A silicon anode material binder, its preparation method and application

Abstract

The present invention relates to the field of silicon anode materials for lithium-ion batteries, and discloses a binder for silicon anode materials, a preparation method thereof, and an application thereof. First, a copolymer P(AA-MA-AN) is synthesized by free radical polymerization of acrylic acid, methyl acrylate, and acrylonitrile monomers. Subsequently, a self-healing binder P(AA-MA-AN)coPEI with a rich three-dimensional spatial structure is formed through reversible Coulomb crosslinking between P(AA-MA-AN) and branched polyethyleneimine. The binder for silicon anode materials of the present invention is used for silicon anode materials of lithium batteries, which can not only significantly improve the comprehensive performance and cycle stability of silicon anode materials, but also achieve environmentally friendly recycling and regeneration.

Description

Technical Field

[0001] The present invention belongs to the field of silicon anode materials for lithium-ion batteries, and particularly relates to an adhesive for silicon anode materials, a preparation method thereof, and applications thereof. Background Art

[0002] As a core energy storage device in fields such as electric vehicles and portable electronic devices, high-performance lithium batteries have a continuously growing market demand. Electrode materials, as the key factors determining the energy density, cycle life, and safety of lithium batteries, have become a research hotspot in both academia and industry. Among them, the type of active material determines the upper limit of the battery capacity. Traditional active materials are mainly various forms of graphite based on carbon elements, but their theoretical capacity upper limit is 375 mAh / g, while the theoretical capacity of silicon-based materials reaches 4200 mAh / g (more than 11 times that of the theoretical capacity of traditional graphite anodes, which is 375 mAh / g). Therefore, it is currently the best choice to replace graphite as the next-generation lithium battery anode material.

[0003] During the transformation process from carbon to silicon, researchers found that lithium will have volume changes due to the detachment and insertion of silicon during battery operation, and the fluctuation range can reach 300% - 400%, resulting in the destruction of the electrode structure and the attenuation of the battery capacity, seriously affecting the life and safety of the battery; at the same time, electrodes with silicon as the active material also have problems such as poor electron migration ability and unstable growth of the solid electrolyte interface.

[0004] To solve the above problems, the existing technology mainly focuses on developing new adhesives to improve the mechanical stability and electrochemical performance of anode materials. Currently, commercially available adhesives mainly include categories such as polyvinylpyrrolidone (PVP), polyurethane (PU), and polyimide (PI). However, although these adhesives can improve the stability and conductivity of the electrode to a certain extent, they still have the following deficiencies: First, their compatibility with silicon materials is poor, resulting in unsatisfactory adhesion effects; second, most traditional adhesives have insufficient thermal stability under high-temperature conditions, which may affect the safety and life of the battery; third, their environmental friendliness is relatively low, and the preparation process may cause certain impacts on the environment.

[0005] In recent years, adhesives represented by polyacrylic acid (PAA) and its modified derivatives have received attention due to their high carboxyl density (-COOH) and strong chemical affinity with silicon. However, the main chain of PAA has high rigidity and is prone to main chain breakage or interfacial desorption during the repeated expansion / contraction of the silicon volume, unable to meet the requirements of long cycle life.

[0006] Therefore, developing an adhesive for silicon-based anode materials that combines strong interfacial adhesion, dynamic flexibility, and self-healing functions has become the key to breaking through the bottleneck of existing technologies and realizing the industrialization of high-energy silicon-based lithium batteries. Summary of the Invention

[0007] In view of the above technical problems, the purpose of the present invention is to provide an adhesive for silicon anode materials, a preparation method thereof and an application. This adhesive can not only better adapt to the volume change of silicon materials, but also is conducive to the recovery of anode active material substances to a certain extent.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect of the present invention, it is to provide a preparation method of an adhesive for silicon anode materials, including the following steps:

[0010] S1. Take acrylic acid solution, methyl acrylate, and acrylonitrile according to the molar ratio of acrylic acid: methyl acrylate: acrylonitrile = (4 - 5):(1 - 2):(4 - 5), inject them into the same closed container, while stirring in the closed container, evacuate and refill nitrogen 3 - 5 times to fully discharge air, heat the closed container, continuously stir, and then inject an initiator solution into the closed container to initiate a free radical polymerization reaction to obtain a first mixed solution containing P(AA - MA - AN);

[0011] S2. Add a pH regulator to the first mixed solution, stir while adding, and adjust the pH value of the first mixed solution to acidic to obtain a second mixed solution containing P(AA - MA - AN);

[0012] S3. Take the second mixed solution and a PEI solution according to the mass ratio of P(AA - MA - AN):PEI = 1:(0.8 - 1.4), add deionized water to dilute to a solid content of 4% - 10%, and mix and stir at 20 - 30 °C for 30 - 40 min to obtain a solution containing P(AA - MA - AN)coPEI adhesive.

[0013] Further, the preparation of the acrylic acid solution in step S1 is specifically as follows: Measure acrylic acid, and add an equal - volume sodium hydroxide or lithium hydroxide solution with a concentration of 8 - 12 wt% to acrylic acid for neutralization to obtain an acrylic acid solution.

[0014] Further, in step S1, the initiator solution is an ammonium persulfate solution, its concentration is 0.4 wt% - 0.6 wt%, and the addition amount is 0.1% - 0.5% of the total mass of acrylic acid, methyl acrylate, and acrylonitrile.

[0015] Further, in step S1, the heating temperature of the free radical polymerization reaction is 70 - 80 °C, and the reaction time is 5 h - 10 h.

[0016] Further, in step S2, the pH regulator is a sodium hydroxide or lithium hydroxide solution with a concentration of 8 wt - 12 wt%.

[0017] Furthermore, the structural formula of the P(AA-MA-AN) is

[0018]

[0019] wherein, a:b:c = (4 - 5):(1 - 2):(4 - 5).

[0020] Furthermore, in the step S2, the pH value of the second mixed solution is 3.5 - 4.5.

[0021] Furthermore, in the step S3, the PEI is branched polyethyleneimine, and its molecular weight is 55000 - 65000.

[0022] Furthermore, in the step S3, the concentration of the PEI solution is 40wt - 60wt%.

[0023] Furthermore, in the step S3, the mass ratio of P(AA-MA-AN):PEI = 1:1.

[0024] Furthermore, in the step S3, the structural formula of the P(AA-MA-AN) coPEI adhesive is

[0025]

[0026] wherein, a:b:c = (4 - 5):(1 - 2):(4 - 5).

[0027] The second aspect of the present invention lies in providing a silicon negative electrode material adhesive prepared according to the above preparation method.

[0028] The third aspect of the present invention lies in providing an application of the above silicon negative electrode material adhesive in a lithium battery.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] The silicon negative electrode material adhesive prepared by the preparation method of the present invention forms a self-healing adhesive with a rich three-dimensional spatial structure through the reversible Coulomb cross-linking between P(AA-MA-AN) and branched polyethyleneimine, which can not only significantly improve the comprehensive performance and cycle stability of the silicon negative electrode material, but also realize environmentally friendly recycling and regeneration, which is mainly reflected in the following aspects:

[0031] 1. In the copolymer P(AA-MA-AN), the abundant carboxyl groups on polyacrylic acid will provide sufficient hydrogen bonds to form a stable bonding effect with silicon particles. The nitrile groups of acrylonitrile can improve the electron transport ability, thereby enhancing the conductivity of the electrode material. The segments formed by methyl acrylate can significantly improve the flexibility of the main chain. The branched polyethyleneimine has a cyclic extended network structure, and the amino ions on it can combine with the carboxyl ions on the polyacrylic acid chain segment in the copolymer P(AA-MA-AN) through Coulomb cross-linking to form a three-dimensional network structure, tightly and firmly encapsulating the silicon particles therein. The flexibility and reversible cross-linking of the P(AA-MA-AN)coPEI binder molecules enable the binder to recover the bonding effect after the silicon volume expands and contracts, thus significantly improving the cycle life and stability of the battery, enabling the battery to maintain a capacity retention rate of ≥81% after 200 cycles at a current density of 0.5C, and the electrode remains intact before and after cycling without cracking;

[0032] 2. The reversible Coulomb cross-linking between the copolymer P(AA-MA-AN) and the branched polyethyleneimine has pH-responsive characteristics. Based on the response characteristics of the P(AA-MA-AN)coPEI binder, the active substances in waste battery materials can be recovered by washing with an alkali solution: at room temperature (25°C), the electrode sheet is treated with a 1M NaOH solution, and the binder network disintegrates within 2 hours, and the recovery rate of the electrode active substances is ≥70%. Description of the Drawings

[0033] Figure 1 is the SEM image of the electrode surface of some embodiments and comparative examples of the present invention. Among them, (a) is the SEM image of the electrode surface after 200 cycles in Example 1 of the present invention, (b) is the SEM image of the electrode surface after 200 cycles in Example 2 of the present invention, (c) is the SEM image of the electrode surface after 200 cycles in Example 3 of the present invention, (d) is the SEM image of the electrode surface after 200 cycles in Example 4 of the present invention, (e) is the SEM image of the electrode surface after 200 cycles in Example 5 of the present invention, (f) is the SEM image of the electrode surface after 200 cycles in Example 6 of the present invention, and (g) is the SEM image of the electrode surface after 200 cycles in Comparative Example 1.

[0034] Figure 2 It is a comparison of the infrared spectra of PEI, P(AA-MA-AN), and P(AA-MA-AN)coPEI in the present invention.

[0035] Figure 3 It is the capacity retention rate curve of the batteries in Example 1, Example 4, Example 5, and Example 6 of the present invention after 200 cycles. Detailed Embodiments

[0036] The present invention will be further described below in conjunction with the accompanying drawings through specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0037] The first aspect of the present invention provides a preparation method of a silicon anode material binder, comprising the following steps:

[0038] (1) Preparation of acrylic acid solution: Measure a certain amount of acrylic acid, and add an equal volume of sodium hydroxide or lithium hydroxide solution with a concentration of 8-12 wt% to acrylic acid for neutralization to obtain an acrylic acid solution; because the free radical polymerization reaction of pure acrylic acid is relatively active and prone to explosive polymerization; and in the present invention, the preferred molecular weight of P(AA-MA-AN) is 500000, so a certain amount of sodium hydroxide is added to reduce the molecular weight of the polymer;

[0039] (2) Preparation of methyl acrylate solution: Measure a certain amount of methyl acrylate and place it in a flask, and add deionized water to obtain a methyl acrylate solution;

[0040] (3) Measure a certain amount of acrylonitrile;

[0041] (4) Preparation of initiator solution: Dissolve ammonium persulfate in deionized water to prepare an ammonium persulfate solution with a concentration of 0.4 wt% - 0.6 wt%;

[0042] (5) Inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the same closed container. Under a stirring speed of 220 - 280 rpm, evacuate and fill with nitrogen 3 - 5 times to fully discharge the air (subsequently, maintain this stirring speed until the reaction ends). Then heat the closed container. When the internal temperature reaches 70 - 80 °C, inject the initiator solution prepared in step (4) into the closed container (the addition amount is 0.1% - 0.5% of the total mass of the acrylic acid, methyl acrylate, and acrylonitrile monomers) to initiate a free radical polymerization reaction. Keep the reaction temperature at 70 - 80 °C for 5 - 10 h to obtain a first mixed solution containing P(AA-MA-AN); wherein, the structural formula of P(AA-MA-AN) is

[0043]

[0044] wherein, a:b:c = (4 - 5):(1 - 2):(4 - 5).

[0045] (6) Add a sodium hydroxide or lithium hydroxide solution with a concentration of 8 - 12 wt% to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 3.5 - 4.5 to obtain a second mixed solution containing P(AA-MA-AN);

[0046] (7) Mix the second mixed solution and the PEI solution (where PEI is branched polyethyleneimine with a molecular weight of 55,000 - 65,000 and the concentration of the PEI solution is 40 - 60 wt%) according to the mass ratio of P(AA - MA - AN):PEI = 1:(0.8 - 1.4), add deionized water to dilute to a solid content of 4% - 10%, and mix and stir at 20 - 30 °C for 30 - 40 min to obtain a solution containing the P(AA - MA - AN)coPEI binder. The structural formula of the P(AA - MA - AN)coPEI binder is

[0047]

[0048] where a:b:c = (4 - 5):(1 - 2):(4 - 5).

[0049] The silicon anode material binder provided by the present invention, its preparation method and application form a self - healing binder P(AA - MA - AN)coPEI with a rich three - dimensional spatial structure through the reversible Coulomb cross - linking between P(AA - MA - AN) and branched polyethyleneimine; P(AA - MA - AN) is synthesized by free - radical polymerization of acrylic acid, methyl acrylate, and acrylonitrile monomers; the silicon anode material binder of the present invention has excellent water solubility, self - healing property, thermal stability, and high bonding strength; a large number of carboxyl groups on the main chain PAA of the binder molecule are tightly bonded to silicon through hydrogen bonding, while PMA can improve the flexibility of the polymer, providing sufficient stress space for the binder molecule during the volume expansion and contraction of silicon particles; the nitrile group (C≡N) on the main chain of acrylonitrile has strong polarity and can interact with the electrolyte in the lithium - ion battery to improve the ionic conductivity and accelerate the + transmission rate during the charge - discharge process. However, the introduction of the nitrile group will reduce the solubility of the binder molecule in water, while branched polyethyleneimine PEI is a cationic polyelectrolyte that can be mixed with water in any proportion and has better processability and mechanical properties than the linear type. It has a highly branched structure, a larger surface area, and can provide more amino functional sites, enabling the binder molecule formed in the subsequent cross - linking reaction to have a broad spatial structure to accommodate silicon particles and other electrode materials; after PEI participates in the cross - linking, it greatly increases the solubility of the binder system in water and is easily soluble in water. At the same time, under acidic conditions, the primary amine of branched polyethyleneimine PEI will dissociate to form amino ions, which are easily cross - linked with carboxyl ions in the solution under electrostatic interaction to form Coulomb cross - links. In addition, when the pH value is greater than 7, metal cations combine with carboxyl ions to break the cross - link between amino ions and carboxyl ions. Based on this property, the electrode material containing the silicon anode material binder of the present invention can be soaked in an alkaline solution to better separate the negative electrode active material and conductive carbon, and the recovered materials can be made into batteries for reuse, realizing environmentally friendly recycling and regeneration.

[0050] It should be noted that the first mixed solution containing P(AA-MA-AN), the second mixed solution containing P(AA-MA-AN), and the solution containing P(AA-MA-AN) coPEI binder prepared in the present invention are all viscous liquids, which can be directly used as binders, or can be diluted or concentrated and then used as binders.

[0051] Hereinafter, examples and comparative examples are given to more specifically illustrate the implementation manners of the present application.

[0052] For the battery cycle stability test of the present invention, the solution containing P(AA-MA-AN) coPEI binder obtained in step (7) is directly used as the binder for the silicon negative electrode material, and a coin-type half-cell is assembled for charge and discharge tests, including the following steps:

[0053] Preparation of coin-type half-cell;

[0054] Static placement: The assembled battery is statically placed for 12 hours to allow the electrolyte to fully infiltrate the electrode material;

[0055] Charge and discharge cycle test;

[0056] a. Test system: A battery test system of Blue Electronic Co., Ltd. is used for constant current charge and discharge cycle tests.

[0057] b. Test conditions

[0058] Temperature: Room temperature (25 °C).

[0059] Voltage range: 0.01–1.2 V (vs Li / Li⁺).

[0060] c. Test procedure:

[0061] First, cycle 4 times at 0.05 C (2,10 mAh·g⁻¹) to activate the electrode material.

[0062] Then, perform a long cycle test at 0.5 C to evaluate the battery cycle stability.

[0063] Among them, the preparation of the coin-type half-cell includes the following steps:

[0064] Step 1: Mixing of electrode materials and preparation of slurry

[0065] Put nano-silicon (Si) and conductive carbon black (Super P) into a vacuum oven and dry at 50 °C for 8 hours to remove the moisture on the material surface; take nano-silicon powder, Super P and the binder for the silicon negative electrode material according to the solid mass ratio of 8:1:1. Add the nano-silicon powder and Super P into a quartz mortar and grind for 30 minutes to ensure thorough mixing of the two. Then add the mixture into the binder for the silicon negative electrode material and stir for 12 h; (Note: Since the viscosity of the binder is very high, an appropriate amount of deionized water needs to be added to adjust the viscosity to ensure uniform mixing).

[0066] Step 2: Preparation of the electrode sheet

[0067] Use a four-sided coater (doctor blade) to evenly coat the electrode slurry onto a copper foil (current collector), controlling the coating thickness to be uniform; place the coated electrode sheet in a vacuum oven and dry at 80 °C for 12 hours to remove the solvent.

[0068] Use a slicing machine to cut the electrode sheet into circular pieces with a diameter of 9 mm and place them in a glove box for standby;

[0069] Step 3: Battery assembly

[0070] Complete the assembly in a vacuum glove box, ensuring that the water and oxygen values in the glove box are lower than 0.01 ppm;

[0071] Electrolyte: 1 M LiPF6 is dissolved in a mixed solution of dimethyl carbonate (DMC), ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1:1:1);

[0072] Separator: Celgaed 2400 polypropylene membrane;

[0073] Counter electrode: Lithium metal sheet. Example 1

[0074] The preparation method of the binder for the silicon negative electrode material in this example includes the following steps:

[0075] (1) Preparation of the acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; measure 10 ml of acrylic acid and add the above sodium hydroxide solution into the acrylic acid to obtain an acrylic acid solution;

[0076] (2) Preparation of the methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution;

[0077] (3) Measure 9.6 ml of acrylonitrile;

[0078] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%.

[0079] (5) Respectively, use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully expel air (subsequently, keep the stirring speed at 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to draw 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Keep the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN).

[0080] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), while adding and stirring, adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN). The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 499523, and the solid content in the second mixed solution is 17.5%.

[0081] (7) Take 10 g of the second mixed solution, 3.5 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60000) solution, and 56.5 g of deionized water and place them in the same container; at this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing P(AA-MA-AN)coPEI adhesive.

[0082] Directly use the solution containing P(AA-MA-AN)coPEI adhesive obtained in step (7) of this example as the silicon negative electrode material adhesive. According to the solid mass ratio of 8:1:1, take nano-silicon powder, Super P, and the silicon negative electrode material adhesive and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps for charge and discharge testing; after the obtained coin-type half-cell is cycled 200 times in the test system, its capacity retention rate is 93%, indicating that the electrode material has a stable structure during long-term cycling and no obvious capacity decay; characterize its surface by scanning electron microscopy, and the result is as Figure 1 described in (a) of, it can be seen that the electrode structure is intact before and after cycling and no rupture occurs; perform a 180° peel test with a universal testing machine, test parameters: length: 16 mm, width: 24 mm; lap area: 384 mm 2 , obtain the highest fracture load and calculate the bonding strength to be 1.27 Mpa, indicating that the binder is firmly bonded to the current collector (copper foil).

[0083] After the cycling experiment, the cycled battery was disassembled in a glove box under vacuum, and the electrode materials were collected. The collected electrodes were immersed in a sodium hydroxide solution (pH = 13), heated and stirred for 5 hours to dissolve the copper foil, and the current collector copper foil immediately fell off. The solid mixture obtained after filtration was a mixture of silicon and Super P. After calculation, the total material recovery rate of silicon and Super P was 78.3%.

[0084] The infrared spectra of PEI, P(AA-MA-AN), and P(AA-MA-AN)coPEI binders in this example were characterized respectively, and the results are shown in Figure 2 ; Figure 2 In the spectrum of P(AA-MA-AN), a broad absorption band at 3130 cm −1 was observed, corresponding to the O-H stretching vibration, while the strong peak at 1724 cm −1 was attributed to the C=O stretching vibration in -COOH. In the spectrum of P(AA-MA-AN)coPEI, the broad absorption band of the O-H stretching vibration at 3130 cm −1 disappeared, and the C=O stretching vibration of PAA at 1724 cm −1 shifted to 1548 cm −1 , which was the result of the ionic interaction of forming ammonium carboxylate between carboxylate ions and ammonium ions, indicating the successful synthesis of the P(AA-MA-AN)coPEI binder.

[0085] Comparative Example 1

[0086] The preparation method of the silicon negative electrode material binder in this comparative example includes the following steps:

[0087] (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution. Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution;

[0088] (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution;

[0089] (3) Measure 9.6 ml of acrylonitrile;

[0090] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%;

[0091] (5) Respectively, use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully expel air (subsequently, maintain the stirring speed at 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Maintain the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN);

[0092] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) into the first mixed solution obtained in step (5), stirring while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 499523, and the solid content in the second mixed solution is 17.5%;

[0093] Take the first mixed solution containing P(AA-MA-AN) obtained in step (6) of this comparative example as the silicon negative electrode material binder. According to the solid mass ratio of 8:1:1, take nano-silicon powder, Super P, and the silicon negative electrode material binder and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps for charge and discharge testing; After the obtained coin-type half-cell is cycled 200 times in the test system, its capacity retention rate is 75%, which is significantly lower than that of Example 1 (93%); Characterize its surface by scanning electron microscopy, and the results are as Figure 1 described in (g) of, it can be seen that there are obvious cracks on the electrode after cycling. Comparing the battery cycle performance test and SEM characterization results of the coin-type half-cell fabricated with the P(AA-MA-AN)coPEI binder in Example 1, it can be clearly concluded that in the case of PEI cross-linking, due to the formed reversible cross-linking reaction, the binder can better maintain the integrity of the electrode during charge and discharge, thereby improving the cycle life of the electrode.

[0094] After the cycling experiment is completed, disassemble the cycled battery in a vacuum glove box and collect the electrode material; Immerse the collected electrode in a sodium hydroxide solution (pH = 13), heat and stir for 5 hours to dissolve the copper foil, and the current collector copper foil will immediately fall off. The solid mixture obtained after filtration is a mixture of silicon and Super P. After calculation, the total material recovery rate of silicon and Super P is 42.5%, which is significantly lower than that of Example 1 (78.3%). Example 2

[0095] The preparation method of the silicon negative electrode material binder in this example includes the following steps:

[0096] Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; measure 8 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution;

[0097] Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, then add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution;

[0098] (3) Measure 12 ml of acrylonitrile;

[0099] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%;

[0100] (5) Respectively use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and fill with nitrogen three times to fully discharge the air (subsequently, keep the stirring speed at 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to suck 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Keep the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN);

[0101] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 442448, and the solid content in the second mixed solution is 14.6%;

[0102] (7) Take 10 g of the second mixed solution, 2.92 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60000) solution, and 45.48 g of deionized water and place them in the same container; At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; Mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing P(AA-MA-AN)coPEI adhesive.

[0103] Directly use the solution containing P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the binder for silicon anode material. Take nano-silicon powder, Super P, and the silicon anode material binder according to a solid mass ratio of 8:1:1, and fabricate a coin-type half-cell according to the aforementioned preparation steps of the coin-type half-cell, and conduct charge and discharge tests. After the obtained coin-type half-cell is cycled 200 times in the test system, its capacity retention rate is 86%, indicating that the electrode material has a stable structure during long-term cycling and no obvious capacity decay. Characterize its surface by scanning electron microscopy, and the results are as Figure 1 described in (b) of 2 , it can be seen that the electrode structure is intact before and after cycling, and no rupture occurs. Conduct a 180° peel test through a universal testing machine, with test parameters: length: 16 mm, width: 24 mm; lap area: 384 mm

[0104] After the cycling experiment is completed, disassemble the cycled battery in a vacuum glove box and collect the electrode material. Immerse the collected electrode in sodium hydroxide solution (pH = 13), heat and stir for 5 hours to dissolve the copper foil, and the current collector copper foil will immediately fall off. The solid mixture obtained after filtration is a mixture of silicon and Super P. After calculation, the total material recovery rate of silicon and Super P is 71.7%. Example 3

[0105] The preparation method of the silicon anode material binder in this example includes the following steps:

[0106] Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution. Measure 12.5 ml of acrylic acid, and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution;

[0107] Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution;

[0108] (3) Measure 7.68 ml of acrylonitrile;

[0109] Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%;

[0110] (5) Respectively, use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully discharge air (subsequently, keep the stirring speed at 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Keep the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN).

[0111] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN). The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 578075, and the solid content in the second mixed solution is 19.2%.

[0112] (7) Take 10 g of the second mixed solution, 3.84 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60000) solution, and 62.69 g of deionized water and place them in the same container. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1. Mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI binder.

[0113] Directly use the solution containing the P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the binder for the silicon negative electrode material. Take nano-silicon powder, Super P, and the silicon negative electrode material binder according to a solid mass ratio of 8:1:1 and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps for charge and discharge testing. After the obtained coin-type half-cell is cycled 200 times in the test system, its capacity retention rate is 81%, indicating that the electrode material has a stable structure during long-term cycling and no obvious capacity decay. Characterize its surface by scanning electron microscopy, and the result is as described in (c) of Figure 1 It can be seen that the electrode structure is intact before and after cycling without rupture. Perform a 180° peel test with a universal testing machine. Test parameters: length: 16 mm, width: 24 mm; lap area: 384 mm 2 , obtain the highest fracture load and calculate the bonding strength to be 1.41 Mpa, indicating that the binder is firmly bonded to the current collector (copper foil).

[0114] After the cycling experiment, the cycled battery was disassembled in a vacuum glove box, and the electrode materials were collected. The collected electrodes were immersed in a sodium hydroxide solution (pH = 13), heated and stirred for 5 hours to dissolve the copper foil, and the current collector copper foil immediately fell off. The solid mixture obtained after filtration was a mixture of silicon and Super P. After calculation, the total material recovery rate of silicon and Super P was 69.1%.

[0115] The test results of the battery cycling performance, peel strength and recovery rate in Examples 1 to 3 are summarized in Table 1.

[0116] Table 1. Cycling performance, peel strength and recovery rate of Examples 1 to 3

[0117]

[0118] It can be seen from Table 1 that in the preparation of the P(AA-MA-AN)coPEI binder, due to the higher polymerization activity of acrylic acid, when the molar ratio of acrylic acid increases, the bonding strength will increase. However, the lack of ionic conductivity provided by acrylonitrile will not continuously enhance the electrical performance of the electrode. At the same time, the increase in the molar ratio of acrylic acid will also lead to a decrease in the recovery rate of the active material. Therefore, in the present invention, when the molar ratio of acrylic acid to acrylonitrile is 1:1, the optimal effect is presented. Example 4

[0119] The preparation method of the silicon negative electrode material binder in this example includes the following steps:

[0120] (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution. Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution.

[0121] (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and dissolve it with 71.54 ml of deionized water to obtain a methyl acrylate solution.

[0122] (3) Measure 9.6 ml of acrylonitrile.

[0123] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%.

[0124] (5) Inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and acrylonitrile obtained in step (3) into the flask through a rubber stopper using a syringe. At a stirring speed of 250 rpm, evacuate and refill with nitrogen three times to fully discharge air (subsequently, maintain the stirring speed at 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to suck 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Keep the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN).

[0125] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stirring while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN). The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 499523, and the solid content in the second mixed solution is 17.5%.

[0126] (7) Take 10 g of the second mixed solution, 2.8 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60000) solution, and 50.2 g of deionized water and place them in the same container. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:0.8. Mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI binder.

[0127] Directly use the solution containing the P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the binder for the silicon anode material. Take nano-silicon powder, Super P, and the silicon anode material binder in a solid mass ratio of 8:1:1 and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps for charge and discharge testing. After the obtained coin-type half-cell is cycled 200 times in the test system, its capacity retention rate is 84%, indicating that the electrode material has a stable structure during long-term cycling and no obvious capacity decay. Characterize its surface by scanning electron microscopy, and the result is as Figure 1 described in (d) of the figure. It can be seen that the electrode structure is intact before and after cycling, and no rupture occurs. Conduct a 180° peel test using a universal testing machine. Test parameters: length: 16 mm, width: 24 mm; lap area: 384 mm 2 , obtain the highest fracture load and calculate the bonding strength to be 0.94 Mpa, indicating that the binder is firmly bonded to the current collector (copper foil).

[0128] After the cycling experiment, the cycled battery was disassembled in a glove box under vacuum, and the electrode materials were collected. The collected electrodes were immersed in a sodium hydroxide solution (pH = 13), heated and stirred for 5 hours to dissolve the copper foil, and the current collector copper foil immediately fell off. The solid mixture obtained after filtration was a mixture of silicon and Super P. After calculation, the total material recovery rate of silicon and Super P was 75.6%. Example 5

[0129] The preparation method of the silicon negative electrode material binder in this example includes the following steps:

[0130] (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution. Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution;

[0131] (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution;

[0132] (3) Measure 9.6 ml of acrylonitrile;

[0133] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%;

[0134] (5) Use syringes to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper respectively. Under a stirring speed of 250 rpm, evacuate and fill with nitrogen three times to fully discharge the air (subsequently, keep the stirring speed at 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to suck 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Keep the reaction temperature at 70 °C and react for 5 h to obtain a first mixed solution containing P(AA-MA-AN);

[0135] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN). The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 499523, and the solid content in the second mixed solution is 17.5%;

[0136] (7) Take 10 g of the second mixed solution, 4.2 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60,000) solution, and 62.8 g of deionized water and place them in the same container; at this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1.2; mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI binder.

[0137] Directly use the solution containing the P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the binder for the silicon negative electrode material. Take nano-silicon powder, Super P, and the silicon negative electrode material binder according to a solid mass ratio of 8:1:1 and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps for charge and discharge testing; after the obtained coin-type half-cell is cycled 200 times in the test system, its capacity retention rate is 90%, indicating that the electrode material has a stable structure during long-term cycling and no obvious capacity decay; characterize its surface by scanning electron microscopy, and the results are as Figure 1 described in (e) of, it can be seen that the electrode structure is intact before and after cycling and no rupture occurs; perform a 180° peel test using a universal testing machine, test parameters: length: 16 mm, width: 24 mm; lap area: 384 mm 2 , obtain the highest fracture load and calculate the bonding strength to be 1.15 Mpa, indicating that the binder is firmly bonded to the current collector (copper foil).

[0138] After the cycling experiment is completed, disassemble the cycled battery in a vacuum glove box and collect the electrode material; immerse the collected electrode in a sodium hydroxide solution (pH = 13), heat and stir for 5 hours to dissolve the copper foil, and the current collector copper foil will immediately fall off. The solid mixture obtained after filtration is a mixture of silicon and Super P. After calculation, the total material recovery rate of silicon and Super P is 79.8%. Example 6

[0139] The preparation method of the binder for the silicon negative electrode material in this example includes the following steps:

[0140] (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide, dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution;

[0141] (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution;

[0142] (3) Measure 9.6 ml of acrylonitrile;

[0143] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%.

[0144] (5) Respectively, use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully discharge air (subsequently, keep the stirring speed at 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Keep the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN).

[0145] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN). The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 499523, and the solid content in the second mixed solution is 17.5%.

[0146] (7) Take 10 g of the second mixed solution, 4.9 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60000) solution, and 69.1 g of deionized water and place them in the same container. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1.4. Mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI binder.

[0147] Directly use the solution containing the P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the binder for the silicon negative electrode material. According to the solid mass ratio of 8:1:1, take nano-silicon powder, Super P, and the silicon negative electrode material binder and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps for charge and discharge testing. After the obtained coin-type half-cell is cycled 200 times in the test system, its capacity retention rate is 87%, indicating that the electrode material has a stable structure during long-term cycling and no obvious capacity decay. Characterize its surface by scanning electron microscopy, and the result is as Figure 1 described in (f) of, and it can be seen that the electrode structure is intact before and after cycling and no rupture occurs. Conduct a 180° peel test with a universal testing machine. Test parameters: length: 16 mm, width: 24 mm; lap area: 384 mm 2 , obtain the highest fracture load and calculate the bonding strength to be 1.09 Mpa, indicating that the binder is firmly bonded to the current collector (copper foil).

[0148] After the cycling experiment, the cycled battery was disassembled in a vacuum glove box, and the electrode materials were collected. The collected electrodes were immersed in a sodium hydroxide solution (pH = 13), heated and stirred for 5 hours to dissolve the copper foil, and the current collector copper foil immediately fell off. The solid mixture obtained after filtration was a mixture of silicon and Super P. After calculation, the total material recovery rate of silicon and Super P was 75.4%.

[0149] The test results of the battery cycling performance, peel strength and recovery rate in Examples 1, 4 to 6 are summarized in Table 2.

[0150] Table 2. Cycling performance, peel strength and recovery rate of Examples 1, 4 to 6

[0151]

[0152] The change diagram of the capacity retention rate of Examples 1, 4 to 6 after 200 cycles is shown in Figure 3 Observing Table 2 and Figure 3 it can be found that when the mass ratio of P(AA-MA-AN) to PEI is 1:(0.8 - 1.4), the synthesized P(AA-MA-AN)coPEI adhesives can greatly improve the battery cycling performance. And when the content of PEI increases, the recovery rate of active substances increases to a certain extent. However, after exceeding 1:1, the bonding strength begins to decline, and the capacity retention rate will also decline accordingly. Example 7

[0153] The preparation method of the silicon negative electrode material adhesive in this example includes the following steps:

[0154] (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution. Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution;

[0155] (2) Preparation of methyl acrylate solution: Measure 6.92 ml of methyl acrylate and add it to a flask, and dissolve it with 68.08 ml of deionized water to obtain a methyl acrylate solution;

[0156] (3) Measure 9.6 ml of acrylonitrile;

[0157] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%;

[0158] (5) Inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and acrylonitrile obtained in step (3) into the flask through a rubber stopper using a syringe. At a stirring speed of 250 rpm, evacuate and refill with nitrogen three times to fully expel air (subsequently, maintain the stirring speed at 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to draw 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Maintain the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN).

[0159] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stirring while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN). The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 511634, and the solid content in the second mixed solution is 17.9%.

[0160] (7) Take 10 g of the second mixed solution, 3.58 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60000) solution, and 56.5 g of deionized water and place them in the same container. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1. Mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI binder.

[0161] Then, use the solution containing the P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the binder for the silicon negative electrode material. Take nano-silicon powder, Super P, and the silicon negative electrode material binder according to a solid mass ratio of 8:1:1 and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps. Subsequently, perform charge-discharge tests, peel tests, and electrode material recovery according to the same test methods as in Example 1. The cycle performance, peel strength, and recovery rate are shown in Table 3. Example 8

[0162] The preparation method of the binder for the silicon negative electrode material in this example includes the following steps:

[0163] (1) Preparation of the acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution. Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution.

[0164] (2) Preparation of the methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution.

[0165] (3) Measure 9.6 ml of acrylonitrile;

[0166] (4) Preparation of the initiator solution: Weigh 25 mg of ammonium persulfate, dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%;

[0167] (5) Respectively use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and fill with nitrogen three times to fully expel air (subsequently, always maintain a stirring speed of 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Maintain the reaction temperature at 70 °C for 6 h to obtain a first mixed solution containing P(AA-MA-AN);

[0168] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 512213, and the solid content in the second mixed solution is 18.1%;

[0169] (7) Take 10 g of the second mixed solution, 3.62 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60000) solution, and 58.78 g of deionized water and place them in the same container; At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; Mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI binder.

[0170] Directly use the solution containing the P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the binder for the silicon negative electrode material. Take nano-silicon powder, Super P, and the silicon negative electrode material binder according to a solid mass ratio of 8:1:1 and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps. Subsequently, conduct charge-discharge tests, peel tests, and electrode material recovery according to the same test methods as in Example 1. The cycle performance, peel strength, and recovery rate are shown in Table 3. Example 9

[0171] The preparation method of the binder for the silicon negative electrode material in this example includes the following steps:

[0172] (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution;

[0173] (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, then add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution;

[0174] (3) Measure 9.6 ml of acrylonitrile;

[0175] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%;

[0176] (5) Use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper respectively. Under a stirring speed of 250 rpm, evacuate and fill with nitrogen three times to fully discharge the air (subsequently, keep the stirring speed at 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to suck 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Keep the reaction temperature at 70 °C for 7 h to obtain a first mixed solution containing P(AA-MA-AN);

[0177] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 526948, and the solid content in the second mixed solution is 18.6%;

[0178] (7) Take 10 g of the second mixed solution, 3.72 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60000) solution, and 60.68 g of deionized water and place them in the same container; At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; Mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing P(AA-MA-AN)coPEI adhesive.

[0179] Directly use the solution containing the P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the binder for the silicon negative electrode material. Take nano-silicon powder, Super P, and the silicon negative electrode material binder according to a solid mass ratio of 8:1:1, and fabricate a button-type half-cell according to the aforementioned preparation steps of the button-type half-cell. Subsequently, perform charge-discharge tests, peeling tests, and electrode material recovery according to the same test method as in Example 1. The cycle performance, peeling strength, and recovery rate are shown in Table 3. Example 10

[0180] The preparation method of the binder for the silicon negative electrode material in this example includes the following steps:

[0181] (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution;

[0182] (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution;

[0183] (3) Measure 9.6 ml of acrylonitrile;

[0184] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%;

[0185] (5) Use syringes to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and fill with nitrogen three times to fully discharge the air (subsequently, always maintain a stirring speed of 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 70 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction, and maintain the reaction temperature at 70 °C for 8 h to obtain a first mixed solution containing P(AA-MA-AN);

[0186] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 545579, and the solid content in the second mixed solution is 20.2%;

[0187] (7) Take 10 g of the second mixed solution, 4.04 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60,000) solution, and 66.76 g of deionized water and place them in the same container; at this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI binder.

[0188] Directly use the solution containing the P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the silicon negative electrode material binder. Take nano-silicon powder, Super P, and the silicon negative electrode material binder according to a solid mass ratio of 8:1:1 and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps. Subsequently, perform charge and discharge tests, peeling tests, and electrode material recovery according to the same test method as in Example 1. The cycling performance, peeling strength, and recovery rate are shown in Table 3. Example 11

[0189] The preparation method of the silicon negative electrode material binder in this example includes the following steps:

[0190] (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution;

[0191] (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution;

[0192] (3) Measure 9.6 ml of acrylonitrile;

[0193] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%;

[0194] (5) Use syringes to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and fill with nitrogen three times to fully discharge the air (subsequently, always maintain a stirring speed of 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 75 °C, use a syringe to draw 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Keep the reaction temperature at 75 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN);

[0195] (6) Add sodium hydroxide solution with the same concentration as in step (1) dropwise to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); the weight-average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 497217, and the solid content in the second mixed solution is 17.2%;

[0196] (7) Take 10 g of the second mixed solution, 3.44 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60000) solution, and 55.36 g of deionized water and place them in the same container; at this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI binder.

[0197] Directly use the solution containing the P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the silicon anode material binder, take nano-silicon powder, Super P, and the silicon anode material binder according to a solid mass ratio of 8:1:1, and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps. Subsequently, perform charge-discharge tests, peeling tests, and electrode material recovery according to the same test methods as in Example 1. The cycle performance, peeling strength, and recovery rate are shown in Table 3. Example 12

[0198] The preparation method of the silicon anode material binder in this example includes the following steps:

[0199] (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution;

[0200] (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution;

[0201] (3) Measure 9.6 ml of acrylonitrile;

[0202] (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%;

[0203] (5) Inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through the rubber stopper using a syringe. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully expel air (subsequently, maintain the stirring speed at 250 rpm until the reaction ends). Heat the flask. When the internal temperature reaches 80 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate the free radical polymerization reaction. Keep the reaction temperature at 80 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN).

[0204] (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stirring while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN). The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 469422, and the solid content in the second mixed solution is 16.7%.

[0205] (7) Take 10 g of the second mixed solution, 3.34 g of a 50 wt% PEI (branched polyethyleneimine with a molecular weight of 60000) solution, and 55.36 g of deionized water and place them in the same container. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1. Mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI binder.

[0206] Directly use the solution containing the P(AA-MA-AN)coPEI binder obtained in step (7) of this example as the binder for the silicon anode material. Take nano-silicon powder, Super P, and the silicon anode material binder according to a solid mass ratio of 8:1:1 and fabricate a coin-type half-cell according to the aforementioned coin-type half-cell preparation steps. Subsequently, perform charge and discharge tests, peel tests, and electrode material recovery according to the same test methods as in Example 1. The cycle performance, peel strength, and recovery rate are shown in Table 3.

[0207] Table 3. Cycle performance, peel strength, and recovery rate of Examples 7 - 12

[0208]

[0209] In summary, the silicon anode material adhesives prepared by the preparation method of the silicon anode material adhesive of the present invention can all significantly improve the cycle life and stability of the battery, so that the capacity retention rate of the battery is ≥81% after 200 cycles at a current density of 0.5C, and the electrode is intact before and after cycling without cracking; based on the response characteristics of the P(AA-MA-AN)coPEI adhesive, the active substances in the waste battery materials are recovered by alkali solution washing: the electrode sheet is treated with alkali solution, and the recovery rate of the electrode active substances is ≥70%.

[0210] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation method of a silicon anode material binder, characterized in that, It includes the following steps: (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution; (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and dissolve it with 71.54 ml of deionized water to obtain a methyl acrylate solution; (3) Measure 9.6 ml of acrylonitrile; (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%; (5) Inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper with a syringe respectively. Under a stirring speed of 250 rpm, evacuate and fill with nitrogen three times to fully discharge the air. Subsequently, keep the stirring speed at 250 rpm until the reaction ends; Heat the flask. When the internal temperature reaches 70 °C, suck 3.75 ml of the ammonium persulfate solution prepared in step (4) with a syringe to initiate a free radical polymerization reaction, and keep the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN); (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); The weight average molecular weight of P(AA-MA-AN) is measured to be 499523 by gel permeation chromatography (GPC), and the solid content in the second mixed solution is 17.5%; (7) Take 10 g of the second mixed solution, 3.5 g of a 50 wt% PEI solution, and 56.5 g of deionized water and place them in the same container; PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; Mix and stir at room temperature of 25 °C for 30 min to obtain a solution containing P(AA-MA-AN)coPEI adhesive.

2. A preparation method of an adhesive for silicon anode materials, characterized in that, It includes the following steps: (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; Measure 8 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution; (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and dissolve it with 71.54 ml of deionized water to obtain a methyl acrylate solution; (3) Measure 12 ml of acrylonitrile; (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%; (5) Respectively use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully discharge the air. Subsequently, maintain the stirring speed at 250 rpm until the reaction ends. Heat the flask. When the internal temperature reaches 70 °C, use a syringe to suck 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate the free radical polymerization reaction. Keep the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN). (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN). The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 442448, and the solid content in the second mixed solution is 14.6%. (7) Take 10 g of the second mixed solution, 2.92 g of a 50 wt% PEI solution, and 45.48 g of deionized water and place them in the same container. PEI is a branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:

1. Mix and stir at room temperature of 25 °C for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI adhesive.

3. A preparation method of an adhesive for silicon anode materials, characterized in that, It includes the following steps: Preparation of the acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution. Measure 12.5 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution. Preparation of the methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to the flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution. (3) Measure 7.68 ml of acrylonitrile. (4) Preparation of the initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%. (5) Respectively use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully discharge the air. Subsequently, maintain the stirring speed at 250 rpm until the reaction ends. Heat the flask. When the internal temperature reaches 70 °C, use a syringe to suck 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate the free radical polymerization reaction. Keep the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN). (6) Add sodium hydroxide solution with the same concentration as in step (1) dropwise into the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); the weight-average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography GPC is 578075, and the solid content in the second mixed solution is 19.2%; (7) Take 10 g of the second mixed solution, 3.84 g of 50 wt% PEI solution, and 62.69 g of deionized water and place them in the same container; PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; mix and stir at room temperature of 25 °C for 30 min to obtain a solution containing P(AA-MA-AN)coPEI adhesive.

4. A preparation method of a binder for a silicon-based anode material, characterized in that, (8) The method includes the following steps: (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide, dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; measure 10 ml of acrylic acid, and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution; (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution; (3) Measure 9.6 ml of acrylonitrile; (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate, dissolve it in 5 ml of deionized water, and prepare an ammonium persulfate solution with a concentration of 0.5 wt%; (5) Inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper with a syringe respectively. Under a stirring speed of 250 rpm, evacuate and fill with nitrogen three times to fully discharge the air. Subsequently, keep the stirring speed at 250 rpm until the reaction ends; heat the flask. When the internal temperature reaches 70 °C, suck 3.75 ml of the ammonium persulfate solution prepared in step (4) with a syringe to initiate a free radical polymerization reaction, and keep the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN); (6) Add sodium hydroxide solution with the same concentration as in step (1) dropwise into the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); the weight-average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography GPC is 499523, and the solid content in the second mixed solution is 17.5%; (7) Take 10 g of the second mixed solution, 2.8 g of 50 wt% PEI solution, and 50.2 g of deionized water and place them in the same container; PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:0.8; mix and stir at room temperature of 25 °C for 30 min to obtain a solution containing P(AA-MA-AN)coPEI adhesive.

5. A preparation method of an adhesive for silicon negative electrode materials, characterized in that, (8) The method includes the following steps: (1)Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution; (2)Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, then add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution; (3)Measure 9.6 ml of acrylonitrile; (4)Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%; (5)Respectively use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully discharge the air. Subsequently, keep the stirring speed at 250 rpm until the reaction ends; Heat the flask. When the internal temperature reaches 70 °C, use a syringe to suck 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Keep the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN); (6)Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); The weight average molecular weight of P(AA-MA-AN) is measured to be 499523 by gel permeation chromatography GPC, and the solid content in the second mixed solution is 17.5%; (7)Take 10 g of the second mixed solution, 4.2 g of a 50 wt% PEI solution, and 62.8 g of deionized water and place them in the same container; PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1.2; Mix and stir at room temperature of 25 °C for 30 min to obtain a solution containing P(AA-MA-AN)coPEI adhesive.

6. A preparation method of a binder for silicon-based anode materials, characterized in that, Including the following steps: (1)Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution; (2)Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, then add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution; (3)Measure 9.6 ml of acrylonitrile; (4)Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%; (5) Respectively use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully discharge the air. Subsequently, continuously maintain the stirring speed at 250 rpm until the reaction ends. Heat the flask. When the internal temperature reaches 70 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Maintain the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN); (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN). The weight average molecular weight of P(AA-MA-AN) is measured to be 499523 by gel permeation chromatography (GPC), and the solid content in the second mixed solution is 17.5%; (7) Take 10 g of the second mixed solution, 4.9 g of a 50 wt% PEI solution, and 69.1 g of deionized water and place them in the same container. PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1.

4. Mix and stir at room temperature of 25 °C for 30 min to obtain a solution containing the P(AA-MA-AN)coPEI adhesive.

7. A preparation method of a silicon anode material binder, characterized in that, The method comprises the following steps: (1) Preparation of the acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution. Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution; (2) Preparation of the methyl acrylate solution: Measure 6.92 ml of methyl acrylate and add it to the flask, and add 68.08 ml of deionized water to dissolve it to obtain a methyl acrylate solution; (3) Measure 9.6 ml of acrylonitrile; (4) Preparation of the initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%; (5) Respectively use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully discharge the air. Subsequently, continuously maintain the stirring speed at 250 rpm until the reaction ends. Heat the flask. When the internal temperature reaches 70 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Maintain the reaction temperature at 70 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN); (6) Add sodium hydroxide solution with the same concentration as that in step (1) dropwise into the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); the weight-average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography GPC is 511634, and the solid content in the second mixed solution is 17.9%; (7) Take 10 g of the second mixed solution, 3.58 g of 50 wt% PEI solution, and 56.5 g of deionized water and place them in the same container; PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; mix and stir at room temperature of 25 °C for 30 min to obtain a solution containing P(AA-MA-AN)coPEI adhesive.

8. A preparation method of a silicon negative electrode material binder, characterized in that, It includes the following steps: (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution; (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution; (3) Measure 9.6 ml of acrylonitrile; (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%; (5) Inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper with a syringe respectively. Under a stirring speed of 250 rpm, evacuate and refill nitrogen three times to fully discharge the air. Subsequently, keep the stirring speed at 250 rpm until the reaction ends; heat the flask. When the internal temperature reaches 70 °C, suck 3.75 ml of the ammonium persulfate solution prepared in step (4) with a syringe to initiate a free radical polymerization reaction, and keep the reaction temperature at 70 °C for 6 h to obtain a first mixed solution containing P(AA-MA-AN); (6) Add sodium hydroxide solution with the same concentration as that in step (1) dropwise into the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); the weight-average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography GPC is 512213, and the solid content in the second mixed solution is 18.1%; (7) Take 10 g of the second mixed solution, 3.62 g of 50 wt% PEI solution, and 58.78 g of deionized water and place them in the same container; PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; mix and stir at room temperature of 25 °C for 30 min to obtain a solution containing P(AA-MA-AN)coPEI adhesive.

9. A preparation method of a binder for a silicon anode material, characterized in that, (8) It includes the following steps: (1)Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution; (2)Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, then add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution; (3)Measure 9.6 ml of acrylonitrile; (4)Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%; (5)Respectively use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and fill with nitrogen three times to fully discharge the air. Subsequently, maintain the stirring speed at 250 rpm until the reaction ends; Heat the flask. When the internal temperature reaches 70 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Keep the reaction temperature at 70 °C for 7 h to obtain a first mixed solution containing P(AA-MA-AN); (6)Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography GPC is 526948, and the solid content in the second mixed solution is 18.6%; (7)Take 10 g of the second mixed solution, 3.72 g of a 50 wt% PEI solution, and 60.68 g of deionized water and place them in the same container; PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; Mix and stir at room temperature of 25 °C for 30 min to obtain a solution containing P(AA-MA-AN)coPEI adhesive.

10. A preparation method of a binder for a silicon-based anode material, characterized in that, Including the following steps: (1)Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution; (2)Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, then add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution; (3)Measure 9.6 ml of acrylonitrile; (4)Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%; (5) Respectively use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill with nitrogen three times to fully discharge the air. Subsequently, continuously maintain the stirring speed at 250 rpm until the reaction ends. Heat the flask. When the internal temperature reaches 70 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Maintain the reaction temperature at 70 °C and react for 8 h to obtain a first mixed solution containing P(AA-MA-AN). (6) Dropwise add the sodium hydroxide solution with the same concentration as in step (1) to the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN). The weight average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography (GPC) is 545579, and the solid content in the second mixed solution is 20.2%. (7) Take 10 g of the second mixed solution, 4.04 g of a 50 wt% PEI solution, and 66.76 g of deionized water and place them in the same container. PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:

1. Mix and stir at room temperature of 25 °C for 30 min to obtain a solution containing P(AA-MA-AN) coPEI adhesive.

11. A method for preparing an adhesive for silicon anode materials, characterized in that, It includes the following steps: (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide and dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution. Measure 10 ml of acrylic acid and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution. (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to the flask, and add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution. (3) Measure 9.6 ml of acrylonitrile. (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate and dissolve it in 5 ml of deionized water to prepare an ammonium persulfate solution with a concentration of 0.5 wt%. (5) Respectively use a syringe to inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper. Under a stirring speed of 250 rpm, evacuate and refill with nitrogen three times to fully discharge the air. Subsequently, continuously maintain the stirring speed at 250 rpm until the reaction ends. Heat the flask. When the internal temperature reaches 75 °C, use a syringe to aspirate 3.75 ml of the ammonium persulfate solution prepared in step (4) to initiate a free radical polymerization reaction. Maintain the reaction temperature at 75 °C and react for 5 h to obtain a first mixed solution containing P(AA-MA-AN). (6) Add sodium hydroxide solution with the same concentration as that in step (1) dropwise into the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); the weight-average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography GPC is 497217, and the solid content in the second mixed solution is 17.2%; (7) Take 10 g of the second mixed solution, 3.44 g of 50 wt% PEI solution, and 55.36 g of deionized water and place them in the same container; PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing P(AA-MA-AN) coPEI adhesive.

12. A preparation method of a silicon negative electrode material binder, characterized in that, It includes the following steps: (1) Preparation of acrylic acid solution: Weigh 1.12 g of sodium hydroxide, dissolve it in 10 ml of deionized water to obtain a sodium hydroxide solution; measure 10 ml of acrylic acid, and add the above sodium hydroxide solution to the acrylic acid to obtain an acrylic acid solution; (2) Preparation of methyl acrylate solution: Measure 3.46 ml of methyl acrylate and add it to a flask, add 71.54 ml of deionized water to dissolve it to obtain a methyl acrylate solution; (3) Measure 9.6 ml of acrylonitrile; (4) Preparation of initiator solution: Weigh 25 mg of ammonium persulfate, dissolve it in 5 ml of deionized water, and prepare an ammonium persulfate solution with a concentration of 0.5 wt%; (5) Inject the acrylic acid solution obtained in step (1), the methyl acrylate solution obtained in step (2), and the acrylonitrile obtained in step (3) into the flask through a rubber stopper with a syringe respectively. Under a stirring speed of 250 rpm, evacuate and fill with nitrogen three times to fully discharge the air. Subsequently, keep the stirring speed at 250 rpm until the reaction ends; heat the flask. When the internal temperature reaches 80 °C, suck 3.75 ml of the ammonium persulfate solution prepared in step (4) with a syringe to initiate a free radical polymerization reaction, and keep the reaction temperature at 80 °C for 5 h to obtain a first mixed solution containing P(AA-MA-AN); (6) Add sodium hydroxide solution with the same concentration as that in step (1) dropwise into the first mixed solution obtained in step (5), stir while adding, and adjust the pH of the first mixed solution to 4 to obtain a second mixed solution containing P(AA-MA-AN); the weight-average molecular weight of P(AA-MA-AN) measured by gel permeation chromatography GPC is 469422, and the solid content in the second mixed solution is 16.7%; (7) Take 10 g of the second mixed solution, 3.34 g of 50 wt% PEI solution, and 55.36 g of deionized water and place them in the same container; PEI is branched polyethyleneimine with a molecular weight of 60000. At this time, the mass ratio of P(AA-MA-AN) to PEI is 1:1; mix and stir at room temperature (25 °C) for 30 min to obtain a solution containing P(AA-MA-AN) coPEI adhesive.

13. A binder for silicon anode materials prepared by the preparation method according to any one of claims 1 to 12.

14. An application of the binder for silicon anode materials according to claim 13 in a lithium battery.

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