Method for improving cycle performance of battery

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a method for improving the cycle performance of a battery. The improvement method comprises the following steps: S1, accurately calibrating the initial actual available capacity of the battery, and ensuring that the amount of free electrolyte in the battery is controlled to be 1-4% of the total weight; and S2, the battery is circularly charged and discharged under the target pre-tightening force of 1200-7200 N, the charging process is stepped charging, the charging current is gradually reduced in a stepped mode in the charging process, and constant-current discharging is carried out after the battery is charged to a full-charge state. According to the invention, a side reaction source and a gas production space are reduced through the barren solution, the pre-tightening force maintains structural stability and interface contact and synergistically inhibits bulging, the stepped charging adapts to the barren solution environment, and the harmful process under high magnification and high SOC is actively avoided, so that the capacity fading speed of the battery in the long-term cycle process is remarkably reduced through the synergistic effect of the three parts, and the battery performance is improved. The cycle performance of the battery is improved, so that the cycle life is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and specifically relates to a method for improving battery cycle performance. Background Technology

[0002] Lithium-ion batteries possess outstanding advantages such as high energy density, no memory effect, long cycle life, rapid charging and discharging, and low self-discharge, making them widely used in portable devices, electric vehicles, and aerospace energy storage fields, resulting in significant market demand. Although lithium-ion batteries are rechargeable, their charge-discharge cycles are limited. The battery's discharge capacity gradually decreases with each cycle, eventually rendering it unusable. Therefore, improving battery cycle life is essential, as it represents a bottleneck in the application of lithium-ion batteries.

[0003] Existing technologies can improve battery cycle life by optimizing electrode materials and increasing the content or types of electrolyte additives; however, these improvements increase battery manufacturing costs. Therefore, there is an urgent need for a low-cost method to improve the cycle performance of lithium-ion batteries. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for improving battery cycle performance. During cycling, the present invention improves battery cycle performance and thus extends the lifespan of lithium-ion batteries through the synergistic effect of setting preload force, adjusting the charge / discharge mechanism, and regulating the amount of free electrolyte.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for improving battery cycle performance, comprising the following steps: S1. Accurately calibrate the initial actual usable capacity of the battery to ensure that the amount of free electrolyte in the battery is controlled at 1% - 4% of the total weight; S2. The battery is subjected to cyclic charging and discharging under a target preload force of 1200~7200 N. The charging process is a stepped charging process, in which the charging current decreases step by step. After the battery is fully charged, it is discharged with constant current.

[0006] Further improvements to methods for improving battery cycle performance: Preferably, during the stepped charging process, the initial charging current is 1~1.5 C, the final charging current is 0.05~0.2 C, the number of decreases is 3~6, ​​and the magnitude of each decrease is 0.05~0.7 C.

[0007] Preferably, the constant current discharge current is the standard discharge current 1C.

[0008] Preferably, in step S1, the amount of free electrolyte in the battery is controlled at 3-4% of the total weight.

[0009] Preferably, the target preload is 4000~5500 N.

[0010] Preferably, in the stepped charging process, the battery after capacity calibration is charged to the first state of charge with an initial charging current, then charged to the second state of charge with a second charging current, then charged to the third state of charge with a third charging current, and finally charged to the full charge with a fourth charging current.

[0011] Preferably, the first state of charge is 60-75%, the second state of charge is 75-85%, the third state of charge is 85-95%, and the fourth state of charge is 95-100%.

[0012] Preferably, the initial charging current is 1.3 C, the second charging current is 0.8 C, the third charging current is 0.5 C, and the fourth charging current is 0.1 C.

[0013] Preferably, the battery is a lithium-ion battery.

[0014] Preferably, the battery includes a positive electrode, a negative electrode, a separator, and an electrolyte.

[0015] The advantages of this invention compared to the prior art are as follows: This invention discloses a method for improving battery cycle performance. First, the initial usable capacity of the battery is accurately calibrated to ensure that the amount of free electrolyte within the battery is controlled at 1%-4% of the total weight. Then, the battery is subjected to cyclic charging and discharging under a target preload of 1200-7200 N. The charging process is a stepped charging, with the charging current decreasing stepwise during charging. After reaching full charge, constant current discharge is performed. The improvement in cycle performance is significant by reducing the charging current at high SOC, increasing cycle performance by approximately 15.4%. This is mainly because the material exhibits minimal volume expansion at high SOC (above 70%), which is unfavorable for rapid lithium-ion insertion. Therefore, the cycle performance can be improved by gradually reducing the charging current in a stepped manner.

[0016] This invention, during cycling, utilizes a combination of three factors: the setting of pre-tightening force, the adjustment of the charge-discharge mechanism, and the regulation of the free electrolyte volume. The pre-tightening force enhances the degree of electrolyte wetting in the battery; the adjusted charge-discharge mechanism improves the lithium-ion insertion / extraction efficiency during cycling; and the free electrolyte volume, within the range of 1-4%, allows for replenishment later in the cycle, preventing electrolyte depletion. Through the combined effect of these three factors, the capacity decay rate of the battery during long-term cycling is significantly slowed, improving battery cycle performance and thus extending the lifespan of lithium-ion batteries. This method is particularly suitable for battery systems sensitive to volume expansion (e.g., silicon-based anodes) or operating at high voltages (e.g., high-nickel cathodes). Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0018] This invention provides a method for improving battery cycle performance, the method comprising the following steps: S1. Accurately calibrate the initial actual usable capacity of the battery to ensure that the amount of free electrolyte in the battery is controlled at 1% - 4% of the total weight; S2. The battery is subjected to cyclic charging and discharging under a target preload force of 1200~7200 N. The charging process is a stepped charging process, in which the charging current decreases step by step. After the battery is fully charged, it is discharged with constant current.

[0019] In this invention, the volume of free electrolyte in the battery is controlled at 1%-4% of the total weight. The setting of the pre-tightening force, the adjustment of the charging and discharging mechanism, and the volume of free electrolyte must work in concert to improve battery cycle performance. Without setting the pre-tightening force, the increased expansion of the electrode plates will lead to a greater lithium-ion transport distance, potentially causing obstruction and cycle failure. Conversely, if a full charge and full discharge cycle is performed directly during cycling, lithium plating at high charging rates will occur in the later stages of the cycle as the charging capacity decreases. Furthermore, without adjusting the volume of free electrolyte, improving cycle performance is not recommended.

[0020] In this invention, if the amount of free electrolyte is too small, less than 1%, it will lead to cycle failure due to lack of electrolyte in the middle and late stages of the cycle; while if it is too large, exceeding 4%, it will increase the side reactions of the cycle and lead to poor cycle performance.

[0021] In this invention, if the target preload is too high, exceeding 7200 N, it will affect the wettability of the battery and cause cycle failure due to lack of battery liquid during cycling; while if the target preload is too low, below 1200 N, it will not be conducive to the rapid transport of lithium ions; furthermore, when the value is in the range of 4000~5500 N, it has better cycle performance.

[0022] In a preferred embodiment of the present invention, during the stepped charging process, the initial charging current is 1~1.5 C, the final charging current is 0.05~0.2 C, the current decreases 3~6 times, and the decrease in current is 0.05~0.7 C each time. This is mainly because high-rate fast charging can shorten the charging time, while low-rate slow charging helps lithium ions to be uniformly embedded in the negative electrode, reducing polarization effects and delaying capacity decay. By adjusting the charging current in stages, the battery lifespan is maximized.

[0023] In a preferred embodiment of the present invention, the constant current discharge current is a standard discharge current of 1C.

[0024] In a preferred embodiment of the present invention, in step S1, the amount of free electrolyte in the battery is controlled at 3-4% of the total weight. This is more conducive to improving cycle performance; if it is below 3%, although it can supplement the electrolyte in the later stage of the cycle, it will affect the cycle life due to insufficient electrolyte; if it exceeds 4%, there will be too many side reactions.

[0025] In a preferred embodiment of the present invention, the target preload is 4000~5500N.

[0026] As a preferred technical solution in a specific embodiment of the present invention, in the stepped charging process, the battery after capacity calibration is charged to the first state of charge with an initial charging current, then charged to the second state of charge with a second charging current, then charged to the third state of charge with a third charging current, and finally charged to the full charge with a fourth charging current.

[0027] In a preferred embodiment of the present invention, the first state of charge (SOC) is 60-75%, the second SOC is 75-85%, the third SOC is 85-95%, and the fourth SOC is 95-100%. This is mainly because the material expands little in volume at high SOC (above 70%), which is not conducive to the rapid insertion of lithium ions. Therefore, the charging method can be adjusted according to the SOC to improve the cycle performance of the battery.

[0028] In this invention, if the first state of charge is too large, it will affect the charging energy of the material; if the first state of charge is too small, it will lead to a long charging time and affect the efficiency of use.

[0029] The initial charging current is 1.3 C, the second charging current is 0.8 C, the third charging current is 0.5 C, and the fourth charging current is 0.1 C. By selecting a high rate for fast charging at low SOC and a low rate for slow charging at high SOC, the charging speed and battery safety are balanced through staged adjustment of current and SOC (voltage), maximizing battery lifespan.

[0030] In a preferred embodiment of the present invention, the battery is a lithium-ion battery.

[0031] It should be noted that the positive electrode, negative electrode, separator, and electrolyte in the battery structure provided by this invention are all conventional technologies, and their preparation methods are also conventional technologies.

[0032] As a preferred technical solution in a specific embodiment of the present invention, the battery includes a positive electrode, a negative electrode, a separator, and an electrolyte.

[0033] Optionally, the positive electrode includes a positive current collector and a positive active material layer located on at least one side of the positive current collector. The positive active material layer includes a positive active material, a conductive agent, and a binder. The negative electrode includes a negative current collector and a negative active material layer located on at least one side of the negative current collector (which may also be a pure metal negative electrode). The negative active material includes a negative active material, a conductive agent, and a binder (which may also be a pure metal negative electrode).

[0034] The types of raw materials mentioned above are not particularly limited. Any known substance can be used in this application without departing from the inventive concept of this application.

[0035] In one embodiment, the positive electrode active material includes, but is not limited to, lithium cobalt oxide (LiCoO2) and lithium nickel cobalt manganese oxide (LiNiO2). x MNyCo 1-x-y O2 (NMC), lithium nickel cobalt aluminum oxide (LiNiCoAlO2, NCA), lithium manganese oxide (LiMN2O4), lithium manganese iron phosphate (LiMN) x Fe 1-x PO4 (abbreviated as LMFP), lithium vanadium phosphate (Li3V2(PO4)3), lithium vanadium oxide phosphate (LiVOPO4), lithium iron phosphate (LiFePO4), lithium titanate (Li2TiO3), and one or more of lithium-rich manganese-based materials.

[0036] Optionally, the negative electrode active material includes graphite, non-graphite carbon, and non-carbon-based graphite materials. In other embodiments, the negative electrode active material is a silicon-based negative electrode active material containing silicon, such as silicon alloys, silicon oxide, or combinations thereof, and in some cases may be mixed with graphite. In other embodiments, the negative electrode may include a carbon-based negative electrode active material containing one or more of graphite, graphene, carbon nanotubes (CNTs), and combinations thereof. In yet another embodiment, the negative electrode active material includes one or more lithium-accepting negative electrode active materials, such as lithium titanium oxide (Li4Ti5O). 12 One or more transition metals (such as tin (SN)), one or more metal oxides (such as vanadium oxide (V₂O₅), tin oxide (SNO), titanium dioxide (TiO₂)), titanium niobium oxide (Ti) x Nb y O z , where 0≤x≤2, 0≤y≤24 and 0≤z≤64, metal alloys (such as copper-tin alloy (Cu6SN5)) and one or more metal sulfides (such as iron sulfide (FeS)).

[0037] Optionally, there are no particular restrictions on the positive and negative current collectors, as long as they are conductive and do not cause chemical changes in the battery. Specifically, copper, stainless steel, aluminum, nickel, titanium, or metal current collectors with surfaces treated with carbon or other substances can be used.

[0038] Optionally, the adhesive is a component used to assist in the bonding of active materials, conductive materials, etc., and to bond with current collectors. Specifically, it may include components selected from polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, and ethylene. propylene Diene monomer (EPDM), sulfonated EPDM, styrene At least one of the group consisting of butadiene rubber and fluororubber.

[0039] Conductive agents can be used to assist and improve the conductivity in secondary batteries, and there are no particular limitations, as long as they are conductive without causing chemical changes. Specifically, they may include graphite, such as natural or artificial graphite; carbon materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking black; conductive fibers, such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; metal powders, such as fluorocarbon powders, aluminum powders, and nickel powders; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxides; and polyphenylene derivatives.

[0040] In one embodiment, the separator separates the negative and positive electrodes and provides a path for lithium ions to move. Any separator can be used without particular limitation, as long as it is a separator commonly used in secondary batteries. In particular, separators with excellent electrolyte moisture content and low resistance to ion movement in the electrolyte are preferred. Specifically, porous polymer membranes can be used, for example, porous polymer membranes made from polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures having two or more layers thereof. Furthermore, typical porous nonwoven fabrics can be used, for example, nonwoven fabrics formed from high-melting-point glass fibers, polyethylene terephthalate fibers, etc. In addition, coated separators containing ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and can be selectively used in single-layer or multi-layer structures.

[0041] In one embodiment, the electrolyte includes an electrolyte salt and a solvent.

[0042] In some embodiments, the electrolyte salt includes, but is not limited to, one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0043] In some embodiments, the solvent includes, but is not limited to, one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0044] In some embodiments, the electrolyte also includes additives, which may be negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery performance, such as additives that improve battery overcharge performance, or additives that improve battery high-temperature or low-temperature performance. Any known type of additive can be used in this application without departing from the inventive concept. There are no special requirements for the mixing method of the additives; for example, they can be directly mixed with conductive agents, active materials, and binders to form a mixture.

[0045] Preparation Example This preparation example provides a method for preparing a lithium-ion battery and calibrating its capacity, as detailed below: Step 1: Preparation of the positive electrode sheet: After uniformly mixing NCM811 (95 wt%) and Super P (3 wt%), PVDF (2 wt%) and an appropriate amount of N-methylpyrrolidone are added and mixed evenly to obtain a positive electrode active material slurry; the above slurry is coated onto aluminum foil, and the conveyor belt speed is controlled at 90℃ to allow the active material slurry to dry, resulting in an areal density of 40 mg / cm³. 2 The positive active material coating is rolled to obtain the positive electrode sheet; Preparation of the negative electrode: Graphite (96 wt%), Super P (1.5 wt%), CMC (1.0 wt%), and an appropriate amount of deionized water were mixed evenly, and then SBR (1.5%) was added and mixed evenly to obtain a negative electrode active material slurry. The slurry was coated onto copper foil, and the conveyor belt speed was controlled at 80~110℃ to allow the active material to dry, resulting in an areal density of 18 mg / cm³. 2 The negative electrode active material coating is rolled to obtain the negative electrode sheet; Diaphragm: Polyethylene diaphragm; Electrolyte: A three-component mixed solvent of 1 mol / L LiPF6 in a volume ratio of EC:DMC:EMC = 1:1:1 is used as the electrolyte; Step 2: Wind the above positive electrode sheet, separator, and negative electrode sheet into a battery cell, and then place the battery cell in an aluminum-plastic packaging bag to assemble it into a battery cell to be injected with liquid. Step 3: The assembled cells are sequentially subjected to electrolyte injection, settling, pre-charging, aging, formation, aging, and capacity testing to obtain the lithium-ion battery; Step 4: Capacity calibration. Charge and discharge the battery at room temperature with a charge and discharge current of 1 C for 3 cycles to calibrate the room temperature discharge capacity D1, thus obtaining the lithium-ion battery after capacity calibration.

[0046] Example 1 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example, specifically including the following steps: S1. Take the lithium-ion battery whose capacity has been calibrated according to the example, and ensure that the amount of free electrolyte in the battery is controlled at 3% of the total weight; S2. The battery is subjected to cyclic charging and discharging under a target preload force of 4800 N. The charging process is a stepped charging: the battery after capacity calibration is charged at 1.3 C to 70% SOC, then charged at 0.8 C to 80% SOC, 0.5 C to 90% SOC, and 0.1 C to 100% SOC; then discharged at 1 C to complete one charge-discharge cycle; the charge-discharge cycle is repeated 2900 times to obtain battery 1 with improved cycle performance.

[0047] Example 2 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the target preload force in step S2 is 1200 N. A battery 2 with improved cycle performance is obtained.

[0048] Example 3 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the target preload force in step S2 is 2800 N. A battery 3 with improved cycle performance is obtained.

[0049] Example 4 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the target preload force in step S2 is 4000 N. A battery 4 with improved cycle performance is obtained.

[0050] Example 5 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the target preload force in step S2 is 5500 N. A battery 5 with improved cycle performance is obtained.

[0051] Example 6 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the target preload force in step S2 is 7200 N. A battery 6 with improved cycle performance is obtained.

[0052] Example 7 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the target preload force in step S2 is 8000 N. A battery 7 with improved cycle performance is obtained.

[0053] Example 8 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the charging process in step S2 is a stepped charging: the battery after capacity calibration is charged at 1.3 C to 75% SOC, 0.8 C to 80% SOC, 0.5 C to 90% SOC, 0.1 C to 100% SOC, and then discharged at 1 C to complete one charge-discharge cycle; the battery 8 with improved cycle performance is obtained.

[0054] Example 9 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the charging process in step S2 is a stepped charging: the battery after capacity calibration is charged at 1.3 C to 80% SOC, then at 0.5 C to 90% SOC, then at 0.1 C to 100% SOC, and then discharged at 1 C to complete one charge-discharge cycle; thus obtaining the battery 9 with improved cycle performance.

[0055] Example 10 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the amount of free electrolyte in the battery is controlled at 1% of the total weight in step S1. A battery 10 with improved cycle performance is obtained.

[0056] Example 11 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the amount of free electrolyte in the battery is controlled at 2% of the total weight in step S1. A battery 11 with improved cycle performance is obtained.

[0057] Example 12 This embodiment provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the amount of free electrolyte in the battery is controlled at 4% of the total weight in step S1. A battery 12 with improved cycle performance is obtained.

[0058] Comparative Example 1 This comparative example provides a general method for improving the cycle performance of lithium-ion batteries, specifically including the following steps: S1. Take the lithium-ion battery whose capacity has been calibrated according to the example, and ensure that the amount of free electrolyte in the battery is controlled at 5% of the total weight; S2. Perform cyclic charging and discharging without preload; specifically: charge the capacity-calibrated battery at 1.3C to 100% SOC, then discharge at 1C to complete one charge-discharge cycle; repeat this charge-discharge cycle 450 times. This yields battery 1 with moderately improved cycle performance.

[0059] Comparative Example 2 This comparative example provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that in step S2, the charge-discharge cycle is performed without preload. A battery 2 with generally improved cycle performance is obtained.

[0060] Comparative Example 3 This comparative example provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the charge-discharge mechanism in step S2 is as follows: the battery after capacity calibration is charged to 100% SOC at 1.3C, and then discharged at 1C to complete one charge-discharge cycle. A battery 3 with generally improved cycle performance is obtained.

[0061] Comparative Example 4 This comparative example provides a method for improving the cycle performance of the lithium-ion battery prepared in the above example. The specific steps are the same as in Example 1, except that the amount of free electrolyte in the battery is controlled at 5% of the total weight in step S1. A battery 4 with generally improved cycle performance is obtained.

[0062] Cycle performance tests were conducted on the improved batteries from Examples 1-12 and Comparative Examples 1-4. Cycle performance included the capacity retention rate (DN / D1) after 400 cycles (N=400) of the lithium-ion battery; it also included the number of cycles in which the capacity retention rate (DN / D1) decreased to below 80%. The results are shown in Table 1 below. Table 1. Improvement measures and cycle performance tests of Examples 1-12 and Comparative Examples 1-4 ; The data results from Examples 1-7 show that when the target preload is between 4000 and 5500 N, the cycle performance is improved more effectively; when it exceeds 7200 N, not only is the cycle performance not improved, but the wettability of the electrode in the later stages of the cycle is also affected, leading to cycle failure.

[0063] The data results from Examples 1 and 8-9 show that an excessively high initial state of charge during the charging process, exceeding 75%, can negatively impact the material's charging capability in the later stages of the cycle.

[0064] The data from Examples 1 and 10-12 show that a free electrolyte content of 3-4% in lithium-ion batteries is more conducive to improving cycle performance.

[0065] As can be seen from the data results of Examples 1-12 and Comparative Example 1, the preparation method provided by the present invention greatly improves the cycle performance of lithium-ion batteries.

[0066] As can be seen from the data results of Example 1 and Comparative Examples 2-4, the present invention can only achieve improved cycle performance through the synergistic combination of pre-tightening force, charging and discharging mechanism and the amount of free electrolyte; without any one of these factors, it cannot be achieved.

[0067] In summary, the improved method provided by this invention, through the synergistic effect of setting the preload, adjusting the charge-discharge mechanism, and regulating the amount of free electrolyte during cycling, enhances the degree of electrolyte wetting in the battery. Adjusting the charge-discharge mechanism improves the lithium-ion insertion / extraction efficiency during cycling. Maintaining the free electrolyte level within the range of 1-4% allows for electrolyte replenishment in the later stages of cycling, preventing battery depletion. Through the combined effect of these three factors, the battery cycle performance is improved, thereby extending the lifespan of the lithium-ion battery.

[0068] The present invention has been illustrated with detailed structural features through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., are all within the protection scope and disclosure scope of the present invention.

[0069] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0070] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

[0071] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for improving battery cycle performance, characterized in that, Includes the following steps: S1. Accurately calibrate the initial actual usable capacity of the battery to ensure that the amount of free electrolyte in the battery is controlled at 1% - 4% of the total weight; S2. The battery is subjected to cyclic charging and discharging under a target preload force of 1200~7200 N. The charging process is a stepped charging process, in which the charging current decreases step by step. After the battery is fully charged, it is discharged with constant current.

2. The method for improving battery cycle performance according to claim 1, characterized in that, During the stepped charging process, the initial charging current is 1~1.5 C, the final charging current is 0.05~0.2 C, the number of decreases is 3~6, ​​and the magnitude of each decrease is 0.05~0.7 C.

3. The method for improving battery cycle performance according to claim 1, characterized in that, The constant current discharge current is the standard discharge current 1C.

4. The method for improving battery cycle performance according to any one of claims 1-3, characterized in that, In step S1, ensure that the amount of free electrolyte in the battery is controlled at 3-4% of the total weight.

5. The method for improving battery cycle performance according to claim 1, characterized in that, The target preload is 4000~5500 N.

6. The method for improving battery cycle performance according to claim 2, characterized in that, In the stepped charging process, the battery, after capacity calibration, is charged to the first state of charge with an initial charging current, then to the second state of charge with a second charging current, then to the third state of charge with a third charging current, and finally to the fully charged state with a fourth charging current.

7. The method for improving battery cycle performance according to claim 6, characterized in that, The first state of charge is 60-75%, the second state of charge is 75-85%, the third state of charge is 85-95%, and the fourth state of charge is 95-100%.

8. The method for improving battery cycle performance according to claim 6 or 7, characterized in that, The initial charging current is 1.3 C, the second charging current is 0.8 C, the third charging current is 0.5 C, and the fourth charging current is 0.1 C.

9. The method for improving battery cycle performance according to claim 1, characterized in that, The battery is a lithium-ion battery.

10. The method for improving battery cycle performance according to claim 9, characterized in that, The battery includes a positive electrode, a negative electrode, a separator, and an electrolyte.