Method for regenerating lithium iron phosphate positive electrode material by wet grinding, positive electrode plate and battery

Abstract

The invention discloses a method for regenerating a lithium iron phosphate positive electrode material by wet grinding, a positive electrode plate and a battery, and relates to the technical field of battery materials, the method comprises the following steps: pre-treating a waste lithium iron phosphate material to obtain a pre-treated lithium iron phosphate positive electrode plate; immersing the pretreated lithium iron phosphate positive plate in a deionized liquid to obtain stripped lithium iron phosphate; preparing a lithium supplementing solution, immersing the stripped lithium iron phosphate into the lithium supplementing solution to obtain a lithium supplementing mixed solution, and grinding the lithium supplementing mixed solution for a first preset time to obtain a reacted mixture; and separating a solid in the reacted mixture, and drying the solid to obtain the regenerated lithium iron phosphate material. According to the present invention, the positive electrode material of the waste lithium iron phosphate battery can be refined and homogenized, the reaction activity of the material is improved, and the lithium salt is configured in the grinding liquid phase so as to supplement the defective lithium element in the retired lithium iron phosphate, such that the electrochemical performance of the prepared regenerated lithium iron phosphate is improved.

Description

Technical Field

[0001] The present application relates to the technical field of battery materials, and in particular to a method for wet grinding and regenerating lithium iron phosphate positive electrode materials, a positive electrode sheet and a battery. Background Art

[0002] As an important member of modern energy storage, lithium iron phosphate batteries have outstanding performance in new energy vehicles, large energy storage systems and portable electronic devices. Usually, the number of cycles of lithium iron phosphate batteries is generally between 500 and 2000 times. After reaching a service life of 3 to 5 years, they will be retired. The main reason for battery retirement is that lithium iron phosphate battery positive electrode materials have lithium vacancy defects during charging and discharging, and lithium sites are occupied by iron, resulting in iron oxidation, while inducing some Fe in its own structure to 2+ Migrate to the lithium site, forming a reaction defect, thereby blocking the Li 2+ diffusion pathway.

[0003] In some related technologies, retired lithium iron phosphate batteries are directly landfilled or disposed of inappropriately, and the toxic organic matter, organic electrolyte and metal ions contained in them will gradually seep into the soil and groundwater, which will cause environmental pollution and waste of resources. The traditional wet recovery technology has the problems of long process flow, cumbersome operation, high production of high-salt wastewater and low economic feasibility; while other solid-phase sintering, electrochemical and hydrothermal methods require high reaction temperature for the regeneration of waste lithium iron phosphate, and there is uneven distribution of particles during the lithium replenishment process, which has poor effect on replenishing lithium-deficient sites. Summary of the invention

[0004] In order to solve at least one of the problems mentioned in the above background technology, the present application provides a method for wet grinding and regenerating lithium iron phosphate positive electrode materials, a positive electrode plate and a battery, which can refine and homogenize the positive electrode materials of waste lithium iron phosphate batteries and improve the reaction activity of the materials. By configuring lithium salt in the ball milling liquid phase to supplement the missing lithium element in the retired lithium iron phosphate, the electrochemical properties of the prepared regenerated lithium iron phosphate can be improved.

[0005] The specific technical solutions provided by the embodiments of this application are as follows:

[0006] In a first aspect, a method for wet grinding and regenerating a lithium iron phosphate positive electrode material is provided, the method comprising:

[0007] Pre-processing the waste lithium iron phosphate material to obtain the pre-processed lithium iron phosphate positive electrode sheet;

[0008] Immersing the pretreated lithium iron phosphate positive electrode sheet in a deionized liquid to obtain the stripped lithium iron phosphate;

[0009] preparing a lithium replenishing solution, immersing the stripped lithium iron phosphate in the lithium replenishing solution to obtain a lithium replenishing mixed solution, and grinding the lithium replenishing mixed solution for a first preset time to obtain a reacted mixture;

[0010] The solid in the reaction mixture is separated and dried to obtain the regenerated lithium iron phosphate material.

[0011] In a specific embodiment, immersing the pretreated lithium iron phosphate positive electrode sheet in a deionized liquid to obtain the stripped lithium iron phosphate specifically includes:

[0012] The pretreated lithium iron phosphate positive electrode sheet is immersed in deionized water and maintained for a second preset time to obtain separated lithium iron phosphate; the separated lithium iron phosphate is placed in a constant temperature device for drying to obtain the stripped lithium iron phosphate.

[0013] In a specific embodiment, the temperature of the deionized liquid is set to 60-100° C., and the second preset time is 3-5 minutes; the drying temperature in the constant temperature device is 80-120° C., and the drying time in the constant temperature device is 24-48 hours.

[0014] In a specific embodiment, the stripped lithium iron phosphate is in the form of flakes or particles, and the surface area of ​​the stripped lithium iron phosphate is in the range of 1.5 to 4 mm 2 ; The particle size of the granular lithium iron phosphate peeled off is 20 to 100 mesh.

[0015] In a specific embodiment, a lithium replenishing solution is prepared, and the stripped lithium iron phosphate is immersed in the lithium replenishing solution to obtain a lithium replenishing mixed solution, and the lithium replenishing mixed solution is ground for a first preset time to obtain a reacted mixture, specifically comprising: mixing a lithium salt, a reducing substance, and a polar solvent in a preset proportion to form a mixed solution, and adjusting the pH value of the mixed solution to a preset pH value to obtain the lithium replenishing solution; immersing the stripped lithium iron phosphate in the lithium replenishing solution to obtain a lithium replenishing mixed solution, grinding the lithium replenishing mixed solution while keeping it in a sealed state, and grinding for the first preset time to obtain a reacted mixture.

[0016] In a specific embodiment, the preset pH value is 8 to 12; the lithium supplementation mixed solution is sealed and ground in a ball mill, the grinding speed is 500 to 1500 rpm, and the grinding time is 2 to 6 hours.

[0017] In a specific embodiment, the lithium salt includes at least one or more of lithium chloride, lithium iodide, lithium phosphate, lithium carbonate, lithium hydroxide, lithium bromide, lithium nitrate, lithium sulfate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium acetate, lithium bis(oxalatoborate), lithium tetrafluoroborate or lithium acrylate;

[0018] The reducing substance includes at least one or more of lithium aluminum hydride, sodium thiocyanate, sodium sulfide, ascorbic acid, citric acid, glucose, fructose, lactose, maltose, potassium tris(1-pyrazolyl)borohydride, sodium triacetoxyborohydride, sodium sulfite, ferrous chloride tetrahydrate or stannous chloride;

[0019] The polar solvent includes at least one or more of ethanol, methanol, acetone, ethyl acetate, dimethyl sulfoxide, glycerol, acetonitrile, tetrahydrofuran, acetic acid, N,N-dimethylamide, pyridine, dimethylacetamide, dioxane, N-methylpyrrolidone or hexamethylammonium phosphate.

[0020] In a specific embodiment, a centrifugal device is used to separate the solid in the reaction mixture, wherein the rotation speed of the centrifugal device is 8000-15000 rpm; a blast oven and a vacuum oven are used to dry the solid in sequence; wherein the temperature of the blast oven drying the solid is 80-100°C, and the drying time is 8-12 hours; wherein the temperature of the vacuum oven drying the solid is 120-150°C, and the drying time is 24-48 hours.

[0021] In a second aspect, a positive electrode plate is provided, wherein the positive electrode plate is prepared by the method of wet grinding and regenerating lithium iron phosphate positive electrode material as described above.

[0022] In a third aspect, a battery is provided, wherein the battery comprises the positive electrode plate as described above or the positive electrode plate in the battery is prepared by the method for wet grinding and regenerating lithium iron phosphate positive electrode material as described above.

[0023] The embodiments of the present application have the following beneficial effects:

[0024] 1. In the embodiment of the present application, by simultaneously using grinding during the lithium replenishment process, the particles can be refined more evenly, and the mixing uniformity and particle size distribution concentration of the lithium replenishment substance and the material to be replenished are improved, which makes the material contact closer and is conducive to a more complete lithium replenishment reaction; and through the technical solution in this embodiment, the discharge specific capacity, cycle stability and rate performance of the regenerated lithium iron phosphate material obtained by the treatment are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1A schematic diagram showing a method for wet grinding and regenerating lithium iron phosphate positive electrode materials according to the present application;

[0027] Figure 2 A schematic diagram showing the recovery test results according to the present application is shown;

[0028] Figure 3 A schematic diagram of the particle size distribution results according to the present application is shown;

[0029] Figure 4 A schematic diagram showing the XRD test results of the regenerated lithium iron phosphate material according to the present application;

[0030] Figure 5 A schematic diagram showing a rate test and a charge-discharge curve of the regenerated lithium iron phosphate material according to the present application is shown;

[0031] Figure 6 A schematic diagram showing the cycle performance of the regenerated lithium iron phosphate material in the capacitor according to the present application is shown. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0034] Embodiment 1

[0035] A method for wet grinding and regenerating lithium iron phosphate positive electrode material is provided, such as Figure 1 As shown, the method comprises the following steps:

[0036] S1. Pre-treating the waste lithium iron phosphate material to obtain a pre-treated lithium iron phosphate positive electrode sheet.

[0037] Among them, the used lithium iron phosphate batteries need to undergo different pretreatments due to the presence or absence of tabs. For retired lithium iron phosphate batteries with missing tabs, only a mechanical crushing and splitting process is required; while for retired lithium iron phosphate batteries with existing tabs, the retired lithium iron phosphate is first mechanically crushed, and then supplemented with an electrochemical discharge process, so that the lithium on the surface of the negative electrode sheet acts on the lithium vacancies of the lithium iron phosphate positive electrode material, thereby obtaining a pretreated lithium iron phosphate positive electrode sheet.

[0038] S2, immersing the pretreated lithium iron phosphate positive electrode sheet in a deionized liquid to obtain the stripped lithium iron phosphate.

[0039] In a specific embodiment, it should be noted that the deionized liquid in this embodiment is deionized water, and the process of obtaining the stripped lithium iron phosphate includes: immersing the pretreated lithium iron phosphate positive electrode sheet in deionized water and maintaining it for a second preset time to obtain the separated lithium iron phosphate; placing the separated lithium iron phosphate in a constant temperature device to dry, so as to obtain the stripped lithium iron phosphate.

[0040] The temperature of the deionized liquid is set to 60-100° C., and the second preset time is 3-5 minutes; the drying temperature in the constant temperature device is 80-120° C., and the drying time in the constant temperature device is 24-48 hours.

[0041] Specifically, the stripped lithium iron phosphate is in the form of flakes or particles, and the surface area of ​​the stripped lithium iron phosphate is in the range of 1.5 to 4 mm 2 ; The particle size of the granular lithium iron phosphate peeled off is 20 to 100 mesh.

[0042] S3, preparing a lithium replenishing solution, and immersing the stripped lithium iron phosphate in the lithium replenishing solution to obtain a lithium replenishing mixed solution, and grinding the lithium replenishing mixed solution for a first preset time to obtain a reacted mixture.

[0043] Specifically, the method comprises: mixing a lithium salt, a reducing substance and a polar solvent in a preset ratio to form a mixed solution, and adjusting the pH value of the mixed solution to a preset pH value to obtain the lithium replenishing solution; immersing the stripped lithium iron phosphate in the lithium replenishing solution to obtain a lithium replenishing mixed solution, grinding the lithium replenishing mixed solution while keeping it sealed, and obtaining a reacted mixture after grinding for a first preset time.

[0044] It should be noted that the molar mass ratio of lithium salt to reducing substance in the lithium replenishing solution is 3 to 1:2, the mixed solution also includes deionized water, the volume ratio of deionized water to polar solvent is 10 to 8:1, and the above substances are mixed according to the above ratio to form a lithium replenishing mixed solution; the preset pH value in this embodiment is 8 to 12; and the lithium replenishing mixed solution is sealed and ground using a ball mill, the grinding speed is 500 to 1500 rpm, and the grinding time is 2 to 6 hours. Wherein, zirconium oxide is contained in the ball mill.

[0045] In a specific embodiment, the lithium salt includes but is not limited to one or more of lithium chloride, lithium iodide, lithium phosphate, lithium carbonate, lithium hydroxide, lithium bromide, lithium nitrate, lithium sulfate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium acetate, lithium bis(oxalatoborate), lithium tetrafluoroborate or lithium acrylate;

[0046] The reducing substance includes, but is not limited to, one or more of lithium aluminum hydride, sodium thiocyanate, sodium sulfide, ascorbic acid, citric acid, glucose, fructose, lactose, maltose, potassium tris(1-pyrazolyl)borohydride, sodium triacetoxyborohydride, sodium sulfite, ferrous chloride tetrahydrate or stannous chloride;

[0047] The polar solvent includes, but is not limited to, one or more of ethanol, methanol, acetone, ethyl acetate, dimethyl sulfoxide, glycerol, acetonitrile, tetrahydrofuran, acetic acid, N,N-dimethylamide, pyridine, dimethylacetamide, dioxane, N-methylpyrrolidone or hexamethylammonium phosphate.

[0048] S4, separating the solid in the reaction mixture, and drying the solid to obtain the regenerated lithium iron phosphate material.

[0049] In a specific embodiment, a centrifugal device is used to separate the solid in the reaction mixture, wherein the rotation speed of the centrifugal device is 8000-15000 rpm; a blast oven and a vacuum oven are used to dry the solid in sequence; wherein the temperature of the blast oven drying the solid is 80-100°C, and the drying time is 8-12 hours; wherein the temperature of the vacuum oven drying the solid is 120-150°C, and the drying time is 24-48 hours.

[0050] The scheme in this embodiment can refine and homogenize the positive electrode material of waste lithium iron phosphate batteries, improve the reaction activity of the material, and supplement the missing lithium element in the retired lithium iron phosphate by configuring a lithium salt in the ball milling liquid phase, thereby improving the electrochemical performance of the prepared regenerated lithium iron phosphate.

[0051] Embodiment 2

[0052] Corresponding to the above embodiment, the method for wet grinding and regenerating lithium iron phosphate positive electrode material in this embodiment specifically includes:

[0053] Pre-treating the waste lithium iron phosphate material with missing tabs to obtain a pre-treated lithium iron phosphate positive electrode sheet; immersing the pre-treated lithium iron phosphate positive electrode sheet in 100° C. deionized water for 5 minutes to separate the lithium iron phosphate and the current collector to obtain separated lithium iron phosphate, and transferring the separated lithium iron phosphate to a 100° C. forced air oven for drying for 24 hours, and then transferring to a 120° C. vacuum oven for drying for 48 hours to obtain stripped lithium iron phosphate;

[0054] 0.6 mol lithium hydroxide and 0.4 mol sodium triacetoxyborohydride were dissolved in deionized water and N'N-dimethylamide in a volume ratio of 9:1, and the pH value of the mixture was adjusted to 12 to obtain a lithium supplementation mixture; 100 g, 4 mm 2 The stripped lithium iron phosphate fragments are immersed in the lithium supplementation mixture and added into a ball-ink tank containing zirconium oxide. The ball milling speed is set to 1500 rpm and the ball milling time is 6 hours to obtain a ball milling suspension, i.e., a reaction mixture.

[0055] The reaction mixture was centrifuged at 15,000 rpm and washed three times with deionizer. The mixture was dried in a 100°C blast oven for 12 h and then transferred to a 150°C vacuum oven for 48 h to obtain a gray powder, i.e., the regenerated lithium iron phosphate material. The elemental composition and content of the lithium iron phosphate were weighed and determined.

[0056] Embodiment 3

[0057] Corresponding to the above embodiment, the method for wet grinding and regenerating lithium iron phosphate positive electrode material in this embodiment specifically includes:

[0058] Pre-treating the waste lithium iron phosphate material with missing tabs to obtain a pre-treated lithium iron phosphate positive electrode sheet; immersing the pre-treated lithium iron phosphate positive electrode sheet in 80° C. deionized water for 5 minutes to separate the lithium iron phosphate and the current collector to obtain separated lithium iron phosphate, and transferring the separated lithium iron phosphate to a 100° C. forced air oven for drying for 24 hours, and then transferring to a 120° C. vacuum oven for drying for 48 hours to obtain stripped lithium iron phosphate;

[0059] 0.6 mol of lithium hydroxide and 0.4 mol of ascorbic acid were prepared and dissolved in deionized water and N-methylpyrrolidone in a volume ratio of 9:1, and the pH value of the mixture was adjusted to 8 to obtain a lithium supplementation mixture; 100 g of lithium iron phosphate powder peeled off with a mesh size of 20 was immersed in the lithium supplementation mixture, and the powder was added to a spherical ink tank containing zirconium oxide, and the ball milling speed was set to 500 rpm and the ball milling time was set to 2 hours to obtain a ball milling suspension, i.e., a reaction mixture;

[0060] The reaction mixture was centrifuged at 8000 rpm and washed three times with deionizer. The mixture was dried in a 100°C blast oven for 12 h and then transferred to a 150°C vacuum oven for 48 h to obtain a gray powder, which was the regenerated lithium iron phosphate material. The elemental composition and content of the lithium iron phosphate were weighed and determined.

[0061] Embodiment 4

[0062] Corresponding to the above embodiment, the method for wet grinding and regenerating lithium iron phosphate positive electrode material in this embodiment specifically includes:

[0063] The waste lithium iron phosphate material with the tabs is subjected to electrochemical discharge and mechanical crushing and splitting pretreatment in sequence to obtain a pretreated lithium iron phosphate positive electrode sheet; the pretreated lithium iron phosphate positive electrode sheet is immersed in 100° C. deionized water for 5 minutes to separate the lithium iron phosphate and the current collector to obtain separated lithium iron phosphate, and the separated lithium iron phosphate is transferred to a 100° C. forced air oven for drying for 24 hours, and then transferred to a 120° C. vacuum oven for drying for 48 hours to obtain the stripped lithium iron phosphate;

[0064] 0.6 mol lithium hydroxide and 0.4 mol sodium triacetoxyborohydride were dissolved in deionized water and N'N-dimethylamide in a volume ratio of 9:1, and the pH value of the mixture was adjusted to 12 to obtain a lithium supplementation mixture; 100 g, 1.5 mm 2 The stripped lithium iron phosphate fragments are immersed in the lithium supplementation mixture and added into a ball-ink tank containing zirconium oxide. The ball milling speed is set to 1500 rpm and the ball milling time is 6 hours to obtain a ball milling suspension, i.e., a reaction mixture.

[0065] The reaction mixture was centrifuged at 15,000 rpm and washed three times with deionizer. The mixture was dried in a 100°C blast oven for 12 h and then transferred to a 150°C vacuum oven for 48 h to obtain a gray powder, i.e., the regenerated lithium iron phosphate material. The elemental composition and content of the lithium iron phosphate were weighed and determined.

[0066] Embodiment 5

[0067] Corresponding to the above embodiment, the method for wet grinding and regenerating lithium iron phosphate positive electrode material in this embodiment specifically includes:

[0068] The waste lithium iron phosphate material with the tabs is subjected to electrochemical discharge and mechanical crushing and splitting pretreatment in sequence to obtain a pretreated lithium iron phosphate positive electrode sheet; the pretreated lithium iron phosphate positive electrode sheet is immersed in 100° C. deionized water for 5 minutes to separate the lithium iron phosphate and the current collector to obtain separated lithium iron phosphate, and the separated lithium iron phosphate is transferred to a 100° C. forced air oven for drying for 24 hours, and then transferred to a 120° C. vacuum oven for drying for 48 hours to obtain the stripped lithium iron phosphate;

[0069] 0.6 mol of lithium hydroxide and 0.4 mol of ascorbic acid were prepared and dissolved in deionized water and N'N-dimethylamide in a volume ratio of 9:1, and the pH value of the mixture was adjusted to 8 to obtain a lithium supplementation mixture; 100 g of 100-mesh lithium iron phosphate fragments peeled off were immersed in the lithium supplementation mixture, and added to a spherical ink tank filled with zirconium oxide, and the ball milling speed was set to 1000 rpm and the ball milling time was 4 hours to obtain a ball milling suspension, i.e., a reaction mixture;

[0070] The reaction mixture was centrifuged at 12,000 rpm and washed three times with deionizer. The mixture was dried in a 100°C blast oven for 12 h and then transferred to a 150°C vacuum oven for 48 h to obtain a gray powder, which was the regenerated lithium iron phosphate material. The elemental composition and content of the lithium iron phosphate were weighed and determined.

[0071] Embodiment 6

[0072] Corresponding to the above embodiment, the method for wet grinding and regenerating lithium iron phosphate positive electrode material in this embodiment specifically includes:

[0073] The waste lithium iron phosphate material is pre-treated by electrochemical discharge or mechanical crushing and splitting to obtain a pre-treated lithium iron phosphate positive electrode sheet; the pre-treated lithium iron phosphate positive electrode sheet is immersed in 80° C. deionized water for 5 minutes to separate the lithium iron phosphate and the current collector to obtain separated lithium iron phosphate, and the separated lithium iron phosphate is transferred to a 100° C. forced air oven for drying for 24 hours, and then transferred to a 120° C. vacuum oven for drying for 48 hours to obtain the stripped lithium iron phosphate;

[0074] 0.6 mol lithium phosphate and 0.4 mol ascorbic acid were dissolved in deionized water and N-methylpyrrolidone in a volume ratio of 9:1, and the pH value of the mixture was adjusted to 10 to obtain a lithium supplementation mixture; 50 g, 4 mm 2 The stripped lithium iron phosphate fragments and 50 g of the stripped lithium iron phosphate powder of 20 mesh were mixed and immersed in the lithium supplement mixture, and added to the ball ink tank filled with zirconium oxide at the same time, and the ball milling speed was set to 1200 rpm and the ball milling time was 4 hours to obtain a ball milling suspension, i.e., a reaction mixture;

[0075] The reaction mixture was centrifuged at 15,000 rpm and washed three times with deionizer. The mixture was dried in a 100°C blast oven for 12 h and then transferred to a 150°C vacuum oven for 48 h to obtain a gray powder, i.e., the regenerated lithium iron phosphate material. The elemental composition and content of the lithium iron phosphate were weighed and determined.

[0076] Embodiment 7

[0077] Corresponding to the above embodiment, the method for wet grinding and regenerating lithium iron phosphate positive electrode material in this embodiment specifically includes:

[0078] The waste lithium iron phosphate material is pretreated by electrochemical discharge or mechanical crushing and splitting to obtain a pretreated lithium iron phosphate positive electrode sheet; the pretreated lithium iron phosphate positive electrode sheet is immersed in 100° C. deionized water for 3 minutes to separate the lithium iron phosphate and the current collector to obtain separated lithium iron phosphate, and the separated lithium iron phosphate is transferred to a 100° C. forced air oven for drying for 24 hours, and then transferred to a 120° C. vacuum oven for drying for 48 hours to obtain the stripped lithium iron phosphate;

[0079] 0.6 mol lithium hydroxide and 0.4 mol ascorbic acid were dissolved in deionized water and N'N-dimethylamide in a volume ratio of 9:1, and the pH value of the mixture was adjusted to 10 to obtain a lithium supplementation mixture; 50 g, 1.5 mm 2 The stripped lithium iron phosphate fragments and 50 g of 100-mesh stripped lithium iron phosphate powder were mixed and immersed in the lithium supplement mixture, and added into a ball ink tank containing zirconium oxide at the same time, and the ball milling speed was set to 1500 rpm and the ball milling time was 4 hours to obtain a ball milling suspension, i.e., a reaction mixture;

[0080] The reaction mixture was centrifuged at 15,000 rpm and washed three times with deionizer. The mixture was dried in a 100°C blast oven for 12 h and then transferred to a 150°C vacuum oven for 48 h to obtain a gray powder, i.e., the regenerated lithium iron phosphate material. The elemental composition and content of the lithium iron phosphate were weighed and determined.

[0081] Embodiment 8

[0082] Corresponding to the above embodiment, the method for wet grinding and regenerating lithium iron phosphate positive electrode material in this embodiment specifically includes:

[0083] The waste lithium iron phosphate material is pretreated by electrochemical discharge or mechanical crushing and splitting to obtain a pretreated lithium iron phosphate positive electrode sheet; the pretreated lithium iron phosphate positive electrode sheet is immersed in 60° C. deionized water for 4 minutes to separate the lithium iron phosphate and the current collector to obtain separated lithium iron phosphate, and the separated lithium iron phosphate is transferred to a 100° C. forced air oven for drying for 24 hours, and then transferred to a 120° C. vacuum oven for drying for 48 hours to obtain the stripped lithium iron phosphate;

[0084] 0.6 mol lithium phosphate and 0.4 mol ascorbic acid were dissolved in deionized water and N'N-dimethylamide in a volume ratio of 9:1, and the pH value of the mixture was adjusted to 8 to obtain a lithium supplementation mixture; 50 g, 1.5 mm 2 The stripped lithium iron phosphate fragments and 50g, 4mm 2 The stripped lithium iron phosphate fragments are mixed and immersed in the lithium supplement mixture, and added into the spherical ink tank containing zirconium oxide, and the ball milling speed is set to 1500 rpm and the ball milling time is 6 hours to obtain a ball milling suspension, that is, a reaction mixture;

[0085] The reaction mixture was centrifuged at 15,000 rpm and washed three times with deionizer. The mixture was dried in a 100°C blast oven for 12 h and then transferred to a 150°C vacuum oven for 48 h to obtain a gray powder, i.e., the regenerated lithium iron phosphate material. The elemental composition and content of the lithium iron phosphate were weighed and determined.

[0086] Embodiment 9

[0087] Corresponding to the above embodiment, the method for wet grinding and regenerating lithium iron phosphate positive electrode material in this embodiment specifically includes:

[0088] The waste lithium iron phosphate material is pre-treated by electrochemical discharge or mechanical crushing and splitting to obtain a pre-treated lithium iron phosphate positive electrode sheet; the pre-treated lithium iron phosphate positive electrode sheet is immersed in 60° C. deionized water for 5 minutes to separate the lithium iron phosphate and the current collector to obtain separated lithium iron phosphate, and the separated lithium iron phosphate is transferred to a 100° C. forced air oven for drying for 24 hours, and then transferred to a 120° C. vacuum oven for drying for 48 hours to obtain the stripped lithium iron phosphate;

[0089] 0.6 mol of lithium hydroxide and 0.4 mol of ascorbic acid are prepared and dissolved in deionized water and N'N-dimethylamide in a volume ratio of 9:1, and the pH value of the mixed solution is adjusted to 8 to obtain a lithium supplement mixed solution; 50 g of lithium iron phosphate powder peeled off at 100 mesh and 50 g of lithium iron phosphate powder peeled off at 20 mesh are mixed and immersed in the lithium supplement mixed solution, and added to a spherical ink tank filled with zirconium oxide at the same time, and the ball milling speed is set to 1000 rpm, and the ball milling time is 2 hours to obtain a ball milling suspension, that is, a reaction mixture;

[0090] The reaction mixture was centrifuged at 8000 rpm and washed three times with deionizer. The mixture was dried in a 100°C blast oven for 12 h and then transferred to a 150°C vacuum oven for 48 h to obtain a gray powder, which was the regenerated lithium iron phosphate material. The elemental composition and content of the lithium iron phosphate were weighed and determined.

[0091] The preparation process of the regenerated lithium iron phosphate positive electrode material in the above-mentioned embodiments 2 to 9 is obtained, and the content of each element in the regenerated lithium iron phosphate prepared in the embodiments 2 to 9 is tested, and the relevant test results are shown in Table 1; and the recovery rate of the stripped lithium iron phosphate stripped out in each embodiment is tested, and the recovery rate of the stripped lithium iron phosphate stripped out with deionized water is calculated using the following formula:

[0092]

[0093] Among them, M S Indicates the mass of the stripped lithium iron phosphate; M P Indicates the quality of lithium iron phosphate positive electrode sheet pretreated by deionized water stripping; M Al represents the mass of the current collector aluminum foil stripped off by deionized water; R represents the recovery rate.

[0094] Table 1 Test results of various parameters in this embodiment

[0095]

[0096]

[0097] Combining the data in Table 1 and Figure 2 From the analysis, it can be seen from the recovery rate test data of the stripped lithium iron phosphate stripped in the method of this embodiment that, by calculating the recovery rate of the stripped lithium iron phosphate, by adopting the stripping conditions in this embodiment, the recovery rate of the stripped lithium iron phosphate can be made above 80% at different temperatures; and the contents of lithium, iron, phosphorus and carbon in the regenerated lithium iron phosphate obtained by adopting the regeneration and lithium replenishment method in this embodiment are improved compared with the contents in the waste lithium iron phosphate before treatment, which further proves the treatment effect of this scheme.

[0098] Further, the lithium supplementation mixed solution in Examples 2 to 9 was ground while maintaining a sealed state. After grinding for a first preset time, the particle size ratio test data in the reaction mixture was obtained as shown in Table 2. At the same time, the particle size distribution obtained after the lithium iron phosphate material was regenerated by wet grinding in Example 2, Example 4, Example 6 and Example 8 was as shown in Table 2. Figure 3As shown, as confirmed by the particle size distribution diagram shown, it is proved that the wet ball milling lithium repair process can ensure the uniformity of the particle size of the material after grinding regardless of whether the initial shape of the retired lithium iron phosphate is flake or powder.

[0099] Table 2 Test results of particle size ratio of lithium supplement mixed solution after grinding in each embodiment

[0100]

[0101] It can be seen from the data in Table 2 that although there are differences in the raw materials ground and the solvents used in the present application, the grinding process in this embodiment maintains uniformity in the particle size of each material in the mixed liquid after grinding, further proving that the positive electrode material of the waste lithium iron phosphate battery undergoes a wet grinding process in which the particles are refined and homogenized, and that each reactant is subjected to the grinding process, thereby enhancing the possibility of sufficient contact between the position to be supplemented and the lithium salt material, so as to form a supplement for the missing lithium element in the retired lithium iron phosphate, thereby improving the electrochemical properties of the prepared regenerated lithium iron phosphate.

[0102] Furthermore, XRD tests were performed on the retired undischarged lithium iron phosphate, the retired discharged lithium iron phosphate and the regenerated lithium iron phosphate material obtained by lithium supplementation and repair in this embodiment in Example 2, Example 4, Example 6 and Example 8. Figure 4 As shown, it is proved that wet grinding lithium repair will not add new impurity phases, and the prepared regenerated lithium iron phosphate meets the LiFePO4@C composite positive electrode material specified in JCPDS:77-0179.

[0103] Embodiment 10

[0104] Corresponding to the above embodiment, the present application provides a positive electrode plate, which is prepared by the method of wet grinding and regenerating lithium iron phosphate positive electrode material as described above.

[0105] Embodiment 11

[0106] Corresponding to the above embodiments, the present application provides a battery, which includes the positive electrode plate as described above, or the positive electrode plate in the battery is prepared by the method of wet grinding and regenerating lithium iron phosphate positive electrode material as described above.

[0107] In this embodiment, the regenerated lithium iron phosphate material prepared in Example 2 is used to assemble a lithium-ion battery, and the electrochemical performance test is carried out. The lithium-ion battery includes a positive electrode, a negative electrode and an electrolyte, and the lithium-ion battery includes but is not limited to a cylindrical battery, a square battery, a button battery and a sheet battery. The positive electrode, the negative electrode and the electrolyte of the lithium-ion battery are conventional structures in the art, wherein the positive electrode sheet includes a positive electrode material layer and a current collector, and the positive electrode material layer includes an active substance, a conductive agent and an adhesive, wherein the active substance is a regenerated lithium iron phosphate material, the conductive agent is conductive carbon black, and the adhesive is polyvinylidene fluoride, and the mass ratio of each is 8:1:1.

[0108] Further, the rate test and charge-discharge performance test of the prepared regenerated lithium iron phosphate material in the above-mentioned Examples 2 to 9 were carried out in the capacitor, and the test results obtained are shown in Table 3. At the same time, the rate test results of the regenerated lithium iron phosphate material obtained in Examples 2, 4, 6 and 8 in the supercapacitor (such as Figure 5 a) and charge and discharge curves (such as Figure 5 b), it can be seen that the charge / discharge platform exhibits reversibility during battery operation.

[0109] Table 3 Rate test and charge-discharge performance test results of each group of examples

[0110]

[0111] Combined with the test data in Table 3, it can be seen that the various battery performances of the regenerated lithium iron phosphate prepared by the method in this scheme are improved compared with the performance of the waste lithium iron phosphate material before treatment, which further verifies that the grinding and liquid phase repair operations adopted in this scheme enhance the possibility of sufficient contact between the position to be supplemented and the lithium salt material, so that the freely moving lithium ions can quickly find and fill the lithium vacancies in the positive electrode material, so that the lithium ions can more fully contact the supplement sites, thereby improving the supplement effect of the lithium-deficient sites.

[0112] The cycle stability of the lithium-ion battery prepared by the regenerated lithium iron phosphate material obtained in the scheme of this embodiment between 2.5 and 4.3 V at a constant (1C) current was also investigated. Figure 6 The cycle performance diagram of the wet ball milling lithium supplementation for repairing retired lithium iron phosphate in the supercapacitor of Example 2 is shown. After 150 cycles, the discharge specific capacity of 132.38 mAh / g is still maintained, and the capacity retention rate is nearly 91.23%, which proves the stable electrochemical performance of the repaired and regenerated lithium iron phosphate.

[0113] In this embodiment, the retired lithium iron phosphate is replenished and repaired by wet grinding, which can refine the material to be repaired into smaller particles by grinding to improve its surface reaction activity, and is conducive to efficient lithium replenishment and repair; compared with traditional dry ball milling, the wet ball milling lithium replenishment method in this embodiment can refine the particles more evenly, improve the mixing uniformity of the position to be replenished with lithium ions and the concentration of particle size distribution, so as to facilitate closer contact of the reaction materials, ensure that the subsequent lithium replenishment reaction is more fully carried out, so as to improve the electrochemical performance of the repaired regenerated lithium iron phosphate material. In addition, in this embodiment, by processing in a mild liquid phase environment, the production efficiency is improved, the production cost is reduced, and the economic benefit is improved; at the same time, the repaired lithium iron phosphate positive electrode material can be used again in battery production, reducing the dependence on new materials and further reducing production costs.

[0114] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present application.

[0115] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for wet grinding and regenerating lithium iron phosphate positive electrode material, characterized in that: The method comprises: Pre-treating waste lithium iron phosphate materials to obtain pre-treated lithium iron phosphate positive electrode sheets; Immersing the pretreated lithium iron phosphate positive electrode sheet in a deionized liquid to obtain the stripped lithium iron phosphate; preparing a lithium replenishing solution, immersing the stripped lithium iron phosphate in the lithium replenishing solution to obtain a lithium replenishing mixed solution, and grinding the lithium replenishing mixed solution for a first preset time to obtain a reacted mixture; The solid in the reaction mixture is separated and dried to obtain the regenerated lithium iron phosphate material.

2. The method for wet grinding and regenerating lithium iron phosphate positive electrode material according to claim 1, characterized in that: The pretreated lithium iron phosphate positive electrode sheet is immersed in a deionized liquid to obtain the stripped lithium iron phosphate, specifically comprising: Immersing the pretreated lithium iron phosphate positive electrode sheet in deionized water and maintaining it for a second preset time to obtain separated lithium iron phosphate; The separated lithium iron phosphate is placed in a constant temperature device for drying to obtain the stripped lithium iron phosphate.

3. The method for wet grinding and regenerating lithium iron phosphate positive electrode material according to claim 2, characterized in that: The method further comprises: The temperature of the deionized liquid is set to 60-100° C., and the second preset time is 3-5 minutes; The drying temperature in the constant temperature device is 80-120° C., and the drying time in the constant temperature device is 24-48 hours.

4. The method for wet grinding and regenerating lithium iron phosphate positive electrode material according to any one of claims 1 to 3, characterized in that: The stripped lithium iron phosphate is in the form of flakes or particles, and the surface area of ​​the stripped lithium iron phosphate is in the range of 1.5 to 4 mm 2 The particle size of the granular lithium iron phosphate peeled off is 20 to 100 meshes.

5. The method for wet grinding and regenerating lithium iron phosphate positive electrode material according to any one of claims 1 to 3, characterized in that: A lithium replenishing solution is prepared, and the stripped lithium iron phosphate is immersed in the lithium replenishing solution to obtain a lithium replenishing mixed solution, and the lithium replenishing mixed solution is ground for a first preset time to obtain a reacted mixture, specifically comprising: Mixing a lithium salt, a reducing substance and a polar solvent in a preset ratio to form a mixed solution, and adjusting the pH value of the mixed solution to a preset pH value to obtain the lithium supplement solution; The stripped lithium iron phosphate is immersed in the lithium replenishing solution to obtain a lithium replenishing mixed solution, and the lithium replenishing mixed solution is ground while maintaining a sealed state, and a reacted mixture is obtained after grinding for a first preset time.

6. The method for wet grinding and regenerating lithium iron phosphate positive electrode material according to claim 5, characterized in that: The method further comprises: The preset pH value is 8 to 12; The lithium supplementation mixed solution is sealed and ground in a ball mill, the grinding speed is 500 to 1500 rpm, and the grinding time is 2 to 6 hours.

7. The method for wet grinding and regenerating lithium iron phosphate positive electrode material according to claim 5, characterized in that: The method further comprises: The lithium salt includes at least one or more of lithium chloride, lithium iodide, lithium phosphate, lithium carbonate, lithium hydroxide, lithium bromide, lithium nitrate, lithium sulfate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium acetate, lithium bis(oxalatoborate), lithium tetrafluoroborate or lithium acrylate; The reducing substance includes at least one or more of lithium aluminum hydride, sodium thiocyanate, sodium sulfide, ascorbic acid, citric acid, glucose, fructose, lactose, maltose, potassium tris(1-pyrazolyl)borohydride, sodium triacetoxyborohydride, sodium sulfite, ferrous chloride tetrahydrate or stannous chloride; The polar solvent includes at least one or more of ethanol, methanol, acetone, ethyl acetate, dimethyl sulfoxide, glycerol, acetonitrile, tetrahydrofuran, acetic acid, N,N-dimethylamide, pyridine, dimethylacetamide, dioxane, N-methylpyrrolidone or hexamethylammonium phosphate.

8. The method for wet grinding and regenerating lithium iron phosphate positive electrode material according to claim 5, characterized in that: The method further comprises: Using a centrifugal device to separate the solid in the reaction mixture, wherein the rotation speed of the centrifugal device is 8000-15000 rpm; Drying the solid in a forced air oven and then in a vacuum oven; The temperature of the blast oven for drying the solid is 80-100°C and the drying time is 8-12h; The temperature of the vacuum oven for drying the solid is 120-150° C., and the drying time is 24-48 hours.

9. A positive electrode sheet, characterized in that: The positive electrode plate is prepared by the method for wet grinding and regenerating lithium iron phosphate positive electrode material according to any one of claims 1 to 8.

10. A battery, characterized in that: The battery comprises the positive electrode sheet described in claim 9 or the positive electrode sheet in the battery is prepared by the method for wet grinding and regenerating lithium iron phosphate positive electrode material according to any one of claims 1 to 8.

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