A method for in-situ repair of lithium ion batteries without disassembly

Abstract

The present application relates to the technical field of lithium ion battery recycling and reuse, and particularly relates to a method for in-situ repair of lithium ion batteries without disassembly, comprising: establishing a pressure field with periodic switching of negative pressure state and positive pressure state inside the battery cell through airtight coupled pressure generating device, using the breathing pumping effect to deeply infiltrate the repair medium containing SEI film forming functional components and acidic substance capturing functional components into the electrode assembly, and forming and updating the repair medium microenvironment at the electrode interface; under the continuous action of the pressure field, applying a time-sequential progressive mode electric excitation to the battery cell, sequentially performing low-rate basic cycle, step charging with pulse current and standing relaxation under partial state of charge, driving the functional components to directionally undergo electrochemical reaction, in-situ generating and densifying SEI film, and neutralizing acidic substances; the capacity recovery rate of the repaired battery reaches 85% to 95%, and the cycle life reaches more than 80% of the initial level.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery recycling and reuse technology, specifically to a method for non-disassembly in-situ repair of lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and large-scale energy storage systems due to their advantages such as high energy density, long cycle life, and low self-discharge rate. However, battery performance inevitably degrades during long-term use, and electrolyte degradation is one of the key factors leading to this performance decline.

[0003] Electrolytes are typically composed of organic carbonate solvents (such as ethylene carbonate EC, dimethyl carbonate DMC, ethyl methyl carbonate EMC, etc.), lithium salts (mainly lithium hexafluorophosphate LiPF6), and functional additives. During the charge-discharge cycle of the battery, the electrolyte will gradually deteriorate due to the following reasons: (1) LiPF6 has poor thermal stability and is easily decomposed in the presence of trace amounts of moisture to produce corrosive products such as HF and POF3; (2) Organic solvents undergo redox decomposition on the electrode surface, leading to solvent consumption and product accumulation; (3) Repeated rupture and regeneration of the solid electrolyte interfacial film continuously consume active lithium and electrolyte; (4) Transition metal ions from the positive electrode dissolve and migrate to the negative electrode, catalyzing the decomposition reaction of the electrolyte.

[0004] To address the above problems, the existing technologies mainly adopt the following repair strategies: (1) Additive repair method, which adds functional compounds to the aged electrolyte to capture HF and moisture, but this method usually requires disassembling the battery, which is complicated and difficult to ensure the uniform distribution of the repair solution inside the cell; (2) Liquid replenishment repair method, which restores the performance by replenishing the battery with fresh electrolyte, but the traditional liquid injection method relies on single negative pressure or normal pressure injection, and the wetting effect is limited; (3) Recycling and regeneration method, which recovers electrolyte components through processes such as distillation and extraction, but it has high energy consumption, complicated processes, and difficulty in maintaining the original ratio of additives.

[0005] Regarding electrolyte replenishment and repair technology, existing patent CN119253217A discloses a method for replenishing and repairing lithium-ion batteries, employing a negative pressure injection and a negative pressure-pressurization cyclic injection method involving multiple small injections. While this method can improve the electrolyte wetting effect to some extent, its "negative pressure-pressurization cycle" is merely a simple pressure switching process, lacking clear control of pulsation parameters (such as the negative pressure / micro-positive pressure range, pulsation cycle duration, and number of pulsation cycles). This fails to generate an effective "breathing effect" to promote deep penetration of the repair solution into the electrode micropores. Furthermore, this method only focuses on the injection process itself, neglecting the post-injection electrochemical activation process, making it difficult to effectively restore the battery interface performance after repair.

[0006] Existing patent CN103117419A discloses a method for repairing waste lithium-ion batteries, which adopts a process route of discharge → drilling → vacuum drying → electrolyte injection → sealing → charging activation. Although the method is simple to operate, it has the following shortcomings: (1) It only uses conventional vacuum drying and atmospheric pressure injection methods, and the electrolyte wetting depth is limited; (2) The injected electrolyte is a common electrolyte containing conventional additives (such as vinylene carbonate), which does not have the dual functions of in-situ repair of SEI film and HF capture; (3) The charging activation is only a simple low-rate constant current charging, and pulse electrochemical activation technology is not used, so the SEI film structure cannot be effectively reconstructed.

[0007] Therefore, developing an electrolyte repair method that does not require battery disassembly, achieves deep wetting of the repair solution through precisely controlled alternating negative and micro-positive pressure injection, and combines multi-stage stepwise pulsed electrochemical activation to achieve in-situ reconstruction of the SEI membrane is of great practical significance for improving battery repair effect and extending the service life of lithium-ion batteries. Summary of the Invention

[0008] The purpose of this invention is to provide a non-disassembly in-situ repair method for lithium-ion batteries, which alternately performs pressure field intervention and electrochemical interface reconstruction to form a repair cycle, utilizes pressure pulsation to deeply wet a dual-function repair medium, and combines pulsed electrical excitation to generate and densify an SEI film in situ, while simultaneously capturing acidic substances, resulting in a capacity recovery rate of 85% to 95% after repair.

[0009] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: A method for non-disassembly in-situ repair of lithium-ion batteries involves alternating pressure field intervention and electrochemical interface reconstruction within the battery cell to form a repair cycle within the cell. The repair cycle includes: By using a pressure generating device that is airtightly coupled to the liquid injection port of the battery cell, a pressure field that periodically switches between negative and positive pressure states is established and maintained inside the battery cell. The breathing pumping effect generated by this pressure field in the microporous structure of the electrode assembly is used to draw in the repair medium and drive it to the depth of the electrode assembly, so as to form and renew the repair medium microenvironment that can supply chemical reactions at the electrode interface. Under the continuous action of the pressure field, a patterned electrical excitation is applied to the battery cell, causing the first and second functional components in the repair medium to undergo a directional electrochemical reaction at the electrode interface in the microenvironment maintained by the pressure field, so as to generate and densify the solid electrolyte interface film in situ, while neutralizing acidic substances. The repair medium comprises a first functional component with film-forming function and a second functional component with acid substance capture function; the patterned electrical excitation includes, in sequence, a low-rate base cycle, a stepped charge with pulsed current, and a rest relaxation in a partially charged state.

[0010] Furthermore, the gauge pressure of the pressure field in the negative pressure state is -90 kPa to -60 kPa, the gauge pressure in the positive pressure state is 10 kPa to 30 kPa, the duration of a single pressure switching cycle is 3 to 8 minutes, and the pressure field continuously executes 5 to 15 switching cycles.

[0011] Furthermore, the repair medium is a liquid composition formulated under anhydrous conditions from the following components: 60wt%-85wt% matrix solvent, 10wt%-15wt% conductive lithium salt, 2wt%-8wt% first functional component, 1wt%-5wt% second functional component, and 0.5wt%-2wt% moisture scavenger.

[0012] Furthermore, the first functional component is at least one of fluoroethylene carbonate and vinylene carbonate; The second functional component is a silane compound containing trimethoxysilane or triethoxysilane, or a trifluoroacetamide compound containing silicon nitrogen.

[0013] Furthermore, in the standardized electrical excitation, the low-rate base cycle is performed 3 to 5 charge-discharge cycles with a constant current of 0.02C to 0.05C within a voltage range of 2.5V to 4.2V; the stepped charging with pulsed current charges the cell to 3.8V-4.0V with a constant current of 0.1C, then applies an alternating pulsed current with a frequency of 0.5Hz-2Hz and a duty cycle of 30%-70% for 5 to 15 minutes, and then continues charging to 4.1V-4.25V with a constant current of 0.05C; the resting relaxation involves adjusting the cell's state of charge to 50%-70% and then resting for 24 to 48 hours.

[0014] Furthermore, while establishing and maintaining the pressure field, the internal pressure of the battery cell is sensed in real time to adjust the frequency, amplitude, and amount of repair medium injection for pressure switching in a closed loop; while applying the patterned electrical excitation, the internal resistance of the battery cell is sensed in real time, and the frequency or duty cycle of the pulse current is adjusted based on the rate of change of internal resistance, or a switch to the resting relaxation is triggered.

[0015] Furthermore, before alternating the pressure field intervention and electrochemical interface reconstruction inside the cell, the cell is first identified and pre-conditioned. The identification involves screening cells with a capacity retention rate between 40% and 80% and an internal resistance increase of no more than 200%. The pre-conditioning involves discharging the selected cells with a small current to a cutoff voltage of 2.5V-3.0V and then letting them stand in an inert atmosphere and at a constant temperature for 12 to 24 hours to homogenize their internal electrochemical state.

[0016] On the other hand, the present invention proposes a non-disassembly in-situ repair system for lithium-ion battery electrolyte, configured to implement the above-described method, the system comprising: The pressure field generating device is configured to be airtightly connected to the battery cell's liquid injection port, and is used to generate and maintain a pressure field that alternates periodically between a negative pressure state and a positive pressure state inside the battery cell. An electrical excitation generating device is configured to be electrically connected to the cell electrodes for generating and applying the patterned electrical excitation; A multi-physical quantity sensing device includes at least a pressure sensor for sensing the internal pressure of the battery cell and an internal resistance detection unit for sensing the internal resistance of the battery cell, so as to acquire process parameters characterizing the state of the battery cell in real time. The controller is electrically connected to the multi-physical quantity sensing device, the pressure field generating device, and the electrical excitation generating device, and is configured to receive the process parameters and output control commands to the pressure field generating device and the electrical excitation generating device according to preset logic or dynamic optimization algorithm to form closed-loop adaptive control.

[0017] The beneficial effects of this invention are: This invention establishes and maintains a pressure field that periodically switches between negative and positive pressure states within the battery cell. Utilizing the breathing pump effect generated by the alternating pressure in the micropores of the electrode assembly, the repair medium achieves deep wetting of the entire electrode and separator after 5 to 15 consecutive pulsation cycles. This overcomes the limitation of atmospheric pressure injection or simple negative-pressurization cycles where the repair medium only wets the surface area. When the pressure field alternates between a negative pressure state (10 kPa to 40 kPa) and a positive pressure state (111 kPa to 131 kPa) with a single cycle duration of 3 to 8 minutes, the negative pressure state extracts gas and residual liquid from the micropores, forming a momentary negative pressure cavity. The positive pressure state forces the repair medium into this cavity under a positive pressure difference. Each pulsation cycle completes one "suction-push" cycle, continuously disrupting the flow equilibrium established by the repair medium in the micropores due to viscosity and surface tension, driving it step by step deeper into the electrode and separator. The comparative example used atmospheric pressure injection, and the repair medium only accumulated near the injection port and could not penetrate into the micropores. The subsequent electrochemical film formation reaction was difficult to occur uniformly on the entire electrode surface due to insufficient supply of repair medium at the interface. The capacity recovery rate was 18 percentage points lower than that of the embodiment of the present invention, and the cycle retention rate was 14 percentage points lower.

[0018] This invention employs a repair medium containing a first functional component and a second functional component. This medium is delivered to the electrode interface by a pressure field, continuously renewing the microenvironment at the interface. Then, a patterned electrical excitation drives the first functional component to undergo a directional electrochemical reaction on the electrode surface, generating and densifying the SEI film in situ. Simultaneously, the second functional component captures acidic substances in the electrolyte within the same microenvironment, completing interface repair and electrolyte purification within the same repair cycle. The first functional component is selected from fluoroethylene carbonate or vinylene carbonate, whose reduction potential is higher than that of the matrix solvent. During the stepped charging stage, it preferentially undergoes reduction and decomposition on the electrode surface, and the decomposition products are deposited and cross-linked at the original SEI film defect sites. During the pulse conduction period, the transient overpotential breaks the concentration polarization layer on the electrode surface, promoting the continuous replenishment of the first functional component to the interface. During the pulse turn-off period, the newly formed SEI film components gain a structural relaxation window, tending towards densification rather than forming a loosely packed layer. The second functional component is a silane containing trimethoxysilane or triethoxysilane groups. Its silicon-oxygen bonds and alkoxy groups selectively react with hydrogen fluoride produced from the decomposition of lithium hexafluorophosphate, generating chemically inert silicon-containing fluorides that block the corrosion of electrode materials and current collectors by acidic substances. The periodic alternation of the pressure field induces microflow of the repair medium in each pulsation cycle, pushing the fresh functional component solution to the interface and carrying away byproducts, maintaining stable component concentration, and ensuring continuous film formation and capture reactions. The battery capacity recovery rate after repair can reach 85% to 95%.

[0019] This invention alternates between pressure field intervention and patterned electroexcitation, forming a synergistic repair cycle of physical and electrochemical fields, unlike the simple sequential process of liquid injection and charging activation in existing technologies. In existing technologies, charging is performed immediately after liquid injection in a closed system, resulting in a continuous decrease in the concentration of functional components at the interface due to electrochemical reactions. Without an external replenishment mechanism, the film formation rate and uniformity are limited by the diffusion mass transfer limit. In this invention, pressure field intervention continues throughout the entire repair process. The continuously generated periodic pressure alternation induces microflow of the repair medium in the micropores of the electrode assembly, continuously delivering fresh functional components to the interface and removing byproducts, maintaining a dynamic stability of component concentration at the interface. Patterned electroexcitation proceeds sequentially based on this dynamically updated microenvironment: a low-rate base cycle completes the gentle activation of the electrode material and the pre-distribution of functional components at the interface; pulsed step charging drives the first functional component to form a film at the interface and promotes film densification using pulsed relaxation gaps; and static relaxation allows the SEI film to transition from a metastable state to a thermodynamically stable state. The physical field drives the material distribution and the electrochemical field drives the interface reaction, which are alternately coupled. After repair, the battery cycle life reaches more than 80% of the initial cycle life.

[0020] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 Flowchart of in-situ repair method for lithium-ion battery electrolyte; Figure 2 A schematic diagram of the pressure change curve during the negative pressure pulsating injection process; Figure 3 This is a schematic diagram of the current-voltage curve for a step-pulse electrochemical activation protocol. Figure 4 This is a schematic diagram of an in-situ repair system for lithium-ion battery electrolyte. Figure 5 This is a schematic diagram of the cycle performance (1C, 25°C) of the lithium iron phosphate battery described in Example 1; Figure 6 This is a schematic diagram of the cycle performance (1C, 25℃) of the ternary material power battery described in Example 2; Figure 7 This is a schematic diagram showing the original and conventionally repaired cycle performance (1C, 25℃) of the lithium iron phosphate battery described in Comparative Example 1. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a method for non-disassembly in-situ repair of lithium-ion batteries. The essence of this method lies in alternately applying pressure field intervention and electrochemical interface reconstruction within the battery cell, thereby establishing a complete repair cycle within the cell.

[0025] In some embodiments, before performing the above-described repair cycle, the waste lithium-ion batteries to be repaired are first subjected to a graded condition assessment. This assessment uses non-destructive testing to sequentially test the battery's capacity, AC internal resistance, open-circuit voltage, and individual cell voltage consistency. Based on the test results, it is determined whether the battery meets preset repair admission criteria, thereby eliminating unsuitable scrap batteries. The preset repair admission criteria are as follows: the battery's current capacity retention rate is within the range of 40% to 80% of its nominal initial capacity, and the increase in the battery's current internal resistance compared to the initial internal resistance at the factory does not exceed 200%; at the same time, the open-circuit voltage difference of the individual cells is required to not exceed 50mV, and there are no visible defects in the battery appearance such as casing bulges, leakage, or tab corrosion.

[0026] For batteries deemed qualified for repair after evaluation, a pre-equilibrium treatment is performed. This pre-treatment step involves: discharging the battery at a constant current rate of 0.05C to 0.1C until the battery voltage drops to a preset cutoff voltage of 2.5V to 3.0V; subsequently, the discharged battery is placed in a sealed, temperature-controlled chamber, and high-purity nitrogen or argon gas is continuously introduced into the chamber to create an inert protective atmosphere. The chamber is then kept at 25°C ± 5°C for 12 to 24 hours. The purpose of this pre-equilibrium treatment is to gradually stabilize the electrolyte distribution, the electrochemical state of the electrode interfaces, and the lithium distribution within the battery, thereby effectively eliminating localized polarization differences within the battery and creating uniform initial conditions for the smooth implementation of subsequent repair cycles.

[0027] After completing the above-mentioned equilibrium pretreatment, the repair cycle, consisting of alternating pressure field intervention and electrochemical interface reconstruction, officially begins.

[0028] The pressure field intervention step in the repair cycle is implemented as follows: The pre-drilled injection port on the battery casing is opened, and a pressure generating device, airtightly coupled to the injection port, is used to quantitatively inject the repair medium into the cell. This repair medium is a dual-function liquid composition, comprising, by mass percentage: 60% to 85% matrix solvent, 10% to 15% conductive lithium salt, 2% to 8% of a first functional component for solid electrolyte interfacial film formation, 1% to 5% of a second functional component for acid capture, and 0.5% to 2% trace moisture remover. All components are mixed and stirred in a sealed, moisture-free environment. After thorough mixing, the mixture is sealed and stored, and used only as needed. The overall moisture content of the repair medium is strictly controlled below 10 ppm.

[0029] In some more specific embodiments, the matrix solvent is selected from two or more of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, and blended in any proportion. The conductive lithium salt is selected from one or two of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. The first functional component, i.e., the component with solid electrolyte interfacial film-forming function, is selected from one or two of fluoroethylene carbonate and vinylene carbonate. The second functional component, i.e., the component with acid substance capture function, is selected from any one of trimethoxysilane, triethoxysilane, and N,O-bis(trimethylsilyl)trifluoroacetamide.

[0030] In the pressure field intervention step, a pressure generating device establishes and maintains a pressure field within the cell that periodically switches between negative and positive pressure states. Specifically, the gauge pressure in the negative pressure state is -90 kPa to -60 kPa, and the gauge pressure in the positive pressure state is 10 kPa to 30 kPa. The duration of each single pressure switching cycle is set to 3 to 8 minutes, and this pressure field is continuously executed for 5 to 15 complete switching cycles. Utilizing the breathing pump effect generated by this pressure field in the microporous structure of the electrode assembly, the repair medium is repeatedly drawn in and displaced deep into the electrode assembly, thereby forming and continuously renewing a repair medium microenvironment at the electrode interface that can power chemical reactions. The entire injection process is completed under conditions where the cavity remains sealed to prevent external moisture and air from intruding into the cell.

[0031] In some embodiments, during the execution of the pressure field intervention step, a pressure sensor built into the cell or pipeline is used to collect dynamic pressure signals inside the cell in real time. Based on the pressure feedback signal, the frequency of pressure switching, pressure amplitude, and the amount of repair medium injected in a single injection are adaptively and closed-loop adjusted to drive the repair medium to achieve uniform permeation throughout the entire area along the gap between the electrode and the diaphragm of the cell.

[0032] In one specific implementation, the closed-loop adaptive control includes: (i) Pressure feedback control: When the built-in pressure sensor detects that the internal pressure of the cell cannot drop to the target value (e.g. -75kPa) within 30 seconds under negative pressure, the controller increases the pumping speed of the vacuum pump or extends the negative pressure maintenance time; when the pressure rise rate under positive pressure is less than 0.5kPa / s, the controller increases the duty cycle of the micro positive pressure push.

[0033] (ii) Internal resistance feedback control: During the step-pulse cycle activation phase, the average rate of decrease of internal resistance within 5 minutes is calculated in real time. When the rate of decrease is less than 2% for two consecutive times, the controller determines that the film formation reaction is nearing completion and automatically reduces the pulse frequency from 1Hz to 0.5Hz or the duty cycle from 50% to 30%, or directly terminates the pulse activation phase and switches to the resting relaxation phase.

[0034] In some embodiments, a short pre-resting buffer step is added after the pressure field intervention step is completed and before the electrochemical interface reconstruction step begins. This step involves placing the battery cell that has undergone electrolyte injection in a sealed environment at 25°C ± 3°C for 2 to 6 hours to allow the repair medium to more fully penetrate the micropores of the electrode and separator, thereby eliminating potential localized concentration unevenness caused by the electrolyte injection process.

[0035] The electrochemical interface reconstruction step in the repair cycle is performed after the pressure field intervention step, and conceptually, this electrochemical interface reconstruction is implemented based on the repair medium microenvironment created by the aforementioned pressure field. This step applies a time-progressive patterned electrical excitation to the cell, which sequentially includes three stages: low-rate base cycling, stepped charging with pulsed current, and rest relaxation in a partially charged state.

[0036] In the first stage, the low-rate base cycle stage, the cell is subjected to 3 to 5 complete charge-discharge cycles at a constant low current of 0.02C to 0.05C. The voltage range for charging and discharging is strictly controlled within the range of 2.5V to 4.2V. This stage employs a constant current charging and constant voltage cutoff discharging mode, the purpose of which is to initially activate the electrode material in a gentle electrochemical manner and to allow the functional components in the repair medium to initially impregnate and distribute at the electrode interface.

[0037] In the second stage, the stepped charging stage with pulsed current, the cell is first charged to a first cutoff voltage of 3.8V to 4.0V using a constant current of 0.1C. Once the cell voltage reaches this first cutoff voltage, an alternating current pulse is applied to the cell. The frequency of this pulse is set to 0.5Hz to 2Hz, the duty cycle is set to 30% to 70%, and the duration of the pulse treatment is set to 5min to 15min. The periodic perturbation of this pulsed current drives the first functional component in the repair medium to migrate directionally on the electrode surface and undergo an electrochemical reaction. After the pulse treatment is completed, the cell is further charged to a second cutoff voltage of 4.1V to 4.25V using a smaller constant current of 0.05C. Throughout this stage, the charging temperature rise of the cell is limited in real time to no more than 8°C by a temperature monitoring unit to avoid the risk of thermal runaway and secondary damage to the electrode interface under reconstruction.

[0038] In the third stage, the resting and relaxation stage, 1 to 3 low-rate charge-discharge cycles are first performed with a current of 0.02C to achieve charge balance within the cell. Subsequently, the state of charge of the cell is adjusted to the range of 50% to 70%, and the cell is left to rest in this state of charge for 24 to 48 hours. This resting and relaxation process allows the solid electrolyte interface film, which was initially formed by pulsed current in the previous stage, to grow naturally and tend to become denser and more stable under conditions without strong electric field interference.

[0039] In some embodiments, during the electrochemical interface reconstruction step, the dynamic changes in the battery's internal resistance are monitored online in real time. When the rate of decrease in internal resistance is detected to be lower than a preset threshold, the system automatically optimizes parameters such as the pulse frequency and duty cycle of the second stage, or directly triggers a switch to the third stage of rest and relaxation, to ensure activation efficiency and avoid over-processing of the cell.

[0040] After completing the aforementioned repair cycle, which alternates between pressure field intervention and electrochemical interface reconstruction, the battery undergoes post-repair aging and conditioning. This process involves removing the battery from the activation equipment and placing it in an open environment at room temperature and pressure with relative humidity controlled below 30% for a prolonged static aging period of 36 to 72 hours. The purpose of aging is to promote the full reaction of residual functional components in the repair medium and to achieve final stability of the electrode interface structure. After aging, a comprehensive performance retest is conducted on the battery, covering at least four indicators: capacity, internal resistance, open-circuit voltage, and initial cycle efficiency, to ultimately confirm the battery's repair effectiveness.

[0041] To make the technical effects of the present invention more intuitive, specific experimental examples are provided below.

[0042] Experimental Example 1 A lithium iron phosphate power battery with a capacity retention rate of 62% and a 3-year cycle service history was selected as the battery to be repaired. The battery has a nominal capacity of 100Ah and a nominal voltage of 3.2V. Capacity testing was conducted on the battery at 25°C and a current of 0.5C, yielding a measured capacity of 62Ah. Its internal resistance was measured using an AC internal resistance meter at a frequency of 1kHz, finding a current internal resistance of 1.8mΩ, compared to an initial factory internal resistance of 1.0mΩ. Both its capacity retention rate and internal resistance increase meet the preset repair criteria of this invention.

[0043] During the equalization pretreatment stage, the battery was discharged to 2.5V at a current of 0.2C, and then placed in a constant temperature chamber at 25°C for 18 hours.

[0044] During the pressure field intervention phase of the repair cycle, the repair medium was prepared. The mass percentages of the components in this repair medium were as follows: ethylene carbonate 30%, methyl ethyl carbonate 40%, lithium hexafluorophosphate 12%, fluoroethylene carbonate (as the first functional component) 5%, trimethoxy(pentafluorophenyl)silane (as the second functional component) 2.5%, and triethyl orthoformate 0.5%. Through the injection port, alternating pulsating injection was performed under negative pressure (-75 kPa) and positive pressure (20 kPa) conditions for a total of 8 pulsating cycles, each lasting 5 minutes. The total injection volume was 15% of the initial injection volume of the battery.

[0045] In the electrochemical interface reconstruction phase of the repair cycle, the battery first enters a low-rate base cycle phase, performing four charge-discharge cycles at a current of 0.03C within a voltage range of 2.5V to 3.8V. This is followed by a stepped charging phase with pulsed current, first charging to 3.8V at 0.1C, then applying an alternating current pulse with a frequency of 1Hz and a duty cycle of 50% for 10 minutes, and finally charging to 3.65V at 0.05C. Finally, a resting relaxation phase is initiated, performing two charge-discharge cycles at 0.03C, adjusting the battery's state of charge to 60%, and then resting in this state for 36 hours.

[0046] The test results after repair showed that the battery's capacity was restored to 89 Ah, with a capacity recovery rate of 89%, and the internal resistance was reduced to 1.2 mΩ. After 500 cycles at 1C and 25°C, its capacity retention rate was 82%.

[0047] Experimental Example 2 A ternary lithium-ion battery with a capacity retention rate of 55% that has been used for 2 years was selected as the battery to be repaired. The nominal capacity of the battery is 50Ah and the nominal voltage is 3.7V. Its measured capacity is 27.5Ah, the current internal resistance is 3.2mΩ, and the initial internal resistance at the factory was 1.5mΩ, which meets the repair conditions.

[0048] During the equalization pretreatment stage, the battery was discharged to 2.8V and left to stand at 25°C for 20 hours.

[0049] During the pressure field intervention phase of the repair cycle, the repair medium was prepared. The mass percentages of the components in this repair medium were as follows: ethylene carbonate 25%, dimethyl carbonate 30%, methyl ethyl carbonate 20%, lithium hexafluorophosphate 12%, fluoroethylene carbonate (as the first functional component) 6%, triethoxysilane (as the second functional component) 3%, molecular sieve desiccant with an average particle size of 2 μm 0.3%, and triethyl orthoformate 0.7%. Alternating pulsating injection was performed under negative pressure (20 kPa) and positive pressure (126 kPa) for a total of 10 pulsating cycles, each lasting 6 minutes. The total injection volume was 18% of the initial injection volume of the battery.

[0050] During the electrochemical interface reconstruction phase of the repair cycle, three low-rate base cycles were first performed at a current of 0.04C within a voltage range of 2.8V to 4.1V. This was followed by a stepped charging phase with pulsed current: first charging to 3.9V at 0.1C, then applying an alternating current pulse with a frequency of 0.8Hz and a duty cycle of 60% for 12 minutes, and finally charging to 4.15V at 0.05C. Finally, a resting relaxation phase was initiated, with two charge-discharge cycles performed at 0.03C, followed by adjusting the battery's state of charge to 55% and allowing it to rest for 40 hours.

[0051] The test results after repair showed that the battery's capacity was restored to 43 Ah, with a capacity recovery rate of 86%, and the internal resistance was reduced to 1.8 mΩ. After 300 cycles at 0.5C and 25°C, its capacity retention rate was 78%.

[0052] Comparative Example 1 To highlight the significant technical advantages of the method provided in this embodiment of the invention, lithium iron phosphate batteries from the same batch as in Experimental Example 1 were selected as the subject of a comparative experiment. The battery had a capacity retention rate of 60% and an internal resistance of 1.9 mΩ. In the comparative experiment, a repair medium with the exact same composition as in Experimental Example 1 was injected into the battery through the injection port under normal atmospheric pressure, with the injection volume also consistent with Experimental Example 1. The electrochemical treatment after repair employed a simple procedure common in the art: five conventional constant current charge-discharge cycles at 0.1C, with a charge-discharge voltage range of 2.5V to 3.65V, followed by a 24-hour resting period before testing.

[0053] The results of the comparative experiment show that after treatment with this traditional repair method, the battery capacity was only restored to 71 Ah, with a capacity recovery rate of 71%, and the internal resistance was reduced to 1.5 mΩ. After 500 cycles under the same 1C rate and 25°C conditions as Experimental Example 1, its capacity retention rate was only 68%. Compared with Experimental Example 1 of this invention, the capacity recovery rate of this comparative example decreased by 18 percentage points, and the capacity retention rate after cycling decreased by 14 percentage points.

[0054] The root of this significant difference lies in the fact that the atmospheric pressure injection method used in the comparative example cannot generate a breathing pump effect in the microporous structure of the electrode assembly, thus failing to form and continuously renew the repair medium microenvironment capable of electrochemical reactions at the electrode interface. Furthermore, the subsequent simple constant current cycle cannot drive the functional components in the repair medium to undergo directional electrochemical reactions at the electrode interface without the continuous application of a pressure field. In stark contrast, the repair cycle established in this invention, consisting of alternating pressure field intervention and electrochemical interface reconstruction, creates and renews the repair medium microenvironment through a pressure field, and then drives the first and second functional components to migrate directionally and undergo electrochemical reactions within this microenvironment through patterned electrical excitation. This achieves in-situ generation and densification of the solid electrolyte interface film, while simultaneously neutralizing acidic substances. It is this deep synergy between the physical and electrochemical fields in time and space that endows the technical solution of this invention with repair effects far exceeding those of existing simple superposition techniques.

[0055] It should be understood that the present invention also provides a non-disassembly in-situ repair system for lithium-ion battery electrolyte. This system is configured to perform the method described in any of the above embodiments. The system includes a pressure field generating device configured to be airtightly connected to the cell's electrolyte injection port for generating and maintaining a periodically alternating pressure field between a negative pressure state and a positive pressure state inside the cell; an electrical excitation generating device configured to be electrically connected to the cell's electrodes for generating and applying the aforementioned patterned electrical excitation; a multi-physical quantity sensing device, which includes at least a pressure sensor for sensing the internal pressure of the cell and an internal resistance detection unit for sensing the internal resistance of the cell, to acquire process parameters characterizing the cell's state in real time; and a controller electrically connected to the multi-physical quantity sensing device, the pressure field generating device, and the electrical excitation generating device, and configured to receive process parameters from the multi-physical quantity sensing device, and output control commands to the pressure field generating device and the electrical excitation generating device according to preset logic or a dynamic optimization algorithm to form closed-loop adaptive control.

[0056] In summary, this invention proposes a non-disassembly, in-situ repair method for lithium-ion batteries. This method involves alternating pressure field intervention and electrochemical interface reconstruction within the battery cell to form a repair cycle. A pressure field with periodic switching between negative and positive pressure states is established within the cell using a gas-tight coupling pressure generator. The repair medium, containing SEI film-forming functional components and acidic substance-capturing functional components, is deeply immersed into the electrode assembly using a breathing pump effect, forming and renewing the microenvironment of the repair medium at the electrode interface. Under the continuous action of the pressure field, a time-progressive, patterned electrical excitation is applied to the cell, sequentially executing a low-rate base cycle, a stepped charging with pulsed current, and partial state-of-charge rest relaxation. This drives the functional components to undergo directional electrochemical reactions, generating and densifying the SEI film in situ, while simultaneously neutralizing acidic substances. The system includes a pressure field generator, an electrical excitation generator, a multi-physical quantity sensing device, and a controller, forming a closed-loop adaptive control based on real-time monitored process parameters. After repair, the battery capacity recovery rate reaches 85% to 95%, and the cycle life reaches more than 80% of the initial level.

[0057] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for non-disassembly in-situ repair of lithium-ion batteries, characterized in that, Alternating pressure field intervention and electrochemical interface reconstruction are applied inside the battery cell to form a repair cycle, which includes: By using a pressure generating device that is airtightly coupled to the liquid injection port of the battery cell, a pressure field that periodically switches between negative and positive pressure states is established and maintained inside the battery cell. The breathing pumping effect generated by this pressure field in the microporous structure of the electrode assembly is used to draw in the repair medium and drive it to the depth of the electrode assembly, so as to form and renew the repair medium microenvironment that can supply chemical reactions at the electrode interface. Under the continuous action of the pressure field, a patterned electrical excitation is applied to the battery cell, causing the first and second functional components in the repair medium to undergo a directional electrochemical reaction at the electrode interface in the microenvironment maintained by the pressure field, so as to generate and densify the solid electrolyte interface film in situ, while neutralizing acidic substances. The repair medium comprises a first functional component with film-forming function and a second functional component with acid substance capture function; the patterned electrical excitation includes, in sequence, a low-rate base cycle, a stepped charge with pulsed current, and a rest relaxation in a partially charged state.

2. The method as described in claim 1, characterized in that, The gauge pressure of the pressure field in the negative pressure state is -90 kPa to -60 kPa, and the gauge pressure in the positive pressure state is 10 kPa to 30 kPa. The duration of a single pressure switching cycle is 3 to 8 minutes, and the pressure field continuously performs 5 to 15 switching cycles.

3. The method as described in claim 1, characterized in that, The repair medium is a liquid composition formulated under anhydrous conditions from the following components: 60wt%-85wt% matrix solvent, 10wt%-15wt% conductive lithium salt, 2wt%-8wt% first functional component, 1wt%-5wt% second functional component, and 0.5wt%-2wt% moisture scavenger.

4. The method as described in claim 3, characterized in that, The first functional component is at least one of fluoroethylene carbonate and vinylene carbonate; The second functional component is a silane compound containing trimethoxysilane or triethoxysilane, or a trifluoroacetamide compound containing silicon nitrogen.

5. The method as described in claim 1, characterized in that, In the standardized electrical excitation, the low-rate base cycle is performed 3 to 5 charge-discharge cycles with a constant current of 0.02C to 0.05C within a voltage range of 2.5V to 4.2V; the stepped charging with pulsed current charges the cell to 3.8V-4.0V with a constant current of 0.1C, then applies an alternating pulse current with a frequency of 0.5Hz-2Hz and a duty cycle of 30%-70% for 5 to 15 minutes, and then continues charging to 4.1V-4.25V with a constant current of 0.05C; the resting relaxation involves adjusting the cell's state of charge to 50%-70% and then resting for 24 to 48 hours.

6. The method as described in claim 1, characterized in that, When establishing and maintaining the pressure field, the internal pressure of the cell is sensed in real time to adjust the frequency, amplitude and amount of repair medium injection of the pressure switching in a closed loop; when applying the patterned electrical excitation, the internal resistance of the cell is sensed in real time, and the frequency or duty cycle of the pulse current is adjusted based on the rate of change of internal resistance, or the switching to the resting relaxation is triggered.

7. The method according to any one of claims 1 to 6, characterized in that, Before alternating the pressure field intervention and electrochemical interface reconstruction inside the cell, the cell is first identified and pre-conditioned. The identification involves screening cells with a capacity retention rate between 40% and 80% and an internal resistance increase of no more than 200%. The pre-conditioning involves discharging the selected cells with a small current to a cutoff voltage of 2.5V-3.0V and then letting them stand in an inert atmosphere and at a constant temperature for 12 to 24 hours to homogenize their internal electrochemical state.

8. A non-disassembly in-situ repair system for lithium-ion battery electrolyte, configured to implement the method according to any one of claims 1 to 7, the system comprising: The pressure field generating device is configured to be airtightly connected to the battery cell's liquid injection port, and is used to generate and maintain a pressure field that alternates periodically between a negative pressure state and a positive pressure state inside the battery cell. An electrical excitation generating device is configured to be electrically connected to the cell electrodes for generating and applying the patterned electrical excitation; A multi-physical quantity sensing device includes at least a pressure sensor for sensing the internal pressure of the battery cell and an internal resistance detection unit for sensing the internal resistance of the battery cell, so as to acquire process parameters characterizing the state of the battery cell in real time. The controller is electrically connected to the multi-physical quantity sensing device, the pressure field generating device, and the electrical excitation generating device, and is configured to receive the process parameters and output control commands to the pressure field generating device and the electrical excitation generating device according to preset logic or dynamic optimization algorithm to form closed-loop adaptive control.

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