Binder for insulating coating of lithium-ion battery and use thereof

Abstract

The present invention relates to the technical field of secondary battery binders and relates to a binder for an insulating coating of a lithium-ion battery and a use thereof. The technical problem solved by the present invention is to provide a binder for an insulating coating of a lithium-ion battery. The binder comprises an acrylate polymer. The structural formula of the acrylate polymer comprises unit I and unit II. An emulsion of the binder of the present invention is stable. A slurry system prepared therefrom has high surface tension, integrates the functions of dispersion, suspension, and binding, does not need the additional addition of auxiliaries such as a thickening agent and a dispersing agent, and can achieve high-speed stirring and dispersion of boehmite in one step, thereby achieving a simple and convenient process and a good dispersion effect, involving a relatively low glass transition temperature, achieving excellent flexibility and the hot-press bonding function of a separator, and avoiding the risk of breakage and powder shedding of the coating.

Description

Binder for lithium-ion battery insulation coating and its application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of and priority to Chinese patent application CN2024103045084, filed on March 18, 2024, and is incorporated herein by reference in its entirety for all other purposes. Technical Field

[0003] The invention relates to a binder for lithium ion battery insulating coating and application thereof, belonging to the technical field of secondary battery binders. Background Art

[0004] Lithium-ion batteries are widely used in communications, new energy vehicles and other fields due to their high energy density, high average output voltage, wide operating temperature range (-20℃~60℃), excellent cycle performance, fast charging and discharging, long service life, and absence of toxic and harmful substances.

[0005] To meet the demands of future electrification, lithium-ion batteries face significant challenges in improving their performance. Common lithium-ion batteries are assembled from a positive electrode, a negative electrode, a separator, and an electrolyte. The quality of the electrode directly impacts the performance of the battery. To achieve higher-performing lithium-ion batteries, using thicker electrode sheets is an effective approach. Other approaches include increasing the proportion of active material in the slurry and improving the compaction density of the electrode sheets to improve the capacity and energy density of lithium-ion batteries. Currently, safety risks and issues associated with the use of lithium batteries are becoming increasingly prominent, with the risk of smoke, fire, and even explosion. Therefore, their safety indicators are receiving significant international attention. Applying an insulating coating to the edges of the electrode sheets can improve battery safety.

[0006] Patent CN200910134934.3 discloses a lithium-ion battery and its preparation method, which applies an insulating coating to the edge of the electrode to improve the battery's high-temperature safety performance. However, the adhesive used has a melting point above 100°C, resulting in weak adhesion to metal foil and no thermal bonding effect on PE separators, which may affect the safety of the lithium battery.

[0007] Patent CN114573812B discloses a lithium ion binder and its preparation method, which includes a polyamide imide compound and discusses the peel strength to aluminum foil; however, a large amount of organic solvent is used in the synthesis, and the synthesis steps are relatively tedious and complicated, resulting in weak adhesion to the diaphragm.

[0008] Currently, the most commonly used edge-coating adhesive is an EAA emulsion adhesive, which has a high thermal adhesion to the separator but insufficient wet bonding strength to the copper foil, making it prone to detachment from the foil. The emulsion is unstable, exhibiting poor shear and freeze-thaw resistance, and is prone to demulsification during stirring to prepare the ceramic slurry. This requires the addition of thickeners such as CMC, which complicates the process and reduces thermal adhesion. Furthermore, the addition of large amounts of emulsifiers, which remain in the adhesive system, can significantly negatively impact the electrochemical performance of the electrode. Therefore, a better-performing edge-coating adhesive is needed. Summary of the Invention

[0009] In view of the above defects, the technical problem solved by the present invention is to provide a binder for lithium ion battery insulating coating.

[0010] The binder for the insulating coating of a lithium ion battery of the present invention comprises an acrylate polymer; the structural formula of the acrylate polymer comprises unit I and unit II, wherein:

[0011] The structure of unit I is shown in formula I:

[0012] R1 is selected from -OOCCH3, -COOCH2CH3, -COO(CH2)3CH3, -COOCH2CH(C2H5)C4H9, -COOC8H 17 、-COOC 12 H 25 、-COOC 18 H 37 , at least one of -CH2OOCCH3;

[0013] The structure of unit II is shown in formula II:

[0014] R2 is selected from at least one of -COOCH2CH2OH, -COOCH(CH3)CH2OH, -COOCH2CH2CH2CH2OH;

[0015] The mass ratio of unit I to unit II is 15-30:70-90.

[0016] In a specific embodiment of the present invention, the acrylate polymer further includes a unit III, and the structure of the unit III is shown in Formula III:

[0017] R3 is selected from at least one of -H and -CH3; R4 is selected from at least one of -COOH, -CONH2, and -CN.

[0018] In a specific embodiment of the present invention, the proportion of the third unit is less than 5% by weight of the acrylate polymer.

[0019] In one embodiment of the present invention, the first unit is introduced by the first monomer, the second unit is introduced by the second monomer, and the third unit is introduced by the third monomer;

[0020] Wherein, the first monomer includes at least one of ethyl acrylate, butyl acrylate, isooctyl acrylate, n-octyl acrylate, lauryl acrylate, octadecyl acrylate, vinyl acetate, and propylene acetate;

[0021] The second monomer includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate;

[0022] The third monomer includes at least one of acrylic acid and methacrylic acid.

[0023] In a specific embodiment of the present invention, the weight ratio of the first monomer: the second monomer: the third monomer is 10-30:70-90:0-5; preferably, the weight ratio of the first monomer: the second monomer: the third monomer is 15-30:70-80:0-5; more preferably, the weight ratio of the first monomer: the second monomer: the third monomer is 15-25:70-80:1-5.

[0024] In a specific embodiment of the present invention, monomer I, monomer II, and monomer III are polymerized in the presence of a protective colloid to obtain an acrylate polymer; the protective colloid includes at least one of cyclodextrin, polyvinyl pyrrolidone, polyvinyl alcohol, and hydroxymethyl cellulose.

[0025] In a specific embodiment of the present invention, the amount of the protective colloid is less than 10% of the weight of the polymerized monomers; preferably, the amount of the protective colloid is 1-5% of the weight of the polymerized monomers.

[0026] In a specific embodiment of the present invention, the binder for the lithium-ion battery insulating coating further comprises a solvent. In a preferred embodiment, the solvent is water.

[0027] In a specific embodiment of the present invention, based on 100 parts by weight of the binder for the insulating coating of lithium-ion batteries, the mass percentage of the acrylic ester polymer is 20-30%.

[0028] The present invention also provides the use of the adhesive for lithium ion battery insulation coating of the present invention in edge coating.

[0029] The adhesive for the insulating coating of a lithium ion battery of the present invention can be used as an edge coating adhesive and applied to the insulating coating of a lithium ion battery.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The adhesive of the present invention adopts a specific structural design, which embodies the scientific use of intermolecular forces. Different components have different functions. Unit II and Unit III can provide good adhesion to copper foil, and the groups of Unit I and Unit II (acrylate segments with low glass transition temperature) have excellent wetting and bonding effects on polyolefin separators.

[0032] (2) The binder of the present invention can adopt soap-free emulsion polymerization through the preferred unit ratio, which effectively avoids the influence of emulsifier on the electrical properties of the product, does not break the emulsion, and has good mechanical shear resistance; on the other hand, it avoids the instability of the binder system and the occurrence of stratification problems.

[0033] (3) The binder emulsion of the present invention is stable, and the slurry system prepared therefrom has a high surface tension (the surface tension of the slurry system can reach 55 to 70 mN / m), thereby improving the anti-penetration property with the negative electrode slurry and avoiding quality defects such as shadow formation or powder leakage.

[0034] (4) The binder of the present invention integrates dispersion, suspension and bonding, and does not require the addition of additional additives such as thickeners and dispersants. Boehmite can be dispersed by high-speed stirring in one step to prepare negative electrode slurry for lithium-ion battery insulating coating. The process is simple and convenient, and the dispersion effect is good.

[0035] (5) The adhesive of the present invention has a low glass transition temperature, T g : -40~20℃, with excellent flexibility and diaphragm hot pressing bonding function, and the coating has no risk of breakage or powdering. DETAILED DESCRIPTION

[0036] The binder for the insulating coating of a lithium ion battery of the present invention comprises an acrylate polymer; the structural formula of the acrylate polymer comprises unit I and unit II, wherein:

[0037] The structure of unit I is shown in formula I:

[0038] R1 is selected from -OOCCH3, -COOCH2CH3, -COO(CH2)3CH3, -COOCH2CH(C2H5)C4H9, -COOC8H 17 、-COOC 12 H 25 、-COOC 18 H 37 , at least one of -CH2OOCCH3;

[0039] The structure of unit II is shown in formula II:

[0040] R2 is selected from at least one of -COOCH2CH2OH, -COOCH(CH3)CH2OH, -COOCH2CH2CH2CH2OH;

[0041] The mass ratio of unit I to unit II is 15-30:70-90.

[0042] The binder for the insulating coating of a lithium-ion battery of the present invention adopts specific component units and proportions, can provide good adhesion to copper foil, has excellent wetting and bonding effects on polyolefin separators, has good mechanical shear resistance, good freeze-thaw resistance, good flexibility, and can improve the anti-permeability with the negative electrode slurry, avoiding quality defects such as shadow formation or powder leakage.

[0043] In a specific embodiment of the present invention, the acrylate polymer further includes a unit III, and the structure of the unit III is shown in Formula III:

[0044] R3 is selected from at least one of -H and -CH3; R4 is selected from at least one of -COOH, -CONH2, and -CN.

[0045] In a specific embodiment of the present invention, the proportion of the third unit is less than 5% by weight of the acrylate polymer.

[0046] The acrylic acid ester polymer of the present invention may have a structural formula as shown in Formula IV:

[0047] In one embodiment of the present invention, the first unit is introduced by the first monomer, the second unit is introduced by the second monomer, and the third unit is introduced by the third monomer;

[0048] Wherein, the first monomer includes at least one of ethyl acrylate, butyl acrylate, isooctyl acrylate, n-octyl acrylate, lauryl acrylate, octadecyl acrylate, vinyl acetate, and propylene acetate;

[0049] The second monomer includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate;

[0050] The third monomer includes at least one of acrylic acid and methacrylic acid.

[0051] In a specific embodiment of the present invention, the weight ratio of the first monomer: the second monomer: the third monomer is 10-30:70-90:0-5; preferably, the weight ratio of the first monomer: the second monomer: the third monomer is 15-30:70-80:0-5; more preferably, the weight ratio of the first monomer: the second monomer: the third monomer is 15-25:70-80:1-5.

[0052] The acrylate polymer of the present invention can be prepared using conventional polymerization methods. In one embodiment of the present invention, monomers I, II, and III are polymerized in the presence of a protective colloid to produce the acrylate polymer; the protective colloid comprises at least one of cyclodextrin, polyvinyl pyrrolidone, polyvinyl alcohol, and hydroxymethyl cellulose. The use of a protective colloid not only stabilizes the emulsion but also increases the surface tension of the system, allowing the surface tension of the slurry system to reach 55-70 mN / m. This further improves the impermeability with the negative electrode slurry, preventing quality defects such as shadowing or powder leakage.

[0053] The amount of protective colloid used can be conventional. In one embodiment of the present invention, the amount of protective colloid used is less than 10% by weight of the polymerized monomers; preferably, the amount of protective colloid used is 1-5% by weight of the polymerized monomers. The polymerized monomers are the sum of monomers I, II, and III.

[0054] In one embodiment of the present invention, the binder for the lithium-ion battery insulating coating further comprises a solvent. In a preferred embodiment, the solvent is water. The binder for the lithium-ion battery insulating coating of the present invention can be a water-based binder, which is more environmentally friendly.

[0055] In a specific embodiment of the present invention, based on 100 parts by weight of the binder for the insulating coating of lithium-ion batteries, the mass percentage of the acrylic ester polymer is 20-30%.

[0056] The binder for the insulating coating of a lithium ion battery of the present invention can be obtained by polymerization using conventional methods. In one embodiment of the present invention, the binder for the insulating coating of a lithium ion battery of the present invention is prepared using the following method:

[0057] 1) Add protective colloid, sodium carbonate, and water to a reactor, stir to dissolve, pass nitrogen, and heat;

[0058] 2) Mix the first monomer, the second monomer, the third monomer and other polymerization monomers uniformly, take out some of the mixed monomers, and add them into the reaction kettle to form a base;

[0059] 3) Add initiator solution (solution concentration 20%) to the reactor to initiate solution polymerization, and adjust the system temperature to the polymerization reaction temperature;

[0060] 4) When the temperature of the reaction system stabilizes, begin to dropwise add the remaining mixed monomers for 1.5-3 hours;

[0061] 5) Add initiator to the reactor twice every 3 hours;

[0062] 6) After the last addition of the initiator, the reaction is kept warm for a certain period of time, then the temperature is lowered, the pH is adjusted, and the material is discharged to obtain a binder for the insulating coating of a lithium ion battery.

[0063] Preferably, the initiator is one or a combination of ammonium persulfate and potassium persulfate. Preferably, the weight percentage of the initiator to the polymerization monomer is 0.2-2.0%. Preferably, in step 3), the reaction temperature is 60-80°C. Preferably, in step 6), the holding time is 9-5 hours.

[0064] The present invention also provides the use of the adhesive for lithium ion battery insulation coating of the present invention in edge coating.

[0065] The adhesive for the insulating coating of a lithium ion battery of the present invention can be used as an edge coating adhesive and applied to the insulating coating of a lithium ion battery.

[0066] The specific embodiments of the present invention are further described below in conjunction with examples, but the present invention is not limited to the scope of the examples.

[0067] Example 1

[0068] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 133.2 kg of vinyl acetate, 710.4 kg of hydroxyethyl acrylate and 45.4 kg of acrylic acid.

[0069] The preparation method comprises the following steps:

[0070] In the first step, 18 kg of cyclodextrin, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 70°C;

[0071] In the second step, 26.6 kg of vinyl acetate, 142.1 kg of hydroxyethyl acrylate monomer, and 8.9 kg of acrylic acid were mixed and added to the reactor;

[0072] In the third step, 20 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0073] Step 4: Evenly mix 106.6 kg of vinyl acetate, 568.3 kg of hydroxyethyl acrylate, and 36.5 kg of acrylic acid. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 1.5 hours.

[0074] Step 5: Add 10 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0075] Step 6: After the last addition of the initiator, the reaction was kept warm for 6 hours, then cooled to 40°C, and sodium carbonate was added to adjust the pH to 7 before discharging the material to obtain a binder for the insulating coating of lithium-ion batteries.

[0076] Preparation process of insulating coated negative electrode sheet:

[0077] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0078] Example 2

[0079] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 177.6 kg of butyl acrylate, 692.6 kg of hydroxypropyl acrylate and 17.76 kg of methacrylic acid.

[0080] The preparation method comprises the following steps:

[0081] In the first step, 18 kg of polyvinyl pyrrolidone, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred and dissolved, and nitrogen was passed through the reactor, and the temperature was raised to 70°C.

[0082] In the second step, 35.5 kg of butyl acrylate, 138.5 kg of hydroxypropyl acrylate, and 3.55 kg of methacrylic acid were mixed and added to the reactor;

[0083] In the third step, 30 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to 80°C;

[0084] Step 4: Evenly mix 142.1 kg of butyl acrylate, 554.1 kg of hydroxypropyl acrylate, and 14.21 kg of methacrylic acid. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 2 hours.

[0085] Step 5: Add 15 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0086] Step 6: After the last addition of the initiator, the reaction was kept warm for 9 hours, then cooled to 40°C, and sodium carbonate was added to adjust the pH to 7 before discharging the material to obtain a binder for the insulating coating of lithium-ion batteries.

[0087] Preparation process of insulating coated negative electrode sheet:

[0088] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0089] Example 3

[0090] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 222 kg of isooctyl acrylate, 657.1 kg of hydroxybutyl acrylate, and 10.01 kg of acrylic acid.

[0091] The preparation method comprises the following steps:

[0092] In the first step, 18 kg of polyvinyl alcohol, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred and dissolved, and nitrogen was passed through, and the temperature was raised to 60°C;

[0093] In the second step, 44.4 kg of isooctyl acrylate, 131.4 kg of hydroxybutyl acrylate, and 1.8 kg of acrylic acid were mixed and added to the reactor;

[0094] In the third step, 40 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was stabilized at 60°C;

[0095] Step 4: Evenly mix 177.6 kg of isooctyl acrylate, 525.7 kg of hydroxybutyl acrylate, and 8.21 kg of acrylic acid. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 3 hours.

[0096] Step 5: Add 20 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0097] Step 6: After the last addition of the initiator, the reaction was kept warm for 15 hours, then cooled to 40°C, sodium carbonate was added to adjust the pH to 7, and the material was discharged to obtain a binder for the insulating coating of lithium-ion batteries.

[0098] Preparation process of insulating coated negative electrode sheet:

[0099] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0100] Example 4

[0101] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 233.3 kg of vinyl acetate, 621.6 kg of hydroxyethyl acrylate, 20 kg of butyl acrylate and 13.1 kg of isooctyl acrylate.

[0102] The preparation method comprises the following steps:

[0103] In the first step, 9 kg of cyclodextrin, 9 kg of polyvinylpyrrolidone, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 70°C;

[0104] In the second step, 53.3 kg of vinyl acetate and 124.3 kg of hydroxyethyl acrylate monomer were mixed evenly and added to the reactor;

[0105] In the third step, 30 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0106] Step 4: Evenly mix 180 kg of vinyl acetate, 20 kg of butyl acrylate, 13.1 kg of isooctyl acrylate, and 497.3 kg of hydroxyethyl acrylate. When the temperature of the reaction system drops to 68°C, start adding the mixed monomers dropwise for 1.5 hours.

[0107] Step 5: Add 15 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0108] Step 6: After the last addition of the initiator, the reaction was kept warm for 12 hours, then cooled to 40°C, and sodium carbonate was added to adjust the pH to 7 before discharging the material to obtain a binder for the insulating coating of lithium-ion batteries.

[0109] Preparation process of insulating coated negative electrode sheet:

[0110] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0111] Example 5

[0112] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 177.6 kg of vinyl acetate, 142.1 kg of hydroxyethyl acrylate, 500 kg of hydroxypropyl acrylate and 68.3 kg of hydroxybutyl acrylate.

[0113] The preparation method comprises the following steps:

[0114] In the first step, 12 kg of hydroxymethyl cellulose, 6 kg of polyvinyl alcohol, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred and dissolved, and nitrogen was passed through, and the temperature was raised to 70°C;

[0115] In the second step, 35.5 kg of vinyl acetate and 142.1 kg of hydroxyethyl acrylate monomer were mixed evenly and added to the reactor;

[0116] In the third step, 40 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0117] Step 4: Evenly mix 142.1 kg of vinyl acetate, 500 kg of hydroxypropyl acrylate, and 68.3 kg of hydroxybutyl acrylate. When the temperature of the reaction system rises to 75°C, start adding the mixed monomers dropwise for 2 hours.

[0118] Step 5: Add 20 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0119] Step 6: After the last addition of the initiator, the reaction was kept warm for 10 hours, then cooled to 40° C., sodium carbonate was added to adjust the pH to 7, and the material was discharged to obtain a binder for the insulating coating of lithium-ion batteries.

[0120] Preparation process of insulating coated negative electrode sheet:

[0121] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0122] Example 6

[0123] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 177.6 kg of vinyl acetate, 692.6 kg of hydroxyethyl acrylate, 3.55 kg of acrylic acid and 14.21 kg of methacrylic acid.

[0124] The preparation method comprises the following steps:

[0125] In the first step, 15 kg of polyvinyl pyrrolidone, 3 kg of polyvinyl alcohol, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 70°C;

[0126] In the second step, 35.5 kg of vinyl acetate, 138.5 kg of hydroxyethyl acrylate, and 3.55 kg of acrylic acid were mixed and added to the reactor;

[0127] In the third step, 20 kg of monomer and 20% initiator solution were added to the reactor to initiate polymerization, and the system temperature was raised to about 80°C;

[0128] Step 4: Evenly mix 142.1 kg of vinyl acetate, 554.1 kg of hydroxyethyl acrylate, and 14.21 kg of methacrylic acid. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 2.5 hours.

[0129] Step 5: Add 10 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0130] Step 6: After the last addition of the initiator, the reaction was kept warm for 9 hours, then cooled to 40°C, and sodium carbonate was added to adjust the pH to 7 before discharging the material to obtain a binder for the insulating coating of lithium-ion batteries.

[0131] Preparation process of insulating coated negative electrode sheet:

[0132] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0133] Example 7

[0134] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 44.4 kg of isooctyl acrylate, 177.6 kg of vinyl acetate, 124.3 kg of hydroxybutyl acrylate, 497.3 kg of hydroxyethyl acrylate, 8.9 kg of methacrylic acid and 35.5 kg of acrylic acid.

[0135] The preparation method comprises the following steps:

[0136] In the first step, 18 kg of cyclodextrin, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 70°C;

[0137] In the second step, 44.4 kg of isooctyl acrylate, 124.3 kg of hydroxybutyl acrylate, and 8.9 kg of methacrylic acid were mixed and added to the reactor;

[0138] In the third step, 40 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0139] Step 4: Evenly mix 177.6 kg of vinyl acetate, 497.3 kg of hydroxyethyl acrylate, and 35.5 kg of acrylic acid. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 1.5 hours.

[0140] Step 5: Add 20 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0141] Step 6: After the last addition of the initiator, the reaction was kept warm for 9 hours, then cooled to 40°C, and sodium carbonate was added to adjust the pH to 7 before discharging the material to obtain a binder for the insulating coating of lithium-ion batteries.

[0142] Preparation process of insulating coated negative electrode sheet:

[0143] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0144] Example 8

[0145] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 44.4 kg vinyl acetate, 177.6 kg butyl acrylate, 129.6 kg hydroxyethyl acrylate, 518.6 kg hydroxybutyl acrylate, 3.55 kg acrylic acid and 14.21 kg methacrylic acid.

[0146] The preparation method comprises the following steps:

[0147] In the first step, 18 kg of cyclodextrin, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 70°C;

[0148] In the second step, 44.4 kg of vinyl acetate, 129.6 kg of hydroxyethyl acrylate, and 3.55 kg of acrylic acid were mixed and added to the reactor;

[0149] In the third step, 20 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0150] Step 4: Evenly mix 177.6 kg of butyl acrylate, 518.6 kg of hydroxybutyl acrylate, and 14.21 kg of methacrylic acid. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 2 hours.

[0151] Step 5: Add 10 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0152] Step 6: After the last addition of the initiator, the reaction was kept warm for 12 hours, then cooled to 40°C, and sodium carbonate was added to adjust the pH to 7 before discharging the material to obtain a binder for the insulating coating of lithium-ion batteries.

[0153] Preparation process of insulating coated negative electrode sheet:

[0154] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0155] Example 9

[0156] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 195.3 kg of vinyl acetate, 657.1 kg of hydroxyethyl acrylate and 35.5 kg of acrylic acid.

[0157] The preparation method comprises the following steps:

[0158] In the first step, 18 kg of cyclodextrin, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 70°C;

[0159] In the second step, 39.1 kg of vinyl acetate, 131.4 kg of hydroxyethyl acrylate, and 7.1 kg of acrylic acid were mixed and added to the reactor;

[0160] In the third step, 30 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0161] Step 4: Evenly mix 156.2 kg of vinyl acetate, 525.7 kg of hydroxyethyl acrylate, and 28.4 kg of acrylic acid. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 3 hours.

[0162] Step 5: Add 15 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0163] Step 6: After the last addition of the initiator, the reaction was kept warm for 15 hours, then cooled to 40°C, sodium carbonate was added to adjust the pH to 7, and the material was discharged to obtain a binder for the insulating coating of lithium-ion batteries.

[0164] Preparation process of insulating coated negative electrode sheet:

[0165] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0166] Example 10

[0167] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 177.6 kg of vinyl acetate, 692.6 kg of hydroxyethyl acrylate, 3.55 kg of acrylamide and 14.21 kg of methacrylamide.

[0168] The preparation method comprises the following steps:

[0169] In the first step, 15 kg of hydroxymethyl cellulose, 3 kg of polyvinyl pyrrolidone, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred and dissolved, and nitrogen was passed through, and the temperature was raised to 70°C;

[0170] In the second step, 35.5 kg of vinyl acetate, 138.5 kg of hydroxyethyl acrylate, and 3.55 kg of acrylamide were mixed and added to the reactor;

[0171] In the third step, 20 kg of monomer and 20% initiator solution were added to the reactor to initiate polymerization, and the system temperature was raised to about 80°C;

[0172] Step 4: Evenly mix 142.1 kg of vinyl acetate, 554.1 kg of hydroxyethyl acrylate, and 14.21 kg of methacrylamide. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 2.5 hours.

[0173] Step 5: Add 10 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0174] Step 6: After the last addition of the initiator, the reaction was kept warm for 9 hours, then cooled to 40°C, and sodium carbonate was added to adjust the pH to 7 before discharging the material to obtain a binder for the insulating coating of lithium-ion batteries.

[0175] Preparation process of insulating coated negative electrode sheet:

[0176] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0177] Example 11

[0178] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 200 kg of isooctyl acrylate, 22 kg of lauryl acrylate, 657.1 kg of hydroxybutyl acrylate, and 10.01 kg of methacrylamide.

[0179] The preparation method comprises the following steps:

[0180] In the first step, 18 kg of polyvinyl pyrrolidone, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 60°C;

[0181] In the second step, 40 kg of isooctyl acrylate, 4.4 kg of lauryl acrylate, 131.4 kg of hydroxybutyl acrylate, and 1.8 kg of methacrylamide were mixed and added to the reactor;

[0182] In the third step, 40 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was stabilized at 60°C;

[0183] Step 4: Evenly mix 160 kg of isooctyl acrylate, 17.6 kg of dodecyl acrylate, 525.7 kg of hydroxybutyl acrylate, and 8.21 kg of methacrylamide. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 3 hours.

[0184] Step 5: Add 20 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0185] Step 6: After the last addition of the initiator, the reaction was kept warm for 15 hours, then cooled to 40°C, sodium carbonate was added to adjust the pH to 7, and the material was discharged to obtain a binder for the insulating coating of lithium-ion batteries.

[0186] Preparation process of insulating coated negative electrode sheet:

[0187] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0188] Example 12

[0189] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 44.4 kg of octadecyl acrylate, 177.6 kg of butyl acrylate, 129.6 kg of hydroxyethyl acrylate, 518.6 kg of hydroxybutyl acrylate, 3.55 kg of acrylonitrile and 14.21 kg of methacrylonitrile.

[0190] The preparation method comprises the following steps:

[0191] In the first step, 18 kg of cyclodextrin, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 70°C;

[0192] In the second step, 44.4 kg of octadecyl acrylate, 129.6 kg of hydroxyethyl acrylate, and 3.55 kg of acrylonitrile were mixed and added to the reactor;

[0193] In the third step, 20 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0194] Step 4: Evenly mix 177.6 kg of butyl acrylate, 518.6 kg of hydroxybutyl acrylate, and 14.21 kg of methacrylonitrile. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 2 hours.

[0195] Step 5: Add 10 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0196] Step 6: After the last addition of the initiator, the reaction was kept warm for 12 hours, then cooled to 40°C, and sodium carbonate was added to adjust the pH to 7 before discharging the material to obtain a binder for the insulating coating of lithium-ion batteries.

[0197] Preparation process of insulating coated negative electrode sheet:

[0198] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0199] Example 13

[0200] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 233.3 kg of vinyl acetate, 621.6 kg of hydroxyethyl acrylate, 20 kg of butyl acrylate, 10.1 kg of n-octyl acrylate, and 3 kg of acrylonitrile.

[0201] The preparation method comprises the following steps:

[0202] In the first step, 9 kg of cyclodextrin, 9 kg of polyvinyl alcohol, 5.6 kg of sodium carbonate, and 2046 kg of water were added to a reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 70°C;

[0203] In the second step, 53.3 kg of vinyl acetate and 124.3 kg of hydroxyethyl acrylate monomer were mixed evenly and added to the reactor;

[0204] In the third step, 30 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0205] Step 4: Evenly mix 180 kg of vinyl acetate, 20 kg of butyl acrylate, 10.1 kg of n-octyl acrylate, 497.3 kg of hydroxyethyl acrylate, and 3 kg of acrylonitrile. When the temperature of the reaction system drops to 68°C, start adding the mixed monomers dropwise for 1.5 hours.

[0206] Step 5: Add 15 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0207] Step 6: After the last addition of the initiator, the reaction was kept warm for 12 hours, then cooled to 40°C, and sodium carbonate was added to adjust the pH to 7 before discharging the material to obtain a binder for the insulating coating of lithium-ion batteries.

[0208] Preparation process of insulating coated negative electrode sheet:

[0209] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0210] Comparative Example 1

[0211] A binder for lithium-ion battery insulating coating, the synthetic monomers of which are: 178kg vinyl acetate and 710kg hydroxyethyl acrylate.

[0212] The preparation method comprises the following steps:

[0213] In the first step, 5.6 kg of sodium carbonate and 2046 kg of water were added to the reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 70°C;

[0214] In the second step, 18 kg of vinyl acetate and 71 kg of hydroxyethyl acrylate monomer were mixed evenly and added to the reactor;

[0215] In the third step, 30 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0216] Step 4: Evenly mix 160 kg of vinyl acetate and 639 kg of hydroxyethyl acrylate. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 3 hours.

[0217] Step 5: Add 15 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0218] Step 6: After the last addition of the initiator, the reaction was kept warm for 9 hours, then cooled to 40°C, and sodium carbonate was added to adjust the pH to 7 before discharging the material to obtain a binder for the insulating coating of lithium-ion batteries.

[0219] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) according to the ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the solid content of the slurry to 60%, disperse the slurry in a dispersing equipment at a speed of 1200r / min for 3.5h, and then filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet bonded with a diaphragm.

[0220] Comparative Example 2

[0221] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 300.8 kg of vinyl acetate and 577.2 kg of hydroxyethyl acrylate.

[0222] The preparation method comprises the following steps:

[0223] In the first step, 5.6 kg of sodium carbonate and 2046 kg of water were added to the reactor, stirred to dissolve, and nitrogen was passed through, and the temperature was raised to 70°C;

[0224] In the second step, 46.62 kg of vinyl acetate and 86.58 kg of hydroxyethyl acrylate monomers were mixed evenly and added to the reactor;

[0225] In the third step, 30 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0226] Step 4: Evenly mix 264.18 kg of vinyl acetate and 490.62 kg of hydroxyethyl acrylate. When the temperature of the reaction system drops to 70°C, start adding the mixed monomers dropwise for 3 hours.

[0227] Step 5: Add 15 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0228] Step 6: After the last addition of initiator, the reaction was kept warm for 12 hours and then cooled to 40°C. It was found that the rubber solution was stratified and demulsified.

[0229] Comparative Example 3

[0230] A binder for lithium-ion battery insulating coating, wherein the synthetic monomers are: 300.8 kg of vinyl acetate and 577.2 kg of hydroxyethyl acrylate.

[0231] The preparation method comprises the following steps:

[0232] In the first step, 5.6 kg of sodium carbonate, 2046 kg of water, and 1.34 kg of sodium lauryl sulfate were added to the reactor, stirred to dissolve and emulsify, and nitrogen was passed through, and the temperature was raised to 70°C;

[0233] In the second step, 46.62 kg of vinyl acetate and 86.58 kg of hydroxyethyl acrylate monomers were mixed evenly, added to the reactor, and further stirred to dissolve and emulsify;

[0234] In the third step, 30 kg of 20% initiator solution of monomer was added to the reactor to initiate polymerization, and the system temperature was raised to about 72°C;

[0235] Step 4: Evenly mix 264.18 kg of vinyl acetate and 490.62 kg of hydroxyethyl acrylate. When the temperature of the reaction system drops to 70 degrees, start adding the mixed monomers dropwise for 3 hours.

[0236] Step 5: Add 15 kg of 20% initiator solution of monomer to the reactor twice every 3 hours;

[0237] Step 6: After the last addition of the initiator, the reaction was kept warm for 9 hours, then cooled to 40° C., sodium carbonate was added to adjust the pH to 7, and the material was discharged to obtain a binder for the insulating coating of lithium-ion batteries.

[0238] Take the above 60g binder (solid content 30%), add 82g of boehmite (average particle size 1.5μm) in a ratio of binder dry glue: boehmite = 18:82, add 24.67g of water, adjust the slurry solid content to 60%, disperse the slurry in a dispersion equipment at a speed of 1200r / min for 3.5h, and then filter and demulsify.

[0239] Comparative Example 4

[0240] Take 80.72g of EAA emulsion (solid content 22.3%), add 82g of boehmite (average particle size 1.5μm) in a ratio of binder dry glue: boehmite = 18:82, add 3.95g of water and 0.3g of CMC, adjust the slurry solid content to 60%, disperse the slurry in a dispersion equipment at a speed of 1200r / min for 3.5h, and then filter to break the emulsion.

[0241] Comparative Example 5

[0242] Take 36.68g of water and 0.6g of CMC, disperse them in a dispersion equipment at a speed of 1200r / min for 1h and then filter; add 82g of boehmite (average particle size 1.5μm) and disperse them in a dispersion equipment at a speed of 1200r / min for 3h; lower the stirring rate to 300r / min, take 80.72g of EAA emulsion (solid content 22.3%), slowly add it to the slurry, stir and disperse for 0.5h, and filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and laminate it with a 30×4cm diaphragm. After hot pressing at 100℃ for 1min, cool it to obtain a negative electrode sheet with a bonded diaphragm.

[0243] Comparative Example 6

[0244] Take 47.74g water and 0.6g CMC, disperse them in a dispersion equipment at a speed of 1200r / min for 1h and then filter; add 82g boehmite (average particle size 1.5μm) and disperse them in a dispersion equipment at a speed of 1200r / min for 3h; lower the stirring rate to 300r / min, take 36.36g SBR emulsion (solid content 49.5%), slowly add it to the slurry, stir and disperse for 0.5h, and filter to obtain an insulating coating slurry; apply the insulating coating slurry on the blank copper foil of the negative electrode sheet, dry it at 80℃ for 0.5h, and dry the coating to a thickness of 60μm to obtain a negative electrode sheet coated with an insulating coating, cut it into 30×4.5cm strips, and after bonding it to a 30×4cm diaphragm, use a hot pressing device to hot press at 100℃ for 1min, and cool it to obtain a negative electrode sheet with a bonded diaphragm.

[0245] The performance of the negative electrode sheets of the examples and comparative examples was determined using the following test method:

[0246] 1) Peel strength: Peel strength between the insulating coating and the copper foil: The prepared negative electrode sheet was cut into 10×4 cm pieces. The 8×4 cm portion of the insulating coating on the front side was fixed to a steel plate with double-sided tape. The remaining 2 cm of the copper foil on the outside of the electrode sheet was affixed with 3M tape. A 180° peel test was performed at a peel speed of 100 mm / min using a universal electronic testing machine at 25°C. The average peel force was recorded.

[0247] Peel strength between the separator and the insulating coating: The copper foil on the back of the negative electrode sheet bonded to the separator was fixed to a steel plate with double-sided tape. The separator and the insulating coating were manually pulled 10 cm apart. 3M tape was then applied to the outside of the separated separator. A 180° peel test was performed at a peel speed of 100 mm / min using a universal electronic testing machine at 25°C. The average peel force was recorded.

[0248] The negative electrode sheet coated with the insulating coating and the negative electrode sheet bonded with the separator were immersed in the electrolyte at a temperature of 70°C for 72 hours. Then, a peeling test was performed according to the above method to record the peeling strength between the insulating coating and the copper foil, and between the separator and the insulating coating after immersion in the electrolyte.

[0249] 2) Pole flexibility test: The pole piece flexibility test is carried out with reference to G / BT 1731-1993 "Determination of paint film flexibility". At room temperature, the pole pieces containing insulating coatings prepared in the above embodiments and comparative examples are cut into 25×10 cm, and the middle of the two long sides are horizontally placed on a steel shaft rod with a length of 12 cm, a diameter of 1.5 cm and a base fixed thereon, so that the film layer of the test pole piece faces upward, and then the pole piece is pressed tightly on the shaft rod with the thumb and index finger for 3 seconds. After bending, the thumb and index finger are symmetrical to the center line of the shaft rod. Observe the surface condition of the pole piece after bending, and record the intact pole piece as ○, the slightly cracked pole piece as □, the severely cracked pole piece as ×, and the pole piece that cannot be tested as / .

[0250] 3) Surface Tension Test: Dilute the slurries prepared in the above examples and comparative examples to 1% slurry. Add an appropriate amount of distilled water to the sample stage of a BZY-2 fully automatic surface / interfacial tension meter. Add 0.2 mL of the diluted slurry to a sample dish. Place the dish on the stage, ensuring it fits snugly with the distilled water and no bubbles remain. Clean the temperature probe and place it in the sample, ensuring it does not contact the sides of the dish. Gently shake or rotate the dish horizontally to maintain a uniform temperature. Take a reading when the temperature reaches 25°C.

[0251] 4) Freeze-thaw resistance test: The freeze-thaw resistance test was performed according to GB / T9268-2008: 100 g of the adhesive sample (adhesives of Examples 1-9, Comparative Example 1, and Comparative Examples 3-6) was placed in a test bottle and placed in a refrigerator at -5±2°C; the sample was placed in the refrigerator for 24 hours, taken out, and placed at 23±2°C for 6 hours. The sample was naturally filtered through a 200-mesh filter, and the filter residue was ≤0.5wt%, which was determined to be non-demulsified. Otherwise, the emulsion was broken and failed this test.

[0252] 5) Shear resistance test: Shear resistance test: Take 200g of adhesive sample (adhesives of Examples 1-9, Comparative Example 1, and adhesives of Comparative Examples 3-6), put it into a test bottle, apply a shear force at a linear speed of 15m / s for 30min, and then filter naturally through a 200-mesh filter. If the filter residue is ≤0.5wt%, it is judged that the emulsion is not broken, otherwise it is broken and fails this test.

[0253] The relevant test results are shown in Table 1.

[0254] Table 1 Note: “ / ” indicates that the relevant test cannot be performed due to process problems.

[0255] As can be seen from Table 1, the peeling strength between the insulating coating and the copper foil, and the peeling strength between the diaphragm and the insulating coating prepared in Examples 1 to 13 of the present invention are relatively high.

[0256] From the comparison of Examples 1 to 13 and Comparative Example 1, it can be seen that in the preparation process of the binder of the present invention, the main functions of cyclodextrin, polyvinyl pyrrolidone, polyvinyl alcohol, and hydroxymethyl cellulose are to stabilize the emulsion state, increase the surface tension of the binder, and thereby improve the anti-permeability with the negative electrode slurry (without adding protective colloid, the surface tension of the binder is low, and the negative electrode slurry is easy to penetrate each other, forming quality defects such as shadows or powder leakage).

[0257] By comparison of Examples 1 to 13 and Comparative Example 2, it can be seen that in the preparation process of the binder of the present invention, preferably, the ratio of the first monomer: the second monomer: the third monomer is 10 to 30:70 to 90:0 to 5; further preferably, the ratio of the first monomer: the second monomer: the third monomer is 15 to 25:70 to 80:1 to 5; in Comparative Example 2, the ratio of the first monomer is further increased to 35%, and the prepared binder is unstable and easily stratified and demulsified.

[0258] From the comparison of Examples 1 to 13 and Comparative Example 3, it can be seen that when an emulsifier is added to emulsify and stabilize the binder prepared by monomer I at a ratio of 35%, demulsification problem will occur when boehmite is dispersed in a one-step high-stirring method to prepare an insulating coating slurry.

[0259] From the comparison of Examples 1 to 13 and Comparative Example 4, it can be seen that EAA emulsion is not resistant to shear (demulsification due to high-speed stirring) when used for lithium-ion battery insulating coating. For example, demulsification problems are prone to occur when using a one-step high-stirring dispersion method for boehmite to prepare insulating coating slurry.

[0260] From the comparison between Examples 1 to 13 and Comparative Example 5, it can be seen that the method of first dispersing boehmite with CMC solution and then adding EAA emulsion with low-speed stirring has the problems of being more complicated, taking a long time, and having low production efficiency.

[0261] From the comparison of Examples 1 to 13 and Comparative Example 6, it can be seen that the surface tension of the SBR emulsion is relatively high, but the thermal bonding effect on the diaphragm is relatively poor, which cannot meet market demand.

[0262] In summary, the water-based electrode ear edge coating prepared in this application has good resistance to high-speed shear and freeze-thaw, no demulsification phenomenon, good dispersion / storage stability, and the prepared negative electrode plate has good flexibility and is not hard and brittle.

Claims

1. A binder for an insulating coating of a lithium-ion battery, characterized in that: Comprising an acrylate polymer; the structural formula of the acrylate polymer comprises unit I and unit II, wherein, The structure of unit I is shown in formula I: R1 is selected from -OOCCH3, -COOCH2CH3, -COO(CH2)3CH3, -COOCH2CH(C2H5)C4H9, -COOC8H 17 、-COOC 12 H 25 、-COOC 18 H 37 , at least one of -CH2OOCCH3; The structure of unit II is shown in formula II: R2 is selected from at least one of -COOCH2CH2OH, -COOCH(CH3)CH2OH, -COOCH2CH2CH2CH2OH; The mass ratio of unit I to unit II is 15-30:70-90.

2. The binder for lithium-ion battery insulating coating according to claim 1, wherein: The acrylic ester polymer further includes a unit III, and the structure of the unit III is shown in Formula III: R3 is selected from at least one of -H and -CH3; R4 is selected from at least one of -COOH, -CONH2, and -CN.

3. The binder for lithium-ion battery insulating coating according to claim 2, wherein: The proportion of the III unit is less than 5% by weight of the acrylic ester polymer.

4. The binder for lithium-ion battery insulating coating according to claim 2, wherein: The first unit is introduced by the first monomer, the second unit is introduced by the second monomer, and the third unit is introduced by the third monomer; Wherein, the first monomer includes at least one of ethyl acrylate, butyl acrylate, isooctyl acrylate, n-octyl acrylate, lauryl acrylate, octadecyl acrylate, vinyl acetate, and propylene acetate; The second monomer includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxybutyl acrylate; The third monomer includes at least one of acrylic acid, methacrylic acid, acrylamide, methacrylamide, acrylonitrile, and methacrylonitrile.

5. The binder for lithium-ion battery insulating coating according to claim 4, characterized in that: The weight ratio of the first monomer: the second monomer: the third monomer is 10-30:70-90:0-5.

6. The binder for lithium-ion battery insulating coating according to claim 5, characterized in that: The weight ratio of the first monomer: the second monomer: the third monomer is 15-30:70-80:0-5.

7. The binder for lithium-ion battery insulating coating according to claim 6, characterized in that: The weight ratio of the first monomer: the second monomer: the third monomer is 15-25:70-80:1-5.

8. The binder for lithium-ion battery insulating coating according to claim 4, characterized in that: The first monomer, the second monomer and the third monomer are polymerized in the presence of a protective colloid to obtain an acrylate polymer; the protective colloid comprises at least one of cyclodextrin, polyvinyl pyrrolidone, polyvinyl alcohol and hydroxymethyl cellulose.

9. The binder for lithium-ion battery insulating coating according to claim 8, characterized in that: The amount of the protective colloid is less than 10% of the weight of the polymerized monomers.

10. The binder for lithium-ion battery insulating coating according to claim 9, characterized in that: The amount of protective colloid used is 1 to 5% of the weight of the polymerized monomers.

11. The binder for lithium-ion battery insulating coating according to claim 1, wherein: Also included are solvents.

12. The binder for lithium-ion battery insulating coating according to claim 11, characterized in that: The solvent is water.

13. The binder for lithium-ion battery insulating coating according to claim 11, characterized in that: Based on 100 parts of the total mass, the mass percentage of the acrylic ester polymer is 20-30%.

14. Use of the binder for lithium ion battery insulating coating according to any one of claims 1 to 13 in edge coating.

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