WO2024056103A1 - Water-based binder, and preparation method and use therefor - Google Patents

Abstract

The invention belongs to the technical field of lithium-ion batteries, and particularly relates to a water-based binder and a preparation method and use therefor. The water-based binder comprises a polymer containing at least three monomer units. The polymer comprises a first monomer unit, a second monomer unit and a third monomer unit. The first monomer unit has a structure shown in formula I, the second monomer unit has a structure shown in formula II, and the third monomer unit has a structure shown in formula III, wherein R 1 , R 2 , R 3 and R 6 are the same or different, and each independently represents hydrogen, linear alkyl or branched alkyl; R 5 is a group containing a hydroxyl group at an end group. The water-based binder provided in the present invention has good bonding performance, can significantly inhibit the expansion of a silicon negative electrode, and at the same time allow the prepared pole piece to have excellent flexibility, thereby improving the cycle performance of the battery.

Description

A kind of water-based adhesive and its preparation method and use Technical field

The invention belongs to the technical field of lithium ion batteries, and specifically relates to an aqueous binder and its preparation method and use.

Background technique

Today, lithium-ion batteries have been widely used in products such as mobile phones, computers, and electric vehicles, and have great commercial value. At present, the cathode materials of commercial lithium-ion batteries are mainly oxides such as LiCoO ₂ , LiMn ₂ O ₄ and LiFePO ₄ ; the negative electrode materials are mainly graphite. Due to the low theoretical capacity of graphite (372mAh/g), it is difficult to meet the requirements. Due to the rapid development of electronic information and energy technology today, the development of high-capacity silicon-based materials has become a major issue in the development of lithium-ion battery technology. However, since silicon-based materials are accompanied by greater volume expansion and contraction (up to 300%) during charge and discharge, the electrode capacity decays quickly and the cycle performance is poor. Therefore, there is a need to develop binders with high bonding strength and the ability to reduce the expansion of silicon anodes to achieve cycle stability of high-capacity anodes.

Commonly used silicon anode binders in the prior art include SBR (styrene-butadiene rubber) binders and PAA binders. SBR binder is usually used in conjunction with CMC. SBR itself has low strength, poor bonding force, and poor resistance to expansion of the counter electrode. Therefore, when used in silicon anodes, its cycle performance is often very poor; the PAA adhesive in the existing technology is used. The pole pieces prepared by the bonding agent have poor flexibility and poor processing performance. After the structure is damaged, it is difficult to recover and the cycle performance is poor.

Therefore, developing a binder with excellent bonding performance, flexibility and cycle performance to meet the application requirements of high-performance electrode plates and lithium-ion batteries is an urgent problem in this field.

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a water-based binder and its preparation method and use. The water-based binder provided by the present invention has excellent bonding performance and can significantly inhibit the silicon negative electrode. expansion, while making the prepared pole piece have excellent flexibility, improving the cycle performance of the battery.

In order to achieve the above objects, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides an aqueous binder. The aqueous binder includes a polymer containing at least three monomer units. The polymer includes a first monomer unit, a second monomer unit and The third monomer unit, the first monomer unit has a structure represented by formula I, the second monomer unit has a structure represented by formula II, and the third monomer unit has a structure represented by formula III. ,

Among them, R ₁ , R ₂ , R ₃ and R ₆ are the same or different, and each independently represents hydrogen, a linear alkyl group or a branched alkyl group; R ₅ is a group containing a hydroxyl group at the end group.

Here, the selection of R ₁ , R ₂ and R ₃ is based on the principle of maintaining the water solubility of the monomer, and the selection of R ₅ is based on the principle of maintaining the water solubility of the monomer. Maintain the water solubility of the monomer as a principle.

The water-based binder provided by the present invention has excellent bonding properties and can significantly inhibit the expansion of the silicon negative electrode. At the same time, the prepared pole piece has excellent flexibility and improves the cycle performance of the battery.

In the above water-based binder, as a preferred embodiment, R ₅ represents a linear alkyl group with 1 to 6 carbon atoms substituted by a hydroxyl group, and a branched alkyl group with a carbon number of 1 to 6 substituted by a hydroxyl group. , -CH ₂ CH ₂ OCH ₂ CH ₂ OH or -(CH ₂ CH ₂ O) _n H, n≥3 (for example, n can be 3, 5, 7 or 10, etc.).

In the above water-based binder, as a preferred embodiment, R ₁ , R ₂ , R ₃ and R ₆ are the same or different, and each independently represents hydrogen, a linear alkyl group with 1 to 6 carbon atoms or carbon Branched alkyl group with atomic number 1-6.

In the above water-based binder, as a preferred embodiment, R ₅ represents -CH ₂ CH ₂ OH, CH ₂ CH ₂ CH ₂ OH, -CH ₂ CH ₂ OCH ₂ CH ₂ OH or -(CH ₂ CH ₂ O ) _n H, n≥3 (for example, n can be 3, 5, 7 or 10, etc.).

In the above water-based binder, as a preferred embodiment, R ₁ represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH (CH ₃ ) ₂ ; R ₂ represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH(CH ₃ ) ₂ ; R ₃ Represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH(CH ₃ ) ₂ ; R ₆ represents hydrogen, methyl, ethyl or -CH(CH ₃ ) ₂ .

In the above water-based binder, as a preferred embodiment, the polymer further includes a fourth monomer unit, and the fourth monomer unit has a structure represented by Formula IV:

Among them, R ₄ represents hydrogen, linear alkyl or branched alkyl; M represents H, Li, Na or K.

In the above water-based binder, as a preferred embodiment, R ₄ represents hydrogen, a linear alkyl group with 1 to 6 carbon atoms or a branched alkyl group with 1 to 6 carbon atoms. For example, R ₄ represents Hydrogen, methyl, ethyl or -CH(CH ₃ ) ₂ .

Among the above water-based binders, as a preferred embodiment, the solid content of the water-based binder is 9.5-10.5%, and the viscosity is 8000-30000cps (for example, the viscosity can be 8000cps, 10000cps, 15000cps, 20000cps, 25000cps or 30000cps wait).

Among the above-mentioned water-based binders, as a preferred embodiment, the polymer has a structure represented by Formula V:

Among them, M represents H, Li, Na or K;

R ₁ represents hydrogen, a linear alkyl group or a branched alkyl group. Preferably, R ₁ represents hydrogen, a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 1 to 6 carbon atoms, and more Preferably, the R ₁ represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH(CH ₃ ) ₂ ;

R ₂ represents hydrogen, a linear alkyl group or a branched alkyl group. Preferably, R ₂ represents hydrogen, a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 1 to 6 carbon atoms, and more Preferably, the R ₂ represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH(CH ₃ ) ₂ ;

R ₃ represents hydrogen, a linear alkyl group or a branched alkyl group. Preferably, R ₃ represents hydrogen, a linear alkyl group with 1 to 6 carbon atoms or a branched alkyl group with 1 to 6 carbon atoms, and more Preferably, the R ₃ represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH(CH ₃ ) ₂ ;

R ₄ represents hydrogen, a linear alkyl group or a branched alkyl group. Preferably, R ₄ represents hydrogen, a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 1 to 6 carbon atoms. , for example, R ₄ represents hydrogen, methyl, ethyl or -CH(CH ₃ ) ₂ ;

R ₅ is a group containing a hydroxyl group at the terminal group. The terminal hydroxyl group is more likely to contact and interact with the active material, making it easier for the pole piece coating to form a three-dimensional network structure and improve the ability to inhibit expansion. Preferably, R ₅ represents a linear alkyl group with 1 to 6 carbon atoms substituted by hydroxyl group, a branched alkyl group with 1 to 6 carbon atoms substituted by hydroxyl group, -CH ₂ CH ₂ OCH ₂ CH ₂ OH or -(CH ₂ CH ₂ O) _n H, n≥3, more preferably, the R ₅ represents -CH ₂ CH ₂ OH, CH ₂ CH ₂ CH ₂ OH, -CH ₂ CH ₂ OCH ₂ CH ₂ OH or -(CH ₂ CH ₂ O) _n H, n≥3;

R ₆ represents hydrogen, a linear alkyl group or a branched alkyl group. Preferably, R ₆ represents hydrogen, a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 1 to 6 carbon atoms, and more Preferably, the R ₆ represents hydrogen, methyl, ethyl or -CH(CH ₃ ) ₂ ;

a:b:c:d＝(30～80):(0～50):(5～50):(5-30), for example, a:b:c:d can be 40:30:15:15, 40:30:10:20, 60:0:20:20, 30:20:40:10 or 30:20:20:30, etc.; a:b:c:d are the individual monomers. The molar ratio of yuan.

Among the above-mentioned water-based binders, as a preferred embodiment, other preferred value ranges of a can include: (30-60), (30-40), (40-60). Among the above water-based binders, as a preferred embodiment, other preferred value ranges of b can be listed as: (0-40), (0-30), (0-20), (0.5-40), (0.5 ~30), (0.5~20), (0.5~40), (1~30), (1~20), (5~40), (10~40), (10~30), (10~20 ), (5～30), (5～20).

Among the above water-based binders, as a preferred embodiment, other preferred value ranges of c can be listed as: (10~50), (20~50), (30~50), (40~50), (10 ~40), (10~30), (20~40), (5~50).

Among the above water-based binders, as a preferred embodiment, other preferred value ranges of d can be listed as: (10-30), (15-30), (20-30).

Among the above water-based binders, as a preferred embodiment, a:b:c:d=(30～80):(0～50):(5～50):(10-30); preferably, a :b:c:d＝(30～80):(0～50):(10～40):(10-30).

In the above water-based binder, as a preferred embodiment, based on the total mole number of monomer units corresponding to a, b, c, and d being 100%, the mole percentage of the monomer unit corresponding to d is 10% to 30 % can be, for example, 10% to 15%, 15% to 20%, or 20% to 30%. By limiting the molar percentage of the monomer unit corresponding to d to 10% to 30%, the present invention can improve the peeling strength of the binder and at the same time improve the ability to inhibit the expansion of the silicon negative electrode.

In the water-based binder provided by the present invention, as a preferred embodiment, the molar ratio of the hydroxyl group to the cyano group is 1/4 to 4, which can enable the resulting polymer to maintain high intermolecular hydrogen bonding force, thereby improving The cohesion of the high-pole coating further improves its ability to inhibit expansion.

In the above water-based binder, as a preferred embodiment, the molar ratio of the hydroxyl group to the cyano group is 1/4 to 1.

In the above water-based binder, as a preferred embodiment, the molar ratio of the hydroxyl group to the cyano group is 1/4 to 1.5.

In the above water-based binder, as a preferred embodiment, the molar ratio of the hydroxyl group to the cyano group is 1.5 to 4.

In a second aspect, the present invention provides a method for preparing an aqueous adhesive as described in the first aspect, comprising the following steps:

Under the action of an initiator, polymer monomers undergo a polymerization reaction in a reaction solvent to obtain the water-based binder, wherein the polymer monomers include acrylamide monomers, vinyl ether monomers and acrylonitrile. Class singleton.

The aqueous binder prepared by the preparation method provided by the invention has high adhesive force, can significantly inhibit the expansion of the silicon negative electrode, and improve the cycle performance of the battery.

In the above preparation method of the water-based adhesive, as a preferred embodiment, the polymer monomer further includes an acrylic monomer.

In the preparation method of the above-mentioned water-based binder, as a preferred embodiment, the molar ratio of the acrylamide monomer, acrylic acid monomer, vinyl ether monomer and the acrylonitrile monomer is (30 ~80):(0~50):(5~50):(5-30), for example, it can be 40:30:15:15, 40:30:10:20, 60:0:20:20, 30 :20:40:10 or 30:20:20:30 etc.

In the preparation method of the above-mentioned water-based binder, as a preferred embodiment, the total number of moles of the acrylamide monomer, acrylic acid monomer, vinyl ether monomer and acrylonitrile monomer is On a 100% basis, the molar percentage of the acrylamide monomer is 30% to 80%, the molar percentage of the acrylic monomer is 0% to 50%, and the molar percentage of the vinyl ether monomer is 5 % to 50%, the molar percentage of the acrylonitrile monomer is 5% to 30%, preferably, the molar percentage of the acrylonitrile monomer is 10% to 30%.

If the molar percentage of the vinyl ether monomer is too large, the water-based adhesive will have poor water solubility and low mechanical strength. If the molar percentage of the vinyl ether monomer is too small, the water-based adhesive will have poor flexibility.

In the above preparation method of the water-based binder, as a preferred embodiment, the acrylamide monomer has a structure represented by formula VI, the vinyl ether monomer has a structure represented by formula VII, and the The acrylonitrile monomer has a structure represented by formula VIII, and the acrylic acid monomer has a structure represented by formula IX,

Among them, the definitions of M, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are the same as those of M, R ₁ , R ₂ , R ₃ , R ₄ , in the water-based binder described in the first aspect. Definition of R ₅ and R ₆ .

In the above preparation method of the water-based binder, as a preferred embodiment, based on the total mole number of the polymer monomer being 100%, the mole number of the initiator is 0.02% to 1.0%, for example, it can be 0.02%, 0.1%, 0.3%, 0.6% or 1%, etc.

In the preparation method of the above-mentioned water-based binder, as a preferred embodiment, under the action of an initiator, the polymer monomer undergoes a polymerization reaction in a reaction solvent to obtain the water-based binder, which includes the following steps:

S1. Add the polymer monomer into the reaction solvent, stir and disperse, and obtain a mixed solution;

S2. Add the initiator to the mixed solution to perform a polymerization reaction. After the reaction is completed, perform vacuuming, alkali neutralization, sieving, and demagnetization to obtain the aqueous binder.

Here, the aqueous binder may be a water-soluble binder for the silicon negative electrode.

In the above preparation method of aqueous binder, as a preferred embodiment, the reaction solvent is water, preferably deionized water.

In the above preparation method of aqueous binder, as a preferred embodiment, in step S1, the stirring speed is 100-800rpm, for example, it can be 100rpm, 300rpm, 500rpm or 800rpm.

In the above preparation method of the water-based binder, as a preferred embodiment, in step S1, after the polymer monomer is added to the reaction solvent, an inert gas is introduced to remove oxygen in the mixed solution.

In the above preparation method of the water-based binder, as a preferred embodiment, the inert gas is nitrogen or argon.

In the above preparation method of aqueous binder, as a preferred embodiment, the initiator is a water-soluble initiator.

In the above preparation method of aqueous binder, as a preferred embodiment, the initiator includes Including at least one of sodium persulfate, potassium persulfate, ammonium persulfate, ammonium persulfate/sodium sulfite, ammonium persulfate/sodium bisulfite, and hydrogen peroxide/ferrous ion.

In the above preparation method of the water-based binder, as a preferred embodiment, adding the initiator to the mixed solution to perform a polymerization reaction includes: adding a first initiator to the mixed solution to perform a polymerization reaction. The first polymerization reaction is carried out, and then the second initiator is added to perform the second polymerization reaction.

In the above preparation method of the water-based binder, as a preferred embodiment, the molar ratio of the first initiator to the second initiator is (0.5-3):1, for example, it can be 0.5:1, 1 :1, 1.5:1, 2:1 or 3:1 etc.

In the above preparation method of the water-based binder, as a preferred embodiment, the first initiator includes at least one of sodium persulfate, potassium persulfate, and ammonium persulfate.

In the above preparation method of the water-based binder, as a preferred embodiment, the second initiator is a redox initiator, including ammonium persulfate/sodium sulfite, ammonium persulfate/sodium bisulfite, hydrogen peroxide/ At least one type of ferrous ions.

Here, the ferrous ion may be a ferrous salt, such as ferrous sulfate, ferrous chloride, etc.

The preparation method provided by the invention can further react the residual monomers and increase the reaction rate by adding a second initiator and limiting the second initiator to a redox initiator, making the polymerization reaction more complete.

In the above preparation method of the water-based binder, as a preferred embodiment, the temperature of the first polymerization reaction is 40°C to 80°C (for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 70℃ or 80℃, etc.), the time is 3 to 10h (for example, it can be 3h, 5h, 7h or 10h, etc.); The temperature of the second polymerization reaction is 70°C to 90°C (for example, it can be 70°C, 80°C, or 90°C, etc.), and the time is 1-3h (for example, it can be 1h, 2h, or 3h, etc.).

In the above preparation method of the water-based adhesive, as a preferred embodiment, in step S2, vacuum is evacuated for 1 to 2 hours, and the absolute vacuum degree is 5 to 50KPa (for example, it can be 5KPa, 10KPa, 15KPa, 20KPa, 40KPa or 50KPa etc.), preferably 10 to 20KPa.

In the above preparation method of the water-based binder, as a preferred embodiment, in step S2, the alkali neutralization includes neutralizing with lithium hydroxide, sodium hydroxide or potassium hydroxide until the pH value is 6.0~ 9.0 (for example, it can be 6.0, 7.0, 8.0 or 9.0, etc.).

In the above preparation method of aqueous binder, as a preferred embodiment, in step S2, the mesh number of the sieved mesh is 150 to 400 mesh, for example, it can be 150 mesh, 200 mesh, 300 mesh or 400 mesh etc.

In the above preparation method of the water-based binder, as a preferred embodiment, in step S2, in the demagnetization, a super-strong magnetic rod demagnetizer is used for demagnetization. Since the prepared aqueous binder will be used in secondary batteries, demagnetization treatment must be performed according to the requirements of its application field.

In the above preparation method of the water-based binder, as a preferred embodiment, in step S2, after the alkali neutralization and before the sieving, the solid content is adjusted to 10±0.5%.

In a third aspect, the present invention provides a use of a water-based adhesive prepared according to the water-based adhesive described in the first aspect or by the preparation method of the water-based adhesive described in the second aspect, wherein the water-based adhesive Junction agents are used in the preparation of lithium-ion batteries.

Among the uses of the above-mentioned water-based adhesive, as a preferred embodiment, the water-based adhesive is used Preparation of negative electrode sheets in lithium-ion batteries.

Methods for preparing battery negative electrodes using binders are well known to those skilled in the art. Preferably, a method for preparing a negative electrode sheet using the binder of the present invention is as follows:

The binder, conductive agent and active material of the present invention are slurried together in deionized water, and the obtained slurry is coated on the current collector to prepare a negative electrode sheet.

In the use of the above water-based binder, as a preferred embodiment, the negative active material in the negative electrode sheet includes silicon-based material.

Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

(1) The water-based binder provided by the present invention has excellent bonding properties and can significantly inhibit the expansion of the silicon negative electrode. At the same time, the prepared pole piece has excellent flexibility and improves the cycle performance of the battery.

(2) The present invention uses acrylamide and its derivatives, acrylonitrile and its derivatives and vinyl ether monomers to perform free radical polymerization in an aqueous solution to obtain a water-soluble polymer with certain flexibility. Medium polar groups -OH, -CONR ₂ R ₃ , -CN, etc. form hydrogen bonds or chemical bonds with silicon particles in the silicon negative electrode, increasing the interaction between the silicon material and graphite, the binder and the active material, A three-dimensional network structure is formed, thereby improving the adhesion force, reducing the expansion of the silicon anode and greatly improving its cycle life.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Those skilled in the art should understand that the embodiments are only to help understand the present invention and should not be regarded as specific to the present invention. limit. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation modes and processes are given. However, the protection scope of the present invention is not limited to the following examples. No specific details are specified in the following examples. The process parameters of the conditions are usually in accordance with conventional conditions.

The endpoints of ranges and any values disclosed in this disclosure are not limited to the precise range or value, but these ranges or values are to be understood to include values approximating those ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges. These values Ranges should be considered to be specifically disclosed in this disclosure.

The process parameters that do not indicate specific conditions in the following examples generally follow conventional conditions. The experimental reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental reagent dosages, unless otherwise specified, are the dosages of reagents used in routine experimental operations.

In a first aspect, embodiments of the present invention provide an aqueous adhesive. The aqueous adhesive includes a polymer containing at least three monomer units. The polymer includes a first monomer unit, a second monomer unit, and a first monomer unit. unit and a third monomer unit, the first monomer unit has a structure represented by formula I, the second monomer unit has a structure represented by formula II, and the third monomer unit has a structure represented by formula III. Structure,

Among them, R ₁ represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH(CH ₃ ) ₂ ; R ₂ represents hydrogen, methyl base, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ Or -CH ₂ CH(CH ₃ ) ₂ ; R ₃ represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH(CH ₃ ) ₂ ; R ₆ represents hydrogen, methyl, ethyl or -CH(CH ₃ ) ₂ ; R ₅ represents -CH ₂ CH ₂ OH, CH ₂ CH ₂ CH ₂ OH, -CH ₂ CH ₂ OCH ₂ CH ₂ OH or -(CH ₂ CH ₂ O) _n H, n≥3;

The polymer further includes a fourth monomer unit, and the fourth monomer unit has a structure represented by Formula IV:

Among them, R ₄ represents hydrogen, methyl, ethyl or -CH(CH ₃ ) ₂ ; M represents H, Li, Na or K;

The polymer has the structure shown in formula V:

Among them, the definitions of M, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are the same as the definitions of M, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ in the embodiment of the present invention. , a:b:c:d=(30～80):(0～50):(5～50):(5-30); preferably, the monomer units corresponding to a, b, c, d When the total number of moles is 100%, the molar percentage of the monomer unit corresponding to d is 10% to 30%.

The water-based binder also includes water, the solid content of the water-based binder is 9.5-10.5%, and the viscosity is 8000-30000 cps.

The invention discloses a water-soluble binder for the silicon negative electrode of a lithium ion battery and a preparation method thereof. The technical problem solved is the problems of low bonding force, excessive expansion and poor cycle performance when traditional binders are used in high-silicon negative electrodes (gram capacity ≥500mAh/g).

The present invention introduces hydroxyl-containing monomers on the basis of commonly used PAA binders. The resulting binder has high strength and a certain degree of flexibility, which is beneficial when applied to high-silicon negative electrodes. With the dispersion of conductive agent and negative electrode material, the polar groups on the polymer can form strong hydrogen bonds and chemical bonds with the polar groups on the surface of the silicon material, thereby forming a three-dimensional cross-linked network structure as a whole and improving adhesion. At the same time, it reduces the expansion of the silicon anode and greatly improves its cycle life. In addition, after the introduction of cyano groups with better complexing ability, the bonding force will be further improved.

In a second aspect, embodiments of the present invention provide a method for preparing the water-based adhesive as described in the first aspect, including the following steps:

S1. Add the polymer monomer to deionized water, stir and disperse to obtain a mixed solution, and pass in an inert gas to remove oxygen in the mixed solution. The stirring speed is 100-800 rpm, and the inert gas is Nitrogen or argon, the polymer monomers include acrylamide monomers, vinyl ether monomers and acrylonitrile monomers, the polymer monomers also include the acrylic monomers, the acrylamide The molar ratio of the acrylic monomer, the acrylic monomer, the vinyl ether monomer and the acrylonitrile monomer is (30~80): (0~50): (5~50): (5-30) ; The acrylamide monomer has a structure represented by formula VI, the vinyl ether monomer has a structure represented by formula VII, the acrylonitrile monomer has a structure represented by formula VIII, and the acrylic acid The quasi-monomer has the structure shown in Formula IX,

Among them, the definitions of M, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are the same as those of M, R ₁ , R ₂ , R ₃ , R ₄ , in the water-based binder described in the first aspect. Definition of R ₅ and R ₆ .

S2. Add the first initiator to the mixed solution to perform the first polymerization reaction, and then add the second initiator to perform the second polymerization reaction. After the reaction is completed, vacuum for 1 to 2 hours until the absolute vacuum degree is 5-50KPa, followed by alkali neutralization, sieving, and demagnetization to obtain the aqueous binder, wherein, based on the total mole number of the polymer monomer being 100%, the first initiator and the The sum of the moles of the second initiator is 0.02% ~ 1.0%; the molar ratio of the first initiator to the second initiator is (0.5 ~ 3): 1, and the first initiator includes: At least one of sodium sulfate, potassium persulfate, and ammonium persulfate, and the second initiator is a redox initiator, including ammonium persulfate/sodium sulfite, ammonium persulfate/sodium bisulfite, hydrogen peroxide/sodium persulfite, At least one of iron ions, the temperature of the first polymerization reaction is 40°C to 80°C, and the time is 3 to 10h; the temperature of the second polymerization reaction is 70°C to 90°C, and the time is 1-3h, The alkali neutralization includes using lithium hydroxide, sodium hydroxide or potassium hydroxide to neutralize until the pH value is 6.0-9.0, the mesh number of the sieved mesh is 150-400 mesh, and the demagnetization , use a super strong magnetic bar demagnetizer to perform demagnetization. After the alkali is neutralized and before the sieving, the solid content is adjusted to 10±0.5%.

In a third aspect, embodiments of the present invention provide a use of the water-based adhesive prepared according to the water-based adhesive described in the first aspect or by the preparation method of the water-based adhesive described in the second aspect, so The aqueous binder is used for the preparation of negative electrode sheets in lithium ion batteries, wherein the negative active material in the negative electrode sheets includes silicon-based materials.

In order to further understand the present invention, the water-based adhesive provided by the present invention and its preparation method and use are described in detail below in conjunction with the examples. The protection scope of the present invention is not limited by the following examples.

Example 1

The water-based adhesive provided in this embodiment includes a polymer with the following structure:

Among them, a:b:c:d=40:30:15:15.

The preparation method of the water-based adhesive provided in this embodiment includes the following steps:

Add 300g deionized water to the reaction kettle at room temperature, then add 0.4 mol of acrylamide, 0.3 mol of acrylic acid, 0.15 mol of vinyl glycol ether and 0.15 mol of acrylonitrile in order, stir and disperse, the stirring speed is 200 rpm, and pass in nitrogen (Nitrogen flow rate is 2L/h), the nitrogen gas is introduced for 1 hour to remove the oxygen in the solution system (mixed solution), and then the temperature is raised to 50°C. After the temperature stabilizes, 0.001 mol of potassium persulfate as the initiator is added to proceed with polymerization. Reaction, react for 7 hours; adjust the temperature to 80°C, then add 0.001 mol of redox initiator ammonium persulfate and 0.001 mol of sodium bisulfite, carry out polymerization reaction, and react for 2 hours to remove residual monomers. After the reaction is completed, Evacuate for 1 hour until the absolute vacuum is 10KPa to further remove the residual monomer, and then add lithium hydroxide monohydrate for neutralization until the pH is reached. The value is 7.5, add deionized water to dilute it to obtain a light yellow glue, pass the glue through a 150 mesh sieve, and use a super strong magnetic rod demagnetizer to demagnetize to obtain the target product (water-based binder), which is a water-based binder. The solid content is 10.4% and the viscosity is 21500cps.

Example 2

The water-based adhesive provided in this embodiment includes a polymer with the following structure:

Among them, a:b:c:d=40:30:10:20.

The preparation method of the water-based adhesive provided in this embodiment includes the following steps:

Add 400g of deionized water to the reaction kettle at room temperature, then add 0.4 mol of acrylamide, 0.3 mol of acrylic acid, 0.1 mol of vinyl glycol ether and 0.2 mol of methacrylonitrile in order, stir and disperse, and stir at a speed of 200 rpm. Introduce nitrogen (nitrogen flow rate 2L/h) for 1 hour to remove oxygen in the solution system (mixed solution), then heat up to 60°C, add 0.0015 mol of initiator ammonium persulfate after the temperature stabilizes, and proceed. Polymerization reaction, react for 5 hours; adjust the temperature to 80°C, then add 0.001 mol of redox initiator ammonium persulfate and 0.001 mol of sodium bisulfite, conduct polymerization reaction, and react for 2 hours to remove residual monomers. After the reaction is completed, Evacuate for 1 hour to an absolute vacuum of 8KPa to further remove residual monomers. Then add lithium hydroxide monohydrate to neutralize until the pH value is 7.6. Add deionized water to dilute to obtain a light yellow glue. Pass the liquid through a 150 mesh sieve and use a super strong magnetic rod to demagnetize it. The device was used for demagnetization to obtain the target product (water-based binder). The solid content of the water-based binder was 10.2% and the viscosity was 14600 cps.

Example 3

The water-based adhesive provided in this embodiment includes a polymer with the following structure:

Among them, a:c:d=60:20:20.

The preparation method of the water-based adhesive provided in this embodiment includes the following steps:

Add 300g deionized water to the reaction kettle at room temperature, then add 0.6 mol of acrylamide, 0.2 mol of vinyl diethylene glycol ether and 0.2 mol of acrylonitrile in order, stir and disperse, the stirring speed is 400 rpm, and nitrogen gas (nitrogen flow rate 2L/h), the nitrogen gas is introduced for 1 hour to remove the oxygen in the solution system (mixed solution), and then the temperature is raised to 50°C. After the temperature stabilizes, 0.001 mol of potassium persulfate as the initiator is added to carry out the polymerization reaction for 7 hours. ; Adjust the temperature to 80°C, then add 0.001 mol of redox initiator ammonium persulfate and 0.001 mol of sodium bisulfite to perform a polymerization reaction for 2 hours to remove residual monomers. After the reaction is completed, vacuum for 1 hour. to an absolute vacuum of 12KPa to further remove residual monomers, and then add lithium hydroxide monohydrate to neutralize until the pH value is 7.7. Add deionized water to dilute to obtain a light yellow glue liquid, which is passed through a 150-mesh sieve. , use a super strong magnetic rod demagnetizer to perform demagnetization, and obtain the target product (water-based binder). The solid content of the water-based binder is 10.2% and the viscosity is 17000cps.

Example 4

The water-based adhesive provided in this embodiment includes a polymer with the following structure:

Among them, a:b:c:d=30:20:40:10.

The preparation method of the water-based binder provided in this embodiment comprises the following steps:

Add 400g of deionized water to the reaction kettle at room temperature, then add 0.3 mol of acrylamide, 0.2 mol of methacrylic acid, 0.4 mol of vinyl glycol ether and 0.1 mol of acrylonitrile in order, and stir to disperse. The stirring speed is 200 rpm. Introduce nitrogen (nitrogen flow rate 2L/h) for 1 hour to remove oxygen in the solution system (mixed solution). Then heat up to 50°C. After the temperature stabilizes, add 0.001 mol of potassium persulfate as the initiator. Polymerization reaction, react for 7 hours; adjust the temperature to 80°C, then add 0.001 mol of redox initiator ammonium persulfate and 0.001 mol of sodium bisulfite, conduct polymerization reaction, and react for 2 hours to remove residual monomers. After the reaction is completed , vacuum for 1 hour to an absolute vacuum of 15KPa to further remove the residual monomer, then add lithium hydroxide monohydrate for neutralization until the pH value is 7.7, add deionized water to dilute, and obtain a light yellow glue liquid. The liquid passes through a 150-mesh sieve and is demagnetized using a super-strong magnetic bar demagnetizer to obtain the target product (water-based binder). The solid content of the water-based binder is 10.1% and the viscosity is 18,000 cps.

Example 5

The water-based adhesive provided in this embodiment includes a polymer with the following structure:

Among them, a:b:c:d=30:20:20:30.

The preparation method of the water-based adhesive provided in this embodiment includes the following steps:

Add 450g of deionized water to the reaction kettle at room temperature, then add 0.3 mol of acrylamide, 0.2 mol of methacrylic acid, 0.2 mol of vinyl diethylene glycol ether and 0.3 mol of acrylonitrile in order, stir and disperse, and the stirring speed is 300 rpm. Pour in nitrogen (nitrogen flow rate 2L/h) for 1 hour to remove oxygen in the solution system (mixed solution), then raise the temperature to 50°C. After the temperature stabilizes, add 0.005 mol of potassium persulfate as the initiator. Carry out polymerization reaction and react for 7 hours; adjust the temperature to 80°C, then add 0.001 mol of redox initiator ammonium persulfate and 0.001 mol of sodium bisulfite, conduct polymerization reaction, and react for 2 hours to remove residual monomers. The reaction is completed. Then, vacuum for 1 hour to an absolute vacuum of 9KPa to further remove the residual monomer. Then add lithium hydroxide monohydrate to neutralize until the pH value is 7.5. Add deionized water to dilute to obtain a light yellow glue solution. The glue solution was passed through a 150-mesh sieve and demagnetized using a super-strong magnetic bar demagnetizer to obtain the target product (water-based binder). The solid content of the water-based binder was 10.1% and the viscosity was 9000 cps.

Example 6

The water-based adhesive provided in this embodiment includes a polymer with the following structure:

Among them, a:b:c:d=40:30:15:15.

The preparation method provided in this example is basically the same as that in Example 1, except that acrylamide is replaced by methacrylamide, and the solid content of the prepared water-based adhesive is 10.2% and the viscosity is 12,000 cps.

Example 7

The water-based adhesive provided in this embodiment includes a polymer with the following structure:

Among them, a:b:c:d=50:10:30:10.

The preparation method provided in this example is basically the same as that in Example 1, except that 0.4 mol of acrylamide is replaced by 0.5 mol of the monomer corresponding to monomer unit a, 0.3 mol of acrylic acid is replaced by 0.1 mol of ethylacrylic acid, and 0.15 mol vinyl glycol ether replaced with 0.3 mol vinyl propylene glycol Ether, replace 0.15 mol of acrylonitrile with 0.1 mol of the monomer corresponding to monomer unit d. The solid content of the prepared water-based adhesive is 9.5% and the viscosity is 13100 cps.

Example 8

The water-based adhesive provided in this embodiment includes a polymer with the following structure:

Among them, a:b:c:d=40:30:15:15.

The preparation method of the water-based adhesive provided in this embodiment includes the following steps:

Add 400g of deionized water to the reaction kettle at room temperature, then add 0.4 mol of N-isopropylacrylamide, 0.3 mol of isopropylacrylic acid, 0.15 mol of vinyl glycol ether and 0.15 mol of acrylonitrile in order, and stir to disperse. The stirring speed is 400rpm, nitrogen gas is introduced (nitrogen flow rate is 2L/h), the nitrogen gas is introduced for 1 hour to remove the oxygen in the solution system (mixed solution), and then the temperature is raised to 70°C. After the temperature is stable, the initiator is added Potassium persulfate 0.001mol, polymerization reaction, reaction 6h; adjust the temperature to 90°C, then add redox initiator ammonium persulfate 0.001mol and sodium bisulfite 0.001mol, polymerization reaction, reaction 1.5h, in order to divide Remove the residual monomer. After the reaction is completed, vacuum for 1 hour to an absolute vacuum of 30KPa to further remove the residual monomer. Then add sodium hydroxide monohydrate for neutralization until the pH value is 7.5, and add deionized water to dilute , obtain light yellow glue liquid, pass the glue liquid through 250 mesh Sieve and use a super strong magnetic rod demagnetizer to perform demagnetization to obtain the target product (water-based binder). The solid content of the water-based binder is 10.5% and the viscosity is 23000 cps.

Example 9

The water-based adhesive provided in this embodiment includes a polymer with the following structure:

Among them, a:b:c:d=30:20:40:10.

The preparation method provided in this example is basically the same as that in Example 1, except that 0.4 mol acrylamide is replaced by 0.3 mol N, N-dimethylacrylamide, and 0.3 mol acrylic acid is replaced by 0.2 mol methacrylic acid. Replace 0.15 mol of vinyl glycol ether with 0.4 mol of vinyl triethylene glycol ether, and replace 0.15 mol of acrylonitrile with 0.1 mol of the monomer corresponding to monomer unit d. The solid content of the prepared water-based binder is 10%, viscosity is 16800cps.

Example 10

The water-based adhesive provided in this embodiment includes a polymer with the following structure:

Among them, a:b:c:d=45:33:17:5.

The preparation method provided in this example is basically the same as that in Example 1, except that 0.4 mol acrylamide is replaced with 0.45 mol acrylamide, 0.3 mol acrylic acid is replaced with 0.33 mol acrylic acid, and 0.15 mol vinyl glycol ether is replaced. Replaced with 0.17 mol of vinyl glycol ether and 0.15 mol of acrylonitrile with 0.05 mol of acrylonitrile. The solid content of the prepared water-based adhesive was 10% and the viscosity was 17900 cps.

Comparative example 1

Commercially available styrene-butadiene rubber SBR from a certain company was used as the binder, and sodium carboxymethylcellulose (CMC) with a mass ratio of 1:1 was used.

Comparative example 2

The acrylic resin PAA commercially available from a certain company was used as the binder.

Comparative example 3

The water-based binder provided in this comparative example has the structure shown below:

Among them, a:b:d=47:35:18.

The preparation method provided in this comparative example is basically the same as that in Example 1, except that no vinyl glycol ether is added, and 0.47 mol of acrylamide, 0.35 mol of acrylic acid, and 0.18 mol of acrylonitrile are added.

Comparative example 4

The water-based binder provided in this comparative example includes a polymer with the following structure:

Among them, a:b:c=47:35:18.

The preparation method provided in this comparative example is basically the same as that in Example 1, except that acrylonitrile is not added, and 0.47 mol of acrylamide, 0.35 mol of acrylic acid, and 0.18 mol of vinyl glycol ether are added.

Comparative example 5

The preparation method provided in this comparative example is basically the same as that in Example 1. The difference is that "redox initiator ammonium persulfate 0.001 mol and sodium bisulfite 0.001 mol" are replaced by "potassium persulfate 0.002 mol". Add redox initiators ammonium persulfate and sodium bisulfite.

Performance Testing

The binders prepared in Examples 1-9 and Comparative Examples 1-5 are used as silicon negative electrode material binders to prepare negative electrode plates. The method is as follows:

Silicon-carbon composite materials (using silicon-based/graphite composite negative electrode materials with a gram capacity of 600mAh/g), Conductive carbon black, single-walled carbon nanotubes and the binder prepared in the examples or comparative examples (take the water-based binder prepared in the examples or comparative examples, where the quality of the solids in the water-based binder is different from that of the silicon-carbon composite material The mass ratio of the silicon-carbon composite material, conductive carbon black, single-walled carbon nanotubes and the binder prepared in the embodiment or comparative example (based on the mass of the solid in the binder) is mixed. The ratio is 93.0:0.5:0.25:6.25. Add an appropriate amount of deionized water according to the total solid content of 35% to make the battery electrode slurry. The uniformly dispersed slurry is passed through a 100-mesh screen, and then coated on a 10 μm thick copper foil as a current collector. After drying at 120°C for 5 minutes, it is obtained by rolling at room temperature with a unit length load of 10×10 ⁴ N/m. Negative pole piece.

A 425060P lithium-ion battery is made with nickel cobalt manganese oxide NCM622 as the positive electrode, a mixed solvent of ethylene carbonate EC: ethyl methyl carbonate EMC: diethyl carbonate DEC in a mass ratio of 3:2:5, containing 1M LiPF6, as the electrolyte, and the existing PP material as the diaphragm.

The performance measurement method is as follows:

Measurement of peel strength: Cut the negative electrode sheet made of the adhesive prepared in the Examples and Comparative Examples into strips of 10 cm A transparent tape is attached to the layer side, peeled off in the 180° direction using a tensile testing machine at a speed of 100mm/min, and the peeling stress is measured.

Determine the flexibility of the pole piece: Place a mandrel with a diameter of Φ = 3mm on the current collector side of the rolled pole piece made from the adhesive prepared in the Examples and Comparative Examples, and conduct a bending experiment. Observe this time through an optical microscope. Regarding the status of the pole piece, if the pole piece is intact, it is marked as ○, and if the pole piece is peeled off or cracked, it is marked as ×.

Determination of the first battery effect: charge and discharge at 0.33C at 25℃, in the voltage range of 2.5~4.2V Cycle, use the constant current method to test the first Coulombic efficiency of the charge and discharge cycle;

Determination of full-charge expansion: At 25°C, in the voltage range of 2.5 to 4.2V, charge and discharge at 0.33C for two cycles, then fully charge, disassemble the battery, and test the thickness of the negative electrode sheet d ₂ , assuming the original thickness of the electrode sheet to be d ₁ , then the full electrical expansion rate is: (d ₂ -d ₁ )/d ₁ ×100%.

Determine the capacity retention rate of 300 cycles: At 25°C, in the voltage range of 2.5 to 4.2V, charge at 0.5C and discharge at 1.0C for charge and discharge cycles. Use the constant current method to test the capacity retention rate after 300 cycles. Capacity retention Rate = 300th cycle discharge gram capacity/1st cycle discharge gram capacity.

The test results are shown in Table 1 and Table 2.

Table 1

Table 2

As can be seen from Tables 1 and 2, compared to commercially available SBR (Comparative Example 1), the adhesives provided in Examples 1-10 have excellent peel strength, first effect, full-charge expansion and cycle retention rate. Significant improvements; compared to commercially available PAA adhesives (Comparative Example 2), the adhesives provided in Examples 1-10 have improved peel strength, pole piece flexibility, first effect, full charge expansion and cycle retention rate. There is also a significant improvement, which shows that the water-based binder provided by the present invention has excellent bonding properties and can significantly inhibit the expansion of the silicon negative electrode. At the same time, the prepared pole piece has excellent flexibility and improves the cycle performance of the battery. .

Compared with Example 1, the content of the acrylonitrile monomer described in Example 10 is reduced, and the corresponding expansion inhibition ability is reduced.

Compared with Example 1, in Comparative Example 3, no vinyl glycol ether was added during the preparation process of the binder, resulting in poor flexibility of the pole piece and a significant decrease in cycle performance.

Compared with Example 1, in Comparative Example 4, acrylonitrile was not added during the preparation process of the binder, which resulted in a decrease in the peel strength of the pole piece and its ability to suppress expansion at full power.

Compared with Example 1, in Comparative Example 5, the redox initiators ammonium persulfate and sodium bisulfite were not added during the preparation process of the binder, resulting in a decrease in the peel strength, first effect and cycle performance of the pole piece.

Obviously, the above-mentioned embodiments are only examples for clear explanation and are not intended to limit the implementation. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. An exhaustive list of all implementations is neither necessary nor possible. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims (10)

1. A kind of water-based adhesive, characterized in that the water-based adhesive includes a polymer containing at least three monomer units, and the polymer includes a first monomer unit, a second monomer unit and a third monomer. Unit, the first monomer unit has a structure represented by formula I, the second monomer unit has a structure represented by formula II, and the third monomer unit has a structure represented by formula III,
   

   Among them, R ₁ , R ₂ , R ₃ and R ₆ are the same or different, and each independently represents hydrogen, a linear alkyl group or a branched alkyl group; R ₅ is a group containing a hydroxyl group at the end group.
2. The water-based adhesive according to claim 1, wherein R ₅ represents a straight-chain alkyl group with a carbon number of 1-6 substituted by a hydroxyl group, and a straight-chain alkyl group with a carbon number of 1-6 substituted by a hydroxyl group. Branched alkyl, -CH ₂ CH ₂ OCH ₂ CH ₂ OH or -(CH ₂ CH ₂ O) _n H, n≥3;

   And/or, the R ₁ , R ₂ , R ₃ and the R ₆ are the same or different, and each independently represents hydrogen, a straight-chain alkyl group with a carbon number of 1-6, or a straight-chain alkyl group with a carbon number of 1-6. of branched alkyl groups.
3. The water-based binder according to claim 1, wherein R ₅ represents -CH ₂ CH ₂ OH, CH ₂ CH ₂ CH ₂ OH, -CH ₂ CH ₂ OCH ₂ CH ₂ OH or -(CH ₂ CH ₂ O) _n H, n≥3; the R ₁ represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH(CH ₃ ) ₂ ; the R ₂ represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH(CH ₃ ) ₂ ; the R ₃ represents hydrogen, methyl, ethyl, propyl, -CH(CH ₃ ) ₂ , -CH ₂ CH ₂ CH ₂ CH ₃ or -CH ₂ CH(CH ₃ ) ₂ ; the R ₆ represents hydrogen, methyl, ethyl or -CH(CH ₃ ) ₂ .
4. The water-based adhesive according to any one of claims 1 to 3, characterized in that the polymer further includes a fourth monomer unit, and the fourth monomer unit has a structure represented by Formula IV:
   

   Among them, R ₄ represents hydrogen, linear alkyl or branched alkyl; M represents H, Li, Na or K.
5. The water-based adhesive according to claim 4, wherein _R4 represents hydrogen, a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 1 to 6 carbon atoms;

   And/or, the solid content of the water-based binder is 9.5-10.5%, and the viscosity is 8000-30000cps;

   And/or, the polymer has the structure shown in formula V:
   

   Wherein, the definitions of M, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are the same as the definitions of M, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ in claim 4, a:b:c:d=(30～80):(0～50):(5～50):(5-30).
6. The water-based adhesive according to claim 5, characterized in that, based on the total mole number of monomer units corresponding to a, b, c, and d being 100%, the mole percentage of the monomer unit corresponding to d is 10%. ~30%.
7. A method for preparing the aqueous adhesive according to any one of claims 1 to 6, characterized in that it includes the following steps:

   Under the action of an initiator, polymer monomers undergo a polymerization reaction in a reaction solvent to obtain the water-based binder, wherein the polymer monomers include acrylamide monomers, vinyl ether monomers and acrylonitrile. Class singleton.
8. The method for preparing a water-based adhesive according to claim 7, wherein the polymer monomer further includes an acrylic monomer, and the acrylamide monomer, acrylic monomer, vinyl ether monomer The molar ratio of the monomer to the acrylonitrile monomer is (30~80):(0~50):(5~50):(5-30);

   And/or, the polymer monomer undergoes a polymerization reaction in a reaction solvent under the action of an initiator to obtain the water-based binder, which includes the following steps:

   S1. Add the polymer monomer into the reaction solvent, stir and disperse, and obtain a mixed solution;

   S2. Add the first initiator to the mixed solution to perform the first polymerization reaction, and then add the second initiator to perform the second polymerization reaction. After the reaction is completed, perform vacuuming, alkali neutralization, sieving, and removal. Magnetize to obtain the aqueous binder, wherein the molar ratio of the first initiator to the second initiator is (0.5-3):1, and the first initiator includes sodium persulfate, persulfate At least one of potassium and ammonium persulfate, the second initiator is a redox initiator, including ammonium persulfate/sulfite At least one of sodium acid, ammonium persulfate/sodium bisulfite, hydrogen peroxide/ferrous ion.
9. The preparation method of aqueous binder according to claim 8, characterized in that the temperature of the first polymerization reaction is 40°C to 80°C and the time is 3 to 10h; the temperature of the second polymerization reaction is 70 ℃ ~ 90 ℃, time is 1-3h.
10. The use of a water-based binder according to any one of claims 1-6 or a water-based binder prepared by the preparation method of a water-based binder according to any one of claims 7-9, It is characterized in that the aqueous binder is used for the preparation of lithium ion batteries.