Method for recycling lithium and copper of negative electrode of lithium ion battery

Abstract

The invention discloses a method for recycling lithium and copper of a negative electrode of a lithium ion battery, and relates to the technical field of recycling of a negative electrode piece of the lithium ion battery. The method comprises the following steps: disassembling the lithium ion battery and separating a pole piece to obtain a negative pole; the negative electrode is subjected to supercritical CO2 extraction, so that a negative electrode material and the copper foil are stripped, and solid residues containing graphite, the copper foil and lithium powder are obtained; dilute acid is added into the solid residues for dissolution, and a mixed solution containing copper and lithium ions is obtained through separation; an electrolyte is added into a mixed solution containing copper and lithium ions, selective reduction of the lithium ions and the copper ions is carried out through electrochemical deposition, and copper and lithium are obtained. By adopting the method disclosed by the invention, the lithium element and the copper element of the lithium ion battery negative plate can be effectively recycled, the finally obtained product has a remarkable additional value, and the benefit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling negative electrode sheets of lithium-ion batteries, and in particular to a method for collaboratively recycling copper and lithium from negative electrodes of lithium-ion batteries. Background Art

[0002] Under the carbon neutrality and new energy policies, the rapid rise of new energy vehicles and energy storage industries has stimulated the rapid development of the lithium-ion battery industry, thereby prompting lithium-ion batteries to shift towards high safety, high energy density and long cycle life. As an important component of lithium-ion batteries, negative electrode materials contain abundant lithium and copper resources. At present, there is no prescribed treatment method for negative electrode sheets in battery cells, especially lithium-embedded negative electrode sheets, which leads to fires caused by untimely treatment of negative electrode sheets. Most companies use spray incineration methods, but there is no effective treatment method for lithium and copper, resulting in waste of resources and environmental pollution. Traditional negative electrode material recycling methods have problems such as complex process flow, serious environmental pollution, and low metal recovery rate. For example, pyrometallurgical recovery has high energy consumption and produces harmful gases, and hydrometallurgical recovery has a long process and produces a large amount of wastewater. Therefore, it is urgent to develop a green, efficient, and simple process flow lithium-ion battery negative electrode recovery method to avoid environmental pollution while realizing the recovery and utilization of resources (lithium and copper), which has significant environmental and economic benefits. Summary of the invention

[0003] The present invention provides a method for collaboratively recovering copper and lithium from negative electrodes of lithium-ion batteries, so as to solve the problem that the negative electrode sheets produced by disassembling batteries (0-100% SOC) during the development and circulation of existing lithium-ion batteries are flammable and contain valuable metal elements such as lithium and copper, while most of the negative electrode sheets are incinerated, resulting in environmental pollution and waste of resources. The method of the present invention can effectively recover the lithium and copper elements of the negative electrode sheets of lithium-ion batteries, and the final product has significant added value and improves efficiency.

[0004] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0005] The present invention provides a method for recovering lithium and copper from a negative electrode of a lithium-ion battery, comprising the following steps:

[0006] S1. Disassemble the lithium-ion battery and separate the pole pieces to obtain the negative electrode; extract the negative electrode by supercritical CO2 to peel off the negative electrode material and copper foil, and separate the solid residue containing graphite, copper foil and lithium powder;

[0007] S2, adding dilute acid to the solid residue of step S1 to dissolve it, and separating to obtain a mixed solution containing copper and lithium ions;

[0008] S3, adding an electrolyte to the mixed solution containing copper and lithium ions in step S2, and selectively reducing lithium ions and copper ions by electrochemical deposition to obtain copper and lithium.

[0009] The following is a detailed description:

[0010] Step S1:

[0011] The lithium-ion battery is disassembled and separated in the disassembly room to obtain the negative electrode.

[0012] The lithium-ion battery may be one or more of a ternary lithium battery, a lithium cobalt oxide battery, a lithium nickel oxide battery, a lithium manganese oxide battery and a lithium iron phosphate battery;

[0013] The lithium-ion battery can be divided into square, cylindrical and soft pack according to the packaging method;

[0014] The SOC of the lithium-ion battery can be 0-100%. In particular, it relates to charged lithium batteries, that is, the negative electrode sheet has active Li embedded in it. Many methods are not designed to handle negative electrodes with higher SOC, because it is difficult to efficiently and effectively recover the negative electrode containing Li (flammable).

[0015] The disassembly method may be manual disassembly or mechanical disassembly.

[0016] In one embodiment, the step of supercritical CO2 extraction comprises:

[0017] The negative electrode is placed in a supercritical extraction device, and supercritical carbon dioxide (scCO2) is used as the extractant. The extraction is carried out at a temperature of 40-60°C and a pressure of 10-15MPa for 1-2 hours. scCO2 can effectively dissolve the binder in the negative electrode and achieve non-destructive stripping of the negative electrode material and copper foil.

[0018] After the extraction is completed, the extract and the solid residue are separated. The scCO2 can be separated and recovered and recycled by decompression (the decompression rate is usually controlled at 0.5-1MPa / min). The extract contains dissolved organic binder, which can be regenerated or recycled to obtain solid residue (including: graphite, copper foil and lithium powder).

[0019] Step S2:

[0020] In one implementation, step S2 specifically includes:

[0021] Dilute HNO3 and dilute H2SO4 were added to the solid residue in sequence, and 3% H2O2 was added as an oxidant. After thorough reaction and dissolution, further liquid-solid separation was performed to obtain a mixed solution containing copper and lithium ions (Li + , Cu 2+ 、NO3 - and SO42- Mixed solution). That is, after complete reaction and dissolution, the reaction product can be a mixed solution of LiNO3, Cu(NO3)2, Li2SO4 and CuSO4.

[0022] Preferably, the concentration of dilute HNO3 is 0.5 to 1 M; the concentration of dilute H2SO4 is 0.5 to 1 M. Liquid-solid separation can be performed by pressure filtration, centrifugal separation, suction filtration and the like.

[0023] The tail gas generated in step S2 may contain NO (dilute HNO3 reacts with copper), which needs to be captured and treated by a tail gas collection device; the tail gas treatment system is mainly composed of exhaust gas collection devices, purification devices and treatment devices, as well as control systems and other components.

[0024] Obtain high purity graphite and Li + , Cu 2+ 、NO3 - and SO4 2- The mixed solution can be exported to lithium battery recycling companies or chemical processing companies. After graphite is dried, it can be shipped in moisture-proof bags. The solution transfer container can be made of high-density polyethylene, polypropylene, stainless steel or fiberglass. During storage, the storage tank should be kept airtight and well ventilated to prevent solution leakage and contamination; the storage area should be away from fire and high temperature sources, and avoid direct sunlight and high temperature.

[0025] Step S3:

[0026] Select appropriate electrolyte and adjust current density to achieve lithium ion (Li) deposition in the electrochemical deposition process. + ) and copper ions (Cu 2+ ), thereby achieving efficient synergistic recovery of lithium and copper.

[0027] In one implementation, step S3 specifically includes:

[0028] Prepare a mixed solvent of 1M LiPF6 in EC / DMC (1:1v / v), add the above-mentioned mixed solution containing copper and lithium ions to form an electrolyte, and place it in an electrolytic cell for electrochemical deposition under an inert or vacuum atmosphere, using an inert electrode as an anode and an inert electrode or copper foil or stainless steel as a cathode: first, at a low current density (0.1-1mA / cm 2 ), lithium is deposited on the cathode surface to obtain lithium metal; after the lithium metal deposition is completed, adjust the current density (1-10mA / cm 2 ) to achieve copper deposition and ultimately obtain high-purity copper and lithium metals.

[0029] The electrolytic cell may be a single-chamber or double-chamber electrolytic cell;

[0030] The inert electrode can be a graphite electrode, a silicon carbide electrode, a glassy carbon electrode, etc.;

[0031] The inert or vacuum atmosphere includes, but is not limited to, Ar gas, He gas, or a vacuum atmosphere.

[0032] like Figure 1 As shown, the present invention provides a method for collaboratively recovering copper and lithium from negative electrodes of lithium-ion batteries, which mainly comprises the following steps:

[0033] 1. Disassemble and separate lithium-ion batteries (types: including ternary lithium batteries, lithium cobalt oxide batteries, lithium nickel oxide batteries, lithium manganese oxide batteries and lithium iron phosphate batteries, etc.; packaging types: square / cylindrical / soft pack) in the disassembly room to obtain the negative electrode; place the negative electrode in a supercritical extraction device, use supercritical carbon dioxide (scCO2) as an extractant, and extract at a temperature of 40-60°C and a pressure of 10-15MPa for 1-2 hours. scCO2 can effectively dissolve the binder in the negative electrode and achieve non-destructive stripping of the negative electrode material;

[0034] 2. After the extraction is completed, the extract and the solid residue are separated; scCO2 can be recovered and recycled by vacuum separation. The extract contains dissolved organic binders, which can be regenerated or recycled to obtain solid residues (including graphite, copper foil and lithium powder). Dilute HNO3 and dilute H2SO4 are added to the solid residue in sequence, and 3% H2O2 is added as an oxidant. The generated gas is captured and treated with an exhaust gas collection device. After thorough reaction and dissolution, Li + , Cu 2+ 、NO3 - and SO4 2- The mixed solution is further subjected to liquid-solid separation to obtain a mixed solution of copper and lithium;

[0035] 3. Prepare a mixed solvent of 1M LiPF6 in EC / DMC (1:1 v / v), add the above copper and lithium mixed solution to form an electrolyte, use an inert electrode as the anode, and use an inert electrode, copper foil or stainless steel as the cathode, and place it in an electrolytic cell for electrochemical deposition. At a low current density (0.1-1 mA / cm 2 ), lithium is deposited on the cathode surface to obtain lithium metal; after the lithium metal deposition is completed, adjust the current density (1-10mA / cm 2 ) to achieve copper deposition. The above reactions are carried out under an inert or vacuum atmosphere to ultimately obtain high-purity copper and lithium metals.

[0036] Technical effects:

[0037] Compared with the currently commonly used methods of recycling negative electrode sheets by disassembling lithium-ion batteries, such as discarding, landfilling or direct incineration, the present invention can achieve rapid recovery and utilization of copper and lithium in negative electrode sheets obtained by disassembling mainstream lithium-ion batteries on the market. Specific advantages include:

[0038] Green and environmentally friendly: Green technologies such as supercritical CO2 extraction and electrochemical deposition are used to avoid environmental pollution problems in traditional methods.

[0039] High recovery efficiency: It realizes the coordinated and efficient recovery of lithium and copper, with high recovery rate and good product quality.

[0040] Short process flow: simplifies the treatment process, reduces energy consumption and improves recovery efficiency.

[0041] Wide range of applications: Suitable for various types of lithium-ion battery negative plates, with wide applicability.

[0042] Significant economic benefits: It increases the added value of the industry and is conducive to the closed-loop development and healthy circulation of the lithium battery industry.

[0043] The present invention is of great significance for achieving green and efficient recovery, recycling and energy conservation and emission reduction of lithium and copper in the negative electrode of lithium-ion batteries, and can be widely used in lithium-ion battery production enterprises, lithium-ion battery disassembly and comprehensive treatment and recovery of negative electrode sheets.

[0044] The present invention has been described in detail above, but the above embodiments are only illustrative in nature and are not intended to limit the present invention. In addition, this article is not limited by any theory described in the above prior art or invention content or the following examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The present invention is a flow chart of the method for recovering copper and lithium from negative electrodes of lithium-ion batteries. DETAILED DESCRIPTION

[0046] The present invention is further described below in conjunction with examples. It should be noted that the following examples are provided for illustrative purposes only and do not constitute a limitation on the scope of protection claimed for the present invention.

[0047] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, methods in the art.

[0048] Example 1

[0049] A method for collaboratively recovering copper and lithium from negative electrodes of lithium-ion batteries, comprising the following steps:

[0050] (1) Dismantle the square lithium iron phosphate battery (90% SOC) in the dismantling room and separate the negative electrode sheet;

[0051] (2) The negative electrode sheet obtained in step (1) is placed in a supercritical extraction device, with scCO2 as the extractant, the temperature is set to 50°C, the pressure is 12MPa, and the extraction time is 1.5h. scCO2 can effectively dissolve the organic binder in the negative electrode material and realize the stripping of the negative electrode black powder and copper foil; after the extraction is completed, scCO2 is recovered and recycled by vacuum separation, and the vacuum rate is 0.8MPa / min, so as to achieve the separation of the extract and the solid residue (including: graphite, copper foil and lithium powder). The solid residue is placed in a reaction container, 1M dilute HNO3 and 1M dilute H2SO4 are added, and 3% H2O2 (3% is the ratio of pure H2O2 mass / total solution mass of dilute HNO3 and dilute H2SO4) is added as an oxidant, and the solid-liquid mass ratio is 1:10; the generated gas is captured and treated by an exhaust gas collection device, and after thorough reaction and dissolution, Li containing graphite is obtained. + , Cu 2+ 、NO3 - and SO4 2- The mixed liquid is filtered by a centrifuge, and the filtered graphite is washed with clean water and vacuum dried. It can be sold as defective graphite or further processed. The filtrate is Li + , Cu 2+ 、NO3 - and SO4 2- Mixed liquid;

[0052] (3) Prepare a mixed solvent of 1M LiPF6 in EC / DMC (1:1 v / v), add the above copper and lithium mixed solution to form an electrolyte, use a graphite electrode as the anode and a copper foil as the cathode, and place it in a single-chamber electrolytic cell for electrochemical deposition. 2 At the current density, the reaction was continued for 1 h, and lithium was deposited on the cathode surface to obtain lithium metal. After the lithium metal deposition was completed, the electrode was replaced and the current density was adjusted to 10 mA / cm 2 , react for 1 hour to achieve copper deposition (copper is deposited on the cathode surface to obtain copper metal), the above reaction is carried out under an inert or vacuum atmosphere, and finally high-purity copper and lithium metals are obtained. The recovery rate is shown in Table 1.

[0053] Example 2

[0054] A method for collaboratively recovering copper and lithium from negative electrodes of lithium-ion batteries is adjusted as follows relative to Example 1 (the remaining step parameters are the same):

[0055] (2) The negative electrode sheet obtained in step (1) is placed in a supercritical extraction device, with scCO2 as the extractant, the temperature is set to 60°C, the pressure is 15MPa, and the extraction time is 1h. scCO2 can effectively dissolve the organic binder in the negative electrode material and realize the stripping of the negative electrode black powder and copper foil; after the extraction is completed, scCO2 is recovered and recycled by vacuum separation, and the vacuum rate is 1MPa / min, so as to achieve the separation of the extract and the solid residue (including: graphite, copper foil and lithium powder). The solid residue is placed in a reaction container, 1M dilute HNO3 and dilute H2SO4 are added, and 3% H2O2 is added as an oxidant, and the solid-liquid mass ratio is 1:10; the generated gas is captured and treated with an exhaust gas collection device, and after thorough reaction and dissolution, Li containing graphite is obtained. + , Cu 2+ 、NO3 - and SO4 2- The mixed liquid is filtered by a centrifuge, and the filtered graphite is washed with clean water and vacuum dried. It can be sold as defective graphite or further processed. The filtrate is Li + , Cu 2+ 、NO3 - and SO4 2- Mixed liquid;

[0056] The recovery rates are shown in Table 1.

[0057] Example 3

[0058] A method for collaboratively recovering copper and lithium from negative electrodes of lithium-ion batteries is adjusted as follows relative to Example 1 (the remaining step parameters are the same):

[0059] (3) Prepare a mixed solvent of 1M LiPF6 in EC / DMC (1:1 v / v), add the above copper and lithium mixed solution to form an electrolyte, use a graphite electrode as the anode and a copper foil as the cathode, and place it in a single-chamber electrolytic cell for electrochemical deposition. 2 At the current density, the reaction was continued for 1 h, and lithium was deposited on the cathode surface to obtain lithium metal. After the lithium metal deposition was completed, the electrode was replaced and the current density was adjusted to 5 mA / cm 2 , react for 1 hour to achieve copper deposition, the above reaction is carried out under an inert or vacuum atmosphere, and finally high-purity copper and lithium metals are obtained. The recovery rate is shown in Table 1.

[0060] Example 4

[0061] A method for collaboratively recovering copper and lithium from negative electrodes of lithium-ion batteries is adjusted as follows relative to Example 1 (the remaining step parameters are the same):

[0062] (3) Prepare a mixed solvent of 1M LiPF6 in EC / DMC (1:1 v / v), add the above copper and lithium mixed solution to form an electrolyte, use a graphite electrode as the anode and a stainless steel cathode, and place it in a single-chamber electrolytic cell for electrochemical deposition. 2 At the current density, the reaction was continued for 1 h, and lithium was deposited on the cathode surface to obtain lithium metal. After the lithium metal deposition was completed, the electrode was replaced and the current density was adjusted to 10 mA / cm 2 , react for 1 hour to achieve copper deposition, the above reaction is carried out under an inert or vacuum atmosphere, and finally high-purity copper and lithium metals are obtained. The recovery rate is shown in Table 1.

[0063] Example 5

[0064] A method for collaboratively recovering copper and lithium from negative electrodes of lithium-ion batteries is adjusted as follows relative to Example 1 (the remaining step parameters are the same):

[0065] The square lithium iron phosphate battery (90% SOC) of Example 1 was replaced with a mixture of square, soft-pack, cylindrical lithium iron phosphate batteries, ternary lithium batteries, lithium manganese oxide batteries, lithium cobalt oxide batteries, etc. The recovery rate is shown in Table 1.

[0066] Comparative Example 1

[0067] A method for treating anode plates by conventional dry metallurgy is adjusted as follows relative to Example 1 (the parameters of the other steps are the same):

[0068] (1) Disassemble the square lithium iron phosphate battery (90% SOC) and separate the negative electrode sheet;

[0069] (2) The negative electrode sheet obtained in step (1) was baked at 600°C in vacuum in a N2 atmosphere to cause the binder to pyrolyze and fail, and then acid leaching and electrochemical deposition were performed in the same manner as in Example 1. The final recovery rate is shown in Table 1.

[0070] Table 1 Recovery rate of lithium and copper elements in Examples and Comparative Examples (%)

[0071] category Li Cu Example 1 95.7 97.5 Example 2 95.3 96.0 Example 3 95.1 94.8 Example 4 94.7 95.5 Example 5 93.8 95.9 Comparative Example 1 64.2 ～96

[0072] It can be seen from the data shown in Table 1 that the method for synergistically recovering copper and lithium from the negative electrode of a lithium-ion battery provided by the present invention can effectively recover the lithium and copper elements in the negative electrode sheet, wherein the element recovery rate of lithium in each embodiment is maintained at a level of 93-96%, showing a relatively good recovery efficiency. In addition, copper is maintained at more than 95%. In addition, the results of Example 5 show that the present invention can simultaneously realize the recovery of different types of negative electrode sheets of lithium batteries, and has certain applicability. The above method shows that the method for synergistically recovering copper and lithium from the negative electrode of a lithium-ion battery provided by the present invention realizes the recovery of lithium and copper to a certain extent. Considering that the existing negative electrode sheet processing method cannot recover the Li element, this method increases the added value of the industry, which is conducive to the closed-loop development and healthy cycle of the lithium battery industry. This method simplifies the processing process, and the recovered product has a high added value and has good application prospects.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and essence of the claims of the present invention; and these modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A method for recovering lithium and copper from a negative electrode of a lithium-ion battery, characterized in that: The following steps are involved: S1. Disassembling the lithium-ion battery and separating the pole pieces to obtain the negative electrode; extracting the negative electrode by supercritical CO2 to obtain a solid residue containing graphite, copper foil and lithium powder after separation; S2, adding dilute acid to the solid residue of step S1 to dissolve it, and separating to obtain a mixed solution containing copper and lithium ions; S3, adding an electrolyte to the mixed solution containing copper and lithium ions in step S2, and selectively reducing lithium ions and copper ions by electrochemical deposition to obtain copper and lithium.

2. The method according to claim 1, characterized in that The lithium-ion battery in step S1 is one or more of a ternary lithium battery, a lithium cobalt oxide battery, a lithium nickel oxide battery, a lithium manganese oxide battery and a lithium iron phosphate battery; The SOC of a lithium-ion battery is 0 to 100%.

3. The method according to claim 1, characterized in that The disassembly in step S1 is manual disassembly or mechanical disassembly.

4. The method according to claim 1, characterized in that: The supercritical CO2 extraction step of step S1 comprises: The negative electrode is placed in a supercritical extraction device, and supercritical carbon dioxide is used as the extractant. The extraction is carried out at a temperature of 40-60°C and a pressure of 10-15MPa for 1-2 hours.

5. The method according to claim 1, characterized in that Step S1 is to separate the extract and the solid residue by reducing pressure, and the pressure reduction rate is 0.5-1 MPa / min.

6. The method according to claim 1, characterized in that Step S2 specifically includes: Dilute HNO3 and dilute H2SO4 are added to the solid residue in sequence, and H2O2 is added as an oxidant. After thorough reaction and dissolution, further liquid-solid separation is performed to obtain a mixed solution containing copper and lithium ions.

7. The method according to claim 6, characterized in that The concentration of dilute HNO3 is 0.5~1M; the concentration of dilute H2SO4 is 0.5~1M.

8. The method according to claim 1, characterized in that Step S3 specifically includes: Prepare a mixed solvent of EC / DMC with a volume ratio of 1:1 with 1M LiPF6, add the mixed solution containing copper and lithium ions to form an electrolyte, and place it in an electrolytic cell for electrochemical deposition under an inert or vacuum atmosphere, using an inert electrode as an anode and an inert electrode or copper foil or stainless steel as a cathode: first, at 0.1-1 mA / cm 2 At this current density, lithium is deposited on the cathode surface to obtain lithium metal. After the lithium metal deposition is completed, the current density is adjusted to 1-10 mA / cm 2 Copper deposition is achieved, and finally high-purity copper and lithium metals are obtained.

9. The method according to claim 8, characterized in that The electrolytic cell is a single-chamber or double-chamber electrolytic cell.

10. The method according to claim 8, characterized in that The inert electrode is a graphite electrode, a silicon carbide electrode or a glassy carbon electrode.

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