Repair method and application of positive electrode material of waste lithium iron phosphate battery, and lithium ion battery

Abstract

The invention provides a repairing method and application of a waste lithium iron phosphate battery positive electrode material and a lithium ion battery. According to the method for repairing the positive electrode material of the waste lithium iron phosphate battery, an organic alcohol solution is used as a cosolvent, invalid lithium iron phosphate, a lithium source and a reducing agent are used as raw materials, the raw materials are firstly prepared into a solution, and then the processes of hydrothermal reaction, filtration, collection, drying and the like are carried out to obtain the positive electrode material of the waste lithium iron phosphate battery. Therefore, the waste lithium iron phosphate is repaired and regenerated into lithium iron phosphate to serve as an electrode material. According to the method, the LFP is directly repaired and regenerated through the simple one-step hydrothermal reaction, the waste lithium iron phosphate positive electrode material can be directly regenerated into lithium iron phosphate capable of being continuously used through the simple one-step hydrothermal method, and the purpose of recycling is achieved. The process supplements the lithium source which is relatively high in consumption in the battery using process, restores the crystal structure of the lithium iron phosphate, and is simple in process, green, pollution-free and high in recovery efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a method and application of repairing a waste lithium iron phosphate battery positive electrode material, and a lithium-ion battery. Background Art

[0002] With the onset of a wave of power battery retirements, establishing a robust recycling system for power batteries and safely handling spent lithium-ion batteries, which are flammable, explosive, and contain toxic components such as fluoride, is crucial for reducing carbon emissions throughout their lifecycle, safeguarding the lives of humans and animals, and protecting land and the environment from pollution. Olivine-structured LiFePO₄ (LFP) is considered a promising cathode material for lithium-ion batteries due to its high stability, long lifespan, and safety. It is commonly used in large-scale energy storage devices, electric vehicles (EVs), and hybrid electric vehicles (HEVs). However, as LFP batteries reach the end of their lifespan, a large number of them are retired. Because they contain multiple valuable metals, such as lithium, phosphorus, and copper, they represent a secondary resource with high recycling value. Furthermore, spent LFP batteries contain toxic organic matter and heavy metals, which, if not properly handled, can harm human health and the environment. Therefore, recycling spent LFP batteries can significantly reduce the demand for related raw materials, mitigate environmental threats, and thus promote their sustainability.

[0003] Currently, the most common methods for recycling LFP are hydrometallurgy, pyrometallurgy, high-temperature calcination, etc. Most of these methods are complex and cause serious secondary pollution, which is contrary to the concept of green development.

[0004] Based on the defects of the current recycling of LFP, it is necessary to improve it. Summary of the Invention

[0005] To address the deficiencies in the prior art, the present invention provides a method and application for repairing spent lithium iron phosphate battery cathode materials, as well as a lithium-ion battery. This method directly regenerates LFP through a simple one-step hydrothermal reaction. This simple one-step hydrothermal method can regenerate spent lithium iron phosphate cathode materials into reusable lithium iron phosphate, achieving recycling. This process replenishes the lithium source, which is consumed significantly during battery use, and restores the crystal structure of the lithium iron phosphate, resulting in a simple, environmentally friendly, and pollution-free process.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for repairing waste lithium iron phosphate battery positive electrode materials, comprising the following steps:

[0008] Adding waste lithium iron phosphate and lithium source into an organic alcohol solution, then adding a reducing agent and stirring to obtain a mixed solution;

[0009] The mixed solution is subjected to a hydrothermal reaction, filtered, and dried to complete the repair of the waste lithium iron phosphate battery positive electrode material to obtain a repaired lithium-ion battery positive electrode material;

[0010] Wherein, the organic alcohol includes at least one of diethylene glycol and triethylene glycol.

[0011] Preferably, the organic alcohol solution comprises organic alcohol and water;

[0012] The volume ratio of the organic alcohol to water is (3-40):(5-35).

[0013] Preferably, the lithium source includes at least one of lithium hydroxide, lithium acetate, and lithium sulfate;

[0014] The reducing agent includes at least one of sodium sulfite, L-threonine, tartaric acid, and citric acid.

[0015] Preferably, the mass volume ratio of the waste lithium iron phosphate, reducing agent and organic alcohol solution is (1-5) g: (0.1-8) g (15-200) mL;

[0016] Waste lithium iron phosphate and a lithium source are added to an organic alcohol solution so that the final concentration of the lithium source is 5 to 20 g / L.

[0017] Preferably, in the step of subjecting the mixed solution to a hydrothermal reaction, the hydrothermal reaction temperature is 160-220° C. and the reaction time is 3-8 h.

[0018] Preferably, the mixed solution is subjected to a hydrothermal reaction, filtered after the reaction is completed, and dried at 50-100° C. to obtain a repaired lithium-ion battery positive electrode material.

[0019] In a second aspect, the present invention further provides a lithium-ion battery positive electrode material, which is repaired using the above-mentioned repair method.

[0020] In a third aspect, the present invention further provides a lithium ion battery positive electrode, comprising a positive electrode current collector and a positive electrode slurry coated on the positive electrode current collector;

[0021] The positive electrode slurry includes a binder, a conductive agent, a solvent and the lithium ion battery positive electrode material obtained by the repair method or the lithium ion battery positive electrode material.

[0022] In a fourth aspect, the present invention further provides a use of the lithium-ion battery positive electrode material or the lithium-ion battery positive electrode in the preparation of a lithium battery.

[0023] In a fifth aspect, the present invention further provides a lithium-ion battery, comprising a positive electrode, wherein the positive electrode is the positive electrode of the lithium-ion battery.

[0024] The repair method and application of waste lithium iron phosphate battery positive electrode materials and lithium ion batteries of the present invention have the following effects compared with the prior art:

[0025] 1. The present invention relates to a method for repairing waste lithium iron phosphate battery positive electrode materials. After a large number of experimental studies, the inventors have developed a method for regenerating and repairing waste lithium iron phosphate battery positive electrode materials based on co-solvents. The method uses an organic alcohol (diethylene glycol, triethylene glycol) solution as a co-solvent, and uses failed lithium iron phosphate, a lithium source (including lithium hydroxide, lithium acetate, lithium sulfate, etc.), and a reducing agent (including sodium sulfite, L-threonine, tartaric acid, citric acid, etc.) as raw materials. First, the raw materials are configured into a solution, and then a hydrothermal reaction, filtration and collection, and drying processes are performed, so that the waste lithium iron phosphate is repaired and regenerated into lithium iron phosphate as an electrode material. The present invention directly repairs and regenerates LFP through a simple one-step hydrothermal reaction. Through a simple one-step hydrothermal method, the waste lithium iron phosphate positive electrode material can be directly regenerated into lithium iron phosphate that can be continued to be used, thereby achieving the purpose of recycling. This process supplements the lithium source that is consumed more during the use of the battery, and repairs the crystal structure of the lithium iron phosphate. The process is simple, green and pollution-free, and has high recovery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0027] Figures 1-2 The following are scanning electron microscope (SEM) images of waste lithium iron phosphate (S-LFP) in Example 2 of the present invention at different magnifications;

[0028] Figures 3-4 The following are scanning electron microscope (SEM) images of the lithium-ion battery cathode material after repairing the waste lithium iron phosphate material in Example 2 of the present invention at different magnifications;

[0029] Figure 5 The XRD patterns of the repaired lithium-ion battery cathode material and the initial waste lithium iron phosphate (S-LFP) obtained by the repair method in Examples 1 to 3;

[0030] Figure 6 This is a CV image of a lithium-ion battery assembled from the lithium-ion battery cathode material repaired from the waste lithium iron phosphate material in Example 2 at a small scan rate of 0.1 mv / s;

[0031] Figure 7CV images of lithium-ion batteries assembled from lithium-ion battery cathode materials repaired from waste lithium iron phosphate materials in Example 2 at different scan rates;

[0032] Figure 8 Lithium-ion batteries assembled from waste lithium iron phosphate ( Figure 8 S-LFP) and the lithium ion battery positive electrode material assembled from the waste lithium iron phosphate material repaired in Example 2 of the present invention ( Figure 8 R-LFP) rate performance comparison chart;

[0033] Figure 9 Lithium-ion batteries assembled from waste lithium iron phosphate ( Figure 9 S-LFP) and the lithium ion battery positive electrode material assembled from the waste lithium iron phosphate material repaired in Example 2 of the present invention ( Figure 9 Comparison of cycling performance of R-LFP at 0.2C current density;

[0034] Figure 10 This is a comparison chart of the cycling performance at a current density of 0.5C between a lithium-ion battery assembled from a lithium-ion battery cathode material repaired with waste lithium iron phosphate material using ethanol (EG) as a co-solvent in Comparative Example 1 and a lithium-ion battery assembled from a lithium-ion battery cathode material repaired with triethylene glycol (TEG) in Example 2 of the present invention;

[0035] Figure 11 Lithium-ion batteries assembled from waste lithium iron phosphate ( Figure 11 S-LFP) and the lithium ion battery positive electrode material assembled from the waste lithium iron phosphate material repaired in Example 2 of the present invention ( Figure 11 Impedance comparison diagram of R-LFP). DETAILED DESCRIPTION

[0036] To facilitate understanding of the present invention, the present invention will be described more fully below in conjunction with the specific embodiments. Preferred embodiments of the present invention are provided in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0037] The order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of this application, the term "including" means "including but not limited to". Various embodiments of the present invention may be presented 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 understood as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0038] The present invention provides a method for repairing waste lithium iron phosphate battery positive electrode materials, comprising the following steps:

[0039] S1. Add waste lithium iron phosphate and a lithium source to an organic alcohol solution, then add a reducing agent and stir to obtain a mixed solution;

[0040] S2. The mixed solution is subjected to a hydrothermal reaction, filtered, and dried to complete the repair of the waste lithium iron phosphate battery positive electrode material to obtain a repaired lithium-ion battery positive electrode material;

[0041] Among them, organic alcohols include diethylene glycol (chemical formula C4H 10 O3,), triethylene glycol (i.e. triethylene glycol, molecular formula C6H 14 O4) at least one.

[0042] After a large number of experimental studies, the inventors have developed a co-solvent-based regeneration and repair method for waste lithium iron phosphate battery positive electrode materials. The method uses an organic alcohol (diethylene glycol, triethylene glycol) solution as a co-solvent, and uses failed lithium iron phosphate, a lithium source (including lithium hydroxide, lithium acetate, lithium sulfate, etc.), and a reducing agent (including sodium sulfite, L-threonine, tartaric acid, citric acid, etc.) as raw materials. First, the raw materials are configured into a solution, and then a hydrothermal reaction, filtration and collection, and drying process are performed, so that the waste lithium iron phosphate is repaired and regenerated into lithium iron phosphate as an electrode material. The present invention directly repairs and regenerates LFP through a simple one-step hydrothermal reaction. Through a simple one-step hydrothermal method, the waste lithium iron phosphate positive electrode material can be directly regenerated into lithium iron phosphate that can be continued to be used, thereby achieving the purpose of recycling. This process supplements the lithium source that is consumed more during the use of the battery, and repairs the crystal structure of the lithium iron phosphate. The process is simple, green and pollution-free, and has a high recovery efficiency.

[0043] In some embodiments, the organoalcohol solution comprises an organic alcohol and water;

[0044] The volume ratio of organic alcohol to water is (3-40):(5-35).

[0045] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium acetate, and lithium sulfate;

[0046] The reducing agent includes at least one of sodium sulfite, L-threonine, tartaric acid and citric acid.

[0047] In some embodiments, the mass volume ratio of waste lithium iron phosphate, reducing agent, and organic alcohol solution is (1-5) g: (0.1-8) g (15-200) mL.

[0048] In some embodiments, waste lithium iron phosphate and a lithium source are added to an organic alcohol solution so that the final concentration of the lithium source is 5 to 20 g / L.

[0049] In some embodiments, in the step of subjecting the mixed solution to a hydrothermal reaction, the hydrothermal reaction temperature is 160-220° C. and the reaction time is 3-8 h.

[0050] In some embodiments, the mixed solution is subjected to a hydrothermal reaction, filtered after the reaction is completed, and dried at 50-100° C. to obtain a repaired lithium-ion battery positive electrode material.

[0051] In some embodiments, a method for repairing waste lithium iron phosphate battery positive electrode materials comprises the following steps:

[0052] S1. Pour 50 mL of a mixed solution of organic alcohol (diethylene glycol or triethylene glycol) and deionized water (volume ratio: 7:3) into a beaker at room temperature to obtain an organic alcohol solution;

[0053] S2. Weigh 1-5 g of waste lithium iron phosphate, 0.1-8 g of a reducing agent, and 5-20 g / L of a lithium source at room temperature (20-25° C.), add the organic alcohol solution in step S1, and stir to dissolve to form a mixed solution;

[0054] S3, pour the mixed solution in S2 into the polytetrafluoroethylene liner at room temperature;

[0055] The polytetrafluoroethylene liner is placed in a stainless steel reactor lined with Teflon, and then placed in a drying oven for hydrothermal reaction; wherein the temperature of the drying oven is set to 160-220°C, and the reaction time is set to 3-8 hours;

[0056] S4, filtration and collection: At room temperature, after the reaction in step S3 is complete, remove the polytetrafluoroethylene liner from the stainless steel reactor, pour the solution into a filtration device for filtration, and collect the powder with filter paper;

[0057] S5, drying: at room temperature, the powder collected in step S4 is placed in a drying oven and dried at 80° C. for more than 8 hours, and the dried powder is collected to complete the repair of the waste lithium iron phosphate battery positive electrode material, thereby obtaining a repaired lithium-ion battery positive electrode material.

[0058] Preferably, the ratio of the lithium source in step S2 of the above technical solution is preferably 6 g / L, 9 g / L, 12 g / L, or 16 g / L; the ratio of the reducing agent is preferably 0.6, 4 g, 6 g, or 8 g.

[0059] Based on the same inventive concept, the present invention also provides a lithium-ion battery positive electrode material, which is repaired using the above-mentioned repair method.

[0060] Based on the same inventive concept, the present invention also provides a lithium ion battery positive electrode, comprising a positive electrode current collector and a positive electrode slurry coated on the positive electrode current collector;

[0061] The positive electrode slurry includes a binder, a conductive agent, a solvent and the lithium ion battery positive electrode material obtained by the above-mentioned repair method or the above-mentioned lithium ion battery positive electrode material.

[0062] Specifically, the binder can be PVDF (polyvinylidene fluoride), conductive carbon black is the conductive agent, and the solvent is N-methylpyrrolidone (NMP); first, PVDF is added to NMP to form a PVDF solution, wherein the mass fraction of PVDF is 5%; the PVDF solution, the conductive agent, and the lithium-ion battery positive electrode material obtained by the above-mentioned repair method are evenly mixed to obtain an electrode slurry; using carbon-coated aluminum foil as a current collector, the electrode slurry is coated on the current collector to obtain a lithium-ion battery positive electrode material; wherein, the lithium-ion battery positive electrode material obtained by the above-mentioned repair method, conductive carbon black, and PVDF are added in a ratio of 80 mg:10 mg:10 mg, and the volume of the PVDF solution is 200 μL; the length of the carbon-coated aluminum foil is 4 cm and the width is 3 cm.

[0063] Based on the same inventive concept, the present invention also provides a use of the above-mentioned lithium-ion battery positive electrode material or the above-mentioned lithium-ion battery positive electrode in the preparation of a lithium battery.

[0064] Based on the same inventive concept, the present invention also provides a lithium-ion battery, comprising a positive electrode, which is the positive electrode of the lithium-ion battery described above.

[0065] The following further illustrates the present invention's methods and applications for repairing waste lithium iron phosphate battery cathode materials and lithium-ion batteries using specific examples. This section further illustrates the present invention with reference to specific examples but should not be construed as limiting the present invention. Unless otherwise specified, the techniques employed in the examples are conventional techniques well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment employed in the present invention are conventional in the art.

[0066] The waste lithium iron phosphate in the following examples and comparative examples comes from Wuhan Power Battery Recycling Technology Co., Ltd.

[0067] Example 1

[0068] This embodiment provides a method for repairing waste lithium iron phosphate battery positive electrode materials, comprising the following steps:

[0069] S1. Mix 35 mL of deionized water and 15 mL of triethylene glycol at room temperature (25°C) to obtain an organic alcohol solution;

[0070] S2. Weigh 5 g of waste lithium iron phosphate, 6 g of sodium sulfite, and lithium sulfate at room temperature and add them to the organic alcohol solution, stirring and dissolving to form a mixed solution; wherein the amount of lithium sulfate added is 0.45 g so that the lithium sulfate concentration is 9 g / L;

[0071] S3, pour the mixed solution in S2 into the polytetrafluoroethylene liner at room temperature;

[0072] The polytetrafluoroethylene liner was placed in a stainless steel reactor lined with Teflon, and then placed in a drying oven for hydrothermal reaction; wherein the temperature of the drying oven was set to 200°C and the reaction time was set to 6 hours;

[0073] S4, filtration and collection: At room temperature, after the reaction in step S3 is complete, remove the polytetrafluoroethylene liner from the stainless steel reactor, pour the solution into a filtration device for filtration, and collect the powder with filter paper;

[0074] S5. Drying: At room temperature, the powder collected in step S4 is placed in a drying oven at 80° C. and dried for 8 hours. The dried powder is collected to complete the repair of the waste lithium iron phosphate battery positive electrode material and obtain a repaired lithium-ion battery positive electrode material.

[0075] This embodiment also provides a lithium-ion battery positive electrode material, including a positive electrode current collector and a positive electrode slurry coated on the positive electrode current collector;

[0076] The positive electrode slurry includes a binder, a conductive agent, a solvent and the lithium ion battery positive electrode material obtained by the repair method in Example 1;

[0077] The binder is PVDF (polyvinylidene fluoride), the conductive carbon black is the conductive agent, and the solvent is N-methylpyrrolidone (NMP); first, PVDF is added to NMP to form a PVDF solution, wherein the mass fraction of PVDF in the PVDF solution is 5%; the PVDF solution, the conductive agent, and the lithium ion battery positive electrode material obtained by the repair method in Example 1 are evenly mixed to obtain an electrode slurry; a carbon-coated aluminum foil is used as a current collector, and the electrode slurry is coated on the current collector to obtain a lithium ion battery positive electrode material; wherein, the lithium ion battery positive electrode material obtained by the above-mentioned repair method, the conductive carbon black, and the PVDF addition ratio are 80 mg:10 mg:10 mg, and the volume of the PVDF solution is 200 μL; the carbon-coated aluminum foil has a length of 4 cm and a width of 3 cm.

[0078] This embodiment also provides a lithium-ion battery, including a positive electrode material, a negative electrode material, an electrolyte, and a separator;

[0079] Wherein, the positive electrode material is the positive electrode material of the lithium ion battery in the above embodiment 1;

[0080] The negative electrode material is lithium sheet;

[0081] The electrolyte is: 1M LiPF6 (DMC:EC:EMC=1:1:1Vcl%), that is, the solute is lithium hexafluorophosphate (LiPF6), the solvents are DMC (dimethyl carbonate), EC (ethylene carbonate), and EMC (ethyl methyl carbonate), the volume ratio of DMC, EC, and EMC is 1:1:1, and the concentration of LiPF6 is 1M (mol / L);

[0082] The diaphragm is a PE diaphragm.

[0083] The lithium-ion battery in Example 1 has a specific capacity of 145 mAh / g after 200 cycles of charge and discharge at a current density of 0.5 C.

[0084] Example 2

[0085] This embodiment provides a method for repairing waste lithium iron phosphate battery positive electrode materials, comprising the following steps:

[0086] S1. Mix 10.5 mL of deionized water and 4.5 mL of triethylene glycol at room temperature (25°C) to obtain an organic alcohol solution;

[0087] S2. Weigh 1 g of waste lithium iron phosphate, 180 mg of lithium acetate (to a concentration of 12 g / L), and 180 mg of L-threonine at room temperature and add them to the organic alcohol solution, stirring and dissolving to form a mixed solution;

[0088] S3, pour the mixed solution in S2 into the polytetrafluoroethylene liner at room temperature;

[0089] The polytetrafluoroethylene liner was placed in a stainless steel reactor lined with Teflon, and then placed in a drying oven for hydrothermal reaction; wherein the temperature of the drying oven was set to 180°C and the reaction time was set to 6 hours;

[0090] S4, filtration and collection: At room temperature, after the reaction in step S3 is complete, remove the polytetrafluoroethylene liner from the stainless steel reactor, pour the solution into a filtration device for filtration, and collect the powder with filter paper;

[0091] S5. Drying: At room temperature, the powder collected in step S4 is placed in a drying oven at 80° C. and dried for 8 hours. The dried powder is collected to complete the repair of the waste lithium iron phosphate battery positive electrode material and obtain a repaired lithium-ion battery positive electrode material.

[0092] This embodiment also provides a lithium-ion battery positive electrode material, including a positive electrode current collector and a positive electrode slurry coated on the positive electrode current collector;

[0093] The positive electrode slurry includes a binder, a conductive agent, a solvent, and the lithium-ion battery positive electrode material obtained by the repair method in Example 2;

[0094] The binder is PVDF (polyvinylidene fluoride), the conductive carbon black is the conductive agent, and the solvent is N-methylpyrrolidone (NMP); first, PVDF is added to NMP to form a PVDF solution, wherein the mass fraction of PVDF in the PVDF solution is 5%; the PVDF solution, the conductive agent, and the lithium ion battery positive electrode material obtained by the repair method in Example 2 are evenly mixed to obtain an electrode slurry; a carbon-coated aluminum foil is used as a current collector, and the electrode slurry is coated on the current collector to obtain a lithium ion battery positive electrode material; wherein, the lithium ion battery positive electrode material obtained by the above-mentioned repair method, the conductive carbon black, and the PVDF addition ratio are 80 mg:10 mg:10 mg, and the volume of the PVDF solution is 200 μL; the carbon-coated aluminum foil has a length of 4 cm and a width of 3 cm.

[0095] This embodiment also provides a lithium-ion battery, including a positive electrode material, a negative electrode material, an electrolyte, and a separator;

[0096] Wherein, the positive electrode material is the positive electrode material of the lithium ion battery in the above embodiment 2;

[0097] The negative electrode material is lithium sheet;

[0098] The electrolyte is: 1M LiPF6 (DMC:EC:EMC=1:1:1Vcl%), that is, the solute is lithium hexafluorophosphate (LiPF6), the solvents are DMC (dimethyl carbonate), EC (ethylene carbonate), and EMC (ethyl methyl carbonate), the volume ratio of DMC, EC, and EMC is 1:1:1, and the concentration of LiPF6 is 1M (mol / L);

[0099] The diaphragm is a PE diaphragm.

[0100] The lithium-ion battery in Example 2 has a specific capacity of 153 mAh / g after 200 cycles of charge and discharge at a current density of 0.5 C.

[0101] Example 3

[0102] This embodiment provides a method for repairing waste lithium iron phosphate battery positive electrode materials, comprising the following steps:

[0103] S1. Mix 35 mL of deionized water and 15 mL of triethylene glycol at room temperature (25°C) to obtain an organic alcohol solution;

[0104] S2. Add 3 g of waste lithium iron phosphate, 0.08 M tartaric acid (0.6 g) and 0.2 M lithium acetate monohydrate (0.84 g) to the organic alcohol solution at room temperature, and stir to dissolve to form a mixed solution;

[0105] S3, pour the mixed solution in S2 into the polytetrafluoroethylene liner at room temperature;

[0106] The polytetrafluoroethylene liner was placed in a stainless steel reactor lined with Teflon, and then placed in a drying oven for hydrothermal reaction; wherein the temperature of the drying oven was set to 200°C and the reaction time was set to 3 hours;

[0107] S4, filtration and collection: At room temperature, after the reaction in step S3 is complete, remove the polytetrafluoroethylene liner from the stainless steel reactor, pour the solution into a filtration device for filtration, and collect the powder with filter paper;

[0108] S5. Drying: At room temperature, the powder collected in step S4 is placed in a drying oven at 80° C. and dried for 8 hours. The dried powder is collected to complete the repair of the waste lithium iron phosphate battery positive electrode material and obtain a repaired lithium-ion battery positive electrode material.

[0109] This embodiment also provides a lithium-ion battery positive electrode material, including a positive electrode current collector and a positive electrode slurry coated on the positive electrode current collector;

[0110] The positive electrode slurry includes a binder, a conductive agent, a solvent, and the lithium-ion battery positive electrode material obtained by the repair method in Example 2;

[0111] The binder is PVDF (polyvinylidene fluoride), the conductive carbon black is the conductive agent, and the solvent is N-methylpyrrolidone (NMP); first, PVDF is added to NMP to form a PVDF solution, wherein the mass fraction of PVDF in the PVDF solution is 5%; the PVDF solution, the conductive agent, and the lithium ion battery positive electrode material obtained by the repair method in Example 3 are evenly mixed to obtain an electrode slurry; a carbon-coated aluminum foil is used as a current collector, and the electrode slurry is coated on the current collector to obtain a lithium ion battery positive electrode material; wherein, the lithium ion battery positive electrode material obtained by the above-mentioned repair method, the conductive carbon black, and the PVDF addition ratio are 80 mg:10 mg:10 mg, and the volume of the PVDF solution is 200 μL; the carbon-coated aluminum foil has a length of 4 cm and a width of 3 cm.

[0112] This embodiment also provides a lithium-ion battery, including a positive electrode material, a negative electrode material, an electrolyte, and a separator;

[0113] The positive electrode material is the positive electrode material of the lithium-ion battery in the above embodiment 3;

[0114] The negative electrode material is lithium sheet;

[0115] The electrolyte is: 1M LiPF6 (DMC:EC:EMC=1:1:1Vcl%), that is, the solute is lithium hexafluorophosphate (LiPF6), the solvents are DMC (dimethyl carbonate), EC (ethylene carbonate), and EMC (ethyl methyl carbonate), the volume ratio of DMC, EC, and EMC is 1:1:1, and the concentration of LiPF6 is 1M (mol / L);

[0116] The diaphragm is a PE diaphragm.

[0117] The lithium-ion battery in Example 3 has a specific capacity of 148 mAh / g after 200 cycles of charge and discharge at a current density of 0.5 C.

[0118] Comparative Example 1

[0119] Our team provides a method for repairing waste lithium iron phosphate battery positive electrode materials, which is the same as Example 2, except that ethanol is used instead of triethylene glycol in step S2, and the other process parameters are the same as Example 2.

[0120] This comparative example also provides a lithium-ion battery positive electrode material, including a positive electrode current collector and a positive electrode slurry coated on the positive electrode current collector;

[0121] The positive electrode slurry includes a binder, a conductive agent, a solvent and the lithium ion battery positive electrode material obtained by the repair method in Comparative Example 1;

[0122] The binder is PVDF (polyvinylidene fluoride), the conductive carbon black is the conductive agent, and the solvent is N-methylpyrrolidone (NMP); first, PVDF is added to NMP to form a PVDF solution, wherein the mass fraction of PVDF in the PVDF solution is 5%; the PVDF solution, the conductive agent, and the lithium ion battery positive electrode material obtained by the repair method in Comparative Example 1 are evenly mixed to obtain an electrode slurry; a carbon-coated aluminum foil is used as a current collector, and the electrode slurry is applied to the current collector to obtain a lithium ion battery positive electrode material; wherein, the lithium ion battery positive electrode material obtained by the above-mentioned repair method, the conductive carbon black, and the PVDF addition ratio are 80 mg:10 mg:10 mg, and the volume of the PVDF solution is 200 μL; the carbon-coated aluminum foil has a length of 4 cm and a width of 3 cm.

[0123] This embodiment also provides a lithium-ion battery, including a positive electrode material, a negative electrode material, an electrolyte, and a separator;

[0124] Wherein, the positive electrode material is the positive electrode material of the lithium ion battery in the above comparative example 1;

[0125] The negative electrode material is lithium sheet;

[0126] The electrolyte is: 1M LiPF6 (DMC:EC:EMC=1:1:1Vcl%), that is, the solute is lithium hexafluorophosphate (LiPF6), the solvents are DMC (dimethyl carbonate), EC (ethylene carbonate), and EMC (ethyl methyl carbonate), the volume ratio of DMC, EC, and EMC is 1:1:1, and the concentration of LiPF6 is 1M (mol / L);

[0127] The diaphragm is a PE diaphragm.

[0128] Performance Testing

[0129] Figures 1-2 The following are scanning electron microscope (SEM) images of waste lithium iron phosphate (S-LFP) in Example 2 of the present invention at different magnifications; Figure 1 It can be seen that waste lithium iron phosphate LFP is a sheet structure with a width (100-200nm) and a length (2-4μm) uniformly distributed in space.

[0130] Figures 3-4 These are scanning electron microscope (SEM) images of the lithium-ion battery positive electrode material after repairing the waste lithium iron phosphate material in Example 2 of the present invention at different magnifications.

[0131] from Figures 1-2 and Figures 3-4 By comparison, it can be seen that the nanosheets of the lithium-ion battery positive electrode material obtained after repair have become regular and complete compared with the waste lithium iron phosphate LFP.

[0132] Figure 5The XRD patterns of the repaired lithium-ion battery cathode material and the initial waste lithium iron phosphate (S-LFP) obtained by the repair method in Examples 1 to 3; Figure 5 R-LFP3 is Example 3, R-LFP2 is Example 2, R-LFP1 is Example 1, and S-LFP is the initial waste lithium iron phosphate.

[0133] from Figure 5 It can be seen that in Examples 1 to 3, the interlayer spacing between the crystal planes becomes larger due to the re-replenishment of lithium, so that all XRD peaks correspond to the commercial LFP peaks one by one.

[0134] Figure 6 This is a CV image of a lithium-ion battery assembled from the lithium-ion battery cathode material repaired from waste lithium iron phosphate material in Example 2 at a low scan rate of 0.1 mv / s. Figure 7 These are CV images of lithium-ion batteries assembled from the lithium-ion battery cathode material repaired from the waste lithium iron phosphate material in Example 2 at different scanning rates.

[0135] from Figures 6-7 It can be seen that the CV curves of the second and third circles basically coincide with each other, indicating that the charge and discharge process is highly reversible and also reflects the stability of its structure.

[0136] Figure 8 Lithium-ion batteries assembled from waste lithium iron phosphate ( Figure 8 S-LFP) and the lithium ion battery positive electrode material assembled from the waste lithium iron phosphate material repaired in Example 2 of the present invention ( Figure 8 Rate performance comparison chart of R-LFP).

[0137] Figure 9 Lithium-ion batteries assembled from waste lithium iron phosphate ( Figure 9 S-LFP) and the lithium ion battery positive electrode material assembled from the waste lithium iron phosphate material repaired in Example 2 of the present invention ( Figure 9 Comparison of the cycling performance of R-LFP) at a current density of 0.2C.

[0138] from Figures 8-9 It can be seen that the cycle performance of the repaired LFP at different rates is significantly higher than that of S-LFP, indicating that it has been successfully repaired, and the coulombic efficiency of the repaired battery ( Figures 8-9 The triangle mark in the middle represents the Coulomb efficiency) which is close to 100%.

[0139] Figure 10This is a comparison chart of the cycling performance at a current density of 0.5C of a lithium ion battery assembled with a lithium ion battery positive electrode material after repairing waste lithium iron phosphate material using ethanol (EG) as a co-solvent and a lithium ion battery assembled with a lithium ion battery positive electrode material after repairing waste lithium iron phosphate material using triethylene glycol (TEG) in Example 2 of the present invention.

[0140] from Figure 10 It can be seen that the lithium-ion battery positive electrode material after using triethylene glycol (TEG) to repair the waste lithium iron phosphate material has higher capacity and better performance, and triethylene glycol has more advantages than ethanol.

[0141] Figure 11 Lithium-ion batteries assembled from waste lithium iron phosphate ( Figure 11 S-LFP) and the lithium ion battery positive electrode material assembled from the waste lithium iron phosphate material repaired in Example 2 of the present invention ( Figure 11 Impedance comparison diagram of R-LFP).

[0142] Depend on Figure 11 It can be seen that the internal resistance of the repaired battery has decreased and its conductivity has increased.

[0143] It can be understood that the various technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0144] The above are merely preferred embodiments of the present application and only specifically describe the technical principles of the present application. These descriptions are intended only to explain the principles of the present application and should not be construed in any way as limiting the scope of protection of the present application. Based on the explanations herein, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application, as well as other specific implementations of the present application that can be conceived by those skilled in the art without inventive effort, shall be included within the scope of protection of the present application.

Claims

1. A method for repairing waste lithium iron phosphate battery positive electrode materials, characterized in that: The following steps are involved: Adding waste lithium iron phosphate and lithium source into an organic alcohol solution, then adding a reducing agent and stirring to obtain a mixed solution; The mixed solution is subjected to a hydrothermal reaction, filtered, and dried to complete the repair of the waste lithium iron phosphate battery positive electrode material to obtain a repaired lithium-ion battery positive electrode material; Wherein, the organic alcohol includes at least one of diethylene glycol and triethylene glycol.

2. The method for repairing waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: The organic alcohol solution comprises organic alcohol and water; The volume ratio of the organic alcohol to water is (3-40):(5-35).

3. The method for repairing waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: The lithium source includes at least one of lithium hydroxide, lithium acetate, and lithium sulfate; The reducing agent includes at least one of sodium sulfite, L-threonine, tartaric acid, and citric acid.

4. The method for repairing waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: The mass volume ratio of the waste lithium iron phosphate, reducing agent and organic alcohol solution is (1-5) g: (0.1-8) g (15-200) mL; Waste lithium iron phosphate and a lithium source are added to an organic alcohol solution so that the final concentration of the lithium source is 5 to 20 g / L.

5. The method for repairing waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: In the step of subjecting the mixed solution to a hydrothermal reaction, the hydrothermal reaction temperature is 160 to 220° C. and the reaction time is 3 to 8 hours.

6. The method for repairing waste lithium iron phosphate battery positive electrode materials according to claim 1, characterized in that: The mixed solution is subjected to a hydrothermal reaction, filtered after the reaction is completed, and dried at 50-100° C. to obtain a repaired lithium-ion battery positive electrode material.

7. A positive electrode material for a lithium ion battery, characterized in that: The repaired product is obtained by using the repair method according to any one of claims 1 to 6.

8. A lithium ion battery positive electrode, characterized in that It includes a positive electrode current collector and a positive electrode slurry coated on the positive electrode current collector; The positive electrode slurry comprises a binder, a conductive agent, a solvent, and the lithium-ion battery positive electrode material obtained by the repair method according to any one of claims 1 to 6 or the lithium-ion battery positive electrode material according to claim 7.

9. Use of the lithium ion battery positive electrode material according to claim 7 or the lithium ion battery positive electrode according to claim 8 in the preparation of a lithium battery.

10. A lithium ion battery, characterized in that: The positive electrode comprises a positive electrode, wherein the positive electrode is the positive electrode of the lithium ion battery according to claim 8.

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