A method for recycling and regenerating waste lithium iron phosphate based on redox targeted flow battery
Through the method based on redox targeted flow batteries, the problems of high energy consumption and secondary pollution in the recycling of waste lithium iron phosphate batteries are solved, and low-cost, pollution-free regeneration and simplified processes are achieved, suitable for large-scale production and maintaining Battery performance.
Patent Information
- Application Number
- CN202311275906.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-28
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2043-09-28
AI Technical Summary
The existing waste lithium iron phosphate battery recycling methods have problems such as high energy consumption, structural damage and secondary pollution. The hydrometallurgy process is cumbersome and costly, making it difficult to achieve simple and efficient large-scale production.
The recycling and regeneration method based on redox targeted flow batteries is adopted. By disassembly, drying, calculating the amount of lithium ion missing, constructing zinc-iron flow batteries for constant current discharge, repairing the regenerated lithium iron phosphate positive electrode material without calcination, etc. Sub-process, directly used for battery assembly.
It realizes low-cost, pollution-free lithium iron phosphate positive electrode material regeneration, reduces energy consumption and pollution, simplifies the process flow, is suitable for large-scale industrial applications, and maintains the discharge capacity and cycle life of the battery.
Smart Images
Figure CN117393874B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of recycling waste lithium-ion batteries, and in particular, relates to a method for recycling and regenerating waste lithium iron phosphate based on a redox targeted liquid flow battery. Background Art
[0002] Lithium-ion batteries (LIBs) are one of the most impressive and successful energy storage systems, playing an important role in our daily lives. As the main cathode of lithium-ion batteries, lithium iron phosphate (LFP) has a large market share. Due to the strong Fe-O and PO bond energy, LFP can maintain a stable olivine crystal structure, thus having good high-temperature stability. In addition, the core elements of LFP, Fe and P, are cost-effective and widely distributed around the world as natural resources. Therefore, lithium iron phosphate-based lithium-ion batteries are widely used in electric vehicles (EVs) and energy storage systems (ESS). As the scale of application expands, the future must face the large-scale abandonment of lithium iron phosphate batteries, and it is certain that their recycling becomes very urgent and necessary.
[0003] So far, many recycling processes have focused on valuable elements and cathode materials, in particular, the recovery of spent lithium iron phosphate cathode materials. Two recycling pathways are generally adopted: pyrometallurgy and hydrometallurgical processes. Both strategies have their own advantages and disadvantages. Pyrometallurgy directly promotes the physicochemical transformation and further regeneration of LFP cathode materials. For example, the spent LFP material is mixed with Li2CO3 by ball milling and then dried at high temperature. Although effective pyrometallurgical technology can achieve the purpose of recycling, the process requires a lot of energy consumption. In addition, the high temperature required for the process may cause structural damage and degradation of electrochemical performance, thereby hindering the sustainable development of spent lithium iron phosphate cathode materials. Therefore, pyrometallurgy cannot be regarded as a sustainable recycling method in the industry. As for hydrometallurgy, most lithium extraction methods are based on oxidative leaching, including acid leaching, alkaline leaching and bioleaching. The remaining elements are recovered from the leachate by different combinations of solvent extraction, chemical precipitation and electrochemical deposition. However, hydrometallurgical technology is always cumbersome because it involves pretreatment, resulting in increased chemical consumption and higher costs. Therefore, it is imperative to find a simple, efficient and suitable method for large-scale production. People also expect that the recycled materials can be used directly as positive electrode materials for batteries without complicated secondary processing. Summary of the invention
[0004] The present invention provides a low-cost, pollution-free, continuous and controllable lithium iron phosphate positive electrode material regeneration method, which aims to solve the problem of secondary pollution of recycled waste liquid in the existing reuse of waste lithium iron phosphate positive electrodes. The method of the present invention directly uses the recycled lithium iron phosphate as the positive electrode and matches it with the negative electrode to manufacture lithium iron phosphate batteries without any secondary treatment. The whole process will not generate secondary pollution, which fully meets the requirements of clean production and circular green economy.
[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:
[0006] The object of the present invention is to provide a method for recycling and regenerating waste lithium iron phosphate based on a redox targeted flow battery, which is specifically achieved through the following steps:
[0007] S1. Disassemble the waste lithium iron phosphate battery, separate the positive electrode, rinse and dry it;
[0008] S2. Calculate the missing amount, surface load and surface capacity of lithium ions in the waste LFP positive electrode sheet;
[0009] S3, construct a zinc-iron liquid flow battery, the liquid flow battery comprising a diaphragm, a positive electrode storage tank and a negative electrode storage tank, the positive electrode storage tank is filled with a positive electrode electrolyte, the negative electrode storage tank is filled with a negative electrode electrolyte, the positive electrode electrolyte contains [Fe(CN)6] 3- ;
[0010] S4. Then, the positive electrode sheet treated by S1 is placed in the positive electrode storage tank of the liquid flow battery, and the liquid flow battery is discharged at a constant current. After the discharge is completed, it is naturally cooled to room temperature to obtain a repaired and regenerated lithium iron phosphate positive electrode sheet.
[0011] It is further defined that in S1, the separated positive electrode sheet is rinsed with DMC solvent.
[0012] It is further defined that in S1, the drying is carried out in a vacuum oven at 70°C to 90°C for at least 1 hour.
[0013] It is further defined that in S2, the degree of lithium ion deficiency in the waste lithium iron phosphate electrode sheet is tested by ICP-MS, and the loading amount and surface capacity per unit area of the electrode sheet are measured by an analytical balance.
[0014] It is further defined that in S3, [Fe(CN)6] 3- The concentration is 0.01 M~0.7 M.
[0015] It is further defined that in S3, the positive electrode electrolyte also includes an auxiliary electrolyte.
[0016] It is further defined that the auxiliary electrolyte is LiCl, and the concentration of LiCl is 3 M.
[0017] It is further defined that in S3, the negative electrode electrolyte consists of ZnBr2, LiOH and deionized water.
[0018] Further defined, the concentration of ZnBr2 is 0.4 M and the concentration of LiOH is 3 M.
[0019] It is further defined that in S3, the steps of preparing the diaphragm are as follows:
[0020] (1) Mixing a polymer, carbon black and a solvent in a mass ratio of (0.05-1): (2-8): (100-1000) to obtain a solution;
[0021] (2) forming the solution on the surface of the ion exchange membrane by spraying, spin coating, rolling, brushing, scraping or interfacial polymerization, and then volatilizing the solvent to obtain the membrane;
[0022] The polymer is PVDF, PTFE or acrylic polyurethane; the carbon black is super carbon black, Ketjen black or ordinary carbon black; the solvent is one or more of water, isopropyl alcohol, ethanol, N-methylpyrrolidone, dimethyl sulfoxide and N,N-dimethylformamide.
[0023] Further, in S4, the constant current discharge time is 1h to 24h, the reaction temperature is 25℃ to 60℃, and the current density is controlled at 1mA / cm 2 ~100 mA / cm 2 , the voltage range is controlled at 0.01V~2V.
[0024] The present invention aims to provide a method for recycling and regenerating waste lithium iron phosphate based on redox targeted flow battery. The method utilizes [Fe(CN)6] 4- React with waste lithium iron phosphate positive electrode sheets to achieve the regeneration of waste lithium iron phosphate positive electrode sheets. Compared with other recycling and regeneration methods, this method can directly regenerate the recycled positive electrode materials and match them with the negative electrode for battery production without the need for secondary processes such as calcination, thereby reducing pollution and energy consumption. In addition, this method has continuous production capabilities, can improve recycling efficiency, and has strong economic driving force, is suitable for large-scale mass production, and can be directly used for industrial applications.
[0025] Another object of the present invention is to provide a lithium iron phosphate battery, that is, a lithium iron phosphate battery assembled from the positive electrode sheets obtained by the recycling and regeneration method. The discharge capacity and cycle life of the battery are almost equivalent to those of a battery assembled from a new lithium iron phosphate positive electrode. This proves that the recycling and regeneration method provided by the present invention can successfully repair waste lithium iron phosphate positive electrode materials.
[0026] Compared with the prior art, the present invention has the following beneficial effects:
[0027] Compared with the existing recycling and regeneration methods, the method of the present invention can directly regenerate waste lithium iron phosphate positive electrode materials and match them with the negative electrode for making batteries without the need for secondary processes such as calcination, thereby reducing pollution and energy consumption. In addition, the method is simple and fast, eliminating cumbersome steps such as mechanical methods, acid leaching or alkaline leaching, reducing costs and avoiding secondary pollution to the environment. In addition, the present invention has low requirements for equipment and is very suitable for industrial-scale lithium battery recycling and regeneration.
[0028] The present invention utilizes a targeted liquid flow battery to electrochemically replenish lithium for waste lithium iron phosphate materials, thereby compensating for lithium lost during multiple charge and discharge uses of the waste lithium iron phosphate materials, thereby repairing the electrochemical properties of the lithium iron phosphate positive electrode materials, which is different from the existing recycling and regeneration methods in conception.
[0029] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the attached drawings are only provided for reference and illustration and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 Schematic diagram of the waste lithium iron phosphate battery positive electrode material recovery and regeneration system of the present invention;
[0031] Figure 2 This is the XRD diagram of the repaired and regenerated lithium iron phosphate cathode material obtained by electrochemical lithium supplementation;
[0032] Figure 3 It is the charge and discharge curve of button cells made of repaired and regenerated lithium iron phosphate positive electrode materials and new lithium iron phosphate positive electrode materials at 1C current density;
[0033] Figure 4 This is the rate performance diagram of button batteries made of repaired and regenerated lithium iron phosphate positive electrode materials and new lithium iron phosphate positive electrode materials. DETAILED DESCRIPTION
[0034] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.
[0035] The following examples are provided to better understand the present invention, but the present invention is not limited to the contents described in the specific embodiments.
[0036] Example 1: The method for recycling and regenerating waste lithium iron phosphate based on redox targeted flow battery in this example is achieved by the following steps:
[0037] S1. After disassembling the waste lithium iron phosphate battery step by step, 1g of positive electrode sheet is separated; the positive electrode sheet is cleaned with DMC solvent to remove the residual electrolyte on the positive electrode sheet, and the positive electrode sheet with the residual electrolyte removed is placed in a vacuum oven at 80°C for drying.
[0038] S2. The degree of lithium ion deficiency in the waste lithium iron phosphate electrode was tested by ICP-MS, and the loading amount and surface capacity per unit area of the electrode were measured using an analytical balance.
[0039] For Zn / [Fe(CN)6] 3- -SLFP hybrid flow battery, the active area of the battery is 2.0 cm 2 × 2.0 cm 2 The cation exchange membrane is a dense cation exchange membrane coated with a carbon layer / hydrophobic layer, which is used to separate the positive electrode electrolyte and the negative electrode electrolyte. The electrochemically treated carbon felt is used as the electrode.
[0040] S3, constructing a zinc-iron liquid flow battery, wherein the liquid flow battery includes a separator, a positive electrode storage tank and a negative electrode storage tank (see Figure 1 ), the positive electrode tank contains positive electrode electrolyte, the negative electrode tank contains negative electrode electrolyte, and the positive electrode electrolyte contains [Fe(CN)6] 3 , - 11.5 ml 0.3 M [Fe(CN)6] 3- A neutral solution of 3 M LiCl supporting salt was used as the positive electrolyte, and 40 mL of an alkaline solution of 0.4 M ZnBr2 and 3 M LiOH supporting salt was used as the negative electrolyte.
[0041] S4, then place the positive electrode sheet treated in S1 into the positive electrode storage tank of the liquid flow battery, discharge the liquid flow battery at a constant current, and perform a constant current discharge test on a NEWARE battery tester with a voltage range of 0.01-2.0 V and a current density range of 20 mA / cm 2 The reaction temperature is 50°C, and after the discharge is completed, it is naturally cooled to room temperature to obtain a repaired and regenerated lithium iron phosphate positive electrode sheet (RLFP).
[0042] The carbon layer / hydrophobic layer coated dense cation exchange membrane is prepared according to the following steps: 4g of Ketjen black and 0.5g of PVDF are dissolved in 20.5g of NMP solvent to obtain a mixed solution with a mass concentration of 18%, the mixed solution is spin-coated on the ion exchange membrane Nafion117, the solvent is evaporated at a temperature of 50°C for 2h, and a carbon / hydrophobic layer functional composite membrane with a thickness of ~10μm is prepared as the diaphragm.
[0043] Recycled lithium iron phosphate sheets or new lithium iron phosphate sheets were used as the positive electrode, lithium sheets were used as the negative electrode, and the separator was a polypropylene film (Cellgard2400). An appropriate amount of electrolyte (1M LiPF6 dissolved in an organic solvent with a volume ratio of EC:DEC:DMC=1:1:1) was added. 2032 button cells were assembled in a glove box under argon protection, and the performance of the assembled full battery was tested.
[0044] The XRD pattern of the repaired and regenerated lithium iron phosphate cathode material obtained by electrochemical lithium replenishment is shown in Figure 2 shown by Figure 2 It can be seen that the diffraction peak of the repaired and regenerated lithium iron phosphate obtained by electrochemical lithium replenishment is consistent with the PDF standard card (JPCDS: 40-1499), which is consistent with the crystal structure of lithium iron phosphate.
[0045] The charge and discharge curves of button cells made of repaired and regenerated lithium iron phosphate positive electrode materials and new lithium iron phosphate positive electrode materials at 1C current density are shown in the figure. Figure 3 shown by Figure 3 It can be seen that the charge and discharge capacities of the repaired and regenerated lithium iron phosphate positive electrode material are 145.4mAh / g and 135.3mAh / g, respectively, which are equivalent to 140.5mAh / g and 140.3mAh / g of the new lithium iron phosphate positive electrode material.
[0046] The rate performance diagram of button cells made of repaired and recycled lithium iron phosphate positive electrode materials and new lithium iron phosphate positive electrode materials is shown in the figure Figure 4 shown by Figure 4 It can be seen that the discharge capacity of the repaired and regenerated lithium iron phosphate positive electrode material at 0.1C, 0.5C, 1C, 2C, 4C, 10C and 20C are 163.6mAh / g, 155.5mAh / g, 143.2mAh / g, 128.9mAh / g, 117.2mAh / g, 101.4mAh / g and 89.6mAh / g, respectively, which are equivalent to 163.2mAh / g, 155.2mAh / g, 142.4mAh / g, 128.8mAh / g, 122.3mAh / g, 112.4mAh / g and 95.7mAh / g of the new lithium iron phosphate positive electrode material.
Claims
1. A method for recycling and regenerating waste lithium iron phosphate based on redox targeted flow battery, characterized in that: The method is achieved by the following steps: S1. Disassemble the waste lithium iron phosphate battery, separate the positive electrode, rinse and dry it; S2. Calculate the missing amount, surface load and surface capacity of lithium ions in the waste LFP positive electrode sheet; S3, construct a zinc-iron liquid flow battery, the liquid flow battery comprising a diaphragm, a positive electrode storage tank and a negative electrode storage tank, the positive electrode storage tank is filled with a positive electrode electrolyte, the negative electrode storage tank is filled with a negative electrode electrolyte, the positive electrode electrolyte contains [Fe(CN)6] 3- ; S4, then placing the positive electrode sheet treated in S1 into the positive electrode storage tank of the liquid flow battery, discharging the liquid flow battery at a constant current, and naturally cooling to room temperature after the discharge, thereby obtaining a repaired and regenerated lithium iron phosphate positive electrode sheet; In S2, the degree of lithium ion deficiency in the waste lithium iron phosphate electrode sheet is tested by ICP-MS, and the loading amount and surface capacity per unit area of the electrode sheet are measured by an analytical balance; In S3, [Fe(CN)6] 3- The concentration is 0.01M~0.7M; In S3, the positive electrode electrolyte further includes an auxiliary electrolyte; The auxiliary electrolyte is LiCl, and the concentration of LiCl is 3M; In S3, the negative electrode electrolyte consists of ZnBr2, LiOH and deionized water; The concentration of ZnBr2 is 0.4M, and the concentration of LiOH is 3M; In S3, the steps of preparing the diaphragm are as follows: (1) mixing a polymer, carbon black and a solvent in a mass ratio of (0.05-1):(2-8):(100-1000) to obtain a solution; (2) forming the solution on the surface of the ion exchange membrane by spraying, spin coating, rolling, brushing, scraping or interfacial polymerization, and then volatilizing the solvent to obtain the diaphragm; The polymer is PVDF, PTFE or acrylic polyurethane; the carbon black is super carbon black, Ketjen black or ordinary carbon black; the solvent is one or more of water, isopropyl alcohol, ethanol, N-methylpyrrolidone, dimethyl sulfoxide and N,N-dimethylformamide; In S4, the constant current discharge time is 1h~24h, the reaction temperature is 25℃~60℃, and the current density is controlled at 1mA / cm 2 ~100mA / cm 2 , the voltage range is controlled at 0.01V~2V; In S4, the reaction temperature was 50°C and the current density was controlled at 20 mA / cm 2 .