:10. The particle size of the nano-ZrO2 is 20-50 nm; S3: After grinding, wash the mixture from the ball mill jar with deionized water to 100 mL, and then perform leaching treatment, controlling the leaching temperature at 50℃ and the leaching time at 50 min; S4: After leaching, the residue and filtrate were obtained by suction filtration using 0.22 µm filter paper. The filter residue, after washing, drying, and grinding, was used for characterization experiments; the filtrate, after being shaken well and brought to a final volume, was then analyzed for Co using ICP-OES. 2+ / Co 3+ and Li + oxalization efficiency; S5: Add lithium precipitant KF to the filtrate obtained in step S3 to achieve the conversion of LiHC2O4 to LiF. The filtered residue is washed, dried and ground to obtain LiF, which is then used for characterization experiments. S6: Use regenerable Amberlyst-15 ion exchange resin to exchange K in the LiF conversion residue. + This process regenerates H₂C₂O₄. The main component in the solution is converted to H₂C₂O₄, which is then characterized after evaporation and crystallization.

[0072] To verify the effectiveness of Embodiment 7 of the present invention, comparative examples 1-5 were set up for recycling methods.

[0073] Comparative Example 1 A method for high-value recycling of lithium cobalt oxide battery cathode materials differs from Example 7 in that the pretreatment step S1 is omitted.

[0074] Comparative Example 2 A method for high-value recycling of lithium cobalt oxide battery cathode material, which differs from Example 7 in that the S2 step does not involve the addition of nano-ZrO2.

[0075] Comparative Example 3 A method for high-value recycling of lithium cobalt oxide battery cathode material differs from Example 7 in that the S1 pretreatment is not performed and nano ZrO2 is not added in the S2 step.

[0076] Comparative Example 4 A method for high-value recycling of lithium cobalt oxide battery cathode material differs from Example 7 in that hydrochloric acid (HCl) is used to replace the original H2C2O4 in step S2, and the mass of hydrogen chloride in the hydrochloric acid is 0.2g.

[0077] Comparative Example 5 A method for high-value recycling of lithium cobalt oxide battery cathode material differs from Example 7 in that, in step S2, an equal amount of citric acid (C6H8O7) is used to replace the original H2C2O4.

[0078] Comparative Example 6 A method for high-value recycling of lithium cobalt oxide battery cathode material differs from Example 7 in that, in step S1, an equal amount of NH4Cl is used to replace the original H2C2O4.

[0079] The leaching efficiency results of Li and Co in Example 7 and Comparative Examples 1-5 are shown in Table 1 below.

[0080] Table 1. Leaching efficiency results of Li and Co Example 7 100 0.97 Comparative Example 1 100 1.38 Comparative Example 2 100 1.72 Comparative Example 3 100 2.19 Comparative Example 4 100 58.59 Comparative Example 5 63.50 30.77 Comparative Example 6 2.93 0.75 Comparing the data from Example 7 and Comparative Example 3, it can be seen that pretreatment of LCO and the addition of nano-grinding aids can further reduce the leaching efficiency of Co. The Co leaching efficiency of Comparative Examples 1 and 2, compared to the optimal process conditions of Comparative Example 3, both showed a decrease, further demonstrating the effectiveness of pretreatment and the addition of nano-grinding aids in reducing Co leaching efficiency. When other acids were used instead of oxalic acid (Comparative Examples 4 and 5), the Co leaching efficiency increased significantly. Excessive Co leaching efficiency affects the separation of Li and Co, requiring the use of additional reagents, such as sodium hydroxide to convert divalent and trivalent cobalt into precipitates. This not only increases recovery costs but also affects the purity of the recovered material, reducing its recovery value. When hydrochloric acid is used, its high H₂ content... + The environment enhances the reducing power of hydrogen peroxide (hydrogen peroxide releases electrons more readily under acidic conditions), accelerating the reduction of Co. 3+ Converted to Co 2+ But these two are related to Cl - The complexes are all soluble, which promotes the transfer of Co from solid LCO to the solution phase, thus significantly improving the leaching efficiency of Co. When using citric acid, because citric acid is weaker than hydrochloric acid and oxalic acid, it cannot provide a sufficient acidic environment for hydrogen peroxide to reduce Co. 3+ Converted to Co 2+ Citrate can also react with Co. 3+ Co 2+The formation of soluble complexes promotes the transfer of Co from solid LCO to the solution phase, improving the leaching efficiency of Co. However, due to the weak acidity of citric acid, it cannot completely leach Li from LCO, with a leaching efficiency of only 63.50%. When ammonium chloride is used instead of oxalic acid (Comparative Example 6), almost no Li or Co is leached from LCO, indicating that the ammonium chloride-hydrogen peroxide mechanical grinding system has little effect on treating LCO cathode materials and is not suitable for recycling LCO cathode materials.

[0081] To verify the effect of lithium precipitation agent on Li recovery of LCO cathode material, comparative examples 7-9 were set up based on Example 7.

[0082] Comparative Example 7 A method for high-value recycling of lithium cobalt oxide battery cathode materials differs from Example 7 in that NH4F is used as a lithium precipitation agent in step S5.

[0083] Comparative Example 8 A method for high-value recycling of lithium cobalt oxide battery cathode materials differs from Example 7 in that NaF is used as a lithium precipitation agent in step S5.

[0084] Comparative Example 9 A method for high-value recycling of lithium cobalt oxide battery cathode material differs from Example 7 in that hydrochloric acid (HCl) is used to replace the original H2C2O4 in step S2, and the mass of hydrogen chloride in the hydrochloric acid is 0.2g; and NaF is used as a lithium precipitation agent in step S5.

[0085] The conversion rate of Li and the purity of LiF in the recovery methods of Examples 7 and Comparative Examples 1-9 are shown in Table 2.

[0086] Table 2. Conversion rate of Li and purity of LiF Example 7 99.23 99.71 Comparative Example 1 98.94 99.41 Comparative Example 2 98.97 99.49 Comparative Example 3 98.81 99.37 Comparative Example 4 94.06 85.31 Comparative Example 5 89.15 84.29 Comparative Example 6 86.52 88.35 Comparative Example 7 95.53 95.82 Comparative Example 8 94.32 92.17 Comparative Example 9 78.24 94.69 Comparing the data from Example 7 and Comparative Examples 1-3, it can be seen that the recovery method of the present invention can efficiently recover Li and convert Li into high-purity LiF. However, Comparative Examples 4-6, due to the use of other substances, resulted in a relatively high Co leaching rate. On the one hand, Co ions compete with Li ions for F ions, affecting the Li conversion rate; on the other hand, CoF3 is difficult to dissolve and forms a precipitate, affecting the purity of LiF. Comparative Examples 7 and 8 (with a different lithium precipitation agent) showed good conversion rates and purity, both above 92%, but still not as good as the KF lithium precipitation agent of the present invention. This is because NH4... + and Na + Its adsorption capacity is greater than K +Therefore, it will adsorb onto the LiF lattice, affecting the conversion rate and purity. Comparative Example 9 (using other acids and other lithium precipitation agents) will further reduce the conversion rate of Li and the purity of LiF, seriously affecting the recovery effect.

[0087] The working principle of the recycling method of this invention is as follows: The recovery method of this invention consists of three modules: plasma pretreatment activation (step S1), mechanical oxalate treatment (steps S2 and S3), and lithium precipitation recovery (steps S4 and S5). These three modules work synergistically to achieve efficient separation and recovery of Li and Co. Specifically, Ar ions in the plasma can bombard the LCO surface to create surface defects, aiding subsequent mechanical polishing. Furthermore, they can act on the low-energy Li-O bonds to produce Li... + Vacancies provide active sites for subsequent reactions. H radicals in the plasma can ignite Co on the surface. 3+ Reduced to Co 2+ To prevent these Co 3+ It first reacts with the oxalate ligand to form [Co(C2O4)3]. 3- Complex.

[0088] The mechanical oxalic acidification module of this invention can break the Li-O and Co-O bonds in LCO, achieving selective release of lithium (Li) from decommissioned LCO cathode materials. This process further utilizes leaching and solid-liquid separation operations to facilitate the transfer of lithium to the liquid phase. Simultaneously, most of the cobalt (Co) is reduced to divalent Co by hydrogen peroxide and remains in the solid phase as CoC2O4·2H2O, thus achieving effective separation of lithium and cobalt. After the separation of CoC2O4·2H2O, the main components of the solution become LiHC2O4 and excess H2C2O4. The grinding aid nano-zirconia in this step has two functions: firstly, it assists in grinding, provides a buffering effect, allows mechanical force to act more evenly on the crystal lattice, and controls the Co content. 3+ Release rate, avoid Co 3+ A large amount escapes and reacts with oxalate ligands to form [Co(C2O4)3]. 3- On the other hand, the hydroxyl groups on the surface of nano-zirconia competitively bind to oxalate ions, further preventing Co from forming. 3+ Direct oxalate ligand formation of [Co(C2O4)3] 3- Complex.

[0089] The lithium precipitation and recovery module of this invention can achieve efficient recovery of Li and regeneration and recycling of H2C2O4. Firstly, based on the main components of the solution after separation, potassium fluoride (KF) is selected as the lithium precipitation agent. This selection has significant advantages: KF can completely dissociate into potassium ions (K+) in water. + ) and fluoride ions (F -Fluoride ions can undergo a highly selective metathesis reaction with LiHC2O4 to generate high-purity lithium fluoride (LiF). LiF is a high-value-added product with better practical application value.

[0090] Furthermore, due to fluoride ions (F... - The alkalinity of ) is compared to that of HC2O4 - The conjugate base is weaker, and fluoride ions cannot be effectively removed from HC₂O₄. - It extracts a proton to generate hydrogen fluoride (HF) and oxalate ions (C2O4). 2- Based on this, the reaction pathway exhibits high specificity, and the risk of side reactions can be effectively controlled. Furthermore, the reaction can proceed smoothly under mild conditions of ambient temperature and pressure, and the aqueous solution system ensures that the reaction occurs in a homogeneous environment, laying a solid foundation for the preparation of high-purity LiF.

[0091] After the fluorination reaction is complete, the main cation in the LiF conversion residue is K. + At this point, Amberlyst-15 type strong acid cation exchange resin can be used to achieve the regeneration and recycling of H2C2O4.

[0092] Instructions for use of Amberlyst-15 resin: Amberlyst-15 resin has sulfonic acid groups (-SO3H) attached to it. In water, these groups can release H+. + This leads to the formation of negatively charged -SO3. - And the freely movable H + The H on these resins + It will undergo an exchange reaction with cations in the solution. Furthermore, this resin possesses excellent regeneration properties. When the resin adsorbs other cations during use, simply contacting it with acid will cause the cations on the resin to be converted by H+. + Replacement, thereby restoring it to H-type resin.

[0093] Before regenerating H2C2O4, the resin needs to be packed into a column and pretreated. The specific steps are as follows: First, thoroughly mix Amberlyst-15 resin and deionized water in a beaker, then slowly pour this mixture into a graduated cylinder. Let it stand for a period of time to allow the resin to settle completely. Add or remove deionized water as needed to align the resin bed with the corresponding graduations on the graduated cylinder, thus ensuring accurate resin measurement. Next, close the outlet valve at the bottom of the ion exchange column and, using water flow, guide all the resin from the graduated cylinder into the ion exchange column. Then, open the outlet valve of the exchange column to allow the resin to settle and compact naturally within the column. After this, close the outlet valve again, ready for subsequent use.

[0094] During pretreatment, a 1 mol / L sulfuric acid solution was used to treat the resin in a forward column feed. After pretreatment, the resin was rinsed with pure water. The washed resin could then be used for H₂C₂O₄ regeneration. When the LiF conversion residue was passed through the resin column at a specific flow rate, the sulfonic acid groups loaded on the resin underwent an ion exchange reaction with K⁺ in the solution, releasing H₂. + H + Then reacted with HC2O4 - The process combines to regenerate a certain amount of H2C2O4, which can then be reused in the mechanical oxaloate stage.

[0095] To investigate the principle of the mechanical oxaloacetization process of this invention, the following mechanism verification experiments were conducted: 1. Experimental study on the mechanism of H2O2-H2C2O4 synergistic enhancement of LCO mechanical leaching In existing technologies, H2O2 and Cl are used. - Examples of co-processing LFP (lithium iron phosphate battery cathode material) require the addition of a quencher to prevent Fe-O bond breakage. Co is chemically more stable than Fe and requires a stronger acidic environment; however, as shown in Comparative Example 4, using a hydrochloric acid and hydrogen peroxide system increases the leaching rate of Co, and Cl... - Hydrochloric acid is not suitable for LCO because it forms soluble complexes with divalent Co. Based on the characteristics of LCO and the properties of hydrogen peroxide, and through a series of repeated experiments, the inventors discovered the need for a substance with moderate acidity, some reducing properties, and an anion that cannot react with Co. 2+ After a series of verification experiments, the inventors identified oxalic acid as a soluble substance that can be formed.

[0096] First, H₂O₂ can act as both an oxidizing agent and a reducing agent. According to the standard potentials shown in Equations 1 and 2, the reduction of H₂O₂ is thermodynamically more feasible than its oxidation; that is, H₂O₂ acts more as an oxidizing agent thermodynamically. Studies have shown that oxalic acid also has reducing properties and can partially reduce Co. 3+ Restored to Co 2+ For example, Equations 3 and 4.

[0097] H2O2 + 2H + + 2e - ⇌ 2H2O E 0 = 1.763V ΔG 0 = -339.63 kJ (1) H2O2 ⇌ O2 +2H + +2e - E 0 = -0.68V ΔG0 = 131.22 kJ (2) Co 3+ + e - ⇌Co 2+ E 0 = 1.92 V ΔG 0 = -185.25 kJ (3) C2O4 2- ⇌ 2CO2 + 2e - E 0 = 0.49 V ΔG 0 = -94.55 kJ (4) To further verify the key roles of H2O2-H2C2O4 in the LCO mechanical oxalic acidification system, Experiment 8 was set up.

[0098] Experimental Example 8 Based on the optimal oxalic acid mechanization process conditions in Example 4, control experiments were conducted in step S2 to set up different systems: blank, H2O2-H2C2O4, H2C2O4, H2O2, and H2O-H2C2O4.

[0099] The leaching efficiency results of Li and Co in Experiment Example 8 are as follows: Figure 3 As shown.

[0100] Under natural ball milling conditions (blank group), the leaching efficiencies of Li and Co were 2.91% and 0.02%, respectively, with only a very small number of Li-O and Co-O bonds breaking. In the H₂O₂-H₂C₂O₄ mechanical oxalate system, the leaching efficiency of Li was 100%, and that of Co was 2.19%. With only H₂C₂O₄, the leaching efficiency of Li was 3.01%, and that of Co was 1.32%, a slight improvement compared to natural ball milling, but the solid-phase reaction is difficult to complete without the presence of liquid. With only H₂O₂, the leaching efficiencies of Li and Co were 2.56% and 0.02%, respectively, indicating that the conversion efficiencies of Li and Co remained extremely low. Under the H2O-H2C2O4 mechanical oxalic acidification system, some unreacted LCO still exists in the solid filter residue. At this point, the leaching efficiency of Li is 7.42%, while the leaching efficiency of Co increases to 27.79%. The solution appears dark green, indicating that LCO is not completely converted; only some Co-O bonds have broken, but Co... 3+ It was not reduced and existed in solution as a complex. Subsequently, H₂O₂ was added to the dark green solution, and the solution color did not change significantly, indicating that the oxalic acid ligand reacted with Co. 3+ The strong coordination effect makes [Co(C2O4)3] 3-More stable, the reduction reaction of the complex requires overcoming a higher energy barrier. Co 3+ It is difficult to restore.

[0101] In summary, in the H₂O₂-H₂C₂O₄ mechanoxate oxidative acidification system, the main role of H₂C₂O₄ is to break Li-O and Co-O bonds and to provide anions for Co bonding. The main role of H₂O₂ in the system is to bond Co... 3+ Restored to Co 2+ The addition of H2O2 can lower the reaction energy barrier and accelerate the reaction of Co. 3+ The reduction to Co 2+ This greatly inhibited the formation of [Co(C2O4)3]. 3- Formation of the complex. In this system, most of the Co undergoes bond breaking and reduction reactions, and then reacts with C2O4. 2- The reaction produces a precipitate of CoC₂O₄·2H₂O with a purity of 99.34%. The remaining Co first undergoes bond breaking to transform into free Co. 3+ Subsequently with C2O4 2- Combined to form [Co(C2O4)3] 3- Coordination compounds.

[0102] [Co(C2O4)3] 3- Validation of the complex: During the implementation of the above recovery method, a green byproduct often occurs in the leachate. To determine the presence of this green byproduct, UV-Vis (ultraviolet-visible spectrophotometry) was used to measure the absorbance of the leachate in the visible light region under different ball milling times. The results are as follows: Figure 4 As shown, the leachates from ball milling times of 10 min, 30 min, 60 min, and 120 min all exhibited peak absorbance around 400 nm. 0.1 mol / L K3[Co(C2O4)3] has previously been reported to have a maximum absorbance peak at 420 nm. Although the peak position shifted slightly, Co... 3+ The presence of the complex causes the solution to turn green, indicating that [Co(C2O4)3] was formed in the early stage of LCO mechanical oxaloacetization. 3- The shift in the maximum absorption peak is attributed to the difference in cations; this invention is based on Li + This may result in the energy gap between the bonding and antibonding orbitals of the coordination compounds in this system being higher than that of K3[Co(C2O4)3].

[0103] Based on this, the applicant devised a synergistic effect between plasma pretreatment and nano-zirconia grinding aid to prevent Co 3+ In the early stages of mechanooxalization, it first reacts with oxalic acid ligands to form [Co(C2O4)3]. 3- Plasma pretreatment removes Co3 from the LCO surface beforehand.+ Converted to Co 2+ In mechanical oxalic acid and can prevent Co from the beginning 3+ In the early stages of mechanooxalization, it first reacts with oxalic acid ligands to form [Co(C2O4)3]. 3- The surface defects created by nano-zirconia grinding aids combined with plasma pretreatment allow for a more uniform grinding process, thereby controlling the rate of lattice breakage and consequently controlling the Co content. 3+ Release rate to avoid excessive Co 3+ In the early stages of mechanooxalization, it first reacts with oxalic acid ligands to form [Co(C2O4)3]. 3- Furthermore, the surface of nano-zirconia also contains hydroxyl groups, which can competitively bind to oxalic acid ligands, further preventing Co from binding. 3+ In the early stages of mechanooxalization, it first reacts with oxalic acid ligands to form [Co(C2O4)3]. 3- .

[0104] 2. Main reaction pathways in the mechanical oxalic acidification process of H2O2-H2C2O4 XRD patterns were analyzed on the decommissioned LCO samples and the filter residue samples from each reaction system in Experimental Example 8. The results are as follows: Figure 5 As shown.

[0105] The XRD pattern of the decommissioned LCO sample is as follows: Figure 5 As shown in Figure a. The XRD pattern of the filter residue sample under the H2O-H2C2O4 mechanical oxalic acidification system is shown in Figure a. Figure 5 As shown in b, the main phase is still LiCoO2, which is consistent with the result that only a small portion of Li is leached by oxalic acid treatment. The partial breakage of Co-O bonds also leads to the disappearance of some peaks. The XRD pattern of the mechanically activated LCO sample in the H2O2-H2C2O4 mechanical oxalic acid treatment system is shown below. Figure 5 As shown in c, its main phase has been transformed into CoC2O4·2H2O, accompanied by CoC2O4·4H2O and LiHC2O4·H2O phases. The main phase of the filter residue sample under the H2O2-H2C2O4 system is mainly CoC2O4·2H2O (… Figure 5 d). This indicates that most of the Co has been converted into CoC2O4·2H2O, and Li has also been released from the LCO structure.

[0106] FT-IR spectra were performed on the decommissioned LCO samples and the samples from each reaction system in Experiment 8 before and after mechanical oxalate treatment. The results are as follows: Figure 6 As shown.

[0107] FT-IR spectra of decommissioned LCO samples are as follows Figure 6 As shown in a, 580.83 cm -1The peak is related to the stretching vibration between Co and O in the CoO2 layer. The FT-IR spectrum of the filter residue sample in the H2O-H2C2O4 system is shown below. Figure 6 As shown in b, 3355.65 cm -1 The peak at 1631.85 cm⁻¹ is usually related to the stretching vibration of OH groups in the water of crystallization of CoC₂O₄·2H₂O. -1 The peak at 1314.54 cm⁻¹ is related to the bending vibration of HOH in the water of crystallization of CoC₂O₄·2H₂O. -1 Peak and C2O4 2- The symmetric stretching vibration of medium CO is related, 821.93 cm. -1 The peak at that location is usually associated with C2O4. 2- It is related to the stretching or bending vibrations of the OCO bond in the middle, 418.7 cm. -1 The peak at this location reflects the stretching or bending vibrations of Co-O. The FT-IR spectrum of the LCO sample under the H2O-H2C2O4 mechanoxate oxidation system is shown below. Figure 6 c, 3341.11cm -1 The peak at 1611.77 cm⁻¹ is usually related to the stretching vibration of OH groups in the sample's water of crystallization. -1 The peak at that point corresponds to the HOH bending vibration or C2O4 in the sample's crystallization water. 2- Related to the stretching vibration of C=O, 1358 cm -1 and 1314 cm -1 The peak at that location is related to C2O4 2- or HC2O4 - Related to the symmetric stretching vibration of CO, 824.01 cm -1 The peak at that location is related to C2O4 2- or HC2O4 - The peak at 733.17 cm⁻¹ is related to the bending vibration or ring deformation vibration of OCO, and the peak at 605.77 cm⁻¹ is related to the bending vibration or Co-O vibration of CCO. -1 and 487.29 cm -1 The peaks at these points are typically related to Co-O vibrations. The FT-IR spectra of filter residue samples in the H2O2-H2C2O4 system are shown below. Figure 6 As shown in d, with Figure 6 Compared to c, a small peak position shifted, 740.87 cm. -1 The peak at that point is still related to C2O4. 2- The OCO bending or ring deformation vibration is related to the 612 cm. -1 and 485 cm -1 The peak at that point is related to the Co-O vibration.

[0108] To further confirm the main reaction pathways in the mechanical oxalization process of decommissioned LCO cathode materials, XPS analysis was performed on samples before and after H2O2-H2C2O4 mechanical oxalization. The results are as follows: Figure 7 As shown.

[0109] The Li 1s spectrum shows that the characteristic peak of Li shifted after mechanical oxalic acid treatment. The Li 1s characteristic peak moved from a high binding energy of 54.16 eV to a low binding energy of 51.60 eV, and the peak intensity decreased significantly, indicating bond breaking and release of Li in LiCoO2. After the mechanical oxalic acid treatment, the Co 2p bonds in the decommissioned LCO cathode material... 3 / 2 The main peak shifted from 780.12 eV to 777.71 eV, Co 2p 1 / 2 The main peak shifted from 795.26 eV to 793.81 eV, showing a clear shift towards lower binding energies. This indicates that during mechanoxate oxidation, the Co-O bond in LCO breaks, and Co(III) is reduced to Co(II).

[0110] Verification and analysis of the mechanism of lithium precipitation recovery 1. Conversion mechanism of LiF After filtration and collection, the CoC₂O₄·2H₂O solution was concentrated, and KF was added to convert LiHC₂O₄ to LiF. KF and LiHC₂O₄ dissolved in water dissociated into K₂O₄ and LiF, respectively. + F - and Li + HC2O4 - (Equations 5 and 6). When the two substances are mixed in water, a double displacement reaction occurs. The essence of the reaction can be simplified to the combination of Li⁺ and F⁻ to form a LiF precipitate with extremely low solubility (solubility product K). sp =1.7×10 -3 K⁺ and HC₂O₄⁻ remain in the solution as “bystander ions” and do not participate in further transformations of the reaction (Equations 7 and 8).

[0111] KF→K + +F - (5) LiHC2O4→Li + +HC2O4 - (6) Li + +F - →LiF (7) K + +HC2O4 - →KHC2O4 (8) From a solubility perspective, the low solubility of LiF is the decisive factor for the spontaneous forward reaction, while the solubility of KHC₂O₄ ensures a homogeneous reaction in the system. Furthermore, from the perspective of acid-base interactions, although HC₂O₄ is present in the system... - (pKa2=4.27) and F - (corresponding to HF's pKa = 3.17), but the difference in acid-base strength between the two leads to H + The possibility of transfer is extremely low. - Its alkalinity is weaker than that of HC2O4 - The conjugate base (C2O4) 2- F⁻ cannot effectively capture HC₂O₄ - H in + HF and C2O4 are generated 2- This makes the fluorination reaction pathway highly specific, with no side reactions occurring. The above thermodynamic calculations further support the feasibility of the reaction. The formation of the precipitate significantly reduces the ion concentration in the solution, thereby reducing the entropy of the system and promoting the rapid formation of LiF without the need for additional activation conditions. The effect of temperature is relatively limited. Although the solubility of LiF increases slightly with increasing temperature (e.g., the solubility at 100℃ is approximately 0.134 g / 100 mL), under normal room temperature conditions, the change in solubility is insufficient to significantly inhibit the formation of the precipitate. In summary, the reaction between KF and LiHC2O4 is a precipitation-driven metathesis reaction with both high efficiency and selectivity. Its clear chemical pathway, mild reaction conditions, and easily separable product characteristics make it of significant application value in Li resource recovery and LiF preparation. Experiments show that 98.81% of the Li in the leachate is converted into well-crystallized LiF with a purity of 99.37%. Figure 8 a).

[0112] 2. Regeneration mechanism of H2C2O4 After Li and Co are precipitated, the main cation in the LiF conversion residue is K. + In this invention, the regeneration and recycling of H₂C₂O₄ can be achieved using Amberlyst-15 type strong acid cation exchange resin. The base material of Amberlyst-15 type resin is a styrene-divinylbenzene copolymer, whose backbone structure is a highly cross-linked polymer network. Its supported sulfonic acid groups (-SO₃H) are the main source of the resin's activity. -SO₃H can release H₂ in water. + This forms a negatively charged sulfonate ion (-SO3H) and a freely moving H group. + When a solution containing other cations passes through Amberlyst-15 resin, the H+ on the resin... +It will undergo ion exchange with cations in the solution. The ion exchange process is based on the principles of electrostatic interaction and chemical equilibrium. The -SO3H on the resin and the cations in the solution are attracted to each other through electrostatic attraction, while the H on the resin... + The ions are then displaced into the solution. The -SO3H atoms on the resin attract the cations in the solution through electrostatic attraction, while the H atoms on the resin... + The cations are then displaced into the solution. More importantly, Amberlyst-15 resin is regenerable and can be converted to the H-form through acid treatment, restoring it to its initial active state. For example, saturated Amberlyst-15 strong acid cation exchange resin can be treated with sulfuric acid to replace the cations on the resin with H⁺, thus restoring it to the H-form resin. During potassium removal, the LiF conversion residue flows through the active resin, and the H⁺ in the active resin... + Replace K in LiF conversion residue + This allows for the regeneration and recycling of H2C2O4. Experiments show that recovering 0.1g of decommissioned LCO cathode material can regenerate 127.12mg of H2C2O4·2H2O, and nearly half of the oxalic acid can be regenerated and reused in the mechanical oxalization stage. Furthermore, H2C2O4·2H2O exhibits good crystallinity. Figure 8 b).

[0113] In summary, a schematic diagram of the mechanical oxalization mechanism of decommissioned LCO cathode materials is shown in Figure 9. During mechanical oxalization, H₂C₂O₄ breaks Li-O and Co-O bonds and provides anions for Li and Co to combine, while H₂O₂ acts as a reducing agent to break down Co. 3 + Restored to Co 2+ The addition of H2O2 lowers the reaction energy barrier and accelerates the reaction of Co. 3+ The reduction to Co 2+ This greatly inhibited the formation of [Co(C2O4)3]. 3- Formation of the complex. In this system, Li bonds are broken with HC₂O₄. - The combination forms LiHC₂O₄, during which most of the Co undergoes bond breaking and reduction reactions, and then reacts with C₂O₄. 2- The remaining Co first undergoes bond breaking to form CoC₂O₄·2H₂O precipitate, and then transforms into free Co. 3+ Subsequently with C2O4 2- Combined to form [Co(C2O4)3] 3- The complex failed to participate in the subsequent redox reaction. Based on this, the present invention incorporates low-temperature plasma pretreatment and the addition of nano-zirconia grinding aids to prevent Co from participating in the subsequent redox reaction. 3+ Early stage of ball milling and C2O4 2- Combined to form [Co(C2O4)3] 3-Coordination compounds.

[0114] Subsequently, upon adding KF to the LiHC₂O₄ solution, Li⁺ and F⁻ combine to form a low-solubility LiF precipitate, while K⁺ and HHC₂O₄⁻ do not participate in further conversion, achieving a high-value conversion of LiHC₂O₄ to LiF. During the H₂C₂O₄ regeneration process, the -SO₃H functional groups in the Amberlyst-15 type strong acid cation exchange resin affect the K⁺ in the LiF conversion residue. + It exhibits strong selective adsorption, releasing an equal amount of H₂ during ion exchange. + With HC2O4 - The resulting H2C2O4 can be converted into H2C2O4·2H2O after evaporation and crystallization. The regenerated H2C2O4·2H2O crystallizes well and can be reused in the mechanical oxalic acidification process.

[0115] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for high-value recycling of lithium cobalt oxide battery cathode materials, characterized in that, The specific steps include the following: S1: Place the lithium cobalt oxide cathode material into a ball mill, add nano-zirconia, oxalic acid and hydrogen peroxide for grinding, control the ball-to-material ratio to be (30-70):1, the ball mill speed to be 200-700 rpm, and the grinding time to be 90-150 min; wherein, the mass ratio of oxalic acid to lithium cobalt oxide cathode material is (1.5-3):1, and the volume mass ratio of hydrogen peroxide to lithium cobalt oxide cathode material is (15-30):1 mL / g; S2: After grinding, wash the mixture out of the ball mill jar with deionized water, and then perform leaching treatment, controlling the leaching temperature at 20-70℃ and the leaching time at 10-120 min; S3: After leaching, filter to obtain filter residue and filtrate; The filter residue was washed, dried and ground and then used for characterization experiments; the filtrate was shaken and then brought to a final volume to determine the oxalicization efficiency of cobalt and lithium. S4: Add potassium fluoride, a lithium precipitant, to the filtrate obtained in step S3 to convert lithium oxalate to lithium fluoride. The filtered residue is washed, dried, and ground to obtain lithium fluoride, which is then used for characterization experiments. S5: Use acidic ion exchange resin to exchange potassium ions in the lithium fluoride conversion residue to regenerate oxalic acid; Before being added to the ball mill, the lithium cobalt oxide cathode material in step S1 undergoes low-temperature plasma pretreatment. The low-temperature plasma pretreatment involves placing the lithium cobalt oxide cathode material in a low-temperature plasma surface treatment instrument for pretreatment. The plasma is an Ar / H2 mixed gas with a volume ratio of Ar to H2 of 9:1, a power of 100-150W, and a treatment time of 5-10 min.

2. The method for high-value recycling of lithium cobalt oxide battery cathode material according to claim 1, characterized in that, Includes the following steps: S1: Place the lithium cobalt oxide cathode material into a ball mill, and add nano-zirconia, oxalic acid and hydrogen peroxide for grinding. Control the ball-to-material ratio to be 50:1, the ball milling speed to be 300 rpm, and the grinding time to be 120 min. The mass ratio of oxalic acid to lithium cobalt oxide cathode material is 2:1, and the volume mass ratio of hydrogen peroxide to lithium cobalt oxide cathode material is 20:1 mL / g. S2: After grinding, the mixture is washed out of the ball mill jar with deionized water, and then leaching is performed. The leaching temperature is controlled at 50℃ and the leaching time is 50 min. S3: After leaching, filter to obtain filter residue and filtrate; The filter residue was washed, dried and ground and then used for characterization experiments; the filtrate was shaken and then brought to a final volume to determine the oxalicization efficiency of cobalt and lithium. S4: Add potassium fluoride, a lithium precipitant, to the filtrate obtained in step S3 to convert lithium oxalate to lithium fluoride. The filtered residue is washed, dried, and ground to obtain lithium fluoride, which is then used for characterization experiments. S5: Use acidic ion exchange resin to exchange potassium ions in the lithium fluoride conversion residue to regenerate oxalic acid.

3. The method for high-value recycling of lithium cobalt oxide battery cathode material according to claim 1, characterized in that: The lithium cobalt oxide cathode material in step S1 is obtained by sequentially fully discharging and removing the aluminum foil from a waste lithium cobalt oxide battery.

4. The method for high-value recycling of lithium cobalt oxide battery cathode material according to claim 1, characterized in that: The ball mill is a zirconia ball mill.

5. The method for high-value recycling of lithium cobalt oxide battery cathode material according to claim 1, characterized in that: The mass ratio of the nano-zirconia to the lithium cobalt oxide cathode material is 1:10, and the particle size of the nano-zirconia is 20-50 nm.

6. The method for high-value recycling of lithium cobalt oxide battery cathode material according to claim 1, characterized in that: The acidic ion exchange resin is Amberlyst-15 type ion exchange resin.

7. A method for high-value recycling of lithium cobalt oxide battery cathode material according to claim 6, characterized in that: The resin needs to be packed into columns and pretreated before use.

8. A method for high-value recycling of lithium cobalt oxide battery cathode material according to claim 7, characterized in that: The pretreatment involves treating the resin with a sulfuric acid solution in a forward column injection manner.

9. The application of the method for high-value recycling of lithium cobalt oxide battery cathode material according to any one of claims 1-8 in the recycling of lithium cobalt oxide battery cathode material.

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