Method for full-chain integrated regeneration of waste lithium iron phosphate positive electrode sheets, and regenerated lithium iron phosphate positive electrode sheet

Abstract

A method for regeneration of waste lithium iron phosphate positive electrode sheets, and a regenerated lithium iron phosphate positive electrode sheet. By means of an electrochemical mode, the method enables lithium iron phosphate to be regenerated without any damage to the structure thereof; the method avoids the discharge of acid-alkali wastewater in large quantities during a wet recovery process, and also avoids the problem of reduced activity of lithium iron phosphate due to the lattice changes in the lithium iron phosphate caused by aerobic calcination during a pyrogenic recovery process; moreover, the process is simple, lithium iron phosphate does not need to be stripped from positive electrode sheets, a positive electrode sheet is directly obtained after regeneration, and a binder, a conductive agent, etc., in the positive electrode sheet do not need to be additionally replenished; and the performance of a regenerated lithium iron phosphate positive electrode material is equivalent to that of the initially prepared lithium iron phosphate positive electrode material.

Description

Full-chain integrated method for regenerating waste lithium iron phosphate positive electrode sheets and regenerated lithium iron phosphate positive electrode sheets Technical Field

[0001] The present disclosure relates to the technical field of cathode material recycling, and in particular to a method for regenerating waste lithium iron phosphate cathode sheets in a fully integrated chain and a regenerated lithium iron phosphate cathode sheet. Background Art

[0002] The rapid development of new energy vehicles and consumer electronics in recent years has led to a surge in lithium-ion battery shipments, generating a significant amount of waste lithium batteries. It is estimated that retired power batteries from new energy vehicles in China could reach 300,000 tons by 2025. Lithium iron phosphate cathode materials, due to their widespread availability, low price, excellent thermal stability, high cycle performance, and environmental friendliness, are increasingly being used in consumer electronics, electric bicycles, electric vehicles, and energy storage power stations, resulting in a significant amount of waste lithium batteries. Waste lithium batteries contain significant amounts of valuable metals and electrolytes. Improper handling can not only cause environmental pollution but also lead to economic losses.

[0003] Usually, retired power batteries will go through the processes of discharge, crushing, leaching, and regeneration to recover valuable metal elements. Currently, there are two routes for the recycling of waste lithium iron phosphate battery positive electrode materials: wet recycling and fire recycling. In the wet recycling, the stripped positive electrode active materials are treated with acid and then precipitated in steps, which produces a lot of wastewater; the fire recycling crushes and calcines the stripped positive electrode active materials to remove the binder and conductive agent, but this will lead to a decrease in the activity of lithium iron phosphate, and the binder and conductive agent cannot be recovered. Both methods are lengthy and some components such as binders cannot be recycled. Therefore, a method for regenerating waste lithium iron phosphate battery positive electrode materials with a simple process, environmental friendliness, and high component recovery rate is particularly necessary.

[0004] In view of this, the present disclosure is proposed.

[0005] Summary of the Invention

[0006] The purpose of the present disclosure is to provide a method for regenerating waste lithium iron phosphate positive electrode sheets in a full-chain integrated manner and a regenerated lithium iron phosphate positive electrode sheet, which can regenerate the positive electrode material without destroying the structure of the positive electrode material and has a simple process.

[0007] The present disclosure is achieved as follows:

[0008] In a first aspect, the present disclosure provides a method for regenerating waste lithium iron phosphate positive electrode sheets, comprising:

[0009] Anode delithiation and impurity removal: using a waste lithium iron phosphate positive electrode sheet or a pre-delithiation waste lithium iron phosphate positive electrode sheet as a first anode and an inert electrode as a first cathode, placing the first cathode and the first anode in a delithiation and impurity removal electrolyte, and applying a voltage of 1V-3V between the first cathode and the first anode to obtain a delithiation and impurity removal waste lithium iron phosphate positive electrode sheet;

[0010] Cathode lithium replenishment, using the delithiation and impurity-removed waste lithium iron phosphate positive electrode sheet as the second cathode, and the inert electrode or the waste lithium iron phosphate positive electrode sheet as the second anode, placing the second cathode and the second anode in a lithium replenishment electrolyte, and applying a voltage of 0.1V-1V 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-delithiation waste lithium iron phosphate positive electrode sheet are obtained.

[0011] In some embodiments, the voltage in the anode delithiation and impurity removal step is provided by a waste lithium-ion battery.

[0012] In some embodiments, in the anode delithiation and impurity removal step, a waste lithium-ion battery discharged to 1V-3V is used as a power source. When the first anode potential change rate within 10 minutes is less than a first preset value, the anode delithiation and impurity removal step is completed.

[0013] In some embodiments, the first preset value is 0.1%.

[0014] In some embodiments, the waste lithium-ion battery includes at least one of a waste lithium iron phosphate battery, a waste ternary battery, a waste lithium cobalt oxide battery, and a waste lithium manganese oxide battery.

[0015] In some embodiments, the delithiation and impurity-removing electrolyte includes 0.1 mol / L-0.5 mol / L of soluble salt.

[0016] In some embodiments, the mass fraction of lithium in the regenerated lithium iron phosphate positive electrode sheet is greater than 4.40%.

[0017] In some embodiments, the voltage in the cathode lithium replenishment step is provided by spent lithium-ion batteries.

[0018] In some embodiments, in the cathode lithium replenishment step, a waste lithium-ion battery discharged to 1V is used as a power source, and the cathode lithium replenishment step ends when the rate of change of the second cathode potential within 10 minutes is less than a second preset value.

[0019] In some embodiments, the second preset value is 0.1%.

[0020] In some embodiments, the lithium-supplementing electrolyte includes a soluble lithium salt.

[0021] In some embodiments, the concentration of lithium ions in the lithium-supplementing electrolyte is 0.1 mol / L-2 mol / L.

[0022] In some embodiments, the delithiation and impurity removal electrolyte contains a soluble lithium salt, and the anode delithiation and impurity removal electrolyte is used as a lithium replenishing electrolyte to participate in the cathode lithium replenishing step after completing the delithiation and impurity removal step.

[0023] In some embodiments, the soluble lithium salt includes at least one of lithium chloride and lithium sulfate.

[0024] In some embodiments, after the cathode is replenished with lithium, the regenerated lithium iron phosphate positive electrode sheet is dried at a drying temperature of 55° C.-80° C.

[0025] In some embodiments, when a waste lithium iron phosphate positive electrode sheet is used as the second anode, the second anode may be replaced when the rate of change of the second anode potential within 10 minutes is less than a third preset value.

[0026] In some implementations, the third preset value is 0.1%.

[0027] In a second aspect, the present disclosure provides a lithium iron phosphate positive electrode sheet obtained by the method for regenerating waste lithium iron phosphate positive electrode sheets described in any one of the aforementioned embodiments.

[0028] The present disclosure has the following beneficial effects:

[0029] After long-term use, waste lithium iron phosphate positive plates are mixed with some organic and metal impurities, such as electrolyte residues and some impurities introduced during the battery processing. In the method for regenerating waste lithium iron phosphate positive plates provided in this embodiment, these impurities are first removed at a higher voltage. However, when the impurities are removed, lithium is also removed to obtain lithium-deficient lithium iron phosphate. Therefore, the next step is to replenish lithium to the waste lithium iron phosphate positive plates that have been delithiated and impurities removed, so that regenerated lithium iron phosphate positive plates can be obtained.

[0030] This embodiment uses electrochemical means to regenerate lithium iron phosphate without destroying its structure. There is no large-scale discharge of acid and alkaline wastewater during wet recovery, nor is there a problem of lattice changes of lithium iron phosphate due to aerobic calcination during fire recovery, which in turn leads to a decrease in the activity of lithium iron phosphate. The process is simple, and there is no need to peel the lithium iron phosphate from the positive electrode sheet. The positive electrode sheet is directly obtained after regeneration, and no additional adhesives and conductive agents in the positive electrode sheet need to be supplemented. The performance of the regenerated lithium iron phosphate positive electrode material is comparable to that of the lithium iron phosphate positive electrode material prepared for the first time. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0032] FIG1 is a process flow chart of Example 1. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0034] In a first aspect, the present disclosure provides a method for regenerating waste lithium iron phosphate positive electrode sheets, comprising:

[0035] Anode delithiation and impurity removal: using a waste lithium iron phosphate positive electrode sheet or a pre-delithiation waste lithium iron phosphate positive electrode sheet as a first anode and an inert electrode as a first cathode, placing the first cathode and the first anode in a delithiation and impurity removal electrolyte, and applying a voltage of 1V-3V between the first cathode and the first anode to obtain a delithiation and impurity removal waste lithium iron phosphate positive electrode sheet;

[0036] Cathode lithium replenishment, using the delithiation and impurity-removed waste lithium iron phosphate positive electrode sheet as the second cathode, and the inert electrode or the waste lithium iron phosphate positive electrode sheet as the second anode, placing the second cathode and the second anode in a lithium replenishment electrolyte, and applying a voltage of 0.1V-1V 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-delithiation waste lithium iron phosphate positive electrode sheet are obtained.

[0037] After long-term use, waste lithium iron phosphate positive plates are mixed with some organic and metal impurities, such as electrolyte residues and some impurities introduced during the battery processing process. In the method for regenerating waste lithium iron phosphate positive plates provided in this embodiment, these impurities are first removed at a higher voltage. However, the removal of impurities is also accompanied by lithium removal, thus obtaining lithium iron phosphate in a lithium-deficient state; the next step of this embodiment is to replenish lithium to the delithiated and impurity-removed waste lithium iron phosphate positive plates, that is, to obtain regenerated lithium iron phosphate positive plates.

[0038] This embodiment uses electrochemical means to regenerate lithium iron phosphate without destroying its structure. There is no large-scale discharge of acid and alkaline wastewater during wet recovery, nor is there a problem of lattice changes of lithium iron phosphate due to aerobic calcination during fire recovery, which in turn leads to a decrease in the activity of lithium iron phosphate. The process is simple, and there is no need to peel the lithium iron phosphate from the positive electrode sheet. The positive electrode sheet is directly obtained after regeneration, and no additional adhesives and conductive agents in the positive electrode sheet need to be supplemented. The performance of the regenerated lithium iron phosphate positive electrode material is comparable to that of the lithium iron phosphate positive electrode material prepared for the first time.

[0039] In the cathode lithium replenishment step of this embodiment, an inert electrode can be used as the anode, or a waste lithium iron phosphate positive electrode sheet can be used as the anode. When the waste lithium iron phosphate positive electrode sheet is used as the anode, part of the lithium therein can be preliminarily removed. However, due to the difficulty in removing impurities, the pre-delithiated waste lithium iron phosphate positive electrode sheet obtained after the cathode lithium replenishment is completed still contains a large amount of impurities. Therefore, the pre-delithiated waste lithium iron phosphate positive electrode sheet can be used as the anode in the lithium removal and impurity removal step. At a higher voltage, the impurities can be removed more completely, and then transferred back to the cathode lithium replenishment step as the cathode for lithium replenishment to obtain a regenerated lithium iron phosphate positive electrode sheet.

[0040] The inert electrodes in the anode lithium removal and impurity removal step and the cathode lithium replenishment step can both be platinum electrodes.

[0041] In this embodiment, the voltage in the anode delithiation and impurity removal step is 1V-3V, specifically it can be a constant voltage of 1V, 1.5V, 2V, 2.5V, 3V or any value between 1V-3V, or it can be a fluctuating or changing voltage, for example, the voltage gradually decreases from 3V to 1V.

[0042] 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 0.1V, 0.5V, 1V or any value between 0.1V-1V, or it can be a fluctuating voltage, for example, the voltage gradually decreases from 1V to 0.1V.

[0043] In some embodiments, the voltage in the anode delithiation and impurity removal step is provided by a waste lithium-ion battery.

[0044] In some embodiments, in the anode delithiation and impurity removal step, a waste lithium-ion battery discharged to 1V-3V is used as a power source. When the first anode potential change rate within 10 minutes is less than a first preset value, the anode delithiation and impurity removal step is completed.

[0045] If the anode delithiation and impurity removal step is not completed when a waste lithium-ion battery or a group of waste lithium-ion batteries is discharged to a voltage of 1V, the anode delithiation and impurity removal step can be continued after replacing the battery or battery group.

[0046] In some embodiments, the first preset value is 0.1%.

[0047] In some embodiments, the waste lithium-ion batteries include at least one of waste lithium iron phosphate batteries, waste ternary batteries, waste lithium cobalt oxide batteries, and waste lithium manganese oxide batteries, as long as there is residual energy that meets the voltage requirements.

[0048] In some embodiments, the anode delithiation and impurity removal electrolyte includes 0.1 mol / L-0.5 mol / L of soluble salt, specifically 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L or any value between 0.1 mol / L and 0.5 mol / L.

[0049] The soluble salt in this embodiment can specifically be sodium salt, lithium salt, potassium salt, sulfate, chloride salt, etc., which can be one of them or a mixture of two or more, for example, it can be selected from sodium chloride, sodium sulfate, lithium chloride, lithium nitrate, etc.

[0050] In some embodiments, the mass fraction of lithium in the regenerated lithium iron phosphate positive electrode sheet is greater than 4.40%, and the theoretical value of lithium content in lithium iron phosphate is 4.43%. When the lithium content reaches 4.40%, it can be considered that lithium replenishment is completed.

[0051] In some embodiments, the voltage in the cathode lithium replenishment step is provided by spent lithium-ion batteries.

[0052] Typically, retired power batteries undergo a process of discharge, crushing, leaching, and regeneration to recover valuable metal elements. However, it's worth noting that lithium-ion power batteries have stringent requirements, and retired batteries still retain approximately 80% of their energy. Beyond the portion that passes inspection and is destined for secondary use, a significant amount of energy stored in lithium-ion batteries is wasted during discharge. Therefore, effectively recovering the residual energy from spent lithium batteries holds significant market potential and promises significant carbon reduction benefits.

[0053] Regarding the collection and utilization of battery residual energy, on the one hand, it is difficult to store and utilize electrical energy below 1V, and the voltage may rebound after discharging the stored energy, posing a safety hazard during the crushing process. On the other hand, even the residual energy of waste batteries in the range of 1V-3V is very difficult to recover. In this embodiment, waste lithium-ion batteries are used as power sources to provide voltage in the anode lithium removal and impurity removal step or the cathode lithium replenishment step, which can fully utilize the residual energy of waste lithium-ion batteries that is difficult to store and recover, thereby reducing the waste of residual energy.

[0054] In this embodiment, waste lithium-ion batteries are used as the power source. Because the voltage of waste lithium-ion batteries gradually decreases during discharge, constant voltage control is more difficult. However, this also offers some advantages. For example, the energy from this voltage drop can be directly utilized, eliminating the need to store and reuse this excess energy. Furthermore, while sustained high voltage can cause the lithium iron phosphate structure to collapse, short periods of high voltage can maintain structural stability while removing impurities, helping to ensure the performance of the subsequent regenerated lithium iron phosphate.

[0055] In some embodiments, the cathode lithium replenishment step uses a waste lithium-ion battery discharged to 1V as a power source. The cathode lithium replenishment step ends when the rate of change of the second cathode potential is less than a second predetermined value within 10 minutes. At this point, nearly all of the energy in the waste lithium-ion battery is utilized, and at this voltage, lithium ions are more easily embedded in the crystal lattice than other impurity ions, resulting in a higher purity of the regenerated positive electrode material. If the cathode lithium replenishment step is not completed when a waste lithium-ion battery or a group of waste lithium-ion batteries is discharged to a voltage of 0.1V, the battery or battery pack can be replaced and the cathode lithium replenishment step can be continued.

[0056] In some embodiments, the second preset value is 0.1%.

[0057] In some embodiments, the lithium-supplementing electrolyte includes a soluble lithium salt.

[0058] In some embodiments, the lithium ion concentration in the lithium-replenishing electrolyte is 0.1 mol / L-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 is not only required to enable the electrolytic cell to function properly, but also to provide lithium ions to meet the lithium replenishment needs of the cathode delithiation and impurity removal of waste lithium iron phosphate positive electrode sheets.

[0059] In some embodiments, the anode delithiation and impurity removal electrolyte contains a soluble lithium salt, and the delithiation and impurity removal electrolyte is used as a lithium replenishing electrolyte in the cathode lithium replenishing step after completing the delithiation and impurity removal step.

[0060] After the lithium removal and impurity removal steps are completed, the lithium removed at 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 replenishing electrolyte in the cathode lithium replenishing step can allow the lithium ions therein to be embedded in the cathode lithium de-lithiation and impurity removal waste lithium iron phosphate positive electrode sheet, thereby achieving lithium replenishment and allowing the lithium ions to be recovered.

[0061] It should be noted that, in theory, as long as the electrolyte can provide the required lithium ions, it can be used repeatedly in the anode delithiation and impurity removal step and the cathode lithium replenishment step. However, in the anode delithiation and impurity removal step or the cathode lithium replenishment step using waste lithium iron phosphate positive electrode sheets as the anode, since the impurities contained in the lithium iron phosphate will continue to dissolve into the electrolyte, the electrolyte can be removed or replaced after being used as a delithiation and impurity removal electrolyte for a long time to avoid using an electrolyte with a high impurity content as a lithium 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 lithium ions to enter the lithium iron phosphate during the lithium replenishment process, which will increase the content of impurities in the regenerated lithium iron phosphate positive electrode sheet, thereby resulting in a decrease in the performance of the regenerated lithium iron phosphate material.

[0062] In some embodiments, the soluble lithium salt includes at least one of lithium chloride and lithium sulfate.

[0063] In some embodiments, after the cathode is replenished with lithium, the regenerated lithium iron phosphate positive electrode sheet is dried at a drying temperature of 55°C-80°C, specifically, it can be 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or any value between 55°C and 80°C.

[0064] In some embodiments, when the waste lithium iron phosphate positive electrode sheet is used as the second anode, when the rate of change of the second anode potential within 10 minutes is less than a third preset value, the second anode can be replaced. In the cathode lithium replenishment step, the waste lithium iron phosphate positive electrode sheet is delithiated, and the waste lithium iron phosphate positive electrode sheet is replenished with lithium after delithiation and impurity removal. In order not to affect the delithiation and replenishment of lithium, the lithium concentration in the lithium replenishment electrolyte should be maintained at 0.1-2 mol / L.

[0065] In some implementations, the third preset value is 0.1%.

[0066] In a second aspect, the present disclosure provides a lithium iron phosphate positive electrode sheet obtained by the method for regenerating waste lithium iron phosphate positive electrode sheets described in any one of the aforementioned embodiments.

[0067] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0068] Example 1:

[0069] This embodiment provides a method for regenerating waste lithium iron phosphate positive electrode sheets, as shown in FIG1 , which specifically includes the following steps:

[0070] S1: The recycled waste lithium iron phosphate cathode sheet is used as the anode and the platinum electrode is used as the cathode in an electrolytic cell filled with an electrolyte. A waste lithium-ion battery with a voltage of 2.7V is used as the power source. The electrolysis reaction is carried out until the battery voltage drops to 1V. The power source is replaced until the rate of change of the anode potential is less than 0.1% within 10 minutes, thereby obtaining a mixed solution of impurities and lithium and a waste lithium iron phosphate cathode sheet that has been de-lithiated and de-impurified. The waste lithium-ion battery is a waste lithium iron phosphate battery, and the electrolyte is a 0.2 mol / L lithium chloride solution.

[0071] S2: Use the delithiation and deimpurity-removed waste lithium iron phosphate positive electrode sheet treated in step S1 as the cathode, and the waste lithium iron phosphate positive electrode sheet not treated in S1 as the anode, use the impurity and lithium mixed solution obtained in S1 as the electrolyte, and connect the waste lithium-ion battery discharged to 1V in step S1 to the battery. Power on until the cathode potential change rate is less than 0.1% within 10 minutes, and the reaction ends.

[0072] S3: Drying the obtained regenerated lithium iron phosphate positive electrode sheet at 60° C. to obtain a regenerated lithium iron phosphate positive electrode sheet, wherein the lithium content in the regenerated lithium iron phosphate positive electrode sheet is 4.40%.

[0073] S4: Using the positive electrode sheet prepared in step S3 as the positive electrode and graphite as the negative electrode, the performance of the recycled material was tested. The initial discharge specific capacity of the recycled material at a 0.5C rate and the capacity retention after 100 charge and discharge cycles were tested.

[0074] According to the carbon emission calculation method described in patent CN202111267063A, the carbon emissions per unit product are calculated to be 0kgCO2e.

[0075] Example 2:

[0076] This embodiment provides a method for regenerating waste lithium iron phosphate positive electrode sheets, which differs from Example 1 only in that step S1 is performed at a constant voltage of 2V.

[0077] Example 3:

[0078] This embodiment provides a method for regenerating waste lithium iron phosphate positive electrode sheets, which differs from Example 1 only in that step S2 is performed at a constant voltage of 0.5V.

[0079] Comparative Example 1:

[0080] This comparative example provides a method for regenerating waste lithium iron phosphate positive electrode sheets, which differs from Example 1 only in that in S1 , a waste lithium-ion battery discharged to 1V is used as a power source.

[0081] Comparative Example 2:

[0082] This comparative example provides a method for regenerating waste lithium iron phosphate positive electrode sheets, which differs from Example 1 only in that a waste lithium-ion battery with a voltage of 1V to 3V is used as a power source in S2.

[0083] Comparative Example 3:

[0084] This comparative example provides a method for regenerating waste lithium iron phosphate positive electrode 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, and in S2, a waste lithium ion battery with a voltage of 1V to 3V is used as the power source.

[0085] Comparative Example 4:

[0086] This embodiment provides a method for regenerating waste lithium iron phosphate positive electrode sheets, which differs from Example 1 only in that step S1 is performed at a constant voltage of 3.5V.

[0087] Comparative Example 5:

[0088] This comparative example provides a method for regenerating waste lithium iron phosphate cathode sheets. The method includes ultrasonically treating the waste lithium iron phosphate cathode sheets in NMP at 40°C for 30 minutes, filtering and drying the sheets to obtain waste lithium iron phosphate cathode material. The waste lithium iron phosphate 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-to-liquid ratio of 80 g / L. The mixture is then ball-milled at 300 rpm for 3 hours, and the ethanol is evaporated to obtain a powdered mixture. The powder is then calcined at 650°C for 5 hours to obtain the regenerated lithium iron phosphate cathode material.

[0089] According to the carbon emission calculation method described in patent CN202111267063A, the carbon emission per unit product is 9.76kgCO 2e .

[0090] Comparative Example 6:

[0091] This comparative example provides a waste lithium iron phosphate positive electrode sheet described in step S1 of Example 1 and tests it.

[0092] Comparative Example 7:

[0093] This comparative example provides a newly prepared, brand-new lithium iron phosphate positive electrode sheet and tests it. (The newly prepared, brand-new lithium iron phosphate positive electrode sheet provided in this comparative example is the spent lithium iron phosphate positive electrode sheet obtained in the example after it has been retired from use).

[0094] The lithium iron phosphate positive electrode obtained in the above examples and comparative examples was used as the positive electrode of the simulated battery. The simulated battery was assembled in an argon-protected glove box. The contents of H2O and O2 were less than 2 ppm (volume). The negative electrode was a metal lithium sheet, the separator was Celgard 2400, and the electrolyte was 1 mol·L -1 LiPF6 / DMC+DEC (volume ratio of 1:1) was used to form a CR2025 type simulated battery. The electrochemical performance test of the simulated battery was carried out on the Shenzhen Xinweier battery testing system at 0.3 mA / cm 2 The charge and discharge current density is charged and discharged, and the charge and discharge voltage range is 2.9~3.7V. The electrochemical performance data of the product are shown in the following table.

[0095] In comparative example 1, a voltage below 1 V was used during both recovery and regeneration. The voltage during recovery was too low, making it difficult for impurity ions to escape, thus affecting the electrochemical properties of the regenerated material.

[0096] In comparative example 2, a voltage of 1-3 V was used during both recovery and regeneration. During regeneration, the voltage was too high, and the insertion of foreign ions affected the electrochemical properties of the regenerated material.

[0097] In comparative example 3, a voltage below 1V is used during recovery and a voltage of 1-3V is used during regeneration. Not only is it difficult to remove impurities during the recovery process, but it is also easy for miscellaneous ions in the electrolyte to be embedded during the regeneration process, affecting the electrochemical performance. Industrial Applicability

[0098] This embodiment uses electrochemical means to regenerate lithium iron phosphate without destroying its structure. There is no large-scale discharge of acid and alkaline wastewater during wet recovery, nor is there a problem of lattice changes of lithium iron phosphate due to aerobic calcination during fire recovery, which in turn leads to a decrease in the activity of lithium iron phosphate. The process is simple, and there is no need to peel the lithium iron phosphate from the positive electrode sheet. The positive electrode sheet is directly obtained after regeneration, and no additional adhesives and conductive agents in the positive electrode sheet are required. The performance of the regenerated lithium iron phosphate positive electrode material is comparable to that of the lithium iron phosphate positive electrode material prepared for the first time, and it has good industrial application prospects.

Claims

1. A method for regenerating waste lithium iron phosphate positive electrode sheets, characterized in that: include: Anode delithiation and impurity removal, using a waste lithium iron phosphate positive electrode sheet or a pre-delithiation waste lithium iron phosphate positive electrode sheet as the first anode and an inert electrode as the first cathode, placing the first cathode and the first anode in a delithiation and impurity removal electrolyte, and applying a voltage of 1V-3V between the first cathode and the first anode to obtain a delithiation and impurity removal waste lithium iron phosphate positive electrode sheet; The cathode is lithium-replenished, and the waste lithium iron phosphate positive electrode sheet that has been de-lithiated and impurities removed is used as the second cathode, and the inert electrode or the waste lithium iron phosphate positive electrode sheet is used as the second anode. The second cathode and the second anode are placed in a lithium-replenished 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-de-lithiated waste lithium iron phosphate positive electrode sheet are obtained.

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

3. The method for regenerating waste lithium iron phosphate positive electrode sheets according to claim 1 or 2, characterized in that: In the anode delithiation and impurity removal step, a waste lithium-ion battery discharged to 1V-3V is used as a power source. When the rate of change of the first anode potential within 10 minutes is less than a first preset value, the anode delithiation and impurity removal step is completed.

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

5. The method for regenerating waste lithium iron phosphate positive electrode sheets according to any one of claims 2 to 4, characterized in that: The waste lithium-ion batteries include at least one of waste lithium iron phosphate batteries, waste ternary batteries, waste lithium cobalt oxide batteries, and waste lithium manganese oxide batteries.

6. The method for regenerating waste lithium iron phosphate positive electrode sheets according to any one of claims 1 to 5, characterized in that: The de-lithiation and impurity-removing electrolyte includes 0.1 mol / L-0.5 mol / L of soluble salt.

7. The method for regenerating waste lithium iron phosphate positive electrode sheets according to any one of claims 1 to 6, characterized in that: The mass fraction of lithium in the regenerated lithium iron phosphate positive electrode sheet is greater than 4.40%.

8. The method for regenerating waste lithium iron phosphate positive electrode sheets according to any one of claims 1 to 7, characterized in that: The voltage in the cathode lithium replenishment step is provided by the waste lithium-ion battery that has undergone the anode lithium removal and impurity removal step.

9. The method for regenerating waste lithium iron phosphate positive electrode sheets according to any one of claims 1 to 8, characterized in that: In the cathode lithium replenishment step, a waste lithium-ion battery discharged to 1V is used as a power source. When the rate of change of the second cathode potential within 10 minutes is less than a second preset value, the cathode lithium replenishment step ends at a preset value.

10. The method for regenerating waste lithium iron phosphate positive electrode sheets according to claim 9, characterized in that: The second preset value is 0.1%.

11. The method for regenerating waste lithium iron phosphate positive electrode sheets according to any one of claims 1 to 10, characterized in that: The lithium-supplementing electrolyte includes a soluble lithium salt.

12. The method for regenerating waste lithium iron phosphate positive electrode sheets according to claim 11, characterized in that: The concentration of lithium ions in the lithium-supplementing electrolyte is 0.1 mol / L-2 mol / L.

13. The method for regenerating waste lithium iron phosphate positive electrode sheets according to claim 11 or 12, characterized in that: The lithium removal and impurity removal electrolyte contains soluble lithium salts. After completing the anode lithium removal and impurity removal step, the lithium removal and impurity removal electrolyte is used as a lithium replenishment electrolyte to participate in the cathode lithium replenishment step.

14. The method for regenerating waste lithium iron phosphate positive electrode sheets according to any one of claims 11 to 13, characterized in that: The soluble lithium salt includes at least one of lithium chloride and lithium sulfate.

15. The method for regenerating waste lithium iron phosphate positive electrode sheets according to any one of claims 1 to 14, characterized in that: After the cathode is replenished with lithium, the regenerated lithium iron phosphate positive electrode sheet is dried at a drying temperature of 55° C.-80° C.

16. The method for regenerating waste lithium iron phosphate positive electrode sheets according to any one of claims 1 to 15, characterized in that: When the waste lithium iron phosphate positive electrode sheet is used as the second anode, when the rate of change of the second anode potential within 10 minutes is less than the third preset value, the second anode is replaced.

17. The method for regenerating waste lithium iron phosphate positive electrode sheets according to claim 16, characterized in that: The third preset value is 0.1%.

18. A regenerated lithium iron phosphate positive electrode sheet obtained by the method for regenerating a waste lithium iron phosphate positive electrode sheet according to any one of claims 1 to 17.

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