Regeneration method of retired lithium battery positive electrode material, regenerated positive electrode material, lithium ion battery and electric device

Abstract

The invention provides a regeneration method of a retired lithium battery positive electrode material, a regenerated positive electrode material, a lithium ion battery and an electric device, and relates to the technical field of waste lithium battery recovery. The regeneration method comprises the following steps: carrying out primary calcination on a decommissioned positive plate in an oxygen-containing atmosphere to obtain decommissioned positive electrode powder; wherein a positive electrode active material in the retired positive plate comprises lithium-containing transition metal phosphate, and retired positive electrode powder contains an aluminum element; mixing the retired positive electrode powder with a lithium source, an organic carbon source and a phosphorus source to obtain a mixed material; and carrying out secondary calcination on the mixed material in a protective atmosphere to obtain the regenerated positive electrode material with the carbon / aluminum phosphate mixed coating layer. According to the regeneration method, the initial discharge gram capacity and the high-temperature cycle performance of the lithium ion battery prepared from the regenerated positive electrode material can be improved while aluminum-containing impurities are removed.

Description

Technical Field

[0001] This application relates to the field of waste lithium battery recycling technology, and in particular to a method for regenerating cathode material of retired lithium batteries, the regenerated cathode material, lithium-ion batteries and electrical devices. Background Technology

[0002] Lithium-ion battery cathodes typically consist of aluminum foil current collectors, conductive carbon, and binders. During recycling, conductive carbon and binders can be removed relatively completely using high-temperature methods. However, the recycled cathode materials inevitably contain a certain amount of elemental aluminum and aluminum-containing compound impurities. The presence of these impurities has an adverse effect on the repair and utilization of cathode materials, especially reducing the initial discharge capacity and high-temperature cycling performance of the recycled cathode materials. Summary of the Invention

[0003] This application is made in view of the above-mentioned issues, and its purpose is to provide a method for regenerating retired lithium battery cathode materials, regenerated cathode materials, lithium-ion batteries, and electrical devices, which can improve the electrochemical performance of regenerated cathode materials while removing aluminum-containing impurities.

[0004] The first aspect of this application provides a method for regenerating retired lithium-ion battery cathode materials, comprising the following steps: calcining a retired cathode sheet in an oxygen-containing atmosphere to obtain retired cathode powder. The cathode active material in the retired cathode sheet includes a lithium-containing transition metal phosphate, and the retired cathode powder contains aluminum. The retired cathode powder is mixed with a lithium source, an organic carbon source, and a phosphorus source to obtain a mixture. The mixture is then calcined a second time in a protective atmosphere to obtain a regenerated cathode material with a carbon / aluminum phosphate mixed coating.

[0005] In the aforementioned technical solutions, retired cathode sheets typically include an aluminum foil current collector, a cathode active material located on the surface of the aluminum foil current collector, a binder, and conductive carbon. While conventional high-temperature processing can remove the binder and conductive carbon to some extent, aluminum impurities inevitably remain in the cathode powder when the aluminum foil current collector and cathode powder are separated. Furthermore, after high-temperature treatment, some elemental aluminum is oxidized, resulting in the presence of aluminum-containing compound impurities such as alumina. These elemental aluminum and aluminum-containing compound impurities are difficult to remove or utilize, and also affect the electrochemical performance of the regenerated cathode material. The regeneration method for retired lithium-ion battery cathode materials provided in this application first calcines the retired cathode sheet in an oxygen-containing atmosphere, which can fully remove conductive carbon, binder, and residual electrolyte, while effectively separating the aluminum foil current collector and cathode powder to obtain retired cathode powder containing aluminum. In this retired cathode powder, the lithium content is relatively low. By adding a lithium source and an organic carbon source, along with a certain amount of phosphorus source, and then performing a second calcination, the lithium source can be effectively replenished to obtain regenerated lithium-containing transition metal phosphate cathode material. The organic carbon source can form a uniform carbon coating layer on the surface of the regenerated cathode material and also act as a reducing agent to inhibit the oxidation of transition metal ions, thus achieving composition control. The additional phosphorus source can react with aluminum-containing compound (e.g., alumina) impurities to generate aluminum phosphate (or / and lithium aluminum phosphate or / and lithium iron phosphate aluminum). The aluminum phosphate mixed with carbon forms a coating layer on the surface of the regenerated cathode material particles, which can effectively improve the lithium-ion transport rate, enhance the initial discharge capacity, and improve high-temperature cycling performance. The combination of phosphorus source and organic carbon source can completely reduce the trace amounts of high-valence transition metal ions oxidized during the first sintering process to low-valence ions. Furthermore, during the second calcination process, some elemental aluminum can be doped into the near-surface or bulk phase of the regenerated cathode material, which can effectively broaden the lithium-ion transport channels. Therefore, the method for regenerating retired lithium battery cathode materials provided in this application effectively improves the electrochemical performance of the regenerated cathode materials while removing aluminum impurities.

[0006] In some embodiments, the molar ratio of lithium, transition metals, and phosphorus in the decommissioned cathode powder is (0.7–0.9):(0.98–0.99):1. Since the lithium ion content in the cathode sheet is lost during the insertion and extraction cycles of a lithium battery, the decommissioned cathode powder obtained in this application is lithium-deficient. Lithium needs to be added before secondary calcination. Furthermore, the phosphorus in the decommissioned cathode powder in this application is relatively saturated so that the subsequently added phosphorus source can react with aluminum to form aluminum phosphate, which can then combine with carbon to form a composite coating layer, thereby improving the electrochemical performance of the regenerated cathode material.

[0007] In some implementations, lithium in the lithium source exists in ionic form. The presence of lithium ions in the lithium source allows for efficient replenishment of the active lithium content by entering the crystal lattice of the regenerated cathode material.

[0008] In some embodiments, the molar ratio of lithium to transition metal elements in the mixture is (1-1.08):1. By controlling the amount of lithium source added, the molar ratio of lithium to transition metal elements in the recycled cathode material can be controlled. This allows for sufficient lithium replenishment while maintaining an appropriate amount of lithium, resulting in lithium-ion batteries prepared from the recycled cathode material exhibiting high initial discharge capacity and good high-temperature cycling performance.

[0009] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium dihydrogen phosphate, lithium phosphate, lithium acetate, lithium hydroxide, or lithium oxalate. All of the above lithium sources can replenish lithium in decommissioned cathode powder to obtain recycled lithium-containing transition metal phosphate cathode material.

[0010] In some embodiments, the organic carbon source includes at least one selected from glucose, sucrose, fructose, polyacrylonitrile, pitch, phenolic resin, starch, citric acid, polyvinyl alcohol, or polypropylene. Using these organic carbon sources allows for the formation of a uniform carbon coating layer on the surface of the regenerated cathode material, thereby improving conductivity.

[0011] In some embodiments, the amount of organic carbon source added is 10wt% to 15wt% of the mass of the decommissioned cathode powder. By controlling the amount of organic carbon source added, a uniform and appropriately thick carbon coating layer can be formed on the surface of the regenerated cathode material particles, which can effectively improve the conductivity of the regenerated cathode material.

[0012] In some implementations, the aluminum content in the decommissioned cathode powder is 500 ppm to 2000 ppm. By measuring the aluminum content in the decommissioned cathode powder, the amount of phosphorus source added subsequently can be precisely controlled, ensuring that aluminum impurities are removed as completely as possible through reaction.

[0013] In some embodiments, the phosphorus source includes phosphates. Phosphates can provide phosphate ions, which react with aluminum-containing compound impurities during secondary sintering to generate aluminum phosphate (or / and lithium aluminum phosphate or / and lithium iron phosphate aluminum).

[0014] In some embodiments, the molar ratio of phosphorus source to aluminum in the decommissioned cathode powder is (1-1.1):1. By controlling the molar ratio of phosphorus source to aluminum, the phosphorus source and aluminum can react fully and completely, preventing excess phosphorus or aluminum impurities from affecting the electrochemical performance of the regenerated cathode material.

[0015] In some embodiments, the phosphorus source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, or lithium dihydrogen phosphate. By selecting these phosphorus sources, it is possible to make the phosphorus source chemically react with aluminum without introducing impurities.

[0016] In some embodiments, the calcination temperature is 350°C to 600°C, and the time is 1 hour to 10 hours. By controlling the calcination at a lower temperature, not exceeding the melting point of the aluminum foil (approximately 650°C), the binder and conductive carbon can be completely removed, the melting of the aluminum foil can be prevented from affecting the subsequent stripping of the positive electrode powder and introducing more metal impurities, and energy consumption can also be reduced to a certain extent.

[0017] In some embodiments, the volume percentage of oxygen in the oxygen-containing atmosphere is not less than 10%. By controlling the oxygen content in the oxygen-containing atmosphere, it is possible to completely remove the binder, conductive carbon, and some other residual electrolytes during a single calcination process.

[0018] In some embodiments, the secondary calcination temperature is 500℃~750℃, and the time is 8h~16h. By controlling the temperature and time of the secondary calcination within a suitable range, lithium replenishment can be effectively achieved while preventing excessive growth of the primary particles, which would result in a small specific surface area and affect the lithium-ion transport efficiency. Furthermore, it also allows for the complete reduction of high-valence transition metal ions oxidized during the primary calcination process.

[0019] In some embodiments, the protective atmosphere is an inert atmosphere or a reducing atmosphere. Secondary sintering under such a protective atmosphere, combined with an organic carbon source and a phosphorus source, can prevent oxidation reactions and reduce high-valence transition metal ions oxidized during the primary calcination process to low-valence ions.

[0020] In some implementations, the mixing method is ball milling or sand milling. By using ball milling or sand milling, the particle size of the decommissioned cathode powder can be reduced, the sintering performance can be improved, and the decommissioned cathode powder can be fully and uniformly mixed with the lithium source, organic carbon source and phosphorus source.

[0021] In some embodiments, the mixing method is sand milling, with a milling speed of 1000 rpm to 6000 rpm and a time of 0.5 h to 4 h. Sand milling can make the components more uniformly mixed, the particle size appropriate, and the carbon coating layer uniformly formed on the surface of the regenerated cathode material.

[0022] In some embodiments, the mixing step is followed by spray drying. Spray-dried material particles have uniformity and good flowability, which is beneficial for subsequent secondary calcination and allows the subsequent organic carbon source and the generated aluminum phosphate to form a uniformly mixed coating layer.

[0023] In some embodiments, the lithium-containing transition metal phosphate has the chemical composition LiM. xPO4, M includes at least one of Fe, Co, Mn, Ni, Cu, Mg, Al, Zn, Cd, Sc, Ti, V, Cr, Y, La, Ce, Nd, Eu, Gd, or Tb, and 0.5 ≤ x ≤ 1. The regeneration method for retired lithium battery cathode materials provided in this application is applicable to the recycling and regeneration of various lithium transition metal phosphate lithium batteries.

[0024] In some embodiments, the lithium-containing transition metal phosphate includes at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, or lithium vanadium iron phosphate. These commonly used lithium battery cathode materials can all be efficiently recycled using this regeneration method.

[0025] The second aspect of this application provides a recycled cathode material, prepared using the recycling method for retired lithium-ion battery cathode materials provided in the first aspect of this application. Because the recycled cathode material removes aluminum impurities and has a carbon / aluminum phosphate mixed coating layer on its surface, the resulting lithium-ion battery exhibits high initial discharge capacity and good high-temperature cycling performance.

[0026] A third aspect of this application provides a lithium-ion battery, including the recycled cathode material provided in the second aspect of this application. Compared to recycled cathode materials obtained using conventional recycling methods, the lithium-ion battery of this application uses a recycled cathode material with a carbon / aluminum phosphate mixed coating layer, resulting in better electrochemical performance.

[0027] A fourth aspect of this application provides an electrical device including the lithium-ion battery provided in the third aspect of this application. Attached Figure Description

[0028] Figure 1 This is a process flow diagram of a method for regenerating retired lithium battery cathode materials according to one embodiment of this application.

[0029] Figure 2 This is a schematic diagram of a lithium-ion battery according to one embodiment of this application.

[0030] Figure 3 for Figure 2 An exploded view of a lithium-ion battery according to an embodiment of this application is shown.

[0031] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application.

[0032] Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0033] Figure 6 for Figure 5 An exploded view of a battery pack according to one embodiment of this application is shown.

[0034] Figure 7 This is a schematic diagram of an electrical device using a lithium-ion battery as a power source according to an embodiment of this application.

[0035] Figure 8 This is an X-ray diffraction (XRD) pattern of the decommissioned cathode powder obtained in Example 1 of this application.

[0036] Figure 9 This is an X-ray diffraction (XRD) pattern of the regenerated cathode material with a carbon / aluminum phosphate mixed coating obtained in Example 1 of this application.

[0037] Figure 10 The images shown are scanning electron microscope (SEM) images and elemental X-ray energy dispersive spectroscopy (EDS) images of the regenerated cathode material with a carbon / aluminum phosphate mixed coating obtained in Example 1 of this application; wherein, Figure 10 A is a SEM image of the regenerated cathode material with a carbon / aluminum phosphate mixed coating layer provided in Embodiment 1 of this application; Figure 10 B is Figure 10 EDS image of P element in the recycled cathode material of A; Figure 10 C is Figure 10 EDS image of Fe element in the regenerated cathode material of A; Figure 10 D is Figure 10 EDS image of O element in the regenerated cathode material of A; Figure 10 E is Figure 10 EDS image of C element in the recycled cathode material of A; Figure 10 F is Figure 10 EDS image of Al element in the recycled cathode material of A.

[0038] Explanation of reference numerals in the attached figures:

[0039] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Lithium-ion battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0040] The following detailed description, with appropriate reference to the accompanying drawings, discloses a method for regenerating the cathode material of retired lithium-ion batteries, the regenerated cathode material, the lithium-ion battery, and embodiments of an electrical device. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions of identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0041] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0043] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0044] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0045] Retired lithium-ion battery cathode sheets typically consist of aluminum foil current collectors, conductive carbon, and binders. During the recycling process, while conductive carbon and binders can be removed relatively completely using high-temperature methods, some aluminum in the aluminum foil current collectors will be partially embedded in the cathode powder or oxidized to aluminum oxide, making it difficult to remove using conventional physical methods such as sieving, flotation, and magnetic adsorption. As a result, the recycled cathode material inevitably contains a certain amount of elemental aluminum and aluminum-containing compound impurities. The presence of these impurities has an adverse effect on the repair and utilization of cathode materials, especially significantly reducing the initial discharge capacity and high-temperature cycle performance of lithium-ion batteries.

[0046] Based on this, the first aspect of the present application provides a method for regenerating retired lithium battery cathode materials. Figure 1 This is a process flow diagram of a method for regenerating retired lithium battery cathode materials according to an embodiment of this application. The regeneration method includes the following steps:

[0047] S110 involves calcining retired cathode sheets in an oxygen-containing atmosphere to obtain retired cathode powder; wherein the cathode active material in the retired cathode sheets includes lithium transition metal phosphates, and the retired cathode powder contains aluminum.

[0048] It should be noted that dismantling and processing retired lithium batteries can yield retired positive electrode plates, retired negative electrode plates, and separators. Among these, the retired positive electrode plates are the raw material source of this application, and the retired negative electrode plates and separators can also be recycled for resource utilization. This application does not impose any restrictions on these components.

[0049] In this embodiment, the retired positive electrode sheet includes an aluminum foil current collector and a positive electrode film layer located on the surface of the aluminum foil current collector. The positive electrode film layer includes a positive electrode active material, conductive carbon, and a binder.

[0050] Among them, the positive electrode active material includes lithium-containing transition metal phosphates, whose chemical composition can be LiM x PO4, M includes at least one of Fe, Co, Mn, Ni, Cu, Mg, Al, Zn, Cd, Sc, Ti, V, Cr, Y, La, Ce, Nd, Eu, Gd, and Tb, with 0.5 ≤ x ≤ 1. As examples, lithium-containing transition metal phosphates include lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, and lithium vanadium iron phosphate. These commonly used lithium battery cathode materials can all be efficiently recycled using this regeneration method.

[0051] Conductive carbon may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0052] In step S110, a single calcination under an oxygen-containing atmosphere degrades the binder and completely removes the conductive carbon, effectively separating the aluminum foil current collector and the positive electrode powder. In some embodiments, after the single calcination step, the process may further include: peeling the positive electrode powder from the aluminum foil current collector and vibrating sieving. After the single calcination under an oxygen-containing atmosphere, the powder and aluminum foil current collector can be easily peeled off, and vibrating sieving can further remove some residual aluminum foil or other impurities.

[0053] In this embodiment, the calcination temperature is 350℃~600℃, and the time is 1h~10h. As an example, the calcination temperature can be 350℃, 500℃, 600℃, etc., and the calcination time can be 1h, 3h, 5h, 10h, etc. Controlling the calcination time at a relatively low temperature, not exceeding the melting point of the aluminum foil current collector (approximately 650℃), ensures complete removal of the binder and conductive carbon from the decommissioned positive electrode sheet, prevents the aluminum foil from melting and affecting subsequent positive electrode powder peeling and introducing more metal impurities, and also reduces energy consumption to some extent.

[0054] In some embodiments, the volume percentage of oxygen in the oxygen-containing atmosphere is not less than 10%. Preferably, the volume percentage of oxygen in the oxygen-containing atmosphere is 10% to 21%. An oxygen content within a suitable range allows for the complete removal of binders, conductive carbon, and some other residual electrolytes during a single calcination process. Optionally, the oxygen-containing atmosphere is air, water vapor, a mixture of oxygen and an inert gas, etc. As an example, the oxygen-containing atmosphere is air with an oxygen content of approximately 21%.

[0055] Elemental analysis of lithium, transition metals, and phosphorus in decommissioned cathode powder is performed. In this embodiment, the molar ratio of lithium, transition metals, and phosphorus in the decommissioned cathode powder is (0.7–0.9):(0.98–0.99):1. As an example, the molar ratio of lithium, transition metals, and phosphorus in the decommissioned cathode powder can be 0.88:0.994:1, 0.7:0.98:1, 0.7:0.99:1, etc.

[0056] It should be noted that, since the lithium ion content in the positive electrode sheet will be lost during the intercalation and deintercalation cycle of lithium batteries, the retired positive electrode powder obtained in this application embodiment is lithium-deficient. Lithium needs to be added before secondary calcination. In addition, the phosphorus in the retired positive electrode powder in this application is relatively saturated so that the phosphorus source added later can react with aluminum to form aluminum phosphate, so that aluminum phosphate can combine with carbon to form a composite coating layer to improve the electrochemical performance of the recycled positive electrode material.

[0057] Elemental analysis of aluminum in decommissioned cathode powder revealed an aluminum content ranging from 500 ppm to 2000 ppm. For example, the aluminum content in decommissioned cathode powder could be 500 ppm, 1000 ppm, 1500 ppm, or 2000 ppm. By determining the aluminum content in the decommissioned cathode powder, the amount of phosphorus source added subsequently can be precisely controlled, ensuring that aluminum impurities are removed as completely as possible through reaction.

[0058] Elemental detection can be performed using inductively coupled plasma atomic emission spectrometry (ICP). The testing method includes: qualitative analysis of the types of elements in the sample and quantitative determination of the molar proportions of elements in the material using ICP-OES with a Thermo ICAP7400 instrument. Aqua regia is prepared by mixing concentrated hydrochloric acid and concentrated nitric acid in a 1:1 volume ratio. A certain amount of material is dissolved in the aqua regia to prepare a low-concentration solution. The proportions of elements in the solid sample are obtained by measuring the concentrations of each ion in the solution using ICP.

[0059] S120 involves mixing retired cathode powder with a lithium source, an organic carbon source, and a phosphorus source to obtain a mixed material.

[0060] In some implementations, lithium in the lithium source exists in ionic form. The presence of lithium ions in the lithium source allows for efficient replenishment of the active lithium content by entering the crystal lattice of the regenerated cathode material.

[0061] In some embodiments, the molar ratio of lithium to transition metal elements in the mixture is (1 to 1.08):1. For example, the molar ratio of lithium to transition metal elements can be 1:1, 1.02:1, 1.05:1, 1.08:1, etc. By controlling the amount of lithium source added, the molar ratio of lithium to transition metal elements in the recycled cathode material can be controlled. This ensures sufficient lithium replenishment while maintaining an appropriate amount of lithium, resulting in a recycled cathode material with high specific capacity and good cycle performance.

[0062] The lithium source includes at least one of lithium carbonate, lithium dihydrogen phosphate, lithium phosphate, lithium acetate, lithium hydroxide, or lithium oxalate. All of the above lithium sources can be used to replenish lithium in decommissioned cathode powder to obtain recycled lithium-containing transition metal phosphate cathode materials.

[0063] In some embodiments, the organic carbon source includes at least one selected from glucose, sucrose, fructose, polyacrylonitrile, pitch, phenolic resin, starch, citric acid, polyvinyl alcohol, or polypropylene. By selecting these organic carbon sources, a uniformly coated carbon layer can be formed on the surface of the regenerated cathode material, thereby improving conductivity.

[0064] In some embodiments, the amount of organic carbon source added is 10wt% to 15wt% of the mass of the decommissioned cathode powder. For example, the amount of organic carbon source added can be 10wt%, 12wt%, 15wt%, etc., of the mass of the decommissioned cathode powder. By controlling the amount of organic carbon source added, a uniform and appropriately thick carbon coating layer can be formed on the surface of the regenerated cathode, effectively improving the conductivity of the regenerated cathode material and avoiding excessive coating that could affect the lithium-ion diffusion rate of the cathode material.

[0065] In some embodiments, the phosphorus source includes phosphates. Phosphates can provide phosphate ions, which react with aluminum-containing compound impurities during the secondary sintering process to generate aluminum phosphate (and / or lithium aluminum phosphate, lithium iron phosphate aluminum).

[0066] In some embodiments, the molar ratio of the phosphorus source to aluminum in the decommissioned cathode powder is (1 to 1.1):1. As examples, the molar ratio of the phosphorus source to aluminum in the decommissioned cathode powder can be 1:1, 1.02:1, 1.05:1, 1.08:1, 1.1:1, etc. By controlling the molar ratio of phosphorus source and aluminum, the phosphorus source and aluminum can react fully and completely, preventing excess phosphorus or aluminum impurities from affecting the electrochemical performance of the regenerated cathode material.

[0067] The phosphorus source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, or lithium dihydrogen phosphate. By selecting these phosphorus sources, it is possible to make the phosphorus source react chemically with aluminum without introducing impurities.

[0068] In some implementations, the mixing method is ball milling or sand milling. By using ball milling or sand milling, the particle size of the decommissioned cathode powder can be reduced, the sintering performance can be improved, and the decommissioned cathode powder can be fully and uniformly mixed with the lithium source, organic carbon source and phosphorus source.

[0069] Preferably, the mixing method is sand milling, with a milling speed of 1000 rpm to 6000 rpm and a time of 0.5 h to 4 h. Sand milling can make the components mix more evenly, the particle size is appropriate, and the carbon coating layer is uniformly formed on the surface of the recycled cathode material.

[0070] For example, the grinding speed can be 1000rpm, 2000rpm, 3000rpm, 4000rpm, 5000rpm, or 6000rpm, and the grinding time can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, or 4h.

[0071] In some embodiments, the mixing step is followed by spray drying. Spray-dried material particles have good uniformity and flowability, which allows the subsequent organic carbon source and the generated aluminum phosphate to form a uniformly mixed coating layer.

[0072] S130 involves calcining the mixture under a protective atmosphere to obtain a recycled cathode material with a carbon / aluminum phosphate mixed coating.

[0073] In some embodiments, the secondary calcination temperature is 500°C to 750°C, and the time is 8 hours to 16 hours. As examples, the secondary calcination temperature can be 500°C, 650°C, 750°C, etc., and the secondary calcination time can be 8 hours, 10 hours, 16 hours, etc. By controlling the secondary calcination temperature and time within a suitable range, lithium replenishment can be effectively achieved while preventing excessive increase in primary particle size, which would lead to a smaller specific surface area and affect lithium-ion transport efficiency. Furthermore, it allows for the complete reduction of high-valence transition metal ions oxidized during the primary calcination process.

[0074] In some embodiments, the protective atmosphere can be an inert atmosphere or a reducing atmosphere. For example, an inert atmosphere may include at least one of nitrogen, argon, hydrogen, helium, neon, krypton, or xenon. A reducing atmosphere may include a mixture of hydrogen and nitrogen. Secondary sintering under the aforementioned protective atmosphere, combined with an organic carbon source and a phosphorus source, can prevent oxidation reactions and reduce high-valence transition metal ions oxidized during the primary calcination process to lower valences, for example, completely reducing trivalent iron ions formed during the primary calcination process to divalent iron ions, thereby improving the electrochemical performance of the regenerated cathode material.

[0075] In step S130, a second calcination under a protective atmosphere allows lithium and carbon supplementation to be incorporated into the cathode material lattice, reforming the regenerated cathode material. The organic carbon source repairs the carbon coating layer and acts as a reducing agent to inhibit transition metal ion oxidation. The organic carbon source, combined with a phosphorus source, can reduce the trace amounts of high-valence transition metal ions generated in step S110 back to low-valence ions, achieving compositional control. Furthermore, during the second calcination, some elemental aluminum is incorporated into the near-surface or bulk phase of the regenerated cathode material, effectively broadening the lithium-ion transport channels. The added phosphorus source reacts with aluminum-containing impurities such as alumina to generate aluminum phosphate (and / or lithium aluminum phosphate, lithium iron phosphate aluminum) ionic conductors that coat the surface of the regenerated cathode material, effectively improving the lithium-ion transport rate and enhancing the initial discharge capacity and high-temperature cycling performance of the lithium-ion battery.

[0076] The second aspect of this application also provides a recycled cathode material, prepared using the recycling method for retired lithium battery cathode materials provided in the second aspect of this application. This recycled cathode material is a lithium-containing transition metal phosphate with a carbon / aluminum phosphate mixed coating layer on its surface.

[0077] Among them, the chemical composition of lithium-containing transition metal phosphate is LiM x PO4, M includes at least one of Fe, Co, Mn, Ni, Cu, Mg, Al, Zn, Cd, Sc, Ti, V, Cr, Y, La, Ce, Nd, Eu, Gd, and Tb, with 0.5 ≤ x ≤ 1. As an example, lithium-containing transition metal phosphates include at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, or lithium vanadium iron phosphate.

[0078] A third aspect of this application provides a lithium-ion battery, including a positive electrode, a negative electrode, an electrolyte, and a separator. During the charging and discharging process, active lithium ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor between the positive and negative electrodes. The separator is disposed between the positive and negative electrodes, primarily preventing short circuits between the positive and negative electrodes while allowing ions to pass through.

[0079] [Positive electrode plate]

[0080] The positive electrode includes a positive current collector and a positive electrode film layer located on the positive current collector, the positive electrode film layer including a positive electrode active material. In the embodiments of this application, the positive electrode active material is the regenerated positive electrode material with a carbon / aluminum phosphate mixed coating layer provided in the second aspect of this application.

[0081] The positive current collector refers to a structure or component that collects current, and can be a metal foil or a composite current collector. For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0082] In some embodiments, the positive electrode film layer also includes a binder, a conductive agent, and a dispersant.

[0083] A binder is a material in the positive electrode film that acts as an adhesive (bonding the positive electrode film to the positive electrode current collector and bonding the positive electrode active materials together). It is also known as a bonding agent or adhesive. For example, the binder includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin.

[0084] The conductive agent includes at least one of conductive carbon black, conductive graphite, single / multi-walled carbon nanotubes, superconducting carbon, acetylene black, Ketjen black, carbon dots, graphene, and carbon nanofibers. The dispersant includes at least one of polyvinylpyrrolidone (PVP), sodium carboxymethyl cellulose (CMC-Na), lithium carboxymethyl cellulose (CMC-Li), etc.

[0085] In some embodiments, the positive electrode film layer may optionally include other additives, such as plasticizers, which may include at least one of BD-3, AP-4plus, etc.

[0086] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0087] [Negative electrode plate]

[0088] The negative electrode sheet includes a negative current collector layer and a negative electrode film layer attached to the surface of the negative current collector layer. The negative electrode film layer includes a negative electrode active material.

[0089] The negative current collector layer refers to the structure or component that collects current, and can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0090] The negative electrode active material can be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0091] In some embodiments, the negative electrode film layer also includes a binder and a conductive agent.

[0092] The binder includes at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0093] The conductive agent includes at least one of conductive carbon black, conductive graphite, single / multi-walled carbon nanotubes, superconducting carbon, acetylene black, Ketjen black, carbon dots, graphene, and carbon nanofibers. The dispersant includes at least one of polyvinylpyrrolidone (PVP), sodium carboxymethyl cellulose (CMC-Na), lithium carboxymethyl cellulose (CMC-Li), etc.

[0094] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0095] [Electrolytes]

[0096] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0097] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0098] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0099] In some embodiments, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0100] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0101] [Isolation membrane]

[0102] In some embodiments, the lithium-ion battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0103] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0104] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0105] In some embodiments, the lithium-ion battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0106] In some implementations, the outer packaging of a lithium-ion battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of a lithium-ion battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0107] This application does not impose any particular limitation on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 This is an example of a square-structured lithium-ion battery 5.

[0108] In some implementations, refer to Figure 3 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. Positive electrode sheets, negative electrode sheets, and a separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The lithium-ion battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0109] In some implementations, lithium-ion batteries can be assembled into battery modules, and the number of lithium-ion batteries contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0110] Figure 4 This is battery module 4, used as an example. (See reference...) Figure 4 In battery module 4, multiple lithium-ion batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple lithium-ion batteries 5 can be fixed in place using fasteners.

[0111] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple lithium-ion batteries 5 are housed.

[0112] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0113] Figure 5 and Figure 6This is battery pack 1 as an example. (See reference...) Figure 5 and Figure 6 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0114] Furthermore, a fourth aspect of this application also provides an electrical device, which includes the lithium-ion battery provided in the third aspect of this application. The lithium-ion battery can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0115] As an electrical device, lithium-ion batteries, battery modules, or battery packs can be selected according to their usage requirements.

[0116] Figure 7 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of lithium-ion batteries for this device, a battery pack or battery module can be used.

[0117] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use lithium-ion batteries as their power source.

[0118] Example

[0119] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0120] Example 1

[0121] This application provides a method for regenerating retired lithium battery cathode materials, including the following steps:

[0122] (1) The retired positive electrode sheet was calcined once in air (oxygen content of about 21%) at a temperature of 500℃ for 3 hours. The powder was then peeled off from the aluminum foil current collector and vibrated and sieved to obtain the retired positive electrode powder. The positive electrode active material in the retired positive electrode sheet was lithium iron phosphate. According to ICP test, the molar ratio of lithium, iron and phosphorus in the retired positive electrode powder was Li:Fe:P = 0.88:0.994:1, and the content of aluminum impurity was 1000ppm.

[0123] The phase composition of decommissioned cathode powder was analyzed and confirmed using a D8 Advance X-ray diffractometer from Bruker GmbH, Germany, with a copper target as the emission source and a scanning range of 10° to 70°. Figure 8 The XRD pattern of the decommissioned cathode powder provided in Example 1 is shown below. Figure 8 As can be seen from the data, the phase composition detected in the decommissioned cathode powder is Li3Fe2(PO4)3, and some of the divalent iron is oxidized to form Fe2O3.

[0124] (2) A certain amount of lithium carbonate, glucose and ammonium dihydrogen phosphate are added to the retired cathode powder. The lithium carbonate is added so that the molar ratio of lithium to iron is 1.02:1. The amount of glucose added is 10 wt% of the mass of the retired cathode powder. The molar ratio of ammonium dihydrogen phosphate to aluminum is 1.02:1. The mixture is sand-milled and spray-dried to obtain the mixture.

[0125] (3) Under a nitrogen atmosphere, the mixture is calcined twice at a temperature of 650°C for 10 hours to obtain lithium iron phosphate cathode material with a carbon / aluminum phosphate mixed coating.

[0126] The phase composition of the lithium iron phosphate cathode material with a carbon / aluminum phosphate mixed coating was confirmed by XRD analysis. Figure 9 The image shows the XRD pattern of the lithium iron phosphate cathode material with a carbon / aluminum phosphate mixed coating provided in Example 1. Figure 9 It can be confirmed that the recycled cathode material obtained from the recycling process is lithium iron phosphate, and an AlPO4 phase is formed.

[0127] The samples were tested using a ZEISS Sigma 300 scanning electron microscope, and then tested according to standard JY / T010-1996 to observe the morphology and coating uniformity of the samples. Figure 10 Scanning electron microscope (SEM) images and elemental X-ray energy dispersive spectroscopy (EDS) images of the regenerated cathode material with a carbon / aluminum phosphate mixed coating provided in Example 1 of this application. Figure 10 A is a SEM image of the regenerated cathode material with a carbon / aluminum phosphate mixed coating layer provided in Embodiment 1 of this application; Figure 10B is Figure 10 EDS image of P element in the recycled cathode material of A; Figure 10 C is Figure 10 EDS image of Fe element in the regenerated cathode material of A; Figure 10 D is Figure 10 EDS image of O element in the regenerated cathode material of A; Figure 10 E is Figure 10 EDS image of C element in the recycled cathode material of A; Figure 10 F is Figure 10 EDS image of Al in the recycled cathode material of A. From Figure 10 As can be seen, P, O, Al, and C elements are evenly distributed in the regenerated cathode material, indicating that AlPO4 and carbon form a uniformly mixed coating layer on the surface of LiFePO4 particles.

[0128] The regeneration methods of Examples 2-9 and Comparative Example 1 are similar to those of Example 1, but the amounts of decommissioned positive electrode sheets, ammonium dihydrogen phosphate, the temperature and time of the first calcination, the temperature and time of the second calcination, the lithium source, the organic carbon source, and the phosphorus source are adjusted, as detailed in Table 1. In Example 5, the positive electrode active material in the decommissioned positive electrode sheet is lithium iron manganese phosphate, corresponding to a molar ratio of Mn to Fe in the decommissioned positive electrode powder of 6:4; the organic carbon source in Example 9 is pitch; and no phosphorus source is added in step (2) of Comparative Example 1.

[0129] Table 1. Partial parameters of the regeneration methods in Examples 1-9 and Comparative Example 1.

[0130]

[0131]

[0132] Understandably, the preparation methods of Examples 2-9 are similar to those of Example 1, and the phase structure of the prepared regenerated cathode materials is roughly the same as that in Example 1. That is, the prepared regenerated cathode materials are all regenerated cathode materials with a carbon / aluminum phosphate mixed coating layer on the surface. However, in Comparative Example 1, no phosphorus source is added during the secondary sintering process, and the phase structure of the prepared regenerated cathode material does not contain AlPO4. That is, the coating layer only contains organic carbon source and does not contain aluminum phosphate.

[0133] Test case

[0134] The recycled cathode materials obtained in Examples 1-9 and Comparative Example 1 were used to prepare lithium-ion batteries, and the electrochemical performance of the lithium-ion batteries was tested.

[0135] 1. The preparation method of lithium-ion batteries is as follows:

[0136] (1) Preparation of positive electrode sheet

[0137] The regenerated positive electrode materials obtained in Examples 1-9 and Comparative Example 1 were mixed with conductive carbon black (Super P), PVDF, and sodium carboxymethyl cellulose at a weight ratio of 96:1:2.5:0.5, respectively. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added, and the mixture was stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was coated onto aluminum foil and dried to obtain a positive electrode sheet. The positive electrode material loading on the positive electrode sheet was 200 mg / 1540.25 cm⁻¹. 2 .

[0138] (2) Preparation of negative electrode sheet

[0139] Artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber, and sodium carboxymethyl cellulose are mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 95:1:2:2 to form a uniform negative electrode slurry. The negative electrode slurry is then uniformly coated onto the surface of the negative electrode current collector copper foil. After drying and cold pressing, the negative electrode sheet is obtained.

[0140] (3) Separating membrane

[0141] A 12μm thick polypropylene film (Φ16mm) was used as the separator.

[0142] (4) Electrolyte

[0143] Ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was then dissolved in this solution to obtain an electrolyte. The concentration of LiPF6 in this electrolyte was 1 mol / L.

[0144] (5) Preparation of lithium-ion batteries

[0145] The positive electrode, separator, and negative electrode obtained above are arranged in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The mixture is then shaped and packaged in an aluminum-plastic bag. Electrolyte is injected, and after encapsulation, capacity formation is performed to obtain a soft-pack battery.

[0146] 2. The performance testing methods for lithium-ion batteries are as follows:

[0147] (1) Initial discharge capacity

[0148] At 25°C, the pouch cell was charged at a constant current of 0.33C to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After resting for 5 minutes, the pouch cell was discharged at a constant current of 0.33C to a voltage of 2.0V. This discharge capacity is the first-cycle discharge capacity of the lithium-ion battery. Dividing this capacity by the mass of the positive electrode active material in the battery gives the initial discharge specific capacity of the positive electrode active material.

[0149] (2) High-temperature cycling performance

[0150] At 60℃, the pouch cell was charged at a constant current of 0.33C to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After resting for 5 minutes, the pouch cell was discharged at a constant current of 0.33C to a voltage of 2.0V. This constitutes one charging cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. After performing the cycle charging test in the above manner, the cycle ends when the discharge capacity decays to 80% of the initial value. The total number of cycles is the high-temperature cycle life.

[0151] The performance test results are shown in Table 2.

[0152] Table 2 Performance test results of Examples 1-9 and Comparative Example 1

[0153]

[0154]

[0155] As shown in Table 2, the lithium-ion batteries prepared in Examples 1-9 all exhibit high initial discharge capacity and good high-temperature cycling performance, with an initial discharge capacity as high as 142 mAh / g and a cycle count as high as 1200 at 60°C. Comparing the performance test results of Example 1 with Comparative Example 1, Example 1 shows a higher initial discharge capacity and superior cycling performance, indicating that the regenerated cathode material obtained by the regeneration method of retired battery cathode material in this application can effectively improve the initial discharge capacity and high-temperature cycling performance of the regenerated cathode material while removing aluminum impurities.

[0156] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for regenerating retired lithium battery cathode materials, characterized in that, Includes the following steps: The retired cathode sheet is calcined once in an oxygen-containing atmosphere to obtain retired cathode powder; wherein, the cathode active material in the retired cathode sheet includes lithium transition metal phosphate, and the retired cathode powder contains aluminum. The decommissioned cathode powder is mixed with a lithium source, an organic carbon source, and a phosphorus source to obtain a mixture. The mixture is calcined a second time under a protective atmosphere to obtain a regenerated cathode material with a carbon / aluminum phosphate mixed coating.

2. The regeneration method as described in claim 1, characterized in that, The molar ratio of lithium, transition metals and phosphorus in the decommissioned cathode powder is (0.7-0.9):(0.98-0.99):

1.

3. The regeneration method according to any one of claims 1 to 2, characterized in that, The lithium in the lithium source exists in ionic form; And / or, in the mixture, the molar ratio of lithium to transition metal is (1 to 1.08):

1.

4. The regeneration method as described in claim 3, characterized in that, The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, lithium phosphate, lithium acetate, or lithium oxalate.

5. The regeneration method according to any one of claims 1 to 4, characterized in that, The organic carbon source includes at least one of glucose, sucrose, fructose, polyacrylonitrile, asphalt, phenolic resin, starch, citric acid, polyvinyl alcohol, or polypropylene. And / or, the amount of the organic carbon source added is 10wt% to 15wt% of the mass of the decommissioned cathode powder.

6. The regeneration method according to any one of claims 1 to 5, characterized in that, The aluminum content in the decommissioned cathode powder is 500ppm to 2000ppm; And / or, the phosphorus source includes phosphoric acid substances; And / or, the molar ratio of the amount of phosphorus source added to the aluminum element in the decommissioned cathode powder is (1~1.1):

1.

7. The regeneration method as described in claim 6, characterized in that, The phosphorus source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, or lithium dihydrogen phosphate.

8. The regeneration method according to any one of claims 1 to 7, characterized in that, The temperature of the first calcination is 350℃~600℃, and the time is 1h~10h; And / or, the volume percentage of oxygen in the oxygen-containing atmosphere is not less than 10%; And / or, the temperature of the secondary calcination is 500℃~750℃, and the time is 8h~16h; And / or, the protective atmosphere is an inert atmosphere or a reducing atmosphere.

9. The regeneration method according to any one of claims 1 to 8, characterized in that, The mixing method is ball milling or sand milling; And / or, the mixing method is sand milling, wherein the sand milling speed is 1000rpm~6000rpm and the time is 0.5h~4h; And / or, the mixing step may be followed by spray drying.

10. The regeneration method according to any one of claims 1 to 9, characterized in that, The chemical composition of the lithium-containing transition metal phosphate is LiM x PO4, wherein M includes at least one of Fe, Co, Mn, Ni, Cu, Mg, Al, Zn, Cd, Sc, Ti, V, Cr, Y, La, Ce, Nd, Eu, Gd or Tb, and 0.5 ≤ x ≤ 1.

11. The regeneration method as described in claim 10, characterized in that, The lithium-containing transition metal phosphate includes at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, or lithium vanadium iron phosphate.

12. A recycled cathode material, characterized in that, It is prepared by the regeneration method according to any one of claims 1 to 11.

13. A lithium-ion battery, characterized in that, Including the recycled cathode material as described in claim 12.

14. An electrical appliance, characterized in that, Including the lithium-ion battery as described in claim 13.

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