Recovery method and application of lithium iron phosphate retired battery pole piece

Abstract

The invention relates to the technical field of secondary batteries, in particular to a recovery method and application of a lithium iron phosphate retired battery pole piece. The negative pole piece of the lithium iron phosphate retired battery is subjected to light degradation, a light degradation area is only distributed on one side of a tab side of the negative pole piece, and when the area of the light degradation area accounts for 30% or below of the total area of the negative pole piece, the health degree of the negative pole piece is judged to be 90%-100%; when the negative pole piece is seriously degraded, a seriously degraded region is simultaneously distributed on one side of the tab side and the opposite side of the tab side of the negative pole piece, and the area of the seriously degraded region accounts for 30%-70% of the total area of the negative pole piece, the health degree of the negative pole piece is judged to be 80%-90%; and when serious degradation occurs and the area of the serious degradation region accounts for 70%-100% of the total area of the negative pole piece, judging that the health degree of the negative pole piece is below 80%. According to the method, the failure degrees of the positive and negative pole pieces of the lithium iron phosphate retired battery can be accurately and efficiently classified.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a recovery method of lithium iron phosphate retired battery pole piece and application thereof. BACKGROUND

[0002] Lithium ion batteries, as a typical new energy secondary power source, exhibit excellent electrochemical characteristics such as high capacity, high energy density, high working voltage, and low self-discharge, and thus have been widely used in the fields of smart phones, notebook computers, electric vehicles, and energy storage power stations. Among them, the use and production of lithium iron phosphate batteries increase year by year due to their low cost, high safety, and long service life. By the end of 2025, the cumulative capacity of global lithium iron phosphate batteries may reach or even exceed 3TWh. As the service life approaches, the amount of retired batteries also increases year by year, and these retired and discarded batteries need to be recycled.

[0003] Currently, waste batteries are mainly recycled by hydrometallurgical process or direct regeneration method, but the direct regeneration method has high requirements for materials, and the performance of the positive pole piece after regeneration is poor, which does not meet the use standard. Therefore, accurately, simply and efficiently identifying the failure degree of lithium iron phosphate batteries, especially the positive pole piece, is crucial for direct regeneration.

[0004] A Chinese patent with publication number CN114865131A provides a repair method for retired lithium iron phosphate, including the following steps: measuring the voltage of the retired lithium iron phosphate battery; grouping the batteries according to the voltage, then disassembling the batteries according to the group, separating out the positive pole piece, and obtaining the positive pole powder; and repairing the positive pole powder of different groups respectively.

[0005] A Chinese patent with publication number CN118444186A introduces a rapid and accurate detection device for the health status of retired power batteries, which includes a battery type identification module, a comprehensive model construction module, a charge-discharge protocol generation module, a health status evaluation module, and a dynamic correction module. Among them, the battery type identification module automatically identifies the type of the connected battery; the comprehensive model construction module predicts the battery aging factor and its influence on the battery performance; the charge-discharge protocol generation module adjusts the charge-discharge rate and depth; the health status evaluation module evaluates the capacity, internal resistance, and electrochemical stability of the battery; and the dynamic correction module dynamically adjusts the comprehensive model and the rapid charge-discharge strategy. By integrating advanced data processing and machine learning technologies, the battery performance monitoring efficiency and accuracy are significantly improved, the operation process is simplified and the cost is reduced, and the continuous health management and optimized recycling and reuse of batteries are effectively promoted.

[0006] There are many reasons leading to different health states of the battery, and the failure degree of the positive and negative electrode sheets is not strictly corresponding to the health state of the battery, and there will be some deviation. Therefore, although the above patent can identify and classify the lithium iron phosphate batteries with different health states, the identification and classification of the specific failure degree of the positive and negative electrode sheets is not accurate, lacks effectiveness, is not simple and efficient, and also lacks recycling of the negative electrode sheets.

[0007] In order to maximize the resource utilization of lithium iron phosphate batteries and improve the recycling benefit, the positive and negative electrode sheets need to be accurately, simply and efficiently identified and classified, and reasonable utilization and treatment methods are given. Therefore, it is of great significance to provide an accurate, simple and efficient method for classifying the positive and negative electrode sheets of lithium iron phosphate batteries and recycling them according to different states of the positive and negative electrode sheets to maximize the utilization.

[0008] Therefore, the present application is proposed. SUMMARY

[0009] The first object of the present application is to provide a recycling method for lithium iron phosphate retired battery electrode sheets, which accurately and efficiently classifies the failure degree of the positive and negative electrode sheets of lithium iron phosphate retired batteries by a simple and easy-to-operate method, and can maximize the resource recycling of the discarded positive and negative electrode sheets. The problem of inaccurate identification and classification of the failure degree of the positive and negative electrode sheets in the prior art, lack of effectiveness, and inconvenience and inefficiency are solved.

[0010] The second object of the present application is to provide the application of the recycling method for lithium iron phosphate retired battery electrode sheets in the preparation of secondary batteries.

[0011] In order to achieve the above object of the present application, the following technical scheme is adopted: The present application first provides a recycling method for lithium iron phosphate retired battery electrode sheets, comprising the following steps: discharging and disassembling the lithium iron phosphate retired battery to obtain the positive electrode sheet and the negative electrode sheet; when the negative electrode sheet has light degradation of turning gray, turning black or turning blue, and the light degradation area is only distributed on one side of the tab side of the negative electrode sheet, and the area of the light degradation area accounts for less than 30% of the total area of the negative electrode sheet, it is determined that the health degree of the negative electrode sheet is 90% to 100%; when the negative electrode sheet has relatively serious degradation of turning blue, and the relatively serious degradation area is simultaneously distributed on one side of the tab side and the opposite side of the tab side of the negative electrode sheet, and the area of the relatively serious degradation area accounts for 30% to 70% of the total area of the negative electrode sheet, it is determined that the health degree of the negative electrode sheet is 80% to 90%; when the negative electrode sheet has serious degradation of turning blue or turning purple, and the area of the serious degradation area accounts for 70% to 100% of the total area of the negative electrode sheet, it is determined that the health degree of the negative electrode sheet is below 80%.

[0012] Further, the lithium iron phosphate retired battery is discharged to 0% SOC.

[0013] Further, when the health degree of the negative electrode sheet is determined to be 90% to 100% and the health degree of the negative electrode sheet is determined to be 80% to 90%, the positive electrode active material in the positive electrode sheet and the negative electrode active material in the negative electrode sheet are recovered by direct regeneration method, respectively; when the health degree of the negative electrode sheet is determined to be below 80%, the valuable components in the positive electrode sheet and the negative electrode sheet are recovered by hydrometallurgy process.

[0014] Further, when the health degree of the negative electrode sheet is determined to be 90% to 100%, the positive electrode active material in the positive electrode sheet is separated and a regenerated positive electrode material is formed by direct lithium supplement sintering method. Preferably, the direct lithium supplement sintering method comprises: determining the element content of the positive electrode active material, then adding a lithium source, mixing and sintering under an inert atmosphere; more preferably, the sintering is at 500°C to 800°C for 5h to 20h.

[0015] Further, when the health degree of the negative electrode sheet is determined to be 90% to 100%, the negative electrode active material in the negative electrode sheet is separated and a regenerated negative electrode material is formed by acid leaching roasting method. Preferably, the acid leaching roasting method comprises: mixing the negative electrode active material with an acid solution and leaching, then washing with water and drying, and then roasting in an inert atmosphere; more preferably, the acid solution comprises a sulfuric acid solution and / or a hydrochloric acid solution; more preferably, the molar concentration of the acid solution is 1mol / L to 3mol / L; more preferably, the leaching time is 1h to 4h; more preferably, the roasting temperature is above 1200°C, and the roasting time is 2h to 10h.

[0016] Further, when the health degree of the negative electrode sheet is determined to be 80% to 90%, the positive electrode active material in the positive electrode sheet is separated and a regenerated positive electrode material is formed by promoting regeneration method. Preferably, the promoting regeneration method comprises: determining the element content of the positive electrode active material, then adding a lithium source and a reducing agent, mixing and sintering under an inert atmosphere; more preferably, the reducing agent comprises sucrose and / or glucose; more preferably, the mass of the reducing agent is 1% to 2% of the mass of the positive electrode active material; more preferably, the sintering is at 500°C to 800°C for 5h to 20h.

[0017] Further, when the health degree of the negative electrode sheet is determined to be 80% to 90%, the negative electrode active material in the negative electrode sheet is separated and a regenerated negative electrode material is formed by an acid leaching high-temperature calcination method. Preferably, the acid leaching high-temperature calcination method comprises: mixing the negative electrode active material with an acid solution and acid leaching, then washing with water and drying, and calcining in an inert atmosphere; more preferably, the acid solution comprises a sulfuric acid solution and / or a hydrochloric acid solution; more preferably, the molar concentration of the acid solution is 1 mol / L to 3 mol / L; more preferably, the acid leaching time is 1 h to 4 h; and more preferably, the calcination temperature is 2000 DEG C or higher, and the calcination time is 2 h to 10 h.

[0018] Further, when the health degree of the negative electrode sheet is determined to be 80% to 90%, the negative electrode active material in the negative electrode sheet is separated and a regenerated negative electrode material is formed by an acid leaching high-temperature calcination method. Preferably, the acid leaching high-temperature calcination method comprises: mixing the negative electrode active material with an acid solution and acid leaching, then washing with water and drying, and calcining in an inert atmosphere; more preferably, the acid solution comprises a sulfuric acid solution and / or a hydrochloric acid solution; more preferably, the molar concentration of the acid solution is 1 mol / L to 3 mol / L; more preferably, the acid leaching time is 1 h to 4 h; and more preferably, the calcination temperature is 2000 DEG C or higher, and the calcination time is 2 h to 10 h.

[0019] Further, when the health degree of the negative electrode sheet is determined to be 80% to 90%, the negative electrode active material in the negative electrode sheet is separated and a regenerated negative electrode material is formed by an acid leaching high-temperature calcination method. Preferably, the acid leaching high-temperature calcination method comprises: mixing the negative electrode active material with an acid solution and acid leaching, then washing with water and drying, and calcining in an inert atmosphere; more preferably, the acid solution comprises a sulfuric acid solution and / or a hydrochloric acid solution; more preferably, the molar concentration of the acid solution is 1 mol / L to 3 mol / L; more preferably, the acid leaching time is 1 h to 4 h; and more preferably, the calcination temperature is 2000 DEG C or higher, and the calcination time is 2 h to 10 h.

[0020] The application also provides application of the above-mentioned recovery method of the lithium iron phosphate retired battery electrode sheet in preparation of a secondary battery.

[0021] Compared with the prior art, the application has the following beneficial effects: (1) The lithium iron phosphate retired battery pole piece recycling method provided by the present application can accurately and efficiently classify the failure degree of the positive and negative pole pieces of the lithium iron phosphate retired battery through a simple and easy-to-operate method, and can maximize the recycling of waste positive and negative pole pieces. The problem of inaccurate identification and classification of the failure degree of the positive and negative pole pieces in the prior art is solved.

[0022] (2) The lithium iron phosphate retired battery pole piece recycling method provided by the present application further recycles and utilizes the positive and negative pole pieces according to their different health states, has higher economic benefits, produces less waste, and is more environmentally friendly. The problems of lack of recycling of negative pole pieces and recycling according to different states of positive and negative pole pieces in the prior art are solved. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the specific embodiments or the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0024] Figure 1 The schematic diagram of the negative pole piece occurring light deterioration provided by the present application is shown in the figure. Figure 2 The schematic diagram of the negative pole piece occurring light deterioration provided by the present application is shown in the figure. Figure 3 The schematic diagram of the negative pole piece occurring light deterioration provided by the present application is shown in the figure. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described clearly and completely in combination with the drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The specific conditions in the embodiments are not specified, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0026] If there is no special indication, in the present application, "first aspect", "second aspect" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implying the importance or quantity of the indicated technical features. Moreover, "first", "second" and the like only serve the purpose of non-exhaustive enumeration description, and should be understood as not constituting a closed limitation on the quantity.

[0027] If there is no special indication, the "includes" and "contains" mentioned in the present application represent open type, and can also be closed type. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0028] In a first aspect, the present application provides a recycling method of lithium iron phosphate retired battery pole piece (including negative pole piece and positive pole piece), comprising the following steps: Discharge the lithium iron phosphate retired battery and obtain the positive pole piece and the negative pole piece respectively by fine disassembling.

[0029] When the negative pole piece has light degradation of turning gray, turning black or bluing (referring to the visual effect with blue or blue tendency in color, showing a blue tone), and the light degradation area is only distributed on one side of the tab side of the negative pole piece (see Figure 1 When the area of the light degradation area accounts for less than 30% (for example, 30%, 25%, 20%, 15%, 10%, 5%, 3% or 1%) of the total area of the negative pole piece, it is determined that the health degree of the negative pole piece is 90%-100%.

[0030] When the negative pole piece has serious degradation of turning blue, and the serious degradation area is distributed on one side of the tab side and the opposite side of the tab side of the negative pole piece (see Figure 2 When the area of the serious degradation area accounts for 30%-70% (for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or 70%) of the total area of the negative pole piece, it is determined that the health degree of the negative pole piece is 80%-90%.

[0031] When the negative pole piece has serious degradation of turning blue or bluish purple, and the serious degradation area is distributed on the entire surface of the negative pole piece (see Figure 3 When the area of the serious degradation area accounts for 70%-100% (for example, 70%, 75%, 80%, 85%, 90%, 95% or 100%) of the total area of the negative pole piece, it is determined that the health degree of the negative pole piece is below 80%.

[0032] The application can accurately and efficiently classify the failure degree of the positive and negative electrode sheets of the retired lithium iron phosphate battery through a simple and easy-to-operate method, and can maximize the recycling of the discarded positive and negative electrode sheets.

[0033] Specifically, during the use of the battery cell, due to the Overhang of the electrode sheet (the "reserved area" or "rim", the industry describes the Overhang of the negative electrode sheet as the part beyond the positive electrode sheet in the length and width directions, which can be simply understood as the excess amount of the negative electrode covering the positive electrode), after the lithium ions in the positive electrode are inserted into the negative electrode, residual lithium accumulates at the edge position and cannot be removed, resulting in the first appearance of inactive lithium at the edge position of the negative electrode; and during the use of the battery cell, especially the square cell, the tab side is generally upward, and the wettability of the electrolyte to the edge electrode sheet on the tab side is worse than that on the bottom side due to the influence of gravity. Therefore, the edge electrode sheet on the tab side accumulates more inactive lithium faster, and the first deterioration phenomenon occurs; the edge electrode sheet on the bottom side (i.e. the opposite side of the tab side) has good electrolyte wettability, and lithium ions can be transferred through the electrolyte, so the accumulation of inactive lithium is slower and less than that on the tab side, and the deterioration phenomenon occurs slower and the deterioration degree is shallower. Therefore, as the state of health of the battery cell gradually decreases during use, the edge electrode sheet on the tab side first shows visible deterioration such as gray, black, blue, and purple, and the deterioration degree gradually deepens and the deterioration area gradually expands; after breaking through a certain state of health (90% SOH), the edge electrode sheet on the bottom side also shows the above-mentioned deterioration phenomenon; as the deterioration areas on both sides of the edge electrode sheet continuously expand towards the center, and finally cover the entire electrode sheet, the state of health of the electrode sheet decreases to below 80%, which cannot meet the normal use, and needs to be retired and scrapped.

[0034] In summary, according to the deterioration degree of the negative electrode sheet, the distribution position of the deterioration area, and the ratio of the area of the deterioration area to the area of the entire electrode sheet, the failure state of the positive and negative electrode sheets can be classified, and the specific method of recycling can be determined according to the different failure states of the positive and negative electrode sheets.

[0035] In some specific embodiments, the lithium iron phosphate retired battery is discharged to 0% SOC. Discharging the failed retired battery to 0% SOC can make the lithium ions as much as possible to be inserted into the positive active material, so as to reduce the influence on the subsequent classification of the failure degree of the positive and negative electrode sheets.

[0036] In some specific embodiments, when the health degree of the negative electrode sheet is determined to be 90% to 100% and the health degree of the negative electrode sheet is determined to be 80% to 90%, the positive active material in the positive electrode sheet and the negative active material in the negative electrode sheet are recovered by direct regeneration methods, respectively. When the health degree of the negative electrode sheet is determined to be less than 80%, the valuable components in the positive electrode sheet and the negative electrode sheet are recovered by hydrometallurgy process. The valuable components include, but are not limited to, valuable elements such as Li, Fe, P (such as LiFePO4, FePO4, Li2CO3), and graphite.

[0037] The present application recycles and utilizes the positive and negative electrode sheets in a suitable and high-value manner according to different health degrees of the positive and negative electrode sheets, has higher economic benefits, produces less waste, and is more green and environmentally friendly.

[0038] In some specific embodiments, when the health degree of the negative electrode sheet is determined to be 90% to 100%, the positive active material in the positive electrode sheet is separated and a regenerated positive electrode material is formed by a direct lithium supplement resintering method. Preferably, the direct lithium supplement resintering method comprises: determining the element content of the positive active material, then adding a lithium source, mixing, and sintering under an inert atmosphere; more preferably, the sintering is at 500°C to 800°C (for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, or 800°C) for 5h to 20h (for example, 5h, 6h, 7h, 8h, 9h, 10h, 12h, 15h, 18h, or 20h).

[0039] In some specific embodiments, when the health degree of the negative electrode sheet is determined to be 90% to 100%, the negative active material in the negative electrode sheet is separated and a regenerated negative electrode material is formed by an acid leaching roasting method. Preferably, the acid leaching roasting method comprises: mixing the negative active material with an acid solution and leaching, then washing with water and drying, and roasting in an inert atmosphere; more preferably, the acid solution comprises a sulfuric acid solution and / or a hydrochloric acid solution; more preferably, the molar concentration of the acid solution is 1 mol / L to 3 mol / L (for example, 1.5 mol / L, 2 mol / L, or 2.5 mol / L); more preferably, the acid leaching time is 1h to 4h (for example, 2h, 2.5h, or 3h); more preferably, the roasting temperature is above 1200°C, and the roasting time is 2h to 10h (for example, 3h, 4h, 5h, 6h, 7h, 8h, or 9h).

[0040] It can be understood that when the normally brown negative electrode sheet is slightly deteriorated in terms of graying, blackening, and blueness, the slightly deteriorated area is only distributed on one side of the tab, and the ratio of the area of the slightly deteriorated area to the area of the whole negative electrode sheet is 0 to 30% (slight deterioration degree, for example, 0% to 10%, 0% to 20%, 0% to 30%, 10% to 20%, or 10% to 30%). Figure 1The results show that the negative electrode sheet has a low degree of failure, a good state, and a low content of non-active lithium, and the health degree of the negative electrode sheet is 90% to 100%. The positive electrode active material and the negative electrode active material can be separated from the positive electrode sheet and the negative electrode sheet, respectively. Then, the element content of the positive electrode active material is determined by the ICP method, the Li / Fe molar ratio is calculated, lithium source such as lithium hydroxide or lithium carbonate is added to supplement the Li / Fe molar ratio to 1.10, and the mixture is uniformly mixed and then put into an atmosphere furnace to sinter under nitrogen. At the same time, the separated negative electrode active material can be first soaked in 1 to 3 mol / L dilute sulfuric acid or dilute hydrochloric acid for 1 to 4 hours for pickling, then washed with deionized water until neutral, and then vacuum dried at 100 to 120°C for 12 to 24 hours, and finally roasted at a temperature above 1200°C in an atmosphere furnace under inert gas. In this way, the material structure can be restored by direct regeneration to obtain regenerated materials (regenerated positive electrode material and regenerated negative electrode material), and the regenerated performance can reach a level close to that of commercial materials.

[0041] In some specific embodiments, when the health degree of the negative electrode sheet is determined to be 80% to 90%, the positive electrode active material in the positive electrode sheet is separated and a regenerated positive electrode material is formed by a regeneration-promoting method. Preferably, the regeneration-promoting method comprises: determining the element content of the positive electrode active material, then adding lithium source and reducing agent, and sintering under inert atmosphere after mixing. More preferably, the reducing agent comprises sucrose and / or glucose. More preferably, the mass of the reducing agent is 1% to 2% (for example, 1.2%, 1.5%, or 1.8%) of the mass of the positive electrode active material. More preferably, the sintering is: holding at 500°C to 800°C (for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, or 800°C) for 5h to 20h (for example, 5h, 6h, 7h, 8h, 9h, 10h, 12h, 15h, 18h, or 20h).

[0042] In some specific embodiments, when the health degree of the negative electrode sheet is determined to be 80% to 90%, the negative electrode active material in the negative electrode sheet is separated and a regenerated negative electrode material is formed by an acid immersion high-temperature calcination method. Preferably, the acid immersion high-temperature calcination method comprises: mixing the negative electrode active material with an acid solution and immersing in acid, then washing with water and drying, and then calcining in an inert atmosphere. More preferably, the acid solution comprises a sulfuric acid solution and / or a hydrochloric acid solution. More preferably, the molar concentration of the acid solution is 1 mol / L to 3 mol / L (for example, 1.5 mol / L, 2 mol / L, or 2.5 mol / L). More preferably, the acid immersion time is 1h to 4h (for example, 2h or 3h). More preferably, the calcination temperature is above 2000°C, and the calcination time is 2h to 10h (for example, 3h, 4h, 5h, 6h, 7h, 8h, or 9h).

[0043] It can be understood that when the normal brown negative electrode sheet is seriously deteriorated to a blue degree, the seriously deteriorated area is distributed on both the tab side and the other side (the bottom side, i.e., the opposite side of the tab side), and the proportion of the area of the seriously deteriorated area to the area of the whole negative electrode sheet is 30% to 70% (a serious deterioration degree, for example Figure 2 As shown, it indicates that the negative electrode sheet has a high failure degree, a poor state, and a high content of non-active lithium, and the health degree of the negative electrode sheet is between 80% and 90%. The positive and negative active materials can also be recovered by a direct regeneration method. However, the direct regeneration process of the positive active material needs to add a carbon source reducing agent (such as sucrose and glucose) to promote regeneration while adding a lithium source. The negative active material also needs to be deepened to adjust the process, such as increasing the high-temperature calcination temperature to above 2000°C, so as to obtain a regenerated material (regenerated positive active material and regenerated negative active material) with a performance close to that of a commercial material.

[0044] In some specific embodiments, when it is determined that the health degree of the negative electrode sheet is below 80%, the positive active material in the positive electrode sheet is separated and FePO4 and Li2CO3 are recovered by a hydrometallurgical method. Preferably, the method for recovering FePO4 and Li2CO3 by the hydrometallurgical method comprises: mixing the positive active material, an acid solution, and an oxidizing agent and heating leaching to obtain a leaching solution, then adding an alkali solution to the leaching solution, and after solid-liquid separation, obtaining FePO4 precipitate and a lithium-rich mother liquor, respectively; and then adding a sodium carbonate solution (preferably a saturated sodium carbonate solution) to the lithium-rich mother liquor to precipitate lithium to obtain Li2CO3. More preferably, the acid solution comprises a dilute sulfuric acid solution and / or a dilute hydrochloric acid solution. More preferably, the oxidizing agent comprises hydrogen peroxide. More preferably, the alkali solution comprises a NaOH solution and / or a Ca(OH)2 solution. More preferably, the pH of the mixed system after adding the alkali solution is 3.5 to 4.5 (for example, 3.6, 3.8, 4.0, 4.2, or 4.4).

[0045] In some specific embodiments, when it is determined that the health degree of the negative electrode sheet is below 80%, the negative active material in the negative electrode sheet is separated and graphite and Li2CO3 are recovered by a hydrometallurgical method. Preferably, the method for recovering graphite and Li2CO3 by the hydrometallurgical method comprises: mixing the negative active material and an acid solution and heating leaching, and after solid-liquid separation, obtaining graphite and a leaching solution, respectively, adding a sodium carbonate solution (preferably a saturated sodium carbonate solution) to the leaching solution to precipitate lithium to obtain Li2CO3. More preferably, the acid solution comprises a dilute sulfuric acid solution and / or a dilute hydrochloric acid solution.

[0046] It can be understood that when the normal brown negative pole piece is seriously deteriorated to a blue or purple degree, the seriously deteriorated area is widely distributed on the surface of the entire negative pole piece, and the proportion of the area of the seriously deteriorated area to the area of the entire negative pole piece is 70% to 100% (a serious deterioration degree, for example Figure 3 As shown in the table, when the normal brown negative pole piece is seriously deteriorated to a blue or purple degree, the seriously deteriorated area is widely distributed on the surface of the entire negative pole piece, and the proportion of the area of the seriously deteriorated area to the area of the entire negative pole piece is 70% to 100% (a serious deterioration degree, for example

[0047] In the second aspect, the application provides an application of the recovery method of the lithium iron phosphate retired battery pole piece in the preparation of a secondary battery.

[0048] The recovery method of the lithium iron phosphate retired battery pole piece provided by the application can accurately, simply and efficiently recover the positive pole piece and the negative pole piece, and the recovered positive active material and negative active material can be reused, for example, the regenerated positive material, the regenerated negative material, FePO4 and Li2CO3 can be used to produce lithium iron phosphate batteries or other lithium ion batteries, and the slightly inferior regenerated graphite can be used to produce lubricants, conductive additives and the like, thereby improving the economic added value and having a wide application prospect.

[0049] Although the application has been described and illustrated with specific embodiments, it should be understood that the foregoing specific embodiments are merely illustrative of the technical solutions of the application, and are not intended to limit the application; those skilled in the art should understand that the technical solutions recorded in the foregoing specific embodiments can be modified, or some or all of the technical features can be replaced equivalently, without departing from the spirit and scope of the application; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application; therefore, this means that all these replacements and modifications within the scope of the application are included in the appended claims.

Claims

1. A method for recycling retired lithium iron phosphate battery electrodes, characterized in that, Includes the following steps: Discharge and disassemble retired lithium iron phosphate batteries to obtain positive and negative electrode plates; When the negative electrode sheet undergoes slight degradation, such as turning gray, black, or bluish, and the slightly degraded area is only distributed on one side of the tab side of the negative electrode sheet, and the area of ​​the slightly degraded area accounts for less than 30% of the total area of ​​the negative electrode sheet, the health of the negative electrode sheet is determined to be 90%~100%. When the negative electrode sheet undergoes severe degradation, turning blue, and the severely degraded area is simultaneously distributed on one side of the tab side and the opposite side of the tab side of the negative electrode sheet, and the area of ​​the severely degraded area accounts for 30% to 70% of the total area of ​​the negative electrode sheet, the health of the negative electrode sheet is determined to be 80% to 90%. When the negative electrode sheet undergoes severe deterioration, turning blue or purple, and the area of ​​the severely deteriorated region accounts for 70% to 100% of the total area of ​​the negative electrode sheet, the health of the negative electrode sheet is determined to be below 80%.

2. The method for recycling retired lithium iron phosphate battery electrodes according to claim 1, characterized in that, The retired lithium iron phosphate battery was discharged to 0% SOC.

3. The method for recycling retired lithium iron phosphate battery electrodes according to claim 1, characterized in that, When the health of the negative electrode sheet is determined to be 90%~100% and when the health of the negative electrode sheet is determined to be 80%~90%, the positive active material in the positive electrode sheet and the negative active material in the negative electrode sheet are restored by direct regeneration. When the health of the negative electrode is determined to be below 80%, the valuable components in the positive and negative electrodes are recovered by a hydrometallurgical process.

4. The method for recycling retired lithium iron phosphate battery electrodes according to claim 3, characterized in that, When the health of the negative electrode sheet is determined to be 90%~100%, the positive electrode active material in the positive electrode sheet is separated and a regenerated positive electrode material is formed by direct lithium replenishment and re-sintering. Preferably, the direct lithium replenishment and re-sintering method includes: determining the elemental content of the positive electrode active material, then adding a lithium source, mixing, and sintering under an inert atmosphere; more preferably, the sintering is performed at 500℃~800℃ for 5h~20h.

5. The method for recycling retired lithium iron phosphate battery electrodes according to claim 3, characterized in that, When the health of the negative electrode sheet is determined to be 90%~100%, the negative electrode active material in the negative electrode sheet is separated and a regenerated negative electrode material is formed by acid leaching and calcination. Preferably, the acid leaching and calcination method includes: mixing the negative electrode active material with an acid solution and leaching it with acid, then washing it with water and drying it, and then calcining it in an inert atmosphere; more preferably, the acid solution includes a sulfuric acid solution and / or a hydrochloric acid solution; more preferably, the molar concentration of the acid solution is 1 mol / L to 3 mol / L; more preferably, the acid leaching time is 1 h to 4 h; more preferably, the calcination temperature is above 1200℃, and the calcination time is 2 h to 10 h.

6. The method for recycling retired lithium iron phosphate battery electrodes according to claim 3, characterized in that, When the health of the negative electrode sheet is determined to be 80%~90%, the positive electrode active material in the positive electrode sheet is separated and a regenerated positive electrode material is formed by promoting regeneration. Preferably, the method for promoting regeneration includes: determining the elemental content of the positive electrode active material, then adding a lithium source and a reducing agent, mixing and sintering under an inert atmosphere; more preferably, the reducing agent includes sucrose and / or glucose; more preferably, the mass of the reducing agent is 1% to 2% of the mass of the positive electrode active material; more preferably, the sintering is performed at 500℃ to 800℃ for 5h to 20h.

7. The method for recycling retired lithium iron phosphate battery electrodes according to claim 3, characterized in that, When the health of the negative electrode sheet is determined to be 80%~90%, the negative electrode active material in the negative electrode sheet is separated and a regenerated negative electrode material is formed by acid leaching and high-temperature calcination. Preferably, the acid leaching and high-temperature calcination method includes: mixing the negative electrode active material with an acid solution and leaching it with acid, then washing it with water and drying it, and then calcining it in an inert atmosphere; more preferably, the acid solution includes a sulfuric acid solution and / or a hydrochloric acid solution; more preferably, the molar concentration of the acid solution is 1 mol / L to 3 mol / L; more preferably, the acid leaching time is 1 h to 4 h; more preferably, the calcination temperature is above 2000℃, and the calcination time is 2 h to 10 h.

8. The method for recycling retired lithium iron phosphate battery electrodes according to claim 3, characterized in that, When the health of the negative electrode sheet is determined to be below 80%, the positive electrode active material in the positive electrode sheet is separated and FePO4 and Li2CO3 are recovered by hydrometallurgical method. Preferably, the method for recovering FePO4 and Li2CO3 by hydrometallurgical means includes: mixing the positive electrode active material, acid solution and oxidant and heating to leach to obtain a leachate; then adding an alkaline solution to the leachate; after solid-liquid separation, obtaining FePO4 precipitate and lithium-rich mother liquor respectively; then adding sodium carbonate solution to the lithium-rich mother liquor to precipitate lithium to obtain Li2CO3; more preferably, the acid solution includes dilute sulfuric acid solution and / or dilute hydrochloric acid solution; more preferably, the oxidant includes hydrogen peroxide; more preferably, the alkaline solution includes NaOH solution and / or Ca(OH)2 solution; more preferably, the alkaline solution is added until the pH of the mixed system is 3.5~4.

5.

9. The method for recycling retired lithium iron phosphate battery electrodes according to claim 3, characterized in that, When the health of the negative electrode sheet is determined to be below 80%, the negative electrode active material in the negative electrode sheet is separated and graphite and Li2CO3 are recovered by hydrometallurgical method. Preferably, the method for recovering graphite and Li2CO3 by hydrometallurgical means includes: mixing the negative electrode active material and an acid solution and heating to leach, separating the solid and liquid to obtain graphite and leachate respectively, adding sodium carbonate solution to the leachate to precipitate lithium, and obtaining Li2CO3; more preferably, the acid solution includes dilute sulfuric acid solution and / or dilute hydrochloric acid solution.

10. The application of the method for recycling retired lithium iron phosphate battery electrodes as described in any one of claims 1 to 9 in the preparation of secondary batteries.

Images