Formation method of battery and lithium battery

Abstract

The application discloses a battery formation method and a lithium battery. The battery formation method comprises: performing a charge-discharge cycle before battery formation, and the charge-discharge cycle has a charge cut-off voltage of not higher than 2.8 V. The application provides a battery formation method, which is especially suitable for a battery containing LiFSI and a negative electrode film-forming additive in an electrolyte. Through optimization of a battery formation process, the battery is subjected to a charge-discharge cycle at a low potential, and the use of the high-efficiency negative electrode film-forming additive in the electrolyte, the negative electrode film-forming additive can fully react and form a film in the early formation stage, the consumption of LiFSI in the film formation is reduced, the content of the LiFSI film-forming product in the SEI film is reduced while the SEI film is complete and dense, thereby effectively reducing the high reactivity of LiFSI and the film-forming product thereof on the negative electrode side, and improving the safety of the battery containing the LiFSI electrolyte.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a battery formation method and a lithium battery. Background Technology

[0002] Lithium-ion batteries are widely used in portable devices, electronic products, electric vehicles, and other fields due to their high energy density, small size, lack of memory effect, and long cycle life. The electrolyte, as a crucial component of lithium-ion batteries, primarily functions to transport lithium ions and form a solid electrolyte membrane (SEI). It typically consists of three types of substances: lithium salt, solvent, and additives. Among these, the lithium salt largely determines the battery's power density, energy density, cycle life, and safety performance.

[0003] As the requirements for high-temperature performance of battery cells continue to increase, the high-temperature stability of electrolytes is also gradually being improved. Compared with lithium salt LiPF6, lithium bisfluorosulfonyl imide (LiFSI) has attracted widespread attention due to its superior high-temperature stability and higher ionic conductivity. Although LiFSI itself has high high-temperature stability, the stability of the LiFSI interface with the negative electrode has been overlooked, especially its reactivity at full charge. Studies have shown that lithium salt LiFSI in the electrolyte can undergo a violent exothermic reaction with the highly reducing lithium-intercalated negative electrode (e.g., LiC6 + LiFSI), which accelerates the reaction sequence and easily triggers battery thermal runaway.

[0004] Therefore, improving the safety of batteries containing LiFSI in the electrolyte is one of the urgent problems to be solved in the battery field, in order to promote the application of LiFSI in battery electrolytes. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a battery formation method and a lithium battery. This formation method effectively improves the safety of batteries containing LiFSI in the electrolyte. By optimizing the battery formation process, the battery undergoes charge-discharge cycles at low potentials. This promotes the full reaction and film formation of the negative electrode film-forming additives while reducing the consumption of LiFSI during film formation. It forms a complete and dense SEI film while reducing the content of LiFSI film-forming products in the SEI film, thereby effectively reducing the high reactivity of LiFSI and its film-forming products on the negative electrode side and improving the safety of batteries containing LiFSI electrolyte.

[0006] This invention provides the following technical solutions:

[0007] The first aspect of the present invention provides a battery formation method, the formation method comprising: performing charge-discharge cycles during the battery formation stage, wherein the charging cut-off voltage of the charge-discharge cycle is not higher than 2.8V.

[0008] Furthermore, the charge-discharge cycle is preferably performed in the voltage range of 1.5-2.8V.

[0009] Furthermore, the SOC of the battery is ≤5% during the charge-discharge cycle, for example, the battery is charged and discharged between 0% and 5% SOC.

[0010] Furthermore, the charge / discharge rate of the charge / discharge cycle is preferably 0.01C-0.1C, more preferably 0.01C-0.05C.

[0011] Furthermore, the number of charge-discharge cycles is not less than 3 cycles, for example 3-10 cycles, more preferably 3-5 cycles.

[0012] Furthermore, the electrolyte of the battery contains a negative electrode film-forming additive; preferably, the negative electrode film-forming additive accounts for 0.5%-10% of the mass of the electrolyte; more preferably, the negative electrode film-forming additive accounts for 5%-10% of the mass of the electrolyte.

[0013] Further, the negative electrode film-forming additive is selected from one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), n-hexane (DICH), 1,3-propanesulfonate lactone (PS), methane disulfonate methylene (MMDS), toluene diisocyanate (TDI), 1,3-propenesulfonate lactone (PST), tris(trimethylsilane) phosphite (TMSP), and tris(trimethylsilane) borate (TMSB); more preferably, it is VC, FEC, or TDI.

[0014] Furthermore, the electrolyte of the battery contains LiFSI; preferably, the mass percentage of LiFSI in the electrolyte is 10%-20%.

[0015] Furthermore, the electrolyte of the battery may also contain other lithium salts, including but not limited to one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorodioxalate, lithium bis(trifluoromethanesulfonyl)imide, and lithium difluorodioxalate.

[0016] A second aspect of the present invention provides a method for preparing a lithium battery, the method comprising the formation method described in the first aspect.

[0017] A third aspect of the present invention provides a lithium battery prepared by the preparation method described in the second aspect.

[0018] Furthermore, the self-heating initiation temperature of the lithium battery is ≥90℃, or the thermal runaway initiation temperature of the lithium battery is >185℃.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. This invention provides a battery formation method that involves low-potential charge-discharge cycling in the early stages of battery formation. This allows the negative electrode film-forming additives in the electrolyte to fully react and form a complete and dense SEI film. Simultaneously, it reduces or avoids the consumption of lithium salt in the electrolyte during film formation, thereby lowering the content of lithium salt film-forming products in the SEI film and preparing a high-quality SEI film. The formation of a high-quality SEI film effectively isolates the subsequent reaction pathway between lithium salt and the negative electrode, reducing the high reactivity of lithium salt and its film-forming products on the negative electrode side. This reduces the enthalpy change at the lithium salt-negative electrode interface, prolongs the peak temperature, and effectively improves the safety performance of the battery cell.

[0021] 2. The above-mentioned battery formation method is particularly suitable for batteries containing LiFSI in the electrolyte. It solves the safety hazards caused by the high reactivity of LiFSI with the negative electrode from the battery preparation stage. The method is simple to operate, easy to implement, and can effectively improve the safety of batteries containing LiFSI electrolyte, and has great application value. Detailed Implementation

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. "Comprising" or "containing" as used herein means that it may include or contain other components in addition to the stated components. "Comprising" or "containing" as used herein may also be replaced with the closed form "is" or "consisting of".

[0023] As described in the background section, although LiFSI itself has high high-temperature stability, the lithium salt LiFSI in the electrolyte will undergo a violent exothermic reaction with the lithium-intercalated anode with strong reducing properties, which will advance the reaction sequence and easily trigger battery thermal runaway. Therefore, it greatly limits the practical application of LiFSI in lithium batteries.

[0024] To address the aforementioned technical problems, the present invention provides a battery formation method in the embodiment section, the formation method comprising: performing charge-discharge cycles during the battery formation stage, wherein the charging cut-off voltage of the charge-discharge cycle is not higher than 2.8V.

[0025] This invention addresses the safety hazards posed by the high reactivity of lithium salts and the negative electrode from the battery fabrication stage. Specifically, it involves low-potential (no higher than 2.8V) charge-discharge cycles during the early stages of battery formation, allowing the negative electrode film-forming additives in the electrolyte to fully react and form a complete and dense SEI film, thus improving the quality of the SEI film. Simultaneously, it reduces or avoids the consumption of lithium salts in the electrolyte during film formation, thereby lowering the content of lithium salt film-forming products in the SEI film. The formation of a high-quality SEI film with low lithium salt film-forming product content effectively isolates the subsequent reaction pathway between lithium salts and the negative electrode, reducing the high reactivity of lithium salts and their film-forming products on the negative electrode side. This reduces the enthalpy change at the lithium salt-negative electrode interface, prolongs the peak temperature, and effectively improves the safety performance of the battery cell. This battery formation method is particularly suitable for all batteries containing LiFSI electrolytes, effectively improving the safety of batteries containing LiFSI electrolytes.

[0026] In this invention, the charge-discharge cycle is preferably carried out in the voltage range of 1.5-2.8V, which is lower than the film formation potential of lithium salt (e.g., LiFSI), thereby reducing the consumption of lithium salt during the film formation process and allowing the negative electrode film-forming additive to fully react and form a film.

[0027] In this invention, the charge / discharge rate of the charge / discharge cycle is preferably 0.01C-0.1C, more preferably 0.01C-0.05C. The charge / discharge rate during the low-potential charge / discharge cycle affects film formation quality and efficiency. If the charge / discharge rate is too low, the film formation efficiency is low, which is detrimental to actual production. If the charge / discharge rate is too high, it will reduce film formation quality. Therefore, to improve efficiency while ensuring film formation quality, it is preferable to control the charge / discharge rate of the low-potential charge / discharge cycle within the range of 0.01-0.1C, more preferably 0.01C-0.05C.

[0028] In this invention, the SOC of the battery is ≤5% during the charge-discharge cycle. For example, the battery is charged and discharged between 0-5% SOC, 1%-5% SOC, or 2%-4% SOC. For example, the battery is charged to 5% SOC and then discharged to 0% SOC to perform a charge-discharge cycle.

[0029] In this invention, the number of charge-discharge cycles is not less than 3 cycles, for example, 3-10 cycles, more preferably 3-5 cycles. To ensure the sufficient reaction of the film-forming additives at low potential and the integrity of the formed SEI film, it is necessary to control the appropriate number of charge-discharge cycles, for example, not less than 3 cycles. Under the same conditions, when the SEI film is not dense, continuing to increase the number of charge-discharge cycles will improve the quality of the SEI film and reduce the subsequent consumption of lithium salt, and can more effectively block the reaction of lithium salt, increasing the onset temperature of cell thermal runaway. When a dense SEI film has been formed, continuing to increase the number of charge-discharge cycles will make it difficult to further improve the quality of the SEI film and will reduce production efficiency. Therefore, to balance the quality of the SEI film and production efficiency, it is preferable to control the number of low-potential charge-discharge cycles to 3-10 cycles, more preferably 3-5 cycles, for example, 3 cycles, 4 cycles, or 5 cycles.

[0030] In this invention, the electrolyte of the battery contains a negative electrode film-forming additive; preferably, the mass percentage of the negative electrode film-forming additive in the electrolyte is 0.5%-10%, for example, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., including but not limited to the values ​​listed above, and may also be other values ​​within the above mass percentage range; more preferably, it is 5%-10%. This invention, by adding a sufficient amount of negative electrode film-forming additive to the electrolyte, enables the formation of a complete and dense SEI film on the negative electrode surface during low-potential charge-discharge cycles, thereby reducing the reaction of lithium salt with the negative electrode at high potentials during the formation stage and reducing the consumption of lithium salt by the SEI film.

[0031] In this invention, the film-forming additive can be selected from one or more of the following: vinylene carbonate (VC), fluoroethylene carbonate (FEC), n-hexane (DICH), 1,3-propanesulfonate lactone (PS), methanedisulfonate methylene (MMDS), toluene diisocyanate (TDI), 1,3-propenesulfonate lactone (PST), tris(trimethylsilane) phosphite (TMSP), and tris(trimethylsilane) borate (TMSB). For example, VC, FEC, or TDI can be added to the electrolyte. These film-forming additives have low film-forming potentials and can fully react and form a film during low-potential charge-discharge cycles, thus forming a high-quality SEI film.

[0032] In this invention, the electrolyte of the battery contains LiFSI. When fully charged, LiFSI has high reactivity with the negative electrode. Therefore, the quality of the SEI film and the content of LiFSI film-forming products in the SEI film directly affect the safety of the battery. The improved formation method described above can effectively improve the quality of the negative electrode SEI film containing LiFSI in the electrolyte, and can greatly reduce or avoid the consumption of LiFSI during the SEI film formation process, reduce the content of LiFSI film-forming products in the SEI film, thereby effectively isolating the subsequent reaction path between LiFSI and the negative electrode, reducing the high reactivity of LiFSI and its film-forming products on the negative electrode side, thereby reducing the reaction enthalpy change at the LiFSI-negative electrode interface, prolonging the peak temperature, and effectively improving the safety performance of the cell.

[0033] In this invention, the mass percentage of LiFSI in the electrolyte is 10%-20%, such as 10%, 11%, 11.5%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., including but not limited to the values ​​listed above, and may also be other values ​​within the above mass percentage range.

[0034] In this invention, the electrolyte of the battery may also contain other lithium salts, including but not limited to one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorodioxalate, lithium bis(trifluoromethanesulfonyl)imide, and lithium difluorodioxalate.

[0035] The present invention also provides a method for preparing a lithium battery in the embodiment section, which includes the above-described formation method.

[0036] In addition, the present invention also provides a lithium battery in the embodiment section, which is obtained by the above preparation method.

[0037] In this invention, the self-heating initiation temperature of the lithium battery is ≥90℃, or the thermal runaway initiation temperature of the lithium battery is >185℃, which has better safety performance.

[0038] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0039] Example 1

[0040] This embodiment relates to the preparation of a lithium battery, and the specific operations are as follows:

[0041] (1) Preparation of positive electrode sheet: The positive electrode active material NCM (811), binder polyvinylidene fluoride (PVDF), conductive carbon black and single-walled carbon nanotubes are mixed in a weight ratio of 97.2:1.5:1.2:0.1, and then N-methylpyrrolidone (NMP) is added. The mixture is stirred under vacuum until the mixture becomes a uniform and fluid positive electrode slurry. The positive electrode slurry is uniformly coated on the current collector aluminum foil. The coated aluminum foil is baked in an oven with 5 different temperature gradients, and then dried in an oven at 120°C for 8 hours. The positive electrode sheet is then obtained by rolling and slitting.

[0042] (2) Preparation of negative electrode sheet: The negative electrode active material graphite, the thickener sodium carboxymethyl cellulose (CMC-Na), the binder styrene-butadiene rubber, and the conductive agent acetylene black are mixed in a weight ratio of 97:1:1:1, deionized water is added, and a negative electrode slurry is obtained under the action of a vacuum stirrer; the negative electrode slurry is uniformly coated on a high-strength carbon-coated copper foil to obtain an electrode sheet; the obtained electrode sheet is dried at room temperature and then transferred to an 80℃ oven for drying for 10 hours, and then rolled and slit to obtain a negative electrode sheet.

[0043] (3) Electrolyte preparation: In a glove box filled with inert gas (H2O < 10 ppm, O2 < 5 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Then, LiFSI based on 13.75% of the total weight of the electrolyte is slowly added to the mixed solution. After the moisture and free acid are tested and found to be qualified, the basic electrolyte is obtained. Film-forming additive VC with a mass ratio of 0.5% is added to the basic electrolyte to obtain the electrolyte.

[0044] (4) Battery fabrication: The prepared positive electrode, separator (9-micron thick PP film), and negative electrode are stacked in sequence, ensuring that the separator acts as a separator between the positive and negative electrodes. The bare cell is placed in an aluminum-plastic film outer packaging. The prepared electrolyte is injected into the dried battery. The battery is then encapsulated, allowed to stand, formed, shaped, and tested for capacity to complete the fabrication of the lithium-ion soft-pack battery. During the early formation stage, the battery undergoes three perturbation cycles at a charge-discharge rate of 0.01C within the range of 1.5V-2.8V, corresponding to a battery capacity of 0-5% SOC.

[0045] Example 2

[0046] This embodiment relates to the preparation of a lithium battery, and the only difference from Embodiment 1 is that the content of the film-forming additive VC in the electrolyte is 2%.

[0047] Example 3

[0048] This embodiment relates to the preparation of a lithium battery, and the only difference from Example 1 is that the content of the film-forming additive VC in the electrolyte is 5%.

[0049] Example 4

[0050] This embodiment relates to the preparation of a lithium battery, and the only difference from Embodiment 1 is that the number of perturbation cycles at the low potential during the early stage of formation is 5.

[0051] Example 5

[0052] This embodiment relates to the preparation of a lithium battery, and the only difference from Embodiment 1 is that the number of perturbation cycles at the low potential during the early stage of formation is 10.

[0053] Example 6

[0054] This embodiment relates to the preparation of a lithium battery, which differs from Embodiment 1 only in that: during the early stage of formation, the battery is subjected to three perturbation cycles at a charge-discharge rate of 0.05C within a range of 1.5V-2.8V, corresponding to a battery capacity of 0-5% SOC.

[0055] Example 7

[0056] This embodiment relates to the preparation of a lithium battery, which differs from Embodiment 1 only in that: during the early stage of formation, the battery is subjected to three perturbation cycles at a charge-discharge rate of 0.1C within a range of 1.5V-2.8V, and the corresponding battery capacity is 0-5% SOC.

[0057] Example 8

[0058] This embodiment relates to the preparation of a lithium battery, which differs from Embodiment 1 only in that the film-forming additive in the electrolyte is FEC, and the content is 2%.

[0059] Example 9

[0060] This embodiment relates to the preparation of a lithium battery, which differs from Embodiment 1 only in that the film-forming additive in the electrolyte is FEC, and the content is 10%.

[0061] Example 10

[0062] This embodiment relates to the preparation of a lithium battery, and the only difference from Embodiment 1 is that the film-forming additive in the electrolyte is TDI, and the content is 1%.

[0063] Comparative Example 1

[0064] This comparative example relates to the preparation of a lithium battery, which differs from Example 2 only in that it involves undisturbed cycling during the battery formation stage.

[0065] Comparative Example 2

[0066] This comparative example relates to the preparation of a lithium battery, which differs from Example 1 only in that no film-forming additives are added to the electrolyte, and there is no turbulent cycling operation during the battery formation stage.

[0067] Comparative Example 3

[0068] This comparative example relates to the preparation of a lithium battery, which differs from Example 1 only in that: during the early stage of formation, the battery is subjected to three perturbation cycles at a charge-discharge rate of 0.1C within the range of 2.8V-3.3V, corresponding to a battery capacity of 5-15% SOC.

[0069] The types, contents, and disturbance cycle-related parameters of the film-forming additives in Examples 1-10 and Comparative Examples 1-3 are summarized in Table 1 below:

[0070] Table 1

[0071]

[0072] Performance testing

[0073] The lithium-ion batteries prepared in the above examples and comparative examples were subjected to ARC and DSC tests, respectively. The specific procedures are as follows:

[0074] Insulation thermal astronomy test: The above-mentioned battery cell was fully charged at a rate of 0.33C and a cutoff voltage of 4.25V and then subjected to ARC test. The self-heating initiation temperature (T1) and thermal runaway initiation temperature (T2) of the battery cell were obtained through ARC test.

[0075] DSC Test: The above-mentioned battery cell was fully charged at a rate of 0.33C and a cutoff voltage of 4.25V. It was then disassembled inside a glove box, and the fully charged negative terminal was punched using a 3mm diameter punching machine and placed in a gold-plated crucible. 5µL of electrolyte (EC:EMC:DEC = 3:5:2 + 13.75% LiFSI) was added to the crucible for DSC testing.

[0076] The test results are shown in Table 2 below:

[0077] Table 2

[0078]

[0079] As shown in Tables 1 and 2, by adding an appropriate amount of film-forming agent to the electrolyte containing LiFSI to synergistically induce low-potential disturbance cycles in the early stage of formation, the self-heating initiation temperature, thermal runaway initiation temperature, and peak temperature of the battery cell can be effectively increased, thereby effectively improving the safety of the battery cell.

[0080] As shown in Examples 1-3 and Examples 8 and 9, the self-heating initiation temperature, thermal runaway initiation temperature, and peak temperature of the battery cell all increase with the increase of the film-forming additive content. For example, when the VC content is increased from 0.5% (Example 1) to 2% (Example 2), T1, T2, and peak temperature all increase significantly. Further increasing the VC content in the electrolyte to 5% (Example 3), compared to Example 2, although T1, T2, and peak temperature all increase, the magnitude of the increase is significantly reduced. Therefore, within a certain addition range, increasing the film-forming additive content can effectively suppress the reaction between LiFSI and the negative electrode.

[0081] As shown in Examples 4 and 5, increasing the number of low-potential perturbation cycles in the early formation stage, even with a small amount of additives, can promote the efficient utilization of film-forming additives, resulting in a higher quality SEI film and thus suppressing side reaction activity. Furthermore, adjusting the charge / discharge rate of the perturbation cycle can improve efficiency, but it also affects film quality. For example, compared to Example 6, increasing the charge / discharge rate from 0.05C to 0.1C in Example 7 resulted in lower T1, T2, and peak temperatures for the battery cell compared to Example 6. In addition, as shown in Examples 2, 8, and 10, the effects of adding FEC and TDI are superior to VC, suggesting that the SEI formed by FEC and TDI is of higher quality, thereby improving the safety of the corresponding battery cell.

[0082] Compared to Example 2, Comparative Example 1 did not undergo low-potential perturbation cycling during battery formation. The resulting cell had significantly lower T1, T2, and peak temperatures than Example 2, with differences reaching 15-20°C. This is because the film-forming additives added to the electrolyte were not efficiently utilized, and LiFSI was consumed during SEI film formation, resulting in a low-quality SEI film that could not effectively isolate the subsequent side reactions between LiFSI and the negative electrode at high temperatures. Compared to Comparative Example 1, Comparative Example 2 did not add film-forming additives to the electrolyte, resulting in even lower T1, T2, and peak temperatures. At lower temperatures, the LiFSI in the electrolyte reacts exothermically with the negative electrode.

[0083] As can be seen from Example 1 and Comparative Example 3, the effect of perturbation cycling at a relatively high potential during the formation stage is not as good as that of Comparative Example 1, which did not perform low potential perturbation cycling. This is because under high potential perturbation, the additive and lithium salt are consumed to form a film at the same time. However, the rapid insertion and extraction of lithium ions under high potential perturbation reduces the quality of SEI film formation, which is not conducive to film protection, and causes LIFSI to undergo an exothermic reaction at a lower temperature.

[0084] In summary, this invention enables the negative electrode film-forming additives to fully react by performing low-potential charge-discharge cycles during the battery formation stage, while avoiding the consumption of lithium salts, thereby preparing a high-quality, low-reactivity SEI film. This effectively improves battery safety, especially the safety of batteries containing LiFSI in the electrolyte, and can effectively solve the safety hazards caused by the high reactivity of LiFSI with the negative electrode from the battery preparation stage.

[0085] The embodiments described above are merely preferred examples to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for forming a battery, characterized in that, The formation method includes: performing charge-discharge cycles in the early stage of battery formation, wherein the charging cut-off voltage of the charge-discharge cycle is not higher than 2.8 V; the electrolyte of the battery contains a negative electrode film-forming additive; the negative electrode film-forming additive is selected from one or more of vinylene carbonate, fluoroethylene carbonate, n-hexane, 1,3-propanesulfonate lactone, methanedisulfonate methylene, toluene diisocyanate, 1,3-propenesulfonate lactone, tris(trimethylsilane)phosphite, and tris(trimethylsilane)borate; the electrolyte of the battery contains LiFSI; the mass percentage of LiFSI in the electrolyte is 10%-20%.

2. The formation method according to claim 1, characterized in that, The charge-discharge cycle is performed in the voltage range of 1.5-2.8 V.

3. The formation method according to claim 1, characterized in that, The charge / discharge rate of the charge / discharge cycle is 0.01C-0.1C.

4. The formation method according to claim 3, characterized in that, The charge / discharge rate of the charge / discharge cycle is 0.01C-0.05C.

5. The formation method according to claim 1, characterized in that, The number of charge-discharge cycles is not less than 3.

6. The formation method according to claim 5, characterized in that, The number of charge-discharge cycles is 3-5.

7. The formation method according to claim 1, characterized in that, The negative electrode film-forming additive accounts for 0.5%-10% of the mass of the electrolyte.

8. The formation method according to claim 7, characterized in that, The negative electrode film-forming additive accounts for 5%-10% of the mass of the electrolyte.

9. A method for preparing a lithium battery, characterized in that, The preparation method comprises the formation method according to any one of claims 1-8.

10. A lithium battery, characterized in that, The lithium battery is prepared by the preparation method described in claim 9.

11. The lithium battery according to claim 10, characterized in that, The self-heating initiation temperature of the lithium battery is ≥90℃, or the thermal runaway initiation temperature of the lithium battery is >185℃.

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