Method for removing copper particles in positive electrode material of lithium ion battery based on ammonium-oxygen synergy

Abstract

The invention discloses a method for removing copper particles in a positive electrode material of a lithium ion battery based on ammonium-oxygen synergy. The method comprises the following steps: mixing a nickel-cobalt-manganese ternary positive electrode material of a retired lithium ion battery containing the copper particles with ammonium carbonate; oxygen-containing gas is introduced for a leaching reaction, and copper particles in the positive electrode material are selectively complexed to form soluble complex tetraamminecopper ions; and carrying out solid-liquid separation to obtain the positive electrode material without the copper particles. According to the invention, the self-buffering capability of ammonium carbonate in a specific pH range is utilized, tetraamminecopper ions are formed based on the synergistic effect of ammonium and oxygen, and valuable metal elements such as nickel, cobalt, manganese and the like do not form soluble ammonia complexes under the pH condition and are precipitated in the form of carbonate, oxide or hydroxide, so that efficient separation of copper and the positive electrode material is realized; the method has the advantages of high copper removal efficiency, good selectivity, pH self-buffering, environmental friendliness and the like.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery recycling technology, specifically to a method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal. Background Technology

[0002] With the rapid development of the electric vehicle industry, the demand for lithium-ion batteries is increasing daily, leading to the problem of disposing of a large number of retired batteries. From the perspective of resource recycling and economics, the efficient recovery and direct regeneration of valuable metals (such as lithium, nickel, cobalt, and manganese) in cathode materials has become a key focus of industry research. However, during the battery dismantling and recycling process, copper (Cu) impurities from the current collector inevitably mix into the recycled cathode material black powder, becoming a key bottleneck restricting the development of direct regeneration technology.

[0003] The presence of copper particles can trigger internal short circuits, seriously threatening battery safety. Studies have shown that even copper particles as small as 20 µm can dissolve on the high-voltage side of the positive electrode during battery charging and discharging. The copper ions generated by this dissolution can penetrate the separator and migrate to the negative electrode side; subsequently, they deposit there and grow along the separator pores. Ultimately, the growth of copper dendrites connects the positive and negative electrodes, triggering an internal short circuit. Although such short circuits do not necessarily lead to thermal runaway immediately, they continuously cause battery self-discharge, capacity decay, and create long-term safety hazards. While trace doping may improve performance, it is difficult to control, and excessive doping severely degrades electrochemical performance. Some studies have indicated that under strictly controlled conditions, approximately 1% Cu doping can improve the lithium-ion diffusion coefficient and cycle stability of nickel-rich cathode materials (such as NCM811). However, in actual recycling systems, the content, distribution, and chemical state of copper impurities are uncontrollable. When the Cu content exceeds 1%, it exacerbates cation mixing, replacing Mn in the structure. 4+ and Ni 2+ This leads to decreased material structural stability, increased irreversible capacity loss, and severely impaired electrochemical performance of recycled materials.

[0004] Currently, industrial methods primarily rely on multi-stage physical sieving (such as magnetic separation and air separation) to remove copper particles from black powder. This method is inefficient and incomplete in removing micron-sized copper powder. While traditional wet acid leaching can dissolve copper, its strong acid environment simultaneously leaches valuable metals such as nickel, cobalt, and manganese, damaging the main structure of the cathode material. This prevents it from being used for high-value direct regeneration and limits its application to precursor materials for further processing. This process is lengthy, costly, and environmentally unfriendly.

[0005] Therefore, developing a direct regeneration pretreatment technology that can selectively remove copper impurities while perfectly preserving the chemical structure and valuable metals of the cathode material is of vital importance for realizing the high-value recycling and closed-loop recovery of retired lithium-ion batteries. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic processes. It utilizes the self-buffering capacity of ammonium carbonate within a specific pH range to spontaneously hydrolyze and generate ammonia-ammonium ion pairs (NH3 / NH4). + This maintains the stability of the system's pH and also represents the optimal pH window for the formation of copper-ammonia complexes. It exhibits high selectivity for copper, forming tetraamminecopper ions [Cu(NH3)4]. 2+ However, valuable metal elements such as nickel, cobalt, and manganese have slow dissolution kinetics and are difficult to form stable ammonia complexes under these conditions. Instead, they precipitate as carbonates, oxides, or hydroxides, thereby achieving efficient separation of copper from the cathode material. This method has the advantages of high copper removal efficiency, good selectivity, pH self-buffering, and environmental friendliness.

[0007] To address the aforementioned technical problems, this invention provides a method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal, comprising the following steps:

[0008] S1. Mix the retired lithium-ion battery nickel-cobalt-manganese ternary cathode material containing copper particles with ammonium carbonate;

[0009] The pH of the ammonium carbonate is 8-10, at which pH, ​​the ammonium carbonate spontaneously hydrolyzes to produce ammonia-ammonium ion pairs;

[0010] S2. Oxygen-containing gas is introduced to carry out a leaching reaction, and the synergistic effect of ammonium and dissolved oxygen is used to selectively complex copper particles in the cathode material to form soluble complex tetraammine copper ions.

[0011] S3. After the reaction, solid-liquid separation is performed to obtain the positive electrode material with copper particles removed.

[0012] This invention demonstrates that ammonium carbonate possesses self-buffering capacity within a pH range of 8-10. This buffering effect originates from the ammonia-ammonium ion pairs (NH3 / NH4) generated during the spontaneous hydrolysis of ammonium carbonate in aqueous solution. + ) and the carbonate-bicarbonate ion pair (HCO3) - / CO3 2- These two buffer pairs work together to maintain the stability of the system's pH, and also represent the optimal pH window for the formation of the copper-ammonia complex. Utilizing the synergistic effect of ammonium and oxygen, copper is oxidized to copper ions, which then form stable tetraamminecopper ions [Cu(NH3)4] with ammonia molecules. 2+ The copper complex dissolves. Meanwhile, ammonium carbonate exhibits high selectivity for copper, while valuable metals such as nickel, cobalt, and manganese are unlikely to form soluble ammonia complexes under these pH conditions. Instead, they precipitate as carbonates, oxides, or hydroxides, thus achieving efficient separation of copper from the cathode material.

[0013] This invention introduces oxygen-containing gas as an oxidant to accelerate the dissolution kinetics of metallic copper oxidation into copper ions, thereby improving copper removal efficiency, and is especially suitable for black powder with high copper content.

[0014] Furthermore, in S1, the concentration of ammonium carbonate is 0.1-2 M.

[0015] Furthermore, in S1, the solvent for the ammonium carbonate is water.

[0016] Furthermore, in S1, the solid-liquid ratio of the retired lithium-ion battery nickel-cobalt-manganese ternary cathode material mixed with ammonium carbonate is (15-35):1 g / L.

[0017] Furthermore, in S1, the mass percentage of copper particles in the retired lithium-ion battery nickel-cobalt-manganese ternary cathode material is 1-5 wt%.

[0018] Furthermore, in S2, the leaching reaction is carried out at a temperature of 25-60 °C for a time of 0.5-4 h.

[0019] Furthermore, in S2, the oxygen-containing gas is selected from air or oxygen.

[0020] Furthermore, in S3, the solid phase separation process further includes a step of washing the solid material with deionized water.

[0021] Furthermore, the removal rate of copper particles is ≥99.9%.

[0022] The beneficial effects of this invention are:

[0023] This invention utilizes the synergistic effect of ammonium and oxygen, where copper is oxidized to copper ions and forms a stable [Cu(NH3)4] with ammonia molecules in ammonium carbonate. 2+ The copper complex dissolves, while the valuable metals such as nickel, cobalt, and manganese in the cathode material are not leached out, thus achieving highly selective removal of copper.

[0024] The ammonium carbonate in this invention forms a natural pH buffer pair, which can stabilize the pH of the reaction system within the optimal range of 8 to 10. This ensures efficient complexation and dissolution of copper while maximally suppressing the volatilization of free ammonia, reducing reagent loss and environmental pollution, and making the system more stable.

[0025] This invention introduces oxygen-containing gas as an oxidant to accelerate the dissolution kinetics of metallic copper oxidation into copper ions, thereby improving copper removal efficiency, and is especially suitable for black powder with high copper content.

[0026] The cathode material after copper particle removal by the method of this invention has an intact main structure and extremely low copper content, and can directly enter the direct repair process, realizing a seamless connection from "impurity removal" to "repair", and promoting the industrialization process of closed-loop recycling of lithium-ion batteries. Attached Figure Description

[0027] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of the method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal according to the present invention;

[0029] Figure 2 This is a color change diagram of the reaction system during the reaction process in Example 1 of the present invention;

[0030] Figure 3 This is the SEM image of the positive electrode material after copper removal in Example 1 of the present invention. Figure 1 ;

[0031] Figure 4 This is the SEM image of the positive electrode material after copper removal in Example 1 of the present invention. Figure 2 ;

[0032] Figure 5 This is a comparison chart of copper removal rates under different copper solid-liquid ratios in Comparative Example 1 of the present invention.

[0033] Figure 6 This is a comparison chart of the copper removal rates under the same copper solid-liquid ratio conditions in Example 1 and Comparative Example 1 of the present invention;

[0034] Figure 7 This is a comparison chart of the copper removal rates of Comparative Examples 1-4 of the present invention under different copper solid-liquid ratio conditions;

[0035] Figure 8 This is a comparison chart of the removal rates of each component under different ammonium chloride-ammonia water volume ratios in Comparative Example 4. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Reference Figure 1 As shown, this embodiment relates to a method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal, comprising the following steps:

[0038] S1. Mix the retired lithium-ion battery nickel-cobalt-manganese ternary cathode material containing copper particles with ammonium carbonate;

[0039] Wherein, the solvent of the ammonium carbonate is water; the pH of the ammonium carbonate is 8-10, at which pH, ​​the ammonium carbonate spontaneously hydrolyzes to produce ammonia-ammonium ion pairs; the concentration of the ammonium carbonate is 0.1-2 M; the solid-liquid ratio of the retired lithium-ion battery nickel-cobalt-manganese ternary cathode material mixed with ammonium carbonate is (15-35):1 g / L.

[0040] S2. Oxygen-containing gas is introduced to carry out a leaching reaction, and the synergistic effect of ammonium and dissolved oxygen is used to selectively complex copper particles in the cathode material to form soluble complex tetraammine copper ions.

[0041] The leaching reaction is carried out at a temperature of 25-60 °C for 0.5-4 h; the oxygen-containing gas is selected from air or oxygen.

[0042] S3. After the reaction, solid-liquid separation is performed, and the solid material is washed with deionized water to obtain the positive electrode material with copper particles removed. The removal rate of copper particles is ≥99.9%.

[0043] In this embodiment, ammonium carbonate exhibits self-buffering capacity within the pH range of 8-10. This buffering effect arises from the ammonia-ammonium ion pairs (NH3 / NH4) generated during the spontaneous hydrolysis of ammonium carbonate in aqueous solution. + ) and the carbonate-bicarbonate ion pair (HCO3) - / CO3 2- These two buffer pairs work together to maintain the stability of the system's pH, and also represent the optimal pH window for the formation of the copper-ammonia complex. Utilizing the synergistic effect of ammonium and oxygen, copper is oxidized to copper ions, which then form stable tetraamminecopper ions [Cu(NH3)4] with ammonia molecules. 2+ The copper complex dissolves. Meanwhile, ammonium carbonate exhibits high selectivity for copper, while valuable metals such as nickel, cobalt, and manganese are difficult to form soluble ammonia complexes under these pH conditions, instead precipitating as carbonates, oxides, or hydroxides. This achieves efficient separation of copper from the cathode material. The introduction of oxygen-containing gas acts as an oxidant, accelerating the dissolution kinetics of metallic copper oxidation to copper ions, thereby improving copper removal efficiency, especially suitable for black powder with high copper content.

[0044] Preferably, in S1, the mass percentage of copper particles in the retired lithium-ion battery nickel-cobalt-manganese ternary cathode material is 1-5 wt%.

[0045] Example 1

[0046] This embodiment relates to a method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal, including the following steps:

[0047] (1) Weigh 0.5 g of retired NCM523 (lithium nickel cobalt manganese oxide) cathode material black powder containing copper particles (Cu content is about 5 wt%), place it in a 50 mL glass bottle, and add 20 mL of ammonium carbonate solution (ammonium carbonate concentration 0.1 M, pH=9.2, copper particles to solution solid-liquid ratio is 1.25 g / L).

[0048] (2) Place the glass bottle in a 50 ℃ oil bath under an oxygen atmosphere, turn on the mechanical stirrer, and carry out the leaching reaction. After reacting for 2.5 hours, filter and collect the leachate. (Reference) Figure 2 During the reaction, the solution color can be observed to gradually change from light blue to dark blue, indicating that copper ions dissolve by forming a copper-ammonia complex with ammonia.

[0049] (3) After the reaction is completed, the solid powder is centrifuged, washed three times with deionized water, and dried in a vacuum drying oven at 80 °C for 6 hours to obtain the positive electrode material after copper removal.

[0050] Scanning electron microscopy (SEM) characterization of the NCM523 cathode material treated with ammonium carbonate showed that the surface morphology was intact and no obvious defects were observed, indicating that the ammonium carbonate solution did not damage the structure of the cathode material. Figure 3 , 4 ).

[0051] According to ICP-MS testing, the removal rate of copper under these conditions reached 99.9%, while the loss rates of nickel, cobalt, and manganese were all less than 0.1%.

[0052] Example 2

[0053] This embodiment relates to a method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal, including the following steps:

[0054] (1) Weigh 0.5 g of retired NCM523 (lithium nickel cobalt manganese oxide) cathode material black powder containing copper particles (Cu content is about 3 wt%), place it in a 50 mL glass bottle, and add 20 mL of ammonium carbonate solution (ammonium carbonate concentration 0.1 M).

[0055] (2) Place the glass bottle in a 50 °C oil bath and, under an oxygen atmosphere, turn on the mechanical stirring to carry out the leaching reaction. After 2.5 hours of reaction, filter and collect the leaching liquid.

[0056] (3) After the reaction is completed, the solid powder is centrifuged, washed three times with deionized water, and dried in a vacuum drying oven at 80 °C for 6 hours to obtain the positive electrode material after copper removal.

[0057] According to ICP-MS testing, the removal rate of copper under these conditions reached 99.9%, while the loss rates of nickel, cobalt, and manganese were all less than 0.1%.

[0058] Comparative Example 1

[0059] The difference between this comparative example and Example 1 is that the leaching reaction atmosphere is air; specifically, it includes the following steps:

[0060] (1) Weigh 0.5 g of retired NCM523 (lithium nickel cobalt manganese oxide) cathode material black powder containing copper particles (Cu content of 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%), place it in a 50 mL glass bottle, and add 20 mL of ammonium carbonate solution (ammonium carbonate concentration 0.1 M), wherein the copper solid-liquid ratio in the ammonium carbonate solution is 0.25 g / L, 0.5 g / L, 0.75 g / L, 1 g / L, 1.25 g / L.

[0061] (2) Place the glass bottle in a 50 ℃ oil bath, and under air atmosphere, turn on the mechanical stirring to carry out the leaching reaction. After reacting for 2.5 hours, filter and collect the leaching liquid.

[0062] (3) After the reaction is completed, the solid powder is centrifuged, washed three times with deionized water, and dried in a vacuum drying oven at 80 °C for 6 hours to obtain the positive electrode material after copper removal.

[0063] ICP-MS testing showed that the removal rates of copper with different solid-liquid ratios under these conditions were as follows: Figure 5 (Horizontal axis: copper solid-liquid ratio) As shown, when the copper solid-liquid ratio is above 1 g / L, the copper removal rate decreases significantly. Specifically, under the same copper solid-liquid ratio (1.25 g / L) as Example 1, the copper removal rate is 96.8%. A comparison of the two is shown in the graph below. Figure 6 As shown.

[0064] Comparative Example 2

[0065] The difference between this comparative example and Comparative Example 1 is that the ammonium carbonate solution is replaced with a 0.2 M ammonium chloride solution; specifically, the steps are as follows:

[0066] (1) Weigh 0.5 g of retired NCM523 (lithium nickel cobalt manganese oxide) cathode material black powder containing copper particles (Cu content is about 5 wt%), place it in a 50 mL glass bottle, and add 20 mL of ammonium chloride solution (ammonium chloride concentration 0.2 M).

[0067] (2) Place the glass bottle in a 50°C oil bath and, under an air atmosphere, turn on the mechanical stirrer to carry out the leaching reaction. After 2.5 hours of reaction, filter and collect the leaching liquid.

[0068] (3) After the reaction is completed, the solid powder is centrifuged, washed three times with deionized water, and dried in a vacuum drying oven at 80 °C for 6 hours to obtain the positive electrode material after copper removal.

[0069] According to ICP-MS testing, the copper removal rate under these conditions was only 1.14%.

[0070] Comparative Example 3

[0071] The difference between this comparative example and Comparative Example 1 is that the ammonium carbonate solution is replaced with a 0.2 M ammonia solution; specifically, the steps are as follows:

[0072] (1) Weigh 0.5 g of retired NCM523 (lithium nickel cobalt manganese oxide) cathode material black powder containing copper particles (Cu content is about 5 wt%), place it in a 50 mL glass bottle, and add 20 mL of ammonia solution (ammonia concentration 0.2 M).

[0073] (2) Place the glass bottle in a 50 ℃ oil bath, and under air atmosphere, turn on the mechanical stirring to carry out the leaching reaction. After reacting for 2.5 hours, filter and collect the leaching liquid.

[0074] (3) After the reaction is completed, the solid powder is centrifuged, washed three times with deionized water, and dried in a vacuum drying oven at 80 °C for 6 hours to obtain the positive electrode material after copper removal.

[0075] According to ICP-MS testing, the copper removal rate under these conditions was only 1.2%.

[0076] Comparative Example 4

[0077] The difference between this comparative example and Comparative Example 1 is that the ammonium carbonate solution is replaced with a mixed solution of ammonium chloride and ammonia (the volume ratio of ammonium chloride to ammonia is 1:1, the concentration of ammonium chloride is 0.2 M, and the concentration of ammonia is 0.2 M); specifically, the following steps are included:

[0078] (1) Weigh 0.5 g of retired NCM523 (lithium nickel cobalt manganese oxide) cathode material black powder containing copper particles (Cu content is about 5 wt%), place it in a 50 mL glass bottle, and add 20 mL of ammonium chloride-ammonia water mixed solution (ammonium chloride-ammonia water volume ratio is 1:1, ammonium chloride concentration is 0.2 M, ammonia water concentration is 0.2 M).

[0079] (2) Place the glass bottle in a 50 ℃ oil bath, and under air atmosphere, turn on the mechanical stirring to carry out the leaching reaction. After reacting for 2.5 hours, filter and collect the leaching liquid.

[0080] (3) After the reaction is completed, the solid powder is centrifuged, washed three times with deionized water, and dried in a vacuum drying oven at 80 °C for 6 hours to obtain the positive electrode material after copper removal.

[0081] According to ICP-MS testing, the removal rate of copper under these conditions was only 29.74%, while the total loss rate of nickel, cobalt, and manganese was greater than 1%.

[0082] Referring to Comparative Example 1, the copper content in Comparative Examples 2-4 was adjusted to achieve copper solid-liquid ratios of 0.25 g / L, 0.5 g / L, 0.75 g / L, 1 g / L, and 1.25 g / L, respectively. ICP-MS analysis was then performed, and the results are as follows: Figure 7 As shown, the copper removal rate gradually decreases with the increase of the copper solid-liquid ratio.

[0083] Furthermore, the volume ratio of ammonium chloride to ammonia in Comparative Example 4 was adjusted to 1:0.5 and 1:3, respectively, and ICP-MS testing was performed. The results are as follows: Figure 8 As shown, the removal rate of copper further decreased after adjusting the volume ratio, and the total loss rate of nickel, cobalt and manganese further increased when the volume ratio of ammonium chloride to ammonia was 1:0.5.

[0084] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal, characterized in that, Includes the following steps: S1. Mix the retired lithium-ion battery nickel-cobalt-manganese ternary cathode material containing copper particles with ammonium carbonate; Among them, ammonium carbonate spontaneously hydrolyzes to produce ammonia-ammonium ion pairs; S2. Oxygen-containing gas is introduced to carry out a leaching reaction, and the synergistic effect of ammonium and dissolved oxygen is used to selectively complex copper particles in the cathode material to form soluble complex tetraammine copper ions. S3. After the reaction, solid-liquid separation is performed to obtain the positive electrode material with copper particles removed.

2. The method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal as described in claim 1, characterized in that, In S1, the concentration of ammonium carbonate is 0.1-2 M.

3. The method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal as described in claim 1, characterized in that, In S1, the pH of the ammonium carbonate is 8-10.

4. The method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal as described in claim 1, characterized in that, In S1, the solvent for the ammonium carbonate is water.

5. The method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal as described in claim 1, characterized in that, In S1, the solid-liquid ratio of the retired lithium-ion battery nickel-cobalt-manganese ternary cathode material mixed with ammonium carbonate is (15-35):1 g / L.

6. The method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal as described in claim 1, characterized in that, In S1, the mass percentage of copper particles in the retired lithium-ion battery nickel-cobalt-manganese ternary cathode material is 1-5 wt%.

7. The method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal as described in claim 1, characterized in that, In S2, the leaching reaction is carried out at a temperature of 25-60 °C for a time of 0.5-4 h.

8. The method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal as described in claim 1, characterized in that, In S2, the oxygen-containing gas is selected from air or oxygen.

9. The method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal as described in claim 1, characterized in that, In step S3, the solid phase separation process further includes a step of washing the solid material with deionized water.

10. The method for removing copper particles from lithium-ion battery cathode materials based on ammonium-oxygen synergistic removal as described in claim 1, characterized in that, Copper particle removal rate ≥99.9%.

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