Remanufacturing composite repairing liquid and method for remanufacturing lithium ion battery

Abstract

The invention discloses a remanufacturing composite repair liquid and a method for remanufacturing a lithium ion battery, and belongs to the technical field of lithium ion batteries and remanufacturing. The remanufacturing composite repair liquid is specifically an electrolyte containing 2, 2, 6, 6-tetramethylpiperidine oxide (TEMPO) and 10-methylphenothiazine (MPT), and the remanufacturing composite repair liquid is prepared from the following raw materials in parts by weight: 20-30% of an electrolyte containing 2, 2, 6, 6-tetramethylpiperidine According to the method, the TEMPO and the MPT are dissolved in the electrolyte to prepare the remanufactured composite repair liquid, the TEMPO and the MPT in the composite repair liquid can be subjected to an oxidation-reduction reaction with the dead lithium, the dead lithium is oxidized into active Li < + > synergistically, and regeneration of the dead lithium is completed. The prepared remanufacturing composite repairing liquid is used for remanufacturing the lithium ion battery, so that the requirement on new material production can be greatly reduced, and the influence of a scrapped battery on the environment can be furthest reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium-ion batteries and remanufacturing, and in particular relates to a method for remanufacturing a composite repair fluid and a lithium-ion battery. Background Art

[0002] With the rapid increase in the application of lithium-ion batteries, the environmentally friendly and low-cost recycling of waste lithium batteries has become an urgent problem to be solved. However, existing recycling technologies such as physical recycling, pyrometallurgical recycling, and wet recycling have defects such as long process time and high input costs, which require increased energy consumption. In addition, according to the automotive industry, batteries eliminated from electric vehicles still retain about 80% of their initial capacity. Such a high capacity is retained, which indicates that most of the materials in the battery are still active, and decomposing and recycling the battery will result in a complete loss of the remaining 80% of the capacity. Remanufacturing lithium-ion batteries will greatly reduce the demand for new material production and minimize the impact of scrapped batteries on the environment.

[0003] The aging mechanism of battery materials is a complex issue. There are two main ways for batteries to fail: damage to active materials and loss of active lithium. (1) Damage to active materials includes irreversible phase change, particle cracking, and electrical contact loss. (2) Loss of active lithium includes the formation of SEI film and lithium plating. During the charging process, active lithium ions undergo irreversible reductive decomposition with the electrolyte at the graphite anode / electrolyte interface to form a solid electrolyte interface (SEI) film. The formation of the SEI film prevents further reductive decomposition, which is one of the reasons for the loss of active ions. In addition, negative electrode lithium plating is also the main cause of active lithium ion loss, which refers to the process of lithium ions depositing from the electrolyte to the negative electrode surface. They consume lithium ions, which no longer participate in the cycle process, causing battery capacity decay. Active material loss often occurs during operation at extreme temperatures. For safety reasons, batteries used in large-scale applications are usually operated in temperature-controlled systems. In these systems, the loss of active lithium ions is often the main aging mode.

[0004] At present, remanufacturing technologies include chemical methods to repair positive or negative electrode materials, physical cleaning of interface layers, etc., but these technologies still do not completely improve the shortcomings of cumbersome processes and high investment costs. Therefore, it is of great significance to propose a lithium-ion battery remanufacturing technology with lower costs and simpler processes. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a remanufacturing composite repair liquid and a method for remanufacturing lithium-ion batteries. By adding 2,2,6,6-tetramethylpiperidinyl oxide and 10-methylphenothiazine to the electrolyte, a remanufacturing composite repair liquid capable of activating dead lithium is obtained, and the obtained remanufacturing composite repair liquid can be used for the preparation of remanufacturing lithium-ion batteries.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a remanufacturing composite repair liquid, specifically an electrolyte containing 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) and 10-methylphenothiazine (MPT).

[0008] Preferably, the concentration of the 2,2,6,6-tetramethylpiperidinyl oxide in the electrolyte is 20-50 mM; the concentration of the 10-methylphenothiazine in the electrolyte is 20-50 mM.

[0009] The second technical solution of the present invention is to provide a method for remanufacturing lithium-ion batteries based on the above-mentioned remanufacturing composite repair fluid, the steps comprising:

[0010] The remanufactured composite repair fluid is injected into the waste lithium-ion battery, and the injection hole is sealed to obtain a remanufactured lithium-ion battery.

[0011] For the purpose of regenerating waste lithium-ion batteries, the electrolyte used in the remanufacturing composite repair fluid is preferably the same as the electrolyte of the waste lithium-ion battery to be regenerated, and conventional lithium-ion battery electrolyte is also acceptable.

[0012] Preferably, the injection volume of the remanufacturing composite repair liquid is 1 to 3000 μL.

[0013] Preferably, the method of sealing the injection hole includes sealing with sealant or spot welding.

[0014] The beneficial technical effects of the present invention are as follows:

[0015] The present invention prepares a remanufacturing composite repair solution by dissolving TEMPO and MPT in an electrolyte. The TEMPO and MPT in the composite repair solution can undergo a redox reaction with dead lithium to synergistically oxidize the dead lithium into active Li + , completing the regeneration of dead lithium.

[0016] The remanufacturing composite repair fluid provided by the present invention can be used to remanufacture lithium-ion batteries. The remanufacturing method provided by the present invention greatly reduces the demand for new material production and can minimize the impact of scrapped batteries on the environment. The remanufacturing process provided by the present invention is simple, does not require complex equipment and experimental steps, has a short cycle, and is conducive to popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of using the regenerated repair fluid to repair waste lithium iron phosphate batteries.

[0018] Figure 2This is a comparison chart of the cycle performance before and after the electrolyte in Examples 1 to 4 is used to repair the waste lithium iron phosphate battery of the present invention.

[0019] Figure 3 This is a comparison chart of the cycle performance before and after repairing a waste lithium iron phosphate battery using the remanufactured composite repair fluid of Example 1 of the present invention.

[0020] Figure 4 This is a comparison chart of the cycle performance before and after repairing a waste lithium iron phosphate battery using the TEMPO remanufacturing repair fluid of Example 2 of the present invention.

[0021] Figure 5 This is a comparison chart of the cycle performance before and after repairing a waste lithium iron phosphate battery using the MPT remanufacturing repair fluid of Example 3 of the present invention.

[0022] Figure 6 This is an EIS comparison diagram before and after the waste lithium iron phosphate battery is repaired using the remanufactured composite repair fluid of Example 1 of the present invention.

[0023] Figure 7 This is a comparison chart of the cycle rates of remanufactured lithium-ion batteries repaired using the remanufactured composite repair fluid of Example 1 and the electrolytes of Examples 1 to 4 of the present invention.

[0024] Figure 8 These are SEM images of the negative electrode of a used lithium iron phosphate battery before remanufacturing, where (a) to (c) are SEM images at different magnifications.

[0025] Fig. 9 This is a SEM image of the negative electrode of a waste lithium iron phosphate battery after 5 cycles of injection of the remanufacturing composite repair liquid of Example 1, wherein (a) to (c) are SEM images at different magnifications.

[0026] Fig.10 This is the XRD diagram of the positive electrode of the waste lithium iron phosphate battery before and after 5 cycles of injection of the remanufacturing composite repair liquid of Example 1. DETAILED DESCRIPTION

[0027] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0028] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0029] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0030] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0031] The electrolyte composition of the waste lithium iron phosphate battery used in the present invention is lithium hexafluorophosphate (LiPF6) dissolved in dimethyl carbonate (DEC), ethylene carbonate (EC) and diethyl carbonate (DEC), the solvent volume ratio is 1:1:1, and the LiPF6 concentration is 1M.

[0032] Example 1

[0033] Preparation of remanufacturing composite repair fluid:

[0034] In a glove box, TEMPO and MPT were dissolved in an electrolyte consisting of 1 M LiPF6 dissolved in DMC:EC:EMC=1:1:1 Vol%, and magnetic stirring was performed for 0.5 h to obtain a remanufacturing composite repair solution with a TEMPO concentration of 20 mM and an MPT concentration of 20 mM.

[0035] Example 2

[0036] Preparation of TEMPO remanufacturing repair fluid:

[0037] In a glove box, TEMPO was dissolved in an electrolyte solution consisting of 1 M LiPF6 dissolved in DMC:EC:EMC=1:1:1 Vol%, and magnetic stirring was performed for 0.5 h to obtain a TEMPO remanufacturing repair solution with a TEMPO concentration of 40 mM.

[0038] Example 3

[0039] Preparation of MPT remanufacturing repair fluid:

[0040] In a glove box, MPT was dissolved in an electrolyte solution consisting of 1 M LiPF6 dissolved in DMC:EC:EMC=1:1:1 Vol%, and magnetic stirring was performed for 0.5 h to obtain an MPT remanufacturing repair solution with an MPT concentration of 40 mM.

[0041] Example 4

[0042] In a glove box, TEMPO and MPT were dissolved in an electrolyte consisting of 1 M LiPF6 dissolved in DMC:EC:EMC=1:1:1 Vol%, and magnetic stirring was performed for 0.5 h to obtain a remanufacturing composite repair solution with a TEMPO concentration of 50 mM and an MPT concentration of 50 mM.

[0043] The regenerated repair liquid prepared in Examples 1 to 4 is used to repair the interior of the waste lithium iron phosphate battery. The method is to first perform a complete discharge treatment on the waste lithium iron phosphate battery in the battery cabinet, and use the tip of the syringe needle to make a hole in the middle of the opposite side of the positive and negative terminals of the battery in the glove box (avoid the positive and negative electrodes during injection to prevent battery failure due to electrode damage or short circuit). Then, use a syringe to absorb the regenerated repair liquid prepared in Examples 1 to 4, that is, a blank electrolyte that does not contain TEMPO or MPT, and slowly inject it into the waste lithium iron phosphate battery. The injection volume is 1 mL. After the injection is completed, the injection hole is sealed with a sealant to ensure that the electrolyte does not overflow and cannot contact the air, thereby obtaining a remanufactured lithium-ion battery. The flow chart of the present invention using the regenerated repair liquid to repair waste lithium iron phosphate batteries is shown in FIG. Figure 1 .

[0044] Battery test: Each remanufactured lithium-ion battery was left to stand for 12 hours to allow the internal electrolyte to be evenly infiltrated. The rested battery was tested at room temperature on a battery cabinet with a 1C (180mAh) constant current charge and discharge test, and the charge and discharge cut-off voltage was 2.5 to 4.2V.

[0045] After remanufacturing, the capacity recovery rate of the remanufactured lithium-ion battery using the electrolyte in Examples 1 to 4 is 0. The comparison of the cycle performance of the lithium-ion battery before and after remanufacturing is shown in FIG. Figure 2 The capacity recovery rate of the remanufactured lithium-ion battery using the remanufactured composite repair fluid of Example 1 is 11.3%, and the capacity retention rate is even higher. The capacity will decay to the value before remanufacturing after nearly 250 cycles, and the new battery will reach the standard of scrapped battery after nearly 250 cycles, indicating that the life of the scrapped battery can be doubled after remanufacturing with the composite repair fluid. The comparison of the cycle performance of the lithium-ion battery before and after remanufacturing is shown in FIG. Figure 3 The capacity recovery rate of the remanufactured lithium-ion battery using the TEMPO remanufacturing repair fluid of Example 2 is 5.4%, and the cycle performance comparison of the lithium-ion battery before and after remanufacturing is shown in FIG. Figure 4The capacity recovery rate of the remanufactured lithium-ion battery using the MPT remanufacturing repair fluid of Example 3 is 5.9%, and the cycle performance comparison of the lithium-ion battery before and after remanufacturing is shown in the figure Figure 5 ; The capacity recovery rate of the remanufactured lithium-ion battery using the remanufactured composite repair fluid of Example 4 is 11.1%.

[0046] After remanufacturing, the electrochemical impedance spectroscopy (EIS) comparison diagram of the remanufactured lithium ion battery using the remanufactured composite repair fluid of Example 1 before and after remanufacturing is shown in Figure 6 . Figure 6 It shows that the battery EIS after adding the repair fluid is significantly smaller than that before remanufacturing, which can be attributed to the fact that the composite helps to form a more stable SEI film.

[0047] The rate cycle comparison diagram of the remanufactured lithium ion battery repaired by the remanufactured composite repair solution of Example 1 and the electrolyte in Examples 1 to 4 is shown in Figure 7 . Figure 7 It shows that the battery rate performance is better when adding the remanufactured composite repair fluid.

[0048] The SEM image of the negative electrode of the waste lithium iron phosphate battery before injection of the remanufacturing composite repair solution of Example 1 is shown in Figure 8 , wherein (a) to (c) are SEM images at different magnifications. The SEM image of the negative electrode of the waste lithium iron phosphate battery after 5 cycles of injection of the remanufacturing composite repair liquid of Example 1 is shown in FIG. Fig. 9 , where (a) to (c) are SEM images at different magnifications.

[0049] from Figure 8 It can be seen from the figure that there are dead lithium and lithium dendrites on the negative electrode surface of the waste lithium iron phosphate battery before remanufacturing. Fig. 9 It shows that after repair with the remanufacturing composite repair fluid, the surface of the negative electrode is smoother, and dead lithium and lithium dendrites are eliminated, which indirectly explains the changes in the electrochemical performance of the battery.

[0050] The XRD pattern of the positive electrode of the waste lithium iron phosphate battery before and after 5 cycles of injection of the remanufacturing composite repair liquid of Example 1 is shown in Fig.10 .

[0051] Fig.10 It shows that FePO4 phase appeared in the positive electrode before remanufacturing, indicating that inactive lithium was produced during the charge and discharge process. This part of inactive lithium cannot return to the positive electrode after discharge and combines with FePO4 to reform LiFePO4, thus forming FePO4. The characteristic peak of the FePO4 phase in the positive electrode after remanufacturing is much smaller, indicating that a part of the dead lithium is reactivated and activated into active lithium ions, which are re-entered into the battery cycle process, thereby achieving the effect of recovering the battery capacity.

[0052] Based on the above experimental results, the present invention provides an in-situ remanufacturing technology for waste lithium-ion batteries based on the principle of composite synergistic dead lithium activation, including materials used in the remanufacturing process and remanufacturing processing methods. This technology targets commercial scrapped lithium-ion batteries, and injects repair fluid into lithium-ion batteries that are about to be scrapped to extend or stabilize the performance of lithium-ion batteries. The experimental process is: dissolving the composite in an electrolyte to obtain a remanufacturing repair fluid, and injecting the repair fluid into a used lithium-ion battery. This method has a simple operation process, targets full batteries, does not require disassembly of the battery, and therefore will not cause damage to the battery due to human factors. The remanufacturing composite repair fluid can not only prolong and stabilize battery performance, but also has a battery protection effect, and has good application prospects.

[0053] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A remanufacturing composite repair fluid, characterized in that: The remanufacturing composite repair liquid is specifically an electrolyte containing 2,2,6,6-tetramethylpiperidinoxide and 10-methylphenothiazine.

2. The remanufacturing composite repair liquid according to claim 1, characterized in that: The concentration of the 2,2,6,6-tetramethylpiperidinyl oxide in the electrolyte is 20-50 mM; the concentration of the 10-methylphenothiazine in the electrolyte is 20-50 mM.

3. A method for remanufacturing a lithium-ion battery based on the composite repair fluid according to claim 1 or 2, characterized in that the steps include: The remanufactured composite repair fluid is injected into the waste lithium-ion battery, and the injection hole is sealed to obtain a remanufactured lithium-ion battery.

4. The method for remanufacturing a lithium-ion battery according to claim 3, characterized in that: The injection volume of the remanufacturing composite repair liquid is 1 to 3000 μL.

5. The method for remanufacturing a lithium-ion battery according to claim 3, characterized in that: The method of sealing the injection hole includes sealing with sealant or spot welding.

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