Lithium ion battery and lithium supplementing method thereof

Abstract

The invention provides a lithium ion battery and a lithium supplementing method, the lithium ion battery comprises a positive plate, the positive plate comprises a lithium supplementing agent, and the lithium supplementing agent comprises at least one of Li2S, Li2S2, Li2S4, Li2S6 and Li2S8; the addition amount of the lithium supplement agent is W, the gram volume Q of the lithium supplement agent and the capacity loss C of the lithium ion battery meet the relation: W = 1000C / Q. According to the lithium ion battery provided by the invention, the lithium-sulfur compound type lithium supplementing agent is added into the positive electrode, so that active lithium in the lithium supplementing agent can be released under a relatively low working voltage, and a chemical reaction for releasing the active lithium does not generate oxygen, so that the safety of the battery is ensured, and large-scale production equipment and productivity are not influenced; besides, in the charging and discharging process of the battery, the gram volume exertion of the lithium supplementing agent can be controlled by controlling the charging current of the battery, and a reaction product which does not influence the performance of the battery can be selectively generated.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a lithium ion battery and a lithium replenishment method thereof. Background Art

[0002] With the rapid development of portable electronic products, new energy vehicles, smart grids and other fields, higher requirements are placed on the energy density of lithium-ion batteries. In order to improve the energy density of batteries, in addition to optimizing battery structure and material iteration, lithium replenishment technology is also an important means. During the first charging of the battery, a solid electrolyte interface film will form on the surface of the negative electrode. This process will irreversibly consume the active lithium in the battery, resulting in the battery's energy density and cycle life being affected. This problem can be effectively solved by replenishing active lithium through lithium replenishment technology.

[0003] In the industry, in order to improve the initial charge and discharge efficiency of lithium-ion batteries, the method under development is to supplement lithium at the positive and negative electrodes of lithium-ion batteries. Because the technology of supplementing lithium at the negative electrode is difficult and has high safety risks, lithium is mostly supplemented at the positive electrode, that is, lithium supplement additives are added to the positive electrode to make up for the loss of active lithium during the initial charge and discharge process. Commonly used positive electrode lithium supplement additives in the current industry include Li5FeO4, Li2NiO4, Li2C2O2, etc., but the platform voltage of Li5FeO4 for releasing active lithium is relatively high. When the charging cut-off voltage is higher than 4V, the pressure resistance of the electrolyte is required to be high under high voltage. In addition, a large amount of oxygen will be generated during the release of active lithium by the lithium supplement additive, which will cause safety hazards during the degassing process. If the degassing is not clean, oxygen will remain in the battery, which will also bring safety hazards.

[0004] The platform voltage of Li2NiO4 releasing active lithium is also high, and the charging cut-off voltage is also higher than 4V. The pressure resistance of the electrolyte is required to be high under high voltage. On the other hand, the amount of active lithium released by Li2NiO4 is small. Under the same amount of lithium supplementation, the amount of Li2NiO4 used should be increased. Although lithium supplementation technology has made great progress, it still faces some challenges, such as improving the utilization rate of lithium supplementation agents, ensuring the safety and stability of batteries, and reducing costs.

[0005] In view of this, it is indeed necessary to provide a technical solution to the above problems. Summary of the invention

[0006] One of the purposes of the present invention is to provide a lithium-ion battery to address the deficiencies of the prior art, so as to improve the problem that the positive electrode lithium supplement additive in the current lithium-ion battery produces gas at high voltage, which may lead to potential safety hazards in the battery.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A lithium-ion battery comprises a positive electrode sheet, wherein the positive electrode sheet comprises a lithium supplement agent, wherein the lithium supplement agent comprises at least one of Li2S, Li2S2, Li2S4, Li2S6, and Li2S8; the amount of the lithium supplement agent added is W, the gram capacity of the lithium supplement agent is Q, and the capacity loss C of the lithium-ion battery satisfies the relationship: W=1000C / Q; wherein the unit of W is g, the unit of Q is mAh / g, and the unit of C is Ah.

[0009] Preferably, the capacity loss C of the lithium-ion battery and the charging current I of the lithium-ion battery satisfy the relationship: 0<I<0.3C.

[0010] Preferably, the battery operating voltage U is negatively correlated with the gram capacity Q of the lithium supplement.

[0011] Preferably, the lithium supplement is a mixture, and the mixture includes a lithium sulfur compound soluble in the electrolyte and a lithium sulfur compound insoluble in the electrolyte.

[0012] Preferably, the gram capacity Q of the lithium supplement agent ranges from 63 to 1150 mAh / g.

[0013] Preferably, the addition amount W of the lithium supplement agent ranges from 21 to 80 g.

[0014] Preferably, the capacity loss C of the lithium-ion battery ranges from 24 to 45 Ah.

[0015] A second object of the present invention is to provide a method for replenishing lithium in a lithium-ion battery, comprising the following steps:

[0016] 1) During the first charge and discharge, charging is performed at a first preset voltage and a first preset current, and the battery capacity loss C1 is calculated; wherein the first preset voltage is 2.3 to 2.9 V, and the first preset current is 2 to 4 A;

[0017] 2) Calculate the amount of lithium supplement W1 added based on C1, where W1 = C1 / Q1, Q1 is the gram capacity of the lithium supplement. 3) During cyclic charge and discharge, charge at a second preset voltage and a second preset current, and calculate the battery capacity loss C2; where the second preset voltage is 2.3 to 3.65 V, and the second preset current is 80 to 84 A;

[0018] 4) Calculate the amount of lithium supplement W2 based on C2, where W2 = (C1 + C2) / Q2, and Q2 is the gram capacity of the lithium supplement.

[0019] Preferably, during the first charge and discharge, C1 is 22 to 24 Ah; during the cyclic charge and discharge, C2 is 17 to 20 Ah.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the lithium-ion battery provided by the present invention, by adding a lithium-sulfur compound type lithium supplement agent to the positive electrode, the active lithium in the lithium supplement agent can be released at a relatively low operating voltage, and the chemical reaction of releasing the active lithium will not produce oxygen, which not only ensures the safety of the battery, but also has no impact on the equipment and production capacity of large-scale production; at the same time, due to its low operating voltage, the requirements for the oxidation resistance of the electrolyte do not need to be increased; in addition, during the battery charging and discharging process, by controlling the battery charging current, the gram capacity of the lithium supplement agent can be controlled, and reaction products that do not affect the battery performance can be selectively generated. DETAILED DESCRIPTION

[0021] To make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects will be further described in detail below in conjunction with specific implementation methods, but the implementation methods of the present invention are not limited thereto.

[0022] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0023] The first aspect of the present invention is to provide a lithium ion battery, comprising a positive electrode sheet, wherein the positive electrode sheet comprises a lithium supplement agent, wherein the lithium supplement agent comprises at least one of Li2S, Li2S2, Li2S4, Li2S6, and Li2S8; the amount of the lithium supplement agent added is W, the gram capacity of the lithium supplement agent is Q, and the capacity loss C of the lithium ion battery satisfies the relationship: W=1000C / Q; wherein the unit of W is g, the unit of Q is mAh / g, and the unit of C is Ah.

[0024] The lithium supplement used in the present invention is a lithium-sulfur compound. Compared with lithium-rich compounds such as Li5FeO4, Li2NiO4, Li2C2O2 and binary lithium compounds such as Li2O2, Li2O and Li3N, the lithium-sulfur compound has a high theoretical gram capacity and a low operating voltage (the operating voltage is 1.0-2.9V). The lithium-sulfur compound can release active lithium at a relatively low operating voltage, and no oxygen is generated when the active lithium is released, thereby ensuring the safety of the battery. In addition, due to the relatively low operating voltage, the oxidation resistance requirement of the electrolyte in the battery does not need to be increased.

[0025] When the battery is charged and discharged, the charging reaction and corresponding gram capacity of the lithium-sulfur compound of the lithium supplement at different voltages are also different. For example, the chain reaction of Li2S at continuously increasing voltages is shown in Table 1 below:

[0026] Table 1

[0027]

[0028] In some embodiments, the lithium-ion battery capacity loss C and the lithium-ion battery charging current I satisfy the relationship: 0<I<0.3C.

[0029] Among them, the battery operating voltage U is negatively correlated with the gram capacity Q of the lithium supplement. The lithium supplement needs to release lithium ions during the charging process of the battery, and its lithium desorption potential should be lower than the voltage upper limit of the positive electrode material, and the lithium insertion potential should be lower than the voltage lower limit of the positive electrode material. If the operating voltage of the battery is high, the lithium desorption potential of the lithium supplement must be lower to ensure that it can effectively release lithium ions during the battery charging process. This limits the gram capacity of the lithium supplement because it must release lithium ions at a lower voltage, which may reduce its theoretical gram capacity; the chemical stability of the lithium supplement is also an important factor. At higher operating voltages, the lithium supplement needs to remain stable and not react adversely with the electrolyte or other battery components. This stability requirement may limit the choice of lithium supplements, thereby affecting their gram capacity.

[0030] In addition, the lithium supplement needs to maintain stable performance during battery cycling to continuously provide lithium ions. If the operating voltage of the battery is higher, the lithium supplement may face greater stability challenges, which may affect its long-term gram capacity performance.

[0031] In some embodiments, the lithium supplement is a mixture, and the mixture includes a lithium sulfur compound soluble in the electrolyte and a lithium sulfur compound insoluble in the electrolyte; for example, Li2S and Li2S2 are insoluble in the electrolyte containing an organic solvent, while Li2S4, Li2S6, and Li2S8 are soluble in the electrolyte containing an organic solvent; the lithium-sulfur compound dissolved in the electrolyte containing an organic solvent will migrate to the surface of the diaphragm and the negative electrode through the electrolyte. When migrating to the diaphragm, it will affect the normal passage of lithium ions through the pores of the diaphragm, thereby increasing the polarization of the battery and reducing the kinetic performance of the battery. When migrating to the surface of the negative electrode, it will change the current density on the surface of the negative electrode, thereby affecting the normal insertion and extraction of lithium ions, and in severe cases may cause the formation of lithium dendrites. Therefore, when selecting different lithium-sulfur compounds as lithium supplements, it is necessary to adjust different working voltages to regulate the products of the electrochemical reaction of the lithium-sulfur compounds.

[0032] Preferably, the gram capacity Q of the lithium supplement agent ranges from 63 to 1150 mAh / g.

[0033] Preferably, the value range of W is 21 to 80 g.

[0034] Preferably, the value range of C is 24 to 45 Ah.

[0035] A second aspect of the present invention is to provide a lithium replenishing method for a lithium ion battery, comprising the following steps:

[0036] 1) Stage 1: During the first charge and discharge, the battery capacity loss is C1, and the mass of the added lithium supplement is W1 = C1 / (gram capacity of the lithium supplement);

[0037] 2) Stage 2: During cyclic charge and discharge, the battery capacity is lost, recorded as C2, and the mass of the added lithium supplement W2 = (C1+C2) / (gram capacity of the lithium supplement).

[0038] Among them, the loss of active lithium in lithium-ion batteries mainly occurs in two stages: the first stage refers to the initial charge and discharge process of the battery, when the active lithium undergoes side reactions on the surfaces of the positive and negative electrodes to produce a solid electrolyte interface film (SEI film), which reduces the initial charge and discharge efficiency of the battery.

[0039] The second stage refers to the process in which the battery is charged and discharged cyclically, during which the active lithium is continuously consumed due to factors such as the expansion and contraction of the negative electrode graphite, the high positive electrode potential, or the high temperature rise of the battery, causing the battery capacity to continue to decay.

[0040] The first and second stages of active lithium loss are continuous. Therefore, you can choose to replenish the active lithium loss in the first stage as needed. However, if you choose to replenish the active lithium loss in the second stage, you will first replenish the active lithium loss in the first stage before replenishing the active lithium loss in the second stage.

[0041] The preparation of the lithium ion battery in the present invention includes:

[0042] Positive electrode production:

[0043] The positive electrode sheet of a lithium-ion battery is generally composed of a positive electrode active material, a binder, a conductive agent, a dispersant and a current collector. The positive electrode active material is a common positive electrode active material in the lithium battery field. The positive electrode active material includes at least one of the following: lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide, lithium manganese oxide, ternary (NCM333 (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 ), NCM523 (LiNi5Co2Mn3), NCM622 (LiNi6Co2Mn2), NCM712 (LiNi7Co1Mn2) or NCM811 (LiNi8Co1Mn1), etc.). The binder is polyvinylidene fluoride (PVDF). The conductive agent is at least one of conductive carbon black, acetylene black, Ketjen black, carbon nanotubes or graphene. The dispersant is polyvinyl pyrrolidone (PVP). The current collector is aluminum foil.

[0044] The positive electrode active material, binder, conductive agent and dispersant are dispersed in the solvent N-methylpyrrolidone (NMP) to form a positive electrode slurry, which is then coated on the current collector aluminum foil. After drying, rolling, die cutting and striping, the positive electrode sheet is obtained.

[0045] Negative electrode production:

[0046] The negative electrode sheet of a lithium-ion battery is generally composed of a negative electrode active material, a binder, a thickener, a conductive agent and a current collector. The negative electrode active material includes at least one of the following: artificial graphite, natural graphite, soft carbon, hard carbon or silicon-based material. The binder is polyacrylic acid, styrene-butadiene rubber, polymethacrylic acid, etc. The thickener is carboxymethyl cellulose, carboxymethyl chitosan, carboxymethyl cellulose lithium, etc. The conductive agent is the same as the conductive agent for the positive electrode material.

[0047] The current collector is copper foil or composite copper foil.

[0048] The negative electrode active material, binder, thickener and conductive agent are dissolved in deionized water to form a negative electrode slurry, which is then coated on the current collector copper foil. After drying, rolling, die cutting and striping, the negative electrode sheet is obtained.

[0049] The isolation membrane is a commonly used porous polyethylene membrane.

[0050] The lithium salt in the electrolyte may be selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, and lithium difluorophosphate. The solvent in the electrolyte may be selected from at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, methyl acetate, ethyl acetate, propyl acetate, ethyl propionate, and propyl propionate. The additive in the electrolyte may be selected from at least one of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate, and methylene methanedisulfonate.

[0051] The positive electrode sheet, the negative electrode sheet, the isolation membrane and the electrolyte are assembled into a battery by winding or stacking. The battery shell can be a square aluminum shell, a square steel shell, a soft pack, a cylinder, etc.

[0052] To make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects will be further described in detail below in conjunction with specific implementation methods, but the implementation methods of the present invention are not limited thereto.

[0053] Comparative Example 1

[0054] A preparation method of a lithium ion battery comprises the following steps:

[0055] Preparation of positive electrode sheet: Lithium iron phosphate: acetylene black: PVP: PVDF is dispersed in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 90:2.5:2.5:5 to form a positive electrode slurry, which is then coated on the current collector aluminum foil. After drying, rolling, die-cutting and striping, the positive electrode sheet is obtained.

[0056] Preparation of negative electrode sheet: artificial graphite: acetylene black: carboxymethyl cellulose: polyacrylic acid is dissolved in deionized water at a mass ratio of 90:5:2.5:2.5 to form a negative electrode slurry, which is then coated on the current collector copper foil. After drying, rolling, die cutting and striping, a negative electrode sheet is obtained.

[0057] The isolation membrane is a porous polyethylene membrane.

[0058] Electrolyte: Propylene carbonate (PC): ethylene carbonate (EC) with a volume ratio of 1:1 is used as the solvent, 1.2M LiPF6 is used as the lithium salt, and 4% vinylene carbonate, vinyl ethylene carbonate, and 5% vinyl ethylene carbonate are used as additives.

[0059] Battery assembly: The positive electrode sheet, separator and negative electrode sheet are assembled into bare cells by winding, packaged with aluminum-plastic film, and injected with electrolyte to obtain lithium-ion cells. The lithium-ion cells are installed in square aluminum shells to obtain lithium-ion batteries.

[0060] The battery used in this comparative example has a square aluminum shell with a capacity of 280Ah, which is the capacity obtained when the battery is charged and discharged at a rate of 0.5C (current of 140A) at an operating voltage of 2.5V-3.65V.

[0061] The positive electrode of the battery in this comparative example does not add lithium supplement additives. When charged for the first time, the voltage is 1V-2.9V, and the first charging current of the battery is 0.1 times the battery capacity, that is, the current is 28A;

[0062] During cycle charging, the voltage is 2.9V-3.65V, and the battery charging current is 0.3 times the battery capacity, that is, the current is 84A.

[0063] Example 1

[0064] Different from the comparative example, lithium supplement Li2S is added to the positive electrode sheet, and the specific charging parameters are shown in Table 2. The rest is the same as the comparative example 1, which will not be repeated here.

[0065] Embodiments 2 to 4

[0066] The difference between this embodiment and embodiment 1 is that the specific charging parameters are shown in Table 2.

[0067] The rest is the same as in Example 1 and will not be described again here.

[0068] Embodiments 5 to 8

[0069] The difference between this embodiment and embodiment 1 is that lithium is replenished during the cyclic charge and discharge process. The specific parameters are shown in Table 2.

[0070] The rest is the same as in Example 1 and will not be described again here.

[0071] Example 9

[0072] The difference between this embodiment and embodiment 1 is that the lithium supplement agent is Li2S2. The specific parameters are shown in Table 2.

[0073] The rest is the same as in Example 1 and will not be described again here.

[0074] Comparative Examples 2 to 4

[0075] The difference between this embodiment and embodiment 1 is the initial charging current, see Table 2 for details.

[0076] The rest is the same as in Example 1 and will not be described again here.

[0077] The lithium ion batteries obtained in Examples 1-9 and Comparative Examples 1-4 were subjected to capacity tests: at room temperature, capacity retention rate = battery 0.5C capacity at 1000 cycles / battery 0.5C capacity at the first cycle of battery cycle*100%. The specific parameters and test results of the above examples and comparative examples are summarized in Table 2 and Table 3.

[0078] Table 2

[0079]

[0080]

[0081] Table 3

[0082]

[0083] From the test results in Table 3 above, we can see that:

[0084] According to the above test, by comparing the data of Examples 1-9 with Comparative Example Batteries 1 to 4, it can be seen that after adding the lithium-sulfur compound as a lithium supplement additive to the positive electrode, the capacity of the batteries of the examples all increased, with an average increase of 7.45%, and the initial charge and discharge efficiency of the battery was about 92%, indicating that the active lithium provided by the lithium-sulfur compound as a lithium supplement additive substantially compensated for the loss of the initial charge and discharge capacity of the battery, thereby improving the energy density of the battery.

[0085] By comparing the 0.5C capacity division data of Examples 5 to 8 with Examples 1-4, it can be seen that the battery capacity division capacity for replenishing the battery cycle capacity loss in the second stage will be lower than the battery capacity division capacity for replenishing the battery initial charge and discharge capacity loss in the first stage, indicating that continuing to add lithium-sulfur compounds as a lithium supplement after a certain amount has been added will reduce the extent of the battery capacity increase.

[0086] By comparing the 0.5C capacity data of the batteries of Examples 1-4 or Examples 5-8, it can be seen that the gram capacity of the lithium-sulfur compound is different under different working voltages. In the voltage range of 0-2.9V, the gram capacity of the lithium-sulfur compound increases with increasing voltage.

[0087] By comparing the battery cycle data of Examples 1-4 and the comparative example at room temperature 0.5C, it can be seen that the battery cycle capacity retention rate of Examples 1-4 is slightly higher than that of the comparative example, but the improvement is not obvious, indicating that the lithium-sulfur compound used as the lithium supplement to supplement the loss of the first charge and discharge capacity of the battery in the first stage cannot significantly improve the battery's cycle performance.

[0088] By comparing the battery cycle data of Examples 5-8 and Comparative Example 1 at room temperature and 0.5C, it can be seen that the capacity retention rate of the batteries of Examples 5-8 is still greater than 99.5% after 1000 cycles, which is significantly higher than the battery cycle capacity retention rate of the comparative example, indicating that the lithium-sulfur compound, a lithium supplement, can significantly improve the battery cycle performance by supplementing the loss of the battery cycle charge and discharge capacity in the second stage.

[0089] By comparing the 0.5C capacity distribution data of the batteries in Example 1, Comparative Examples 2 to 4 and Example 12, it can be seen that, under a fixed working voltage of 0V-2.3V, as the initial charging current increases, the battery polarization increases, and the gram capacity of the lithium supplement Li2S decreases. When the charging current exceeds 3 times the battery capacity loss, the gram capacity of the lithium supplement Li2S cannot be fully utilized due to excessive battery polarization.

[0090] By comparing the 0.5C capacity splitting data of the batteries of Example 9 and Example 1, it can be seen that the 0.5C capacity splitting capacity of the battery with Li2S2 as a lithium supplement is lower than the 0.5C capacity splitting capacity of the battery with Li2S as a lithium supplement, and the gram capacity of Li2S2 is lower than that of Li2S, which means that the lower the gram capacity, the more lithium supplement is used.

[0091] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A lithium ion battery, characterized in that: It includes a positive electrode sheet, the positive electrode sheet includes a lithium supplement agent, the lithium supplement agent includes at least one of Li2S, Li2S2, Li2S4, Li2S6, and Li2S8; the addition amount of the lithium supplement agent is W, the gram capacity of the lithium supplement agent is Q, and the capacity loss C of the lithium-ion battery satisfies the relationship: W=1000C / Q; wherein the unit of W is g, the unit of Q is mAh / g, and the unit of C is Ah.

2. A lithium ion battery according to claim 1, characterized in that: The lithium-ion battery capacity loss C and the lithium-ion battery charging current I satisfy the relationship: 0<I<0.3C.

3. A lithium ion battery according to claim 1, characterized in that: The battery operating voltage U is negatively correlated with the gram capacity Q of the lithium supplement.

4. A lithium ion battery according to claim 1, characterized in that: The lithium supplement agent is any one of a pure substance or a mixture, and the mixture includes a lithium sulfur compound soluble in the electrolyte and a lithium sulfur compound insoluble in the electrolyte.

5. A lithium ion battery according to claim 1, characterized in that: The gram capacity Q of the lithium supplement agent ranges from 63 to 1150 mAh / g.

6. A lithium ion battery according to claim 1, characterized in that: The added amount W of the lithium supplement agent ranges from 21 to 80 g.

7. A lithium ion battery according to claim 1, characterized in that: The capacity loss C of the lithium-ion battery ranges from 24 to 45 Ah.

8. A lithium replenishment method for a lithium ion battery according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) During the first charge and discharge, charging is performed at a first preset voltage and a first preset current, and the battery capacity loss C1 is calculated; wherein the first preset voltage is 2.3 to 2.9 V, and the first preset current is 2 to 4 A; 2) Calculate the amount of lithium supplement W1 based on C1, where W1 = C1 / Q1, and Q1 is the gram capacity of the lithium supplement.

9. The lithium replenishing method for a lithium ion battery according to claim 8, characterized in that: The following steps are also included: 3) During cyclic charge and discharge, charging is performed at a second preset voltage and a second preset current, and the battery capacity loss C2 is calculated; wherein the second preset voltage is 2.3 to 3.65 V, and the second preset current is 80 to 84 A; 4) Calculate the amount of lithium supplement W2 based on C2, where W2 = (C1 + C2) / Q2, and Q2 is the gram capacity of the lithium supplement.

10. The lithium replenishing method for a lithium ion battery according to claim 9, characterized in that: During the first charge and discharge, C1 is 22-24Ah; during the cyclic charge and discharge, C2 is 17-20Ah.

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