A method for the integrated recycling of waste lithium iron phosphate cathode sheets and the recycling of lithium iron phosphate cathode sheets

Abstract

This disclosure discloses a method for regenerating waste lithium iron phosphate (LFP) cathode sheets and the method for regenerating LFP cathode sheets. Through electrochemical means, LFP can be regenerated without destroying its structure. This method avoids the large-scale discharge of acid and alkaline wastewater in wet recycling and the problem of LFP crystal lattice changes caused by aerobic calcination in pyrometallurgical recycling, which leads to a decrease in LFP activity. The process is simple, does not require stripping LFP from the cathode sheet, and the regenerated cathode sheet is obtained directly. No additional binders and conductive agents are needed in the cathode sheet. Furthermore, the performance of the regenerated LFP cathode material is comparable to that of the initially prepared LFP cathode material.

Description

Technical Field

[0001] This disclosure relates to the field of cathode material recycling technology, and more specifically, to a method for the integrated regeneration of waste lithium iron phosphate cathode sheets and the regenerated lithium iron phosphate cathode sheets. Background Technology

[0002] In recent years, the rapid development of new energy vehicles and 3C electronic products has led to a surge in lithium-ion battery shipments, resulting in a large volume of waste lithium batteries. It is estimated that by 2025, retired power batteries from China's new energy vehicles could reach 300,000 tons. Lithium iron phosphate cathode materials, due to their wide availability, low price, good thermal stability, high cycle performance, and environmental friendliness, are increasingly widely used in 3C products, electric bicycles, electric vehicles, and energy storage power stations, resulting in a significant amount of retired batteries. Waste lithium batteries contain large amounts of valuable metals and electrolytes; improper disposal can cause not only environmental pollution but also economic loss.

[0003] Retired power batteries typically undergo processes such as discharge, crushing, leaching, and regeneration to recover valuable metal elements. Currently, there are two routes for recycling cathode materials from spent lithium iron phosphate batteries: wet recycling and pyrometallurgical recycling. Wet recycling involves acid treatment of the stripped cathode active material followed by stepwise precipitation, generating significant amounts of wastewater. Pyrometallurgical recycling involves crushing and calcining the stripped cathode active material to remove binders and conductive agents, but this reduces the activity of lithium iron phosphate, and binders and conductive agents cannot be recovered. Both methods are lengthy and some components, such as binders, cannot be recovered. Therefore, a simple, environmentally friendly method for regenerating spent lithium iron phosphate battery cathode materials with high component recovery rates is particularly necessary.

[0004] In view of this, this disclosure is hereby made. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method for the integrated recycling of waste lithium iron phosphate cathode sheets and the recycling of lithium iron phosphate cathode sheets, which can regenerate cathode materials without damaging the cathode material structure, and the process is simple.

[0006] This disclosure is implemented as follows:

[0007] In a first aspect, this disclosure provides a method for regenerating waste lithium iron phosphate cathode sheets, including:

[0008] Anode delithiation and impurity removal: using waste lithium iron phosphate positive electrode sheet or pre-delithiation waste lithium iron phosphate positive electrode sheet as the first anode and an inert electrode as the first cathode, the first cathode and the first anode are placed in the delithiation and impurity removal electrolyte, and a voltage of 1V-3V is applied between the first cathode and the first anode to obtain delithiation and impurity removal waste lithium iron phosphate positive electrode sheet;

[0009] The cathode lithium replenishment method uses a delithiated and impurity-removed waste lithium iron phosphate positive electrode sheet as the second cathode and an inert electrode or a waste lithium iron phosphate positive electrode sheet as the second anode. The second cathode and the second anode are placed in a lithium replenishment electrolyte, and a voltage of 0.1V-1V is applied between the second cathode and the second anode. When the second anode is an inert electrode, a regenerated lithium iron phosphate positive electrode sheet is obtained; when the second anode is a waste lithium iron phosphate positive electrode sheet, a regenerated lithium iron phosphate positive electrode sheet and a pre-delithiated waste lithium iron phosphate positive electrode sheet are obtained.

[0010] In some embodiments, the voltage in the anode delithiation and impurity removal step is provided by spent lithium-ion batteries.

[0011] In some embodiments, the anode delithiation and impurity removal step uses a spent lithium-ion battery discharged to 1V-3V as a power source. When the rate of change of the first anode potential is less than a first preset value within 10 minutes, the anode delithiation and impurity removal step ends.

[0012] In some implementations, the first preset value is 0.1%.

[0013] In some embodiments, the waste lithium-ion batteries include at least one of waste lithium iron phosphate batteries, waste ternary lithium batteries, waste lithium cobalt oxide batteries, and waste lithium manganese oxide batteries.

[0014] In some embodiments, the delithiation and impurity removal electrolyte includes 0.1 mol / L to 0.5 mol / L of soluble salt.

[0015] In some embodiments, the mass fraction of lithium in the regenerated lithium iron phosphate cathode is 4.40% or more.

[0016] In some embodiments, the voltage in the cathode replenishment step is provided by a spent lithium-ion battery.

[0017] In some embodiments, the cathode lithium replenishment step uses a spent lithium-ion battery discharged to 1V as a power source, and the cathode lithium replenishment step ends when the rate of change of the second cathode potential is less than a second preset value within 10 minutes.

[0018] In some implementations, the second preset value is 0.1%.

[0019] In some embodiments, the lithium-replenishing electrolyte includes a soluble lithium salt.

[0020] In some embodiments, the concentration of lithium ions in the lithium-replenishing electrolyte is 0.1 mol / L to 2 mol / L.

[0021] In some embodiments, the delithiation and impurity removal electrolyte contains soluble lithium salts, and the anode delithiation and impurity removal electrolyte, after completing the delithiation and impurity removal step, participates in the cathode lithium replenishment step as a lithium replenishment electrolyte.

[0022] In some embodiments, the soluble lithium salt includes at least one of lithium chloride and lithium sulfate.

[0023] In some embodiments, after lithium replenishment at the cathode, the regenerated lithium iron phosphate cathode sheet is dried at a temperature of 55°C-80°C.

[0024] In some implementations, when a waste lithium iron phosphate cathode sheet is used as the second anode, the second anode can be replaced if the rate of change of the second anode potential within 10 minutes is less than a third preset value.

[0025] In some implementations, the third preset value is 0.1%.

[0026] Secondly, this disclosure provides a lithium iron phosphate cathode obtained by the method for regenerating waste lithium iron phosphate cathodes as described in any of the foregoing embodiments.

[0027] This disclosure has the following beneficial effects:

[0028] Waste lithium iron phosphate cathode sheets, after long-term use, contain some organic matter and metallic impurities, such as electrolyte residue and impurities introduced during battery processing. In the method for regenerating waste lithium iron phosphate cathode sheets provided in this embodiment, these impurities are first removed under a higher voltage. However, the removal of impurities is accompanied by delithiation, resulting in lithium iron phosphate in a low-lithiation state. Therefore, the next step is to replenish lithium on the delithiated and impurity-removed waste lithium iron phosphate cathode sheets to obtain regenerated lithium iron phosphate cathode sheets.

[0029] This embodiment utilizes an electrochemical method to regenerate lithium iron phosphate without damaging its structure. It avoids the large-scale discharge of acidic and alkaline wastewater during wet recycling and the lattice changes caused by aerobic calcination during pyrometallurgical recycling, which can lead to reduced activity of lithium iron phosphate. Furthermore, the process is simple, eliminating the need to peel lithium iron phosphate from the cathode sheet. The regenerated cathode sheet is obtained directly, and no additional binders or conductive agents are required. Moreover, the performance of the regenerated lithium iron phosphate cathode material is comparable to that of the initially prepared lithium iron phosphate cathode material. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a process flow diagram for Example 1. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the embodiments of this disclosure will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] In a first aspect, this disclosure provides a method for regenerating waste lithium iron phosphate cathode sheets, including:

[0034] Anode delithiation and impurity removal: using waste lithium iron phosphate positive electrode sheet or pre-delithiation waste lithium iron phosphate positive electrode sheet as the first anode and an inert electrode as the first cathode, the first cathode and the first anode are placed in the delithiation and impurity removal electrolyte, and a voltage of 1V-3V is applied between the first cathode and the first anode to obtain delithiation and impurity removal waste lithium iron phosphate positive electrode sheet;

[0035] The cathode lithium replenishment method uses a delithiated and impurity-removed waste lithium iron phosphate positive electrode sheet as the second cathode and an inert electrode or a waste lithium iron phosphate positive electrode sheet as the second anode. The second cathode and the second anode are placed in a lithium replenishment electrolyte, and a voltage of 0.1V-1V is applied between the second cathode and the second anode. When the second anode is an inert electrode, a regenerated lithium iron phosphate positive electrode sheet is obtained; when the second anode is a waste lithium iron phosphate positive electrode sheet, a regenerated lithium iron phosphate positive electrode sheet and a pre-delithiated waste lithium iron phosphate positive electrode sheet are obtained.

[0036] Waste lithium iron phosphate cathode sheets, after long-term use, contain some organic matter and metallic impurities, such as electrolyte residue and impurities introduced during battery processing. In the method for regenerating waste lithium iron phosphate cathode sheets provided in this embodiment, these impurities are first removed under a higher voltage. However, the removal of impurities is accompanied by delithiation, resulting in lithium iron phosphate in a low-lithiation state. The next step in this embodiment is to replenish lithium on the delithiated and impurity-removed waste lithium iron phosphate cathode sheets to obtain regenerated lithium iron phosphate cathode sheets.

[0037] This embodiment utilizes an electrochemical method to regenerate lithium iron phosphate without damaging its structure. It avoids the large-scale discharge of acidic and alkaline wastewater during wet recycling and the lattice changes caused by aerobic calcination during pyrometallurgical recycling, which can lead to reduced activity of lithium iron phosphate. Furthermore, the process is simple, eliminating the need to peel lithium iron phosphate from the cathode sheet. The regenerated cathode sheet is obtained directly, and no additional binders or conductive agents are required. Moreover, the performance of the regenerated lithium iron phosphate cathode material is comparable to that of the initially prepared lithium iron phosphate cathode material.

[0038] In the cathode lithium replenishment step of this embodiment, an inert electrode can be used as the anode, or a waste lithium iron phosphate cathode sheet can be used as the anode. When a waste lithium iron phosphate cathode sheet is used as the anode, some of the lithium can be initially removed. However, due to the difficulty in removing impurities, the pre-delithiated waste lithium iron phosphate cathode sheet obtained after cathode lithium replenishment still contains a large amount of impurities. Therefore, the pre-delithiated waste lithium iron phosphate cathode sheet can be used as the anode in the delithiation and impurity removal step. Under a higher voltage, the impurities can be removed more completely. Then, it can be transferred back to the cathode lithium replenishment step as the cathode for lithium replenishment to obtain a regenerated lithium iron phosphate cathode sheet.

[0039] The inert electrodes in both the anode delithiation and cathode lithium replenishment steps can be platinum electrodes.

[0040] In this embodiment, the voltage in the anode delithiation and impurity removal step is 1V-3V. Specifically, it can be a constant voltage of any value between 1V, 1.5V, 2V, 2.5V, 3V or 1V-3V, or it can be a fluctuating or changing voltage, for example, the voltage gradually decreases from 3V to 1V.

[0041] In this embodiment, the voltage in the cathode lithium replenishment and impurity removal step is 0.1V-1V. Specifically, it can be a constant voltage of any value between 0.1V, 0.5V, 1V or 0.1V-1V, or it can be a fluctuating voltage, for example, the voltage gradually decreases from 1V to 0.1V.

[0042] In some embodiments, the voltage in the anode delithiation and impurity removal step is provided by spent lithium-ion batteries.

[0043] In some embodiments, the anode delithiation and impurity removal step uses a spent lithium-ion battery discharged to 1V-3V as a power source. When the rate of change of the first anode potential is less than a first preset value within 10 minutes, the anode delithiation and impurity removal step ends.

[0044] If a waste lithium-ion battery or a group of waste lithium-ion batteries is discharged to a voltage of 1V and the anode delithiation and impurity removal step is not yet completed, the anode delithiation and impurity removal step can be continued after replacing the battery or battery group.

[0045] In some implementations, the first preset value is 0.1%.

[0046] In some embodiments, the waste lithium-ion batteries include at least one of waste lithium iron phosphate batteries, waste ternary lithium batteries, waste lithium cobalt oxide batteries, and waste lithium manganese oxide batteries, as long as they still have residual energy to meet the voltage requirements.

[0047] In some embodiments, the anode delithiation and impurity removal electrolyte includes 0.1 mol / L to 0.5 mol / L of soluble salt, specifically any value between 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, or 0.1 mol / L to 0.5 mol / L.

[0048] The soluble salt in this embodiment can specifically be a sodium salt, lithium salt, potassium salt, sulfate salt, chloride salt, etc., and can be one of them or a mixture of two or more, such as sodium chloride, sodium sulfate, lithium chloride, lithium nitrate, etc.

[0049] In some embodiments, the mass fraction of lithium in the regenerated lithium iron phosphate cathode is 4.40% or more, and the theoretical value of lithium content in lithium iron phosphate is 4.43%. When the lithium content is 4.40%, lithium replenishment can be considered to be completed.

[0050] In some embodiments, the voltage in the cathode replenishment step is provided by a spent lithium-ion battery.

[0051] Typically, retired power batteries undergo processes such as discharge, crushing, leaching, and regeneration to recover valuable metal elements. However, it is worth noting that lithium-ion power batteries have stringent requirements, and retired power batteries still retain about 80% of their energy. After deducting the portion that passes inspection and is used for secondary applications, a large amount of energy contained in lithium-ion batteries is wasted during discharge. Therefore, the effective recycling of the remaining energy of waste lithium batteries has significant market potential and carbon emission reduction value.

[0052] Regarding the collection and utilization of residual battery energy, on the one hand, storing and utilizing electrical energy below 1V is quite difficult, as the voltage may rebound after discharging stored energy, posing a safety hazard during the crushing process; on the other hand, even the residual energy in waste batteries within the 1V-3V range is very difficult to recycle. In this embodiment, waste lithium-ion batteries are used as a power source to provide voltage in the anode delithiation and impurity removal step or the cathode lithium replenishment step, which can fully utilize the residual energy of waste lithium-ion batteries that are difficult to store and recycle, and reduce the waste of residual energy.

[0053] In this embodiment, spent lithium-ion batteries are used as the power source. Since the voltage of spent lithium-ion batteries gradually decreases during discharge, maintaining a relatively constant voltage is more difficult. However, this also presents some advantages. For example, the energy from this voltage level can be directly utilized without storing the excess energy for later use. Furthermore, prolonged high voltage can cause the lithium iron phosphate structure to collapse, but short periods of higher voltage can maintain structural stability while removing impurities, which is beneficial for ensuring the performance of subsequently recycled lithium iron phosphate.

[0054] In some embodiments, the cathode lithium replenishment step uses a spent lithium-ion battery discharged to 1V as the power source. The cathode lithium replenishment step ends when the rate of change of the second cathode potential is less than a second preset value within 10 minutes. At this point, almost all the charge in the spent lithium-ion battery is utilized, and at this voltage, lithium ions are more easily inserted into the crystal lattice than other impurity ions, resulting in a higher purity of the recycled cathode material. If a spent lithium-ion battery or a group of spent lithium-ion batteries is discharged to 0.1V before the cathode lithium replenishment step is completed, the battery or battery pack can be replaced before continuing the cathode lithium replenishment step.

[0055] In some implementations, the second preset value is 0.1%.

[0056] In some embodiments, the lithium-replenishing electrolyte includes a soluble lithium salt.

[0057] In some embodiments, the concentration of lithium ions in the lithium-replenishing electrolyte is 0.1 mol / L to 1 mol / L, specifically 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, or any value between 0.1 mol / L and 1 mol / L. The lithium-replenishing electrolyte not only needs to ensure the normal operation of the electrolytic cell but also needs to provide lithium ions to meet the lithium replenishment requirements of the delithiated and impurity-removed waste lithium iron phosphate cathode sheets.

[0058] In some embodiments, the anode delithiation and impurity removal electrolyte contains soluble lithium salts, and after completing the delithiation and impurity removal step, the delithiation and impurity removal electrolyte is used as a lithium replenishment electrolyte in the cathode lithium replenishment step.

[0059] After the lithium removal and impurity removal process is completed, the lithium removed from the anode and some impurities will dissolve in the lithium removal and impurity removal electrolyte. Therefore, the lithium removal and impurity removal electrolyte will contain a large amount of lithium. Using this electrolyte as a lithium replenishment electrolyte in the cathode lithium replenishment process allows the lithium ions in it to be embedded in the spent lithium iron phosphate cathode sheet after lithium removal and impurity removal, thus achieving lithium replenishment and recycling of lithium ions.

[0060] It should be noted that, theoretically, as long as the electrolyte can provide enough lithium ions, it can be reused repeatedly in the anode delithiation and cathode replenishment steps. However, in the anode delithiation and cathode replenishment steps, or in the cathode replenishment steps using waste lithium iron phosphate cathode sheets as the anode, impurities mixed in the lithium iron phosphate will continuously dissolve into the electrolyte. Therefore, after being used as a delithiation and cathode replenishment electrolyte for a long time, the electrolyte should be cleaned or replaced to avoid using an electrolyte with a high impurity content as a replenishment electrolyte. On the one hand, an electrolyte with a high impurity content may inhibit the dissolution of impurities; on the other hand, it is easier for impurities to enter the lithium iron phosphate along with lithium ions during the replenishment process. Both of these factors will increase the impurity content in the regenerated lithium iron phosphate cathode sheet, thereby reducing the performance of the regenerated lithium iron phosphate material.

[0061] In some embodiments, the soluble lithium salt includes at least one of lithium chloride and lithium sulfate.

[0062] In some embodiments, after lithium replenishment at the cathode, the regenerated lithium iron phosphate cathode sheet is dried at a temperature of 55°C-80°C. Specifically, it can be any value among 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or 55°C-80°C.

[0063] In some implementations, when the waste lithium iron phosphate cathode sheet is used as the second anode, the second anode can be replaced if the rate of change of the second anode potential within 10 minutes is less than a third preset value. In the cathode lithium replenishment step, the waste lithium iron phosphate cathode sheet is delithiated, and the delithiated and impurity-removed waste lithium iron phosphate cathode sheet is then replenished with lithium. In order not to affect the delithiation and lithium replenishment, the lithium concentration in the lithium replenishment electrolyte should be maintained at 0.1 to 2 mol / L.

[0064] In some implementations, the third preset value is 0.1%.

[0065] Secondly, this disclosure provides a lithium iron phosphate cathode obtained by the method for regenerating waste lithium iron phosphate cathodes as described in any of the foregoing embodiments.

[0066] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0067] Example 1:

[0068] This embodiment provides a method for regenerating waste lithium iron phosphate cathode sheets, such as... Figure 1 As shown, the specific steps include:

[0069] S1: The recycled waste lithium iron phosphate cathode sheet is placed in an electrolytic cell containing electrolyte, with a platinum electrode as the cathode. An old lithium-ion battery with a voltage of 2.7V is used as the power source to carry out the electrolytic reaction until the battery voltage drops to 1V. The power source is then replaced until the anode potential change rate is less than 0.1% within 10 minutes. This yields a mixed solution of impurities and lithium, and delithiated and deimpurified waste lithium iron phosphate cathode sheets. The waste lithium-ion battery is a waste lithium iron phosphate battery, and the electrolyte is a 0.2mol / L lithium chloride solution.

[0070] S2: Use the delithiated and impurity-removed waste lithium iron phosphate cathode sheet processed in step S1 as the cathode, and the untreated waste lithium iron phosphate cathode sheet as the anode. Use the impurity and lithium mixed solution obtained in S1 as the electrolyte. Connect the waste lithium-ion battery that was discharged to 1V in step S1 to the external circuit. The reaction ends when the cathode potential change rate is less than 0.1% within 10 minutes.

[0071] S3: The obtained regenerated lithium iron phosphate cathode sheet is dried at 60°C to obtain a regenerated lithium iron phosphate cathode sheet with a lithium content of 4.40%.

[0072] S4: Using the positive electrode sheet prepared in step S3 as the positive electrode and graphite as the negative electrode, test the performance. Test the initial discharge specific capacity of the recycled material at a 0.5C rate, and the capacity retention rate after 100 charge-discharge cycles.

[0073] According to the carbon emission calculation method described in patent CN202111267063A, the carbon emission per unit product is calculated to be 0 kg CO2e.

[0074] Example 2:

[0075] This embodiment provides a method for regenerating waste lithium iron phosphate cathode sheets. The only difference from Embodiment 1 is that step S1 is performed at a constant voltage of 2V.

[0076] Example 3:

[0077] This embodiment provides a method for regenerating waste lithium iron phosphate cathode sheets. The only difference from Embodiment 1 is that step S2 is performed at a constant voltage of 0.5V.

[0078] Comparative Example 1:

[0079] This comparative example provides a method for regenerating waste lithium iron phosphate cathode sheets. The only difference from Example 1 is that in S1, a waste lithium-ion battery discharged to 1V is used as the power source.

[0080] Comparative Example 2:

[0081] This comparative example provides a method for regenerating waste lithium iron phosphate cathode sheets. The only difference from Example 1 is that in S2, a waste lithium-ion battery with a voltage of 1V to 3V is used as the power source.

[0082] Comparative Example 3:

[0083] This comparative example provides a method for regenerating waste lithium iron phosphate cathode sheets. The only difference from Comparative Example 1 is that in S1, a waste lithium-ion battery discharged to 1V is used as the power source, while in S2, a waste lithium-ion battery with a voltage of 1V to 3V is used as the power source.

[0084] Comparative Example 4:

[0085] This embodiment provides a method for regenerating waste lithium iron phosphate cathode sheets. The only difference from Embodiment 1 is that step S1 is performed at a constant voltage of 3.5V.

[0086] Comparative Example 5:

[0087] This comparative example provides a method for regenerating waste lithium iron phosphate (LFP) cathode sheets, including ultrasonically treating the waste LFP cathode sheets in NMP at 40°C for 30 min, filtering and drying to obtain waste LFP cathode material. The waste LFP cathode material is mixed with lithium carbonate at a mass ratio of 20:1. After mixing, a certain amount of ethanol is added to form a mixture with a solid-liquid ratio of 80 g / L. The mixture is then ball-milled at 300 rpm for 3 h, and the ethanol is evaporated to obtain a powder. The powder is then calcined at 650°C for 5 h to obtain the regenerated LFP cathode material.

[0088] According to the carbon emission calculation method described in patent CN202111267063A, the carbon emission per unit product is calculated to be 9.76 kg CO. 2e .

[0089] Comparative Example 6:

[0090] This comparative example provides a waste lithium iron phosphate cathode sheet as described in step S1 of Example 1, and tests it.

[0091] Comparative Example 7:

[0092] This comparative example provides a novel lithium iron phosphate cathode sheet prepared for the first time and tests it. (The novel lithium iron phosphate cathode sheet prepared for the first time in this comparative example is obtained by using the decommissioned lithium iron phosphate cathode sheet in the examples).

[0093] The lithium iron phosphate cathode sheets obtained in the above examples and comparative examples were used as the cathodes of simulated batteries. The simulated batteries were assembled in an argon-protected glove box with H2O and O2 contents below 2 ppm (by volume). The anode was a lithium metal sheet, the separator was Celgard 2400, and the electrolyte was 1 mol·L⁻¹. -1 A CR2025 type simulated battery was constructed using LiPF6 / DMC+DEC (volume ratio 1:1). The electrochemical performance of the simulated battery was tested using the Shenzhen Xinwei Battery Testing System at a frequency of 0.3 mA / cm². 2 The charge / discharge current density was used for charging and discharging, and the charge / discharge voltage range was 2.9–3.7V. The resulting electrochemical performance data is shown in the table below.

[0094]

[0095] In Comparative Example 1, a voltage of less than 1V was used during both recycling and regeneration. The voltage was too low during recycling, making it difficult for impurity ions to be removed, which affected the electrochemical performance of the recycled material.

[0096] In Comparative Example 2, a voltage of 1-3V was used during both recycling and regeneration. During regeneration, the voltage was too high, and the intercalation of impurity ions affected the electrochemical performance of the regenerated material.

[0097] Comparative Example 3 uses a voltage below 1V during recovery and a voltage of 1-3V during regeneration. Not only are impurities difficult to remove during recovery, but impurity ions in the electrolyte are also easily embedded during regeneration, affecting electrochemical performance.

[0098] Industrial applicability

[0099] This embodiment utilizes an electrochemical method to regenerate lithium iron phosphate without structural damage. It avoids the large-scale discharge of acidic and alkaline wastewater during wet recycling and the lattice changes caused by aerobic calcination during pyrometallurgical recycling, which can lead to reduced activity of lithium iron phosphate. The process is simple, eliminating the need to peel lithium iron phosphate from the cathode sheet; the regenerated cathode sheet is obtained directly. No additional binders or conductive agents are required in the cathode sheet. Furthermore, the performance of the regenerated lithium iron phosphate cathode material is comparable to that of the initially prepared lithium iron phosphate cathode material, demonstrating promising prospects for industrial applications.

Claims

1. A method for regenerating waste lithium iron phosphate cathode sheets, characterized in that, include: The anode delithiation and impurity removal process involves using waste lithium iron phosphate cathode sheets or pre-delithiated waste lithium iron phosphate cathode sheets as the first anode and an inert electrode as the first cathode. The first cathode and the first anode are placed in a delithiation and impurity removal electrolyte, and a voltage of 1V-3V is applied between the first cathode and the first anode to obtain delithiated and impurity-removed waste lithium iron phosphate cathode sheets. In the anode delithiation and impurity removal step, a waste lithium-ion battery discharged to 2.7V-3V is used as the power source. When the rate of change of the first anode potential is less than a first preset value within 10 minutes, the anode delithiation and impurity removal step ends. The cathode lithium replenishment process uses a delithiated and impurity-removed waste lithium iron phosphate positive electrode as the second cathode and an inert electrode or a waste lithium iron phosphate positive electrode as the second anode. The second cathode and the second anode are placed in a lithium replenishment electrolyte, and a voltage of 0.1V-1V is applied between the second cathode and the second anode. When the second anode is an inert electrode, a regenerated lithium iron phosphate positive electrode is obtained; when the second anode is a waste lithium iron phosphate positive electrode, a regenerated lithium iron phosphate positive electrode and a pre-delithiated waste lithium iron phosphate positive electrode are obtained. In the cathode lithium replenishment step, a waste lithium-ion battery discharged to 1V is used as the power source. When the potential change rate of the second cathode is less than a second preset value within 10 minutes, the cathode lithium replenishment step ends at the preset value.

2. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 1, characterized in that, The voltage in the anode delithiation and impurity removal step is provided by the waste lithium-ion battery.

3. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 1, characterized in that, The first preset value is 0.1%.

4. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 2 or 3, characterized in that, The waste lithium-ion batteries include at least one of waste lithium iron phosphate batteries, waste ternary lithium batteries, waste lithium cobalt oxide batteries, and waste lithium manganese oxide batteries.

5. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 1, characterized in that, The delithiation and impurity removal electrolyte contains 0.1 mol / L to 0.5 mol / L of soluble salt.

6. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 1, characterized in that, The mass fraction of lithium in the regenerated lithium iron phosphate cathode is above 4.40%.

7. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 1, characterized in that, The voltage in the cathode lithium replenishment step is provided by the spent lithium-ion batteries that have undergone the anode delithiation and impurity removal step.

8. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 1, characterized in that, The second preset value is 0.1%.

9. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 1, characterized in that, The lithium replenishing electrolyte includes soluble lithium salts.

10. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 9, characterized in that, The concentration of lithium ions in the lithium-replenishing electrolyte is 0.1 mol / L to 2 mol / L.

11. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 9, characterized in that, The delithiation and impurity removal electrolyte contains soluble lithium salts. After completing the anode delithiation and impurity removal step, the delithiation and impurity removal electrolyte is used as a lithium replenishment electrolyte in the cathode lithium replenishment step.

12. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 9, characterized in that, The soluble lithium salt includes at least one of lithium chloride and lithium sulfate.

13. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 1, characterized in that, After lithium replenishment at the cathode, the regenerated lithium iron phosphate cathode sheet is dried at a temperature of 55℃-80℃.

14. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 1, characterized in that, When a waste lithium iron phosphate cathode sheet is used as the second anode, the second anode is replaced when the rate of change of the second anode potential within 10 minutes is less than the third preset value.

15. The method for regenerating waste lithium iron phosphate cathode sheets according to claim 14, characterized in that, The third preset value is 0.1%.

16. A regenerated lithium iron phosphate cathode obtained by the method for regenerating waste lithium iron phosphate cathodes according to any one of claims 1-15.

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