Method for restoring lithium-ion battery capacity

Abstract

The present invention belongs to the field of batteries, and specifically relates to a method for restoring lithium-ion battery capacity, comprising step a and step b; step a: over-discharging a lithium-ion battery to be restored, discharging gas from an inner cavity of the lithium-ion battery, and injecting an electrolyte into the inner cavity; and step b: using a lithium replenishment electrode to replenish lithium in the electrodes of the lithium-ion battery to be restored. In the present invention, a lithium-ion battery prior to scrapping treatment is restored and regenerated, combining over-discharging and lithium replenishment without damaging the electrode assembly; the charge and discharge cycle performance of waste lithium-ion batteries is prolonged and the pressure of waste lithium-ion batteries on the environment is reduced, and battery use costs are lowered.

Description

Lithium ion battery capacity repair method TECHNICAL FIELD

[0001] The application belongs to the field of batteries, and particularly relates to a lithium ion battery capacity repair method. BACKGROUND

[0002] A lithium ion battery is a kind of secondary battery, which mainly works by moving lithium ions between the positive electrode and the negative electrode. + The lithium ions are embedded and de-embedded between the two electrodes. + When charging, the lithium ions are de-embedded from the positive electrode, embedded into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; when discharging, the process is reversed.

[0003] With the popularization and application of the lithium ion battery, the lithium ion battery will cause environmental problems. If the lithium ion battery can be repaired to improve its capacity and be used again, the environmental burden can be reduced and the cost can be saved. SUMMARY

[0004] The application aims to provide a lithium ion battery capacity repair method to prolong the charge-discharge cycle performance of the lithium ion battery, reduce the pressure on the environment caused by waste lithium ion batteries, and reduce the use cost of the battery.

[0005] The lithium ion battery capacity repair method provided in the first aspect of the application has the special feature that it comprises steps a and b.

[0006] In step a, the lithium ion battery to be repaired is over-discharged, the gas in the inner cavity of the lithium ion battery is discharged, and electrolyte is injected into the inner cavity.

[0007] In step b, a lithium supplement electrode is used to supplement lithium to the electrode of the lithium ion battery to be repaired.

[0008] The application repairs and regenerates the lithium ion battery before it is scrapped (the lithium ion battery is a battery whose capacity is reduced to less than 90% of the nominal capacity), combines over-discharge and lithium supplement without damaging the electrode assembly, does not specifically limit the sequence of over-discharge and lithium supplement, and usually performs over-discharge first and then performs lithium supplement, or performs over-discharge and lithium supplement simultaneously. Through over-discharge, part or all of the thickened SEI film of the negative electrode is removed in situ, and after over-discharge, the gas is discharged to reduce the pressure in the inner cavity of the battery, and then new electrolyte is injected to re-form a stable SEI film on the surface of the negative electrode during small-current charge and discharge. Through lithium supplement, the electrode assembly is supplemented with lithium, the active lithium lost during the battery cycle is supplemented, and the performance of the battery is reactivated.

[0009] To further improve the repair effect, the execution order of step a and step b can be optimized, and the lithium supplement parameters can also be optimized, including the lithium supplement time and the lithium supplement current.

[0010] The present application preferably performs step a first and then step b, that is, over-discharge is performed first and then lithium supplement is performed.

[0011] The lithium supplement current can be determined according to the battery capacity. C is a constant between 20 and 200, and the larger the capacity, the larger the constant C value.

[0012] In another preferred embodiment of the present application, step a and step b can be started simultaneously, and step b is continuously performed for a set time after step a is completed, that is, over-discharge and lithium supplement are started simultaneously, and lithium supplement is continuously performed for a set time after over-discharge is completed, which can also achieve good repair effect.

[0013] Further, in step b, the lithium supplement region of the lithium supplement electrode is arranged in the lithium ion battery shell, and the wiring terminal of the lithium supplement electrode is arranged outside the lithium ion battery shell.

[0014] The present application can control the communication between the lithium supplement electrode and the polarity terminal of the lithium ion battery, and controllably supplement lithium to the lithium ion battery according to the repair requirement.

[0015] Further, the lithium supplement electrode is arranged between the electrode assembly and the bottom plate, so that the lithium supplement electrode is parallel to the end surface of the electrode assembly, and the distance between each circle of electrode sheets of the electrode assembly and the lithium supplement electrode is the same, so that each circle of electrode sheets can be quickly and uniformly embedded with lithium when the lithium supplement electrode supplements lithium to the electrode assembly.

[0016] Further, the wiring terminal of the lithium supplement electrode is electrically connected to the polarity terminal of the lithium ion battery through a switch, a variable resistor and a diode. The resistance value of the variable resistor is adjusted to control the discharge current, so that precise and controllable lithium supplement can be achieved, and lithium precipitation phenomenon of the negative electrode due to excessive lithiumization can be prevented. The diode enables one-way conduction of the lithium supplement current and blocks the lithium embedding process of the lithium supplement electrode during the charging and discharging process.

[0017] Further, the lithium supplementing electrode is a lithium sheet or other lithium-rich material.

[0018] Further, the lithium-rich material is a lithium-rich negative electrode sheet.

[0019] The second aspect of the present application provides a lithium ion battery capacity repair method, which is characterized in that the method mainly comprises the following steps:

[0020] performing a discharging step on the old lithium ion battery; performing a heating step on the old lithium ion battery.

[0021] The present application promotes the decomposition of the SEI layer on the surface of the negative electrode sheet of the battery to a certain extent through the discharging operation, reduces the thickness of the SEI layer, facilitates the composition and structure of the SEI layer in the subsequent step, and activates the "dead lithium" in the negative electrode of the battery, so that the lithium participates in the subsequent charging and discharging cycle.

[0022] By heating the old lithium ion battery, the crystal structure of the positive and negative electrode materials of the battery changes, thereby restoring the original structure of the battery, and further maintaining the capacity of the battery.

[0023] Further, since gas is generated during discharging, in order to avoid the problem that the battery is inflated after the gas generation amount is too large, affecting the performance of the battery, or even the battery shell is torn and leaks, the above method further comprises an exhaust step.

[0024] The exhaust step can be performed at the following times:

[0025] 1. The exhaust is performed simultaneously with the discharging;

[0026] 2. The exhaust is performed after the discharging, and the heating step is finally performed;

[0027] 3. The exhaust step is finally performed after the discharging and heating steps.

[0028] Further, the above method further comprises a liquid supplementing step.

[0029] The liquid supplementing step can be performed at the following times:

[0030] 1. The liquid supplementing step is performed after the discharging step is completed;

[0031] 2. The liquid supplementing step is performed after the discharging and heating steps are completed;

[0032] The liquid supplementing step can solve the problem of poor conductivity caused by insufficient electrolyte content in the old battery to be repaired, and the exhaust step is also performed during the liquid supplementing step, which can avoid the problem that the battery is inflated after the gas generation amount is too large during the discharging, affecting the performance of the battery, or even the battery shell is torn and leaks.

[0033] Further, the electrolyte formula injected in the above liquid supplementing step is: solvent, lithium salt, fluorinated ether and 1,3 benzene ethyldinitrile; the solvent is a mixed solution of ethylene carbonate and ethyl methyl carbonate, and the lithium salt is lithium bisfluorosulfonylimide.

[0034] Further, the above method further comprises a clamping step performed on the screened old lithium ion battery.

[0035] Further, the discharge cutoff voltage range is 0.01V to 2.4V.

[0036] Further, the discharge cutoff voltage is 0.01V.

[0037] Further, the heating temperature range is 40 to 60℃.

[0038] Further, the heating temperature is 50℃.

[0039] The lithium ion battery capacity repair method provided by the third aspect of the application has the speciality that the lithium ion battery is a large-capacity battery, and the large-capacity battery is detected in real time, and the large-capacity battery with capacity attenuation is repaired online.

[0040] Specifically, the application provides the following five online repair methods for large-capacity batteries:

[0041] The specific steps of method one are as follows:

[0042] Step 1: Real-time detection of large-capacity batteries, if the large-capacity battery is detected to be attenuated to X or has been executed Y times of charge-discharge cycles, at least once step 2 is executed; 85%≤X≤98%; Y≥200 times;

[0043] Step 2: Repair process;

[0044] Step a: Perform liquid supplementing or liquid replacing on the large-capacity battery through a functional interface, and utilize the functional interface to exhaust the large-capacity battery;

[0045] Step b: Supplement lithium to the large-capacity battery through a lithium supplementing device.

[0046] The application utilizes the structural characteristics of large-capacity batteries, and utilizes the functional interface to realize online liquid supplementing and exhaust of large-capacity batteries, not only makes up for the consumption of electrolyte in the large-capacity battery, improves the conductivity of lithium ions, but also exhausts the large-capacity battery, not only reduces the influence of excessive gas pressure on the performance of the large-capacity battery, but also makes the liquid supplementing process more smooth;

[0047] And, the lithium supplement device is used to supplement lithium in the large capacity battery online, which can improve the content of active lithium ions in the large capacity battery, and then improve the cycle performance of the large capacity battery from the aspects of improving the conductivity of lithium ions, reducing the gas pressure, improving the active lithium ions and the like, and complete the online repair of the large capacity battery. The process can be a first a and then b, or a first b and then a.

[0048] Alternatively, the functional interface is used to realize the liquid replacement and exhaust of the large capacity battery online, which not only makes up for the consumption of the electrolyte in the large capacity battery and improves the conductivity of lithium ions, but also exhausts the large capacity battery, which not only reduces the influence of excessive gas pressure on the performance of the large capacity battery, but also makes the liquid replacement process more smooth, and at the same time, the liquid replacement process can take away the impurities in the old electrolyte, and realize the purification of the electrolyte.

[0049] And, the lithium supplement device is used to supplement lithium in the large capacity battery online, which can improve the content of active lithium ions in the large capacity battery, and then improve the cycle performance of the large capacity battery from the aspects of improving the conductivity of lithium ions, reducing the gas pressure, improving the active lithium ions and the like, and complete the online repair of the large capacity battery.

[0050] Further, since the long-term operation of the large capacity battery will cause the SEI film to thicken, the SEI film that is too thick will cause the ion impedance to continuously increase, and the active lithium ions will continuously decrease, therefore, in order to solve the problem, the above step 2 further includes a step c: performing over-discharge treatment on the large capacity battery. The over-discharge treatment can reduce the thickness of the SEI film, activate the dead lithium in the large capacity battery, and reduce the ion impedance.

[0051] Further, in order to improve the repair effect of the large capacity battery after over-discharge, the above method further includes a step d: performing heating treatment on the large capacity battery through the heat transfer pipe on the polarity terminal of the large capacity battery. The heat transfer pipe of the present application transmits heat to each single battery in the large capacity battery, and the positive and negative electrode materials in each single battery change the crystal structure after being heated to restore the original structure, so that the active lithium ions can be smoothly embedded or removed from the positive and negative electrodes in the charging and discharging process, and then the cycle performance of the large capacity battery can be further improved.

[0052] The specific steps of the second method are as follows:

[0053] Step 1: Real-time detection of the large capacity battery, if the capacity of the large capacity battery is detected to be attenuated to X or the over-discharge treatment is performed for more than Y times, at least step 2 is performed once; 70%≤X≤98%; Y≥200 times;

[0054] Step 2: Repair process;

[0055] Step a: perform liquid supplement or replacement for the large capacity battery through the functional interface, and perform exhaust for the large capacity battery through the functional interface;

[0056] Step b: perform over-discharge treatment for the large capacity battery.

[0057] The present application utilizes the structural features of the large capacity battery, and the liquid supplement and exhaust for the large capacity battery can be realized online through the functional interface, which makes up for the consumption of electrolyte in the large capacity battery, improves the conductivity of lithium ions, performs exhaust for the large capacity battery, reduces the influence of excessive gas pressure on the performance of the large capacity battery, and makes the liquid supplement process smoother.

[0058] Since the long-term operation of the large capacity battery will cause the SEI film in each single battery to thicken, the over-thick SEI film will cause ion impedance to continuously increase, and the active lithium ions will continuously decrease, so as to solve the problem, the present application performs over-discharge treatment for the large capacity battery. The over-discharge treatment will reduce the thickness of the SEI film, activate the dead lithium in the large capacity battery, reduce the ion impedance, and then improve the cycle performance of the large capacity battery from the aspects of improving the conductivity of lithium ions, reducing the gas pressure, activating the dead lithium, and reducing the ion impedance, and complete the online repair of the large capacity battery.

[0059] Alternatively, the liquid replacement and exhaust for the large capacity battery can be realized online through the functional interface, which makes up for the consumption of electrolyte in the large capacity battery, improves the conductivity of lithium ions, performs exhaust for the large capacity battery, reduces the influence of excessive gas pressure on the performance of the large capacity battery, and makes the liquid replacement process smoother. At the same time, the liquid replacement process will take away the impurities in the old electrolyte, realize the purification of the electrolyte, and then improve the cycle performance of the large capacity battery from the aspects of improving the conductivity of lithium ions, reducing the gas pressure, activating the dead lithium, reducing the ion impedance, and purifying the electrolyte, and complete the online repair of the large capacity battery.

[0060] Further, in order to improve the repair effect of the large capacity battery after over-discharge, the above method further includes step c: performing heating treatment for the large capacity battery through the heat transfer pipe on the polarity terminal of the large capacity battery. The present application transmits heat to each single battery in the large capacity battery through the heat transfer pipe, the lattice structure of the positive and negative electrode materials in each single battery changes after being heated, thereby restoring the original structure, so that the active lithium ions can be smoothly embedded or extracted in the positive and negative electrodes during the charging and discharging process, and then the cycle performance of the large capacity battery can be further improved.

[0061] The specific steps of method three are as follows:

[0062] Step 1: real-time detect the large capacity battery, if the capacity of the large capacity battery is detected to be attenuated to X or the over-discharge is performed for more than Y times, at least one step 2 is performed; 70%≤X≤98%; Y≥200 times;

[0063] Step 2: repair process;

[0064] Step a: over-discharge the large capacity battery;

[0065] Step b: supplement lithium to the large capacity battery through a lithium supplement device;

[0066] Step c: exhaust the large capacity battery through a functional interface.

[0067] As the long-term operation of the large capacity battery can cause the SEI film to thicken, the SEI film that is too thick can cause the ion impedance to continuously increase, and the active lithium ions to continuously decrease, therefore, in order to solve the problem, the application performs over-discharge processing on the large capacity battery. Over-discharge can reduce the thickness of the SEI film, activate the dead lithium in the large capacity battery, and reduce the ion impedance; the lithium supplement device is used to supplement lithium to the large capacity battery online, which can improve the content of active lithium ions in the large capacity battery; the functional interface on the large capacity battery is used to realize the online exhaust of the large capacity battery, which reduces the influence of excessive gas pressure on the performance of the large capacity battery; then, the cycle performance of the large capacity battery is improved from the aspects of activating dead lithium, reducing ion impedance, reducing gas pressure, and improving the content of active lithium ions, and the online repair of the large capacity battery is completed.

[0068] Further, in order to improve the repair effect of the large capacity battery after over-discharge, the above method further includes step d: performing heating processing on the large capacity battery through the heat transfer pipe on the polarity terminal of the large capacity battery. The application transmits heat to each single battery in the large capacity battery through the heat transfer pipe, and the positive and negative electrode materials in each single battery change the crystal structure after being heated to restore their original structure, so that the active lithium ions can be smoothly inserted or extracted during the charging and discharging process, and the cycle performance of the large capacity battery can be further improved.

[0069] The specific steps of method four are as follows:

[0070] Step 1: real-time detection of the large capacity battery, if the capacity of the large capacity battery is detected to be attenuated to X1 or after performing over Y1 times of charging and discharging cycles, at least once step 2 is performed; wherein 85%≤X1≤98%; Y1≥200 times;

[0071] Step 2: first stage online repair

[0072] Step a: supplement liquid to the large capacity battery directly through the functional interface, and exhaust the large capacity battery through the functional interface;

[0073] Step 3: real-time detection of the large capacity battery, if the large capacity battery reaches the second repair condition, at least once step 4 is performed;

[0074] Step 4: Second stage online repair

[0075] Step b: Over-discharge the large capacity battery;

[0076] Step c: Lithium supplement of the large capacity battery by the lithium supplement device

[0077] The second repair condition is as follows:

[0078] Case 1: The capacity and capacity retention rate of the large capacity battery do not improve significantly after the first stage online repair;

[0079] Case 2: The capacity of the large capacity battery decays to X2 or executes over Y2 times of charge and discharge; wherein 70%≤X2≤95%; Y2>Y1.

[0080] Since the decay of the large capacity battery is different in each stage, the repair process of the large capacity battery is roughly divided into two stages:

[0081] The first stage through the step of supplementing liquid compensates for the consumption of electrolyte in the large capacity battery, improves the conductivity of lithium ions, discharges the large capacity battery, reduces the impact of excessive gas pressure on the performance of the large capacity battery, and also makes the liquid supplement process smoother, thereby completing the first stage online repair of the large capacity battery;

[0082] After the large capacity battery runs for a long time again, the SEI film gradually thickens, causing the ion impedance to continuously increase, and the active lithium ions to continuously decrease. Therefore, in order to solve this problem, the second stage through over-discharge can reduce the thickness of the SEI film, activate the dead lithium in the large capacity battery, and reduce the ion impedance. The lithium supplement device is used to supplement the large capacity battery online. The above two ways can improve the content of active lithium ions in the large capacity battery, thereby completing the second stage online repair of the large capacity battery.

[0083] Further, in order to improve the repair effect of the large capacity battery after over-discharge, the above method further includes step d: a step of performing heating treatment on the large capacity battery through the heat transfer pipe on the polarity terminal of the large capacity battery. The heat transfer pipe of the present application transfers heat to each single battery in the large capacity battery. The positive and negative electrode materials in each single battery change their lattice structure after being heated, thereby restoring their original structure, so that the active lithium ions can be smoothly embedded or extracted in the positive and negative electrodes during the charge and discharge process, thereby further improving the cycle performance of the large capacity battery.

[0084] Further, the second stage repair further includes e, performing liquid supplement or replacement on the large capacity battery through the functional interface, and performing secondary discharge on the large capacity battery through the functional interface.

[0085] The specific steps of method five are as follows:

[0086] Step 1: Real-time detection of large capacity battery, if the capacity of the large capacity battery is detected to decay to X1 or the number of charge-discharge cycles is more than Y1, at least one step 2 is performed; wherein 85%≤X1≤98%; Y1≥200 times;

[0087] Step 2: First stage online repair

[0088] Step a: supplementing lithium to the large capacity battery through a lithium supplementing device;

[0089] Step 3: Real-time detection of large capacity battery capacity, if the large capacity battery reaches the second repair condition, at least one step 4 is performed;

[0090] Step 4: Second stage online repair

[0091] Step b: performing over-discharge on the large capacity battery;

[0092] Step c: performing liquid supplementing or replacing on the large capacity battery through a functional interface, and performing degassing on the large capacity battery through the functional interface;

[0093] The second repair condition is as follows:

[0094] Case 1: The capacity and capacity retention rate of the large capacity battery do not obviously increase after the first stage online repair;

[0095] Case 2: The capacity of the large capacity battery decays to X2 or the number of charge-discharge cycles is more than Y2; wherein 70%≤X2≤95%; Y2>Y1.

[0096] Since the decay of the large capacity battery is caused by different reasons in each stage, the repair process of the large capacity battery is roughly divided into two stages: the first stage supplements lithium to increase the content of active lithium ions in the large capacity battery, and completes the first stage online repair of the large capacity battery;

[0097] After the large capacity battery is operated for a long time again, the SEI film gradually thickens, resulting in continuous increase of ion impedance and continuous decrease of active lithium ions. Therefore, in order to solve this problem, the second stage reduces the thickness of the SEI film through over-discharge, activates the dead lithium in the large capacity battery, reduces the ion impedance, supplements the electrolyte in the large capacity battery through the functional interface of the large capacity battery, makes up for the consumption of the electrolyte in the large capacity battery, and improves the conductivity of lithium ions. At the same time, the large capacity battery is degassed, which not only reduces the influence of excessive gas pressure on the performance of the large capacity battery, but also makes the liquid supplementing process more smooth;

[0098] Or the stage uses the function interface of the large capacity battery to replace the liquid of the large capacity battery, makes up the consumption of the electrolyte in the large capacity battery, improves the conductivity of lithium ions, and exhausts the large capacity battery to reduce the influence of excessive gas pressure on the performance of the large capacity battery, so that the replacement process is more smooth, and the impurities in the old electrolyte are removed during the replacement process, so that the electrolyte is purified, and the second stage of the large capacity battery online repair is completed.

[0099] Further, in order to improve the repair effect of the large capacity battery after over-discharge, the above method further comprises step d: a step of performing heating treatment on the large capacity battery through the heat transfer pipe on the polarity terminal of the large capacity battery. The present application transmits heat to each single battery in the large capacity battery through the heat transfer pipe, and the positive and negative electrode materials in each single battery change the crystal structure after being heated, thereby restoring the original structure, so that the active lithium ions can be smoothly embedded or removed from the positive and negative electrodes during the charging and discharging process, thereby further improving the cycle performance of the large capacity battery.

[0100] Further, the above step 4 further comprises step e: performing secondary lithium supplement on the large capacity battery through the lithium supplement device.

[0101] Further, the above step 2 further comprises step f: performing liquid supplement on the large capacity battery through the function interface, and simultaneously performing exhaust on the large capacity battery through the function interface.

[0102] Further, in the five methods of the above large capacity battery online repair, the function interface is a columnar body, the columnar body is provided with a gas passage connecting the gas sharing chamber of the large capacity battery and the external gas pipe, and an electrolyte passage connecting the electrolyte sharing chamber of the large capacity battery and the external liquid pipe, and the gas passage and the electrolyte passage are isolated from each other.

[0103] In the above five methods, the lithium supplement device comprises a lithium source, a lithium supplement wire, a variable resistor and a switch; the lithium source is arranged in the large capacity battery and soaked in the electrolyte; one end of the lithium supplement wire is electrically connected with the lithium source, and the other end is used to connect with the polarity terminal of the large capacity battery, and the lithium supplement wire is provided with the switch and the variable resistor; the switch is used to turn on or cut off the lithium supplement wire.

[0104] The lithium source comprises two copper mesh layers and a metal lithium layer arranged between the two copper mesh layers.

[0105] Further, in the above five methods, the cut-off voltage of over-discharge is 0.01V to 2.4V; and the heating temperature range is 45 to 60℃. BRIEF DESCRIPTION OF DRAWINGS

[0106] Fig. 1 is a discharge capacity retention rate curve of each sample in Example 1;

[0107] Fig. 2 is a discharge capacity retention rate curve of each sample in Example 2;

[0108] Figure 3 is a discharge capacity retention rate curve of each sample in Example 3;

[0109] Figure 4 is a discharge capacity retention rate curve of each sample in Example 4;

[0110] Figure 5 is a discharge capacity retention rate curve of samples 1 to 8 in Example 1 to Example 4;

[0111] Figure 6 is a schematic diagram of a structure of a lithium ion battery to be repaired provided with a lithium supplement electrode;

[0112] Figure 7 is a capacity improvement rate curve in Example 5;

[0113] Figure 8 is a capacity improvement rate curve in Example 6;

[0114] Figure 9 is a conductivity test curve of a mixed solution of ethylene carbonate, ethyl methyl carbonate and lithium bisfluorosulfonylimide in Example 7;

[0115] Figure 10 is a capacity improvement rate curve in Example 7;

[0116] Figure 11 is a structure diagram of a first large-capacity battery;

[0117] Figure 12 is a structure diagram of a second large-capacity battery;

[0118] Figure 13 is a sectional view of the second large-capacity battery;

[0119] Figure 14 is a structure diagram of a functional interface provided on an end plate of a large-capacity battery;

[0120] Figure 15 is a schematic diagram of a lithium supplement device;

[0121] Figure 16 is a capacity improvement rate curve of Example 12;

[0122] Figure 17 is a capacity retention rate curve of Example 15;

[0123] Figure 18 is a capacity retention rate curve of Example 18;

[0124] Reference numerals in the drawings are:

[0125] 01, positive electrode polarity terminal; 02, wiring terminal; 03, diode; 04, variable resistor; 05, shell;

[0126] 100-large capacity battery, 1-single battery, 2-first hollow pipe, 3-second hollow pipe, 4-box, 5-electrolyte sharing chamber, 6-gas sharing chamber, 7-functional interface, 8-gas passage, 9-electrolyte passage, 10-lithium supplement device, 11-lithium source, 12-lithium supplement lead, 13-variable resistor, 14-switch. DETAILED DESCRIPTION

[0127] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of the present application.

[0128] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in other manners different from those described herein, and those skilled in the art can make similar generalizations without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0129] The main reasons for the capacity decline of lithium-ion batteries are mainly the following two aspects:

[0130] 1. The thickening of SEI film of lithium-ion battery will bring a series of negative effects

[0131] Firstly, the thickening of SEI film will cause the increase of battery impedance, which is an index to measure the internal resistance of the battery. The increase of impedance means the increase of internal resistance of the battery, which affects the moving speed of lithium ions, thereby reducing the performance and efficiency of the battery.

[0132] Secondly, the thickening of SEI film will also cause irreversible loss of lithium. During the aging process of the battery, the SEI film is thickened due to the deposition of reaction products of the electrolyte, which is accompanied by the consumption of lithium ions, causing irreversible loss of lithium. Lithium is an important element in the battery, and its loss directly leads to the reduction of battery capacity.

[0133] In addition, the thickening of SEI film not only affects the negative electrode of the battery, but also blocks the active particles of the positive electrode, increases the impedance, and causes the reduction of available active material and capacity. This means that the battery will gradually decrease in energy and power that it can provide during storage and use.

[0134] The thickening of SEI film is an important phenomenon in the aging process of lithium-ion batteries, which directly affects the performance and life of the battery by increasing impedance, causing lithium loss, and reducing available capacity.

[0135] 2. Decomposition and consumption of electrolyte

[0136] The decomposition and consumption of electrolyte will reduce the conductivity of electrolyte, thereby causing the decline of cycle performance of the battery.

[0137] In order to realize the repair of the capacity and capacity retention rate of the old battery, the technical means adopted by the present application is that: over-discharge step is performed on the old lithium ion battery, and heating step is performed on the old lithium ion battery.

[0138] The present application promotes the decomposition of the SEI layer on the surface of the negative plate of the battery to a certain extent by discharging, reduces the thickness of the SEI layer, and facilitates the composition and structure of the SEI layer in the subsequent step, and activates the "dead lithium" in the negative electrode of the battery, so that the lithium participates in the subsequent charge and discharge cycle (improves the capacity of the old battery).

[0139] The old lithium ion battery is heated, so that the crystal structure of the positive and negative electrode materials of the battery changes, thereby restoring the original structure, and the capacity of the battery can be maintained (improving the capacity retention rate of the old battery).

[0140] In view of the above problems, the present application over-discharges the battery with capacity attenuation, decomposes the SEI film, and thins the thickness of the SEI film; then, the gas in the battery cavity after over-discharge can be discharged, and electrolyte can be added to the battery cavity for repair. At the same time, the present application uses a lithium supplement electrode to supplement lithium to the battery with capacity attenuation, to supplement the active lithium lost in the battery cycle process, to overcome the problem of reducing the cycle life of the existing lithium ion battery due to the consumption of lithium ions, and to achieve the purpose of battery repair.

[0141] It should be noted that the present application does not make specific limitation on the sequence of over-discharge and lithium supplement, and over-discharge can be performed first and then lithium supplement, or over-discharge and lithium supplement can be performed simultaneously.

[0142] In the present application, first, multiple waste 20Ah square shell lithium iron phosphate batteries (Lishen) of the same manufacturer and the same batch are taken, the initial capacity of the battery is tested, and multiple batteries with similar initial capacity are selected as samples (including test samples and comparison samples) in the following examples.

[0143] The specific method for testing the capacity is: at 25℃±5℃, using a 5V-20A charge and discharge tester, constant current charging (1C) to voltage 3.65V, then constant voltage charging to cut-off current 1 / 20C, standing for 10min, then constant current discharging (1C) to voltage 2.5V cut-off, as one cycle, a total of 10 cycles, the average value of the battery capacity is taken as the capacity base, and the mass is 100%.

[0144] The present application is further described in combination with specific examples.

[0145] Example 1

[0146] In this embodiment, the repair scheme of over-discharge and synchronous lithium supplement is used to repair the samples to be repaired.

[0147] Specifically, the following steps can be performed:

[0148] (1) Preparation of test sample 1, test sample 2 and comparative sample 4;

[0149] Among the screened samples, three lithium ion batteries were selected and placed in a glove box. Each lithium ion battery was treated as follows:

[0150] The lithium ion battery was inverted, the bottom plate of the lithium ion battery was opened with a tool, the lithium supplement electrode was placed above the electrode assembly, and the terminal of the lithium supplement electrode was extended out of the battery shell 05. The battery bottom plate was installed and sealed with epoxy resin. The three treated lithium ion batteries were used as test sample 1, test sample 2 and comparative sample 4 of the present embodiment, respectively. The specific structure can be seen from Figure 6.

[0151] In the present embodiment, the lithium-rich negative electrode sheet is used as the lithium supplement electrode. In other embodiments, lithium metal sheets or other lithium-rich materials can also be used as lithium supplement electrodes.

[0152] (2) Repair;

[0153] (2.1) Lithium supplement and over-discharge repair of test sample 1 and test sample 2;

[0154] The terminals 02 of the lithium supplement electrodes in test sample 1 and test sample 2 were electrically connected to the positive polarity terminals 01 through resistors 04, diodes 03 and ammeters (as shown in Figure 6). The resistance value of the resistor 04 was adjusted to control the lithium supplement current to be 1 mA. The positive electrodes of test sample 1 and test sample 2 were supplemented with lithium. At the same time, test sample 1 and test sample 2 were over-discharged to a voltage of 0.01 V on a charge-discharge tester, and after about 24 hours, the terminals of the lithium supplement electrodes were disconnected from the positive polarity terminals of the battery, and the gas in the cavities of test sample 1 and test sample 2 was discharged. The cavities of test sample 1 and test sample 2 were injected with electrolyte, and the repair of test sample 1 and test sample 2 was completed.

[0155] In other embodiments, an external power supply can be added to supplement lithium to the positive electrode. The terminals of the lithium supplement electrodes are connected to the positive electrode of the external power supply, and the negative electrode of the external power supply is electrically connected to the negative polarity terminal of the battery through a resistor, a diode and an ammeter to supplement lithium to the negative electrode.

[0156] In other embodiments, the lithium supplement current is determined according to the battery capacity, C is a constant between 20 and 200, and the larger the specific capacity, the larger the constant C value. Typically, the lithium supplement current is any value within the range of 0.1 mA to 10 mA.

[0157] The constant resistance over-discharge method is adopted in the embodiment, and the resistance is determined according to the internal resistance of the battery cell. The smaller the internal resistance, the smaller the constant resistance value, and vice versa. In some other embodiments, the constant voltage over-discharge method can also be adopted, and the over-discharge voltage can be greater than 0.01V and less than or equal to 2.5V.

[0158] (2.2) Over-discharge repair is performed on the comparative sample 1 and the comparative sample 2;

[0159] The constant resistance over-discharge method is adopted, and the comparative sample 1 and the comparative sample 2 are over-discharged to a voltage of 0.01V on the charge-discharge tester for about 24 hours. Then, the gas in the cavities of the comparative sample 1 and the comparative sample 2 is discharged. The electrolyte is injected into the cavities of the comparative sample 1 and the comparative sample 2, and the repair of the comparative sample 1 and the comparative sample 2 is completed.

[0160] (2.3) Lithium supplement repair is performed on the comparative sample 4;

[0161] The wiring terminal of the lithium supplement electrode in the comparative sample 4 is electrically connected to the positive polarity terminal thereof through a variable resistor, a diode and an ammeter. The resistance value of the variable resistor is adjusted to control the lithium supplement current to be 1mA. The positive electrode of the comparative sample 4 is continuously supplemented with lithium.

[0162] It should be noted that in the subsequent step (3) of the charge-discharge test, the wiring terminal of the lithium supplement electrode in the comparative sample 4 is always electrically connected to the positive polarity terminal thereof through a variable resistor, a diode and an ammeter.

[0163] (3) Charge-discharge test:

[0164] (3.1) The capacity of the repaired test sample 1, the repaired test sample 2, the comparative sample 1, the comparative sample 2 and the comparative sample 4 is directly tested on the charge-discharge tester at 0.5-1C. The capacity of the comparative sample 5 and the comparative sample 6 is also measured.

[0165] (3.2) At 25℃±5℃, the battery is charged to a voltage of 3.65V at a constant current (1C) using a 5V-20A charge-discharge tester, and then charged to a current of 1 / 20C at a constant voltage, and then left for 10 minutes, and then discharged to a cut-off voltage of 2.5V at a constant current. This is one cycle. The capacity of the battery after 100th, 200th, 300th, 400th and 480th cycle discharge is tested, and the capacity retention rate of each sample after 100th, 200th, 300th, 400th and 480th charge-discharge cycle is calculated in combination with the initial cycle capacity of the battery.

[0166] It should be noted that:

[0167] 1. In the embodiment, the resistance value of the variable resistor is adjusted to control the size of the lithium supplement current, so that the lithium supplement is controllable, and the lithium precipitation phenomenon of the negative electrode due to excessive lithiumization is prevented.

[0168] 2、The over-discharge in the embodiment takes over-discharge to 0.01V as an example, and the time length of over-discharge needs to be controlled to ensure that the negative current collector is not damaged.

[0169] 3、The components of the electrolyte are one or more of the following: ethylene carbonate, propylene carbonate, vinylene carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl propargyl carbonate, 1,4-butyrolactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate or ethyl butyrate, and a lithium salt.

[0170] The lithium salt is one or more of LiPF6, LiClO4, LiBF4, LiBOB, LiODFB, LiTDI, LiTFSI and LiFSI.

[0171] In other embodiments, according to actual needs, corresponding additives can be added to the electrolyte, such as lithium supplementing additives or film forming additives, to achieve better repair effects.

[0172] 4、The above-mentioned comparative sample 1, comparative sample 2, comparative sample 4, comparative sample 5 and comparative sample 6 can be used as comparative samples in subsequent embodiments.

[0173] The specific test data of the embodiment is shown in Table 1.1, Table 1.2 and Figure 1.

[0174] Table 1.1: Capacity data of each sample

[0175] Table 1.2: Discharge capacity retention rate data of each sample

[0176] As can be seen from Table 1.1, Table 1.2 and Figure 1, after completing the repair once, the capacity retention rates of test sample 1, test sample 2, comparative sample 1, comparative sample 2 and comparative sample 4 are basically always greater than those of comparative sample 5 and comparative sample 6 (comparative sample 4 has a higher capacity retention rate before 480 cycles of charge and discharge, and the capacity retention rate is less than that of comparative sample 5 and comparative sample 6 after 480 cycles of charge and discharge, and the reason is analyzed, which may be due to lithium precipitation in the negative electrode); it can be concluded that over-discharge synchronous lithium supplementing, separate over-discharge and separate lithium supplementing can all achieve repair of lithium ion batteries.

[0177] After 480 cycles of charge and discharge, the capacity retention rates of test sample 1 and test sample 2 are slightly greater than those of comparative sample 1, comparative sample 2 and comparative sample 4; it can be proved that the over-discharge synchronous lithium supplementing in the embodiment can obtain better repair effect compared with the separate over-discharge and separate lithium supplementing schemes.

[0178] When the repaired lithium ion battery is subjected to charge-discharge cycling for a period of time, the capacity again appears to be attenuated, and the method of the present embodiment can be used for multiple repairs.

[0179] Embodiment 2

[0180] Unlike Embodiment 1, the present embodiment uses a repair scheme of first over-discharging and then lithium supplementing on the sample to be repaired;

[0181] Specifically, the following steps can be performed:

[0182] (1) Prepare test sample 3 and test sample 4;

[0183] Among the screened samples, select two lithium ion batteries, place them in a glove box, and perform the following treatment on each lithium ion battery:

[0184] Invert the lithium ion battery, use a tool to open the bottom plate of the lithium ion battery, place the lithium supplementing electrode above the electrode assembly, and make the wiring terminal of the lithium supplementing electrode protrude out of the battery shell. Install the battery bottom plate and seal it with epoxy resin. The two treated lithium ion batteries are used as test sample 3 and test sample 4 of the present embodiment. The specific structure can be seen in Figure 6.

[0185] In the present embodiment, the lithium-rich negative electrode sheet is used as the lithium supplementing electrode. In other embodiments, lithium metal sheets or other lithium-rich materials can also be used as lithium supplementing electrodes.

[0186] (2) Repair;

[0187] Over-discharge and lithium supplementing are performed on test sample 3 and test sample 4:

[0188] Using the constant resistance over-discharge method, test sample 3 and test sample 4 are over-discharged to a voltage of 0.01V on the charge-discharge tester (in other embodiments, the over-discharge voltage can be greater than 0.01V and less than or equal to 2.5V). The gas in the internal cavity of test sample 3 and test sample 4 is discharged; electrolyte is injected into the internal cavity of test sample 3 and test sample 4;

[0189] After that, the wiring terminal of the lithium supplementing electrode in test sample 3 and test sample 4 is electrically connected to the positive electrode polarity terminal through a variable resistor, a diode, and an ammeter. The resistance value of the variable resistor is adjusted to control the lithium supplementing current to be 1mA, and the positive electrode of test sample 3 and test sample 4 is supplemented with lithium;

[0190] It should be noted that in the subsequent step (3) charge-discharge test process of the present embodiment, the wiring terminal of the lithium supplementing electrode in test sample 3 and test sample 4 is always electrically connected to the positive electrode polarity terminal through a variable resistor, a diode, and an ammeter.

[0191] In some other embodiments, the lithium supplementing current can also be any value ranging from 0.1 to 10 mA.

[0192] (3) Charge-discharge test:

[0193] (3.1) Directly test the capacity of the repaired test sample 3, the test sample 4 and the comparative sample 4 on a charge-discharge tester at 0.5-1C;

[0194] (3.2) At 25℃±5℃, use a 5V-20A charge-discharge tester to charge at a constant current (1C) to a voltage of 3.65V, then charge at a constant voltage to a current of 1 / 20C, stand for 10 min, then discharge at a constant current to a cut-off voltage of 2.5V, which is one cycle, test the capacity of the battery after 100th, 200th, 300th, 400th and 480th cycle, and calculate the capacity retention rate of each sample at the 100th, 200th, 300th, 400th and 480th charge-discharge cycle based on the initial cycle capacity of the battery.

[0195] The specific test data of this embodiment are shown in Table 2.1, Table 2.2 and Figure 2.

[0196] Table 2.1 Capacity data of each sample

[0197] Table 2.2 Discharge capacity retention rate data of each sample

[0198] As can be seen from Table 2.1, Table 2.2 and Figure 2, after one repair, the capacity retention rate of the test sample 3, the test sample 4, the comparative sample 1, the comparative sample 2 and the comparative sample 4 is basically greater than that of the comparative sample 5 and the comparative sample 6 (the comparative sample 4 has a higher capacity retention rate before the 480th charge-discharge cycle, and the capacity retention rate is less than that of the comparative sample 5 and the comparative sample 6 after the 480th charge-discharge cycle, and the reason is that the negative electrode lithium precipitation leads to it); it can be concluded that over-discharge followed by lithium supplementing, over-discharge alone and lithium supplementing alone can all achieve the repair of lithium ion batteries.

[0199] And after 480 cycles of charge-discharge, the capacity retention rate of the test sample 3 and the test sample 4 of this embodiment is slightly greater than that of the comparative sample 1, the comparative sample 2 and the comparative sample 4. It can be proved that the over-discharge followed by lithium supplementing in this embodiment can obtain better repair effect compared with the over-discharge alone and the lithium supplementing alone.

[0200] When the repaired lithium ion battery has capacity decay again after a period of charge-discharge cycle, it can also be repaired multiple times by the method of this embodiment.

[0201] Embodiment 3

[0202] Different from embodiment 1, this embodiment is to set the repair scheme of the over-discharge synchronous lithium supplement of the to-be-repaired sample for a certain time, that is, this embodiment simultaneously starts the over-discharge and lithium supplement of the to-be-repaired sample, and after the over-discharge is completed, the lithium supplement is continuously performed for a certain time.

[0203] Specifically, the following steps can be performed:

[0204] (1) Preparation of test sample 5 and test sample 6;

[0205] Among the screened samples, two lithium ion batteries are selected and placed in a glove box, and each lithium ion battery is processed as follows:

[0206] The lithium ion battery is inverted, the bottom plate of the lithium ion battery is opened with a tool, the lithium supplement electrode is placed above the electrode assembly, and the wiring terminal of the lithium supplement electrode is stretched out of the battery shell. The battery bottom plate is installed and sealed with epoxy resin. The two processed lithium ion batteries are used as test sample 5 and test sample 6 of this embodiment, and the specific structure can be referred to as shown in FIG. 6.

[0207] In this embodiment, the lithium-rich negative electrode sheet is used as the lithium supplement electrode, and in other embodiments, lithium metal sheets or other lithium-rich materials can also be used as the lithium supplement electrode.

[0208] (2) Repair;

[0209] The test sample 5 and the test sample 6 are over-discharged and supplemented with lithium:

[0210] The test sample 5 and the test sample 6 are over-discharged to a voltage equal to 0.01V (in other embodiments, the over-discharge voltage can be greater than 0.01V and less than or equal to 2.5V) on a charge-discharge tester using a constant resistance over-discharge method. At the same time, the wiring terminal of the lithium supplement electrode in the test sample 5 and the test sample 6 is electrically connected to the positive polarity terminal thereof through a variable resistor, a diode, and an ammeter. The resistance value of the variable resistor is adjusted to control the lithium supplement current to be 1mA (in other embodiments, the lithium supplement current can also be any value within the range of 0.1 to 10mA), and the positive electrode of the test sample 5 and the test sample 6 is supplemented with lithium. After about 24 hours, the wiring terminal of the lithium supplement electrode is disconnected from the positive polarity terminal of the battery, and the gas in the internal cavity of the test sample 5 and the test sample 6 is discharged. The internal cavity of the test sample 5 and the test sample 6 is injected with electrolyte. Then, the wiring terminal of the lithium supplement electrode in the test sample 5 and the test sample 6 is electrically connected to the positive polarity terminal thereof through a variable resistor, a diode, and an ammeter. The resistance value of the variable resistor is adjusted to control the lithium supplement current to be 1mA, and the positive electrode of the test sample 5 and the test sample 6 is supplemented with lithium again.

[0211] It should be noted that in the subsequent step (3) of the charge and discharge test, the terminal of the lithium supplement electrode in the test sample 5 and the test sample 6 is always electrically connected to the positive electrode terminal through a variable resistor, a diode and an ammeter.

[0212] (3) Charge and discharge test:

[0213] (3.1) Directly test the capacity of the repaired test sample 5 and the test sample 6 on the charge and discharge tester at 0.5-1C;

[0214] (3.2) At 25℃±5℃, use a 5V-20A charge and discharge tester to charge to a voltage of 3.65V at a constant current (1C), then charge to a current of 1 / 20C at a constant voltage, stand for 10min, and then discharge to a cut-off voltage of 2.5V at a constant current, which is one cycle. Test the capacity of the battery after 100th, 200th, 300th and 400th cycles, and calculate the capacity retention rate of the 100th, 200th, 300th and 400th charge and discharge cycles based on the initial cycle capacity of the battery.

[0215] The specific test data of this embodiment is shown in Table 3.1, Table 3.2 and Figure 3.

[0216] Table 3.1 Capacity data of each sample

[0217] Table 3.2 Discharge capacity retention rate data of each sample

[0218] As can be seen from Table 3.1, Table 3.2 and Figure 3, after completing one repair, the capacity retention rate of the test sample 5, the test sample 6, the comparative sample 1, the comparative sample 2 and the comparative sample 4 is basically greater than that of the comparative sample 5 and the comparative sample 6 during the 100th to 400th charge and discharge cycles. It can be concluded that over-discharge synchronous lithium supplement, separate over-discharge and separate lithium supplement can all achieve the repair of lithium ion batteries.

[0219] After 400th charge and discharge cycles, the capacity retention rate of the test sample 5 and the test sample 6 of this embodiment is greater than that of the comparative sample 1, the comparative sample 2 and the comparative sample 4. It can be proved that the method of over-discharge synchronous lithium supplement and then lithium supplement in this embodiment can obtain better repair effect compared with the methods of separate over-discharge and separate lithium supplement.

[0220] When the repaired lithium ion battery shows capacity decay again after a period of charge and discharge cycles, it can also be repaired multiple times by the method of this embodiment.

[0221] Example 4

[0222] Different from embodiment 1, this embodiment carries out the repair scheme of first over-discharging and then high-frequency lithium supplement on the sample to be repaired;

[0223] Specifically, the following steps can be performed:

[0224] (1) Prepare test sample 7 and test sample 8;

[0225] Among the screened samples, four lithium ion batteries are selected and placed in a glove box. Each lithium ion battery is processed as follows:

[0226] The lithium ion battery is inverted, the bottom plate of the lithium ion battery is opened with a tool, the lithium supplement electrode is placed above the electrode assembly, and the wiring terminal of the lithium supplement electrode is stretched out of the battery shell. The battery bottom plate is installed and sealed with epoxy resin. The four processed lithium ion batteries are used as test sample 7, test sample 8, comparative sample 7 and comparative sample 8 of this embodiment. The specific structure can be seen from FIG. 6.

[0227] In this embodiment, the lithium-rich negative electrode sheet is used as the lithium supplement electrode. In other embodiments, lithium metal sheets or other lithium-rich materials can also be used as lithium supplement electrodes.

[0228] (2) Repair;

[0229] (2.1) Over-discharge and high-frequency lithium supplement are performed on test sample 7 and test sample 8:

[0230] The constant resistance over-discharge method is used to over-discharge test sample 7 and test sample 8 on the charge-discharge tester to a voltage equal to 0.01V (in other embodiments, the over-discharge voltage can be greater than 0.01V and less than or equal to 2.5V). The gas in the internal cavity of test sample 7 and test sample 8 is discharged. The electrolyte is injected into the internal cavity of test sample 7 and test sample 8.

[0231] Then, the wiring terminal of the lithium supplement electrode in test sample 7 and test sample 8 is electrically connected to the positive terminal of the lithium supplement electrode through a variable resistor, a diode and an ammeter. The resistance value of the variable resistor is adjusted to control the lithium supplement current to be 10mA (in other embodiments, the lithium supplement current can also be any value within the range of 0.1 to 10mA). The charge-discharge tester is used to perform the following charge-discharge cycle process on test sample 7 and test sample 8:

[0232] 1C charging for 15s, standing for 15s, 1C discharging for 15s, standing for 15s as one cycle, and such cycle is repeated for 12h to 24h to promote the uniform dispersion of lithium ions to the positive electrode sheet, and the repair of test sample 7 and test sample 8 is completed.

[0233] (2.2) High-frequency lithium supplement repair is performed on comparative sample 7 and comparative sample 8;

[0234] The terminal of the lithium supplement electrode in the comparative sample 7 and the comparative sample 8 is electrically connected with the positive terminal of the lithium supplement electrode through a rheostat, a diode and an ammeter, and the resistance of the rheostat is adjusted to control the lithium supplement current to be 10 mA;

[0235] The comparative sample 7 and the comparative sample 8 are subjected to the following charge-discharge cycle process on a charge-discharge tester:

[0236] One cycle is 1C charging for 15 s, standing for 15 s, 1C discharging for 15 s and standing for 15 s, and the cycle is repeated for 12 h to 24 h to promote the uniform dispersion of lithium ions to the positive electrode tab, and the repair of the comparative sample 7 and the comparative sample 8 is completed;

[0237] (3) Charge-discharge test:

[0238] (3.1) The capacity of the repaired test sample 7, the repaired test sample 8, the comparative sample 7 and the comparative sample 8 is directly tested on a charge-discharge tester at 0.5-1C;

[0239] (3.2) The capacity of the battery after the 100th, 200th, 300th, 400th and 480th cycle is tested at 25℃±5℃, and the capacity retention rate of each sample is calculated based on the initial cycle capacity of the battery.

[0240] The specific test data of this embodiment are shown in Table 4.1, Table 4.2 and FIG. 4.

[0241] Table 4.1 Capacity data of each sample

[0242] Table 4.2 Discharge capacity retention rate data of each sample

[0243] As can be seen from Table 4 and FIG. 4, after one repair, the capacity retention rate of the test sample 7, the test sample 8, the comparative sample 1, the comparative sample 2, the comparative sample 7 and the comparative sample 8 is greater than that of the comparative sample 5 and the comparative sample 6 during the 100th to 480th cycle. It can be concluded that over-discharge, high-frequency lithium supplement, over-discharge alone and high-frequency lithium supplement alone can all achieve the repair of lithium ion batteries.

[0244] The capacity retention rates of the test sample 7 and the test sample 8 of the embodiment are always greater than those of the comparative sample 1, the comparative sample 2, the comparative sample 7 and the comparative sample 8 between 100th and 480th charge-discharge cycles, which proves that the repair scheme of first over-discharging and then high-frequency lithium supplement can obtain better repair effect compared with the repair schemes of over-discharging alone or high-frequency lithium supplement alone.

[0245] When the capacity of the repaired lithium ion battery again decays after a period of charge-discharge cycles, the method of the embodiment can still be used for multiple repairs.

[0246] The discharge capacity retention rates of the test sample 1 to the test sample 8 of the embodiment are compared with those of the test sample 1 to the test sample 8 of the embodiment 1, and specific reference can be made to Table 5 and FIG. 5.

[0247] Table 5

[0248] As can be seen from Table 5 and FIG. 5, after one repair, the capacity retention rates of the test sample 7 and the test sample 8 in the embodiment and the test sample 5 and the test sample 6 in the embodiment 3 are basically always greater than those of the test sample 1 and the test sample 2 in the embodiment 1 and the test sample 3 and the test sample 4 in the embodiment 2 between 100th and 400th charge-discharge cycles, which proves that the repair schemes of first over-discharging and then high-frequency lithium supplement and over-discharging and synchronous lithium supplement and then continuous lithium supplement can obtain better repair effect compared with the repair schemes of over-discharging and synchronous lithium supplement and first over-discharging and then lithium supplement.

[0249] Embodiment 5

[0250] In the embodiment, 12 square lithium ion batteries of the same manufacturer and the same batch whose nominal capacity decays to 90% are selected as the old lithium ion batteries to be repaired;

[0251] Among them, two square lithium ion batteries are taken as the sample 1 and the sample 2 and are over-discharged according to the over-discharge cut-off voltage 2.0V, and then are tested by normal charge-discharge;

[0252] Among them, two square lithium ion batteries are taken as the sample 3 and the sample 4 and are over-discharged according to the over-discharge cut-off voltage 1.0V, and then are tested by normal charge-discharge;

[0253] Among them, two square lithium ion batteries are taken as the sample 5 and the sample 6 and are over-discharged according to the over-discharge cut-off voltage 0.01V, and then are tested by normal charge-discharge;

[0254] Among them, two square lithium ion batteries are taken as the comparative sample 1 and the comparative sample 2 and are only tested by normal charge-discharge;

[0255] The specific test data of the embodiment are shown in Table 6, Table 7 and FIG. 7.

[0256] Table 6 is the capacity value of 8 batteries performing 400 cycles

[0257] Table 7 is the capacity improvement rate of 8 batteries performing 400 cycles

[0258] From the above test, it is found that the discharge cut-off voltage is inversely proportional to the capacity recovery amplitude of the old battery. In order to improve the repair effect of the old battery, 0.01V is selected as the discharge cut-off voltage.

[0259] Example 6

[0260] In this embodiment, 12 square lithium ion batteries of the same manufacturer and the same batch with nominal capacity decayed to 90% are selected as old lithium ion batteries to be repaired, and the old lithium ion batteries are repaired by over-discharging and then heating;

[0261] In a normal temperature environment, the discharge cut-off voltage is set to 0.01V, and the 12 old batteries to be repaired are discharged by constant resistance discharge, and then stand for 5h;

[0262] The 12 old batteries to be repaired after over-discharge are divided into 6 groups, of which 5 groups are placed in an oven every 2 groups, and the 5 groups of old batteries to be repaired are heated at 40℃, 45℃, 50℃, 55℃ and 60℃ respectively, and stand to normal temperature after heating treatment, and are recorded as sample 1 to sample 10 respectively; wherein, the heating temperature of sample 1 and sample 2 is 40℃, the heating temperature of sample 3 and sample 4 is 45℃, the heating temperature of sample 5 and sample 6 is 50℃, the heating temperature of sample 7 and sample 8 is 55℃, and the heating temperature of sample 9 and sample 10 is 60℃;

[0263] In addition, 2 old batteries to be repaired only performing over-discharge step are used as comparative sample 1 and comparative sample 2 (comparative sample 1 and comparative sample 2 do not perform heating step);

[0264] The capacity of the repaired battery is directly tested on the charge-discharge tester; at 25℃±5℃, using 5V-20A charge-discharge tester, constant current (1C) charging to voltage 3.65V, then constant voltage charging to current 1 / 20C (1A), standing for 10min, then constant current discharging to cut-off voltage 2.5V, as a cycle, the data of 300 cycles of the repaired battery is tested.

[0265] The specific test data of this embodiment is shown in Table 8, Table 9 and Figure 8.

[0266] Table 8 is the capacity value of 12 batteries performing 300 cycles

[0267] Table 9 is the capacity improvement rate of 12 batteries performing 300 cycles

[0268] From the above table 8, table 9 and figure 8, it can be seen that the capacity improvement range of the lithium ion battery after over-discharge according to the over-discharge cut-off voltage 0.1V and then heating at 50℃ is not only the largest (i.e. the sample heated to 50℃ is improved by more than 4%), but also the capacity retention rate after 300 charge-discharge cycles after over-discharge and heating repair is also better.

[0269] Example 7

[0270] Since gas is generated in the battery during the over-discharge step, in order to avoid the problem that the high gas pressure in the battery will cause the battery charge-discharge performance in the later stage, the difference between this embodiment and example 6 is that an exhaust step is added in the repair process, which can be performed simultaneously with the over-discharge, or after the over-discharge, or after the heating step is performed.

[0271] Example 8

[0272] The difference between this embodiment and example 7 is that a liquid supplementing step is added in the repair process; specifically, the specific execution process of the repair process of this embodiment is as follows:

[0273] Over-discharge

[0274] At room temperature, set the discharge cut-off voltage to 0.01V, perform discharge treatment on the old battery to be repaired according to the constant resistance discharge mode, and then stand for 5h;

[0275] Heating

[0276] Put the old battery to be repaired into an oven for heating, the heating temperature is 50℃, and the heating lasts for 12h, and then stand to room temperature;

[0277] Liquid supplementing

[0278] Open the pressure relief port of the battery to be repaired in the glove box, then supplement liquid into the battery, stand for 30min, and then seal the pressure relief port;

[0279] Charge-discharge test

[0280] Directly test the capacity of the battery after repair on the charge-discharge tester; at 25℃±5℃, use a 5V-20A charge-discharge tester to charge at a constant current (1C) to a voltage of 3.65V, then charge at a constant voltage to a current of 1 / 20C (1A), stand for 10min, then discharge at a constant current to a cut-off voltage of 2.5V, which is one cycle, test the data of 300 cycles of the battery after repair.

[0281] The embodiment selects 14 square lithium ion batteries of 20 Ah of the same factory and the same batch whose nominal capacity attenuates to 90%;

[0282] Among them, 2 batteries are a group, marked as sample 1 and sample 2, and the repair mode of the above two samples is: only put into the oven to perform heating repair at 50 DEG C;

[0283] 2 batteries are a group, marked as sample 3 and sample 4, and the repair mode of the above two samples is: only perform over-discharge according to the discharge cut-off voltage 0.01V;

[0284] 2 batteries are a group, marked as sample 5 and sample 6, and the repair mode of the above two samples is: perform over-discharge according to the discharge cut-off voltage 0.01V and then put into the oven to perform heating at 50 DEG C;

[0285] 2 batteries are a group, marked as sample 7 and sample 8, and the repair mode of the above two samples is: perform over-discharge according to the discharge cut-off voltage 0.01V, then put into the oven to perform heating at 50 DEG C, and finally inject the conventional electrolyte;

[0286] 2 batteries are a group, marked as sample 9 and sample 10, and the repair mode of the above two samples is: perform over-discharge according to the discharge cut-off voltage 0.01V, then inject the conventional electrolyte, and finally put into the oven to perform heating at 50 DEG C;

[0287] 2 batteries are a group, marked as sample 11 and sample 12, and the repair mode of the above two samples is: perform over-discharge according to the discharge cut-off voltage 0.01V, then put into the oven to perform heating at 50 DEG C, and finally inject the self-made electrolyte;

[0288] 2 batteries are a group, marked as sample 13 and sample 14, and the repair mode of the above two samples is: perform over-discharge according to the discharge cut-off voltage 0.01V, then inject the self-made electrolyte, and finally put into the oven to perform heating at 50 DEG C;

[0289] The self-made electrolyte formula injected in the above test process includes solvents and lithium salts; wherein the solvent is a mixed solution of ethylene carbonate and ethyl methyl carbonate; the reason for selecting ethylene carbonate and ethyl methyl carbonate as the electrolyte solvent is that:

[0290] After ethylene carbonate is dissolved, its viscosity is relatively small. For lithium battery electrolyte, low viscosity means lower ion migration resistance, which means better battery performance. In addition, ethylene carbonate has another advantage, that is, it has good compatibility with graphite-based negative materials and can be used in high concentration.

[0291] Ethyl methyl carbonate has high conductivity and excellent low-temperature performance. Ethylene carbonate and ethyl methyl carbonate are combined in a certain proportion, which can effectively reduce the viscosity of the electrolyte while maximizing the conductivity, and also has good low-temperature performance.

[0292] In this embodiment, the lithium salt is selected as lithium bisfluorosulfonylimide. The reason for selecting lithium bisfluorosulfonylimide as the lithium salt of the electrolyte is that:

[0293] Compared with traditional lithium salts, lithium bisfluorosulfonylimide has more excellent comprehensive performance:

[0294] Firstly, the anion radius of lithium bisfluorosulfonylimide is larger, which is more easily dissociated into lithium ions, and can improve the conductivity of the electrolyte. Secondly, its decomposition temperature is higher than 200℃, and has better thermal stability, which can improve the high-temperature resistance of the electrolyte. Then, it can improve the discharge charge performance in low-temperature environment and maintain the capacity retention rate in high-temperature environment, which can improve the high and low temperature performance of lithium battery. Therefore, the use of lithium bisfluorosulfonylimide in electrolyte can significantly improve the cycle life, rate performance and safety of the battery.

[0295] In order to determine the optimal ratio of ethylene carbonate and ethyl methyl carbonate as solvents and different contents of lithium bisfluorosulfonylimide mixed, the following tests are carried out in this embodiment:

[0296] Ethylene carbonate and ethyl methyl carbonate are mixed in a mass ratio of 3:7, 4:6 and 5:5, respectively. Then different amounts of lithium bisfluorosulfonylimide are added to the mixed solution, and the conductivity is tested. At the same time, the conductivity of the electrolyte in the commercially available battery is tested, and the curve shown in Figure 9 is obtained. As can be seen from the figure, the best ratio of ethylene carbonate and ethyl methyl carbonate is 4:6, and the conductivity of the solvent is best when the content of lithium bisfluorosulfonylimide is 1.2mol / L, which is much better than that of the commercially available electrolyte. In Figure 9, 280 refers to the conventional electrolyte used in the commercially available 280Ah square lithium ion battery.

[0297] The specific test data of this embodiment is shown in Table 10, Table 11 and Figure 10.

[0298] Table 10 is the capacity value of 14 batteries performing 250 cycles

[0299] Table 11 is the capacity improvement rate of 12 batteries performing 250 cycles

[0300] From the above Tables 10, 11 and Figure 10, it can be seen that:

[0301] One: the capacity increase and capacity retention rate of sample 5 to sample 12 are higher than those of sample 3 and sample 4, that is, the repair effect of over-discharge, heating and liquid supplementing is better than that of over-discharge combined with heating, and the capacity increase and capacity retention rate of sample 3 and sample 4 are higher than those of sample 3 and sample 4, that is, the repair effect of over-discharge combined with heating is better than that of over-discharge alone or heating alone;

[0302] Secondly, in sample 9 to sample 12, the capacity increase and capacity retention rate of sample 11 and sample 12 are higher than those of sample 9 and sample 10, and it can be seen that the repair effect of the self-made electrolyte on the battery is obviously better than that of the conventional electrolyte.

[0303] The application also provides an online repair method of a large-capacity battery.

[0304] The first structure is shown in Fig. 11, and the large-capacity battery 100 comprises a plurality of single batteries 1, a first hollow pipe 2 and a second hollow pipe 3.

[0305] The plurality of single batteries 1 are placed side by side, and all the positive electrode terminals of the single batteries are connected as a total positive electrode, and all the negative electrode terminals of the single batteries are connected as a total negative electrode.

[0306] At least one heat transfer pipe is clamped on the total positive electrode and the total negative electrode.

[0307] The first hollow pipe 2 connects the gas zones of the plurality of single batteries, so that the gas pressures in the single batteries are consistent.

[0308] The second hollow pipe 3 connects the electrolyte zones of the plurality of single batteries, so that the electrolytes in the single batteries are consistent.

[0309] The functional interface in the first large-capacity battery comprises valves connected to the first hollow pipe and the second hollow pipe respectively.

[0310] The second structure is shown in Figs. 12 to 14, and the large-capacity battery 100 comprises a box body 4 and a plurality of single batteries 1.

[0311] The plurality of single batteries 1 are arranged in the same direction in the box body 4, and the electrolyte zones of the single batteries 1 are connected through an electrolyte sharing chamber 5 arranged at the bottom of the box body 4, and the gas zones of the single batteries are connected through a gas sharing chamber 6 arranged at the top of the box body 4.

[0312] Avoidance holes are formed on the top plate of the box body 4 corresponding to the polarity terminals of the single batteries 1, the polarity terminals of the single batteries 1 extend out of the avoidance holes, and the area of the top plate of the box body corresponding to the avoidance holes is fixedly sealed with the single battery shell.

[0313] The positive terminals of all the single cells 1 are connected as a total positive electrode, and the negative terminals of all the single cells are connected as a total negative electrode.

[0314] At least one heat pipe is clamped on the total positive electrode and the total negative electrode.

[0315] In the second large-capacity battery, the functional interface 7 is a columnar body arranged on the box body 4, the columnar body is provided with a gas passage 8 for connecting the large-capacity battery gas sharing chamber 6 and an external gas pipe, and an electrolyte passage 9 for connecting the large-capacity battery electrolyte sharing chamber 5 and an external liquid pipe, and the gas passage 8 and the electrolyte passage 9 are isolated from each other.

[0316] As shown in FIG. 15, the specific structure of the lithium supplement device 10 includes a lithium source 11, a lithium supplement wire 12, a variable resistor 13, and a switch 14.

[0317] The lithium source 11 is arranged in the large-capacity battery and is soaked in the electrolyte.

[0318] One end of the lithium supplement wire 12 is electrically connected with the lithium source 11, and the other end is used for being connected with the negative terminal of the large-capacity battery, and the lithium supplement wire 12 is sequentially provided with the switch 14 and the variable resistor 13 between the connection end connected with the negative terminal of the large-capacity battery and the connection end connected with the lithium source 11; the switch 14 is used for turning on or cutting off the lithium supplement wire 12.

[0319] The lithium source 11 includes two layers of copper mesh layers and a metal lithium layer arranged between the two layers of copper mesh layers.

[0320] In the first large-capacity battery structure, the lithium source 11 of the lithium supplement device is arranged in the second hollow pipe 3, and in the second large-capacity battery structure, the lithium source 11 of the lithium supplement device is arranged in the electrolyte sharing chamber 5.

[0321] Based on the above introduction of the reasons for the capacity reduction of the lithium ion battery and the structure of the large-capacity battery, the present application utilizes the structural characteristics of the large-capacity battery, mainly utilizes the methods of supplementing and replacing the electrolyte, discharging gas, and supplementing lithium, to realize the online repair of the large-capacity battery.

[0322] Example 9

[0323] In this embodiment, the second large-capacity battery structure is taken as an example to describe the specific repair process in detail.

[0324] Step 1: Real-time detection of the large-capacity battery, if the large-capacity battery is detected to be attenuated to X or after Y times of charging and discharging cycles are performed, at least one step 2 is performed; wherein 85%≤X≤98%; Y≥200 times;

[0325] Step 2: Repair process;

[0326] Step a: perform liquid supplement to the large capacity battery through the functional interface, and perform gas discharge to the large capacity battery through the functional interface;

[0327] The specific process of this step a is: open the valves on the gas channel between the external gas pipe and the functional interface, and the electrolyte channel between the external liquid pipe and the functional interface, and then the electrolyte enters the large capacity battery through the external liquid pipe and the electrolyte channel in sequence, and the gas in the large capacity battery is discharged through the gas channel and the external gas pipe in sequence;

[0328] This embodiment can realize the liquid supplement and gas discharge of the large capacity battery on line through the functional interface of the large capacity battery. Through the step of supplementing liquid while discharging gas, the consumption of electrolyte in the large capacity battery is compensated, the conductivity of lithium ions is improved, the gas discharge is performed on the large capacity battery, the influence of excessive gas pressure on the performance of the large capacity battery is reduced, and the liquid supplement process is more smooth;

[0329] In this embodiment, the liquid supplement step can be replaced by a liquid replacement step. The specific process of the liquid replacement is: first, open the valves on the gas channel between the external gas pipe and the functional interface, and the electrolyte channel between the external liquid pipe and the functional interface, and then inject inert gas into the large capacity battery through the external gas pipe and the gas channel in sequence, and the old electrolyte in the large capacity battery is discharged through the electrolyte channel and the external liquid pipe; then, the new electrolyte enters the large capacity battery through the external liquid pipe and the electrolyte channel in sequence, and the gas in the large capacity battery is discharged through the gas channel and the external gas pipe in sequence, and then the replacement of the electrolyte in the large capacity battery is completed. Compared with the liquid supplement, the liquid replacement process can also remove impurities in the old electrolyte, and purify the electrolyte;

[0330] Step b: supplement lithium to the large capacity battery through the lithium supplement device.

[0331] The specific process of this step b is: open the switch, adjust the resistance value of the variable resistor, control the lithium supplement current to be 1 mA, and realize the lithium supplement to the large capacity battery.

[0332] In this embodiment, step 2 is performed in the order of performing step b after performing step a. The main reason is that supplementing and replacing liquid first and then supplementing lithium can ensure that the active lithium has better conductivity. In some other embodiments, lithium can be supplemented first and then liquid can be supplemented and replaced.

[0333] When the repaired large capacity battery is in the charging and discharging cycle for a period of time, the capacity again appears to be attenuated, and the method of this embodiment can be used for multiple repairs.

[0334] Embodiment 10

[0335] Since long-term operation of the large-capacity battery can cause the SEI film to thicken, the SEI film that is too thick can cause the ion impedance to increase and the active lithium ions to decrease, and thus, in order to solve this problem, the repair process further includes step c of performing an over-discharge step on the large-capacity battery based on the embodiment 1;

[0336] The over-discharge step on the large-capacity battery can reduce the thickness of the SEI film, activate the dead lithium in the large-capacity battery, and reduce the ion impedance;

[0337] The over-discharge step can be performed before the liquid replacement, between the liquid replacement and the lithium supplement, or during the over-discharge process while the lithium supplement device is used to supplement lithium to the large-capacity battery. It should be noted that during the over-discharge process, the gas production in the large-capacity battery can be further increased, and if the over-discharge step is performed between the liquid replacement and the lithium supplement, a secondary exhaust step for the large-capacity battery needs to be performed during the over-discharge step or after the over-discharge step to avoid affecting the cycle performance of the large-capacity battery due to excessive gas pressure after the repair is completed.

[0338] The cut-off voltage of the over-discharge step needs to be controlled between 0.01 V and 2.4 V when the over-discharge step is performed on the large-capacity battery. Specifically, the cut-off voltage of the over-discharge step can be selected from a high-voltage range, such as between 1.0 V and 2.4 V, a medium-voltage range, such as between 0.1 V and 0.9 V, or a low-voltage range, such as between 0.01 V and 0.09 V.

[0339] Embodiment 11

[0340] This embodiment is based on the embodiment 10 and adds step d of performing a heating step on the large-capacity battery through a heat transfer pipe on the polarity terminal of the large-capacity battery. The step d can be performed after the step c or during the step c (i.e., the heating step is performed after the over-discharge step or during the over-discharge process).

[0341] Of course, the step d can be performed after the step b or during the step b (i.e., the heating step is performed after the lithium supplement step or during the lithium supplement process).

[0342] Specifically, the heat transfer pipe transfers heat from the polarity terminal of the large-capacity battery to the electrode assembly in each single battery, changes the lattice structure of the positive and negative electrode materials in the electrode assembly of each single battery to restore the original structure, and enables the active lithium ions to be smoothly inserted or extracted from the positive and negative electrodes during the charging and discharging process, thereby improving the repair effect of the large-capacity battery.

[0343] Preferably, the heating temperature needs to be controlled between 45℃ and 60℃.

[0344] The method of the present application is also applicable to existing square shell lithium ion batteries. A plurality of commercially available square shell lithium ion batteries with similar initial capacities can be selected, and several square shell lithium ion batteries are modified to set a lithium supplement device on the lithium ion battery.

[0345] The square shell lithium ion battery is repaired in the following ways:

[0346] Method 1: After the supplement and replacement of the liquid and the exhaust are performed, the lithium supplement is performed.

[0347] Method 2: After the lithium supplement is performed, the supplement and replacement of the liquid and the exhaust are performed.

[0348] Method 3: On the basis of method 1, over-discharge is added. The over-discharge can be performed before the supplement and replacement of the liquid, between the supplement and replacement of the liquid and the lithium supplement, or simultaneously with the lithium supplement.

[0349] Method 4: On the basis of method 2, over-discharge is added. The over-discharge can be performed before the lithium supplement, between the lithium supplement and the supplement and replacement of the liquid, or simultaneously with the lithium supplement.

[0350] Method 5: On the basis of method 3 and method 4, heating is added. The heating can be performed after the over-discharge, or simultaneously with the over-discharge.

[0351] Example 12

[0352] This example is to repair the square shell lithium ion battery according to method 1, and the specific process is as follows:

[0353] Seven 20 Ah square shell lithium ion batteries with similar initial capacities are selected, and three of them are modified to set a lithium supplement device on the lithium ion battery.

[0354] Three lithium ion batteries with the lithium supplement device are used as sample 1 to sample 3 of this example. When the capacity decays to about 90%, the repair process of first supplement and replacement of the liquid and then lithium supplement is performed, and then normal charging and discharging is performed for 400 times.

[0355] Three lithium ion batteries without the lithium supplement device are used as comparative sample 1 to comparative sample 3 of this example. When the capacity decays to about 90%, only the repair of supplement and replacement of the liquid is performed, and then normal charging and discharging is performed for 400 times.

[0356] One lithium ion battery without the lithium supplement device is used as comparative sample 4 of this example without any repair.

[0357] The specific test data of this example is shown in Table 12, Table 13 and Figure 16.

[0358] Table 12: Capacity data of each sample Table 12: Capacity data of each sample

[0359] Table 13 Capacity retention data of each sample

[0360] As can be seen from Table 12, Table 13 and Figure 16, after one repair is completed, the capacity of sample 1, sample 2 and sample 3 of the embodiment during 1-100 charge-discharge cycles is greater than the initial capacity (i.e. the capacity after repair is significantly improved), while the capacity of comparative sample 1 to comparative sample 4 does not improve after repair.

[0361] It can be proved that the repair scheme of supplementing liquid and lithium in the embodiment can not only improve the capacity of lithium ion battery, but also slow down the decline trend of capacity retention rate compared with the scheme of supplementing liquid alone and without any repair operation;

[0362] When the lithium ion battery after repair is attenuated in capacity after a period of charge-discharge cycle, the method of the embodiment can be used for multiple repairs.

[0363] Embodiment 13

[0364] In this embodiment, the second large-capacity battery structure is taken as an example to describe the specific repair process in detail:

[0365] Step 1: Real-time detection of large-capacity battery, if the capacity of large-capacity battery is detected to be attenuated to X or after Y times of charge-discharge cycle are performed, at least step 2 is performed once; wherein 70%≤X≤98%; Y≥200 times;

[0366] Step 2: Repair process;

[0367] Step a: supplementing liquid to the large-capacity battery through the functional interface, and simultaneously using the functional interface to exhaust the large-capacity battery;

[0368] The specific process of this step a is: opening the valves on the gas channel of the functional interface and the external gas pipe, and the electrolyte channel of the functional interface and the external liquid pipe, and the electrolyte passes through the external liquid pipe and the electrolyte channel into the large-capacity battery in turn, and the gas in the large-capacity battery passes through the gas channel and the external gas pipe to exhaust the large-capacity battery;

[0369] In this embodiment, the functional interface of the large-capacity battery can be used to supplement liquid and exhaust the large-capacity battery online, and through the step of supplementing liquid and exhausting at the same time, the consumption of electrolyte in the large-capacity battery is compensated, the conductivity of lithium ions is improved, and the large-capacity battery is exhausted, which reduces the influence of excessive gas pressure on the performance of the large-capacity battery, and also makes the liquid supplementing process more smooth;

[0370] In this embodiment, the replenishing step can be replaced by a liquid replacement step. The specific process of liquid replacement is as follows: first, open the valves of the gas channel of the external gas pipe and the functional interface, and the electrolyte channel of the external liquid pipe and the functional interface, inject inert gas into the large capacity battery through the external gas pipe and the gas channel in sequence, and discharge the old electrolyte in the large capacity battery through the electrolyte channel and the external liquid pipe; then, the new electrolyte enters the large capacity battery through the external liquid pipe and the electrolyte channel in sequence, and the gas in the large capacity battery is discharged through the gas channel and the external gas pipe in sequence, thereby completing the replacement of the electrolyte in the large capacity battery. Compared with the replenishing step, the liquid replacement process can also remove impurities in the old electrolyte, thereby purifying the electrolyte.

[0371] Step b: performing over-discharge treatment on the large capacity battery; the over-discharge treatment can reduce the thickness of the SEI film, activate the dead lithium in the large capacity battery, and reduce the ion impedance.

[0372] The over-discharge step can be performed before or after the replenishing step, or during the replenishing step. It should be noted that, during the over-discharge process, the gas production in the large capacity battery increases compared with the normal operation of the large capacity battery. If the over-discharge step is performed after the replenishing step, a secondary gas discharge step for the large capacity battery is required during or after the over-discharge step to avoid affecting the cycle performance of the large capacity battery due to excessive gas pressure in the large capacity battery after repair.

[0373] Since the electrolyte is consumed quickly during the over-discharge process, a replenishing step can be added when the secondary gas discharge step for the large capacity battery is performed after the over-discharge step.

[0374] The cut-off voltage of the over-discharge treatment for the large capacity battery needs to be controlled between 0.01 V and 2.4 V; specifically, the cut-off voltage of the over-discharge treatment can be selected from a high voltage range, for example, between 1.0 V and 2.4 V, or a medium voltage range, for example, between 0.1 V and 0.9 V, or a low voltage range, for example, between 0.01 V and 0.09 V.

[0375] In this embodiment, step 2 is performed in the order of performing step b after performing step a. The main reason is that replenishing before over-discharge can ensure that the large capacity battery has sufficient electrolyte during the over-discharge process. In some other embodiments, over-discharge can be performed before replenishing.

[0376] Embodiment 14

[0377] This embodiment is based on embodiment 13, and step c is added: heating treatment is performed on the large capacity battery through the heat transfer pipe on the polar terminal of the large capacity battery. This step d can be performed after step c, or it can be performed during the execution of step c (that is, the heating step is performed after the over-discharge step or during the over-discharge process);

[0378] Of course, step d can be performed after step b or during the execution of step b (that is, the heating step is performed after the lithium supplement step or during the lithium supplement process);

[0379] Specifically, the heat transfer pipe transmits heat from the polar terminal of the large capacity battery to the electrode assembly in each single battery, changes the lattice structure of the positive and negative electrode materials in each single battery electrode assembly to restore it to the original structure, so that the active lithium ions can be smoothly embedded or removed from the positive and negative electrodes during the charging and discharging process, thereby improving the repair effect of the large capacity battery.

[0380] Preferably, the heating temperature needs to be controlled between 45°C and 60°C.

[0381] The method of the present application is also applicable to existing square shell lithium ion batteries. A plurality of commercially available square shell lithium ion batteries with similar initial capacity can be selected, and several square shell lithium ion batteries can be modified to set a lithium supplement device on the lithium ion battery;

[0382] The square shell lithium ion battery is repaired in the following ways:

[0383] Method 1: After the supplement and replacement of the liquid and the exhaust, over-discharge is performed;

[0384] Method 2: After over-discharge, the supplement and replacement of the liquid are performed. In this method, the exhaust is performed during or after over-discharge;

[0385] Method 3: Based on method 1 and method 2, heating is added. The heating can be performed after over-discharge, or over-discharge and heating can be performed simultaneously.

[0386] Method 4: Based on method 1 and method 2, secondary exhaust is added. The secondary exhaust can be performed after over-discharge, or over-discharge and secondary exhaust can be performed simultaneously.

[0387] Method 5: Based on method 4, secondary liquid supplement is added. The secondary liquid supplement and the secondary exhaust are performed simultaneously.

[0388] Embodiment 15

[0389] Seven 20Ah square shell lithium ion batteries with similar initial capacity are selected, wherein

[0390] Two of the lithium ion batteries were taken as sample 1 and sample 2 in this embodiment, and when the capacity was attenuated to about 90%, the over-discharge operation was performed to restore the normal charge-discharge cycle;

[0391] Two of the lithium ion batteries were taken as sample 3 and sample 4 in this embodiment, and when the capacity was attenuated to about 90%, the over-discharge operation was performed while the exhaust operation was performed, and after the over-discharge and exhaust operation was completed, the liquid supplement operation was performed to restore the normal charge-discharge cycle;

[0392] Two of the lithium ion batteries were taken as sample 5 and sample 6 in this embodiment, and when the capacity was attenuated to about 90%, the exhaust operation was performed after the over-discharge operation was completed, and then the liquid supplement operation was performed to restore the normal charge-discharge cycle;

[0393] Two of the lithium ion batteries were taken as sample 7 and sample 8 in this embodiment, and when the capacity was attenuated to about 90%, the liquid supplement and exhaust operation was performed on the battery, and then the over-discharge operation was performed to restore the normal charge-discharge cycle;

[0394] Two of the lithium ion batteries were taken as sample 1 and sample 2 in this embodiment, and when the capacity was attenuated to about 90%, the over-discharge operation was performed to restore the normal charge-discharge cycle;

[0395] The specific test data of this embodiment is shown in Table 14, Table 15 and Figure 17.

[0396] Table 14: Capacity data of each sample

[0397] Table 15: Capacity retention rate data of each sample

[0398] As can be seen from Table 14, Table 15 and Figure 17, after the repair is completed, the capacity of sample 1 to sample 8 continues to rise and then slowly declines when the charge-discharge cycle is performed 1 to 100 times, and the capacity of sample 3 to sample 8 is higher than that of sample 1 and sample 2, and the capacity of sample 1 and sample 2 is always declining; thus it can be proved that the over-discharge combined with liquid supplement in this embodiment can obtain better repair effect compared with the over-discharge alone scheme.

[0399] When the repaired lithium ion battery is attenuated again after a period of charge-discharge cycle, it can be repaired multiple times by the method of this embodiment.

[0400] Embodiment 16

[0401] In this embodiment, the second large-capacity battery structure is taken as an example to describe the specific repair process in detail:

[0402] Step 1: Real-time detection of large capacity battery, since the SEI film will thicken after the large capacity battery is operated for a long time again, the SEI film is too thick, which will cause the ion impedance to increase on the one hand, and the active lithium ions to decrease on the other hand; if the capacity of the large capacity battery is detected to decay to X or after Y times of charge-discharge cycles are performed, at least one step 2 is performed; wherein 70%≤X≤98%; Y≥200 times;

[0403] Step 2: Repair process

[0404] Step a: over-discharge the large capacity battery

[0405] When the over-discharge treatment is performed on the large capacity battery, the cut-off voltage of the over-discharge needs to be controlled between 0.01V and 2.4V; specifically, the cut-off voltage of the over-discharge can be selected in a high voltage area, for example: between 1.0V and 2.4V, or in a medium voltage area, for example: between 0.1V and 0.9V, or in a low voltage area, for example: between 0.01V and 0.09V.

[0406] Step b: supplement lithium to the large capacity battery through the lithium supplement device.

[0407] The specific process of this step b is: turn on the switch, adjust the resistance value of the variable resistor, control the lithium supplement current to be 1mA, and realize the lithium supplement to the large capacity battery.

[0408] In this embodiment, step 2 is performed in the order of performing step a and then performing step b, in some other embodiments, the lithium can be supplemented first and then over-discharged, of course, step a and step b can also be performed at the same time.

[0409] Step c: exhaust the large capacity battery through the functional interface; this step can avoid the problem that the excessive gas pressure in the large capacity battery affects the cycle performance of the large capacity battery;

[0410] The specific process of this step c is: open the valve on the gas passage of the external gas pipe and the functional interface, and the gas in the large capacity battery is sequentially discharged out of the large capacity battery through the gas passage and the external gas pipe; since the over-discharge will aggravate the generation of gas in the large capacity battery, therefore, step c (exhaust) is performed synchronously with step a (over-discharge) in this embodiment;

[0411] In some other embodiments, step c (exhaust) can also be performed after step a (over-discharge) is performed.

[0412] Embodiment 17

[0413] This embodiment is based on embodiment 16 and adds step d: performing a heating treatment on the large capacity battery through the heat transfer pipe on the polar terminal of the large capacity battery. This step d can be performed after step c or during the performance of step c (i.e., the heating step is performed after the over-discharge step or during the over-discharge process);

[0414] Of course, step d can also be performed after step b or during the performance of step b (i.e., the heating step is performed after the lithium supplement step or during the lithium supplement process);

[0415] Specifically, the heat transfer pipe transfers heat from the polar terminal of the large capacity battery to the electrode assembly in each single battery, causing the lattice structure of the positive and negative electrode materials in each single battery electrode assembly to change and return to the original structure, allowing active lithium ions to smoothly embed or extract positive and negative electrodes during the charging and discharging process, thereby improving the repair effect of the large capacity battery.

[0416] The method of the present application is also applicable to existing square shell lithium ion batteries. A plurality of commercially available square shell lithium ion batteries with similar initial capacity can be selected, and several square shell lithium ion batteries can be modified to set a lithium supplement device on the lithium ion battery;

[0417] The square shell lithium ion battery is repaired in the following ways:

[0418] Method 1: Perform over-discharge and exhaust after lithium supplement;

[0419] Method 2: Perform over-discharge and exhaust after lithium supplement;

[0420] Method 3: On the basis of method 1 and method 2, heating is added. The heating can be performed after over-discharge or simultaneously with over-discharge.

[0421] Embodiment 18

[0422] Seven 20Ah square shell lithium ion batteries with similar initial capacity are selected, and four of them are modified to set a lithium supplement device on the lithium ion battery;

[0423] Two of the lithium ion batteries with the lithium supplement device are used as test sample 1 and test sample 2 of this embodiment. When the capacity decays to about 90%, over-discharge and exhaust are performed after lithium supplement repair, and then normal charging and discharging is performed 480 times;

[0424] The other two lithium ion batteries with the lithium supplement device are used as comparative sample 3 and comparative sample 4 of this embodiment. When the capacity decays to about 90%, only lithium supplement repair is performed, and then normal charging and discharging is performed 480 times;

[0425] The lithium ion battery without lithium supplement device in which two are taken as comparative sample 1 and comparative sample 2 of the embodiment, when the capacity attenuation is about 90%, only after over-discharge repair, normal charge and discharge is performed 480 times;

[0426] Another lithium ion battery without lithium supplement device is taken as comparative sample 5 of the embodiment, without performing any repair;

[0427] The specific test data of the embodiment is shown in table 16, table 17 and figure 18.

[0428] Table 16: Capacity data of each sample

[0429] Table 17: Capacity retention rate data of each sample

[0430] From table 16, table 17 and figure 18, it can be seen that after one repair, the capacity retention rate of test sample 1, test sample 2, comparative sample 1, comparative sample 2 and comparative sample 3 is basically greater than that of comparative sample 4 and comparative sample 5 (comparative sample 3 has a higher capacity retention rate before 480 charge and discharge cycles, and the capacity retention rate is less than that of comparative sample 4 and comparative sample 5 after 480 charge and discharge cycles, the analysis reason is that the negative electrode lithium precipitation leads to it); it can be concluded that over-discharge, single over-discharge and single lithium supplement can realize the repair of lithium ion battery;

[0431] And after 480 charge and discharge cycles, the capacity retention rate of test sample 1 and test sample 2 is slightly greater than that of comparative sample 1, comparative sample 2 and comparative sample 3. It can be proved that the over-discharge and lithium supplement method of the embodiment can obtain better repair effect compared with the single over-discharge and single lithium supplement method;

[0432] When the repaired lithium ion battery capacity attenuates again after a period of charge and discharge cycle, it can also be repaired multiple times by the method of the embodiment.

[0433] Embodiment 19

[0434] Step 1: real-time detection of large capacity battery, if the capacity of the large capacity battery is detected to be attenuated to X1 or over Y1 charge and discharge cycles are performed, at least once step 2 is performed; wherein 85%≤X1≤98%; Y1≥200 times;

[0435] Step 2: First stage online repair; the single cells of the large capacity battery consume a part of active lithium ions in formation, and as long time charging and discharging cycle, the electrolyte in the large capacity battery continuously decomposes and consumes, the active lithium ions continuously decrease, and the gas pressure in the large capacity battery continuously increases, resulting in the capacity of the large capacity battery to decay;

[0436] The specific way of this stage repair is:

[0437] Step a: directly supplementing the electrolyte into the large capacity battery by using the functional interface, and simultaneously discharging the gas in the large capacity battery by using the functional interface;

[0438] The specific process of this step a is: opening the valves on the gas channel of the external gas pipe and the functional interface, and the electrolyte channel of the external liquid pipe and the functional interface, the electrolyte enters the large capacity battery through the external liquid pipe and the electrolyte channel in turn, and the gas in the large capacity battery is discharged through the gas channel and the external gas pipe in turn; this embodiment can realize the supplement of the electrolyte and the discharge of the gas in the large capacity battery by using the functional interface of the large capacity battery, and through the step of supplementing the electrolyte and discharging the gas at the same time, the consumption of the electrolyte in the large capacity battery is compensated, the conductivity of lithium ions is improved, the gas pressure in the large capacity battery is reduced, and the influence of the large gas pressure on the performance of the large capacity battery is reduced, and the supplement process is more smooth;

[0439] In this embodiment, the supplement step can be replaced by the replacement step, and the specific process of the replacement is: first, open the valves on the gas channel of the external gas pipe and the functional interface, and the electrolyte channel of the external liquid pipe and the functional interface, inject inert gas into the large capacity battery through the external gas pipe and the gas channel in turn, and discharge the old electrolyte in the large capacity battery through the electrolyte channel and the external liquid pipe; then, the new electrolyte enters the large capacity battery through the external liquid pipe and the electrolyte channel in turn, and the gas in the large capacity battery is discharged through the gas channel and the external gas pipe in turn, and then the replacement of the electrolyte in the large capacity battery is completed. Compared with the supplement, the replacement process can also take away the impurities in the old electrolyte, and realize the purification of the electrolyte;

[0440] Step 3: real-time detection of the large capacity battery, if the capacity and capacity retention rate of the large capacity battery have no obvious improvement after the first stage online repair, or the capacity of the large capacity battery is detected to decay to X2, or the large capacity battery is executed Y2 times of charging and discharging cycle, as the SEI film thickens after the long-term operation of the large capacity battery, the SEI film is too thick, which on the one hand increases the ion impedance, and on the other hand reduces the active lithium ions, so at least once step 4 is executed; wherein, 70%≤X2≤95%; Y2>Y1;

[0441] Step 4: second stage online repair;

[0442] Step b: over-discharge the large capacity battery; over-discharging the large capacity battery can reduce the thickness of the SEI film, activate the dead lithium in the large capacity battery, and reduce the ion impedance;

[0443] The over-discharge cut-off voltage when over-discharging the large capacity battery needs to be controlled between 0.01V and 2.4V; specifically, the over-discharge cut-off voltage can be selected in the high voltage region, for example, between 1.0V and 2.4V, or in the medium voltage region, for example, between 0.1V and 0.9V, or in the low voltage region, for example, between 0.01V and 0.09V.

[0444] Step c: supplement lithium to the large capacity battery through the lithium supplement device.

[0445] The specific process of this step c is to turn on the switch, adjust the resistance value of the variable resistor, control the lithium supplement current to be 1mA, and realize the lithium supplement to the large capacity battery.

[0446] In this embodiment, step 4 is performed in the order of step b and step c, or step b and step c can be performed synchronously. In some other embodiments, lithium can be supplemented first and then over-discharged.

[0447] Embodiment 20

[0448] This embodiment is based on embodiment 19 and adds step d: a step of performing heating treatment on the large capacity battery through the heat transfer pipe on the polarity terminal of the large capacity battery. Step d can be performed after step b or during the execution of step b (i.e., the heating step is performed after the over-discharge step or during the over-discharge process).

[0449] Of course, step d can also be performed after step c or during the execution of step c (i.e., the heating step is performed after the lithium supplement step or during the lithium supplement process).

[0450] Specifically, the heat transfer pipe transmits heat from the polarity terminal of the large capacity battery to the electrode assembly in each single battery, so that the crystal lattice structure of the positive and negative electrode materials in each single battery electrode assembly changes and returns to the original structure, so that the active lithium ions can be smoothly embedded or removed from the positive and negative electrodes during the charging and discharging process, thereby improving the repair effect of the large capacity battery.

[0451] Preferably, the heating temperature needs to be controlled between 45°C and 60°C.

[0452] Embodiment 21

[0453] This embodiment is based on embodiment 20 and adds step e: performing liquid supplement or replacement on the large capacity battery through the functional interface, and simultaneously performing secondary degassing on the large capacity battery through the functional interface.

[0454] The step e can be performed before step b (that is, liquid injection, exhaust before over-discharge), the purpose of which is that after the large-capacity battery is repaired in the first stage and then undergoes long-term charging and discharging, the electrolyte is decomposed and consumed, and the gas pressure in the large-capacity battery is relatively large. In order to achieve better over-discharge effect in the subsequent process, it is necessary to perform liquid supplement and exhaust on the large-capacity battery before over-discharge;

[0455] The step e can be performed after step b (that is, liquid replacement and exhaust after over-discharge), the purpose of which is that after over-discharge, the consumption of electrolyte is large, and the gas production is large. In addition, impurities may exist in the electrolyte due to the thinning of the SEI film during over-discharge. Therefore, after over-discharge, liquid replacement can be performed to remove impurities in the old electrolyte, improve the performance of the electrolyte in the large-capacity battery, and exhaust the gas generated during the over-discharge process. At the same time, due to the newly injected electrolyte in the large-capacity battery at this time, the conductivity is greatly improved, which provides strong support for the subsequent lithium supplement process.

[0456] It should be noted that the specific process of liquid supplement and replacement in step e is basically the same as the process in step a of embodiment 1.

[0457] Embodiment 22

[0458] In this embodiment, the second large-capacity battery structure is taken as an example to describe the specific repair process in detail:

[0459] Step 1: Real-time detection of the large-capacity battery. If the capacity of the large-capacity battery is detected to be attenuated to X1 or the over-discharge is performed Y1 times, at least step 2 is performed once; wherein 85%≤X1≤98%; Y1≥200 times;

[0460] Step 2: First-stage online repair; the single battery of the large-capacity battery will consume a part of active lithium ions during formation and long-term charging and discharging, resulting in capacity attenuation of the large-capacity battery;

[0461] The repair method in this stage is: step a: supplement lithium to the large-capacity battery through the lithium supplement device;

[0462] The specific process of step a is: turn on the switch, adjust the resistance value of the variable resistor, control the lithium supplement current in the appropriate range, and then realize the lithium supplement of the large-capacity battery;

[0463] Step 3: Real-time detection of the large capacity battery. If the capacity and capacity retention of the large capacity battery do not significantly improve after the first stage of online repair, or if the capacity of the large capacity battery decays to X2, or if the large capacity battery has performed Y2 times of charge and discharge cycles, then at least one step 4 is performed. Wherein, 70%≤X2≤95%; Y2>Y1.

[0464] Step 4: Second stage of online repair.

[0465] Step b: Perform over-discharge on the large capacity battery.

[0466] Perform over-discharge on the large capacity battery. Over-discharge processing of the large capacity battery can reduce the thickness of the SEI film, activate the dead lithium in the large capacity battery, and reduce the ion impedance.

[0467] The cutoff voltage of over-discharge during over-discharge processing of the large capacity battery needs to be controlled between 0.01V and 2.4V. Specifically, the cutoff voltage of over-discharge can be selected in the high voltage region, for example: between 1.0V and 2.4V, or in the medium voltage region, for example: between 0.1V and 0.9V, or in the low voltage region, for example: between 0.01V and 0.09V.

[0468] Step c: Replace the liquid in the large capacity battery through the functional interface, and simultaneously use the functional interface to exhaust the large capacity battery.

[0469] The specific process of step c is as follows: first, open the valves on the gas channel of the external gas pipe and the functional interface, and the electrolyte channel of the external liquid pipe and the functional interface, inject inert gas into the large capacity battery through the external gas pipe and the gas channel in turn, and the old electrolyte in the large capacity battery is discharged from the electrolyte channel and the external liquid pipe; then, the new electrolyte enters the large capacity battery through the external liquid pipe and the electrolyte channel in turn, and the gas in the large capacity battery is discharged from the large capacity battery through the gas channel and the external gas pipe, thereby completing the replacement of the electrolyte in the large capacity battery.

[0470] In this embodiment, step 4 is performed in the order of step b and step c. The main reason is that the consumption of electrolyte is large after over-discharge, and the gas production is large. In addition, impurities may exist in the electrolyte due to the thinning of the SEI film during over-discharge. Therefore, after over-discharge, the replacement of the electrolyte can remove the impurities in the old electrolyte, improve the performance of the electrolyte in the large capacity battery, and discharge the gas generated during the over-discharge process. At the same time, the conductivity of the newly injected electrolyte in the large capacity battery is greatly improved.

[0471] In some other embodiments, the liquid replacement in step c can also be a liquid supplement;

[0472] In some other embodiments, the liquid replacement can also be supplemented before the over-discharge; the purpose of this repair process is that after the large-capacity battery is repaired in the first stage and then undergoes long-term charging and discharging, the electrolyte is decomposed and consumed, and the air pressure in the large-capacity battery is also relatively large. In order to achieve better over-discharge effect in the future, the large-capacity battery needs to be supplemented with liquid replacement and air exhaust before over-discharge.

[0473] Embodiment 23

[0474] This embodiment is based on embodiment 22 and adds step d: a step of performing heating treatment on the large-capacity battery through the heat transfer pipe on the polarity terminal of the large-capacity battery. This step d can be performed after step b, or it can be performed during the execution of step b (that is, the heating step is performed after the over-discharge step or during the over-discharge process);

[0475] Of course, step d can also be performed after step c (that is, the heating step is performed after the lithium supplement step or during the lithium supplement process);

[0476] Specifically, the heat transfer pipe transmits heat from the polarity terminal of the large-capacity battery to the electrode assembly in each single battery, so that the crystal structure of the positive and negative electrode materials in each single battery electrode assembly changes to restore to the original structure, so that the active lithium ions can smoothly embed or extract the positive and negative electrodes in the charging and discharging process, thereby improving the repair effect of the large-capacity battery.

[0477] Preferably, the heating temperature needs to be controlled between 45°C and 60°C.

[0478] Embodiment 24

[0479] This embodiment is based on embodiment 22 or 23, and specifically adds step e: a secondary lithium supplement to the large-capacity battery through the lithium supplement device in step 4; the specific process of this step e is: turn on the switch, adjust the resistance value of the variable resistor, control the lithium supplement current to be 1mA, and realize the lithium supplement to the large-capacity battery.

[0480] Embodiment 25

[0481] This embodiment is based on embodiment 22 or embodiment 23 or embodiment 24, and specifically adds step f: supplementing liquid to the large-capacity battery through the functional interface, and simultaneously using the functional interface to exhaust the large-capacity battery in step 2.

[0482] The process is specifically: opening the gas passage of the external gas pipe and the functional interface, and the valve on the electrolyte passage of the external liquid pipe and the functional interface, the electrolyte passes through the external liquid pipe and the electrolyte passage into the large capacity battery in turn, and the gas in the large capacity battery is discharged from the large capacity battery through the gas passage and the external gas pipe in turn.

Claims

1. A method of lithium-ion battery capacity restoration, characterized by, By repairing lithium-ion batteries with capacity decay, the charge-discharge cycle performance of lithium-ion batteries can be extended.

2. The lithium-ion battery capacity restoration method of claim 1, wherein, Includes steps a and b; Step a is as follows: over-discharge the lithium-ion battery to be repaired, remove the gas inside the lithium-ion battery cavity, and inject electrolyte into the cavity; Step b is to replenish lithium on the electrode of the lithium-ion battery to be repaired using a lithium replenishment electrode.

3. The lithium-ion battery capacity restoration method of claim 2, wherein: Execute step a first, then execute step b.

4. The lithium-ion battery capacity restoration method of claim 3, wherein: In step b, a lithium replenishment electrode is used to perform high-frequency lithium replenishment on the lithium-ion battery electrode to be repaired.

5. The lithium-ion battery capacity restoration method of claim 4, wherein: High-frequency lithium replenishment is performed on the lithium-ion battery electrode to be repaired based on the following charge and discharge parameters: control the lithium replenishment current, and perform a cycle of 1C charging for 15s, resting for 15s, 1C discharging for 15s, and resting for 15s. Repeat this cycle for 12h to 24h.

6. The lithium-ion battery capacity restoration method of claim 1, wherein: Steps a and b are executed synchronously. When step a stops, the lithium replenishment current is controlled, and step b is executed continuously for the set time.

7. The lithium-ion battery capacity restoration method of any one of claims 1 to 6, wherein: In step b, the lithium replenishment area of ​​the lithium replenishment electrode is set inside the lithium-ion battery casing to be repaired, and the wiring terminals of the lithium replenishment electrode are placed outside the lithium-ion battery casing to be repaired. During lithium replenishment, the wiring terminals of the lithium replenishment electrode are electrically connected to the polarity terminals of the lithium-ion battery to be repaired, so that the lithium replenishment electrode replenishes lithium to the electrode of the lithium-ion battery to be repaired.

8. The lithium-ion battery capacity restoration method of claim 7, wherein: The lithium replenishment electrode is placed between the electrode assembly and the base plate inside the lithium-ion battery casing to be repaired.

9. The lithium-ion battery capacity restoration method of claim 8, wherein: The terminals of the lithium-ion battery being repaired are electrically connected to the polarity terminals of the lithium-ion battery being repaired via a switch, a rheostat, and a diode.

10. The lithium-ion battery capacity restoration method of claim 9, wherein: The lithium-filling electrode is a lithium sheet or other lithium-rich material.

11. The lithium-ion battery capacity restoration method of claim 10, wherein: The lithium-rich material is a lithium-rich anode sheet.

12. The lithium-ion battery capacity restoration method of claim 1, wherein, Includes the following steps: Perform an over-discharge step on the old lithium-ion battery; perform a heating step on the old lithium-ion battery.

13. The lithium-ion battery capacity restoration method of claim 12, wherein: It also includes a fluid replenishment step.

14. The lithium-ion battery capacity restoration method of claim 13, wherein: It also includes the exhaust process.

15. The lithium-ion battery capacity restoration method of claim 13, wherein: The electrolyte injected in the replenishment step includes a solvent and a lithium salt; the solvent is a mixed solution of ethylene carbonate and ethyl methyl carbonate in a ratio of 4:6, and the lithium salt is 1.2 mol of lithium difluorosulfonyl imide.

16. The lithium-ion battery capacity restoration method of any one of claims 12 to 15, wherein: It also includes performing a clamping step on the selected lithium batteries to be repaired.

17. The lithium-ion battery capacity restoration method of claim 12, wherein: The discharge cutoff voltage range is 0.01V to 2.4V.

18. The lithium-ion battery capacity restoration method of claim 17, wherein: The discharge cutoff voltage is 0.01V.

19. The lithium-ion battery capacity restoration method of claim 12, wherein: The heating temperature range is 40 to 60°C.

20. The lithium-ion battery capacity restoration method of claim 19, wherein: The heating temperature is 50°C.

21. The lithium-ion battery capacity restoration method of claim 1, wherein, The lithium-ion battery is a high-capacity battery. By monitoring the high-capacity battery in real time, online repair can be performed on high-capacity batteries with capacity degradation.

22. The lithium-ion battery capacity restoration method according to claim 21, characterized in that, Includes the following steps: Step 1: Real-time monitoring of the large-capacity battery. If the battery capacity is detected to have decreased to X or after Y charge-discharge cycles, Step 2 shall be executed at least once; 85% ≤ X ≤ 98%; Y ≥ 200 cycles; Step 2: Repair process; Step a: Perform electrolyte replenishment or replacement, and venting on the large-capacity battery via the functional interface; Step b: Replenish lithium in the large-capacity battery using a lithium replenishment device.

23. The lithium-ion battery capacity restoration method of claim 22, wherein, Step 2 further includes step c: performing over-discharge treatment on the large-capacity battery.

24. The lithium-ion battery capacity restoration method of claim 23, wherein, Step 2 further includes step d: performing a heating treatment on the large-capacity battery through the heat transfer tube on the polar terminal of the large-capacity battery.

25. The lithium-ion battery capacity restoration method of claim 24, wherein, The functional interface is a columnar body, and the columnar body is internally provided with a gas passage connecting the gas sharing chamber of the large capacity battery and an external gas pipe and an electrolyte passage connecting the electrolyte sharing chamber of the large capacity battery and an external liquid pipe, and the gas passage and the electrolyte passage are isolated from each other.

26. The lithium-ion battery capacity restoration method of claim 25, wherein, The lithium supplement device comprises a lithium source, a lithium supplement wire, a variable resistor and a switch. The lithium source is arranged in the large capacity battery and is soaked in the electrolyte. One end of the lithium supplement wire is electrically connected with the lithium source, and the other end is used for being connected with a polar terminal of the large capacity battery, and the lithium supplement wire is provided with the switch and the variable resistor. The switch is used for turning on or cutting off the lithium supplement wire.

27. The lithium-ion battery capacity restoration method of claim 26, wherein, The lithium source comprises two layers of copper mesh layers and a metal lithium layer arranged between the two layers of copper mesh layers.

28. The lithium-ion battery capacity restoration method of claim 23, wherein: The cutoff voltage of the over-discharge is 0.01V to 2.4V.

29. The lithium-ion battery capacity restoration method of claim 24, wherein: The heating temperature range is 45 to 60℃.

30. The lithium-ion battery capacity restoration method of claim 20, wherein, The method comprises the following steps: Step 1: real-time detection of the large capacity battery, if the capacity of the large capacity battery is detected to be attenuated to X or the over-discharge is performed for Y times, at least step 2 is performed once; 70%≤X≤98%; Y≥200 times; Step 2: repair process; Step a: supplementing or replacing the electrolyte of the large capacity battery through the functional interface, and exhausting the large capacity battery through the functional interface; Step b: performing over-discharge treatment on the large capacity battery.

31. The lithium-ion battery capacity restoration method of claim 30, wherein, The step 2 further comprises step c: heating treatment on the large capacity battery through the heat transfer pipe on the polar terminal of the large capacity battery.

32. The lithium-ion battery capacity restoration method of claim 30 or 31, wherein, The step 2 further comprises step d: secondary exhaust treatment on the large capacity battery.

33. The lithium-ion battery capacity restoration method of claim 32, wherein, The step d further comprises secondary supplementing of the electrolyte of the large capacity battery through the functional interface.

34. The lithium-ion battery capacity restoration method of claim 33, wherein, The functional interface is a columnar body, and the columnar body is internally provided with a gas passage connecting the gas sharing chamber of the large capacity battery and an external gas pipe and an electrolyte passage connecting the electrolyte sharing chamber of the large capacity battery and an external liquid pipe, and the gas passage and the electrolyte passage are isolated from each other.

35. The lithium-ion battery capacity restoration method of claim 30, wherein: The cutoff voltage of the over-discharge is 0.01V to 2.4V.

36. The lithium-ion battery capacity restoration method of claim 31, wherein: The heating temperature range is 45 to 60℃.

37. The lithium-ion battery capacity restoration method of claim 20, wherein, The method comprises the following steps: Step 1: real-time detection of the large capacity battery, if the capacity of the large capacity battery is detected to be attenuated to X or the over-discharge is performed for Y times, at least step 2 is performed once; 70%≤X≤98%; Y≥200 times; Step 2: repair process; Step a: over-discharge treatment on the large capacity battery; Step b: lithium supplement on the large capacity battery through the lithium supplement device; Step c: exhaust of the large capacity battery through the functional interface.

38. The lithium-ion battery capacity restoration method of claim 37, wherein, The step 2 further comprises step d: heating treatment on the large capacity battery through the heat transfer pipe on the polar terminal of the large capacity battery.

39. The lithium-ion battery capacity restoration method of claim 37 or 38, wherein, The lithium supplement device comprises a lithium source, a lithium supplement wire, a variable resistor and a switch. The lithium source is arranged in the large capacity battery and is soaked in the electrolyte. One end of the lithium supplement wire is electrically connected with the lithium source, and the other end is used for being connected with a polar terminal of the large capacity battery, and the lithium supplement wire is provided with the switch and the variable resistor.

40. The lithium-ion battery capacity restoration method of claim 39, wherein, The lithium source comprises two layers of copper mesh layers and a metal lithium layer arranged between the two layers of copper mesh layers.

41. The lithium-ion battery capacity restoration method of claim 37, wherein: The cutoff voltage of the over-discharge is 0.01V to 2.4V.

42. The lithium-ion battery capacity restoration method of claim 38, wherein: The heating temperature range is 45 to 60℃.

43. The lithium-ion battery capacity restoration method of claim 20, wherein, The method comprises the following steps: Step 1: Real-time detection of the large capacity battery. If the capacity of the large capacity battery is detected to decay to X1 or the number of charge-discharge cycles is detected to be Y1, at least one step 2 is performed; wherein 85%≤X1≤98%; Y1≥200 times; Step 2: First stage online repair Step a: Directly supplementing the large capacity battery with a functional interface, and exhausting the large capacity battery with the functional interface; Step 3: Real-time detection of the large capacity battery. If the large capacity battery is detected to reach the second repair condition, at least one step 4 is performed; Step 4: Second stage online repair Step b: Over-discharging the large capacity battery; Step c: Supplementing lithium to the large capacity battery through a lithium supplementing device; The second repair condition is the following two cases: Case 1: The capacity and capacity retention rate of the large capacity battery do not significantly improve after the first stage online repair; Case 2: The capacity of the large capacity battery decays to X2 or the number of charge-discharge cycles is Y2; wherein 70%≤X2≤95%; Y2>Y1.

44. The lithium-ion battery capacity restoration method of claim 43, wherein, The step 4 further comprises a step d: heating the large capacity battery through a heat transfer pipe on the polarity terminal of the large capacity battery.

45. The lithium-ion battery capacity restoration method of claim 43 or 44, wherein, The step 4 further comprises a step e: supplementing or replacing the electrolyte of the large capacity battery through the functional interface, and exhausting the large capacity battery through the functional interface.

46. The lithium-ion battery capacity restoration method of claim 45, wherein, The functional interface is a columnar body, which is provided with a gas passage connecting the gas sharing chamber of the large capacity battery and the external gas pipe, and an electrolyte passage connecting the electrolyte sharing chamber of the large capacity battery and the external liquid pipe, and the gas passage and the electrolyte passage are isolated from each other.

47. The lithium-ion battery capacity restoration method of claim 46, wherein, The lithium supplementing device comprises a lithium source, a lithium supplementing wire, a variable resistor and a switch; The lithium source is arranged in the large capacity battery and soaked in the electrolyte; One end of the lithium supplementing wire is electrically connected with the lithium source, and the other end is used for connecting with the polarity terminal of the large capacity battery, and the lithium supplementing wire is provided with a switch and a variable resistor; The switch is used for turning on or turning off the lithium supplementing wire.

48. The lithium-ion battery capacity restoration method of claim 47, wherein, The lithium source comprises two layers of copper mesh layers and a metal lithium layer arranged between the two layers of copper mesh layers.

49. The lithium-ion battery capacity restoration method of claim 43, wherein: The cut-off voltage of the over-discharge is 0.01V to 2.4V.

50. The lithium-ion battery capacity restoration method of claim 44, wherein: The heating temperature range is 45 to 60℃.

51. The lithium-ion battery capacity restoration method of claim 20, wherein, Comprising the following steps: Step 1: Real-time detection of the large capacity battery. If the capacity of the large capacity battery is detected to decay to X1 or the number of charge-discharge cycles is detected to be Y1, at least one step 2 is performed; wherein 85%≤X1≤98%; Y1≥200 times; Step 2: First stage online repair Step a: Supplementing lithium to the large capacity battery through a lithium supplementing device; Step 3: Real-time detection of the large capacity battery. If the large capacity battery is detected to reach the second repair condition, at least one step 4 is performed; Step 4: Second stage online repair Step b: Over-discharging the large capacity battery; Step c: Supplementing or replacing the electrolyte of the large capacity battery through a functional interface, and exhausting the large capacity battery through the functional interface; The second repair condition is the following two cases: Case 1: The capacity and capacity retention rate of the large capacity battery do not significantly improve after the first stage online repair; Case 2: The capacity of the large capacity battery decays to X2 or the number of charge-discharge cycles is Y2; wherein 70%≤X2≤95%; Y2>Y1.

52. The lithium-ion battery capacity restoration method of claim 51, wherein, The step 4 further comprises step d: performing heating treatment on the large capacity battery through a heat transfer pipe on the large capacity battery polarity terminal.

53. The lithium-ion battery capacity restoration method of claim 51 or 52, wherein, The step 4 further comprises step e: performing secondary lithium supplement on the large capacity battery through a lithium supplement device.

54. The lithium-ion battery capacity restoration method of claim 51, wherein, The step 2 further comprises step f: performing liquid supplement on the large capacity battery through a functional interface, and simultaneously performing exhaust on the large capacity battery through the functional interface.

55. The lithium-ion battery capacity restoration method of claim 51, wherein, The functional interface is a columnar body, and a gas passage for connecting a gas chamber of the large capacity battery and an external gas pipe, and an electrolyte passage for connecting an electrolyte chamber of the large capacity battery and an external liquid pipe are arranged in the columnar body, and the gas passage and the electrolyte passage are isolated from each other.

56. The lithium-ion battery capacity restoration method of claim 51, wherein, The lithium supplement device comprises a lithium source, a lithium supplement lead, a variable resistor and a switch. The lithium source is arranged in the large capacity battery and is soaked in the electrolyte. One end of the lithium supplement lead is electrically connected with the lithium source, and the other end is used for connecting with a polarity terminal of the large capacity battery, and the lithium supplement lead is provided with the switch and the variable resistor. The switch is used for turning on or turning off the lithium supplement lead.

57. The lithium-ion battery capacity restoration method of claim 56, wherein, The lithium source comprises two layers of copper mesh layers and a metal lithium layer arranged between the two layers of copper mesh layers.

58. The lithium-ion battery capacity restoration method of claim 51, wherein: The cut-off voltage of the over-discharge is 0.01V to 2.4V.

59. The lithium-ion battery capacity restoration method of claim 52, wherein: The heating temperature range is 45 to 60℃.

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