Method for synchronous separation and recovery of waste lithium ion battery cell

Abstract

This invention discloses a method for the simultaneous separation and recycling of waste lithium-ion battery cells, relating to the field of lithium-ion battery recycling technology. The method includes: (1) disassembling the discharged waste lithium-ion battery to obtain battery cells; (2) using the battery cell as the cathode and an inert electrode as the anode, adding electrolyte and performing pulse electrolysis separation; (3) separating the current collector and separator obtained in step (2) from the electrolyte; (4) removing the positive electrode material layer obtained in step (2) as a whole, performing solid-liquid separation on the electrolyte to obtain negative electrode material and electrolyte containing impurities; (5) adding an alkaline solution to the electrolyte containing impurities to adjust the pH to above 12, performing solid-liquid separation to obtain a lithium-containing electrolyte; (6) introducing carbon dioxide into the lithium-containing electrolyte until the pH is 8.5-9.5, and after the reaction is complete, performing solid-liquid separation to obtain lithium carbonate precipitate and electrolyte. This method can achieve simultaneous and efficient separation of battery cells with low energy consumption.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery recycling technology, specifically to a method for the simultaneous separation and recycling of waste lithium-ion battery cells. Background Technology

[0002] Used lithium-ion batteries release harmful organic compounds and heavy metals, posing a significant risk to the environment. On the other hand, they also contain valuable strategic metals. Therefore, the recycling of used lithium-ion batteries is crucial for sustainable resource management and environmental protection.

[0003] Currently, the main recycling processes for spent lithium-ion batteries include physical-mechanical separation, pyrometallurgy, and hydrometallurgy. However, these traditional processes all have significant limitations. Physical-mechanical separation typically achieves separation through direct crushing and sieving, a process that easily leads to mixing of positive and negative electrode powders, current collector fragments, and separators, making subsequent separation and purification extremely difficult and generating dust pollution. Pyrometallurgical processes require smelting at ultra-high temperatures, resulting in extremely high energy consumption and carbon emissions. Furthermore, high-value materials such as lithium, aluminum, and graphite are often lost as slag or gas at high temperatures, leading to a low overall resource recovery rate. While hydrometallurgical processes offer higher metal recovery rates, their pretreatment stripping and leaching processes often rely on large amounts of strong acids (such as sulfuric acid and hydrochloric acid) and strong oxidants (such as hydrogen peroxide), resulting in harsh reaction conditions. This not only generates large amounts of waste acid and waste liquid containing heavy metals, easily causing serious secondary pollution, but also results in lengthy process flows and high reagent costs.

[0004] Therefore, the recycling methods for used lithium-ion batteries still need improvement. Summary of the Invention

[0005] This invention is based on the inventor's discoveries and understanding of the following facts and problems: To overcome the many shortcomings of traditional recycling processes, new recycling technologies based on electrochemical stripping have emerged in recent years. This technology typically places waste electrode sheets in a specific electrolyte as the cathode or anode, and uses a constant current or constant voltage continuous direct current (DC) electrolysis method to achieve the non-destructive separation of electrode powder and metal foil.

[0006] However, existing continuous DC electrochemical stripping technology still faces many insurmountable technical bottlenecks in practical applications. First, severe polarization leads to high stripping energy consumption. Under a continuous DC electric field, severe concentration polarization easily occurs at the electrode-solution interface. As stripping bubbles accumulate and cover the electrode interface, the system's interfacial contact resistance increases sharply, causing a rapid rise in cell voltage. A large amount of electrical energy is wasted as Joule heat, resulting in persistently high overall energy consumption. Second, severe side reactions cause significant corrosion of the current collector. Under continuous high-current polarization, the cathode surface becomes locally enriched with hydroxide ions due to the intense hydrogen evolution reaction, creating a locally strongly alkaline environment. This strongly alkaline environment easily leads to severe pitting corrosion or even large-area dissolution of amphoteric metal current collectors (such as aluminum foil). This not only significantly reduces the recovery rate of high-value aluminum foil but also introduces impurities such as aluminum ions into the electrolyte, severely interfering with subsequent electrolyte recycling and the purification of active materials. Finally, it is difficult to balance separation efficiency with material integrity. While using a low DC current density can reduce polarization and corrosion, it results in insufficient gas generation power, leading to long stripping time and low production efficiency. On the other hand, blindly increasing the DC current density can accelerate stripping, but it can lead to uncontrolled bubble nucleation, causing uneven bursting of the electrode sheet and even damaging the crystal structure of the active material.

[0007] In summary, existing waste lithium-ion battery recycling and separation technologies, especially DC electrochemical stripping technology, cannot simultaneously solve common problems such as high energy consumption, severe current collector corrosion, and polarization. Therefore, there is an urgent need in this field to develop a new technology for the simultaneous separation of waste battery cells that can effectively eliminate interfacial polarization, suppress side reactions, and achieve both high separation efficiency and low energy consumption.

[0008] This invention aims to at least partially alleviate or solve at least one of the aforementioned problems. Therefore, the object of this invention is to provide a method for the simultaneous separation and recycling of waste lithium-ion battery cells, aiming to achieve simultaneous and efficient cell stripping while reducing energy consumption.

[0009] In one aspect, the present invention provides a method for the simultaneous separation and recycling of waste lithium-ion battery cells, the method comprising: (1) Disassemble the discharged waste lithium-ion batteries to obtain battery cells; (2) Using the disassembled battery cell as the cathode and the inert electrode as the anode, electrolyte is added to the electrolytic cell for pulse electrolysis separation; (3) Separate the current collector and diaphragm obtained from the pulse electrolysis separation in step (2) from the electrolyte, and clean and dry them; (4) Take out the whole positive electrode material layer obtained by pulse electrolysis separation in step (2), and perform solid-liquid separation on the electrolyte to obtain negative electrode material and electrolyte containing impurities; (5) Add an alkaline solution to the electrolyte containing impurities obtained in step (4) to adjust the pH to above 12, and perform solid-liquid separation to obtain a lithium-containing electrolyte; (6) Carbon dioxide gas is introduced into the lithium-containing electrolyte in step (5) until the pH is 8.5-9.5. After the reaction is completed, the resulting material is separated into solid and liquid to obtain lithium carbonate precipitate and electrolyte.

[0010] The above method can achieve synchronous and efficient separation of battery cells with low energy consumption, and can also obtain high-purity lithium carbonate.

[0011] In some embodiments, the electrolyte in the electrolyte solution includes one or more of sulfate and nitrate; and / or, the concentration of the electrolyte in the electrolyte solution is 0.1-1M.

[0012] In some embodiments, the sulfate includes one or more of sodium sulfate, potassium sulfate, and ammonium sulfate, and the nitrate includes one or more of potassium nitrate, sodium nitrate, and ammonium nitrate.

[0013] In some embodiments, in step (2), pulsed current is used for pulsed electrolytic separation, wherein the pulsed current satisfies at least one of the following conditions: the density of the pulsed current is 0.1-20 A / cm³. 2 The duty cycle of the pulse current is 0.1-0.9.

[0014] In some embodiments, in step (2), pulsed electrolytic separation is performed using a pulsed voltage, wherein the pulsed voltage satisfies at least one of the following conditions: the pulsed voltage is 3-20V; the duty cycle of the pulsed voltage is 0.1-0.9.

[0015] In some embodiments, in step (5), an alkaline solution is added to the electrolyte containing impurities obtained in step (4) to adjust the pH to 12 to 13; and / or, in step (5), the solute in the alkaline solution includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0016] In some embodiments, in step (6), the rate of carbon dioxide gas introduction is 10-500 ml / min; and / or, in step (6), the time of carbon dioxide gas introduction is 0.5-6 h.

[0017] In some embodiments, the inert electrode is selected from one or more of titanium-based coated electrodes, graphite electrodes, and platinum electrodes.

[0018] In some embodiments, the solid-liquid separation in steps (4), (5), and (6) each independently includes at least one of centrifugation and filtration.

[0019] In some embodiments, the method for simultaneous separation and recycling of waste lithium-ion battery cells satisfies at least one of the following conditions: the waste lithium-ion battery is a lithium iron phosphate battery, a ternary lithium battery, a lithium manganese oxide battery, or a lithium cobalt oxide battery; the battery cell is a stacked structure or a wound structure; in step (2), the disassembled battery cell is cut, and the cut battery cell is used as the cathode. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a process flow diagram of the simultaneous separation and recycling of waste lithium-ion battery cells according to an embodiment of the present invention; Figure 2 This is a process flow diagram for the simultaneous separation and recycling of waste lithium iron phosphate battery cells according to another embodiment of the present invention; Figure 3 Images of the current collector and active material separated in Example 1 of this invention; Figure 4 Figures (a) and (b) are SEM images of the positive electrode material and negative electrode material obtained in Example 1 of the present invention, respectively. Figure 5 The image shows the XRD pattern of lithium carbonate prepared in Example 1 of this invention. Detailed Implementation

[0021] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] In one aspect of the invention, a method for the simultaneous separation and recycling of waste lithium-ion battery cells is provided. In some embodiments, reference is made to… Figure 1 The method for simultaneous separation and recycling of waste lithium-ion battery cells may include the following steps: (1) Disassemble the discharged waste lithium-ion batteries to obtain battery cells.

[0023] In this step, if the spent lithium-ion battery is already fully discharged, it can be directly disassembled to remove the battery casing and other structures, yielding a battery cell. The battery cell may include a positive electrode, a separator, and a negative electrode. In some embodiments, the battery cell may include multiple positive electrode plates, multiple separators, and multiple negative electrode plates.

[0024] In this step, if the waste lithium-ion battery is in an incompletely discharged state, it is necessary to discharge the waste lithium-ion battery first, and then disassemble it to obtain the battery cell.

[0025] In some embodiments, spent lithium-ion batteries can be lithium iron phosphate batteries, ternary lithium batteries, lithium manganese oxide batteries, or lithium cobalt oxide batteries. The above classification is based on the cathode material of the lithium-ion battery. Lithium iron phosphate batteries use lithium iron phosphate as the cathode material, ternary lithium batteries use ternary materials (such as lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide) as the cathode material, and lithium manganese oxide batteries and lithium cobalt oxide batteries use lithium manganese oxide and lithium cobalt oxide, respectively, as the cathode materials.

[0026] In some embodiments, the battery cell may be a stacked structure. In other embodiments, the battery cell may be a wound structure.

[0027] (2) Using the disassembled battery cell as the cathode and the inert electrode as the anode, electrolyte is added to the electrolytic cell for pulse electrolysis separation.

[0028] In this step, a large amount of hydrogen gas is intermittently generated on the current collector through pulse electrolysis. The collapse (bursting) of these bubbles impacts the interface, reducing its adhesion and at least partially preventing side reactions and severe polarization. This ensures complete separation of the active material from the current collector in the waste electrode, guaranteeing the purity of the current collector (e.g., aluminum foil, copper foil), separator, and active material, thus providing a foundation for subsequent battery regeneration. This method achieves efficient separation of the current collector and active material with low energy consumption. Utilizing the insulating effect of the separator between the positive and negative electrodes of the battery cell, short circuits can be avoided, achieving simultaneous separation of the positive and negative electrodes.

[0029] In some embodiments, in step (2), the entire battery cell obtained from disassembly can be used as the cathode.

[0030] In some other embodiments, in step (2), the disassembled battery cell can be cut into smaller sizes, such as 1cm×2cm, 2cm×3cm, or 4cm×6cm, and these smaller cells can be used as cathodes.

[0031] In some embodiments, the inert electrode may be selected from one or more of the following: titanium-based coated electrodes, graphite electrodes (e.g., high-purity, high-density graphite material electrodes, specifically graphite plates, graphite rods, etc.), and platinum electrodes (e.g., platinum mesh, platinum sheet, platinum wire). These electrodes possess excellent conductivity, which facilitates the formation of conductive pathways and promotes the electrolytic separation of the battery cell.

[0032] In some embodiments, in step (2), the cathode can be fully immersed in the electrolyte, which is beneficial for separating the active material from the current collector.

[0033] In some embodiments, the electrolyte in the electrolyte solution may include one or more of sulfates and nitrates. The electrolyte solution described above has a certain degree of conductivity and is not prone to causing side reactions.

[0034] In some embodiments, the concentration of the electrolyte in the electrolyte solution can be 0.1-1M, for example, 0.1M, 0.3M, 0.5M, 0.8M, 1M, etc. Therefore, the electrolyte solution has good conductivity, which is beneficial for the separation of the current collector and the active material.

[0035] In some embodiments, the electrolyte in the electrolyte solution may be selected from one or more of sulfates and nitrates, and the concentration of the electrolyte in the electrolyte solution may be 0.1-1M.

[0036] In some embodiments, sulfates may include one or more of sodium sulfate, potassium sulfate, and ammonium sulfate, and nitrates may include one or more of potassium nitrate, sodium nitrate, and ammonium nitrate.

[0037] In some embodiments, in step (2), pulsed current can be used for pulsed electrolytic separation. In some embodiments, the density of the pulsed current can be 0.1-20 A / cm³. 2 For example, the pulse current density can be 0.1 A / cm². 2 0.5A / cm 2 1A / cm 2 5A / cm 2 10A / cm 2 15A / cm 2 20A / cm 2 When the pulse current density is within the above range, it is beneficial for the rapid separation of the current collector and the active material, thereby improving the separation efficiency.

[0038] In some embodiments, the duty cycle of the pulse current can be 0.1-0.9, for example, 0.1, 0.3, 0.5, 0.7, 0.9, etc. This helps reduce energy consumption and further reduces side reactions, thereby improving the recovery rate of the current collector. In this paper, the duty cycle of the pulse current refers to the ratio of the time the current is in the on (high level) state within one pulse cycle to the total cycle time.

[0039] In some embodiments, pulsed electrolytic separation can be performed using a pulsed voltage in step (2). In some embodiments, the pulsed voltage can be 3-20V, for example, 3V, 5V, 8V, 10V, 12V, 15V, 17V, 20V, etc. Pulsed electrolytic separation under the above pulsed voltage is beneficial for the rapid separation of the current collector and the active material, thereby improving the separation efficiency.

[0040] In some embodiments, the duty cycle of the pulse voltage can be 0.1-0.9, for example, the duty cycle of the pulse voltage can be 0.1, 0.3, 0.5, 0.7, 0.9, etc. This is beneficial for reducing energy consumption and further reducing side reactions. In this article, the duty cycle of the pulse voltage refers to the ratio of the duration of the high level (i.e., the voltage is in an effective state) to the total cycle time within one pulse cycle.

[0041] (3) Separate the current collector and diaphragm obtained from the pulse electrolysis separation in step (2) from the electrolyte, and clean and dry them.

[0042] After pulse electrolysis separation in step (2), the positive electrode material layer will be separated from the positive electrode current collector, and the negative electrode material will be separated from the negative electrode current collector. The positive electrode current collector, negative electrode current collector and separator are taken out from the electrolyte and cleaned and dried to realize the recycling of the positive electrode current collector, negative electrode current collector and separator, which can be reused later.

[0043] In some specific embodiments, the current collector and the diaphragm can be washed with water and dried. Of course, those skilled in the art can also choose other cleaning and drying methods according to the actual situation.

[0044] (4) Take out the whole positive electrode material layer obtained by pulse electrolysis separation in step (2), and perform solid-liquid separation on the electrolyte to obtain negative electrode material and electrolyte containing impurities.

[0045] During pulse electrolytic separation, hydrogen gas is generated at the interfaces between the positive current collector and the positive electrode material layer, and at the interfaces between the negative current collector and the negative electrode material layer. The bonding strength between the positive electrode material and the binder in the positive electrode material layer is relatively strong, causing the positive electrode material layer to peel off from the positive current collector as a whole. Conversely, the bonding strength between the negative electrode material and the binder in the negative electrode material layer is relatively weak, causing the negative electrode material to detach from the negative current collector in powder form and disperse in the electrolyte. Therefore, the positive electrode material layer can be removed as a whole, and then solid-liquid separation can be performed on the electrolyte to obtain the negative electrode material and the electrolyte containing impurities.

[0046] In some embodiments, after the entire positive electrode material layer is removed, it can be cleaned and dried. For example, it can be cleaned with deionized water and then dried in a drying oven.

[0047] During the pulse electrolysis separation process, lithium elements in the negative electrode material layer will dissolve in the electrolyte. In addition, a small amount of positive electrode material and a small amount of positive electrode current collector (such as aluminum foil) may also dissolve in the electrolyte. Therefore, the electrolyte will contain some impurities.

[0048] In step (4), solid-liquid separation may include at least one of centrifugation and filtration, which can separate the negative electrode material from the electrolyte. In some specific embodiments, vacuum filtration can be used to obtain the negative electrode material and the electrolyte containing impurities.

[0049] In some embodiments, the negative electrode material obtained by solid-liquid separation can be dried, for example, the negative electrode material can be dried in a drying oven and then collected.

[0050] (5) Add an alkaline solution to the electrolyte containing impurities obtained in step (4) to adjust the pH to above 12, and perform solid-liquid separation to obtain a lithium-containing electrolyte.

[0051] Adding an alkaline solution can cause metallic impurities in the electrolyte to precipitate (for example, iron ions react with hydroxide ions to form a metallic impurity precipitate). Adjusting the pH of the electrolyte to above 12 with an alkaline solution allows hydroxide ions to react fully with the metallic impurities, forming an electrolyte containing trace amounts of metallic impurity precipitates. This facilitates the removal of metallic impurities such as iron ions from the electrolyte. Solid-liquid separation can then remove the metallic impurity precipitates from the electrolyte, yielding a lithium-containing electrolyte.

[0052] In some embodiments, the solid-liquid separation in step (5) may include at least one of centrifugation and filtration. In some specific embodiments, solid-liquid separation may be performed by vacuum filtration in step (5).

[0053] In some embodiments, in step (5), an alkaline solution can be added to the electrolyte containing impurities obtained in step (4) to adjust the pH to 12 to 13. This facilitates the removal of metal element impurities and does not introduce other impurities.

[0054] In some embodiments, in step (5), the solute in the alkaline solution may include one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide. This facilitates the removal of metallic element impurities without introducing other impurities.

[0055] (6) Carbon dioxide gas is introduced into the lithium-containing electrolyte in step (5) until the pH is 8.5-9.5. After the reaction is completed, the resulting material is separated into solid and liquid to obtain lithium carbonate precipitate and electrolyte.

[0056] In this step, carbon dioxide gas is introduced into the lithium-containing electrolyte until the pH of the electrolyte is 8.5-9.5, allowing the lithium ions in the electrolyte to react fully with the carbon dioxide to form lithium carbonate precipitate. After the reaction, the material is subjected to solid-liquid separation, and the separated solid is dried to obtain recyclable and reusable lithium carbonate precipitate and electrolyte. In some embodiments, the solid-liquid separation in step (6) may include at least one of centrifugation and filtration. In some specific embodiments, the material after the reaction can be filtered to obtain lithium carbonate precipitate and electrolyte.

[0057] In some embodiments, in step (6), the rate at which carbon dioxide gas is introduced can be 10-500 ml / min, for example, the rate at which carbon dioxide gas is introduced can be 10 ml / min, 50 ml / min, 100 ml / min, 200 ml / min, 300 ml / min, 400 ml / min, 500 ml / min, etc. This facilitates the full utilization of carbon dioxide gas and reduces waste.

[0058] In some embodiments, in step (6), the carbon dioxide gas can be introduced for 0.5-6 hours, for example, 0.5 hours, 0.75 hours, 1 hour, 3 hours, 5 hours, 6 hours, etc. This allows lithium ions to fully react with carbon dioxide to form a precipitate, thereby improving the recovery rate of lithium carbonate.

[0059] In some specific embodiments of this application, reference is made to Figure 2Discharged lithium iron phosphate batteries are disassembled to obtain spent lithium iron phosphate cells. Using these cells as cathodes and inert electrodes as anodes, electrolyte is added to an electrolytic cell for pulse electrolysis separation. The bonding force between the lithium iron phosphate positive electrode material and the binder (e.g., PVDF) is strong. During pulse electrolysis, hydrogen gas is generated at the interface between the positive electrode current collector (aluminum foil) and the positive electrode material layer, causing the entire positive electrode material layer to peel off from the aluminum foil. The bonding force between the negative electrode material (e.g., graphite) and the binder is relatively weak. During pulse electrolysis, hydrogen gas is generated at the interface between the negative electrode current collector (copper foil) and the negative electrode material layer, causing the negative electrode material to peel off from the copper foil and disperse as powder in the electrolyte. The resulting positive and negative electrode current collectors and separator are separated from the electrolyte, cleaned, and dried to obtain reusable current collectors and separators. The positive electrode material layer is removed as a whole, and then the electrolyte is separated into solid and liquid components to obtain the negative electrode material and the electrolyte containing impurities. Adding sodium hydroxide solution to the electrolyte containing impurities to adjust the pH to 12 yields an electrolyte containing trace amounts of metal impurities. Solid-liquid separation is then performed to obtain the metal impurity precipitate (hydroxide precipitate) and the lithium-containing electrolyte. Passing carbon dioxide gas into the lithium-containing electrolyte to a pH of 9 causes the lithium ions in the electrolyte to form lithium carbonate precipitate. After the reaction is complete, filtration yields the lithium carbonate precipitate (which can be dried to obtain dry lithium carbonate) and the electrolyte. The electrolyte can be reused.

[0060] Compared with the prior art, the beneficial effects of the method proposed in this invention are reflected in the following aspects: (1) The present invention generates a large amount of hydrogen gas intermittently on the current collector through pulse electrolysis. The impact of bubble collapse (bursting) on ​​the interface reduces the adhesion of the interface. This can at least avoid side reactions and severe polarization to a certain extent, and completely separate the active material in the waste electrode from the current collector, ensuring the purity of the current collector (e.g., aluminum foil, copper foil), separator and active material, and providing a basis for subsequent battery regeneration.

[0061] (2) The present invention simplifies the separation process. By utilizing the insulating effect of the separator between the positive and negative electrode plates of the waste battery cell, short circuits can be avoided and the positive and negative electrodes can be separated synchronously. By introducing carbon dioxide gas into the lithium-containing electrolyte, lithium ions can generate high-purity lithium carbonate precipitate, thereby realizing the recovery of lithium resources.

[0062] (3) The pulse electrolysis separation method can reduce energy consumption, has a simple process flow, is green and pollution-free, and can achieve efficient and non-destructive stripping of waste lithium-ion battery cells, reduce or even avoid aluminum impurity pollution, and ensure recycling purity.

[0063] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the materials and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0064] Example 1 A method for simultaneous separation and recycling of waste lithium-ion battery cells. In this embodiment, lithium iron phosphate batteries are used as an example. The process flow diagram is shown below. Figure 2 Specifically, it includes the following steps: (1) Disassemble the discharged waste lithium iron phosphate batteries, cut the disassembled waste lithium iron phosphate cells into 1cm×2cm (electrode area) pieces and place them in an electrolytic cell as cathodes, with a platinum mesh as anodes, and control the sodium sulfate electrolyte concentration to 0.5M. Then, use pulsed current electrolysis to separate the active materials (including positive and negative electrode materials), current collectors, and separators of the lithium iron phosphate cells. The pulsed current conditions are: current density of 0.5A / cm. 2 The duty cycle was 0.5. After separation, the complete aluminum foil, copper foil, separator, and positive electrode active material layer were removed, rinsed with deionized water, and dried in a vacuum drying oven at 60°C for 24 hours. The separation rate was then calculated.

[0065] (2) The graphite anode material mixture of the waste lithium iron phosphate battery cell in step (1) is filtered and separated to obtain an electrolyte containing trace metal element impurities. The metal element content (lithium leaching rate, iron leaching rate, aluminum leaching rate) in the electrolyte is shown in Table 1. The separated graphite powder is dried in a vacuum drying oven for 24 hours and then collected.

[0066] (3) Add sodium hydroxide to the electrolyte containing impurities in step (2) to adjust the pH to 12, and filter to obtain lithium electrolyte and impurity precipitate.

[0067] (4) Carbon dioxide was introduced into the lithium-containing electrolyte obtained in step (3) at a rate of 100 ml / min to adjust the pH to 9. The electrolyte and lithium carbonate were obtained by vacuum filtration. After the lithium carbonate was dried, the lithium content was detected by inductively coupled plasma mass spectrometry. The purity of lithium carbonate was calculated to be over 99.5%.

[0068] Figure 3 Images of the current collector and active material separated in Example 1, wherein, Figure 3 The image above shows an aluminum foil (positive electrode current collector) and two layers of positive electrode material peeled off from the aluminum foil. Figure 3The two images below are of copper foil (negative electrode current collector) and graphite negative electrode material peeled off from the copper foil, respectively. Figure 4 Figures (a) and (b) are SEM images of the positive electrode material (lithium iron phosphate) and negative electrode material (graphite) obtained from the separated battery cell in Example 1, respectively. Figure 4 It can be seen that the positive and negative electrode materials are well preserved. Figure 5 The image shows the XRD pattern of lithium carbonate prepared in Example 1. Figure 5 The white powder in the upper right corner is lithium carbonate material recovered in Example 1. From... Figure 5 As can be seen, the XRD peak positions of the white powder correspond to those of the lithium carbonate standard card (PDF#99-000-4385), indicating that the precipitate is lithium carbonate.

[0069] Example 2 A method for simultaneous separation and recycling of waste lithium-ion battery cells specifically includes the following steps: (1) Disassemble the discharged waste lithium iron phosphate batteries, cut the disassembled waste lithium iron phosphate cells into 1cm×2cm (electrode area) pieces and place them in an electrolytic cell as cathodes, with a platinum mesh as anodes, and control the ammonium sulfate electrolyte concentration to 0.2M. Then, use pulsed current electrolysis to separate the active materials (including positive and negative electrode materials), current collectors, and separators of the lithium iron phosphate cells. The pulsed current conditions are: current density of 5A / cm². 2 The duty cycle is 0.5. After separation, the complete aluminum foil, copper foil, separator and positive electrode active material layer are taken out, rinsed with deionized water and dried in a vacuum drying oven at 60°C for 24 hours.

[0070] (2) The graphite anode material mixture of the waste lithium iron phosphate battery cell in step (1) is filtered and separated to obtain an electrolyte containing trace metal element impurities. The metal element content (lithium leaching rate, iron leaching rate, aluminum leaching rate) in the electrolyte is shown in Table 1. The separated graphite powder is dried in a vacuum drying oven for 24 hours and then collected.

[0071] (3) Add sodium hydroxide to the electrolyte containing impurities in step (2) to adjust the pH to 12, and filter to obtain lithium electrolyte and impurity precipitate.

[0072] (4) Carbon dioxide was introduced into the lithium-containing electrolyte obtained in step (3) at a rate of 200 ml / min to adjust the pH to 9. The electrolyte and lithium carbonate were obtained by vacuum filtration. After the lithium carbonate was dried, the lithium content was detected by inductively coupled plasma mass spectrometry. The purity of lithium carbonate was calculated to be over 99.6%.

[0073] Example 3 A method for simultaneous separation and recycling of waste lithium-ion battery cells specifically includes the following steps: (1) Disassemble the discharged waste lithium iron phosphate batteries, cut the disassembled waste lithium iron phosphate cells into 1cm×2cm (electrode area) pieces and place them in an electrolytic cell as cathodes, with a platinum mesh as anodes, and control the potassium nitrate electrolyte concentration to 0.5M. Then, use pulsed current electrolysis to separate the active materials (including positive and negative electrode materials), current collectors, and separators of the lithium iron phosphate cells. The pulsed current conditions are: current density of 5A / cm². 2 The duty cycle is 0.2. After separation, the complete aluminum foil, copper foil, separator and positive electrode active material layer are taken out, rinsed with deionized water and dried in a vacuum drying oven at 60°C for 24 hours.

[0074] (2) The graphite anode material mixture of the waste lithium iron phosphate battery cell in step (1) is filtered and separated to obtain an electrolyte containing trace metal element impurities. The metal element content (lithium leaching rate, iron leaching rate, aluminum leaching rate) in the electrolyte is shown in Table 1. The separated graphite powder is dried in a vacuum drying oven for 24 hours and then collected.

[0075] (3) Add lithium hydroxide to the electrolyte containing impurities in step (2) to adjust the pH to 12, and filter to obtain lithium electrolyte and impurity precipitate.

[0076] (4) Carbon dioxide was introduced into the lithium-containing electrolyte obtained in step (3) at a rate of 200 ml / min to adjust the pH to 9. The electrolyte and lithium carbonate were obtained by vacuum filtration. After the lithium carbonate was dried, the lithium content was detected by inductively coupled plasma mass spectrometry. The purity of lithium carbonate was calculated to be over 99.8%.

[0077] Example 4 A method for simultaneous separation and recycling of waste lithium-ion battery cells specifically includes the following steps: (1) Disassemble the discharged waste lithium iron phosphate batteries, cut the disassembled waste lithium iron phosphate cells into 1cm×2cm (electrode area) pieces and place them in an electrolytic cell as cathodes, with a platinum mesh as anodes, and control the sodium sulfate electrolyte concentration to 1M. Then, use pulse voltage electrolysis to separate the active materials (including positive and negative electrode materials), current collectors and separators of the lithium iron phosphate cells. The pulse voltage conditions are: voltage of 10 V and duty cycle of 0.5. After separation, take out the complete aluminum foil, copper foil, separator and positive electrode active material layer, rinse with deionized water and dry in a vacuum drying oven at 60℃ for 24 hours.

[0078] (2) The graphite anode material mixture of the waste lithium iron phosphate battery cell in step (1) is filtered and separated to obtain an electrolyte containing trace metal element impurities. The metal element content (lithium leaching rate, iron leaching rate, aluminum leaching rate) in the electrolyte is shown in Table 1. The separated graphite powder is dried in a vacuum drying oven for 24 hours and then collected.

[0079] (3) Add sodium hydroxide to the electrolyte containing impurities in step (2) to adjust the pH to 12, and filter to obtain lithium electrolyte and impurity precipitate.

[0080] (4) Carbon dioxide was introduced into the lithium-containing electrolyte obtained in step (3) at a rate of 50 ml / min to adjust the pH to 9. The electrolyte and lithium carbonate were obtained by vacuum filtration. After the lithium carbonate was dried, the lithium content was detected by inductively coupled plasma mass spectrometry. The purity of lithium carbonate was calculated to be over 99.6%.

[0081] Example 5 The difference from Example 1 is that the duty cycle of the pulse current in step (1) of Example 5 is 0.9. The remaining steps and parameters are the same as in Example 1. The lithium leaching rate, iron leaching rate, aluminum leaching rate, separation rate, and lithium carbonate purity are recorded in Table 2.

[0082] Example 6 The difference from Example 1 is that in step (1) of Example 6, the disassembled waste lithium iron phosphate cells are not cut, and the large-area cells are directly used as cathodes, with a pulse current density of 20A / cm. 2 The remaining steps and parameters are the same as in Example 1. The lithium leaching rate, iron leaching rate, aluminum leaching rate, separation rate, and lithium carbonate purity are recorded in Table 2.

[0083] Example 7 Unlike Example 4, the voltage in step (1) of Example 7 is 3V. The remaining steps and parameters are the same as in Example 4. The lithium leaching rate, iron leaching rate, aluminum leaching rate, separation rate, and lithium carbonate purity are recorded in Table 2.

[0084] Example 8 Unlike Example 4, the voltage in step (1) of Example 8 is 20V. The remaining steps and parameters are the same as in Example 4. The lithium leaching rate, iron leaching rate, aluminum leaching rate, separation rate, and lithium carbonate purity are recorded in Table 2.

[0085] Example 9 Unlike Example 4, the duty cycle of the pulse voltage in step (1) of Example 9 is 0.9. The remaining steps and parameters are the same as in Example 4. The lithium leaching rate, iron leaching rate, aluminum leaching rate, separation rate, and lithium carbonate purity are recorded in Table 2.

[0086] Comparative Example 1 The difference between this comparative example and Example 1 is that in this comparative example, no electrolyte is added to the electrolyte in step (1); all other processes are the same as in Example 1. The results are shown in Table 1, which indicates that pure water has poor conductivity, resulting in low hydrogen production efficiency and poor stripping effect. Furthermore, in Comparative Example 1, lithium element was not recovered.

[0087] Comparative Example 2 The difference between this comparative example and Example 1 is that in this comparative example, in step (1), constant current electrolysis is used, and the current density is 0.5 A / cm². 2 All other processes are the same as in Example 1. This comparative example does not use pulsed current for processing. The results are shown in Table 1, indicating that constant current electrolysis will lead to localized over-alkaliness in the current collector, corrosion of the current collector, and an increase in the content of metal impurities, affecting the purity of lithium carbonate.

[0088] Table 1

[0089] Table 2

[0090] The calculation methods for separation rate η1 and metal element leaching rate η2 are shown in equations (1) and (2): Equation (1), Equation (2), in: M is the total mass of the battery cell (g); m1 is the sum of the mass of the dried current collector (including copper foil and aluminum foil) and the separator; m2 is the sum of the mass of the recovered positive electrode material layer and the graphite negative electrode material; m3 is the theoretical metal element mass of the electrode sheet. After cutting a portion of the battery cell (positive electrode, negative electrode and separator) and digesting it in a digestion tube, ICP is measured, and the theoretical metal element mass is calculated based on the ICP test results; C is the metal element detection concentration in the electrolyte (referring to the electrolyte containing trace metal element impurities in step (2) of each embodiment and comparative example); V is the volume of the electrolyte.

[0091] In addition, the pulse electrolysis separation method can also be used to completely strip the active material and current collector from nickel-cobalt-manganese ternary lithium-ion batteries, lithium manganese oxide batteries, and lithium cobalt oxide batteries.

[0092] In the description of this invention, the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and are not intended to require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0093] In the description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0094] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for simultaneous separation and recycling of waste lithium-ion battery cells, characterized in that, include: (1) Disassemble the discharged waste lithium-ion batteries to obtain battery cells; (2) Using the disassembled battery cell as the cathode and the inert electrode as the anode, electrolyte is added to the electrolytic cell for pulse electrolysis separation; (3) Separate the current collector and diaphragm obtained from the pulse electrolysis separation in step (2) from the electrolyte, and clean and dry them; (4) Take out the whole positive electrode material layer obtained by pulse electrolysis separation in step (2), and perform solid-liquid separation on the electrolyte to obtain negative electrode material and electrolyte containing impurities; (5) Add an alkaline solution to the electrolyte containing impurities obtained in step (4) to adjust the pH to above 12, and perform solid-liquid separation to obtain a lithium-containing electrolyte; (6) Carbon dioxide gas is introduced into the lithium-containing electrolyte in step (5) until the pH is 8.5-9.

5. After the reaction is completed, the resulting material is separated into solid and liquid to obtain lithium carbonate precipitate and electrolyte.

2. The method according to claim 1, characterized in that, The electrolyte in the electrolyte solution includes one or more of sulfates and nitrates; and / or, the concentration of the electrolyte in the electrolyte solution is 0.1-1M.

3. The method according to claim 2, characterized in that, The sulfate includes one or more of sodium sulfate, potassium sulfate, and ammonium sulfate, and the nitrate includes one or more of potassium nitrate, sodium nitrate, and ammonium nitrate.

4. The method according to claim 1, characterized in that, In step (2), pulsed current is used for pulsed electrolytic separation, wherein the pulsed current satisfies at least one of the following conditions: The density of the pulse current is 0.1-20 A / cm. 2 ; The duty cycle of the pulse current is 0.1-0.

9.

5. The method according to claim 1, characterized in that, In step (2), pulsed electrolytic separation is performed using a pulsed voltage, wherein the pulsed voltage satisfies at least one of the following conditions: The pulse voltage is 3-20V; The duty cycle of the pulse voltage is 0.1-0.

9.

6. The method according to claim 1, characterized in that, In step (5), an alkaline solution is added to the electrolyte containing impurities obtained in step (4) to adjust the pH to 12 to 13; And / or, in step (5), the solute in the alkaline solution includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide.

7. The method according to claim 1, characterized in that, In step (6), the rate of carbon dioxide gas introduction is 10-500 ml / min; And / or, in step (6), the carbon dioxide gas is introduced for 0.5-6 hours.

8. The method according to claim 1, characterized in that, The inert electrode is selected from one or more of titanium-based coated electrodes, graphite electrodes, and platinum electrodes.

9. The method according to claim 1, characterized in that, The solid-liquid separation in steps (4), (5), and (6) each independently includes at least one of centrifugation and filtration.

10. The method according to any one of claims 1-9, characterized in that, At least one of the following conditions must be met: The waste lithium-ion batteries are lithium iron phosphate batteries, ternary lithium batteries, lithium manganese oxide batteries, or lithium cobalt oxide batteries. The battery cell has a stacked structure or a wound structure; In step (2), the disassembled battery cells are cut and the cut battery cells are used as cathodes.

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