A silicon-based anode binder with a self-healing dual-channel ion network and its preparation method

Abstract

This invention discloses a silicon-based anode binder with a self-healing dual-ion-conducting network and its preparation method. This aqueous binder uses hydroxyl-rich polyvinyl alcohol as its molecular backbone, providing excellent adhesion. Through acetalization, ether bonds with lithium-ion conduction effects are introduced into the molecular chain. Furthermore, graft polymerization introduces ionic monomers to construct comb-shaped side chains with high bonding strength and reconfigurable fracture properties. The ionic functional groups promote the dissociation of lithium salts and the migration of lithium ions, accelerating lithium-ion conduction. Through these methods, this invention can endow the binder with higher ion-conducting properties and dynamic self-healing function while providing effective adhesion, enabling lithium-ion batteries to possess advantages such as high energy density, long cycle life, and fast charging.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery manufacturing technology, and relates to a silicon-based anode binder with a self-healing dual-conducting ion network and its preparation method. Background Technology

[0002] Lithium-ion batteries, with their high energy density, long cycle life, and environmental friendliness, have gradually become one of the preferred carriers for providing and storing energy. However, with the continuous expansion of applications, the market has placed higher demands on the cycle life and fast-charging performance of lithium-ion batteries. Silicon-based anode materials have ultra-high specific capacity, which can significantly improve the energy density of lithium-ion batteries, but they still face challenges such as excessive volume expansion of active materials and insufficient intrinsic conductivity. Binders play a crucial role in bonding active materials and substrate materials in the anode sheet, and are essential for battery stability and cycle life. To address volume expansion, patent CN110444765A designed a non-dynamic three-dimensional cross-linked binder using chemically cross-linked polyvinyl alcohol. While this can temporarily suppress the volume expansion of active materials, it cannot cope with binder breakage under long-term cycling. Patents CN113782744A, CN114203987A, and CN112680148A all utilize hydrogen bonding between PVA and other component polymers to form a cross-linked network structure to stabilize the battery during long-term cycling, but lack consideration for the conductivity of the binder. Patent CN114242990A utilizes a binder with a three-dimensional interconductive network structure formed by polyvinyl alcohol polymer and acrylic acid-acrylamide-(2-acrylamide-2-methylpropanesulfonic acid) terpolymer. Although the terpolymer has a certain effect on promoting ionic conductivity diffusion, the polyvinyl alcohol remains in a state below lithium ion concentration, which is not conducive to the overall lithium ion diffusion of the electrode. Similarly, in the composite binder system formed by polyvinyl alcohol, polydopamine, and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate aqueous solution (PEDOT:PSS) in patent CN110336037B, polyvinyl alcohol also does not contribute to lithium ion diffusion.

[0003] How to improve the overall performance of the binder, so as to optimize the ion conduction pathway, reduce impedance and improve fast charging performance while ensuring the adhesive strength, and extend the battery cycle life by combining dynamic network characteristics, has become an important problem that needs to be solved. Summary of the Invention

[0004] In view of this, and addressing the limitations of lithium-ion battery applications and the shortcomings in the current development of silicon-based anode materials, this invention focuses on the binder—a crucial component of silicon anode sheets—as a starting point for optimizing battery performance. This invention provides a novel polymer synthesized in a two-step process for use as a binder in aqueous silicon anodes, along with its preparation method. This binder possesses a strong dynamic repair network and exhibits dual ion-conducting effects. The dynamic repair characteristic allows the binder to better adapt to the volume changes of the active material during charge and discharge, while simultaneously acting as a bond to the active material and conductive agent. Under the volume expansion and contraction of the active material, the binder can dissipate energy through the breaking and recombination of dynamic bonds, adapting to and suppressing the volume changes of the active material. This avoids the fragmentation of the active material due to volume changes after multiple charge and discharge cycles, as well as battery electrode failure caused by the slippage and breakage of binder molecules. The main chain and side chains of the polymer binder each possess functional groups with lithium-ion conducting properties, which will improve ionic conductivity by constructing a fast-conducting ion network in the electrode sheet, thus benefiting the battery's rate performance and cycle performance.

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a silicon-based anode binder with a self-healing dual-ion-conducting network. This aqueous binder uses hydroxyl-rich polyvinyl alcohol as its molecular backbone, providing excellent adhesive properties. By acetalization, ether bonds with lithium-ion conduction effects are introduced into the molecular chain. Furthermore, graft polymerization is used to introduce ionic monomers to construct comb-shaped side chains with high bonding strength and recombinability after breakage. The ionic functional groups can promote the dissociation of lithium salts and the migration of lithium ions, thereby accelerating lithium-ion conduction.

[0006] The method of this invention uses polyvinyl alcohol as the main component, introduces ether bonds into the chain segments through acetalization reaction, and then introduces polyionic monomer side chains into the polyvinyl alcohol acetal through graft polymerization reaction.

[0007] Includes the following steps:

[0008] (1) Preparation of polyvinyl acetal adhesive:

[0009] Polyvinyl alcohol (PVA) was added to deionized water and stirred continuously. The temperature was slowly increased until the PVA was completely dissolved, resulting in a PVA aqueous solution. When the temperature reached the first treatment temperature, hydrochloric acid solution was added dropwise to adjust to the first pH value. Then, a quantitative amount of aldehyde solution of a specific concentration was slowly added dropwise and the reaction was maintained at this temperature for a period of time. After the reaction was completed, the pH of the reaction system was adjusted to neutral. When the temperature dropped to the second treatment temperature, an appropriate amount of urea was added to remove unreacted aldehydes. After cooling to room temperature, the reactants were poured off, dialyzed using a dialysis bag, and the polymer solution after dialyzing was freeze-dried for later use. The amount of aldehyde added was 5%–40% of the molar number of hydroxyl groups in the PVA.

[0010] (2) Polyvinyl acetal grafted ionomer:

[0011] The polyvinyl acetalized polymer obtained from the above reaction was redissolved in deionized water. Then, an appropriate amount of initiator was added, the air was purged under vacuum three times, and the reactor was heated to the set reaction temperature. After the temperature stabilized and the system was thoroughly stirred, the monomer solution was slowly added dropwise to initiate the graft polymerization reaction. The reaction was stopped after 6–24 hours (preferably 12 hours). After cooling to room temperature, the reactants were poured off, dialyzed using a dialysis bag, and the dialyzed polymer solution was freeze-dried for later use.

[0012] In the above method, the raw material in step (1) is characterized by polyvinyl alcohol with different degrees of polymerization and hydrolysis having a polyhydroxy structure. Further, the degree of polymerization of the polyvinyl alcohol ranges from 600 to 2500.

[0013] Furthermore, as described above, the degree of hydrolysis of polyvinyl alcohol ranges from 50% to 99%, preferably from 60% to 99%.

[0014] In the above method, the degree of conversion of the hydroxyl group to acetalization using aldehydes in the acetalization reaction is 5% to 50%.

[0015] In the above method, the aldehyde substance has an aldehyde group structure, and the aldehyde group structure includes one or more of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, etc.

[0016] In the above method, the graft polymerization is initiated by an initiator to carry out graft polymerization on the polyvinyl acetal chain, and the mass ratio of the grafting host to the grafting monomer is 10:1 to 1:10; the mass ratio of the initiator to the monomer is 1:1000 to 5:100.

[0017] In the above method, the first processing temperature in step (1) is 50 to 100°C.

[0018] In the above method, the first pH value in step (1) is 1 to 6.

[0019] In the above method, the dropping time in step (1) is 5 to 60 minutes; the reaction time is 1 to 6 hours.

[0020] In the above method, the concentration of the aldehyde solution in step (1) is 5% to 60%.

[0021] As in step (1) above, the mass ratio of polyvinyl alcohol and aldehyde is 5:1 to 20:1.

[0022] Furthermore, the types of aldehydes include, but are not limited to, one or more of formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde.

[0023] As in step (1) above, the second processing temperature is 30 to 70°C.

[0024] As in step (1) above, the second pH value is 7 to 10.

[0025] Furthermore, the alkaline solutions for adjusting pH include, but are not limited to, one or more of LiOH, NaOH, KOH, NaOH, and NH3·H2O.

[0026] As in step (2) above, the reaction temperature is 50-100℃; the dropping time is 5-120 min; and the total reaction time is 1-12 h.

[0027] Furthermore, the initiator includes, but is not limited to, one or more of the following: ammonium persulfate, potassium persulfate, alkali metal persulfate salts (ammonium, potassium)-reducing agents (sodium bisulfite (NaHSO3), sodium sulfite (Na2SO3), sodium thiosulfate (Na2S2O3), oxalic acid, etc.), azobisisobutylamidine hydrochloride (AIBA), azobisisobutylimidazoline hydrochloride (AIBI), azobiscyanopentanoic acid (ACVA), and azobisisopropylimidazoline (AIP).

[0028] As in step (2) above, the monomers include, but are not limited to, one or more of the following: dimethyl diallyl ammonium chloride (DMDAAC), methacryloyloxyethyl trimethyl ammonium chloride (DMC), acryloyloxyethyl trimethyl ammonium chloride (DAC), methacrylamidopropyl trimethyl ammonium chloride (MAPTAC), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), itaconic acid (IA), sodium styrene sulfonate (NaSS), sodium α-olefin sulfonate, 2-methacryloyloxyethyl phosphorylcholine (MPC), carboxybetaine acrylamide (CBAA), methacrylic acid sulfobetaine (SBMA), and methacrylic acid carboxybetaine (CBMA).

[0029] As in step (2) above, the reaction temperature is 50 to 100°C.

[0030] As in step (2) above, the reaction time is 1 to 12 hours.

[0031] As in step (2) above, the mass ratio of the polyvinyl acetalized polymer to the monomer is 10:1 to 1:10.

[0032] A silicon-based anode binder with a self-healing dual-channel ion network was prepared by the above method. This aqueous binder utilizes coordination bonds to form a three-dimensional network structure and exhibits self-healing properties. The reversible dynamic characteristics of these coordination bonds are used to address volume changes in the anode particles during cycling. The breaking of these coordination bonds dissipates the energy from volume expansion, preventing slippage and breakage of the binder molecules.

[0033] Compared with existing technologies, the present invention has the following significant and substantial advantages and features:

[0034] (1) The present invention uses water as the solvent and reaction system carrier, which makes the reaction simple, the product yield high, and has outstanding advantages such as environmental friendliness and low production process cost.

[0035] (2) The flexible nature of the polyvinyl alcohol backbone and the beneficial adhesion provided by the hydroxyl groups, along with the introduction of abundant ether bonds through the acetalization of the hydroxyl groups, enhance the affinity for the electrolyte and promote the dissociation of ion pairs and the transfer of lithium ions in the lithium salt.

[0036] (3) By grafting ionic monomers onto hydroxyl active sites, high-bond-energy, dynamically reversible coordination bonds are obtained, redistributing the charge density distribution of side groups, enhancing intermolecular forces, and constructing a highly entangled dynamic three-dimensional cross-linked network. The numerous ionic functional groups on the molecular side chains construct a rapid pathway for lithium ion movement through electrostatic interactions and chain segment motion.

[0037] The advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the embodiments thereof. Attached Figure Description

[0038] Figure 1 This is a Coulomb efficiency diagram;

[0039] Figure 2 This is a cyclic data graph. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the invention clearer, the technical solutions will be described more clearly and in detail below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the protection scope of the present invention.

[0041] Example 1

[0042] (1) Preparation of polyvinyl alcohol formaldehyde adhesive:

[0043] 10g of polyvinyl alcohol (1799) was added to 100g of deionized water and stirred continuously. The temperature was slowly raised to 90℃ and maintained for 1 hour to completely dissolve the polyvinyl alcohol, resulting in a polyvinyl alcohol aqueous solution. The temperature was adjusted to 85℃, and dilute hydrochloric acid solution (0.1mol / L) was added dropwise to adjust the pH to approximately 2.5. 3.5g of formaldehyde aqueous solution (35wt%) was slowly added dropwise over 30 minutes, and the reaction was maintained at this temperature for 120 minutes. After the reaction was completed, the reaction system was neutralized to a pH of approximately 7 using sodium hydroxide solution (1wt%). The temperature was lowered to 60℃, and 1.5g of urea was added. The reaction was carried out for 30 minutes to remove unreacted formaldehyde. After cooling to room temperature, the reaction mixture was poured out, dialyzed using a dialysis bag, and the polymer solution after dialyzing was freeze-dried for later use.

[0044] (2) Polyvinyl alcohol formaldehyde grafted ionomer:

[0045] 10g of the polyvinyl alcohol acetalized polymer obtained from the above reaction was redissolved in 100g of deionized water. 0.1g of potassium persulfate was added to the reactor containing the polyvinyl alcohol acetal polymer solution. The reactor was purged with nitrogen three times under vacuum and then purged for 30 minutes. The temperature was then raised to 75°C. After the temperature stabilized and the system was thoroughly stirred, 3g of methacrylic acid sulfobetaine was slowly added dropwise over a period of 30 minutes to initiate the graft polymerization reaction. The reaction was stopped after 12 hours. After cooling to room temperature, the reactants were poured off, dialyzed using a dialysis bag, and the dialyzed polymer solution was freeze-dried for later use.

[0046] Example 2

[0047] This embodiment is basically the same as Embodiment 1, except that the amount of formaldehyde and the acetalization time are controlled to regulate the amount of ether bonds introduced into the main chain of polyvinyl alcohol.

[0048] (1) Preparation of polyvinyl alcohol formaldehyde adhesive:

[0049] 10g of polyvinyl alcohol (1799) was added to 100g of deionized water and stirred continuously. The temperature was slowly raised to 90℃ and maintained for 1 hour to completely dissolve the polyvinyl alcohol, resulting in a polyvinyl alcohol aqueous solution. The temperature was adjusted to 85℃, and dilute hydrochloric acid solution (0.1mol / L) was added dropwise to adjust the pH to approximately 2.5. 2g of formaldehyde aqueous solution (35wt%) was slowly added dropwise over 30 minutes, and the reaction was maintained at this temperature for 60 minutes. After the reaction was complete, the reaction system was neutralized to approximately pH 7 using sodium hydroxide solution (1wt%). The temperature was lowered to 60℃, and 1.5g of urea was added. The reaction was carried out for 30 minutes to remove unreacted formaldehyde. After cooling to room temperature, the reaction mixture was poured out, dialyzed using a dialysis bag, and the resulting polymer solution was freeze-dried for later use.

[0050] (2) Polyvinyl alcohol formaldehyde grafted ionomer:

[0051] 10g of the polyvinyl alcohol formaldehyde polymer obtained from the above reaction was redissolved in 100g of deionized water. 0.2g of potassium persulfate was added to the reactor containing the polyvinyl alcohol formaldehyde polymer solution. The reactor was purged with vacuum three times and nitrogen for 30 minutes, and then heated to 75°C. Once the temperature was constant and the system was thoroughly stirred, the addition time was controlled at 30 minutes, and 3g of methacrylic acid sulfobetaine was slowly added dropwise to initiate the graft polymerization reaction. The reaction was stopped after 12 hours. After cooling to room temperature, the reactants were poured off, dialyzed using a dialysis bag, and the dialyzed polymer solution was freeze-dried for later use.

[0052] Example 3

[0053] This embodiment is basically the same as Embodiment 1, except that the number and degree of polymerization of the polyionic monomer side chains are controlled by controlling the temperature of the graft polymerization and the amount of monomer used.

[0054] (1) Preparation of polyvinyl alcohol formaldehyde adhesive:

[0055] 10g of polyvinyl alcohol (1799) was added to 100g of deionized water and stirred continuously. The temperature was slowly raised to 90℃ and maintained for 1 hour to completely dissolve the polyvinyl alcohol, resulting in a polyvinyl alcohol aqueous solution. The temperature was adjusted to 85℃, and dilute hydrochloric acid solution (0.1mol / L) was added dropwise to adjust the pH to approximately 2.5. 3.5g of formaldehyde aqueous solution (35wt%) was slowly added dropwise over 30 minutes, and the reaction was maintained at this temperature for 120 minutes. After the reaction was completed, the reaction system was neutralized to a pH of approximately 7 using sodium hydroxide solution (1wt%). The temperature was lowered to 60℃, and 1.5g of urea was added. The reaction was carried out for 30 minutes to remove unreacted formaldehyde. After cooling to room temperature, the reaction mixture was poured out, dialyzed using a dialysis bag, and the polymer solution after dialyzing was freeze-dried for later use.

[0056] (2) Polyvinyl alcohol formaldehyde grafted ionomer:

[0057] 10g of the polyvinyl alcohol acetalized polymer obtained from the above reaction was redissolved in 100g of deionized water. 0.1g of potassium persulfate was added to the reactor containing the polyvinyl alcohol acetal polymer solution. The reactor was purged with vacuum three times and nitrogen for 30 minutes, and then heated to 80°C. Once the temperature was constant and the system was thoroughly stirred, 5g of methacrylic acid sulfobetaine was slowly added dropwise over a period of 30 minutes to initiate the graft polymerization reaction. The reaction was stopped after 12 hours. After cooling to room temperature, the reactants were poured off, dialyzed using a dialysis bag, and the dialyzed polymer solution was freeze-dried for later use.

[0058] Example 4

[0059] This embodiment is basically the same as Embodiment 1, except that carboxybetaine methacrylate was chosen instead of sulfobetaine methacrylate as the grafting monomer.

[0060] (1) Preparation of polyvinyl alcohol formaldehyde adhesive:

[0061] 10g of polyvinyl alcohol (1799) was added to 100g of deionized water and stirred continuously. The temperature was slowly raised to 90℃ and maintained for 1 hour to completely dissolve the polyvinyl alcohol, resulting in a polyvinyl alcohol aqueous solution. The temperature was adjusted to 85℃, and dilute hydrochloric acid solution (0.1mol / L) was added dropwise to adjust the pH to approximately 2.5. 3.5g of formaldehyde aqueous solution (35wt%) was slowly added dropwise over 30 minutes, and the reaction was maintained at this temperature for 120 minutes. After the reaction was completed, the reaction system was neutralized to a pH of approximately 7 using sodium hydroxide solution (1wt%). The temperature was lowered to 60℃, and 1.5g of urea was added. The reaction was carried out for 30 minutes to remove unreacted formaldehyde. After cooling to room temperature, the reaction mixture was poured out, dialyzed using a dialysis bag, and the polymer solution after dialyzing was freeze-dried for later use.

[0062] (2) Polyvinyl alcohol formaldehyde grafted ionomer:

[0063] 10g of the polyvinyl alcohol acetalized polymer obtained from the above reaction was redissolved in 100g of deionized water. 0.1g of potassium persulfate was added to the reactor containing the polyvinyl alcohol acetal polymer solution. The reactor was purged with nitrogen three times under vacuum and then heated to 75°C. Once the temperature was constant and the system was thoroughly stirred, 3g of carboxybetaine methacrylate was slowly added dropwise over a period of 30 minutes to initiate the graft polymerization reaction. The reaction was stopped after 12 hours. After cooling to room temperature, the reactants were poured off, dialyzed using a dialysis bag, and the dialyzed polymer solution was freeze-dried for later use.

[0064] Example 5

[0065] This embodiment is basically the same as Embodiment 1, except that butyraldehyde was chosen as the acetalization reactant, and more non-polar side chains were introduced into the main chain.

[0066] (1) Preparation of polyvinyl butyral adhesive:

[0067] 10g of polyvinyl alcohol (1799) was added to 100g of deionized water and stirred continuously. The temperature was slowly raised to 90℃ and maintained for 1 hour to completely dissolve the polyvinyl alcohol, resulting in a polyvinyl alcohol aqueous solution. The temperature was adjusted to 85℃, and dilute hydrochloric acid solution (0.1mol / L) was added dropwise to adjust the pH to approximately 2.5. 3.5g of butyraldehyde solution (35wt%) was slowly added dropwise over 30 minutes, and the reaction was maintained at this temperature for 120 minutes. After the reaction was completed, the reaction system was neutralized to approximately pH 7 using sodium hydroxide solution (1wt%). The temperature was lowered to 60℃, and 1.5g of urea was added. The reaction was carried out for 30 minutes to remove unreacted butyraldehyde. After cooling to room temperature, the reaction mixture was poured out, dialyzed using a dialysis bag, and the dialyzed polymer solution was freeze-dried for later use.

[0068] (2) Polyvinyl butyral grafted ionomer:

[0069] 10g of the polyvinyl butyral polymer obtained from the above reaction was redissolved in 100g of deionized water. 0.1g of potassium persulfate was added to the reactor containing the polyvinyl butyral polymer solution. The reactor was purged with nitrogen three times under vacuum and then heated to 75°C. Once the temperature was constant and the system was thoroughly stirred, 3g of methacrylic acid sulfobetaine was slowly added dropwise over a period of 30 minutes to initiate the graft polymerization reaction. The reaction was stopped after 12 hours. After cooling to room temperature, the reactants were poured off, dialyzed using a dialysis bag, and the dialyzed polymer solution was freeze-dried for later use.

[0070] Example 6

[0071] This embodiment is basically the same as Embodiment 1, except that polyvinyl alcohol (1788) was chosen to replace polyvinyl alcohol (1799) as the main chain for acetalization and graft polymerization.

[0072] (1) Preparation of polyvinyl alcohol formaldehyde adhesive:

[0073] 10g of polyvinyl alcohol (1788) was added to 100g of deionized water and stirred continuously. The temperature was slowly raised to 90℃ and maintained for 1 hour to completely dissolve the polyvinyl alcohol, obtaining a polyvinyl alcohol aqueous solution. The temperature was adjusted to 85℃, and dilute hydrochloric acid solution (0.1mol / L) was added dropwise to adjust the pH to approximately 2.5. 3.5g of formaldehyde aqueous solution (35wt%) was slowly added dropwise over 30 minutes, and the reaction was maintained at this temperature for 120 minutes. After the reaction was completed, the reaction system was neutralized to approximately pH 7 using sodium hydroxide solution (1wt%). The temperature was lowered to 60℃, and 1.5g of urea was added. The reaction was carried out for 30 minutes to remove unreacted formaldehyde. After cooling to room temperature, the reaction mixture was poured out, dialyzed using a dialysis bag, and the polymer solution after dialyzing was freeze-dried for later use.

[0074] (2) Polyvinyl alcohol formaldehyde grafted ionomer:

[0075] 10g of the polyvinyl alcohol acetalized polymer obtained from the above reaction was redissolved in 100g of deionized water. 0.1g of potassium persulfate was added to the reactor containing the polyvinyl alcohol acetal polymer solution. The reactor was purged with nitrogen three times under vacuum and then purged for 30 minutes. The temperature was then raised to 75°C. After the temperature stabilized and the system was thoroughly stirred, 3g of methacrylic acid sulfobetaine was slowly added dropwise over a period of 30 minutes to initiate the graft polymerization reaction. The reaction was stopped after 12 hours. After cooling to room temperature, the reactants were poured off, dialyzed using a dialysis bag, and the dialyzed polymer solution was freeze-dried for later use.

[0076] Comparative Example 1

[0077] This comparative example uses polyvinyl alcohol (1799) directly as the main binder, dissolved in deionized water for later use, for performance testing and preparation of slurry and electrode sheets.

[0078] Comparative Example 2

[0079] This comparative example is basically similar to the steps in Example 1, except that the ether bond structure is introduced into polyvinyl alcohol (1799) only through on-chain formalization, and the grafting of ionic monomers is omitted.

[0080] Comparative Example 3

[0081] This comparative example is basically similar to the steps in Example 1, except that the polyionic monomer side chain is introduced into polyvinyl alcohol (1799) only through graft polymerization, and the introduction of ether bonds on the main chain is omitted.

[0082] Effect Example

[0083] The performance of the comparative examples and embodiments is described below.

[0084] Preparation of electrode sheets: Nano-silicon, conductive carbon black and binder are homogenized in a ratio of 7:1:2. The slurry is then uniformly coated onto a 0.1 mm copper foil using a 100 μm scraper. The coated copper foil is then transferred to an 80 °C forced-air oven for drying for 12 h to obtain the electrode sheets to be used.

[0085] Peel strength test: 3M tape was used for adhesion, and the electrode strips were cut into 19×5cm shapes. The cut electrode strips were then attached to a glass slide using double-sided tape, and a 180° tensile test was performed on the electrode strips to test the peel strength. The peel speed was 60mm / min.

[0086] Conductivity Testing: The polymer solution was baked into a thin film with a thickness of approximately 0.1 mm using a polytetrafluoroethylene mold, and then cut into circular pieces with a diameter of 18 mm using a cutter. The battery was assembled in the form of positive electrode shell-steel sheet-electrolyte-film-electrolyte-steel sheet-spring sheet-negative electrode shell; the electrolyte used was prepared with ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1, with 10% fluoroethylene carbonate (FEC) as solvent, and 1M lithium hexafluorophosphate (LiPF6) as lithium salt. Battery assembly was carried out in a glove box (H2O≤0.1ppm, O2≤0.5ppm). Before testing, the battery was left at room temperature for 24 hours. Then, the conductivity was tested using an electrochemical workstation.

[0087] Cyclic Testing: Similarly, the batteries used in the cyclic testing were also assembled in a glove box. The assembly sequence was: positive electrode shell - negative electrode plate - electrolyte - separator - electrolyte - lithium plate - steel plate - spring plate - negative electrode shell. The electrolyte used was the same as above. The cyclic testing used the Newway test channel, and the batteries were subjected to constant current charge-discharge testing at 30°C. The charge and discharge current densities were both 0.2C. Before the test, the batteries needed to be allowed to stand for 12 hours.

[0088] The results are as follows Figure 1 and Figure 2 As shown.

[0089] Figure 1 The figure shows the coulombic efficiency of the electrode in Example 4 at a long 0.2C cycle. The initial coulombic efficiency of the battery reached 88.86%, and the coulombic efficiency remained above 98.5% during the subsequent 150 cycles, demonstrating good reversibility. Figure 2 As can be observed from the cycling capacity curves, the initial discharge specific capacity of the nano-silicon electrode in Example 4 is as high as 3409.9 mAh g⁻¹, and after 4 cycles of low-current activation, the initial cycling specific capacity at 0.2C is still 2990.4 mAh g⁻¹. After 146 cycles at a current density of 0.2C, it still maintains a high capacity of 1929.0 mAh g⁻¹, with a capacity retention rate of 64.5%, indicating that the electrode prepared in Example 4 possesses excellent cycling stability as a nano-silicon anode.

[0090] Peel strength and ionic conductivity:

[0091] Test Project Average peel force (N) Ionic conductivity (mS / cm) Example 1 14.30 0.0175 Example 2 14.43 0.0313 Example 3 14.40 0.0205 Example 4 14.35 0.0227 Example 5 12.18 0.0108 Example 6 11.55 0.0156 Comparative Example 1 12.00 0.0014 Comparative Example 2 13.21 0.0133 Comparative Example 3 12.55 0.0092

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. The present invention has been described in detail with reference to the foregoing embodiments. Those skilled in the art should understand that reasonable deletions, modifications, substitutions, and optimizations can be made to the technical solutions of the foregoing embodiments; and these deletions, modifications, substitutions, and optimizations do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a silicon-based negative electrode binder with a self-healing dual-channel ion network, characterized in that, Using polyvinyl alcohol as the main component, ether bonds are introduced into the chain segments through acetalization, and then polyvinyl alcohol acetals are grafted to introduce polyionic monomer side chains; the monomers include one or more of the following: dimethyl diallyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, methacrylamidopropyl trimethyl ammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, itaconic acid, sodium styrene sulfonate, sodium α-olefin sulfonate, 2-methacryloyloxyethyl phosphorylcholine, carboxybetaine acrylamide, methacrylic acid sulfobetaine, and methacrylic acid carboxybetaine. The specific method is as follows: (1) Preparation of polyvinyl acetal adhesive: Polyvinyl alcohol (PVA) was added to deionized water and stirred continuously. The temperature was slowly increased to completely dissolve the PVA, resulting in an aqueous solution. When the temperature reached the first treatment temperature, hydrochloric acid solution was added dropwise to adjust to the first pH value. Then, an aldehyde solution was slowly added dropwise while maintaining the temperature for the reaction. After the reaction was complete, the pH of the reaction system was adjusted to neutral. When the temperature dropped to the second treatment temperature, urea was added to remove unreacted aldehydes. After cooling to room temperature, the reactants were poured off, dialyzed using a dialysis bag, and the resulting polymer solution was freeze-dried for later use. The amount of aldehyde added was 5%–40% of the molar number of hydroxyl groups in the PVA. (2) Polyvinyl acetal grafted ionomer: The polyvinyl acetalized polymer obtained from the above reaction was redissolved in deionized water; then an initiator was added, the air was replaced under vacuum three times and the reactor was purged, and the temperature was raised to the set reaction temperature; after the temperature was constant and the system was stirred evenly, the monomer solution was slowly added dropwise to carry out the graft polymerization reaction; after the reaction was completed, the reaction was stopped; after cooling to room temperature, the reactants were poured out, dialyzed using a dialysis bag, and the polymer solution after dialyzing was freeze-dried for later use.

2. The method for preparing a silicon-based negative electrode binder with a self-healing dual-channel ion network according to claim 1, characterized in that, The degree of polymerization of the polyvinyl alcohol is 600~2500, and the degree of alcoholysis is 50%~99%.

3. The method for preparing a silicon-based negative electrode binder with a self-healing dual-channel ion network according to claim 1, characterized in that, In the acetalization reaction, the degree of conversion of hydroxyl groups to acetalization by aldehydes is 5% to 50%.

4. A method for preparing a silicon-based negative electrode binder with a self-healing dual-channel ion network according to claim 1 or 3, characterized in that, The aldehydes contain an aldehyde group structure, which includes one or more of formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde.

5. The method for preparing a silicon-based negative electrode binder with a self-healing dual-channel ion network according to claim 1, characterized in that, The graft polymerization is carried out by initiating monomers on polyvinyl acetal chains using an initiator, with the mass ratio of grafting host to grafting monomer being 10:1 to 1:10; and the mass ratio of initiator to monomer being 1:1000 to 5:

100. The initiator includes one or more of ammonium persulfate, potassium persulfate, alkali metal persulfate-reducing agent, azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobiscyanopentanoic acid, and azobisisopropylimidazoline; the reducing agent is selected from sodium bisulfite, sodium sulfite, sodium thiosulfate, or oxalic acid.

6. The method for preparing a silicon-based negative electrode binder with a self-healing dual-channel ion network as described in claim 1, characterized in that, In step (1), the first treatment temperature is 50~100 ℃, the first pH value is 1~6, the dropping time is 5~60 min, the reaction time is 1~6 h, the concentration of aldehyde solution is 5%~60%, the second treatment temperature is 30~70 ℃, and the second pH value is 7~10.

7. The method for preparing a silicon-based negative electrode binder with a self-healing dual-channel ion network as described in claim 1, characterized in that, In step (1), the alkaline solution used to adjust the pH includes one or more of LiOH, NaOH, KOH, NaOH, and NH3∙H2O.

8. The method for preparing a silicon-based negative electrode binder with a self-healing dual-channel ion network as described in claim 1, characterized in that, In step (2), the reaction temperature is 50~100 ℃; the dropping time is 5~120 min; and the total reaction time is 1~12 h.

9. The silicon-based anode binder with a self-healing dual-conducting ion network prepared by the preparation method according to any one of claims 1 to 8.

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