CN113174044B - Modified polyimide binder and preparation method and application thereof - Google Patents

Abstract

The present invention relates to a kind of modified polyimide binder and its preparation method and application, the general structural formula of described modified polyimide binder is:

Among them, m:n=5:1～1:5; the degree of polymerization m+n is an integer of 100～5000; the structural formula of R1 contains a self-healing functional group, and the self-healing functional group is a disulfide bond containing a dynamic reversible covalent bond or polysulfide bond functional groups; the structural formulas of R2 and R3 have a conjugated structure, and the R2 and R3 respectively include any one of aromatic compounds, heterocyclic compounds, aromatic derivatives or heterocyclic derivatives.

Description

Modified polyimide binder and its preparation method and application

technical field

The invention relates to the field of material technology, in particular to a modified polyimide binder and its preparation method and application.

Background technique

Lithium-ion batteries have excellent characteristics such as high energy density, long cycle life, low self-discharge rate, and no memory effect. They gradually replace traditional lead-acid batteries and nickel-cadmium batteries, and are widely used in portable electronic devices. In order to further expand the commercial application of lithium-ion batteries, major challenges have been raised in terms of high-power output performance and safety performance. Among them, many electrochemical properties of lithium-ion batteries, such as stability and irreversible capacity loss, are closely related to the performance of the binder.

Since the theoretical capacity of the traditional graphite negative electrode is only 372mAh/g, the theoretical capacity of the silicon material can reach as much as ten times, but the volume expansion of the silicon material is poor, and it is easy to pulverize during the charging and discharging process, resulting in short battery life and poor performance stability. wait. In this case, researchers used silicon-carbon composite materials as the negative electrode material, and the performance of the battery has been improved. During the use of silicon-carbon composite materials, the binder is an important part of the positive and negative electrodes of lithium-ion batteries. It is a polymer that adheres the electrode active material layer to the current collector. Its main function is to make the The components in the electrode are closely bonded and stabilize the structure of the pole piece to alleviate the expansion and contraction of the pole piece during the charging and discharging process of the battery, reduce the resistance of the electrode, and play a very important role in improving battery performance.

Polyimide material has the characteristics of structural diversity, stable chemical structure, and excellent mechanical properties. As a binder in the negative electrode of lithium-ion batteries, it plays an important role in the development of lithium-ion batteries with high capacity, stable cycle performance and good safety performance. significance.

At present, the research on the application of polyimide binders in lithium batteries is relatively extensive, but most of the research starts from the good mechanical properties, thermal stability and adhesion of polyimides. There are few studies on ion mobility, electrical conductivity, and self-healing properties. The application of the existing polyimide binder is in the ability of the electrode to combine with lithium ions, ion transfer ability, electrochemical stability, thermal stability, solubility in organic solvents, the absorption capacity of the electrode to the electrolyte, the electrode There are still deficiencies in impedance and flexibility, and the overall performance needs to be improved.

Contents of the invention

The embodiment of the present invention provides a modified polyimide binder and its preparation method and application, which are used to improve the cycle stability and overcharge safety of lithium-ion batteries, and at the same time solve the problem of low conductivity of the polymer itself .

In the first aspect, the embodiment of the present invention provides a modified polyimide adhesive, the general structural formula is:

Wherein, m:n=5:1～1:5; the degree of polymerization m+n is an integer of 100～5000;

The structural formula of R1 contains a self-repairing functional group, and the self-repairing functional group is a functional group containing a disulfide bond or a polysulfide bond of a dynamic reversible covalent bond;

The structural formulas of R2 and R3 have a conjugated structure, and said R2 and R3 respectively include any one of aromatic compounds, heterocyclic compounds, aromatic derivatives or heterocyclic derivatives.

Preferably, the R1 is one or more of diaryl disulfide, dialkyl disulfide, biheterocyclic disulfide;

The R2 is one or more of benzene, naphthalene, perylene, anthracene, pyrrole, thiophene, and furan;

The R3 is one or more of benzoquinone, naphthalene, perylene, anthracene, imidazole, thiazole and oxazole.

R2具体为/>

R3具体为

Preferably, the R1 is specifically

R2 is specifically />

R3 is specifically

In a second aspect, embodiments of the present invention provide a method for preparing the modified polyimide binder described in the first aspect, the preparation method comprising:

Under nitrogen protection, dissolving the diamine monomer in an organic solvent, stirring and dissolving at room temperature to obtain a first solution;

adding the dianhydride monomer into the first solution, and continuing to stir and react at room temperature for 12-24 hours to obtain a polyamic acid solution;

Precipitating the polyamic acid solution in a poor solvent, washing, suction filtering, and drying to obtain a polyamic acid solid powder;

Dissolving polyamic acid solid powder in an appropriate amount of N-methylpyrrolidone solvent to obtain a polyamic acid binder;

The polyamic acid binder is transformed into a modified polyimide binder after pole piece coating, rolling and heat treatment.

Preferably, the organic solvent is one or a mixture of tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide;

The ratio of the organic solvent to the diamine monomer is set according to R1:R3=5:1～1:5 in the general structural formula of the finally obtained modified polyimide binder;

The amount of the substance of the dianhydride monomer and the diamine monomer is the same;

The structural general formula of described modified polyimide binder is:

m:n＝5:1～1:5；聚合度m+n为100～5000的整数。

m:n=5:1-1:5; the degree of polymerization m+n is an integer of 100-5000.

Preferably, the solid content of the polyamic acid solution is 8wt%-12wt%; the solid content of the polyamic acid binder is 1wt%-20wt%.

Preferably, the poor solvent includes one or more of deionized water, methanol, ethanol, isopropanol, ethylene glycol, 2-butanol, cyclopentanol, cyclohexanol or phenol.

Preferably, the drying temperature is not higher than 150°C.

In a third aspect, an embodiment of the present invention provides an electrode sheet, which is a positive electrode sheet or a negative electrode sheet, and includes the modified polyimide binder described in the first aspect above.

In a fourth aspect, an embodiment of the present invention provides a lithium battery, including the electrode sheet described in the third aspect above.

The modified polyimide adhesive provided by the embodiment of the present invention introduces self-healing functional groups into the polyimide structure, improves the flexibility of the polymer, and also combines the good mechanical stability, Thermal stability; and the self-healing effect is achieved by introducing reversible covalent bonds or hydrogen bonds with self-healing functional groups into the polyimide structure, which can resist the expansion of active materials during charging and discharging, ensuring the cycle stability of lithium-ion batteries and overcharge safety, while solving the problem of low conductivity of the polymer itself; taking advantage of the property that conjugated polymers are easily oxidized and reduced, the conjugated structure of aromatic imides makes the lowest unoccupied molecular orbital of polyimide (Lowest Unoccupied Molecular Orbital, LUMO) has a low energy level and is easy to perform n-type doping, so that ions can be embedded in the polymer to neutralize the charge on the main chain, making polyimide rapidly and reversibly change from an insulating state to a conductive state State, improve the electronic conductivity of the binder, reduce the impedance; and the binder itself can also provide a certain reversible capacity, which helps to improve the first Coulombic efficiency and cycle capacity of the battery.

Description of drawings

The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings and embodiments.

Fig. 1 is the flow chart of the preparation method of the modified polyimide binder of the embodiment of the present invention;

Fig. 2 is the proton nuclear magnetic resonance spectrum of the modified polyimide that the embodiment of the present invention 1 provides;

Fig. 3 is the proton nuclear magnetic resonance spectrum of the polyamic acid that the embodiment of the present invention 1 provides;

Figure 4 is a comparison of the 100-cycle cycle stability and capacity retention at 0.1C between the modified polyimide binder and the traditional polyacrylate binder provided by Example 1 of the present invention.

Detailed ways

The present invention will be further described below through the accompanying drawings and specific embodiments, but it should be understood that these embodiments are only used for more detailed description, and should not be construed as limiting the present invention in any form, that is, not intended To limit the protection scope of the present invention.

The invention provides a modified polyimide binder, which can be used as a binder for lithium-ion batteries, and can be used in positive electrodes or negative electrodes.

The general structural formula of the modified polyimide binder is:

Wherein, m:n=5:1～1:5; the degree of polymerization m+n is an integer of 100～5000;

The structural formula of R1 contains a self-healing functional group, and the self-healing functional group is a functional group containing a disulfide bond or a polysulfide bond with a dynamic reversible covalent bond; specifically, R1 is a diaryl disulfide, a dialkyl disulfide, a bihetero One or more of cyclic disulfides.

The structural formulas of R2 and R3 have a conjugated structure, and R2 and R3 respectively include any one of aromatic compounds, heterocyclic compounds, aromatic derivatives or heterocyclic derivatives. R2 can be specifically one or more of benzene, naphthalene, perylene, anthracene, pyrrole, thiophene, and furan; R3 can be specifically one or more of benzoquinone, naphthalene, perylene, anthracene, imidazole, thiazole, and oxazole kind.

R2具体为/>

R3具体为/>

In a preferred example, R1 is specifically

R2 is specifically />

R3 is specifically />

The above modified polyimide binder can be prepared by the following method, and the main steps are as shown in Figure 1, including:

Step 110, under the protection of nitrogen, dissolve the diamine monomer in an organic solvent, stir and dissolve at room temperature to obtain a first solution;

Specifically, the organic solvent is one or a mixture of tetrahydrofuran, N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide;

The ratio of the organic solvent to the diamine monomer is set according to R1:R3=5:1˜1:5 in the general structural formula of the finally obtained modified polyimide binder.

Step 120, adding the dianhydride monomer into the first solution, and continuing to stir and react at room temperature for 12-24 hours to obtain a polyamic acid solution;

Specifically, the amount of the added dianhydride monomer is the same as that of the diamine monomer.

The solid content of the polyamic acid solution is 8wt%-12wt%; more preferably 10wt%.

Step 130, precipitating the polyamic acid solution in a poor solvent, washing, suction filtering, and drying to obtain a polyamic acid solid powder;

Specifically, the poor solvent includes one or more of deionized water, methanol, ethanol, isopropanol, ethylene glycol, 2-butanol, cyclopentanol, cyclohexanol or phenol.

During the precipitation treatment, the volume of the poor solvent used is 5-10 times that of the organic solvent used in step 110 .

In the drying process, vacuum drying can be used specifically, and other drying methods can also be used, the purpose of which is to remove the solvent. The drying temperature should not be higher than 150°C, because if the temperature is too high, it will easily induce the imidization reaction and reduce the solubility of the product, so it is preferable to dry between 60°C and 80°C.

Step 140, dissolving polyamic acid solid powder in an appropriate amount of N-methylpyrrolidone solvent to obtain a polyamic acid binder;

Specifically, the solid content of the polyamic acid binder is 1wt%-20wt%. More preferably 5wt% - 15wt%.

In step 150, the polyamic acid binder is transformed into a modified polyimide binder after electrode sheet coating, rolling, and heat treatment.

Specifically, mix the electrode active material, the conductive agent and the polyamic acid binder obtained in step 140, add a solvent and stir evenly to obtain an electrode slurry, adjust the electrode slurry to a suitable viscosity, apply it on the current collector, and dry it to obtain Pole piece to be processed;

Put the electrode piece to be processed into a tube furnace after rolling and cutting, pass inert gas, and program the temperature to rise at 5°C/min. When the temperature reaches 100°C, 200°C, and 300°C, keep it at this temperature for 1 hour respectively. The polyamic acid is imidized into polyimide, and finally cooled to obtain an electrode sheet containing a polyimide binder.

Wherein, the electrode pole piece can be a positive pole piece or a negative pole piece;

When the modified polyimide binder is used for the positive electrode sheet, the positive electrode active material can specifically be lithium nickel cobalt manganate, lithium iron phosphate, lithium manganate, lithium cobaltate, lithium nickel cobalt aluminate, lithium-rich manganese base Cathode materials, etc.

When the modified polyimide binder is used for the negative electrode sheet, the negative electrode active material may specifically include one or more of nano-silicon, micro-silicon, silicon oxygen, and silicon-carbon materials.

The conductive agent used may specifically include: one or a combination of conductive carbon black, carbon fiber, conductive graphite, and carbon nanotubes.

In the electrode slurry, preferably, the weight ratio of the electrode active material, the conductive agent, and the modified polyimide binder is 8:1:1.

The above-prepared positive electrode sheet or negative electrode sheet can be applied to lithium ion batteries.

The modified polyimide adhesive provided by the embodiment of the present invention introduces self-healing functional groups into the polyimide structure, improves the flexibility of the polymer, and also combines the good mechanical stability, Thermal stability; and the self-healing effect is achieved by introducing reversible covalent bonds or hydrogen bonds with self-healing functional groups into the polyimide structure, which can resist the expansion of active materials during charging and discharging, ensuring the cycle stability of lithium-ion batteries and overcharge safety, while solving the problem of low conductivity of the polymer itself; taking advantage of the property that conjugated polymers are easily oxidized and reduced, the conjugated structure of aromatic imides makes the lowest unoccupied molecular orbital of polyimide (Lowest Unoccupied Molecular Orbital, LUMO) has a low energy level and is easy to perform n-type doping, so that ions can be embedded in the polymer to neutralize the charge on the main chain, making polyimide rapidly and reversibly change from an insulating state to a conductive state State, improve the electronic conductivity of the binder, reduce the impedance; and the binder itself can also provide a certain reversible capacity, which helps to improve the first Coulombic efficiency and cycle capacity of the battery.

For a better understanding of the technical solutions provided by the present invention, the specific process of preparing the modified polyimide binder by using the methods provided in the above-mentioned embodiments of the present invention and applying it to lithium Ion battery methods and battery characteristics.

Example 1

其中，m:n ＝4:1。This embodiment provides a lithium ion battery negative electrode binder, which is a modified polyimide polymer, and its structural formula is:

Wherein, m:n=4:1.

和2mmol的/>

二胺单体溶于40mlN-甲基吡咯烷酮中，持续通入氮气，在室温下搅拌使其充分溶解后加入10.02mmol二酐单体/>

室温下搅拌12小时，得到高分子溶液。反应完成后将 300ml去离子水加入到高分子溶液中搅拌沉淀，将得到的沉淀物经洗涤、抽滤后，在60℃下真空干燥12小时，得到纤维状白色及浅黄色的聚酰胺酸固体粉末，结构式为/>

The preparation method of the modified polyimide binder of the present embodiment is: with 8mmol

and 2 mmol of

Dissolve the diamine monomer in 40ml N-methylpyrrolidone, continue to feed nitrogen, stir at room temperature to fully dissolve it, then add 10.02mmol dianhydride monomer/>

Stir at room temperature for 12 hours to obtain a polymer solution. After the reaction is completed, add 300ml of deionized water into the polymer solution to stir and precipitate. After washing and suction filtering, the obtained precipitate is vacuum-dried at 60°C for 12 hours to obtain a fibrous white and light yellow polyamic acid solid Powder, structural formula is />

The above polyamic acid solid powder was dissolved in N-methylpyrrolidone, fully stirred at 15° C. to dissolve it completely, and a 10 wt % polyamic acid binder solution was obtained.

The composition of the negative electrode material is in accordance with the ZT-SC-600 silicon carbon negative electrode material: conductive carbon black: polyamic acid binder with a mass ratio of 80:10:10, mixed with high-speed shearing, adding N-methylpyrrolidone A slurry with a viscosity of 10000 mPa·s was adjusted to obtain the slurry, and the slurry was evenly scraped on the copper foil with a thickness of 100 μm, and dried in an oven at 80° C. to obtain a negative electrode sheet to be treated.

Finally, roll the negative electrode sheet to be processed under a pressure of 20 MPa, cut off the excess copper foil, put it into a tube furnace, pass in an inert gas, and program the temperature at 5°C/min. The temperature was kept under the temperature of 1 hour respectively, so that the polyamic acid was imidized into polyimide, and finally cooled to obtain a negative electrode sheet containing a polyimide binder.

During this process, the polyamic acid solid powder in the above process and the polyimide contained in the final negative pole piece were tested for hydrogen nuclear magnetic resonance. The results are shown in Figure 2 and Figure 3, respectively, and verified by hydrogen nuclear magnetic resonance Can ensure the successful synthesis of polyimide binder.

For comparison, a traditional polyacrylate binder was used to prepare a negative electrode sheet for comparison by a preparation process. The composition of the negative electrode slurry in this comparative example is: the mass ratio of ZT-SC-600 silicon carbon negative electrode material: conductive carbon black: polyacrylate is 80:10:10, and the solvent is water. After stirring the above slurry evenly, apply it on the copper foil with a scraper with a thickness of 100 μm, place it in an oven at 80°C for 2 hours, then quickly dry it at 120°C for 1 hour, and finally dry it at 110°C After vacuum drying for 1.5 hours and rolling, a negative electrode sheet for comparison was obtained.

The above prepared negative electrode sheet containing polyimide binder was compared with the negative electrode sheet for comparison prepared by traditional polyacrylate binder. The results are shown in Table 1.

binder Peel strength (kN/m) Peel force (N) polyimide adhesive 0.0796 1.1954 Traditional polyacrylate binder 0.0175 0.2634

Table 1

It can be seen that the peel strength of the polyimide-containing adhesive provided by the present invention is much better than that of the traditional polyacrylate adhesive.

The four-probe method was used to test the negative electrode sheet containing polyimide binder and the negative electrode sheet for comparison, and the measured resistivity comparison is shown in Table 2.

Electrode binder Resistivity (mΩ*cm) polyimide adhesive 82.2 Traditional polyacrylate binder 348.1

Table 2

It can be seen that the use of the polyimide-containing binder provided by the present invention greatly improves the electronic conductivity and effectively reduces the impedance.

A button battery was made respectively with the negative electrode sheet containing the polyimide binder provided by the present invention and the negative electrode sheet containing the traditional polyacrylate binder for performance comparison. The Celgard2300 diaphragm is used, the metal is the lithium negative electrode, and 1MLiPF ₆ @1:1 ethylene carbonate (EC) + dimethyl carbonate (DMC) is the electrolyte. The test results shown in Figure 4 are obtained through testing. As can be seen from Fig. 4, the cycle stability and capacity retention rate of 100 cycles at 0.1C of the negative electrode sheet prepared by the polyimide binder of the present invention are significantly better than those prepared by the traditional polyacrylate binder. Negative pole piece.

Example 2

其中， m:n＝3:1。This embodiment provides a lithium ion battery negative electrode binder, which is a modified polyimide polymer, and its structural formula is:

Wherein, m:n=3:1.

和2.5mmol的/>

二胺单体溶于40mlN-甲基吡咯烷酮中，持续通入氮气，在室温下搅拌使其充分溶解后加入10.02mmol二酐单体/>

室温下搅拌12小时，得到高分子溶液。反应完成后将300ml去离子水加入到高分子溶液中搅拌沉淀，得到的沉淀物经洗涤、抽滤后，在60℃下真空干燥12小时，得到纤维状白色及浅黄色的聚酰胺酸聚合物固体粉末。The preparation method of the modified polyimide binder of the present embodiment is: the

and 2.5 mmol of

Dissolve the diamine monomer in 40ml N-methylpyrrolidone, continue to feed nitrogen, stir at room temperature to fully dissolve it, then add 10.02mmol dianhydride monomer/>

Stir at room temperature for 12 hours to obtain a polymer solution. After the reaction is completed, add 300ml of deionized water into the polymer solution to stir and precipitate. After washing and suction filtration, the obtained precipitate is vacuum-dried at 60°C for 12 hours to obtain a fibrous white and light yellow polyamic acid polymer. solid powder.

The preparation method of the negative electrode sheet and the battery assembly process are the same as those in Example 1.

The negative pole piece prepared by the polyimide binder of the present invention is cycled for 100 cycles at 0.1C, and the cycle capacity retention rate and first-week efficiency are significantly better than the negative pole piece prepared by the traditional polyacrylate binder. The comparison of the obtained data can be seen in Table 3.

Electrode binder cycle capacity retention first week efficiency polyimide adhesive 92.4% 94.5% Traditional polyacrylate binder 64.6% 86.5%

table 3

Example 3

其中， m:n＝3:2。This embodiment provides a lithium ion battery negative electrode binder, which is a modified polyimide polymer, and its structural formula is:

Wherein, m:n=3:2.

和4mmo l的/>

二胺单体溶于40mlN-甲基吡咯烷酮中，持续通入氮气，在室温下搅拌使其充分溶解后加入10.02mmol二酐单体/>

室温下搅拌12小时，得到高分子溶液。反应完成后将 300ml去离子水加入到高分子溶液中搅拌沉淀，得到的沉淀物经洗涤、抽滤后，在60℃下真空干燥12小时，得到纤维状白色及浅黄色的聚酰胺酸聚合物固体粉末。The preparation method of the modified polyimide binder of the present embodiment is: the

and 4mmol of />

Dissolve the diamine monomer in 40ml N-methylpyrrolidone, continue to feed nitrogen, stir at room temperature to fully dissolve it, then add 10.02mmol dianhydride monomer/>

Stir at room temperature for 12 hours to obtain a polymer solution. After the reaction is completed, add 300ml of deionized water into the polymer solution to stir and precipitate. After washing and suction filtration, the obtained precipitate is vacuum-dried at 60°C for 12 hours to obtain a fibrous white and light yellow polyamic acid polymer. solid powder.

The preparation method of the negative electrode sheet and the battery assembly process are the same as those in Example 1.

The negative pole piece prepared by the polyimide binder of the present invention is cycled for 100 cycles at 0.1C, and the cycle capacity retention rate and first-week efficiency are significantly better than the negative pole piece prepared by the traditional polyacrylate binder. The comparison of the obtained data can be seen in Table 4.

Electrode binder cycle capacity retention first week efficiency polyimide adhesive 90.6% 92.1% Traditional polyacrylate binder 64.6% 86.5%

Table 4

Example 4

其中m:n＝1:1。This embodiment provides a lithium ion battery negative electrode binder, which is a modified polyimide polymer,

where m:n=1:1.

和5mmol的/>

二胺单体溶于40mlN-甲基吡咯烷酮中，持续通入氮气，在室温下搅拌使其充分溶解后加入10.02mmol二酐单体/>

室温下搅拌12小时，得到高分子溶液。反应完成后将 300ml去离子水加入到高分子溶液中搅拌沉淀，得到的沉淀物经洗涤、抽滤后，在60℃下真空干燥12小时，得到纤维状白色及浅黄色的聚酰胺酸聚合物固体粉末。The preparation method of the modified polyimide binder of the present embodiment is: the

and 5 mmol of

Dissolve the diamine monomer in 40ml N-methylpyrrolidone, continue to feed nitrogen, stir at room temperature to fully dissolve it, then add 10.02mmol dianhydride monomer/>

Stir at room temperature for 12 hours to obtain a polymer solution. After the reaction is completed, add 300ml of deionized water into the polymer solution to stir and precipitate. After washing and suction filtration, the obtained precipitate is vacuum-dried at 60°C for 12 hours to obtain a fibrous white and light yellow polyamic acid polymer. solid powder.

The preparation method of the negative electrode sheet and the battery assembly process are the same as those in Example 1.

The negative pole piece prepared by the polyimide binder of the present invention is cycled for 100 cycles at 0.1C, and the cycle capacity retention rate and first-week efficiency are significantly better than the negative pole piece prepared by the traditional polyacrylate binder. The comparison of the obtained data can be seen in Table 5.

Electrode binder cycle capacity retention First week efficiency polyimide adhesive 95.8% 93.8% Traditional polyacrylate binder 64.6% 86.5%

table 5

Example 5

其中，m:n＝2:3。This embodiment provides a lithium ion battery negative electrode binder, which is a modified polyimide polymer,

Among them, m:n=2:3.

和6mmol的/>

二胺单体溶于40mlN-甲基吡咯烷酮中，持续通入氮气，在室温下搅拌使其充分溶解后加入10.02mmol二酐单体/>

室温下搅拌12小时，得到高分子溶液。反应完成后将 300ml去离子水加入到高分子溶液中搅拌沉淀，得到的沉淀物经洗涤、抽滤后，在60℃下真空干燥12小时，得到纤维状白色及浅黄色的聚酰胺酸聚合物固体粉末。The preparation method of the modified polyimide binder of the present embodiment is: with 4mmol

and 6 mmol of

Dissolve the diamine monomer in 40ml N-methylpyrrolidone, continue to feed nitrogen, stir at room temperature to fully dissolve it, then add 10.02mmol dianhydride monomer/>

Stir at room temperature for 12 hours to obtain a polymer solution. After the reaction is completed, add 300ml of deionized water into the polymer solution to stir and precipitate. After washing and suction filtration, the obtained precipitate is vacuum-dried at 60°C for 12 hours to obtain a fibrous white and light yellow polyamic acid polymer. solid powder.

The preparation method of the negative electrode sheet and the battery assembly process are the same as those in Example 1.

The negative pole piece prepared by the polyimide binder of the present invention is cycled for 100 cycles at 0.1C, and the cycle capacity retention rate and first-week efficiency are significantly better than the negative pole piece prepared by the traditional polyacrylate binder. The comparison of the obtained data can be seen in Table 6.

Electrode binder cycle capacity retention first week efficiency polyimide adhesive 96.1% 96.7% Traditional polyacrylate binder 64.6% 86.5%

Table 6

Example 6

其中，m:n＝1:3。This embodiment provides a lithium ion battery negative electrode binder, which is a modified polyimide polymer,

Among them, m:n=1:3.

和7.5mmol的/>

二胺单体溶于40mlN-甲基吡咯烷酮中，持续通入氮气，在室温下搅拌使其充分溶解后加入10.02mmol二酐单体/>

室温下搅拌12小时，得到高分子溶液。反应完成后将300ml去离子水加入到高分子溶液中搅拌沉淀，得到的沉淀物经洗涤、抽滤后，在60℃下真空干燥12小时，得到纤维状白色及浅黄色的聚酰胺酸聚合物固体粉末。The preparation method of the modified polyimide binder of the present embodiment is: the

and 7.5 mmol of

Dissolve the diamine monomer in 40ml N-methylpyrrolidone, continue to feed nitrogen, stir at room temperature to fully dissolve it, then add 10.02mmol dianhydride monomer/>

Stir at room temperature for 12 hours to obtain a polymer solution. After the reaction is completed, add 300ml of deionized water into the polymer solution to stir and precipitate. After washing and suction filtration, the obtained precipitate is vacuum-dried at 60°C for 12 hours to obtain a fibrous white and light yellow polyamic acid polymer. solid powder.

The preparation method of the negative electrode sheet and the battery assembly process are the same as those in Example 1.

The negative pole piece prepared by the polyimide binder of the present invention is cycled for 100 cycles at 0.1C, and the cycle capacity retention rate and first-week efficiency are significantly better than the negative pole piece prepared by the traditional polyacrylate binder. The comparison of the obtained data can be seen in Table 7.

Electrode binder cycle capacity retention first week efficiency polyimide adhesive 89.9% 98.2% Traditional polyacrylate binder 64.6% 86.5%

Table 7

Example 7

其中，m:n＝1:4。This embodiment provides a lithium ion battery negative electrode binder, which is a modified polyimide polymer,

Among them, m:n=1:4.

和8mmol的/>

二胺单体溶于40mLN-甲基吡咯烷酮中，持续通入氮气，在室温下搅拌使其充分溶解后加入10.02mmol二酐单体/>

室温下搅拌12小时，得到高分子溶液。反应完成后将 300ml去离子水加入到高分子溶液中搅拌沉淀，得到的沉淀物经洗涤、抽滤后，在60℃下真空干燥12小时，得到纤维状白色及浅黄色的聚酰胺酸聚合物固体粉末。The preparation method of the modified polyimide adhesive of the present embodiment is: the

and 8 mmol of

Dissolve the diamine monomer in 40mL N-methylpyrrolidone, continue to feed nitrogen, stir at room temperature to fully dissolve it, then add 10.02mmol dianhydride monomer/>

Stir at room temperature for 12 hours to obtain a polymer solution. After the reaction is completed, add 300ml of deionized water into the polymer solution to stir and precipitate. After washing and suction filtration, the obtained precipitate is vacuum-dried at 60°C for 12 hours to obtain a fibrous white and light yellow polyamic acid polymer. solid powder.

The preparation method of the negative electrode sheet and the battery assembly process are the same as those in Example 1.

The negative pole piece prepared by the polyimide binder of the present invention is cycled for 100 cycles at 0.1C, and the cycle capacity retention rate and first-week efficiency are significantly better than the negative pole piece prepared by the traditional polyacrylate binder. The comparison of the obtained data can be seen in Table 8.

Electrode binder cycle capacity retention first week efficiency polyimide adhesive 86.4% 95.4% Traditional polyacrylate binder 64.6% 86.5%

Table 8

The modified polyimide binder proposed by the present invention can be used in the positive electrode material system as well as the above negative electrode material system. Applicable positive electrode materials include nickel-cobalt lithium manganese oxide, lithium iron phosphate, lithium manganate, lithium cobalt oxide, nickel-cobalt lithium aluminate, lithium-rich manganese-based and other positive electrode materials.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (9)

1. a modified polyimide adhesive, is characterized in that, the general structural formula of described modified polyimide adhesive is:

Wherein, m:n=5:1～1:5; the degree of polymerization m+n is an integer of 100～5000; The structural formula of R1 contains a self-repairing functional group, and the self-repairing functional group is a functional group containing a disulfide bond or a polysulfide bond of a dynamic reversible covalent bond; The structural formulas of R2 and R3 have a conjugated structure, and the monomers before the reaction of R2 and R3 respectively include any one of aromatic compounds, heterocyclic compounds, aromatic derivatives or heterocyclic derivatives; The monomer before the R1 reaction is one or more of diaryl disulfide, dialkyl disulfide, and biheterocyclic disulfide; The monomer before the R1 reaction is specifically

The monomer before the R2 reaction is specifically />

The monomer before the R3 reaction is specifically />

2. modified polyimide binding agent according to claim 1, is characterized in that, the monomer before described R2 reaction is benzene, naphthalene, perylene, anthracene, pyrrole, thiophene, a kind of in furan or Several; The monomer before the R3 reaction is one or more of benzoquinone, naphthalene, perylene, anthracene, imidazole, thiazole, and oxazole. 3. a kind of preparation method of the arbitrary described modified polyimide binding agent of above-mentioned claim 1-2, is characterized in that, described preparation method comprises: Under nitrogen protection, dissolving the diamine monomer in an organic solvent, stirring and dissolving at room temperature to obtain a first solution; adding the dianhydride monomer into the first solution, and continuing to stir and react at room temperature for 12-24 hours to obtain a polyamic acid solution; Precipitating the polyamic acid solution in a poor solvent, washing, suction filtering, and drying to obtain a polyamic acid solid powder; Dissolving polyamic acid solid powder in an appropriate amount of N-methylpyrrolidone solvent to obtain a polyamic acid binder; The polyamic acid binder is transformed into a modified polyimide binder after pole piece coating, rolling and heat treatment. 4. preparation method according to claim 3 is characterized in that, described organic solvent is THF, N-methylpyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide One or any combination of several; The ratio of the organic solvent to the diamine monomer is set according to R1:R3=5:1～1:5 in the general structural formula of the finally obtained modified polyimide binder; The amount of the substance of the dianhydride monomer and the diamine monomer is the same; The structural general formula of described modified polyimide binder is:

m:n=5:1-1:5; the degree of polymerization m+n is an integer of 100-5000. 5. The preparation method according to claim 3, characterized in that, the solid content of the polyamic acid solution is 8wt%-12wt%; the solid content of the polyamic acid binder is 1wt%-20wt%. 6. preparation method according to claim 3, is characterized in that, described poor solvent comprises deionized water, methyl alcohol, ethanol, Virahol, ethylene glycol, 2-butanol, cyclopentanol, cyclohexanol or One or several kinds of phenols. 7. The preparation method according to claim 3, characterized in that, the drying temperature is not higher than 150°C. 8. An electrode sheet, characterized in that the electrode sheet is a positive electrode sheet or a negative electrode sheet, comprising the modified polyimide binder according to any one of claims 1-2. 9. A lithium ion battery, characterized in that the lithium ion battery comprises the electrode sheet according to claim 8.

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