Method for recovering cathode copper foil of waste lithium ion battery

Abstract

The invention provides a waste lithium ion battery negative electrode copper foil recovery method, which comprises: crushing a negative electrode material to a particle size of less than or equal to 5 mm, carrying out room temperature pretreatment with 1-5% dilute sulfuric acid for 0.5-2 h, and separating to obtain a pretreated copper foil; then hydrogen peroxide or glucose is used as a reducing agent, reduction acid leaching is carried out under the conditions of specific concentration sulfuric acid, temperature, time and solid-to-liquid ratio, and copper-containing filtrate and carbon-containing filter residues are separated out; and immersing the copper foil into a sodium sulfite (0.4-0.6 M)-hydrochloric acid (pH = 2.0-3.0) solution containing the auxiliary agent, carrying out magnetic field stirring reaction at room temperature for 4-6 hours, filtering, and adding iron powder to reduce copper ions, so that efficient recovery of the copper foil and deep removal of impurities are realized, and the process is environment-friendly and efficient.

Description

Technical Field

[0001] This invention relates to the field of resource utilization of waste lithium-ion batteries, specifically to a method for recycling copper foil from the negative electrode of waste lithium-ion batteries. Background Technology

[0002] With the widespread application of lithium-ion batteries in electric vehicles, portable electronic devices, and other fields, the recycling of spent lithium-ion batteries has become an important issue. The negative electrode material, as a key component of the battery, typically consists of copper foil current collectors and graphite / silicon-based active materials. Copper foil (purity ≥99.5%) accounts for 30%–50% of the negative electrode material's mass and has high recycling value.

[0003] Traditional recycling methods primarily employ pyrometallurgical or mechanical-physical methods, but these suffer from high energy consumption, low recovery rates, and insufficient purity. For example, pyrometallurgical processes require high-temperature treatment, which easily leads to copper oxidation loss; mechanical stripping methods struggle to completely separate copper foil from active materials, and the recovered copper foil has low purity (containing impurities such as carbon and lithium), making it unsuitable for direct use in battery production. Furthermore, some wet processes use strong acids (such as nitric acid) to directly dissolve the copper foil, followed by electrodeposition for recovery, but these methods suffer from nitrogen oxide pollution, high energy consumption, and severe equipment corrosion. Therefore, developing a method that can efficiently recover high-purity copper foil while also being environmentally friendly and economical is of significant practical necessity. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recycling copper foil from the negative electrode of waste lithium-ion batteries. Through the synergistic effect of reducing acid leaching, alkaline leaching and chemical deposition, selective recycling and deep purification of copper foil can be achieved.

[0005] The technical solution of this invention is: a method for recycling copper foil from the negative electrode of waste lithium-ion batteries, characterized by comprising the following steps:

[0006] Raw material pretreatment

[0007] Waste negative electrode material is crushed to a particle size of ≤5mm to obtain crushed material.

[0008] The crushed material was pretreated with dilute sulfuric acid, stirred at room temperature for a period of time, and then filtered to obtain pretreated copper foil.

[0009] Reduction acid leaching

[0010] The pretreated copper foil was added to a dilute sulfuric acid solution containing a reducing agent, such as hydrogen peroxide or glucose, for reducing acid leaching. The sulfuric acid concentration was controlled. Then, a sodium sulfite-hydrochloric acid solution containing the auxiliary agent was added. The reaction was carried out under magnetic stirring at room temperature. After filtration, iron powder was added to reduce the copper ions. The copper-containing filtrate and carbon-containing filter residue were obtained by filtration separation.

[0011] Calculate copper leaching rate

[0012] The concentrations of various metal ions in the leachate were determined using inductively coupled plasma optical emission spectrometry (ICP-OES), and the leaching rate was calculated using the following formula: Where C is the concentration of metal ions in the leachate (mg / L), V is the volume of the leachate (L), M is the molar mass of the metal (g / mol), m is the mass of the cathode powder (g), and w is the mass fraction of the metal in the cathode (%).

[0013] As a preferred embodiment of the present invention, the waste negative electrode material is a negative electrode sheet obtained from the dismantling of a lithium-ion battery, and an oxide layer exists on the surface of the copper foil, with XPS analysis showing Cu... 2+ / Cu 0 The ratio is 0.1-0.3.

[0014] As a preferred embodiment of the present invention, the crushing step is characterized by using a jaw crusher with a crushing ratio of 1:5-1:15 and a particle size of 2-5mm after crushing.

[0015] As a preferred embodiment of the present invention, the pretreatment step is characterized in that the mass fraction of dilute sulfuric acid is 3%-5%, the stirring speed is 250-350 r / min, the leaching time is 0.5-1.5 h, and the pH of the solution after the reaction is completed is 2.0-3.0.

[0016] As a preferred embodiment of the present invention, the characteristic is that, in the reduction acid leaching step, when the reducing agent is hydrogen peroxide, its addition amount is 1.0-1.1 times the theoretical amount, and the dropping rate is 0.5-2 mL / min; when the reducing agent is glucose, its addition amount is 1.05-1.2 times the theoretical amount, and the glucose is added in solid form all at once.

[0017] As a preferred embodiment of the present invention, the sulfuric acid concentration in the reduction acid leaching step is 1.0-1.5 mol / L, the temperature is 50-60℃, the reaction time is 1.5-2.5 h, the solid-liquid ratio is 1:8-1:12, and the stirring speed is 350-450 r / min.

[0018] As a preferred embodiment of the present invention, the method for preparing the auxiliary agent is characterized in that:

[0019] Under weakly alkaline conditions (pH 8.0-9.0) adjusted with potassium hydroxide, 10-14 parts by mass of vinyl-β-aminoethanethiol, 8-11 parts by mass of crotonic acid, and 4-7 parts by mass of 5-bromo-2-fluorophenylboronic acid were dissolved in tetrahydrofuran (the solvent volume was 1.5 times the total mass of the reactants), and reacted at 50-70°C for 4-6 hours. After the reaction, THF was removed by purging with nitrogen to obtain a liquid thiocarboxylic acid derivative with a number average molecular weight of 2500-4000.

[0020] As a preferred embodiment of the present invention, the pretreated copper foil obtained in the pretreatment step has a lithium removal rate of ≥95% and a removal rate of metal impurities such as iron, aluminum, and manganese of ≥60%; the copper-containing filtrate obtained in the reduction acid leaching step has a copper leaching rate of ≥95% and a carbon leaching rate of ≤0.5%.

[0021] As a preferred embodiment of the present invention, the method further includes a step of removing impurities from the copper-containing filtrate: adding a sodium hydroxide solution with a mass fraction of 5%-10% to the copper-containing filtrate, adjusting the pH to 4.0-5.5, so that metal impurities such as iron, aluminum, and manganese precipitate in the form of hydroxides, and filtering to obtain a copper solution after impurity removal, wherein the residual amounts of iron, aluminum, and manganese are all ≤0.01g / L.

[0022] I. Reaction Mechanism

[0023] 1. Thiol-boronic acid co-addition: The borate group of 5-bromo-2-fluorophenylboronic acid undergoes electrophilic addition to the double bond of crotonic acid, while the thiol group of vinyl-β-aminoethanethiol undergoes nucleophilic attack, forming a bifunctional molecule containing CS and CB bonds, with the bromofluorophenyl ring providing steric hindrance.

[0024] 2. Dual-coordination stabilized copper ions: thiol S atom and Cu 2+ Formation of coordinate bonds, boron-oxygen bonds (BO - ) and Cu 2+ Hydrated ions form hydrogen bonds, generating the [Cu(SR)(B(OH)2)]+ complex ion, which inhibits the formation of CuS precipitate and stabilizes Cu in the solution. 2+ concentration.

[0025] II. Technical Effects

[0026] 1. Reduction efficiency and product purity: Iron powder reduction of Cu 2+ Efficiency increased from 90% to 95%, copper powder purity ≥99%, and reaction time shortened by 25%; steric hindrance of the bromofluorobenzene ring improved Cu 2+ The complex ion is stable at pH 2.5.

[0027] 2. Solvent removal and process adaptation: After nitrogen purging, the residual THF content is <0.5%, the product viscosity is <50 mPa·s, and it is compatible with automated pipeline transportation, reducing dissolution time by 50%. Detailed Implementation

[0028] The present invention will be described in detail below with reference to specific embodiments.

[0029] Example 1

[0030] 1. A method for the efficient recycling and purification of copper foil from waste lithium-ion batteries, characterized by comprising the following steps:

[0031] Example 1:

[0032] Raw material pretreatment

[0033] 100g of waste lithium-ion battery negative electrode material was taken and crushed to a particle size ≤3mm (using a jaw crusher, crushing ratio 1:10). 500mL of 3% (w / w) dilute sulfuric acid was added, and the mixture was stirred at 300r / min for 1h at room temperature. During the reaction, a small amount of bubbles were observed to be generated, and the solution pH gradually increased from the initial 1.2 to 2.5. After the reaction was completed, vacuum filtration was used to obtain pretreated copper foil (wet weight approximately 98.5g) and pretreated filtrate (pale blue, containing Li). + Fe 2+ Al 3 + cations).

[0034] Reduction acid leaching

[0035] The pretreated copper foil was transferred to a 1000 mL three-necked flask, and 700 mL of 1.0 mol / L dilute sulfuric acid solution (prepared by diluting 98% concentrated sulfuric acid) was added. 20 mL of 30% hydrogen peroxide was slowly added dropwise as a reducing agent, controlling the dropping rate at 1 mL / min. Simultaneously, the three-necked flask was placed in a water bath at 50 ± 2 °C, and the reaction was stirred at 400 rpm for 2 hours. Then, a sodium sulfite (0.4 M)-hydrochloric acid (pH = 2.0) solution containing the aforementioned auxiliary agent was added, and the reaction was stirred under a magnetic field for 4 hours. After filtration, iron powder was added to reduce the copper ions. Initially, the solution gradually turned blue (Cu... 2+ The reaction produces a characteristic color and releases a small amount of heat (ΔT≈5℃). In the later stages of the reaction, the solution color stabilizes and no obvious bubbles are produced, indicating that the copper foil dissolution reaction is basically complete. After the reaction is complete, the solution is filtered while hot (using a heat-insulated funnel to avoid copper sulfate crystallization) to obtain a copper-containing filtrate (a light blue clear liquid, approximately 750 mL in volume) and a carbon-containing filter residue (a black solid, approximately 40.2 g wet weight).

[0036] The preparation method of the auxiliary agent is as follows:

[0037] Under weakly alkaline conditions (pH 8.0) adjusted with potassium hydroxide, 10 g of vinyl-β-aminoethanethiol, 8 g of crotonic acid, and 4 g of 5-bromo-2-fluorophenylboronic acid were dissolved in tetrahydrofuran (the solvent volume was 1.5 times the total mass of the reactants), and the mixture was reacted at 50 °C for 4 hours. After the reaction, THF was removed by purging with nitrogen to obtain liquid thiocarboxylic acid derivatives with a number average molecular weight of 2500-4000.

[0038] Calculate copper leaching rate

[0039] The copper leaching rate of the above copper-containing filtrate was calculated to be 96.0%.

[0040] Example 2:

[0041] A highly efficient method for recycling and purifying copper foil from waste lithium-ion batteries, characterized by the following steps:

[0042] Raw material pretreatment

[0043] Take 100g of waste lithium-ion battery negative electrode material, crush it to a particle size ≤5mm, add 800mL of 5% (w / w) dilute sulfuric acid, and stir at 350r / min for 0.5h at room temperature (25±2℃). During the reaction, obvious bubble generation was observed, and the solution pH gradually increased from the initial 1.0 to 2.2. After the reaction was completed, vacuum filtration was performed to obtain pretreated copper foil (wet weight approximately 97.8g) and pretreated filtrate (pale blue).

[0044] Reduction acid leaching

[0045] Transfer the pretreated copper foil to a 1500mL three-necked flask, add 1.5mol / L dilute sulfuric acid solution (1000mL), and add 15g of glucose (C6H4O2). 12 O6 (analytical grade, used as a reducing agent) was added, and the reaction was carried out at 60±2℃ with stirring at 450 r / min for 1.5 h. Then, a sodium sulfite (0.5 M)-hydrochloric acid (pH = 2.5) solution containing the aforementioned auxiliary agent was added, and the reaction was stirred under a magnetic field for 5 hours. After filtration, iron powder was added to reduce copper ions. In the initial stage of the reaction, the solution gradually turned blue, accompanied by a small amount of heat release (ΔT≈8℃); in the later stage of the reaction, the solution color stabilized, and no obvious bubbles were produced. After the reaction was completed, the solution was filtered while hot to obtain a copper-containing filtrate (a pale blue clear liquid, approximately 1050 mL in volume) and a carbon-containing filter residue (a black solid, approximately 35.1 g wet weight).

[0046] The preparation method of the auxiliary agent is as follows:

[0047] Under weakly alkaline conditions (pH 8.5) adjusted with potassium hydroxide, 12 g of vinyl-β-aminoethanethiol, 9.5 g of crotonic acid, and 5.5 g of 5-bromo-2-fluorophenylboronic acid were dissolved in tetrahydrofuran (solvent volume was 1.5 times the total mass of reactants), and reacted at 60 °C for 5 hours. After the reaction, THF was removed by nitrogen purging to obtain liquid thiocarboxylic acid derivatives with a number average molecular weight of 2500-4000.

[0048] Calculate copper leaching rate

[0049] The copper leaching rate of the above copper-containing filtrate was calculated to be 97.5%.

[0050] Example 3:

[0051] A highly efficient method for recycling and purifying copper foil from waste lithium-ion batteries, characterized by the following steps:

[0052] Raw material pretreatment

[0053] Take 100g of waste lithium-ion battery negative electrode material, crush the material to a particle size ≤2mm, add 600mL of 1% (w / w) dilute sulfuric acid, and stir at 250r / min for 2h at room temperature (25±2℃). During the reaction, a small amount of bubbles were observed to be generated, and the pH of the solution gradually increased from the initial 1.5 to 3.0. After the reaction was completed, vacuum filtration was performed to obtain pretreated copper foil (wet weight approximately 99.2g) and pretreated filtrate (light blue).

[0054] Reduction acid leaching

[0055] The pretreated copper foil was transferred to a 1200 mL three-necked flask, and 800 mL of 0.5 mol / L dilute sulfuric acid solution was added. 15 mL of 30% hydrogen peroxide was slowly added dropwise, and the temperature was controlled at 40 ± 2 °C. The mixture was stirred at 350 rpm for 3 h. Then, a sodium sulfite (0.6 M)-hydrochloric acid (pH = 3.0) solution containing the aforementioned additive was added, and the mixture was stirred under a magnetic field for 6 h. After filtration, iron powder was added to reduce the copper ions. Initially, the solution gradually turned blue; later, the solution color stabilized, and no obvious bubbles were produced. After the reaction was complete, the mixture was filtered while hot to obtain a copper-containing filtrate (a pale blue clear liquid, approximately 820 mL in volume) and a carbon-containing filter residue (a black solid, approximately 42.5 g wet weight).

[0056] The preparation method of the auxiliary agent is as follows:

[0057] Under weakly alkaline conditions (pH 9.0) adjusted with potassium hydroxide, 14 g of vinyl-β-aminoethanethiol, 11 g of crotonic acid, and 7 g of 5-bromo-2-fluorophenylboronic acid were dissolved in tetrahydrofuran (solvent volume was 1.5 times the total mass of reactants), and reacted at 70°C for 6 hours. After the reaction, THF was removed by nitrogen purging to obtain liquid thiocarboxylic acid derivatives with a number average molecular weight of 2500-4000.

[0058] Calculate copper leaching rate

[0059] The copper-containing filtrate was taken from the above solution, and the copper leaching rate was calculated to be 99%.

[0060] Comparative Example 1:

[0061] A highly efficient method for recycling and purifying copper foil from waste lithium-ion batteries, characterized by the following steps:

[0062] Raw material pretreatment

[0063] 100g of waste lithium-ion battery negative electrode material was taken and crushed to a particle size ≤3mm (using a jaw crusher, crushing ratio 1:10). 500mL of 3% (w / w) dilute sulfuric acid was added, and the mixture was stirred at 300r / min for 1h at room temperature. During the reaction, a small amount of bubbles were observed to be generated, and the solution pH gradually increased from the initial 1.2 to 2.5. After the reaction was completed, vacuum filtration was used to obtain pretreated copper foil (wet weight approximately 98.5g) and pretreated filtrate (pale blue, containing Li). + Fe 2+ Al 3 + cations).

[0064] Reduction acid leaching

[0065] The pretreated copper foil was transferred to a 1000 mL three-necked flask, and 700 mL of 1.0 mol / L dilute sulfuric acid solution (prepared by diluting 98% concentrated sulfuric acid) was added. 20 mL of 30% hydrogen peroxide was slowly added dropwise as a reducing agent at a rate of 1 mL / min. Simultaneously, the three-necked flask was placed in a water bath at 50 ± 2 °C, and the mixture was stirred at 400 rpm for 2 hours. Initially, the solution gradually turned blue (Cu...). 2+ The reaction produces a characteristic color and releases a small amount of heat (ΔT≈5℃). In the later stages of the reaction, the solution color stabilizes and no obvious bubbles are produced, indicating that the copper foil dissolution reaction is basically complete. After the reaction is complete, the solution is filtered while hot (using a heat-insulated funnel to avoid copper sulfate crystallization) to obtain a copper-containing filtrate (a light blue clear liquid, approximately 750 mL in volume) and a carbon-containing filter residue (a black solid, approximately 40.2 g wet weight).

[0066] Calculate copper leaching rate

[0067] The copper leaching rate of the above copper-containing filtrate was calculated to be 85.0%.

[0068] Comparative Example 2:

[0069] A highly efficient method for recycling and purifying copper foil from waste lithium-ion batteries, characterized by the following steps:

[0070] Raw material pretreatment

[0071] Take 100g of waste lithium-ion battery negative electrode material, crush it to a particle size ≤5mm, add 800mL of 5% (w / w) dilute sulfuric acid, and stir at 350r / min for 0.5h at room temperature (25±2℃). During the reaction, obvious bubble generation was observed, and the solution pH gradually increased from the initial 1.0 to 2.2. After the reaction was completed, vacuum filtration was performed to obtain pretreated copper foil (wet weight approximately 97.8g) and pretreated filtrate (pale blue).

[0072] Reduction acid leaching

[0073] Transfer the pretreated copper foil to a 1500mL three-necked flask, add 1.5mol / L dilute sulfuric acid solution (1000mL), and add 15g of glucose (C6H4O2). 12 O6 (analytical grade, used as a reducing agent) was used to react the solution at a controlled temperature of 60±2℃ with stirring at 450 r / min for 1.5 h. Initially, the solution gradually turned blue, accompanied by a small amount of heat release (ΔT≈8℃); later, the solution color stabilized, and no obvious bubbles were generated. After the reaction was complete, the solution was filtered while hot to obtain a copper-containing filtrate (a pale blue, clear liquid, approximately 1050 mL in volume) and a carbon-containing filter residue (a black solid, approximately 35.1 g wet weight).

[0074] Calculate copper leaching rate

[0075] The copper-containing filtrate was taken from the above solution, and the copper leaching rate was calculated to be 89%.

[0076] Compared to traditional methods for recycling copper foil from waste lithium-ion batteries, the recycling method of this invention achieves a higher copper leaching rate and product purity, with a copper leaching rate ≥95%. Due to the use of a specially prepared liquid thiocarboxylic acid derivative as an additive, its thiol S atom can synergistically coordinate with the boron-oxygen bond to copper ions, generating a stable complex ion that inhibits CuS precipitation. Simultaneously, combined with reducing acid leaching and magnetic field stirring, the dissolution and separation of copper are accelerated, achieving highly efficient recycling and deep purification of copper foil. The process is environmentally friendly and suitable for automated production.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recycling copper foil from the negative electrode of waste lithium-ion batteries, characterized in that, Includes the following steps: Raw material pretreatment Waste negative electrode materials are crushed to a particle size of ≤5mm to obtain crushed material; The crushed material was pretreated with dilute sulfuric acid, stirred at room temperature for a period of time, and then filtered to obtain pretreated copper foil. Reduction acid leaching The pretreated copper foil was added to a dilute sulfuric acid solution containing a reducing agent, such as hydrogen peroxide or glucose, for reducing acid leaching. The sulfuric acid concentration was controlled. Then, a sodium sulfite-hydrochloric acid solution containing the auxiliary agent was added. The reaction was carried out under magnetic stirring at room temperature. After filtration, iron powder was added to reduce the copper ions. The copper-containing filtrate and carbon-containing filter residue were obtained by filtration separation. Calculate copper leaching rate The concentrations of various metal ions in the leachate were determined using inductively coupled plasma optical emission spectrometry (ICP-OES), and the leaching rate was calculated using the following formula: Where C is the concentration of metal ions in the leachate (mg / L), V is the volume of the leachate (L), M is the molar mass of the metal (g / mol), m is the mass of the cathode powder (g), and w is the mass fraction of the metal in the cathode (%).

2. The method for recycling waste lithium-ion battery negative electrode copper foil according to claim 1, characterized in that, The waste negative electrode material is a negative electrode sheet obtained from the dismantling of lithium-ion batteries. An oxide layer exists on the surface of the copper foil, and XPS analysis shows that Cu... 2+ / Cu 0 The ratio is 0.1-0.

3.

3. The method for recycling waste lithium-ion battery negative electrode copper foil according to claim 1, characterized in that, The crushing step uses a jaw crusher with a crushing ratio of 1:5-1:15, and the particle size after crushing is 2-5mm.

4. The method for recycling waste lithium-ion battery negative electrode copper foil according to claim 1, characterized in that, In the pretreatment step, the mass fraction of dilute sulfuric acid is 3%-5%, the stirring speed is 250-350 r / min, the leaching time is 0.5-1.5 h, and the pH of the solution after the reaction is completed is 2.0-3.

0.

5. The method for recycling waste lithium-ion battery negative electrode copper foil according to claim 1, characterized in that, In the reduction leaching step, when the reducing agent is hydrogen peroxide, its addition amount is 1.0-1.1 times the theoretical amount, and the dropping rate is 0.5-2 mL / min; when the reducing agent is glucose, its addition amount is 1.05-1.2 times the theoretical amount, and the glucose is added in solid form all at once.

6. The method for recycling waste lithium-ion battery negative electrode copper foil according to claim 1, characterized in that, In the reduction acid leaching step, the sulfuric acid concentration is 1.0-1.5 mol / L, the temperature is 50-60℃, the reaction time is 1.5-2.5 h, the solid-liquid ratio is 1:8-1:12, and the stirring speed is 350-450 r / min.

7. The method for recycling waste lithium-ion battery negative electrode copper foil according to claim 1, characterized in that, The preparation method of the auxiliary agent: Under weakly alkaline conditions (pH 8.0-9.0) adjusted with potassium hydroxide, 10-14 parts by mass of vinyl-β-aminoethanethiol, 8-11 parts by mass of crotonic acid, and 4-7 parts by mass of 5-bromo-2-fluorophenylboronic acid were dissolved in tetrahydrofuran (the solvent volume was 1.5 times the total mass of the reactants), and reacted at 50-70°C for 4-6 hours. After the reaction, THF was removed by purging with nitrogen to obtain a liquid thiocarboxylic acid derivative with a number average molecular weight of 2500-4000.

8. A method for recycling waste lithium-ion battery negative electrode copper foil according to claim 1, characterized in that, In the pretreated copper foil obtained by the pretreatment step, the removal rate of lithium element is ≥95%, and the removal rate of metal impurities such as iron, aluminum, and manganese is ≥60%; in the copper-containing filtrate obtained by the reduction acid leaching step, the copper leaching rate is ≥95%, and the carbon leaching rate is ≤0.5%.

9. A method for recycling waste lithium-ion battery negative electrode copper foil according to claim 1, characterized in that, The method also includes a step of removing impurities from the copper-containing filtrate: adding a sodium hydroxide solution with a mass fraction of 5%-10% to the copper-containing filtrate, adjusting the pH to 4.0-5.5, so that metal impurities such as iron, aluminum, and manganese precipitate in the form of hydroxides, and filtering to obtain a copper solution after impurity removal, wherein the residual amounts of iron, aluminum, and manganese are all ≤0.01g / L.

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