A battery negative electrode interface passivation layer repairing method, a battery online repairing system and an energy storage system

Abstract

The present application relates to the technical field of battery repair, and particularly relates to a battery negative electrode interface passivation layer repair method, a battery online repair system and an energy storage system. The present application is based on the characteristics of the aged battery negative electrode interface passivation layer, i.e. the inner layer is relatively stable and the outer layer is loose and invalid. Firstly, under the condition of a lower SOC and a higher temperature, the outer layer component with poor stability in the aged interface passivation layer is preferentially weakened, dissolved, loosened or rearranged through discharging, so that the old film is selectively removed. Then, an asymmetric bidirectional pulse is applied, wherein the forward charging pulse is used to induce the formation of a new interface passivation layer, and the reverse discharging pulse is used to weaken the local excessive film formation and lithium ion enrichment, and cooperate with the standing process to promote the uniformization of the lithium ion concentration. Finally, a new interface passivation layer with uniformity, compactness and low impedance is reformed on the negative electrode surface, so that the interface impedance of the battery is significantly reduced, the capacity is recovered, and the cycle stability and safety of the battery are improved.

Description

Technical Field

[0001] This invention relates to the field of battery repair technology, and in particular to a method for repairing the passivation layer at the negative electrode interface of a battery, an online battery repair system, and an energy storage system. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and high operating voltage, have been widely used in new energy vehicles, electrochemical energy storage, and portable electronic devices. However, as battery service life increases and the number of cycles rises, the passivation layer on the negative electrode surface gradually ages and fails, becoming a significant cause of battery capacity decay, increased internal resistance, decreased rate performance, and deteriorated safety.

[0003] During the initial charge and discharge cycle of a lithium-ion battery, the electrolyte undergoes reduction and decomposition on the negative electrode surface, forming an interfacial passivation layer. This passivation layer typically consists of an inner layer rich in inorganic components and an outer layer rich in organic components. An ideal passivation layer should possess characteristics such as continuity, density, electronic insulation, and lithium-ion conductivity, thereby preventing continuous electrolyte decomposition and maintaining the stability of the negative electrode interface. However, under long-term cycling, high-rate charge and discharge, temperature fluctuations, or low-temperature conditions, the negative electrode interfacial passivation layer will continuously undergo cracking, thickening, localized detachment, and regeneration. Especially for graphite, silicon-oxygen, and silicon-carbon negative electrodes, changes in particle volume and uneven lithium-ion distribution during cycling further exacerbate the uneven cracking and regeneration of the interfacial passivation layer, causing its outer layer to gradually form a loose structure rich in organic lithium salts, low-stability carbonate decomposition products, and by-reaction products. The aforementioned aging interface passivation layer significantly increases lithium-ion migration resistance, induces local polarization and lithium deposition, and continuously consumes active lithium and electrolyte, resulting in rapid capacity decay, increased internal resistance, and in severe cases, even lithium plating and thermal runaway.

[0004] In existing technologies, the following methods are typically used to improve the stability of the negative electrode interface: (1) During the first formation stage of the battery, a more stable interface passivation layer is formed on the surface of the negative electrode by optimizing the electrolyte formulation, adding film-forming additives or increasing the proportion of fluorine-containing components; (2) Local overpotential and interface damage of the negative electrode are reduced by optimizing the formation process, reducing the charging rate, and using pulse charging; (3) After the battery degrades, the performance is restored by heating and recycling, replenishing lithium or replacing the electrolyte.

[0005] However, the above methods are mainly aimed at the initial formation of the passivation layer at the interface of new batteries, or can only slow down the continued deterioration of the passivation layer at the interface of aged batteries. For batteries that have undergone multiple cycles, it is difficult to effectively repair the already formed thick, loose, and high-resistivity aged passivation layer at the interface. On the one hand, most existing pulse charging methods use unidirectional charging pulses, which are mainly aimed at improving rate performance or suppressing lithium plating, without selectively treating the aging interface passivation layer that has formed on the negative electrode surface after cycling. Simply using unidirectional pulses or repeated charge and discharge is difficult to effectively remove the loose and failed outer components in the aging interface passivation layer, which can easily lead to the superposition of old and new interface passivation layers, further thickening the interface.

[0006] On the other hand, while existing methods such as temperature-heating recirculation or static resting can promote interface reformation to some extent, they often lack phased control over the repair process. They cannot preferentially remove failed components from the aged interface passivation layer, nor can they form a uniform and dense new interface passivation layer in subsequent processes. In addition, existing methods usually lack online determination of the repair endpoint, which can easily lead to under-repair or over-repair, resulting in a further increase in interface impedance or a decrease in battery performance.

[0007] Therefore, there is an urgent need to provide an in-situ electrochemical repair method for the negative electrode interface passivation layer of lithium-ion batteries after cycling, so as to effectively repair the negative electrode interface passivation layer, thereby reducing interface impedance, restoring capacity, and improving battery cycle stability and safety. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a method for repairing the passivation layer at the negative electrode interface of a battery, an online battery repair system, and an energy storage system. The method for repairing the passivation layer at the negative electrode interface provided by this invention can reform a uniform, dense, and low-resistance new interface passivation layer on the negative electrode surface, significantly reducing interface impedance, restoring capacity, and improving the battery's cycle stability and safety.

[0009] In a first aspect, the present invention provides a method for repairing the passivation layer at the negative electrode interface of a battery, the repair method comprising the following steps: (1) Adjust the battery to be repaired to a preset state of charge and place the battery at 40~70℃, and discharge it to a preset discharge termination state, so that the components with poor stability on the outer layer of the passivation layer of the aged negative electrode interface are weakened, dissolved, loosened or rearranged; wherein, the preset state of charge is 5~30% of the total battery capacity; (2) Applying an asymmetric bidirectional pulse to the battery to form a new interface passivation layer on the negative electrode surface; wherein, the process of applying the asymmetric bidirectional pulse includes performing a first repair stage and a second repair stage in sequence, the first repair stage includes an alternately applied first forward charging pulse and a first reverse discharging pulse, and the second repair stage includes an alternately applied second forward charging pulse and a second reverse discharging pulse; the first repair stage and the second repair stage constitute a repair cycle. Wherein, the current of the first forward charging pulse is greater than the current of the second forward charging pulse, and the duration of each first forward charging pulse is greater than the duration of each second forward charging pulse; the current of the first reverse discharging pulse is greater than the current of the second reverse discharging pulse, and the duration of each first reverse discharging pulse is greater than the duration of each second reverse discharging pulse. (3) Check whether the negative electrode interface impedance or coulomb efficiency meets the preset target conditions. If the preset target conditions are met, the repair is completed; if the preset target conditions are not met, repeat step (2) until the preset target conditions are met. The aging interface passivation layer refers to the interface passivation layer that becomes thicker, looser, and has increased impedance at the negative electrode interface after cycling.

[0010] The battery negative electrode interface passivation layer repair method provided by this invention first adjusts the battery to 5-30% SOC and discharges it at 40-70°C to preferentially weaken, dissolve, loosen, or rearrange the unstable outer layer components in the aged negative electrode interface passivation layer, thereby removing them while retaining a relatively stable inner layer structure. Then, an asymmetric bidirectional pulse is applied, including a first repair stage and a second repair stage. The first repair stage uses a larger forward charging pulse and a larger reverse discharging pulse (with a larger current and pulse duration) compared to the second repair stage to quickly restore the continuous interface passivation layer components on the negative electrode surface. The second repair stage uses a smaller forward charging pulse and a smaller reverse discharging pulse (with a smaller current and pulse duration) compared to the first repair stage to further improve the uniformity and density of the interface passivation layer. The forward charging pulse is used to induce the formation of a new interface passivation layer, and the reverse discharging pulse is used to weaken local over-film formation and lithium-ion enrichment. Simultaneously, the completion of the repair is determined based on impedance and coulombic efficiency. The battery negative electrode interface passivation layer repair method provided by the present invention can re-form a uniform, dense, and low-resistance new interface passivation layer on the negative electrode surface, significantly reducing interface impedance, restoring capacity, and improving the cycle stability and safety of the battery.

[0011] As a preferred technical solution of the present invention, the discharge method in step (1) is as follows: constant current discharge at a rate of 0.02~0.2 C (0.02 C, 0.05 C, 0.08 C, 0.1 C, 0.12 C, 0.15 C, 0.18 C, 0.2 C, etc.) and maintained for 10~180 min (e.g., 10 min, 20 min, 50 min, 80 min, 100 min, 150 min, 180 min, etc.). Alternatively, the discharge method described in step (1) is as follows: discharge at a constant current of 0.02~0.5 C (e.g., 0.02 C, 0.05 C, 0.1 C, 0.2 C, 0.3 C, 0.4 C, 0.5 C, etc.) until the preset discharge termination state is reached, and then maintain a constant voltage for 1~120 min (e.g., 1 min, 5 min, 10 min, 20 min, 40 min, 60 min, 80 min, 100 min, 120 min, etc.).

[0012] As a preferred embodiment of the present invention, the preset discharge termination state is a state of charge of 0 to 10% of the total battery capacity.

[0013] As a preferred embodiment of the present invention, the current of the first forward charging pulse is greater than the current of the first reverse discharging pulse.

[0014] As a preferred embodiment of the present invention, the duration of each first forward charging pulse is greater than the duration of each first reverse discharging pulse.

[0015] As a preferred embodiment of the present invention, the current of the second forward charging pulse is greater than the current of the second reverse discharging pulse.

[0016] As a preferred embodiment of the present invention, the duration of each second forward charging pulse is greater than the duration of each second reverse discharging pulse.

[0017] As a preferred embodiment of the present invention, the current of the first positive charging pulse is 0.2~0.5 C, such as 0.2 C, 0.3 C, 0.4 C, 0.5 C, etc.; the duration of each first positive charging pulse is 10~60 s, such as 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, etc.

[0018] As a preferred embodiment of the present invention, the current of the first reverse discharge pulse is 0.1 to 0.3 times the current of the first forward charging pulse, for example, 0.1 times, 0.2 times, 0.3 times, etc.; the duration of each first reverse discharge pulse is 0.5 to 5 s, for example, 0.5 s, 1 s, 2 s, 3 s, 4 s, 5 s, etc.

[0019] As a preferred embodiment of the present invention, the number of cycles in the first repair stage is 10-200 times, such as 10 times, 40 times, 60 times, 80 times, 100 times, 120 times, 140 times, 160 times, 180 times, 200 times, etc.

[0020] As a preferred embodiment of the present invention, the current of the second positive charging pulse is 0.05~0.2 C, such as 0.05 C, 0.1 C, 0.15 C, 0.2 C, etc.; the duration of each second positive charging pulse is 2~20 s, such as 2s, 5s, 10s, 15s, 20s, etc.

[0021] As a preferred embodiment of the present invention, the current of the second reverse discharge pulse is 0.05 to 0.2 times the current of the second forward charging pulse, for example, 0.05 times, 0.1 times, 0.2 times, etc.; the duration of each second reverse discharge pulse is 0.1 to 2 s, for example, 0.1 s, 0.5 s, 1 s, 1.5 s, 2 s, etc.

[0022] As a preferred embodiment of the present invention, the number of cycles in the second repair stage is 20-300 times, such as 20 times, 40 times, 60 times, 80 times, 100 times, 120 times, 140 times, 160 times, 180 times, 200 times, 220 times, 240 times, 260 times, 280 times, 300 times, etc.

[0023] As a preferred embodiment of the present invention, after every 1 to 50 alternating first forward charging pulses and first reverse discharging pulses, the battery is left to stand for 10 to 300 seconds.

[0024] As a preferred embodiment of the present invention, after every 1 to 50 alternating second forward charging pulses and second reverse discharging pulses, the battery is left to stand for 10 to 300 seconds.

[0025] The present invention involves a resting period between pulses to promote uniformity of lithium ion concentration.

[0026] Based on the characteristic of "relatively stable inner layer and loose and failed outer layer" of the passivation layer at the negative electrode interface after cycling, this invention firstly, under low SOC and high temperature conditions, discharge causes the outer layer components with poor stability in the aged interface passivation layer to be preferentially weakened, dissolved, loosened, or rearranged, thereby achieving selective removal of the old film. Subsequently, an asymmetric bidirectional pulse is applied, in which the forward charging pulse is used to induce the formation of a new interface passivation layer, and the reverse discharge pulse is used to weaken local over-film formation and lithium ion enrichment. Combined with the resting process, it promotes the homogenization of lithium ion concentration, and finally a uniform, dense, and low-resistance new interface passivation layer is formed on the negative electrode surface.

[0027] As a preferred technical solution of the present invention, the repair is completed when any of the following preset target conditions are met in step (3): (A) The impedance of the interface passivation layer or the charge transfer impedance decreased by 10-50% compared to before repair; (B) The rate of change in impedance over two consecutive repair cycles is less than 5%; (C) Coulomb efficiency recovered to over 95%.

[0028] Among them, (B) two consecutive repair cycles means that after the completion of one repair cycle in step (2), the battery impedance is detected, and then the battery impedance is detected again after the completion of one repair cycle in step (2), and the impedance change rate of the two detection results is less than 5%.

[0029] (C) The coulombic efficiency is restored to more than 95% means that after step (2) is completed, the battery undergoes one charge-discharge cycle and the coulombic efficiency is calculated to be restored to more than 95%.

[0030] As a preferred embodiment of the present invention, the battery to be repaired is a battery with a capacity decay of 70-95% and an impedance increase of 10-100%.

[0031] As a preferred embodiment of the present invention, the battery to be repaired includes lithium-ion batteries to be repaired, such as lithium iron phosphate|graphite batteries, lithium iron phosphate|silicon-oxygen composite negative electrode batteries, lithium iron phosphate|silicon-carbon negative electrode batteries, ternary material|graphite batteries, etc.

[0032] In a second aspect, the present invention provides an online battery repair system for performing the repair method described in the first aspect, the online battery repair system comprising a temperature control module, a SOC adjustment module, a pulse control module, and an online detection module; The temperature control module is used to heat the battery to be repaired to 40~70℃; The SOC adjustment module is used to adjust the battery to be repaired to a preset state of charge and discharge it to a preset discharge termination state. The pulse control module is used to apply asymmetric bidirectional pulses to the battery to be repaired; The online detection module is used to detect the battery negative electrode interface impedance or coulombic efficiency data, and automatically terminates the repair process when the preset target conditions are met.

[0033] As a preferred embodiment of the present invention, the online detection module is configured to automatically execute the repair method described in the first aspect when it detects that the battery capacity has decreased by 70-95% and the impedance has increased by 10-100%.

[0034] Thirdly, the present invention provides an energy storage system including at least one of the battery online repair systems described in the second aspect.

[0035] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art: 1. The repair method provided by the present invention is not simply to recharge and discharge the battery after cycling. Instead, it first discharges to a preset discharge termination state and uses a higher negative electrode potential to selectively weaken, dissolve, crack, or rearrange the loose, high-resistance, and unstable outer layer components in the passivation layer of the aged interface, thereby avoiding further thickening caused by the simple superposition of the old and new passivation layers.

[0036] 2. This invention uses asymmetric bidirectional pulses to rebuild a new interface passivation layer, wherein the forward charging pulse is used to induce the formation of a new interface passivation layer, and the reverse discharge pulse is used to release local overpotential, weaken local excessive film formation and lithium ion enrichment, thereby achieving uniform repair of the interface passivation layer on the negative electrode surface.

[0037] 3. The asymmetric bidirectional pulse of the present invention includes a first repair stage and a second repair stage. The first repair stage rapidly restores the continuous interface, and the second repair stage further improves the uniformity and density of the interface passivation layer, which can effectively reduce interface impedance, improve lithium-ion transport, and improve the capacity retention and rate performance of the battery after cycling.

[0038] 4. The repair method of this invention introduces an online stop mechanism, which automatically terminates the repair process based on the recovery of impedance and coulomb efficiency, thereby avoiding insufficient or excessive repair and improving the applicability and engineering feasibility of the method. Detailed Implementation

[0039] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0040] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0041] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0042] The lithium-ion batteries used in the embodiments of this invention are all batteries that have undergone cycle aging, wherein: the rated capacity of the lithium iron phosphate|graphite battery is 280 Ah; the rated capacity of the lithium iron phosphate|silicon-oxygen composite negative electrode battery is 50 Ah; and the rated capacity of the ternary material|graphite battery is 20 Ah. All aged batteries have undergone charge-discharge cycles at 25°C and 0.5 C for 300-800 cycles, with the capacity retention rate decreasing to 80-90%, and the battery impedance increasing by 15-50% compared to the initial state.

[0043] Example 1 This embodiment provides a method for repairing the passivation layer at the negative electrode interface of a battery and an online battery repair system. The online battery repair system is used to perform the method for repairing the passivation layer at the negative electrode interface of a battery. The online battery repair system includes a temperature control module, a SOC adjustment module, a pulse control module, and an online detection module. The temperature control module is used to heat the battery to be repaired to 40~70℃; The SOC adjustment module is used to adjust the battery to be repaired to a preset state of charge and discharge it to a preset discharge termination state. The pulse control module is used to apply asymmetric bidirectional pulses to the battery to be repaired; The online detection module is used to detect the negative electrode interface impedance or coulombic efficiency data of the battery, and automatically terminates the repair process when the preset target conditions are met.

[0044] The battery to be repaired is a lithium iron phosphate / graphite battery that has undergone 500 cycles. The repair method includes the following steps: (1) The SOC adjustment module adjusts the battery SOC to 20%, the temperature control module heats the battery to 50°C, and then the SOC adjustment module discharges the battery at a constant current of 0.1 C to the preset discharge termination state (the state of charge is 5% of the total battery capacity) and then holds it at a constant voltage for 30 min, so that the components with poor stability in the outer layer of the passivation layer of the aged negative electrode interface are weakened, dissolved, loosened or rearranged, thereby removing them and retaining a relatively stable inner layer structure. (2) The pulse control module applies an asymmetric bidirectional pulse to the battery to form a new interface passivation layer on the negative electrode surface. The process of applying the asymmetric bidirectional pulse includes a first repair stage and a second repair stage performed sequentially. First repair phase: Forward charging pulse: current 0.3 C, each pulse lasts 30 s; Reverse discharge pulse: current 0.06 C, each pulse lasts 2 s; rest for 60 s after every 10 pulses; a total of 50 pulse cycles are performed.

[0045] Second repair phase: Forward charging pulse: current 0.1 C, each pulse lasts 10 s; Reverse discharge pulse: current 0.01 C, each pulse lasts 0.5 s; after every 20 pulses, rest for 120 s; a total of 100 pulse cycles are performed, which constitutes one repair cycle.

[0046] (3) The online detection module detects that the negative electrode interface impedance and charge transfer impedance of the battery reach the preset target conditions, and the repair is completed.

[0047] Example 2 This embodiment provides a method for repairing the passivation layer at the negative electrode interface of a battery and an online battery repair system. The online battery repair system is the same as that in Embodiment 1. The difference from Embodiment 1 is that in this embodiment, the battery to be repaired is a lithium iron phosphate|silicon-oxygen composite negative electrode battery after 800 cycles. The repair method includes the following steps: (1) The SOC adjustment module adjusts the battery SOC to 15%, the temperature control module heats the battery to 60°C, and then the SOC adjustment module discharges the battery at a constant current of 0.05 C and maintains it for 60 min, so that the components with poor stability in the outer layer of the passivation layer of the aged negative electrode interface are weakened, dissolved, loosened or rearranged, thereby removing them and retaining the relatively stable inner layer structure. (2) The pulse control module applies an asymmetric bidirectional pulse to the battery to form a new interface passivation layer on the negative electrode surface. The process of applying the asymmetric bidirectional pulse includes a first repair stage and a second repair stage performed sequentially. First repair phase: Forward charging pulse: current 0.4 C, each pulse lasts 20 s; Reverse discharge pulse: current 0.08 C, each pulse lasts 1 s; rest for 30 s after every 5 pulses; a total of 80 pulse cycles are performed.

[0048] Second repair phase: Forward charging pulse: current 0.15 C, each pulse lasts 5 s; Reverse discharge pulse: current 0.015 C, each pulse lasts 0.2 s; rest for 60 s after every 10 pulses; a total of 150 pulse cycles are performed.

[0049] (3) The online detection module detects that the negative electrode interface impedance and charge transfer impedance of the battery reach the preset target conditions, and the repair is completed.

[0050] Example 3 This embodiment provides a method for repairing the passivation layer at the negative electrode interface of a battery and an online battery repair system. The online battery repair system is the same as that in Embodiment 1. The difference from Embodiment 1 is that in this embodiment, the battery to be repaired is a ternary material / graphite battery after 300 cycles. The repair method includes the following steps: (1) The SOC adjustment module adjusts the battery SOC to 30%, the temperature control module heats the battery to 45°C, and then the SOC adjustment module discharges the battery at a constant current of 0.2 C to the preset discharge termination state (the state of charge is 10% of the total battery capacity) and then holds it at a constant voltage for 10 min, so that the components with poor stability in the outer layer of the passivation layer of the aged negative electrode interface are weakened, dissolved, loosened or rearranged, thereby removing them and retaining the relatively stable inner layer structure. (2) The pulse control module applies an asymmetric bidirectional pulse to the battery to form a new interface passivation layer on the negative electrode surface. The process of applying the asymmetric bidirectional pulse includes a first repair stage and a second repair stage performed sequentially. First repair stage: Forward charging pulse: current 0.25 C, each pulse lasts 15 s; Reverse discharge pulse: current 0.05 C, each pulse lasts 1 s; after every 15 pulses, rest for 30 s; a total of 40 pulse cycles are performed.

[0051] Second repair phase: Forward charging pulse: current 0.08 C, each pulse lasts 5 s; Reverse discharge pulse: current 0.008 C, each pulse lasts 0.2 s; rest for 60 s after every 20 pulses; a total of 80 pulse cycles are performed.

[0052] (3) The online detection module detects that the negative electrode interface impedance and charge transfer impedance of the battery reach the preset target conditions, and the repair is completed.

[0053] Comparative Example 1 This comparative example provides a method for repairing the passivation layer of the negative electrode interface of a battery. The repair method is the same as that in Example 1. The difference between Example 1 and Example 1 is that step (1) is omitted in this comparative example. Instead, the battery online repair system is used to directly apply an asymmetric bidirectional pulse to the battery in step (2). In step (3), the online detection module detects whether the impedance of the negative electrode interface and the charge transfer impedance of the battery reach the preset target conditions.

[0054] Comparative Example 2 This comparative example provides a method for repairing the passivation layer of the negative electrode interface of a battery. The repair method is the same as that in Example 1. The difference between this comparative example and Example 1 is that step (2) is omitted, and only the battery online repair system is used to perform step (1). In step (3), the online detection module detects whether the battery negative electrode interface impedance and charge transfer impedance have reached the preset target conditions.

[0055] Comparative Example 3 This comparative example provides a method for repairing the passivation layer of the negative electrode interface of a battery. The repair method is the same as that in Example 1. The difference between Example 1 and Example 1 is that in this comparative example, step (2) is repaired by traditional unidirectional pulse charging with a pulse current of 0.3C, each pulse lasts for 30 seconds, and is left to stand for 60 seconds after every 10 pulses. In step (3), the online detection module detects whether the impedance of the negative electrode interface and the charge transfer impedance of the battery reach the preset target conditions.

[0056] Comparative Example 4 This comparative example provides a method for repairing the passivation layer of the negative electrode interface of a battery. The repair method is the same as that in Example 1. The difference between Example 1 and Example 1 is that in this comparative example, step (2) only performs the first repair stage and omits the second repair stage. In step (3), the online detection module detects whether the impedance of the negative electrode interface and the charge transfer impedance of the battery reach the preset target conditions.

[0057] Comparative Example 5 This comparative example provides a method for repairing the passivation layer of the negative electrode interface of a battery. The repair method is the same as that in Example 1. The difference between Example 1 and Example 1 is that in this comparative example, step (2) omits the first repair stage and only performs the second repair stage. In step (3), the online detection module detects whether the impedance of the negative electrode interface and the charge transfer impedance of the battery reach the preset target conditions.

[0058] Comparative Example 6 This comparative example provides a method for repairing the passivation layer of the negative electrode interface of a battery. The repair method is the same as that in Example 1. The difference from Example 1 is that step (2) in this comparative example adopts symmetrical bidirectional pulse repair, wherein the current of the forward charging pulse and the reverse discharging pulse is 0.3C, and the duration of each pulse is 30 s; after every 10 pulses, it is left to stand for 60 s; a total of 50 pulse cycles are performed. In step (3), the online detection module detects whether the impedance of the negative electrode interface and the charge transfer impedance of the battery reach the preset target conditions.

[0059] In Examples 1-3 and Comparative Examples 1-6, the online detection module performs AC impedance tests on the batteries before and after repair. The test methods include: After being left to stand at 25°C for 2 hours, the battery was tested at 50% SOC, with a frequency range of 100 kHz to 10 mHz and an AC disturbance amplitude of 5 mV. The interface passivation layer impedance R was obtained using equivalent circuit fitting. SEI and charge transfer impedance R ct The test results are shown in Table 1: Table 1

[0060] As can be seen from Table 1, the repair methods provided in the embodiments of the present invention can significantly reduce the impedance of the interface passivation layer and the charge transfer impedance. Among them, Example 2 shows the most significant improvement to the silicon-oxygen composite negative electrode battery. However, Comparative Examples 1 to 6 have significantly smaller impedance reductions due to the lack of step (1) selective removal of the old film, asymmetric bidirectional pulse, or the first and second repair stages.

[0061] Performance testing 1. Capacity recovery and rate performance testing: The repaired batteries from Examples 1-3 and Comparative Examples 1-6 were subjected to a 0.5 C charge-discharge test at 25°C, and the discharge capacity was recorded. Subsequently, rate performance tests were conducted at 0.5 C, 1 C, and 2 C rates, respectively. The capacity recovery rate was calculated based on the battery capacity before repair, and the results are shown in Table 2.

[0062] Capacity increase rate = (Capacity after repair - Capacity before repair) / Capacity before repair × 100%.

[0063] Table 2

[0064] As can be seen from Table 2, the repair method provided by the embodiments of the present invention can not only restore capacity, but also significantly improve the capacity retention capability at high rates, indicating that the passivation layer of the battery interface after repair is more uniform and dense, and lithium-ion transport is faster.

[0065] 2. Cyclic Stability Test: The repaired batteries of Examples 1-3 and Comparative Examples 1-6 were subjected to 200 charge-discharge cycles at 25°C and 1C, and the capacity retention rate was recorded. The capacity retention rate was calculated based on the initial cycle discharge capacity after repair. The test results are shown in Table 3. Table 3

[0066] As can be seen from Table 3, the new interface passivation layer formed by the repair method provided by the present invention has better long-term stability and is not easy to thicken and fail again during subsequent cycles. Therefore, the capacity retention rate is significantly better than that of the comparative example.

[0067] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0068] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for repairing the passivation layer at the negative electrode interface of a battery, characterized in that, The repair method includes the following steps: (1) Adjust the battery to be repaired to a preset state of charge and place the battery at 40~70℃, and discharge it to a preset discharge termination state; wherein, the preset state of charge is 5~30% of the total battery capacity; (2) Applying an asymmetric bidirectional pulse to the battery; the process of applying the asymmetric bidirectional pulse includes performing a first repair stage and a second repair stage in sequence; the first repair stage includes an alternately applied first forward charging pulse and a first reverse discharging pulse, and the second repair stage includes an alternately applied second forward charging pulse and a second reverse discharging pulse; Wherein, the current of the first forward charging pulse is greater than the current of the second forward charging pulse, and the duration of each first forward charging pulse is greater than the duration of each second forward charging pulse; the current of the first reverse discharging pulse is greater than the current of the second reverse discharging pulse, and the duration of each first reverse discharging pulse is greater than the duration of each second reverse discharging pulse. (3) Check whether the negative electrode interface impedance or coulomb efficiency meets the preset target conditions. If the preset target conditions are met, the repair is completed; if the preset target conditions are not met, repeat step (2) until the preset target conditions are met.

2. The repair method according to claim 1, characterized in that, Step (1) satisfies one or both of the following 1) to 2): 1) The discharge method described in step (1) is: constant current discharge at a rate of 0.02~0.2 C and maintained for 10~180 min; Alternatively, the discharge method described in step (1) is: discharge at a constant current of 0.02~0.5 C until the preset discharge termination state, and then maintain a constant voltage for 1~120 min; 2) The preset discharge termination state is a state of charge of 0 to 10% of the total battery capacity.

3. The repair method according to claim 1, characterized in that, The repair method satisfies one or more of the following 1) to 4): 1) The current of the first forward charging pulse is greater than the current of the first reverse discharging pulse; 2) The duration of each first forward charging pulse is greater than the duration of each first reverse discharging pulse; 3) The current of the second forward charging pulse is greater than the current of the second reverse discharging pulse; 4) The duration of each second positive charging pulse is greater than the duration of each second reverse discharging pulse.

4. The repair method according to any one of claims 1 to 3, characterized in that, The current of the first positive charging pulse is 0.2~0.5 C, and the duration of each first positive charging pulse is 10~60 s; And / or, the current of the first reverse discharge pulse is 0.1 to 0.3 times the current of the first forward charging pulse, and the duration of each first reverse discharge pulse is 0.5 to 5 seconds; And / or, the number of cycles in the first repair phase is 10-200; And / or, the current of the second positive charging pulse is 0.05~0.2 C, and the duration of each second positive charging pulse is 2~20 s; And / or, the current of the second reverse discharge pulse is 0.05 to 0.2 times the current of the second forward charging pulse, and the duration of each second reverse discharge pulse is 0.1 to 2 s; And / or, the second repair phase is repeated 20-300 times.

5. The repair method according to any one of claims 1 to 3, characterized in that, After every 1 to 50 alternating first forward charging pulses and first reverse discharging pulses, allow the battery to rest for 10 to 300 seconds. And / or, after every 1 to 50 alternating second positive charging pulses and second reverse discharging pulses, allow the battery to rest for 10 to 300 seconds.

6. The repair method according to any one of claims 1 to 3, characterized in that, The repair is complete when any of the following preset target conditions are met in step (3): (A) The impedance of the interface passivation layer or the charge transfer impedance decreased by 10-50% compared to before repair; (B) The rate of change in impedance over two consecutive repair cycles is less than 5%; (C) Coulomb efficiency recovered to over 95%.

7. The repair method according to any one of claims 1 to 3, characterized in that, The battery to be repaired is one with a capacity decay of 70-95% and an impedance increase of 10-100%.

8. A battery online repair system, characterized in that, The battery online repair system, used to perform the repair method according to any one of claims 1 to 7, includes a temperature control module, a SOC adjustment module, a pulse control module, and an online detection module; The temperature control module is used to heat the battery to be repaired to 40~70℃; The SOC adjustment module is used to adjust the battery to be repaired to a preset state of charge and discharge it to a preset discharge termination state. The pulse control module is used to apply asymmetric bidirectional pulses to the battery to be repaired; The online detection module is used to detect the battery negative electrode interface impedance or coulombic efficiency data, and automatically terminates the repair process when the preset target conditions are met.

9. The battery online repair system according to claim 8, characterized in that, The online detection module is configured to automatically execute the repair method described in any one of claims 1 to 7 when it detects that the battery capacity has decreased by 70-95% and the impedance has increased by 10-100%.

10. An energy storage system, characterized in that, It includes at least one battery online repair system as described in claim 8 or 9.

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