A strong adhesion type adhesive, its preparation method and application

Abstract

The present invention provides a strongly adhesive binder, a preparation method thereof and an application thereof, relating to the technical field of lithium-ion batteries. In the present invention, poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) and poly(acrylic acid-co-hydroxyethyl acrylate) are prepared, and these two polymers are crosslinked to obtain a strongly adhesive binder. The binder prepared in the present invention has strong adhesion. When applied to the silicon-based anode of a lithium-ion battery, it can effectively solve the problem of adhesion between silicon-based anode particles under large-volume expansion in the prior art. Even when applied to thick electrodes or high-loading Si electrodes, the binder prepared in the present invention still has good adhesion and can effectively maintain the integrity of the electrode structure and the conductive network. Moreover, the binder prepared in the present invention can improve the processability of the electrode sheet. In addition, the preparation method provided by the present invention has a simple process, is easy to operate and is suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and particularly to a strongly adhesive binder and its preparation method and application. Background Art

[0002] Lithium ion batteries are widely used in energy storage of electric vehicles, 3C products, renewable energy and smart grids due to a series of advantages such as high energy density, high working voltage, high output power, small self-discharge effect and environmental protection, and are gradually expanding to high-power systems and fields. With the booming development of new industries such as high-end communication and electric vehicles, in order to overcome the "range anxiety" of electric vehicles and the "low battery anxiety" of consumer electronics products, it is required that lithium ion batteries have higher energy density. Silicon (Si) is considered to be one of the most promising alternatives to graphite anodes due to its high theoretical specific capacity (4200 mAh / g), low lithium insertion potential (~0.4V vs Li / Li + ) low, rich reserves and low cost, etc. However, the drastic volume change of silicon particles during the lithiation / delithiation process leads to electrode particle displacement, electrical connection failure and the formation of an unstable SEI (solid electrolyte interface film), resulting in rapid attenuation of battery capacity. Developing high-performance polymer binders is one of the most effective methods to solve the above problems.

[0003] Based on the chemical bonding theory in the bonding mechanism, natural polysaccharides (such as NaCMC, Alginate) and synthetic polymers (PAA, PVA) containing rich polar groups can generate strong adhesion with Si particles through hydrogen bonding, but the adhesion of this type of binder still has certain limitations. Especially in high-quality loaded Si electrodes (i.e., thick electrodes), the adhesion provided by this type of polymer can no longer maintain the integrity of the electrode structure during the continuous large volume change process. In addition, this type of binder is not compatible with currently commercialized silicon-based anodes. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a strongly adhesive binder and its preparation method and application. The binder prepared by the present invention has strong adhesion, and can effectively maintain the integrity of the electrode structure and conductive network even when used in high-quality loaded silicon-based electrodes.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a strongly adhesive binder, comprising the following steps:

[0007] Mix acrylic acid, γ-methacryloxypropyltrimethoxysilane, water and a first initiator to carry out a first polymerization reaction to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0008] Mix acrylic acid, 2-hydroxyethyl acrylate, water and a second initiator to carry out a second polymerization reaction to obtain a poly(acrylic acid-co-2-hydroxyethyl acrylate) solution;

[0009] Mix the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution and the poly(acrylic acid-co-2-hydroxyethyl acrylate) solution to carry out a physical cross-linking reaction to obtain the strong adhesion type adhesive.

[0010] Preferably, the molar ratio of acrylic acid to γ-methacryloxypropyltrimethoxysilane is (9.9~8):(0.1~2); the mass of the first initiator is 0.05~0.15% of the sum of the masses of acrylic acid and γ-methacryloxypropyltrimethoxysilane; the total mass concentration of acrylic acid and γ-methacryloxypropyltrimethoxysilane in water is 8~10%.

[0011] Preferably, the molar ratio of acrylic acid to 2-hydroxyethyl acrylate is (9~5):(1~5); the mass of the second initiator is 0.05~0.2% of the sum of the masses of acrylic acid and 2-hydroxyethyl acrylate; the total mass concentration of acrylic acid and 2-hydroxyethyl acrylate in water is 8~10%.

[0012] Preferably, the first initiator and the second initiator independently include one or more of azobisisobutyronitrile, azobis(isobutyramidine) dihydrochloride, azoisovaleronitrile, ammonium persulfate, sodium bisulfite and potassium persulfate.

[0013] Preferably, both the first polymerization reaction and the second polymerization reaction include a first reaction stage and a second reaction stage carried out in sequence. The temperature of the first reaction stage is 35~40°C, and the heat preservation time is 3~5 h. The temperature of the second reaction stage is 50~60°C, and the heat preservation time is 4~6 h.

[0014] Preferably, the mass ratio of the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution to the poly(acrylic acid-co-2-hydroxyethyl acrylate) solution is (1~2):1.

[0015] Preferably, the temperature of the physical cross-linking reaction is 25~30°C, and the heat preservation time is 2~4 h.

[0016] The present invention provides a strong adhesion type adhesive prepared by the preparation method described in the above technical solution. The active ingredient of the adhesive is a physical cross-linking product of poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) and poly(acrylic acid-co-2-hydroxyethyl acrylate).

[0017] The present invention provides the application of the strong adhesion type adhesive described in the above technical solution as an adhesive for the silicon-based negative electrode of a lithium-ion battery.

[0018] The present invention also provides a silicon-based negative electrode slurry for a lithium-ion battery, which includes a silicon-based active material, a conductive additive, and an adhesive, and the adhesive is the strong adhesion type adhesive described in the above technical solution.

[0019] The present invention provides a preparation method of a strong adhesion type adhesive, which includes the following steps: mixing acrylic acid, γ-methacryloxypropyltrimethoxysilane, water, and a first initiator to carry out a first polymerization reaction to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution; mixing acrylic acid, hydroxyethyl acrylate, water, and a second initiator to carry out a second polymerization reaction to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution; mixing the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution and the poly(acrylic acid-co-hydroxyethyl acrylate) solution to carry out a physical crosslinking reaction to obtain the strong adhesion type adhesive. The present invention prepares poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) and poly(acrylic acid-co-hydroxyethyl acrylate), and physically crosslinks these two polymers to obtain a strong adhesion type adhesive. Compared with the prior art, the present invention has the following beneficial effects:

[0020] In the adhesive system of the present invention, carboxyl groups, hydroxyl groups, and silanols formed by the hydrolysis and condensation of silanes are introduced through poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) and poly(acrylic acid-co-hydroxyethyl acrylate), enhancing the binding force between the active material particles of the silicon-based negative electrode of the lithium-ion battery and between the active material particles and the current collector; at the same time, the SiO2 nano crosslinking points formed by the hydrolysis and condensation of silanols can effectively improve the adhesion of the polymer adhesive by enhancing the cohesion between polymer segments;

[0021] Moreover, when the volume of the active particles of the silicon-based negative electrode of the lithium-ion battery changes, the multiple dynamic hydrogen bonds constructed between the carboxyl groups and hydroxyl groups in the adhesive system start to gradually dissociate under stress, and the dissociation of the hydrogen bonds can effectively dissipate the extrusion stress generated during the volume expansion of the active particles, thereby stabilizing the structure on the surface of the negative electrode material and repairing the damaged interface layer, improving the electrochemical stability of the battery;

[0022] In addition, the introduction of the polyacrylate hydroxyethyl ester segment increases the flexibility of the polymer, thereby improving the processability of the electrode sheet.

[0023] Therefore, the adhesive prepared by the present invention has strong adhesion, which can enhance the adhesion during the dynamic volume change of the anode material particles. When applied to the silicon-based anode of a lithium-ion battery, it can effectively solve the problem of adhesion between silicon-based anode particles under large volume expansion. Even when applied to a thick electrode with a high mass load, the adhesive prepared by the present invention still has good adhesion and can effectively maintain the integrity of the electrode structure and the conductive network. Moreover, the preparation method provided by the present invention has a simple process, is easy to operate, and is suitable for large-scale production. The results of the examples show that when the adhesive prepared by the present invention is used for the silicon-based anode of a lithium-ion battery, the areal loading of the electrode is 8-9 mg / cm 2 (thick electrode), and the first-cycle Coulombic efficiency of the half-cell assembled with this anode reaches more than 85% when the capacity of the electrode reaches 3.5 mAh / cm 2 , and the capacity retention rate after 150 cycles is more than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the linear sweep voltammetry curve of the Cu|Li battery with the adhesive A1 in Example 1 under the condition of 0.1 mV·s -1 ;

[0025] Figure 2 is the comparison chart of the cycling performance of the lithium-ion half-cells with the adhesive A1 in Example 1 and the adhesive B1 in Comparative Example 1;

[0026] Figure 3 is the cycling performance chart of the lithium-ion soft-pack battery with the adhesive A1 in Example 1;

[0027] Figure 4 is the comparison chart of the peel strength of the lithium-ion battery anode electrode sheets of adhesives A1, A2, and A3. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention provides a method for preparing a strongly adhesive adhesive, which includes the following steps:

[0029] Mix acrylic acid, γ-methacryloxypropyltrimethoxysilane, water, and a first initiator to carry out a first polymerization reaction to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0030] Mix acrylic acid, hydroxyethyl acrylate, water, and a second initiator to carry out a second polymerization reaction to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0031] Mix the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution and the poly(acrylic acid-co-hydroxyethyl acrylate) solution to carry out a physical cross-linking reaction to obtain the strongly adhesive adhesive.

[0032] In the present invention, unless otherwise specified, the raw materials involved are commercially available products well-known to those skilled in the art.

[0033] In the present invention, acrylic acid, γ-methacryloxypropyltrimethoxysilane, water and a first initiator are mixed to carry out a first polymerization reaction to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution. In the present invention, the molar ratio of acrylic acid to γ-methacryloxypropyltrimethoxysilane is preferably (9.9 - 8):(0.1 - 2), more preferably (9.9 - 9):(0.1 - 1); the water is preferably deionized water, and the total mass concentration of acrylic acid and γ-methacryloxypropyltrimethoxysilane in water is preferably 8 - 10%, more preferably 10%. In the present invention, the first initiator preferably includes one or more of azobisisobutyronitrile, azobis(2-methylpropionamidine) dihydrochloride, azobisisovaleronitrile, ammonium persulfate, sodium bisulfite and potassium persulfate, more preferably a mixture of sodium bisulfite and potassium persulfate or a mixture of azobis(2-methylpropionamidine) dihydrochloride and potassium persulfate. The mass ratio of sodium bisulfite to potassium persulfate in the mixture of sodium bisulfite and potassium persulfate is preferably 1:2, and the mass ratio of azobis(2-methylpropionamidine) dihydrochloride to potassium persulfate in the mixture of azobis(2-methylpropionamidine) dihydrochloride and potassium persulfate is preferably 2:1; the mass of the first initiator is preferably 0.05 - 0.15% of the sum of the masses of acrylic acid and γ-methacryloxypropyltrimethoxysilane, more preferably 0.05 - 0.1%. In the present invention, the method of mixing acrylic acid, γ-methacryloxypropyltrimethoxysilane, water and the first initiator is preferably: dissolving acrylic acid and γ-methacryloxypropyltrimethoxysilane in water to obtain a mixed aqueous solution; adding the first initiator to the mixed aqueous solution, and then introducing a protective gas into the obtained mixed system. In the present invention, the protective gas is preferably argon or nitrogen, and the introduction time of the protective gas is preferably 40 min; in the present invention, oxygen in the reaction system is removed by introducing the protective gas to prevent the inhibitory effect of oxygen on the polymerization reaction. In the present invention, the first polymerization reaction preferably includes a first reaction stage and a second reaction stage carried out in sequence; the temperature of the first reaction stage is preferably 35 - 40°C, more preferably 38 - 40°C, and the heat preservation time is preferably 3 - 5 h, more preferably 3.5 - 4.5 h; the temperature of the second reaction stage is preferably 50 - 60°C, more preferably 55 - 58°C, and the heat preservation time is preferably 4 - 6 h, more preferably 4.5 - 5.5 h; the present invention has no special requirements for the heating rate of raising the temperature from the temperature of the first reaction stage to the temperature of the second reaction stage. The present invention uses gradient heating for the polymerization reaction, and gradient heating will affect the reaction rate, thereby regulating properties such as the molecular weight and viscosity of the polymer. In the present invention, the reaction formula A of the first polymerization reaction is as follows.

[0034] After the first polymerization reaction, no post-treatment is required.

[0035]

[0036] In the present invention, acrylic acid, hydroxyethyl acrylate, water and a second initiator are mixed to carry out a second polymerization reaction to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution. In the present invention, the molar ratio of the acrylic acid to the hydroxyethyl acrylate is preferably (9 - 5):(1 - 5), more preferably (9 - 8):(1.5 - 5); the water is preferably deionized water, and the total mass concentration of the acrylic acid and the hydroxyethyl acrylate in the water is preferably 8 - 10%, more preferably 10%. In the present invention, the second initiator preferably includes one or more of azobisisobutyronitrile, azobis(2-methylpropionamidine) dihydrochloride, azobisisovaleronitrile, ammonium persulfate, sodium bisulfite and potassium persulfate, more preferably a mixture of sodium bisulfite and potassium persulfate or a mixture of azobis(2-methylpropionamidine) dihydrochloride and potassium persulfate. The mass ratio of sodium bisulfite to potassium persulfate in the mixture of sodium bisulfite and potassium persulfate is preferably 1:2, and the mass ratio of azobis(2-methylpropionamidine) dihydrochloride to potassium persulfate in the mixture of azobis(2-methylpropionamidine) dihydrochloride and potassium persulfate is 2:1; the mass of the second initiator is preferably 0.05 - 0.2% of the sum of the masses of the acrylic acid and the hydroxyethyl acrylate, more preferably 0.05 - 0.1%. In the present invention, the method for mixing the acrylic acid, the hydroxyethyl acrylate, the water and the second initiator is preferably: dissolving the acrylic acid and the hydroxyethyl acrylate in water to obtain a mixed aqueous solution; adding the second initiator to the mixed aqueous solution, and then introducing a protective gas into the obtained mixed system; the conditions and functions for introducing the protective gas are the same as those in the above technical solution and will not be elaborated here. In the present invention, the second polymerization reaction preferably includes a first reaction stage and a second reaction stage carried out in sequence, that is, the present invention uses gradient temperature rise for the polymerization reaction; the temperature of the first reaction stage is preferably 35 - 40°C, more preferably 38 - 40°C, and the heat preservation time is preferably 3 - 5 h, more preferably 3.5 - 4.5 h; the temperature of the second reaction stage is preferably 50 - 60°C, more preferably 55 - 58°C, and the heat preservation time is preferably 4 - 6 h, more preferably 4.5 - 5.5 h; the present invention has no special requirements for the heating rate from the temperature of the first reaction stage to the temperature of the second reaction stage. In the present invention, the reaction formula of the second polymerization reaction is shown as formula B. After the second polymerization reaction, no post-treatment is required.

[0037]

[0038] After obtaining the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution and the poly(acrylic acid-co-2-hydroxyethyl acrylate) solution, the present invention mixes the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution and the poly(acrylic acid-co-2-hydroxyethyl acrylate) solution to carry out a physical crosslinking reaction to obtain the strong adhesion type adhesive. In the present invention, the mass ratio of the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution to the poly(acrylic acid-co-2-hydroxyethyl acrylate) solution is preferably (1-2):1, more preferably 1:1; the present invention preferably adds the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution to the poly(acrylic acid-co-2-hydroxyethyl acrylate) solution. In the present invention, the temperature of the physical crosslinking reaction is preferably 25-30°C. In the examples of the present invention, the physical crosslinking reaction is carried out at room temperature (25°C), the heat preservation time of the physical crosslinking reaction is preferably 2-4 h, more preferably 4 h; the physical crosslinking reaction is preferably carried out under stirring conditions.

[0039] The present invention provides a strong adhesion type adhesive prepared by the preparation method described in the above technical solution, and the active ingredient of the adhesive is a physical crosslinking product of poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) and poly(acrylic acid-co-2-hydroxyethyl acrylate).

[0040] The present invention provides an application of the strong adhesion type adhesive described in the above technical solution as an adhesive for a silicon-based negative electrode of a lithium-ion battery. The strong adhesion type adhesive provided by the present invention is an adhesive for a silicon-based negative electrode of a lithium-ion battery, and has a strong binding force with each component in the silicon-based negative electrode of the lithium-ion battery. The adhesive enhances the binding force between the negative electrode active material particles and between the active material particles and the current collector through carboxyl groups, hydroxyl groups and silanols formed by hydrolysis and condensation; multiple dynamic hydrogen bonds are also constructed between the carboxyl groups and hydroxyl groups in the binder. When the volume of the silicon-based active material changes, the multiple dynamic bonds in the adhesive begin to gradually dissociate after being stressed, and the dissociation of the hydrogen bonds can effectively dissipate the stress generated when the active particles expand in volume, thereby stabilizing the surface structure of the negative electrode material and repairing the damaged interface layer, improving the electrochemical stability of the battery; by introducing a poly(2-hydroxyethyl acrylate) chain segment, the flexibility of the electrode sheet is improved, and then the structural integrity of the negative electrode is maintained, effectively improving the electrochemical stability of the battery. When the negative electrode of the lithium-ion battery uses the adhesive provided by the present invention, after 500 cycles of the soft-pack battery, the capacity retention rate is still above 80%, and it has high cycle stability. The adhesive provided by the present invention can enable the silicon-based negative electrode to maintain good stability and excellent adhesion at a high loading (3.5 mAh / cm in the examples of the present invention 2 ) still maintains good stability and excellent adhesion.

[0041] The present invention also provides a silicon-based anode slurry for lithium-ion batteries, which includes a silicon-based active material, a conductive additive, and a binder. The binder is the strong adhesion type binder described in the above technical solution. In the present invention, the silicon-based active material preferably includes one or more of silicon, silicon-carbon, and silicon-oxygen materials; the conductive additive preferably includes one or more of SuperP, acetylene black, and Ketjen black; the mass ratio of the silicon-based active material, the conductive additive, and the binder is preferably (92-95):(2-1):(6-4), more preferably 95:1:4. In the present invention, the use method of the silicon-based anode slurry for lithium-ion batteries is preferably as follows: the silicon-based active material, the conductive additive, and the binder are uniformly dispersed in water by ball milling to obtain a slurry; the obtained slurry is coated on a current collector (such as a copper foil), and then dried to obtain a lithium-ion battery anode electrode sheet. In the present invention, the thickness of the coating is preferably 220-300 microns.

[0042] The following examples are used to illustrate in detail the strong adhesion type binder provided by the present invention, its preparation method and application, but they should not be construed as limiting the protection scope of the present invention.

[0043] Comparative Example 1

[0044] A commercially available CMC / SBR (i.e., sodium carboxymethyl cellulose / styrene-butadiene rubber, the mass ratio of CMC to SBR is 2:3) is used as binder B1.

[0045] Example 1

[0046] A strong adhesion type binder, the preparation method is as follows:

[0047] (1) Take 3.8 g of acrylic acid and 0.2 g of γ-methacryloxypropyltrimethoxysilane and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 55 °C, and the holding time is 4 h and 4 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0048] (2) Take 2 g of acrylic acid and 2 g of hydroxyethyl acrylate and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the solution system from 40 °C to 55 °C, and the holding time is 4 h and 4 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0049] (3) Add 4 g of poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution to 4 g of poly(acrylic acid - co - hydroxyethyl acrylate) solution and stir for 4 h to obtain a clear poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) - poly(acrylic acid - co - hydroxyethyl acrylate) cross - linker, namely the strong adhesion type adhesive, marked as A1.

[0050] Apply the adhesive A1 prepared in Example 1 and the adhesive B1 in Comparative Example 1 to the negative electrode of a lithium - ion battery and assemble a lithium - ion battery, and test the electrochemical performance. The method is as follows:

[0051] (a) Configure the silicon - based negative electrode active material (silicon oxide / carbon material with a commercial specific capacity of 500 mAh / g, model Shanshan GS1S - C500), conductive additive (conductive carbon black) and adhesive according to a mass ratio of 95:1:4, and uniformly disperse them in deionized water by ball - milling to obtain a uniformly mixed negative electrode slurry.

[0052] (b) Use an automatic film - coating machine to uniformly coat the slurry in (a) on an 8 - micron - thick copper foil with a coating thickness of 220 microns, and then place it in a vacuum drying oven at 80 °C to remove the solvent. The electrode areal loading is measured to be 8 - 9 mg / cm 2 . After drying, cut it into negative electrode sheets with a diameter of 12 mm.

[0053] (c) Transfer the electrode sheet prepared in (b) to a glove box filled with argon, assemble it into a 2032 coin - type half - cell, use a lithium sheet as the counter electrode, use Celgard 2325 polypropylene - polyethylene - polypropylene (PP - PE - PP) membrane as the separator, and use a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1:1) containing 1 M lithium hexafluorophosphate (LiPF6) as the electrolyte, and add 10% by volume of fluoroethylene carbonate (FEC).

[0054] (d) Let the coin - type battery assembled in (c) stand for 10 h, and then activate it at a rate of 0.05 C for one week in the voltage range of 0.01 - 2.00 V, and then perform charge - discharge cycles at a rate of 0.5 C.

[0055] Figure 1 For the linear sweep voltammetry curve of the Cu|Li battery with adhesive A1 under the condition of 0.1 mV s -1 conditions. Figure 1 The results show that adhesive A1 has high electrochemical stability at voltages of 0.01 - 2.00 V.

[0056] Figure 2Cycling performance comparison chart of lithium-ion half-cells with adhesive A1 in Example 1 and adhesive B1 in Comparative Example 1 (since the charge-discharge efficiency of both Example 1 and Comparative Example 1 is above 99% after activation and stabilization, the two lines are almost coincident). From Figure 2 It can be seen that at a current density of 0.5C, the electrode surface capacity of the electrode using adhesive A1 is ~3.5 mAh / cm 2 , and it has a high capacity retention rate (91.1%) after 150 cycles. By comparison, the adhesive A1 prepared in Example 1 has higher cycling stability than the comparative sample B1 (capacity retention rate of 36.9%).

[0057] Figure 3 Cycling performance chart of the lithium-ion soft-pack battery with adhesive A1. From Figure 3 It can be seen that the adhesive A1 prepared in Example 1 gives the soft-pack battery a very prominent capacity retention rate (500 cycles, 81.34%). Adhesive A1 helps to improve the electrochemical cycling performance of the silicon-based anode and has great potential in practical applications.

[0058] Example 2

[0059] A strongly adhesive binder is prepared as follows:

[0060] (1) Take 3.6 g of acrylic acid and 0.4 g of γ-methacryloxypropyltrimethoxysilane and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 55 °C, and the holding times are 4 h and 4 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0061] (2) Take 2 g of acrylic acid and 2 g of hydroxyethyl acrylate and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 55 °C, and the holding times are 4 h and 4 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0062] (3) Add 4 g of the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution to 4 g of the poly(acrylic acid-co-hydroxyethyl acrylate) solution, and stir for 4 h to obtain a clear poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane))-poly(acrylic acid-co-hydroxyethyl acrylate) crosslinker, which is the strongly adhesive binder, labeled as A2.

[0063] Example 3

[0064] A strongly adhesive binder, the preparation method is as follows:

[0065] (1) Take 3.8 g of acrylic acid and 0.2 g of γ-methacryloxypropyltrimethoxysilane and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 38 °C to 58 °C, and the holding times are 3.5 h and 4.5 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0066] (2) Take 2.4 g of acrylic acid and 1.6 g of hydroxyethyl acrylate and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 38 °C to 58 °C, and the holding times are 3.5 h and 4.5 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0067] (3) Add 4 g of the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution to 4 g of the poly(acrylic acid-co-hydroxyethyl acrylate) solution, and stir for 4 h to obtain a clear poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane))-poly(acrylic acid-co-hydroxyethyl acrylate) crosslinker, that is, the strongly adhesive binder, marked as A3.

[0068] Example 4

[0069] A strongly adhesive binder, the preparation method is as follows:

[0070] (1) Take 3.6 g of acrylic acid and 0.4 g of γ-methacryloxypropyltrimethoxysilane and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 38 °C to 58 °C, and the holding times are 3.5 h and 4.5 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0071] (2) Take 2 g of acrylic acid and 2 g of hydroxyethyl acrylate and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 38 °C to 58 °C, and the holding times are 3.5 and 4.5 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0072] (3) Add 4 g of poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution to 2 g of poly(acrylic acid - co - 2 - hydroxyethyl acrylate) solution, and stir for 4 h to obtain a clear poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) - poly(acrylic acid - co - 2 - hydroxyethyl acrylate) cross - linker, which is the strong - adhesion adhesive, labeled as A4.

[0073] Example 5

[0074] A strong - adhesion adhesive, the preparation method is as follows:

[0075] (1) Take 3.6 g of acrylic acid and 0.4 g of γ - methacryloyloxypropyltrimethoxysilane and dissolve them in 36 mL of deionized water, and stir well; add 1.5 mg of potassium persulfate and 0.75 mg of sodium bisulfite to the above solution, and purge with nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 55 °C, and the holding times are 3.5 h and 5 h respectively to obtain a poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution;

[0076] (2) Take 2 g of acrylic acid and 2 g of 2 - hydroxyethyl acrylate and dissolve them in 36 mL of deionized water, and stir well; add 1.5 mg of potassium persulfate and 0.75 mg of sodium bisulfite to the above solution, and purge with nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 55 °C, and the holding times are 3.5 h and 5 h respectively to obtain a poly(acrylic acid - co - 2 - hydroxyethyl acrylate) solution;

[0077] (3) Add 4 g of poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution to 4 g of poly(acrylic acid - co - 2 - hydroxyethyl acrylate) solution, and stir for 4 h to obtain a clear poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) - poly(acrylic acid - co - 2 - hydroxyethyl acrylate) cross - linker, which is the strong - adhesion adhesive, labeled as A5.

[0078] Example 6

[0079] A strong - adhesion adhesive, the preparation method is as follows:

[0080] (1) Dissolve 3.6 g of acrylic acid and 0.4 g of γ-methacryloxypropyltrimethoxysilane in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 55 °C, and the holding times are 3.5 h and 5 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0081] (2) Dissolve 2.8 g of acrylic acid and 1.2 g of hydroxyethyl acrylate in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 minutes to remove the oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 55 °C, and the holding times are 3.5 h and 5 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution.

[0082] (3) Add 4 g of the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution to 4 g of the poly(acrylic acid-co-hydroxyethyl acrylate) solution, and stir for 4 h to obtain a clear poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane))-poly(acrylic acid-co-hydroxyethyl acrylate) crosslinker, that is, the strong adhesion type adhesive, marked as A6.

[0083] Example 7

[0084] A strong adhesion type adhesive, the preparation method is as follows:

[0085] (1) Dissolve 3.8 g of acrylic acid and 0.2 g of γ-methacryloxypropyltrimethoxysilane in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 35 °C to 55 °C, and the holding times are 3 h and 5.5 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0086] (2) Dissolve 3.2 g of acrylic acid and 0.8 g of hydroxyethyl acrylate in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 35 °C to 55 °C, and the holding times are 3 h and 5.5 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0087] (3) Add 4 g of poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution to 4 g of poly(acrylic acid - co - hydroxyethyl acrylate) solution, and stir for 3 h to obtain a clear poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) - poly(acrylic acid - co - hydroxyethyl acrylate) crosslinker, which is the strong adhesion type adhesive, marked as A7.

[0088] Example 8

[0089] A strong adhesion type adhesive, the preparation method is as follows:

[0090] (1) Take 3.8 g of acrylic acid and 0.2 g of γ - methacryloyloxypropyltrimethoxysilane and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 35 °C to 55 °C, and the holding times are 3 h and 5.5 h respectively to obtain a poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution;

[0091] (2) Take 3.0 g of acrylic acid and 1.0 g of hydroxyethyl acrylate and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 35 °C to 55 °C, and the holding times are 3 h and 5.5 h respectively to obtain a poly(acrylic acid - co - hydroxyethyl acrylate) solution;

[0092] (3) Add 4 g of poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution to 4 g of poly(acrylic acid - co - hydroxyethyl acrylate) solution, and stir for 3 h to obtain a clear poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) - poly(acrylic acid - co - hydroxyethyl acrylate) crosslinker, which is the strong adhesion type adhesive, marked as A8.

[0093] Example 9

[0094] A strong adhesion type adhesive, the preparation method is as follows:

[0095] (1) Dissolve 3.8 g of acrylic acid and 0.2 g of γ-methacryloxypropyltrimethoxysilane in 36 mL of deionized water, and stir well; add 4 mg of azobisisobutyramidine hydrochloride and 2 mg of potassium persulfate to the above solution, and pass nitrogen for 40 min to remove oxygen in the system; raise the temperature of the obtained solution system from 38 °C to 58 °C, and the holding times are 4 h and 5.5 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0096] (2) Dissolve 2 g of acrylic acid and 2 g of hydroxyethyl acrylate in 36 mL of deionized water, and stir well; add 4 mg of azobisisobutyramidine hydrochloride and 2 mg of potassium persulfate to the above solution, and pass nitrogen for 40 min to remove oxygen in the system; raise the temperature of the obtained solution system from 38 °C to 58 °C, and the holding times are 4 h and 5.5 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0097] (3) Add 4 g of the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution to 4 g of the poly(acrylic acid-co-hydroxyethyl acrylate) solution, and stir for 4 h to obtain a clear poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane))-poly(acrylic acid-co-hydroxyethyl acrylate) crosslinker, namely the strong adhesion type adhesive, marked as A9.

[0098] Example 10

[0099] A strong adhesion type adhesive, the preparation method is as follows:

[0100] (1) Dissolve 3.6 g of acrylic acid and 0.4 g of γ-methacryloxypropyltrimethoxysilane in 36 mL of deionized water, and stir well; add 4 mg of azobisisobutyramidine hydrochloride and 2 mg of potassium persulfate to the solution, and pass nitrogen for 40 min to remove oxygen in the system; raise the temperature of the obtained solution system from 38 °C to 58 °C, and the holding times are 4 h and 5.5 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0101] (2) Dissolve 2.4 g of acrylic acid and 1.6 g of hydroxyethyl acrylate in 36 mL of deionized water, and stir well; add 4 mg of azobisisobutyramidine hydrochloride and 2 mg of potassium persulfate to the above solution, and pass nitrogen for 40 min to remove oxygen in the system; raise the temperature of the obtained solution system from 38 °C to 58 °C, and the holding times are 4 h and 5.5 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0102] (3) Add 4 g of poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution to 4 g of poly(acrylic acid - co - 2 - hydroxyethyl acrylate) solution, and stir for 2 h to obtain a clear poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) - poly(acrylic acid - co - 2 - hydroxyethyl acrylate) cross - linker, which is the strong - adhesion adhesive, marked as A10.

[0103] Example 11

[0104] A strong - adhesion adhesive, the preparation method is as follows:

[0105] (1) Take 3.6 g of acrylic acid and 0.4 g of γ - methacryloyloxypropyltrimethoxysilane and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above - mentioned solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 60 °C, and the holding times are 3 h and 4 h respectively to obtain a poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution;

[0106] (2) Take 2.8 g of acrylic acid and 1.2 g of 2 - hydroxyethyl acrylate and dissolve them in 36 mL of deionized water, and stir well; add 4 mg of azobisisobutyramidine hydrochloride and 2 mg of potassium persulfate to the above - mentioned solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 60 °C, and the holding times are 3 h and 4 h respectively to obtain a poly(acrylic acid - co - 2 - hydroxyethyl acrylate) solution.

[0107] (3) Add 4 g of poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution to 4 g of poly(acrylic acid - co - 2 - hydroxyethyl acrylate) solution, and stir for 2 h to obtain a clear poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) - poly(acrylic acid - co - 2 - hydroxyethyl acrylate) cross - linker, which is the strong - adhesion adhesive, marked as A11.

[0108] Example 12

[0109] A strong - adhesion adhesive, the preparation method is as follows:

[0110] (1) Dissolve 3.6 g of acrylic acid and 0.4 g of γ-methacryloxypropyltrimethoxysilane in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 60 °C, and the holding times are 3 h and 4 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0111] (2) Dissolve 3.2 g of acrylic acid and 0.8 g of hydroxyethyl acrylate in 36 mL of deionized water, and stir well; add 4 mg of azodiisobutyramidine hydrochloride and 2 mg of potassium persulfate to the above solution, and pass nitrogen for 40 min to remove oxygen in the system; raise the temperature of the obtained solution system from 40 °C to 60 °C, and the holding times are 3 h and 4 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0112] (3) Add 4 g of the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution to 4 g of the poly(acrylic acid-co-hydroxyethyl acrylate) solution, and stir for 4 h to obtain a clear poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane))-poly(acrylic acid-co-hydroxyethyl acrylate) crosslinker, namely the strong adhesion type adhesive, labeled as A12.

[0113] Example 13

[0114] A strong adhesion type adhesive, the preparation method is as follows:

[0115] (1) Dissolve 3.6 g of acrylic acid and 0.4 g of γ-methacryloxypropyltrimethoxysilane in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove oxygen in the system; raise the temperature of the obtained solution system from 35 °C to 50 °C, and the holding times are 5 h and 4 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0116] (2) Dissolve 3.0 g of acrylic acid and 1.0 g of hydroxyethyl acrylate in 36 mL of deionized water, and stir well; add 4 mg of azodiisobutyramidine hydrochloride and 2 mg of potassium persulfate to the above solution, and pass nitrogen for 40 min to remove oxygen in the system; raise the temperature of the obtained solution system from 35 °C to 50 °C, and the holding times are 5 h and 4 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0117] (3) Add 2 g of poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution to 2 g of poly(acrylic acid - co - 2 - hydroxyethyl acrylate) solution, and stir for 3 h to obtain a clear poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) - poly(acrylic acid - co - 2 - hydroxyethyl acrylate) cross - linker, which is the strong - adhesion adhesive, marked as A13.

[0118] Example 14

[0119] A strong - adhesion adhesive, the preparation method is as follows:

[0120] (1) Take 3.6 g of acrylic acid and 0.4 g of γ - methacryloyloxypropyltrimethoxysilane and dissolve them in 36 mL of deionized water, and stir well; add 2 mg of potassium persulfate and 1 mg of sodium bisulfite to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 35 °C to 50 °C, and the holding times are 5 h and 4 h respectively to obtain a poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution.

[0121] (2) Take 2.8 g of acrylic acid and 1.2 g of 2 - hydroxyethyl acrylate and dissolve them in 36 mL of deionized water, and stir well; add 4 mg of azodiisobutyramidine hydrochloride and 2 mg of potassium persulfate to the above solution, and pass nitrogen for 40 min to remove the oxygen in the system; raise the temperature of the obtained solution system from 35 °C to 50 °C, and the holding times are 5 h and 4 h respectively to obtain a poly(acrylic acid - co - 2 - hydroxyethyl acrylate) solution;

[0122] (3) Add 4 g of poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) solution to 2 g of poly(acrylic acid - co - 2 - hydroxyethyl acrylate) solution, and stir for 4 h to obtain a clear poly(acrylic acid - co - (γ - methacryloyloxypropyltrimethoxysilane)) - poly(acrylic acid - co - 2 - hydroxyethyl acrylate) cross - linker, which is the strong - adhesion adhesive, marked as A14.

[0123] Example 15

[0124] A strong - adhesion adhesive, the preparation method is as follows:

[0125] (1) Dissolve 3.6 g of acrylic acid and 0.4 g of γ-methacryloxypropyltrimethoxysilane in 36 mL of deionized water, and stir well; add 4 mg of azobisisobutyramidine hydrochloride and 2 mg of potassium persulfate to the above solution, and pass nitrogen for 40 min to remove oxygen in the system; raise the temperature of the obtained solution system from 35 °C to 50 °C, and the holding times are 5 h and 4 h respectively to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution;

[0126] (2) Dissolve 3.2 g of acrylic acid and 0.8 g of hydroxyethyl acrylate in 36 mL of deionized water, and stir well; add 4 mg of azobisisobutyramidine hydrochloride and 2 mg of potassium persulfate to the above solution, and pass nitrogen for 40 min to remove oxygen in the system; raise the temperature of the obtained solution system from 35 °C to 50 °C, and the holding times are 5 h and 4 h respectively to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution;

[0127] (3) Add 4 g of the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution to 2 g of the poly(acrylic acid-co-hydroxyethyl acrylate) solution, and stir for 4 h to obtain a clear poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane))-poly(acrylic acid-co-hydroxyethyl acrylate) crosslinker, that is, the strong adhesion type adhesive, marked as A15.

[0128] Apply the adhesives A2 - A15 prepared in Examples 2 - 15 to the negative electrode of the lithium-ion battery and assemble the lithium-ion battery according to the method of Example 1, and test the electrochemical performance. The test results are listed in Table 1:

[0129] Table 1 Electrochemical performance of lithium-ion batteries assembled with adhesives A1 - A15

[0130] Number Capacity retention rate after 150 weeks (%) Initial week Coulomb efficiency (%) Example 1 91.1 89.2 Example 2 91.5 88.1 Example 3 90.2 87.5 Example 4 92.6 86.3 Example 5 90.7 88.7 Example 6 90.3 87.5 Example 7 92.2 87.6 Example 8 92.3 87.5 Example 9 91.4 87.2 Example 10 91.2 86.3 Example 11 90.5 86.3 Example 12 91.6 86.9 Example 13 92.2 87.4 Example 14 90.5 87.8 Example 15 91.1 85.5 Comparative Example 1 36.9 88.2

[0131] It can be seen from the results in Table 1 that the adhesive prepared in the present invention, as the adhesive for the silicon-based negative electrode of the lithium-ion battery, when the capacity of the electrode reaches 3.5 mAh / cm 2 , the first-cycle Coulombic efficiency of the thick electrode reaches more than 85%, and the capacity retention rate after 150 cycles is above 90%. While the first-cycle efficiency of the adhesive in Comparative Example 1 is about 88.2%, but the capacity retention rate after 150 cycles is only 36.9%. It can be seen that the adhesive of the present invention significantly improves the cycle stability of the silicon-based negative electrode material.

[0132] The present invention also uses the 180° peel test to characterize the adhesion strength of the test electrode, Figure 4 It is a comparative diagram of the peel strength of the negative electrode sheets of lithium-ion batteries with adhesives A1, A2, and A3. FromFigure 4 It can be seen that the average peel strength of the silicon-based anode using adhesives A1, A2, and A3 is greater than 150 N m -1 .

[0133] In the present invention, a series of poly(acrylic acid-co-(γ-methacryloyloxypropyltrimethoxysilane))-poly(acrylic acid-co-hydroxyethyl acrylate) adhesives with different stoichiometric ratios are prepared by traditional free radical polymerization. The adhesive exhibits stable electrochemical cyclability. In this system, the bonding ability between active material particles and between active material particles and copper foil is enhanced by introducing strongly polar groups. The introduction of SiO2 nano-crosslinking points improves the cohesion between polymer segments, effectively enhancing the adhesion of the polymer adhesive; the multiple dynamic hydrogen bonds formed between carboxyl groups and hydroxyl groups can effectively relieve the stress concentration between silicon-based material particles, stabilize the surface structure of the anode material, and improve the electrochemical performance of the battery; the adhesive is water-soluble, environmentally friendly, and its structure is easy to regulate, which can well meet the preparation and production requirements of silicon-based anodes.

[0134] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a strong adhesion type adhesive, characterized in that, It includes the following steps: Mix acrylic acid, γ-methacryloxypropyltrimethoxysilane, water and a first initiator to carry out a first polymerization reaction to obtain a poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution; the molar ratio of acrylic acid to γ-methacryloxypropyltrimethoxysilane is (9.9~8):(0.1~2); Mix acrylic acid, hydroxyethyl acrylate, water and a second initiator to carry out a second polymerization reaction to obtain a poly(acrylic acid-co-hydroxyethyl acrylate) solution; the molar ratio of acrylic acid to hydroxyethyl acrylate is (9~5):(1~5); Mix the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution and the poly(acrylic acid-co-hydroxyethyl acrylate) solution to carry out a physical cross-linking reaction to obtain the strong adhesion adhesive; the mass ratio of the poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) solution to the poly(acrylic acid-co-hydroxyethyl acrylate) solution is (1~2):

1.

2. The preparation method according to claim 1, characterized in that, The mass of the first initiator is 0.05~0.15% of the sum of the masses of acrylic acid and γ-methacryloxypropyltrimethoxysilane; the total mass concentration of acrylic acid and γ-methacryloxypropyltrimethoxysilane in water is 8~10%.

3. The preparation method according to claim 1, characterized in that, The mass of the second initiator is 0.05~0.2% of the sum of the masses of acrylic acid and hydroxyethyl acrylate; the total mass concentration of acrylic acid and hydroxyethyl acrylate in water is 8~10%.

4. The preparation method according to any one of claims 1 to 3, characterized in that The first initiator and the second initiator independently include one or more of azobisisobutyronitrile, azobis(isobutyramidine) dihydrochloride, azodiisovaleronitrile, ammonium persulfate, sodium bisulfite and potassium persulfate.

5. The preparation method according to claim 1, characterized in that, Both the first polymerization reaction and the second polymerization reaction include a first reaction stage and a second reaction stage carried out in sequence. The temperature of the first reaction stage is 35~40°C, and the heat preservation time is 3~5h. The temperature of the second reaction stage is 50~60°C, and the heat preservation time is 4~6h.

6. The preparation method according to claim 1, wherein The temperature of the physical cross-linking reaction is 25~30°C, and the heat preservation time is 2~4h.

7. The strong adhesion adhesive prepared by the preparation method according to any one of claims 1~6, wherein the active ingredient of the adhesive is the physical cross-linking product of poly(acrylic acid-co-(γ-methacryloxypropyltrimethoxysilane)) and poly(acrylic acid-co-hydroxyethyl acrylate).

8. Application of the strong adhesion adhesive according to claim 7 as an adhesive for a silicon-based negative electrode of a lithium-ion battery.

9. A silicon-based anode slurry for a lithium-ion battery, characterized in that, It includes a silicon-based active material, a conductive additive and an adhesive, and the adhesive is the strong adhesion adhesive according to claim 7.

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