A method for regenerating waste lithium iron phosphate cathode material, and a lithium ion battery

Abstract

This invention relates to a method for regenerating waste lithium iron phosphate cathode materials and lithium-ion batteries, belonging to the field of electronic waste resource utilization technology. The method for regenerating waste lithium iron phosphate cathode materials includes the following steps: adding waste lithium iron phosphate cathode materials to a medium-strong acid solution for acid leaching and dissolution, followed by filtration to obtain a transparent solution; reflux heating the transparent solution, followed by filtration to obtain an iron-phosphorus product and a lithium-containing solution; treating the lithium-containing solution to obtain a lithium salt product; mixing the iron-phosphorus product, the lithium salt product, and a carbon source, followed by calcination under an inert atmosphere to obtain a LiFePO4 / C composite material. This invention solves the problems of complex processing, high energy consumption, serious secondary pollution, high impurity content in products, and low quality of recycled products in existing waste lithium iron phosphate battery treatment technologies. Furthermore, the recycled cathode electrode material obtained by this invention can meet battery-grade standards again.

Description

Technical Field

[0001] This invention relates to the field of electronic waste resource utilization technology, and in particular to a method for regenerating lithium iron phosphate cathode material waste and lithium-ion batteries. Background Technology

[0002] With the widespread promotion of new energy vehicles and strong government policy support, the new energy vehicle market has achieved significant breakthroughs. As a crucial power source for new energy vehicles, lithium-ion batteries have also seen rapid growth in production. Lithium iron phosphate (LFP) batteries account for over 60% of this market, and this growth continues unabated with the development of new energy vehicles and energy storage. However, due to the limited cycle life of lithium-ion batteries (ranging from 5 to 8 years), many early-produced LFP batteries have reached their end-of-life after nearly a decade of development, and their scrap volume is increasing daily with the expanding market. LFP batteries are rich in metals such as Li and Fe. Effective recycling can reduce market dependence on scarce resources like Li, and the recovered metal resources offer considerable economic benefits. Furthermore, the large amount of carbon dioxide generated during battery production is mainly concentrated in the material manufacturing stage; recycling battery waste can effectively reduce carbon emissions. At the same time, waste lithium-ion batteries also contain organic binders, organic electrolytes, and harmful lithium salts. Therefore, recycling waste lithium-ion batteries can not only effectively alleviate metal resource shortages and environmental problems but also offer significant economic benefits.

[0003] Traditional pyrometallurgical and hydrometallurgical processes for recycling lithium iron phosphate (LFP) cathode material waste employ a crushing method. After thoroughly pulverizing the batteries, they undergo a series of treatments, including smelting (generally at temperatures ≥900℃) or strong acid processing, to obtain molten alloys and metal mixtures. These are then subjected to a series of complex separation processes to obtain lithium and iron raw materials, primarily lithium and iron salts. Finally, new batteries are manufactured from scratch. This recycling approach easily leads to a waste of energy and resources. Furthermore, some current processes propose adding lithium sources (Li₂CO₃ and LiOH) to LFP waste for direct regeneration under high-temperature conditions. However, the regenerated materials obtained by this method contain impurities and certain lattice defects, making them unsuitable for direct use as cathode materials. Therefore, it is necessary to develop novel recycling methods that treat LFP waste under relatively mild conditions, yielding recycled products with good quality that can be directly used as precursors for LFP production, thereby achieving the recycling of LFP cathode materials. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for regenerating waste lithium iron phosphate cathode materials and a lithium-ion battery. This invention aims to solve the problems of complex processing procedures, high energy consumption, severe secondary pollution, numerous impurities in the products, and low quality of the recycled products in existing waste lithium iron phosphate battery treatment technologies. Simultaneously, this invention can effectively achieve the conversion and recycling of waste lithium iron phosphate battery cathode materials, and the resulting recycled cathode electrode material can once again meet battery-grade standards.

[0005] In a first aspect, the present invention provides a method for regenerating lithium iron phosphate cathode material waste, the method comprising the following steps:

[0006] The waste lithium iron phosphate cathode material was added to a medium-strong acid solution for acid leaching and dissolution, and then filtered to obtain a transparent solution.

[0007] The transparent solution was refluxed and heated, then filtered to obtain an iron-phosphorus product and a lithium-containing solution.

[0008] The lithium-containing solution was treated to obtain a lithium salt product;

[0009] The iron-phosphorus product, the lithium salt product, and the carbon source were mixed and then calcined under an inert atmosphere to obtain a LiFePO4 / C composite material.

[0010] Furthermore, the moderately strong acid includes phosphoric acid, and the concentration of the phosphoric acid is 0.3–1.1 mol / L.

[0011] Furthermore, the operating parameters of the reflux heating include: a temperature of 60–90°C and a duration of 6–12 hours.

[0012] Further, the step of processing the lithium-containing solution to obtain the lithium salt product includes the following processes:

[0013] The lithium salt product is obtained by adding an alkali to the lithium-containing solution to adjust the pH to 12-14, then passing CO2 gas or adding a carbonate compound, filtering and drying.

[0014] Further, the step of processing the lithium-containing solution to obtain the lithium salt product includes the following processes:

[0015] The lithium-containing solution was vacuum dried to obtain an oily viscous substance.

[0016] The oily viscous substance was mixed and dissolved with ethanol, then filtered, washed and dried to obtain the lithium salt product.

[0017] Furthermore, the molar ratio of the iron-phosphorus product, the lithium salt product (Li2CO3), and the carbon source is 2:(1.05-1.15):(0.3-0.5).

[0018] Furthermore, the carbon source includes at least one of glucose, sucrose, phenolic resin, and carbon black.

[0019] Furthermore, the roasting parameters include: a temperature of 650–900°C and a duration of 8–12 hours.

[0020] Secondly, the present invention provides a LiFePO4 / C composite material, which is prepared by the regeneration method of lithium iron phosphate cathode material waste as described in any one of the first aspects.

[0021] Thirdly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising at least a portion of a battery positive electrode made of the LiFePO4 / C composite material described in any of the second aspects.

[0022] The technical solutions provided in the embodiments of the present invention have at least the following advantages compared with the prior art:

[0023] This invention provides a method for regenerating waste lithium iron phosphate (LFP) cathode materials. By thoroughly decomposing and dissolving the waste LFP cathode materials under the action of moderately strong phosphoric acid, the dissolution efficiency of LFP is improved, significantly increasing the effective recovery rate of lithium. After reflux heating, further reaction precipitation produces a nanoscale layered structure FePO4·2H2O (iron-phosphorus product), which can be directly used as the iron and phosphorus source for LFP preparation. Furthermore, the solution is mainly a lithium solution, and lithium salt products can be recovered in the form of LiH2PO4 and Li2CO3, respectively, which can be used as the main lithium source for cathode material preparation. Therefore, the process proposed in this invention achieves effective recovery of all elements from LFP waste. After adding a carbon source in a certain proportion, the obtained product is calcined at high temperature in an oxygen-free environment to obtain a LiFePO4 / C composite material, which has been verified to be directly used as a LFP cathode material. This effectively solves the problems of complex processing, high energy consumption, serious secondary pollution, high impurity content in the product, and low quality of the recycled product in existing waste LFP battery treatment technologies. Meanwhile, this invention can effectively realize the conversion and recycling of waste lithium iron phosphate battery cathode materials, and the resulting recycled cathode electrode material can meet battery-grade standards again. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic flowchart of a method for regenerating waste lithium iron phosphate cathode material provided in an embodiment of the present invention.

[0027] Figure 2 This is a schematic flowchart of a method for regenerating waste lithium iron phosphate cathode material provided in Embodiment 1 of the present invention.

[0028] Figure 3 This is a SEM image of regenerated LiFePO4 / C obtained in Example 1 of the present invention.

[0029] Figure 4 The XRD patterns of regenerated LiFePO4 / C obtained in the embodiments and comparative examples of the present invention are shown. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] In a first aspect, the present invention provides a method for regenerating waste lithium iron phosphate cathode materials, such as... Figure 1 As shown, the method for regenerating the waste lithium iron phosphate cathode material includes the following steps:

[0033] The waste lithium iron phosphate cathode material was added to a medium-strong acid solution for acid leaching and dissolution, and then filtered to obtain a transparent solution.

[0034] The transparent solution was refluxed and heated, then filtered to obtain an iron-phosphorus product and a lithium-containing solution.

[0035] The lithium-containing solution was treated to obtain a lithium salt product;

[0036] The iron-phosphorus product, the lithium salt product, and the carbon source were mixed and then calcined under an inert atmosphere to obtain a LiFePO4 / C composite material.

[0037] This invention provides a method for regenerating waste lithium iron phosphate (LFP) cathode materials. By thoroughly decomposing and dissolving the waste LFP cathode materials under the action of moderately strong phosphoric acid, the dissolution efficiency of LFP is improved, significantly increasing the effective recovery rate of lithium. After reflux heating, further reaction precipitation produces a nanoscale layered structure FePO4·2H2O (iron-phosphorus product), which can be directly used as the iron and phosphorus source for LFP preparation. Furthermore, the solution is mainly a lithium solution, and lithium salt products can be recovered in the form of LiH2PO4 and Li2CO3, respectively, which can be used as the main lithium source for cathode material preparation. Therefore, the process proposed in this invention achieves effective recovery of all elements from LFP waste. After adding a carbon source in a certain proportion, the obtained product is calcined at high temperature in an oxygen-free environment to obtain a LiFePO4 / C composite material, which has been verified to be directly used as a LFP cathode material. This effectively solves the problems of complex processing, high energy consumption, serious secondary pollution, high impurity content in the product, and low quality of the recycled product in existing waste LFP battery treatment technologies. Meanwhile, this invention can effectively realize the conversion and recycling of waste lithium iron phosphate battery cathode materials, and the resulting recycled cathode electrode material can meet battery-grade standards again.

[0038] The process for processing waste lithium iron phosphate battery cathode materials according to this invention is simple and efficient, effectively recovering valuable metal elements from the waste, and has the advantages of low energy consumption and high recovery rate. This invention is of great significance for achieving efficient recycling and reuse of waste lithium iron phosphate battery cathode materials, and can be widely used in the fields of waste lithium iron phosphate battery recycling and comprehensive waste management.

[0039] In some specific embodiments, the waste lithium iron phosphate cathode material can be obtained by the following method: Firstly, waste lithium iron phosphate batteries are disassembled after discharge to obtain waste lithium iron phosphate cathode sheets. The cathode active material and aluminum foil are separated by preheating. After removing the aluminum foil, the cathode active material is pulverized to obtain the waste lithium iron phosphate cathode material. The source of the waste lithium iron phosphate can be from energy storage, power batteries, or 3C applications. The type of waste lithium iron phosphate battery can be prismatic, pouch, or cylindrical. The preheating method can be an inert atmosphere or an oxygen-containing atmosphere, with a temperature generally between 400 and 600°C.

[0040] In some specific embodiments, the moderately strong acid includes phosphoric acid, and the concentration of the phosphoric acid is 0.3–1.1 mol / L. This invention uses phosphoric acid of a specific concentration for acid leaching and dissolving lithium iron phosphate cathode material waste, thereby improving the dissolution efficiency of lithium iron phosphate and significantly increasing the effective recovery rate of lithium.

[0041] In some specific embodiments, the operating parameters for the reflux heating include: a temperature of 60–90°C and a duration of 6–12 hours. This invention, through reflux heating of a transparent solution under the aforementioned specific parameters, first separates an iron-phosphorus product with a layered structure (nanoscale layered FePO4·2H2O), and then processes the solution to obtain two different lithium salt products.

[0042] In some specific embodiments, the step of treating the lithium-containing solution to obtain the lithium salt product includes the following process: adding an alkali to the lithium-containing solution to adjust the pH to 12-14, then bubbling in CO2 gas or adding a carbonate compound, filtering and drying to obtain the lithium salt product. The present invention can treat the lithium-containing solution to obtain a solid Li2CO3 lithium salt product, specifically including the following process: adding an alkali solution to the lithium-containing solution to adjust the pH to 12-14, then bubbling in CO2 gas or a carbonate compound to the solution to obtain a white Li2CO3 precipitate, filtering and drying to obtain the solid Li2CO3 product.

[0043] In some specific embodiments, the step of processing the lithium-containing solution to obtain the lithium salt product includes the following processes: vacuum drying the lithium-containing solution to obtain an oily viscous substance; mixing and dissolving the oily viscous substance with ethanol, followed by filtration, washing, and drying to obtain the lithium salt product. The present invention can process the lithium-containing solution to obtain a solid LiH2PO4 lithium salt product, specifically including the following processes: placing the lithium-containing solution in a vacuum drying oven at a temperature generally of 80–120°C to obtain an oily viscous substance, then adding anhydrous ethanol to separate the white precipitate of LiH2PO4, filtering, washing with anhydrous ethanol, and drying to obtain the solid LiH2PO4 product.

[0044] In some specific embodiments, the molar ratio of the iron-phosphorus product, the lithium salt product (Li2CO3), and the carbon source is 2:(1.05-1.15):(0.3-0.5). Preferably, the molar ratio of the iron-phosphorus product, the lithium salt product, and the carbon source is 2:1.05:0.3.

[0045] In some specific embodiments, the carbon source includes at least one of glucose, sucrose, phenolic resin, and carbon black.

[0046] In some specific embodiments, the roasting parameters include: a temperature of 650–900°C and a duration of 8–12 hours.

[0047] Secondly, based on a general inventive concept, the present invention provides a LiFePO4 / C composite material, which is prepared by the recycling method of lithium iron phosphate cathode material waste as described in any one of the first aspects.

[0048] This invention can effectively realize the conversion and recycling of cathode materials from waste lithium iron phosphate batteries. The resulting recycled cathode material can meet battery-grade standards again. This is of great significance for the efficient recycling and reuse of cathode materials from waste lithium iron phosphate batteries and can be widely used in the fields of waste lithium iron phosphate battery recycling and comprehensive waste management.

[0049] Thirdly, based on the same inventive concept, the present invention provides a lithium-ion battery, the lithium-ion battery comprising at least a portion of a battery positive electrode made of the LiFePO4 / C composite material described in any of the second aspects.

[0050] The lithium-ion battery provided by this invention, because it uses at least a portion of the LiFePO4 / C composite material obtained from the recycling method of lithium iron phosphate cathode material waste as described in any one of the first aspects to prepare the battery cathode, has at least the beneficial effects described in the first aspect, which will not be elaborated further here. Meanwhile, this lithium-ion battery can be prepared using existing conventional lithium-ion battery manufacturing processes, which will also not be elaborated further here.

[0051] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0052] Example 1

[0053] This example provides a method for regenerating waste lithium iron phosphate cathode materials, such as... Figure 2 As shown, it includes the following steps:

[0054] (1) Discharge the waste lithium iron phosphate battery to a safe charge, then disassemble and separate the waste lithium iron phosphate positive electrode sheet, and pyrolyze it in a pyrolysis furnace under an inert atmosphere at 500℃. Disassemble the waste lithium-ion battery, separate the waste positive electrode foil, heat it at 500℃ to separate the active material and aluminum foil, and crush and sort the active material to obtain lithium iron phosphate waste with a particle size ≤50μm;

[0055] (2) The lithium iron phosphate waste obtained in step (1) was leached and dissolved in a phosphoric acid solution with a phosphoric acid concentration of 0.9 mol / L. After complete dissolution, the supernatant was obtained by filtration and then heated and refluxed at 80°C for 9 h to obtain a FePO4·2H2O precursor with a layered structure. Then, an alkaline solution was added to the supernatant to adjust the pH to 12-14, and CO2 gas was bubbled into the solution to obtain a white precipitate of Li2CO3. After filtration and drying, Li2CO3 solid product was obtained. The recovery rate of Li is shown in Table 1.

[0056] (3) Li₂CO₃ and FePO₄·2H₂O were mixed at a molar ratio of 1.05:2, and then about 20% glucose was added as a carbon source. The mixture was calcined in an inert environment, and the temperature was increased to 650℃ in stages and held for 9 hours to obtain the regenerated LiFePO₄ / C composite material. The SEM and XRD images of the final product are shown below. Figure 3 and Figure 4 As shown in Table 2, the discharge is as follows.

[0057] Example 2

[0058] This example provides a method for regenerating waste lithium iron phosphate cathode materials, which is adjusted from Example 1 as follows (all other steps and parameters are the same):

[0059] (2) The lithium iron phosphate waste obtained in step (1) was leached and dissolved in a phosphoric acid solution with a concentration of 0.9 mol / L. After complete dissolution, the supernatant was obtained by filtration and then heated under reflux at 80°C for 9 hours to obtain a FePO4·2H2O precursor with a layered structure. Subsequently, the Li-containing waste was treated with... + The supernatant was processed and placed in a vacuum drying oven at 90°C to obtain an oily viscous substance. Then anhydrous ethanol was added to separate the white precipitate of LiH2PO4. After filtration, it was washed with anhydrous ethanol and dried to obtain the solid product of LiH2PO4. The recovery rate of Li is shown in Table 1.

[0060] (3) LiH2PO4 and FePO4·2H2O were mixed at a molar ratio of 1.05:1, and then about 20% glucose was added as a carbon source. The mixture was calcined in an inert environment, with the temperature gradually increased to 650℃ and held for 9 hours to obtain the regenerated LiFePO4 / C composite material. The XRD pattern of the final product is shown in the figure. Figure 4 As shown in Table 2, the discharge is as follows.

[0061] Example 3

[0062] This example provides a method for regenerating waste lithium iron phosphate cathode materials, which is adjusted from Example 1 as follows (all other steps and parameters are the same):

[0063] (2) The lithium iron phosphate waste obtained in step (1) was leached and dissolved in a phosphoric acid solution with a concentration of 0.3 mol / L. After complete dissolution, the supernatant was obtained by filtration and then heated and refluxed at 90°C for 12 h to obtain a FePO4·2H2O precursor with a layered structure. Then, an alkaline solution was added to the supernatant to adjust the pH to 12-14, and CO2 gas was bubbled into the solution to obtain a white precipitate of Li2CO3. After filtration and drying, the solid product of Li2CO3 was obtained. The recovery rate of Li is shown in Table 1.

[0064] (3) Mix Li2CO3 and FePO4·2H2O in a molar ratio of 1.05:2, then add about 20% phenolic resin as a carbon source and calcine in an inert environment. The temperature is raised to 650℃ in stages and held for 9 hours to obtain the regenerated LiFePO4 / C composite material. The charge and discharge are shown in Table 2.

[0065] Example 4

[0066] This example provides a method for regenerating waste lithium iron phosphate cathode materials, which is adjusted from Example 1 as follows (all other steps and parameters are the same):

[0067] (2) The lithium iron phosphate waste obtained in step (1) was leached and dissolved in a phosphoric acid solution with a phosphoric acid concentration of 1.1 mol / L. After complete dissolution, the supernatant was obtained by filtration and then heated and refluxed at 70°C for 9 h to obtain a FePO4·2H2O precursor with a layered structure. Then, an alkaline solution was added to the supernatant to adjust the pH to 12-14, and CO2 gas was bubbled into the solution to obtain a white precipitate of Li2CO3. After filtration and drying, the solid product of Li2CO3 was obtained. The recovery rate of Li is shown in Table 1.

[0068] (3) Mix Li2CO3 and FePO4·2H2O in a molar ratio of 1.05:2, then add about 20% sucrose as a carbon source and calcine in an inert environment. The temperature is raised to 650℃ in stages and held for 9 hours to obtain the regenerated LiFePO4 / C composite material. The charge and discharge are shown in Table 2.

[0069] Example 5

[0070] This example provides a method for regenerating waste lithium iron phosphate cathode materials, which is adjusted from Example 1 as follows (all other steps and parameters are the same):

[0071] (3) Mix Li2CO3 and FePO4·2H2O in a molar ratio of 1.05:2, then add about 20% glucose as a carbon source and calcine in an inert environment. The temperature is raised to 900℃ in stages and held for 8 hours to obtain the regenerated LiFePO4 / C composite material. The charge and discharge are shown in Table 2.

[0072] Comparative Example 1

[0073] Commercially available LiFePO4 / C composite materials were selected as a control sample, and their lattice and charge-discharge data were compared with those of the prepared recycled LiFePO4 / C composite materials. Their XRD patterns are shown below. Figure 4 As shown in Table 2, the discharge is as follows.

[0074] Table 1. Li recovery rates in different embodiments

[0075] Group Li recovery rate (%) Example 1 97.7 Example 2 96.3 Example 3 97.1 Example 4 96.7 Example 5 97.5

[0076] As shown in Table 1, the regeneration method for recovering lithium iron phosphate cathode waste using medium-strong acid achieves a recovery rate of over 96% for valuable metal elements, especially Li, maintaining a high level. This indicates that the method effectively recovers Li and avoids resource waste. Furthermore, it is noteworthy that the Li recovery rate increases with increasing phosphoric acid concentration, but declines slightly when the concentration rises from 0.9 mol / L to 1.1 mol / L, suggesting that a phosphoric acid concentration of 0.9 mol / L is more suitable. Compared to the traditional dry method, this method avoids the loss of Li due to high-temperature volatilization; and compared to the traditional wet method, the reaction conditions are milder, avoiding the use of large amounts of strong acids and bases.

[0077] Table 2 Regenerated LiFePO4 of the present invention 4 / Comparison of discharge specific capacity between C composite material and commercial LiFePO4 / C composite material under 1C / 1C charge-discharge conditions (room temperature 25±2℃)

[0078]

[0079] As shown in Table 2, the regeneration methods for recovering lithium iron phosphate cathode waste using medium-strong acid (Examples 1-5) all exhibit superior initial discharge specific capacity under 1C charge-discharge conditions, demonstrating competitiveness compared to the first-cycle discharge specific capacity of commercial cathode materials (Comparative Example 1). After 50 cycles of constant current charge-discharge, the capacity retention rate of the regenerated cathode materials obtained in this invention (Examples 1-5) remained above 98%, almost on par with the capacity retention rate of commercial cathode materials (Comparative Example 1), exhibiting excellent electrochemical performance.

[0080] Figure 3The LiFePO4 / C composite material obtained in Example 1 has a relatively uniform and fine morphology. The generated crystals are coated with a layer of uniform and fine carbon particles, indicating that the LiFePO4 / C composite material obtained in this example has a good morphological structure.

[0081] Figure 4 The XRD patterns of the samples in Examples 1, 2 and Comparative Example 1 are shown. The results show that the crystal lattice of Examples 1 and 2 is relatively close to that of commercial LiFePO4 / C composite materials, indicating that the composite materials obtained by this method have a better crystal structure.

[0082] In summary, the regeneration method for recovering lithium iron phosphate cathode waste using moderately strong acid provided by this invention can effectively separate and leach waste lithium iron phosphate cathode materials, effectively recover and separate Li and Fe products, maximize the retention of valuable metal elements in the products, and the recovered products can be used as precursors and raw materials for preparing LiFePO4 / C composite materials, simplifying the recycling process. The final LiFePO4 / C composite material obtained has good discharge specific capacity. These results demonstrate that the regeneration method for recovering lithium iron phosphate cathode waste using moderately strong acid of this invention has promising application prospects for the recycling and regeneration of waste lithium iron phosphate cathode materials.

[0083] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0084] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for regenerating waste lithium iron phosphate cathode material, characterized in that, The method for regenerating the lithium iron phosphate cathode material waste includes the following steps: The waste lithium iron phosphate cathode material was dissolved by acid leaching in a phosphoric acid solution, followed by filtration to obtain a transparent solution; the concentration of the phosphoric acid was 0.3~1.1 mol / L. The transparent solution was refluxed and heated, then filtered to obtain an iron-phosphorus product and a lithium-containing solution. The reflux heating parameters included a temperature of 60-90°C and a duration of 6-12 hours. The lithium-containing solution is adjusted to pH 12-14 by adding alkali, then CO2 gas is introduced or carbonate compounds are added, filtered and dried to obtain the lithium salt product. Alternatively, the lithium-containing solution is vacuum dried to obtain an oily viscous substance; the oily viscous substance is mixed and dissolved with ethanol, then filtered, washed and dried to obtain a lithium salt product; The iron-phosphorus product, the lithium salt product, and the carbon source were mixed and then calcined under an inert atmosphere to obtain a LiFePO4 / C composite material. The molar ratio of the iron-phosphorus product, the lithium salt product, and the carbon source is 2:(1.05~1.15):(0.3~0.5).

2. The method for regenerating lithium iron phosphate cathode material waste according to claim 1, characterized in that, The carbon source includes at least one of glucose, sucrose, phenolic resin, and carbon black.

3. The method for regenerating lithium iron phosphate cathode material waste according to claim 1, characterized in that, The roasting parameters include: temperature of 650~900℃ and duration of 8~12 hours.

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