Pole piece slurry for positive electrode of lithium ion battery and preparation method of pole piece slurry

Abstract

The invention discloses pole piece slurry for a positive electrode of a lithium ion battery and a preparation method of the pole piece slurry, the pole piece slurry comprises the following raw materials in parts by weight: 90-95 parts of lithium iron phosphate, 2-5 parts of a modified binder, 0.5-1 part of carbon black, 1-1.5 parts of carbon nanotubes and 3-5 parts of deionized water, and the pole piece slurry uses the deionized water to replace an organic solvent. A toxic organic solvent needed by a traditional oily binder is avoided, pollution to the environment is reduced, the modified binder is prepared from a modified cross-linking agent containing disulfide bonds and a pretreatment binder containing furan groups, then a dynamic cross-linked structure is formed, in the charging and discharging process, the positive electrode material is subjected to volume expansion, and therefore the positive electrode material can be charged and discharged, and the service life of the positive electrode material is prolonged. The dynamic crosslinking of the adhesive can buffer stress, ensure the integrity of a pole piece and avoid the falling of active substances, and the molecular chain contains an organic silicon chain segment, so that the high-temperature-resistant effect of the modified adhesive can be improved, the degradation of the modified adhesive at high temperature is inhibited, and the service life of the battery is further prolonged.

Description

Technical Field

[0001] This invention relates to the field of cathode slurry preparation technology, specifically to a cathode slurry for lithium-ion batteries and its preparation method. Background Technology

[0002] Lithium-ion batteries are widely used in modern electronic devices such as mobile phones, laptops, and electric vehicles due to their high energy density and good cycle performance. Designing a suitable positive electrode is a key step in improving battery performance. As an important component of the positive electrode material, electrode slurry effectively improves electronic conductivity and reduces interfacial resistance, thereby enhancing the battery's charge-discharge efficiency and cycle performance. Traditional electrode slurries use conventional oil-based binders, which require toxic organic solvents, posing significant risks to human health and environmental safety. In contrast, aqueous binders emit no VOCs, pose no risk of combustion or explosion, and some can provide additional lithium-ion transport channels, reduce interfacial impedance, and exhibit high slurry dispersion uniformity, enabling high-speed coating. However, they have poor toughness, leading to a significant decrease in battery capacity after multiple charge-discharge cycles. Summary of the Invention

[0003] The purpose of this invention is to provide an electrode slurry for lithium-ion battery cathodes and its preparation method, which solves the problem that the aqueous binder in the current electrode slurry breaks down after multiple charge and discharge cycles, affecting the battery's lifespan.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing electrode slurry for lithium-ion battery positive electrode, specifically including the following steps:

[0006] Step A1: Mix polyvinyl alcohol, sodium persulfate, sodium sulfite, and deionized water evenly. Stir and add acrylic acid at a speed of 120-150 r / min and a temperature of 65-70℃ for 2-3 hours to obtain modified polyvinyl alcohol. Mix modified polyvinyl alcohol, 4-dimethylaminopyridine, and tetrahydrofuran evenly. Purge with nitrogen for protection. Stir and add furanoyl chloride at a speed of 150-200 r / min and a temperature of -5-0℃ for 1-1.5 hours. Then raise the temperature to 20-25℃ and react for 3-5 hours to obtain pretreated adhesive.

[0007] Step A2: Mix the pretreated binder, modified crosslinking agent, zinc chloride and tetrahydrofuran evenly, purge with nitrogen, and react for 15-18 hours at a rotation speed of 200-300 r / min and a temperature of 20-25℃ to obtain the modified binder. Weigh the following raw materials in parts by weight: 90-95 parts of lithium iron phosphate, 2-5 parts of modified binder, 0.5-1 parts of carbon black, 1-1.5 parts of carbon nanotubes and 3-5 parts of deionized water. Mix the raw materials evenly to obtain the electrode slurry for the positive electrode of lithium-ion batteries.

[0008] Further, in step A1, the mass ratio of polyvinyl alcohol, sodium persulfate, sodium sulfite, and acrylic acid is 2.75:0.03:0.1:2.75, the Mw of polyvinyl alcohol is 70000 g / mol, the mass ratio of modified polyvinyl alcohol to furoyl chloride is 5:1, and the amount of 4-dimethylaminopyridine is 6% of the mass of furoyl chloride.

[0009] Furthermore, the mass ratio of the pretreated binder to the modified crosslinking agent described in step A2 is 100:2-5, and the amount of zinc chloride used is 3% of the mass of the modified crosslinking agent.

[0010] Furthermore, the modified crosslinking agent is prepared by the following steps:

[0011] Step B1: Bis(4-hydroxyphenyl)disulfide, acryloyl chloride, triethylamine and tetrahydrofuran are mixed and reacted at 200-300 r / min and 30-40℃ for 2-3 h to obtain an intermediate. The intermediate, dimethylchlorosilane, chloroplatinic acid and DMF are mixed evenly and under nitrogen protection. The mixture is then reacted at 150-200 r / min and 70-80℃ for 6-8 h to obtain the modified monomer.

[0012] Step B2: Mix octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride evenly, purge with nitrogen for protection, and react for 10-12 hours at a rotation speed of 120-150 r / min and a temperature of 90-95°C. Then raise the temperature to 105-110°C and continue the reaction for 2-3 hours to obtain vinyl polysiloxane.

[0013] Step B3: Mix vinyl polysiloxane, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 6-8 hours at a speed of 150-200 r / min and a temperature of 70-80℃ to obtain pretreated polysiloxane. Mix lithium dimethylhydrosilyl alcohol and tetrahydrofuran evenly, stir and add octamethylcyclotetrasiloxane at a speed of 120-150 r / min and a temperature of 0℃, raise the temperature to 25-30℃ and react for 7-9 hours. Then add the pretreated polysiloxane and continue the reaction for 1-1.5 hours to obtain modified polysiloxane.

[0014] Step B4: Mix the modified polysiloxane, acryloyl chloride, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 6-8 hours at a speed of 150-200 r / min and a temperature of 75-85℃ to obtain the functionalized polysiloxane. Mix maleamide, triethylamine and tetrahydrofuran, stir and add the functionalized polysiloxane at a speed of 200-300 r / min and a temperature of 0℃, and react for 2-3 hours. Then raise the temperature to 20-25℃ and continue the reaction for 1-1.5 hours to obtain the modified crosslinking agent.

[0015] Furthermore, in step B1, the molar ratio of bis(4-hydroxyphenyl)disulfide, acryloyl chloride, and triethylamine is 1:2:2.1, the molar ratio of the intermediate to dimethylchlorosilane is 2:1, and the amount of chloroplatinic acid used is 1‰ of the mass of dimethylchlorosilane.

[0016] Furthermore, the ratio of octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and dimethyl sulfoxide in step B2 is 3.8 mol: 1 mol: 6 mol: 4 mol: 3 L: 10 L.

[0017] Furthermore, in step B3, the molar ratio of vinyl polysiloxane to trichlorosilane is 1:2, the amount of chloroplatinic acid is 1‰ of the mass of trichlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, octamethylcyclotetrasiloxane and the Si-Cl bond on the pretreated polysiloxane is 1:4:1.

[0018] Furthermore, in step B4, the molar ratio of Si-H bonds on the modified polysiloxane to acryloyl chloride is 1:1, the amount of chloroplatinic acid is 2‰ of the mass of acryloyl chloride, and the molar ratio of maleamide, triethylamine and acryl chloride on the functionalized polysiloxane is 1:1.2:1.

[0019] The beneficial effects of the present invention are as follows: The electrode slurry for the positive electrode of lithium-ion batteries prepared by the present invention includes the following raw materials: lithium iron phosphate, modified binder, carbon black, carbon nanotubes and deionized water. The modified binder is made of polyvinyl alcohol as raw material. Under the action of sodium persulfate and sodium sulfite, it is grafted onto the polyvinyl alcohol molecular chain through free radical polymerization reaction. Then, under the action of 4-dimethylaminopyridine, the acyl chloride on furanoyl chloride reacts with some alcohol hydroxyl groups on the polyvinyl alcohol molecule to obtain a pretreated binder. The pretreated binder is reacted with the modified crosslinking agent DA to obtain the modified binder.

[0020] The modified adhesive uses bis(4-hydroxyphenyl)disulfide and acryloyl chloride as raw materials. The hydroxyl groups on bis(4-hydroxyphenyl)disulfide react with the acryloyl chloride to obtain an intermediate. The intermediate is then reacted with dimethylchlorosilane, causing the double bonds on the intermediate to react with the Si-H bonds on the dimethylchlorosilane, yielding a modified monomer. Octamethylcyclotetrasiloxane is ring-opened, then hydrolyzed and condensed with the modified monomer, and finally capped with tetramethyldivinyldisiloxane to obtain a vinyl polysiloxane. The vinyl polysiloxane is then reacted with trichlorosilane, causing the double bonds on the vinyl polysiloxane to react with the trichlorosilane... Pretreated polysiloxanes are prepared by reacting the Si-H bonds on silanes. Dimethylhydrosilyllithium is used as an initiator, octamethylcyclotetrasiloxane as a polymerization monomer, and polysiloxane is added to react the Si-Cl bonds on the polysiloxane with the lithium silyllithium to obtain modified polysiloxanes. The modified polysiloxanes are then reacted with acryloyl chloride, causing the Si-H bonds on the modified polysiloxanes to react with the double bonds on the acryloyl chloride to obtain functionalized polysiloxanes. Finally, the functionalized polysiloxanes are reacted with maleimide, causing the acyl chloride on the functionalized polysiloxanes to react with the imide on the maleimide to obtain a modified crosslinking agent.

[0021] This electrode slurry uses deionized water instead of organic solvents, avoiding the toxic organic solvents required by traditional oil-based binders and reducing environmental pollution. Furthermore, the modified binder is made from a crosslinking agent containing disulfide bonds and a pretreated binder containing furan groups, forming a dynamic crosslinking structure. During charging and discharging, the positive electrode material undergoes volume expansion, and the dynamic crosslinking of the binder buffers stress, ensuring the integrity of the electrode and preventing the shedding of active material. The presence of organosilicon segments in the molecular chain increases the high-temperature resistance of the modified binder, inhibits its degradation at high temperatures, alleviates electrolyte side reactions, and thus increases battery life. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1: A method for preparing electrode slurry for lithium-ion battery positive electrode, specifically including the following steps:

[0024] Step A1: Polyvinyl alcohol, sodium persulfate, sodium sulfite, and deionized water are mixed evenly. Under the conditions of 120 r / min and 65℃, acrylic acid is added and the mixture is stirred and reacted for 2 h to obtain modified polyvinyl alcohol. Modified polyvinyl alcohol, 4-dimethylaminopyridine, and tetrahydrofuran are mixed evenly and protected with nitrogen gas. Under the conditions of 150 r / min and -5℃, furanoyl chloride is added and the mixture is stirred and reacted for 1 h. Then, the temperature is raised to 20℃ and the mixture is reacted for 3 h to obtain the pretreated adhesive.

[0025] Step A2: Mix the pretreated binder, modified crosslinking agent, zinc chloride and tetrahydrofuran evenly, purge with nitrogen, and react for 15 hours at a speed of 200 r / min and a temperature of 20℃ to obtain the modified binder. Weigh the following raw materials in parts by weight: 90 parts lithium iron phosphate, 2 parts modified binder, 0.5 parts carbon black, 1 part carbon nanotubes and 3 parts deionized water. Mix the raw materials evenly to obtain the electrode slurry for the positive electrode of lithium-ion batteries.

[0026] The mass ratio of polyvinyl alcohol, sodium persulfate, sodium sulfite and acrylic acid in step A1 is 2.75:0.03:0.1:2.75, the Mw of polyvinyl alcohol is 70000 g / mol, the mass ratio of modified polyvinyl alcohol and furoyl chloride is 5:1, and the amount of 4-dimethylaminopyridine is 6% of the mass of furoyl chloride.

[0027] The mass ratio of the pretreated adhesive to the modified crosslinking agent in step A2 is 100:2, and the amount of zinc chloride used is 3% of the mass of the modified crosslinking agent.

[0028] The modified crosslinking agent is prepared by the following steps:

[0029] Step B1: Bis(4-hydroxyphenyl)disulfide, acryloyl chloride, triethylamine and tetrahydrofuran were mixed and reacted for 2 h at a speed of 200 r / min and a temperature of 30 °C to obtain an intermediate. The intermediate, dimethylchlorosilane, chloroplatinic acid and DMF were mixed evenly and then reacted under nitrogen protection at a speed of 150 r / min and a temperature of 70 °C for 6 h to obtain the modified monomer.

[0030] Step B2: Mix octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride evenly, purge with nitrogen, and react for 10 h at a speed of 120 r / min and a temperature of 90 °C. Then raise the temperature to 105 °C and continue the reaction for 2 h to obtain vinyl polysiloxane.

[0031] Step B3: Mix vinyl polysiloxane, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 6 hours at 150 r / min and 70°C to obtain pretreated polysiloxane. Mix lithium dimethylhydrosilyl alcohol and tetrahydrofuran evenly, stir and add octamethylcyclotetrasiloxane at 120 r / min and 0°C, raise the temperature to 25°C and react for 7 hours. Then add the pretreated polysiloxane and continue the reaction for 1 hour to obtain modified polysiloxane.

[0032] Step B4: Mix the modified polysiloxane, acryloyl chloride, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 6 hours at 150 r / min and 75°C to obtain the functionalized polysiloxane. Mix maleamide, triethylamine and tetrahydrofuran, stir and add the functionalized polysiloxane at 200 r / min and 0°C, react for 2 hours, then raise the temperature to 20°C and continue the reaction for 1 hour to obtain the modified crosslinking agent.

[0033] The molar ratio of bis(4-hydroxyphenyl) disulfide, acryloyl chloride and triethylamine in step B1 is 1:2:2.1, the molar ratio of intermediate and dimethylchlorosilane is 2:1, and the amount of chloroplatinic acid is 1‰ of the mass of dimethylchlorosilane.

[0034] The ratio of octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and dimethyl sulfoxide in step B2 is 3.8 mol: 1 mol: 6 mol: 4 mol: 3 L: 10 L.

[0035] In step B3, the molar ratio of vinyl polysiloxane to trichlorosilane is 1:2, the amount of chloroplatinic acid is 1‰ of the mass of trichlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, octamethylcyclotetrasiloxane and the Si-Cl bond on the pretreated polysiloxane is 1:4:1.

[0036] In step B4, the molar ratio of Si-H bonds on the modified polysiloxane to acryloyl chloride is 1:1, the amount of chloroplatinic acid is 2‰ of the mass of acryloyl chloride, and the molar ratio of maleamide, triethylamine and acryl chloride on the functionalized polysiloxane is 1:1.2:1.

[0037] Example 2: A method for preparing electrode slurry for lithium-ion battery positive electrode, specifically including the following steps:

[0038] Step A1: Polyvinyl alcohol, sodium persulfate, sodium sulfite, and deionized water are mixed evenly. Under the conditions of 120 r / min and 68℃, acrylic acid is added and the mixture is stirred for 3 h to obtain modified polyvinyl alcohol. Modified polyvinyl alcohol, 4-dimethylaminopyridine, and tetrahydrofuran are mixed evenly and nitrogen gas is introduced for protection. Under the conditions of 150 r / min and 0℃, furanoyl chloride is added and the mixture is stirred for 1.2 h. Then, the temperature is raised to 23℃ and the mixture is reacted for 4 h to obtain pretreated adhesive.

[0039] Step A2: Mix the pretreated binder, modified crosslinking agent, zinc chloride and tetrahydrofuran evenly, purge with nitrogen, and react for 16.5 h at a speed of 200 r / min and a temperature of 25℃ to obtain the modified binder. Weigh the following raw materials in parts by weight: 93 parts lithium iron phosphate, 3.5 parts modified binder, 0.8 parts carbon black, 1.2 parts carbon nanotubes and 4 parts deionized water. Mix the raw materials evenly to obtain the electrode slurry for the positive electrode of lithium-ion batteries.

[0040] The mass ratio of polyvinyl alcohol, sodium persulfate, sodium sulfite and acrylic acid in step A1 is 2.75:0.03:0.1:2.75, the Mw of polyvinyl alcohol is 70000 g / mol, the mass ratio of modified polyvinyl alcohol and furoyl chloride is 5:1, and the amount of 4-dimethylaminopyridine is 6% of the mass of furoyl chloride.

[0041] The mass ratio of the pretreated binder to the modified crosslinking agent described in step A2 is 100:3.5, and the amount of zinc chloride used is 3% of the mass of the modified crosslinking agent.

[0042] The modified crosslinking agent is prepared by the following steps:

[0043] Step B1: Bis(4-hydroxyphenyl)disulfide, acryloyl chloride, triethylamine and tetrahydrofuran were mixed and reacted at 200 r / min and 35 °C for 3 h to obtain an intermediate. The intermediate, dimethylchlorosilane, chloroplatinic acid and DMF were mixed evenly and then reacted under nitrogen protection at 150 r / min and 75 °C for 7 h to obtain the modified monomer.

[0044] Step B2: Octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted at a speed of 120 r / min and a temperature of 95°C for 11 h. Then the temperature is raised to 110°C and the reaction is continued for 2.5 h to obtain vinyl polysiloxane.

[0045] Step B3: Mix vinyl polysiloxane, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 7 hours at 150 r / min and 75°C to obtain pretreated polysiloxane. Mix lithium dimethylhydrosilyl alcohol and tetrahydrofuran evenly, stir and add octamethylcyclotetrasiloxane at 120 r / min and 0°C, raise the temperature to 30°C and react for 8 hours. Then add the pretreated polysiloxane and continue the reaction for 1.3 hours to obtain modified polysiloxane.

[0046] Step B4: Mix the modified polysiloxane, acryloyl chloride, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 7 hours at 150 r / min and 80°C to obtain the functionalized polysiloxane. Mix maleamide, triethylamine and tetrahydrofuran, stir and add the functionalized polysiloxane at 200 r / min and 0°C, react for 3 hours, then raise the temperature to 23°C and continue the reaction for 1.5 hours to obtain the modified crosslinking agent.

[0047] The molar ratio of bis(4-hydroxyphenyl) disulfide, acryloyl chloride and triethylamine in step B1 is 1:2:2.1, the molar ratio of intermediate and dimethylchlorosilane is 2:1, and the amount of chloroplatinic acid is 1‰ of the mass of dimethylchlorosilane.

[0048] The ratio of octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and dimethyl sulfoxide in step B2 is 3.8 mol: 1 mol: 6 mol: 4 mol: 3 L: 10 L.

[0049] In step B3, the molar ratio of vinyl polysiloxane to trichlorosilane is 1:2, the amount of chloroplatinic acid is 1‰ of the mass of trichlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, octamethylcyclotetrasiloxane and the Si-Cl bond on the pretreated polysiloxane is 1:4:1.

[0050] In step B4, the molar ratio of Si-H bonds on the modified polysiloxane to acryloyl chloride is 1:1, the amount of chloroplatinic acid is 2‰ of the mass of acryloyl chloride, and the molar ratio of maleamide, triethylamine and acryl chloride on the functionalized polysiloxane is 1:1.2:1.

[0051] Example 3: A method for preparing electrode slurry for lithium-ion battery positive electrode, specifically including the following steps:

[0052] Step A1: Polyvinyl alcohol, sodium persulfate, sodium sulfite, and deionized water are mixed evenly. Under conditions of 150 r / min and 70°C, acrylic acid is added and the mixture is stirred for 3 h to obtain modified polyvinyl alcohol. Modified polyvinyl alcohol, 4-dimethylaminopyridine, and tetrahydrofuran are mixed evenly and protected with nitrogen gas. Under conditions of 200 r / min and 0°C, furanoyl chloride is added and the mixture is stirred for 1.5 h. Then, the temperature is raised to 25°C and the mixture is reacted for 5 h to obtain the pretreated adhesive.

[0053] Step A2: Mix the pretreated binder, modified crosslinking agent, zinc chloride and tetrahydrofuran evenly, purge with nitrogen, and react for 18 hours at a speed of 300 r / min and a temperature of 25℃ to obtain the modified binder. Weigh the following raw materials in parts by weight: 95 parts lithium iron phosphate, 5 parts modified binder, 1 part carbon black, 1.5 parts carbon nanotubes and 5 parts deionized water. Mix the raw materials evenly to obtain the electrode slurry for the positive electrode of lithium-ion batteries.

[0054] The mass ratio of polyvinyl alcohol, sodium persulfate, sodium sulfite and acrylic acid in step A1 is 2.75:0.03:0.1:2.75, the Mw of polyvinyl alcohol is 70000 g / mol, the mass ratio of modified polyvinyl alcohol and furoyl chloride is 5:1, and the amount of 4-dimethylaminopyridine is 6% of the mass of furoyl chloride.

[0055] The mass ratio of the pretreated adhesive to the modified crosslinking agent in step A2 is 100:5, and the amount of zinc chloride used is 3% of the mass of the modified crosslinking agent.

[0056] The modified crosslinking agent is prepared by the following steps:

[0057] Step B1: Bis(4-hydroxyphenyl)disulfide, acryloyl chloride, triethylamine and tetrahydrofuran were mixed and reacted at 300 r / min and 40 °C for 3 h to obtain an intermediate. The intermediate, dimethylchlorosilane, chloroplatinic acid and DMF were mixed evenly and then reacted under nitrogen protection at 200 r / min and 80 °C for 8 h to obtain the modified monomer.

[0058] Step B2: Mix octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride evenly, purge with nitrogen, and react for 12 hours at a speed of 150 r / min and a temperature of 95°C. Then raise the temperature to 110°C and continue the reaction for 3 hours to obtain vinyl polysiloxane.

[0059] Step B3: Mix vinyl polysiloxane, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 8 hours at 200 r / min and 80°C to obtain pretreated polysiloxane. Mix lithium dimethylhydrosilyl alcohol and tetrahydrofuran evenly, stir and add octamethylcyclotetrasiloxane at 150 r / min and 0°C, raise the temperature to 30°C and react for 9 hours. Then add the pretreated polysiloxane and continue the reaction for 1.5 hours to obtain modified polysiloxane.

[0060] Step B4: Mix the modified polysiloxane, acryloyl chloride, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 8 hours at 200 r / min and 85°C to obtain the functionalized polysiloxane. Mix maleamide, triethylamine and tetrahydrofuran, stir and add the functionalized polysiloxane at 300 r / min and 0°C, react for 3 hours, then raise the temperature to 25°C and continue the reaction for 1.5 hours to obtain the modified crosslinking agent.

[0061] The molar ratio of bis(4-hydroxyphenyl) disulfide, acryloyl chloride and triethylamine in step B1 is 1:2:2.1, the molar ratio of intermediate and dimethylchlorosilane is 2:1, and the amount of chloroplatinic acid is 1‰ of the mass of dimethylchlorosilane.

[0062] The ratio of octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and dimethyl sulfoxide in step B2 is 3.8 mol: 1 mol: 6 mol: 4 mol: 3 L: 10 L.

[0063] In step B3, the molar ratio of vinyl polysiloxane to trichlorosilane is 1:2, the amount of chloroplatinic acid is 1‰ of the mass of trichlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, octamethylcyclotetrasiloxane and the Si-CI bond on the pretreated polysiloxane is 1:4:1.

[0064] In step B4, the molar ratio of Si-H bonds on the modified polysiloxane to acryloyl chloride is 1:1, the amount of chloroplatinic acid is 2‰ of the mass of acryloyl chloride, and the molar ratio of maleamide, triethylamine and acryl chloride on the functionalized polysiloxane is 1:1.2:1.

[0065] Comparative Example 1: Compared with Example 1, this comparative example uses N,N′-(1,4-phenylene)bismaleimide instead of the modified crosslinking agent, and the other steps are the same.

[0066] Comparative Example 2: This comparative example did not include any modified monomers compared to Example 1, but the remaining steps were the same.

[0067] Comparative Example 3: Compared with Example 1, this comparative example mixed octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldisiloxane, deionized water and thionyl chloride evenly, purged with nitrogen, and reacted at 120 r / min and 90°C for 10 h. Then the temperature was raised to 105°C and the reaction was continued for 2 h. The product obtained replaced the modified polysiloxane, and the remaining steps were the same.

[0068] The electrode slurries obtained in Examples 1-3 and Comparative Examples 1-3 were coated on aluminum foil, dried, and sliced ​​to obtain positive electrode sheets. They were then assembled into button batteries using an LIR2032 button battery case and subjected to charge-discharge cycle tests at a 5C rate. The test voltage range was 2.4-4.2V, and the number of cycles was 600. The battery capacity retention rate was recorded, and the test results are shown in Table 1 below.

[0069] Table 1

[0070]

[0071]

[0072] As shown in the table above, this application can still maintain high capacity after multiple cycles.

[0073] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing electrode slurry for lithium-ion battery positive electrode, characterized in that: Specifically, the steps include the following: Step A1: Mix polyvinyl alcohol, sodium persulfate, sodium sulfite and deionized water, stir and add acrylic acid to react and obtain modified polyvinyl alcohol. Mix modified polyvinyl alcohol, 4-dimethylaminopyridine and tetrahydrofuran evenly, purge with nitrogen, stir and add furanyl chloride to react and obtain pretreated adhesive. Step A2: Mix the pretreated binder, modified crosslinking agent, zinc chloride and tetrahydrofuran evenly, purge with nitrogen gas for protection, and react to obtain the modified binder. Weigh the following raw materials in parts by weight: 90-95 parts lithium iron phosphate, 2-5 parts modified binder, 0.5-1 parts carbon black, 1-1.5 parts carbon nanotubes and 3-5 parts deionized water. Mix the raw materials evenly to obtain the electrode slurry for the positive electrode of lithium-ion batteries.

2. The method for preparing the electrode slurry for the positive electrode of a lithium-ion battery according to claim 1, characterized in that: The mass ratio of polyvinyl alcohol, sodium persulfate, sodium sulfite and acrylic acid in step A1 is 2.75:0.03:0.1:2.75, and the mass ratio of modified polyvinyl alcohol and furanoyl chloride is 5:

1.

3. The method for preparing the electrode slurry for the positive electrode of a lithium-ion battery according to claim 1, characterized in that: The mass ratio of the pretreated adhesive to the modified crosslinking agent described in step A2 is 100:2-5.

4. The method for preparing the electrode slurry for the positive electrode of a lithium-ion battery according to claim 1, characterized in that: The modified crosslinking agent is prepared by the following steps: Step B1: Bis(4-hydroxyphenyl)disulfide, acryloyl chloride, triethylamine and tetrahydrofuran are mixed and reacted to obtain an intermediate. The intermediate, dimethylchlorosilane, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection to carry out the reaction to obtain the modified monomer. Step B2: Mix octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride evenly, purge with nitrogen gas, and react to obtain vinyl polysiloxane. Step B3: Mix vinyl polysiloxane, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen, and react to obtain pretreated polysiloxane. Mix and stir dimethylhydrosilyl alcohol lithium and tetrahydrofuran, add octamethylcyclotetrasiloxane, react, add pretreated polysiloxane, and continue the reaction to obtain modified polysiloxane. Step B4: Mix the modified polysiloxane, acryloyl chloride, chloroplatinic acid and DMF evenly, purge with nitrogen for protection, and react to obtain the functionalized polysiloxane. Mix maleamide, triethylamine and tetrahydrofuran, stir and add the functionalized polysiloxane, and react to obtain the modified crosslinking agent.

5. The method for preparing the electrode slurry for the positive electrode of a lithium-ion battery according to claim 4, characterized in that: The molar ratio of bis(4-hydroxyphenyl)disulfide, acryloyl chloride and triethylamine in step B1 is 1:2:2.1, and the molar ratio of the intermediate and dimethylchlorosilane is 2:

1.

6. The method for preparing the electrode slurry for the positive electrode of a lithium-ion battery according to claim 4, characterized in that: The ratio of octamethylcyclotetrasiloxane, modified monomer, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and dimethyl sulfoxide in step B2 is 3.8 mol: 1 mol: 6 mol: 4 mol: 3 L: 10 L.

7. The method for preparing the electrode slurry for the positive electrode of a lithium-ion battery according to claim 4, characterized in that: The molar ratio of vinyl polysiloxane and trichlorosilane in step B3 is 1:2, and the molar ratio of lithium dimethylhydrosiloxane, octamethylcyclotetrasiloxane and Si-Cl bonds on the pretreated polysiloxane is 1:4:

1.

8. The method for preparing the electrode slurry for the positive electrode of a lithium-ion battery according to claim 4, characterized in that: In step B4, the molar ratio of Si-H bonds on the modified polysiloxane to acryloyl chloride is 1:1, and the molar ratio of maleamide, triethylamine, and acryloyl chloride on the functionalized polysiloxane is 1:1.2:

1.

9. A slurry for a positive electrode of a lithium-ion battery, characterized in that: Prepared according to any one of the preparation methods described in claims 1-8.

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