Fluorine-containing soluble polyimide adhesive special for lithium ion battery and preparation method and application of fluorine-containing soluble polyimide adhesive

Abstract

The invention relates to the field of lithium ion batteries, in particular to a fluorine-containing soluble polyimide adhesive special for a lithium ion battery as well as a preparation method and application of the fluorine-containing soluble polyimide adhesive. The fluorine-containing soluble polyimide adhesive is prepared by reacting dianhydride with diamine; the structure of the fluorine-containing soluble polyimide adhesive is shown in the specification. The polyimide obtained by the invention can be used for an adhesive material, an electrode material prepared from the polyimide has high adhesive property and fatigue resistance, a lithium ion battery assembled by using the polyimide has higher multiplying power, and the adhesive material is applied to the lithium ion battery, especially the lithium ion battery containing a silicon-carbon negative electrode, and has a good application prospect in the field of lithium ion batteries. Excellent rate capability and adhesive property are shown, and the method has a good industrial prospect. # imgabs0 #

Description

[0001] The present invention relates to the field of lithium-ion batteries, and particularly to a novel binder based on polyimide (PI), specifically a fluorine-containing soluble polyimide binder for lithium-ion batteries, its preparation method and applications. Background Art

[0002] Among the key components of batteries, the silicon-based anode has attracted much attention due to its unique lithium storage mechanism. Compared with the traditional graphite material where 6 carbon atoms are required to fix 1 lithium ion, a silicon atom can accommodate 4 lithium ions, achieving a theoretical specific capacity of up to 4200 mAh / g. This value far exceeds the lithium storage capabilities of artificial graphite (310 - 360 mAh / g) and natural graphite (340 - 370 mAh / g), showing revolutionary potential for energy density improvement. However, the industrialization process of silicon anodes faces three major technical barriers: First, the volume deformation of up to 300% during charge and discharge easily leads to the destruction of the electrode structure; second, the insufficient intrinsic conductivity restricts the charge transfer efficiency; third, the surface is prone to oxidation, which exacerbates side reactions. These defects are specifically manifested as problems such as electrode pulverization, dynamic reconstruction of the SEI film, and failure of the conductive network. The current countermeasures mainly focus on three dimensions: alleviating mechanical stress through nanometer modification (such as nano-silicon particles); constructing a stable solid electrolyte layer using interface engineering; and optimizing the electrolyte components to improve the initial coulombic efficiency (ICE) value.

[0003] It is worth noting that the innovation of the binder system plays a crucial role in solving the above problems. The limitations of the traditional binder PVDF are mainly reflected in the intermolecular interaction mechanism: there is only a weak van der Waals interaction between it and the active substance, making it difficult to withstand the repeated stress impacts during cycling. The weakness of this binding force directly leads to the shedding of active substances, the rupture of the SEI film, and continuous electrolyte decomposition, ultimately resulting in rapid capacity decay. In response, researchers have successively developed new binding systems: The Drofenik team pioneered the application of sodium carboxymethyl cellulose (CMC) to the graphite system in 2003. This linear polysaccharide derivative forms a unique binding network through the carboxymethyl substitution of β - pyranose glucose residues, providing ideas for subsequent research on silicon-based systems.

[0004] Chinese Patent CN119463793A discloses a fluorine-containing soluble polyimide binder for lithium batteries, its preparation method and applications. The fluorine-containing polyimide is prepared by the reaction of dianhydride and diamine. The dianhydride includes 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and the diamine includes 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane. The structure of the fluorine-containing polyimide in the binder is shown in Formula I:

[0005] Among them, the groups A and B are independently selected from and A is different from B. However, compared with the present invention, the rate performance of the silicon anode lithium-ion battery using the fluorine-containing soluble polyimide of this patent as an adhesive is worse.

[0006] Chinese Patent CN119463794A discloses a fluorine-containing soluble polyimide adhesive special for lithium batteries, its preparation method and application. The fluorine-containing polyimide is prepared by reacting a dianhydride with a diamine. The dianhydride includes 4,4'-hexafluoroisopropyl phthalic anhydride (6FDA), and the diamine includes 4,4'-diaminodiphenylamine (NDA). The structural formula of the fluorine-containing polyimide (6FDA-NDA) is:

[0007]

[0008] However, compared with the present invention, the peel strength performance of the polyimide adhesive material prepared by this patent is worse.

[0009] In the exploration of polymers, polyimide (PI) exhibits excellent mechanical strength and thermal stability due to its aromatic ring-imide rigid structure. However, its inherent low ionic conductivity and electronic conductivity limit the electrode kinetic performance. The current research focus is on balancing its adhesion strength and conductive properties through molecular structure modification (such as introducing flexible segments or functional groups), which provides a new breakthrough for the development of high-performance composite bonding systems. Summary of the Invention

[0010] In view of the technical problems encountered in the practical application of high-energy-density lithium-ion batteries, the present invention designs a fluorine-containing soluble polyimide bonding material. The main chain of this adhesive material contains a -(R)NR'-C(O)-R'N(R)- structure. The existence of this structure makes the polyimide material more chemically compatible with silicon particles. Its huge polar effect can generate more hydrogen bonds, improving the adhesion of the polyimide, helping to form a more stable interfacial bond. The electrode material prepared with the fluorine-containing soluble polyimide bonding material has high bonding characteristics and high stability. The assembled lithium battery exhibits a higher rate and is an effective solution for a silicon anode adhesive with high stability, high capacity and suitable for large-scale production.

[0011] The first object of the present invention is to provide a fluorine-containing soluble polyimide adhesive special for lithium-ion batteries. The fluorine-containing soluble polyimide adhesive is prepared by reacting a dianhydride with a diamine. The structure of the fluorine-containing soluble polyimide adhesive is as follows:

[0012]

[0013] Among them,

[0014] is

[0015] -R'- is -C m H 2m -, m are each independently selected from 0, 1 or 2;

[0016] -R are each independently selected from -H, -CH 3 or -COO(CH 3 ) 3 ;

[0017] n is a positive integer.

[0018] Preferably, the fluorine-containing soluble polyimide adhesive is selected from any one of 6FDA-BAEPU, 6FCDA-BAEPU, 6FDA-BAEPU-BOC, 6FCDA-BAEPU-BOC, 6FDA-DMAPU, 6FCDA-DMAPU;

[0019] The structural formula of the 6FDA-BAEPU is:

[0020]

[0021] The structural formula of the 6FCDA-BAEPU is:

[0022]

[0023] The structural formula of the 6FDA-BAEPU-BOC is:

[0024]

[0025] The structural formula of the 6FCDA-BAEPU-BOC is:

[0026]

[0027] The structural formula of the 6FDA-DMAPU is:

[0028]

[0029] The structural formula of the 6FCDA-DMAPU is:

[0030]

[0031] More preferably, the dianhydride is selected from any one of 6FDA, 6FCDA; the diamine is selected from any one of BAEPU, BAEPU-BOC, DMAPU.

[0032] The second object of the present invention is to provide a method for preparing the above-mentioned fluorine-containing soluble polyimide adhesive, which comprises the following steps:

[0033] (1) Mix a dianhydride, a diamine and an aprotic polar solvent to carry out a polycondensation reaction;

[0034] (2) After the polycondensation reaction is completed, add a catalyst and a dehydrating agent and react to obtain the fluorine-containing soluble polyimide adhesive.

[0035] Preferably, the aprotic polar solvent in step (1) is selected from at least one of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and N,N-dimethylacetamide (DMAc).

[0036] Preferably, the reaction temperature in step (1) is room temperature, preferably 25 °C; the reaction time is 12 - 24 h, preferably 16 h; the rotation speed is 50 - 300 r / min, preferably 280 r / min.

[0037] Preferably, the catalyst in step (2) is selected from at least one of pyridine, isoquinoline, and methylpyridine.

[0038] Preferably, the dehydrating agent in step (2) is acetic anhydride.

[0039] Preferably, the reaction time in step (2) is 12 - 24 h, preferably 16 h; the rotation speed is 50 - 300 r / min, preferably 280 r / min.

[0040] The third object of the present invention is to provide the application of the above-mentioned fluorine-containing soluble polyimide adhesive in a lithium-ion battery.

[0041] Preferably, the lithium-ion battery is a silicon-carbon negative electrode lithium-ion battery.

[0042] Preferably, the lithium-ion battery is a silicon negative electrode lithium-ion battery.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The main chain of the fluorine-containing soluble polyimide adhesive material of the present invention contains a -(R)NR’-C(O)-R’N(R)- structure. The existence of this structure makes the polyimide material more chemically compatible with silicon particles. Its huge polar effect can generate more hydrogen bonds, improving the adhesion of the polyimide and helping to form a more stable interfacial bond.

[0045] (2) The electrode material prepared with the fluorine-containing soluble polyimide adhesive of the present invention has high bonding characteristics and anti-fatigue characteristics, and the assembled lithium battery shows a higher rate performance. The present invention is an effective solution for silicon anode adhesives with high anti-fatigue, high capacity and suitable for large-scale production. Description of the Drawings

[0046] Figure 1 It is a graph of the battery rate performance of the PI adhesive materials prepared in Examples 1-6 and Comparative Examples 1-4.

[0047] Figure 2 It is an infrared structural characterization diagram of the PI adhesive materials prepared in Examples 1-6. Detailed Description of the Invention

[0048] The following further describes in detail the specific embodiments of the present invention in conjunction with the embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0049] Unless otherwise specified, the methods are all conventional methods. Unless otherwise specified, the materials can all be obtained from public commercial channels.

[0050] The performance evaluation methods of the fluorine-containing soluble polyimide (PI) adhesive materials obtained in the following embodiments are as follows:

[0051] Electrochemical performance evaluation method of PI adhesive materials: The rate performance test is measured by a Blue Electric test system CT3002A, and the test conditions are to charge and discharge 5 cycles at current densities of 0.1C, 0.5C, 1C, 2C, 5C, and 0.1C respectively.

[0052] Peeling strength performance evaluation method of PI adhesive materials: Stick a 5 cm long, 2 cm wide, and 1 mm thick 3M tape on the dried battery electrode sheet, connect the other end of the tape to a tensile machine, and peel the slurry on the surface of the electrode sheet at a constant speed (5 cm / min) at an angle of 180°. The force of the tensile machine starts from 0 N and gradually increases until the tape completely falls off the electrode sheet, and record the average force during the peeling process.

[0053] Molecular weight test: Waters GPC test system, solvent DMF, flow rate 1 mL / min, column temperature 40 °C.

[0054] Example 1 Preparation of PI adhesive material with 6FDA and BAEPU

[0055] Weigh 14.9195 g of 1,3-bis(4-aminophenethyl)urea (BAEPU) and place it in a round-bottom flask. Add an appropriate amount of DMAc solvent to dissolve it under stirring conditions. Weigh 22.2120 g of 4,4'-hexafluoroisopropyl phthalic anhydride (6FDA) and add it to the above device. The stirring paddle speed is 280 r / min, and the reaction time is 16 h. Subsequently, add 10.2 g of acetic anhydride and 7.91 g of pyridine to this device, keep the rotation speed unchanged, and continue stirring for 16 h. After the reaction is completed, pour the obtained sol into an anhydrous ethanol solution for precipitation to obtain a fluorine-containing soluble PI adhesive material.

[0056] Take the prepared PI adhesive material and dissolve it in an NMP solution to prepare a solution with a PI content of 0.2 g / mL. According to the weight ratio of active material (Si / C, reversible specific capacity 650 mAh / g): conductive agent (Super P): adhesive (PI) = 5:4:1, take an appropriate amount and place it in a 20 mL small glass bottle. Stir magnetically at 600 r / min for 12 h to fully mix the electrode slurry. Then, uniformly coat the slurry on a carbon-coated copper foil with a 150-micron-thick scraper, place it in a vacuum oven, heat it at 120 °C for 10 h to obtain a dried electrode sheet. After that, use a knife head to cut it and then put it back into the vacuum oven for 30 min to remove moisture. Subsequently, assemble the battery in a glove box and test the rate performance.

[0057] The rate performance is as shown in the appendix Figure 1 as follows;

[0058] The peel strength performance of the prepared PI adhesive material is shown in Table 1, and the infrared structural characterization is as Figure 2 .

[0059] Example 2: Prepare a PI adhesive material using 6FCDA and BAEPU

[0060] Weigh 14.9195 g of 1,3-bis(4-aminophenethyl)urea (BAEPU) and place it in a round-bottom flask. Add an appropriate amount of DMAc solvent to dissolve it under stirring conditions. Weigh 22.9110 g of 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic dianhydride (6FCDA) and add it to the above device. The stirring paddle speed is 280 r / min, and the reaction time is 16 h. Subsequently, add 10.2 g of acetic anhydride and 7.91 g of pyridine to this device, keep the rotation speed unchanged, and continue stirring for 16 h. After the reaction is completed, pour the obtained sol into an anhydrous ethanol solution for precipitation to obtain a fluorine-containing soluble PI adhesive material.

[0061] The subsequent steps of preparing the electrode sheet and assembling the battery are the same as those in Example 1.

[0062] The rate performance is as shown in the appendix Figure 1 as follows;

[0063] The peel strength performance of the prepared PI adhesive material is shown in Table 1, and the infrared structural characterization is as Figure 2 .

[0064] In Example 3, 6FDA and BAEPU-BOC were used to prepare the PI adhesive material

[0065] Weigh 19.9255 g of 1-tert-butoxycarbonyl-1,3-bis(4-aminophenylethyl)urea (BAEPU-BOC) and place it in a round-bottom flask. Add an appropriate amount of DMAc solvent to dissolve it under stirring conditions. Weigh 22.2120 g of 4,4-hexafluoroisopropyl phthalic anhydride (6FDA) and add it to the above device. The stirring paddle speed is 280 r / min, and the reaction time is 16 h. Subsequently, add 10.2 g of acetic anhydride and 7.91 g of pyridine to the device, keep the rotation speed unchanged, and continue stirring for 16 h. After the reaction is completed, pour the obtained sol into an anhydrous ethanol solution for precipitation to obtain a fluorine-containing soluble PI adhesive material.

[0066] The subsequent steps of preparing the electrode plate and assembling the battery are the same as those in Example 1.

[0067] The rate performance is as shown in the appendix Figure 1 ;

[0068] The peel strength performance of the prepared PI adhesive material is shown in Table 1, and the infrared structural characterization is as Figure 2 .

[0069] In Example 4, the PI adhesive material prepared with 6FCDA and BAEPU-BOC

[0070] Weigh 19.9255 g of 1-tert-butoxycarbonyl-1,3-bis(4-aminophenylethyl)urea (BAEPU-BOC) and place it in a round-bottom flask. Add an appropriate amount of DMAc solvent to dissolve it under stirring conditions. Weigh 22.9110 g of 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic dianhydride (6FCDA) and add it to the above device. The stirring paddle speed is 280 r / min, and the reaction time is 16 h. Subsequently, add 10.2 g of acetic anhydride and 7.91 g of pyridine to the device, keep the rotation speed unchanged, and continue stirring for 16 h. After the reaction is completed, pour the obtained sol into an anhydrous ethanol solution for precipitation to obtain a fluorine-containing soluble PI adhesive material.

[0071] The subsequent steps of preparing the electrode plate and assembling the battery are the same as those in Example 1.

[0072] The rate performance is as shown in the appendix Figure 1 ;

[0073] The peel strength performance of the prepared PI adhesive material is shown in Table 1, and the infrared structural characterization is as Figure 2 .

[0074] Example 5 Preparation of PI Adhesive Material Using 6FDA and DMAPU

[0075] Weigh 13.519 g of N,N'-dimethyl-N,N'-bis(4-aminophenyl)urea (DMAPU) and place it in a round-bottom flask. Add an appropriate amount of DMAc solvent to dissolve it under stirring conditions. Weigh 22.2120 g of 4,4-hexafluoroisopropyl phthalic anhydride (6FDA) and add it to the above device. The rotation speed of the stirring paddle is 280 r / min, and the reaction time is 16 h. Subsequently, add 10.2 g of acetic anhydride and 7.91 g of pyridine to this device, keep the rotation speed unchanged, and continue stirring for 16 h. After the reaction is completed, pour the obtained sol into an anhydrous ethanol solution for precipitation to obtain a fluorine-containing soluble PI adhesive material.

[0076] The subsequent steps of preparing the electrode plate and assembling the battery are the same as those in Example 1.

[0077] The rate performance is as shown in the appendix Figure 1 as follows;

[0078] The peel strength performance of the prepared PI adhesive material is shown in Table 1, and the infrared structure characterization is as shown in Figure 2 .

[0079] Example 6 PI Adhesive Material Prepared Using 6FCDA and DMAPU

[0080] Weigh 13.519 g of N,N'-dimethyl-N,N'-bis(4-aminophenyl)urea (DMAPU) and place it in a round-bottom flask. Add an appropriate amount of DMAc solvent to dissolve it under stirring conditions. Weigh 22.9110 g of 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic dianhydride (6FCDA) and add it to the above device. The rotation speed of the stirring paddle is 280 r / min, and the reaction time is 16 h. Subsequently, add 10.2 g of acetic anhydride and 7.91 g of pyridine to this device, keep the rotation speed unchanged, and continue stirring for 16 h. After the reaction is completed, pour the obtained sol into an anhydrous ethanol solution for precipitation to obtain a fluorine-containing soluble PI adhesive material.

[0081] The subsequent steps of preparing the electrode plate and assembling the battery are the same as those in Example 1.

[0082] The rate performance is as shown in the appendix Figure 1 as follows;

[0083] The peel strength performance of the prepared PI adhesive material is shown in Table 1, and the infrared structure characterization is as shown in Figure 2 .

[0084] Comparative Example 1 Polyvinylidene Fluoride (PVDF) as a Lithium Ion Battery Adhesive

[0085] The PVDF in Comparative Example 1 is a product produced by Arkema France. PVDF was dissolved in NMP solution to prepare a solution with a PVDF content of 0.2 g / mL. An appropriate amount was taken according to the weight ratio of active material (Si / C, standard specific capacity 650 mAh / g): conductive agent (SuperP): binder (PVDF) = 5:4:1 and placed in a 20 mL small glass bottle, and magnetically stirred for 10 h to prepare an electrode slurry. Subsequently, the slurry was evenly coated on a carbon-coated copper foil with a 150-micron-thick scraper and placed in a vacuum oven at 120 °C for 10 h to obtain a dried electrode sheet. Subsequently, the battery was assembled in a glove box to test the rate performance.

[0086] The rate performance is as shown in the appendix Figure 1 as follows;

[0087] The specific data of the peel strength performance are listed in Table 1.

[0088] In Comparative Example 2, carboxymethyl cellulose (CMC) was used as a lithium-ion battery binder

[0089] The CMC in Comparative Example 2 was purchased from Kejingxing Technology Co., Ltd. (Shenzhen). CMC was dissolved in deionized water to prepare a solution with a CMC content of 0.2 g / mL. An appropriate amount was taken according to the weight ratio of active material (Si / C, standard specific capacity 650 mAh / g): conductive agent (SuperP): binder (CMC) = 5:4:1 and placed in a 20 mL small glass bottle, and magnetically stirred for 10 h to prepare an electrode slurry. Subsequently, the slurry was evenly coated on a carbon-coated copper foil with a 150-micron-thick scraper and placed in a vacuum oven at 120 °C for 10 h to obtain a dried electrode sheet. Subsequently, the battery was assembled in a glove box to test the rate performance.

[0090] The rate performance is as shown in the appendix Figure 1 as follows;

[0091] The specific data of the peel strength performance are listed in Table 1.

[0092] In Comparative Example 3, a PI binder material was prepared using 6FDA and NDA

[0093] 9.9625 g of 4,4'-diaminodiphenylamine (NDA) was placed in a round-bottom flask and dissolved by adding an appropriate amount of DMAc solvent under stirring conditions. 22.21 g of 4,4-hexafluoroisopropyl phthalic anhydride (6FDA) was weighed and added to the above device, and the stirring paddle speed was 280 r / min, and the reaction time was 16 h. Subsequently, 10.2 g of acetic anhydride and 7.91 g of pyridine were added to the device, and the rotation speed was kept unchanged, and stirring was continued for 16 h. After the reaction, the obtained sol was poured into an anhydrous ethanol solution for precipitation to obtain a fluorine-containing soluble PI binder material.

[0094] Dissolve the prepared PI adhesive material in NMP solution to prepare a solution with a PI content of 0.2 g / mL. Take appropriate amounts according to the weight ratio of active material (Si / C, reversible specific capacity 650 mAh / g): conductive agent (Super P): adhesive (PI) = 5:4:1 and place them in a 20 mL small glass bottle. Stir magnetically for 10 h to prepare the electrode slurry. Then, evenly coat the slurry on the carbon-coated copper foil with a 150-micron-thick scraper, and place it in a vacuum oven and heat at 120 °C for 10 h to obtain a dried electrode sheet. Subsequently, assemble the battery in a glove box and test the rate performance.

[0095] The rate performance is as shown in the Figure 1 appendix;

[0096] The peel strength performance of the prepared PI adhesive material is shown in Table 1.

[0097] In Comparative Example 4, PI material was prepared using PMDA and ODA

[0098] Weigh 10.0000 g of 4,4'-diaminodiphenyl ether (ODA) and an appropriate amount of NMP solvent and add them to a three-necked flask. Stir under nitrogen until completely dissolved. Subsequently, gradually add 10.9060 g of pyromellitic dianhydride (PMDA), and stir at room temperature for 24 h to obtain a polyamic acid solution with a solid content of 10%, which is directly used as an adhesive. Mix according to the weight ratio of active material (Si / C, reversible specific capacity 650 mAh / g): conductive agent (Super P): adhesive (PAA) = 5:4:1. After the slurry is mixed evenly, coat it on the copper foil, and then heat it in a vacuum oven at 120 °C for 10 h, 150 °C for 1 h, 200 °C for 1 h, 250 °C for 1 h, and finally heat it at 350 °C for 10 min. The subsequent steps of preparing the electrode sheet and assembling the battery are the same.

[0099] The rate performance is as shown in the Figure 1 appendix;

[0100] The peel strength performance of the prepared PI adhesive material is shown in Table 1.

[0101] Table 1: Composition of PI Adhesive Material and Peel Strength Performance of Electrode Sheet

[0102]

[0103] As can be seen from the data in Table 1, compared with Comparative Examples 1 and 2, Examples 1, 2, 3, and 4 using the fluorine-containing soluble polyimide adhesive of the present invention as the adhesive material have higher bonding strength. This may be due to the polarity of the -(R)NR’-C(O)-R’N(R)- structure, which brings about a greater adhesive force. At the same time, it can be seen that Examples 1, 2, 3, 4, 5, and 6 have the advantage of being soluble compared with Comparative Example 4, which is more convenient for industrial application. From Figure 1 the data, it can be seen that the rate performance of the silicon anode lithium-ion battery using the fluorine-containing soluble polyimide of the present invention as the adhesive is better.

[0104] Thus, it can be seen that the fluorine-containing soluble polyimide adhesive material proposed by the present invention has excellent rate performance in silicon anode lithium-ion batteries, is simple to operate, and produces no by-products. This implementation has good industrial prospects.

[0105] Finally, the method of the present invention is only a preferred implementation, and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fluorine-containing soluble polyimide adhesive specifically for lithium-ion batteries, characterized in that: The fluorine-containing soluble polyimide adhesive is prepared by reacting dianhydride and diamine; the structure of the fluorine-containing soluble polyimide adhesive is as follows: in, -R'-for-C m H 2m -, m are each independently selected from 0, 1 or 2; -R is each independently selected from -H, -CH3 or -COO(CH3)3; n is a positive integer.

2. The fluorine-containing soluble polyimide adhesive according to claim 1, characterized in that: The fluorine-containing soluble polyimide adhesive is selected from any one of 6FDA-BAEPU, 6FCDA-BAEPU, 6FDA-BAEPU-BOC, 6FCDA-BAEPU-BOC, 6FDA-DMAPU, and 6FCDA-DMAPU; The structural formula of the 6FDA-BAEPU is: The structural formula of the 6FCDA-BAEPU is: The structural formula of the 6FDA-BAEPU-BOC is: The structural formula of the 6FCDA-BAEPU-BOC is: The structural formula of the 6FDA-DMAPU is: The structural formula of the 6FCDA-DMAPU is:

3. The fluorine-containing soluble polyimide adhesive according to claim 2, characterized in that: The dianhydride is selected from any one of 6FDA and 6FCDA; the diamine is selected from any one of BAEPU, BAEPU-BOC and DMAPU.

4. The method for preparing the fluorine-containing soluble polyimide adhesive according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) mixing dianhydride, diamine and aprotic polar solvent to undergo polycondensation reaction; (2) After the polycondensation reaction is completed, a catalyst and a dehydrating agent are added to react to obtain a fluorine-containing soluble polyimide adhesive.

5. The preparation method according to claim 4, characterized in that: The aprotic polar solvent in step (1) is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone and N,N-dimethylacetamide.

6. The preparation method according to claim 4, characterized in that: The catalyst in step (2) is selected from at least one of pyridine, isoquinoline and picoline.

7. The preparation method according to claim 4, characterized in that: The dehydrating agent in step (2) is acetic anhydride.

8. Use of the fluorine-containing soluble polyimide adhesive according to any one of claims 1 to 3 or the fluorine-containing soluble polyimide adhesive prepared by the preparation method according to any one of claims 4 to 7 in lithium-ion batteries.

9. The use according to claim 8, characterized in that: The lithium-ion battery is a silicon-carbon negative electrode lithium-ion battery.

10. The use according to claim 8, characterized in that: The lithium ion battery is a silicon negative electrode lithium ion battery.

Images