Lithium battery silicon-based negative electrode binder as well as preparation method and application thereof

Abstract

The invention provides a lithium battery silicon-based negative electrode binder as well as a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. According to the invention, polyacrylic acid is taken as a matrix, zinc ions and nickel ions are introduced to form a dynamic coordination bond network, and 3, 4-ethylenedioxythiophene (i.e., EDOT) monomers are subjected to in-situ polymerization to generate a poly (3, 4-ethylenedioxythiophene) (i.e., PEDOT) conductive polymer, so that the water-based composite binder with dynamic self-repairing capability and a conductive ion-conductive electron bicontinuous network structure is constructed; the technical problems that a traditional binder is insufficient in binding force in a silicon negative electrode, poor in flexibility, free of conductivity and difficult to adapt to large-volume change of a silicon material are solved. The negative electrode binder can be used in the fields of high-energy-density lithium ion batteries, fast-charging batteries, flexible or miniature electronic equipment and the like, and has great development potential in the fields of high-end power batteries, energy storage systems and the like.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a silicon-based negative electrode binder for lithium batteries, its preparation method, and its application. Background Technology

[0002] With the increasing demand for high-energy-density lithium-ion batteries, silicon-based anodes have become a research focus due to their extremely high theoretical specific capacity. However, the significant volume expansion of silicon during charging and discharging can easily lead to electrode pulverization, interfacial instability, and rapid capacity decay. Therefore, it is crucial to develop high-performance binders that can adapt to volume changes, maintain structural integrity, and ensure interfacial stability. Currently, traditional binders such as polyacrylic acid still have shortcomings in terms of mechanical flexibility, intrinsic conductivity, and long-term cycle stability. Furthermore, there are few solutions that can simultaneously integrate dynamic self-healing and efficient ion / electron transport functions, which restricts the overall improvement of silicon anode performance.

[0003] To address these challenges, existing technologies have explored different approaches. CN121355258A discloses a binder for sulfide all-solid-state batteries, employing polyacrylic acid copolymer grafted metal nanowires to enhance electronic conductivity. However, its reliance on physically blended metal nanowires makes it difficult to form a uniform, dynamic stress dissipation network, and it does not involve the construction of ion transport channels, resulting in limited interfacial compatibility in liquid electrolyte systems. CN121271488A introduces dynamic disulfide bonds into a plastic track adhesive to achieve significant self-healing properties. However, the exchange reaction of these dynamic covalent bonds typically requires high temperatures or specific catalysts to trigger, making efficient operation difficult under battery operating conditions. Furthermore, it lacks conductivity design, thus, although its self-healing performance is excellent, it cannot be used as a superior battery binder. CN116285777B discloses a self-healing adhesive based on metal ion-polymer coordination bonds, achieving dynamic repair through coordination between polynitrogen heterocycles and metal ions. However, its synthetic route is complex, involving multiple high-temperature organic reactions, and it does not introduce intrinsically conductive components. Rate performance improvement depends on external conductive agents, limiting its process scale-up and further optimization of electrochemical performance. Therefore, existing research still has significant shortcomings in achieving efficient dynamic self-healing under mild conditions, simultaneously constructing intrinsic ion / electron dual channels, and simplifying the preparation process.

[0004] In summary, there is an urgent need to develop a multifunctional binder that is easy to synthesize, can gently trigger dynamic self-healing during electrochemical cycling, and has both high efficiency in ion and electron transport capabilities, in order to comprehensively solve the problems of volume effect, interface instability and high polarization of silicon anodes, and promote the development of high energy density, fast-charging lithium-ion batteries. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a silicon-based anode binder for lithium-ion batteries, its preparation method, and its applications. This invention uses polyacrylic acid as a matrix, introduces zinc and nickel ions to form a dynamic coordination network, and in-situ polymerizes 3,4-ethylenedioxythiophene (EDOT) monomers to generate poly(3,4-ethylenedioxythiophene) (PEDOT) conductive polymer. This constructs an aqueous composite binder with both dynamic self-healing capabilities and a continuous ion-conducting electron-conducting network structure. This binder can be used in high-energy-density lithium-ion batteries, fast-charging batteries, flexible or microelectronic devices, etc., solving the technical problems of insufficient adhesion, poor flexibility and interfacial stability, lack of conductivity, and inability to adapt to large volume changes in silicon materials in traditional binders for silicon anodes.

[0006] This invention discloses a silicon-based negative electrode binder for lithium batteries, which uses polyacrylic acid as the matrix binder polymer, introduces zinc ions and nickel ions to form a dynamic and reversible coordination bond crosslinking network with the carboxyl groups on the polyacrylic acid chain, and simultaneously polymerizes EDOT monomer in situ in the system to generate conductive polymer PEDOT, thereby obtaining a composite binder with a dual continuous network structure.

[0007] This invention also discloses a method for preparing a silicon-based negative electrode binder for lithium batteries, such as... Figure 1 As shown, the feature is: Step 1: Dissolve polyacrylic acid in deionized water to form a homogeneous solution, add zinc sulfate and nickel sulfate aqueous solution and mix, then adjust the pH of the mixed solution to weakly acidic.

[0008] Step 2: Under continuous stirring and an inert gas atmosphere, EDOT monomer is added to a weakly acidic mixed solution and stirred. The reaction system is cooled in a low-temperature medium. Under continuous and gentle stirring, oxidant is added dropwise at a constant rate to initiate the oxidative polymerization reaction of the monomer.

[0009] Step 3: The system after polymerization reaction is completed is transferred to a dialysis bag for dialysis. The obtained pure colloidal dispersion is then deep-frozen to completely solidify and freeze-dried to obtain a loose and porous solid block. After grinding, the binder powder is obtained.

[0010] This invention also discloses the application of a silicon-based negative electrode binder for lithium batteries. The negative electrode active material, conductive carbon black, and binder are mixed in proportion and deionized water is added and repeatedly ground to form a slurry. The slurry is then coated on copper foil as a negative electrode sheet and transferred to a vacuum drying oven for a first stage of low-temperature vacuum drying and a second stage of high-temperature vacuum drying. The dried electrode sheet is then placed in a sealed container and transferred to a glove box filled with nitrogen. In the glove box, a CR2032 coin cell is assembled using a lithium sheet as the positive electrode and a 1:1 mixture of ethylene carbonate and dimethyl carbonate (containing 1 mol / L LiFSI) as the electrolyte.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By introducing Zn 2+ and Ni 2+ The metal-carboxyl coordination bonds form a dynamic coordination cross-linking network with the carboxyl groups on the polyacrylic acid chain, giving the binder the ability to self-repair during electrochemical cycling. When the silicon particles expand or contract, these metal-carboxyl coordination bonds can be reversibly broken and recombined, thereby absorbing stress and repairing microstructural damage caused by volume changes, and maintaining the structural integrity of the electrode.

[0012] 2. Through in-situ polymerization of PEDOT, a three-dimensional continuous electronic conduction framework is formed in the polyacrylic acid matrix. Simultaneously, the carboxyl groups of the polyacrylic acid itself and the introduced Zn... 2+ Ni 2+ It provides abundant ion transport sites and channels. This bicontinuous network of interwoven and complementary ion and electron conduction paths enables lithium ions and electrons to be transported efficiently and synergistically throughout the electrode, greatly reducing the polarization impedance of the electrode.

[0013] 3. Controlling the pH of the system within a weakly acidic range during binder preparation helps to gently control the EDOT polymerization rate, promotes the formation of a uniform and ordered structure in the product, and avoids excessive oxidation, side reactions, or corrosion of equipment that may occur under strong acid conditions. It also helps to form a stable and uniform solid electrolyte interface (SEI) film on the electrode surface, effectively preventing the continuous decomposition of the electrolyte and the irreversible consumption of active lithium. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the preparation process of the silicon-based negative electrode binder of the present invention. Figure 2 This is a schematic diagram illustrating the cyclic capacity retention of embodiments and comparative examples of the present invention; Figure 3 This is a schematic diagram of the discharge capacity of the embodiments and comparative examples of the present invention at different rates; Figure 4 The infrared spectrum of the binder powder prepared in Example 1 of this invention is shown below. Figure 5 This is a Raman spectrum scan of the binder powder prepared in Example 1 of the present invention. Detailed Implementation

[0015] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0016] This invention proposes a method for preparing a silicon-based negative electrode binder for lithium batteries, such as... Figure 1 As shown, the specific technical solution is as follows: 1. Prepare the matrix and construct an ion-dynamic cross-linked network Polyacrylic acid was dissolved in the aqueous phase, and Zn was introduced. 2+ and Ni 2+ The system pH was adjusted to weakly acidic to form a dynamic coordination network. This dynamic coordination network is based on Zn. 2+ and Ni 2+ As a crosslinking point, it reversibly coordinates with the carboxyl groups on the polyacrylic acid chain to form a self-healing polymer network. During the charging and discharging process of the silicon-based negative electrode, the mechanical stress generated by the repeated expansion and contraction of the electrode material can cause local coordination bonds to break to buffer the stress. After the stress is eliminated, the coordination bonds can reform in new positions, achieving self-repair of the microstructure and thus maintaining the integrity of the electrode. 2+ and Ni 2+ As transition metal ions possess empty orbitals, they can accept electron pairs as Lewis acids. The oxygen atoms on the carboxyl groups of polyacrylic acid are rich in lone pairs of electrons, allowing them to donate electron pairs as Lewis bases. When these two meet in aqueous solution, the lone pairs of electrons from the oxygen atoms fill the empty orbitals of the metal ion, forming coordinate bonds. A single metal ion can coordinate with multiple carboxyl groups simultaneously, thus crosslinking the linear polymer into a three-dimensional network. Zinc and nickel ions differ in their coordination ability and geometry; their combined use can form crosslinking points with complementary strength and kinetics, enriching the network relaxation modes. This coordinate bond strength is higher than physical interactions such as hydrogen bonds, but lower than covalent bonds, making it an environmentally sensitive dynamic bond. Its stability is directly affected by the type and concentration of metal ions and the chemical environment, including pH. Adjusting the system to a weakly acidic environment is necessary because under strongly acidic conditions, the carboxyl groups are highly ionized, resulting in lower electron cloud density and making coordination difficult; while under strongly alkaline conditions, the carboxyl groups are completely ionized into -COO. -It is easy to form overly dense and irreversible precipitates or gels with metal ions. However, a weakly acidic environment can ionize some carboxyl groups, providing sufficient coordination sites. At the same time, the unionized -COOH can help stabilize the structure through hydrogen bonding, prevent the hydrolysis and precipitation of metal ions, and ensure the smooth progress of subsequent EDOT monomer oxidative polymerization, avoiding side reactions caused by excessive acidity or alkalinity or excessively rapid decomposition of oxidants.

[0017] 2. Introducing monomers and constructing a conductive network in situ through low-temperature oxidative polymerization. Under an inert atmosphere, EDOT monomers were added to the above system. After thorough emulsification and dispersion, an oxidant was added at low temperature to generate a conductive polymer in situ. The π-conjugated system of the thiophene ring in the EDOT molecule and its ethylene dioxy substituents at the 3 and 4 positions determine its low oxidative polymerization potential and its ability to form highly conjugated polymer chains. Under stirring, the hydrophobic EDOT monomers were dispersed in the aqueous phase as microdroplets. PAA molecules were adsorbed at the droplet interface, playing a stabilizing role in emulsification. The introduction of an inert gas ensured the complete removal of oxygen, as oxygen, as an interfering oxidant, could cause randomization of the polymerization initiation point and may induce side reactions, affecting the regularity and doping efficiency of the final PEDOT. The addition of the oxidant ammonium persulfate initiated a free radical polymerization chain reaction, and the EDOT monomers formed linear PEDOT chains through α-carbon-carbon coupling. The polymerization process is carried out at low temperatures. This low-temperature environment suppresses the decomposition rate of ammonium persulfate and the exothermic effect of the reaction, preventing excessive oxidation, cross-linking, or aggregation of PEDOT chains due to localized overheating. This ensures a relatively uniform molecular weight distribution in the polymer and facilitates the formation of PEDOT with a long-range conjugated structure, which is fundamental to achieving high intrinsic electrical conductivity. The PEDOT chains generated by polymerization carry a positive charge due to oxidation doping, resulting in electrostatic attraction with the partially negatively charged PAA chains. Simultaneously, the rigid conjugated chains of PEDOT and the flexible aliphatic chains of PAA are tightly bound together through physical entanglement and π-polar interactions. This force promotes the natural interpenetration and deposition of PEDOT within the PAA-metal ion network during polymerization, forming an interpenetrating rather than phase-separated composite structure. The spatial confinement of the PAA network prevents excessive stacking and crystallization of the PEDOT chains, allowing them to be uniformly dispersed as amorphous nanofibers or nanoparticles. This constructs a three-dimensional electronic conduction network that runs throughout the entire material. This electronic network interweaves and complements the pre-constructed ion conduction network, forming a unique bicontinuous structure. The ion conduction network consists of ionizable carboxyl groups on the PAA chain and zinc and nickel ions cross-linked through dynamic coordination bonds. These components provide sites and pathways for lithium ion migration. The continuous interpenetration of the electron and ion networks at the nanoscale enables lithium ions and electrons to achieve coordinated and efficient synchronous transport within the electrode, greatly reducing charge transfer impedance. This structural design allows the binder itself to possess both electronic and ionic conductivity, reducing absolute dependence on traditional conductive additives. When the electrode is subjected to silicon volume changes, the conductive pathway is not easily interrupted due to contact failure between active materials, thus ensuring electrochemical kinetic stability under high rate and fast charging performance.

[0018] 3. Purification and solidification of reaction products The polymerized composite colloidal solution is dialyzed to remove small molecule impurities, and then the purified solution is freeze-dried into a solid powder. The membrane pore size of the dialysis bag allows small molecules such as water molecules, inorganic salt ions, unreacted trace amounts of EDOT monomers and their oligomers to pass freely, while the large molecular weight PAA-PEDOT complex is trapped inside the bag. The dialysis process is carried out in flowing deionized water, and a concentration difference is maintained across the membrane, driving impurity molecules to diffuse outward continuously. Since the presence of impurities has a serious negative impact on the performance of the final binder, residual ions can increase the conductivity background of the final electrode sheet, interfere with the assessment of the intrinsic conductivity of the binder, and may also migrate or undergo side reactions in the battery electrolyte, damaging the stability of the electrode / electrolyte interface. Residual monomers or oligomers may polymerize or decompose during battery cycling, leading to increased interfacial impedance or gas generation. Therefore, dialysis purification ensures the purity and consistency of the binder's chemical composition. The dialysis process is also accompanied by a slow change in the solution environment, with residual acids or bases being continuously diluted until the system eventually approaches neutrality. This mild environmental change helps to further stabilize the composite colloidal structure. The subsequent freeze-drying is a dehydration process that converts the purified liquid product into a solid powder. The dialyzed solution is rapidly and deeply frozen to a temperature far below its eutectic point. At this ultra-low temperature, the water in the solution rapidly crystallizes to form tiny ice crystals. The PAA-PEDOT complex is squeezed into the gaps between the ice crystals and solidifies, forming a solid mixture composed of an ice crystal template and a solute framework. The size and morphology of the ice crystals are determined by the freezing rate. Rapid freezing is beneficial for forming small and uniform ice crystals. Subsequently, a high-vacuum environment was established in a freeze dryer, and the sample was kept at a low temperature. This allowed the ice crystals to sublimate directly into water vapor without passing through a liquid state, which was then removed by a vacuum pump. The remaining pores formed a porous solute framework. This drying method avoids the capillary forces caused by the surface tension of water in conventional heating drying. Under the action of capillary forces, the pores in the wet gel collapse when the liquid evaporates, leading to material shrinkage, densification, a significant decrease in specific surface area, and the formation of a dense and hard mass that is difficult to grind and has poor resolubility. Freeze drying completely avoids the presence of a liquid phase, thus perfectly preserving the porous network structure formed in the early stage of freezing, determined by the ice crystal template. This structure allows it to quickly contact and disperse with water in the subsequent electrode slurry preparation, exhibiting excellent resolubility. The porous structure also means that the binder powder has a lower packing density and a larger volume for the same mass, facilitating more uniform physical mixing with other electrode materials during the dry powder mixing stage. The low-temperature process of freeze drying also avoids the destruction of the heat-sensitive PAA chain structure, dynamic coordination bonds, and PEDOT doping state.

[0019] The following are some specific embodiments of the present invention, and Table 1 shows the raw material information used in the embodiments.

[0020] Table 1 Raw Material Information Table Example 1 S1: Add 10.0g of polyacrylic acid powder to 200mL of deionized water and mechanically stir at 500rpm for 6h at room temperature until the powder is completely dissolved to form a homogeneous and transparent viscous solution. While maintaining continuous stirring, slowly add 20mL of 1mol / L ZnSO4·7H2O and 20mL of 1mol / L NiSO4·6H2O to the solution in sequence. Then continue stirring for 3h to disperse the metal ions evenly. Adjust the pH of the system to 6.0 using 2.0wt% NaOH solution, and then stir for another 1h to make the system homogeneous. S2: Under the protection of continuous high-purity nitrogen gas at a flow rate of 50 mL / min, 2.0 g of EDOT monomer was added to the solution obtained in S1. Then the nitrogen flow rate was adjusted to 10 mL / min, and the mixture was mechanically stirred at 300 rpm for 6 h. The system was then transferred to an ice bath at 2 °C, and 30 mL of 0.5 mol / L ammonium persulfate solution was added to the system using a constant pressure dropping funnel, with the dropping rate controlled at 0.5 mL / min. After the addition was completed, the mixture was stirred at low temperature for 18 h to obtain a blue-black reaction solution. S3: Transfer the reaction solution to a dialysis bag with a cutoff of 12000 Da and tie the bag tightly. Completely immerse the dialysis bag in 5L of flowing deionized water and dialyze it at room temperature for 72 hours, changing the dialysis water every 12 hours. After dialysis, place the colloidal solution in the bag in an ultra-low temperature freezer and freeze it at -50°C for 8 hours to solidify it. Then, quickly transfer the solidified sample to a pre-cooled refrigerated dryer at -85°C and freeze-dry it continuously for 36 hours under the conditions of cold trap temperature -80°C and system vacuum degree of 5Pa to obtain a dark blue blocky solid. Then, grind the solid into powder in an agate mortar and pass it through a 200-mesh sieve to obtain the silicon-based negative electrode binder.

[0021] S4: Mix silicon powder, binder, and conductive carbon black in a mass ratio of 6:2:2, and add 30% deionized water by mass of the mixture. Grind repeatedly until a uniform, fine, and fluid slurry is formed. Use a doctor blade coater to evenly coat the slurry onto the copper foil, with a coating amount of 4 mg / cm². 2 The copper foil was then immediately transferred to a vacuum drying oven and dried at 60℃ and -0.1MPa for 2 hours, followed by drying at 120℃ under the same vacuum for 8 hours. The copper foil was then transferred from the vacuum drying oven to a nitrogen-filled sealed container and then to a nitrogen-filled glove box. In the glove box, the dried electrode was rolled and punched into 12mm diameter round sheets with a compacted density of 1.5g / cm³. 3A CR2032 coin cell was assembled using lithium foil as the positive electrode, Super P as the conductive carbon black, cellulose membrane as the separator, and a 1:1 mixture of ethylene carbonate and dimethyl carbonate in 1 mol / L LiFSI as the electrolyte.

[0022] Example 2 The preparation method according to Example 1 differs in that: S1: 8g of polyacrylic acid was weighed out, and the initial stirring time was 4 hours. Zn 2+ and Ni 2+ The concentration was 0.8 mol / L, the added volume was 15 mL, the second stirring time was 2 h, and the pH of the system was adjusted to 5.5. S2: The mechanical stirring time at room temperature is 4h, the ice bath temperature is 0℃, the ammonium persulfate solution is replaced with potassium persulfate solution with a concentration of 0.4mol / L, the dropping time is 50min, and the low temperature stirring time is 12h; S3: Dialysis time is 60h, water change frequency is once every 10h, low temperature of the freezer is -55℃, freezing time is 4h, cold trap temperature is -78℃, system vacuum degree is 3Pa, and freeze drying time is 30h. S4: The first stage drying temperature is 50℃ and the drying time is 1.5h. The second stage drying temperature is 100℃ and the drying time is 6h. The remaining steps are the same.

[0023] Example 3 The preparation method according to Example 1 differs in that: S1: 12g of polyacrylic acid was weighed out, and the initial stirring time was 8 hours. Zn 2+ and Ni 2+ The concentration was 1.2 mol / L, the added volume was 25 mL, the second stirring time was 4 h, and the pH of the system was adjusted to 6.5. S2: The mechanical stirring time at room temperature is 8 hours, the ice bath temperature is 5℃, the concentration of ammonium persulfate solution is 0.6 mol / L, the dropping time is 70 minutes, and the low-temperature stirring time is 24 hours; S3: Dialysis time is 84h, water change frequency is once every 14h, low temperature of the freezer is -45℃, freezing time is 8h, cold trap temperature is -82℃, system vacuum degree is 10Pa, freeze drying time is 42h; S4: The first stage drying temperature is 70℃ and the drying time is 3h. The second stage drying temperature is 140℃ and the drying time is 12h. The remaining steps are the same.

[0024] Example 4 The preparation method according to Example 1 differs in that: S1: 9g of polyacrylic acid was weighed out, and the initial stirring time was 5 hours. Zn 2+ and Ni 2+ The concentration was 0.9 mol / L, the added volume was 22 mL, the second stirring time was 2.5 h, and the pH of the system was adjusted to 5.8. S2: The mechanical stirring time at room temperature is 7h, the ice bath temperature is 3℃, the concentration of ammonium persulfate solution is 0.55mol / L, the dropping time is 65min, and the low-temperature stirring time is 20h; S3: Dialysis time is 77h, water change frequency is once every 11h, low temperature of the freezer is -48℃, freezing time is 7h, cold trap temperature is -81℃, system vacuum degree is 8Pa, and freeze drying time is 40h. S4: The first stage drying temperature is 65℃ and the drying time is 2.5h. The second stage drying temperature is 130℃ and the drying time is 10h. The remaining steps are the same.

[0025] Comparative Example 1 The preparation method according to Example 1 differs in that: S1: Instead of adding zinc sulfate and nickel sulfate solutions, add an equal amount of ethylenediamine, adjust the pH to 6.0, heat the system to 60°C, and stir continuously for 6 hours. All other steps are the same.

[0026] This comparative example prepares a statically covalently cross-linked composite binder using ethylenediamine as a covalent cross-linking agent and the corresponding lithium battery.

[0027] Comparative Example 2 The preparation method according to Example 1 differs in that: S2: Without adding EDOT monomer and ammonium persulfate, the system obtained in S1 is directly purified and cold-dried for curing. All other steps are the same.

[0028] This comparative study prepared an adhesive with dynamic repair capabilities but lacking intrinsic electronic conductivity, and a corresponding lithium battery.

[0029] Comparative Example 3 The preparation method according to Example 1 differs in that: S1: Adjust the pH of the system to 6.0 using dilute sulfuric acid; the remaining steps are the same.

[0030] This comparative example shows the preparation of a composite binder synthesized under a strong acid environment and the corresponding lithium battery.

[0031] Comparative Example 4 The preparation method according to Example 1 differs in that: CR2032 coin cells were fabricated by directly using commercial PVDF powder as a binder.

[0032] This comparative example demonstrates the preparation of a conventional PVDF binder and its assembly into a commercial lithium battery.

[0033] Experimental Example 1 According to the assembly of lithium batteries in the examples, the CR2032 lithium-ion batteries prepared in Examples 1-4 and Comparative Examples 1-4 were placed in a 25°C constant temperature chamber and left to stand for 12 hours to allow the internal temperature of the batteries to equalize. Subsequently, using the Blue Battery Testing System, the batteries were activated by cycling with a 0.1C current for 5 cycles within a voltage range of 3.0-4.3V. After that, the batteries were left to stand for 12 hours. After the standing period, the batteries were subjected to 1000 continuous charge-discharge cycles with a 1C current. The discharge capacity at the 5th charge-discharge cycle was used as the baseline discharge capacity C0, and the capacity retention rate of the batteries at the 1C current was calculated. The results are shown in Table 2.

[0034] Table 2 Cyclic performance of the examples and comparative samples From Table 2 and Figure 2 As can be seen from the examples, the lithium batteries assembled with the binders prepared in the examples all exhibited excellent and stable capacity retention rates, maintaining high discharge capacity after 1000 cycles. This indicates that the dynamic coordination self-healing network and the ion-conductivity-electron-conductivity dual-continuous network in the binder significantly improve the stability of the batteries. Comparative Example 1 sample had a high initial capacity, but its capacity retention rate dropped sharply after 1000 cycles. This is because the covalent cross-linked network formed by ethylenediamine and polyacrylic acid lacks reversibility. Under the repeated mechanical stress generated by the cyclic expansion and contraction of the silicon anode, the rigid covalent network cannot dissipate energy through bond breaking and recombination, leading to the irreversible generation and propagation of microcracks, rapid destruction of the electrode structure, and shedding of active material, thus causing rapid capacity decay. Comparative Example 2 sample lacks intrinsic electronic conductivity, therefore its initial capacity and capacity retention rate are both low. This is due to the lack of in-situ polymerized P... In the EDOT conductive network, electron conduction at the electrodes relies entirely on physically added conductive agents, resulting in low electron transport efficiency, large initial polarization, and insufficient capacity utilization. Furthermore, during cycling, volume changes in silicon particles easily lead to contact failure between the conductive agent network and the active particles, and unlike the PEDOT network, it cannot maintain the conductive path through deformation, causing a continuous increase in impedance and capacity decay during cycling. Comparative Example 3 exhibited the worst performance because the binder, synthesized in a strongly acidic environment, had an extremely high degree of carboxylation of the polyacrylic acid matrix, severely inhibiting its interaction with Zn. 2+ / Ni 2+Effective coordination is impossible, and the dynamic self-healing network cannot be constructed normally. At the same time, the acidic environment severely interferes with the polymerization process of EDOT, resulting in an increase in PEDOT structural defects, poor conductivity, and deterioration of compatibility with the matrix. Strong acid residues can also damage the stability of the electrode / electrolyte interface, causing all functions of the binder to fail. In the comparative example 4 sample, PVDF, as a traditional binder, relies on weak van der Waals forces. Its mechanical strength and elasticity are insufficient to constrain the volume expansion of silicon particles exceeding 300%. During cycling, the electrode active layer cracks, pulverizes, and peels off from the current collector due to repeated stress, resulting in loss of electrical contact and continuous consumption of active lithium. Therefore, the capacity will be significantly lost during long-term cycling.

[0035] Experiment Example 2 The CR2032 lithium-ion batteries prepared in Examples 1-4 and Comparative Examples 1-4 were placed in a 25°C constant temperature chamber and left to stand for 12 hours to allow the internal temperature of the batteries to equalize. Then, using the Blue Battery Testing System, five cycles were performed at a rate of 0.1C within a voltage range of 3.0-4.3V. The discharge capacity of the fifth cycle was taken as the baseline capacity C0. Subsequently, five cycles were performed at rates of 0.2C, 0.5C, 1C, 2C, 5C, and 8C, and the stable discharge capacity C of the last cycle at each rate was recorded. x (x is the current rate), calculate the battery's capacity retention rate at each rate. After completing the 8C rate test, adjust the current back to 0.1C and perform 5 more cycles. Record the discharge capacity C' at this point and calculate its capacity recovery rate. The formulas for calculating the capacity recovery rate and capacity retention rate are as follows: ; The results are shown in Table 3.

[0036] Table 3 Rate performance of the examples and comparative samples From Table 3 and Figure 3As can be seen from the examples, the batteries assembled with the binders prepared in the examples all have excellent high-rate discharge capability and structural reversibility. They can still maintain a high capacity retention rate at extremely high charge and discharge rates, and the capacity loss is minimal when returning to low rates. This indicates that the ion-conducting-electron-conducting dual continuous network can significantly reduce electrode polarization, ensuring the coordinated and rapid transport of lithium ions and electrons at extremely high current densities. At the same time, the dynamic self-healing network structure ensures that the electrode structure can recover in time after rapid and drastic volume changes, thereby achieving high rate and high capacity recovery. The rigid covalent cross-linked network in Comparative Example 1 cannot adapt to the dynamic process at high rates. During rapid charge and discharge, the silicon particles experience more drastic instantaneous volume changes. The static network, unable to buffer stress through reversible bond breakage, leads to the rapid generation and propagation of internal electrode cracks. The transport pathways for ions and electrons are physically blocked, causing a sharp drop in capacity. This structural damage is irreversible, resulting in extremely poor capacity recovery. Comparative Example 2, lacking an electrode with an intrinsic PEDOT conductive network, relies entirely on the physically contacting conductive agent network for electron transport. At high rates, it is prone to localized circuit breaks due to minute displacements or volume changes in the silicon particles, generating significant electrochemical polarization and greatly reducing usable capacity. The instability of the electron pathways also affects the reversible recovery of the structure. Comparative Example 3… The strongly acidic environment during sample preparation fundamentally destroyed the functional basis of the binder. Due to the difficulty in forming a dynamic coordination network, the polymerization quality of PEDOT was low. As a result, the binder prepared in this way had neither effective self-healing ability nor efficient conductive network. In high-rate testing, the electrode structure rapidly disintegrated, making it almost impossible to carry out effective charge transfer and storage, exhibiting the characteristic of rapid capacity decay, and the damage was completely irreversible. The PVDF binder of Comparative Example 4 sample had huge ohmic polarization at high rates due to its insulation properties, and its lack of flexibility made it unable to bind the drastic volume changes of silicon particles at high rates. This caused the active material to rapidly pulverize and detach from the current collector, and the electronic conduction network was completely destroyed. Therefore, the battery not only experienced a significant capacity reduction at high rates, but its structure also suffered permanent damage with weak recovery ability.

[0037] Experimental Example 3 Take 2 mg of the binder powder prepared in Example 1, mix it with dry spectral grade KBr powder at a mass ratio of 1:100 in an agate mortar, grind it, and then press it into a translucent sheet. Then, heat it at a pressure of 400-4000 cm⁻¹. -1 Infrared spectral scanning was performed within the specified wavelength range, and the scanning results are as follows: Figure 4 As shown.

[0038] The binder powder prepared in Example 1 was placed in a microconfocal Raman spectrometer and Raman spectroscopy was performed at a wavelength of 532 nm. The laser power was 0.5 mW to 1 mW, and the scanning range was 1000 to 2000 cm⁻¹. -1 The scan results are as follows Figure 5As shown.

[0039] from Figure 4 As can be seen from this, the adhesive is at 870cm -1 The vibration of the CS bond in the thiophene ring at 1100 cm⁻¹ indicates the presence of a sulfur heterocycle in the binder; -1 The appearance of the COC stretching vibration peak at 1440 cm⁻¹ indicates that the EDOT monomer has been successfully polymerized into PEDOT, and its cyclic structure has remained intact during the oxidative polymerization process; the peak at 1440 cm⁻¹ further confirms this. -1 and 1600cm -1 The peak appearing at this point is the carboxylate ion -COOH. - The bimodal split of the peak, with the introduction of zinc and nickel ions and pH adjustment, caused the peak of the originally free carboxyl group to shift slightly to the right and split into two characteristic peaks at the low beam, namely a symmetric stretching vibration peak and an asymmetric stretching vibration peak. This indicates that a bridging coordination mode was formed between the metal ions and polyacrylic acid, successfully constructing a three-dimensional network structure. Meanwhile, at 1600 cm⁻¹... -1 The peak at 1760 cm⁻¹ also represents C=C in PEDOT, indicating that the conductive network is generated in situ on the polypropylene chain and interwoven in the matrix; -1 The presence of a stretching vibration peak of C=O in the free carboxyl group at 3300 cm⁻¹ indicates that some protonated carboxyl groups are retained in the system; -1 The broad peak at that point is the OH stretching vibration peak caused by the polypropylene chain absorbing water at room temperature.

[0040] from Figure 5 It can be seen from this that at 1425cm -1 C appears on the thiophene ring of PEDOT. α =C β The symmetric stretching vibration peak, which shifts towards lower wavelengths compared to the peak of neutral PEDOT, indicates that PEDOT mainly exists in a planar molecular configuration and a quinone structure with better electron delocalization. This demonstrates the inductive effect of polyacrylic acid as a template on PEDOT, which restricts the coiling of PEDOT, making its molecular chain more extended, thereby constructing an efficient electron transport channel.

Claims

1. A lithium battery silicon-based anode binder, comprising a matrix and additives, characterized in that: The matrix is ​​polyacrylic acid, and the additives are metal ions and conductive polymers; the metal ions are Zn derived from zinc sulfate. 2+ and Ni derived from nickel sulfate 2+ The conductive polymer is poly(3,4-ethylenedioxythiophene); the binder comprises a dynamically reversible self-healing network structure and a bicontinuous network structure with both ion and electronic conductivity capabilities; the dynamically reversible self-healing network and the ion conductivity are formed by using polyacrylic acid as a matrix and forming dynamic ion coordination bonds with metal ions; the electronic conductivity is formed by dispersing the conductive polymer in the polyacrylic acid matrix through in-situ polymerization.

2. The lithium battery silicon-based negative electrode binder according to claim 1, characterized in that: The Zn 2+ and the Ni 2+ The total number of moles of polyacrylic acid is in the molar ratio of carboxyl groups on the polyacrylic acid chain to (1:2) to (1:5), and the mass ratio of polyacrylic acid to poly(3,4-ethylenedioxythiophene) is (4:1) to (6:1).

3. A method for preparing a lithium battery silicon-based negative electrode binder according to any one of claims 1 to 2, characterized in that, It is prepared according to the following method: S1: Dissolve polyacrylic acid in deionized water, stir to form a homogeneous solution, add zinc sulfate and nickel sulfate aqueous solution and stir again, adjust the pH of the mixed solution to acidic; S2: Under continuous stirring and an inert gas atmosphere, 3,4-ethylenedioxythiophene monomer was added to an acidic mixed solution and stirred to disperse. Then the reaction system was placed at a low temperature, and an oxidant was added dropwise at a constant rate under continuous stirring to initiate the oxidative polymerization reaction of the monomer. S3: The system after the polymerization reaction is completed is transferred to a dialysis bag for dialysis. The obtained pure colloidal dispersion is then deep-frozen to completely solidify and freeze-dried to obtain a loose and porous solid block. After grinding, the binder powder is obtained.

4. The method for preparing a lithium battery silicon-based negative electrode binder according to claim 3, characterized in that: The concentration of polyacrylic acid in the homogeneous solution described in S1 is 4-6 wt%; the stirring time is 4-8 h; the concentration of the zinc sulfate and nickel sulfate aqueous solution is 0.8-1.2 mol / L, and the addition amount is 15-25 mL; the stirring time again is 2-4 h; and the pH of the mixed solution is adjusted to 5.5-6.

5.

5. The method for preparing a silicon-based negative electrode binder for lithium batteries according to claim 3, characterized in that: The oxidant mentioned in S2 is one or more of ammonium persulfate and potassium persulfate.

6. The method for preparing a lithium battery silicon-based negative electrode binder according to claim 3, characterized in that: The stirring and dispersion time in S2 is 4~8h; the low temperature is 0~5℃; the oxidant concentration is 0.4~0.6mol / L; the constant rate dropping time is 50~70min; and the oxidative polymerization reaction time is 12~24h.

7. The method for preparing a silicon-based negative electrode binder for lithium batteries according to claim 3, characterized in that: The dialysis time described in S3 is 60~84h, with water changed every 10~14h; the deep freezing temperature is -55~-45℃, and the deep freezing time is 4~8h; the cold trap temperature during freeze drying is -78~-82℃, the system vacuum degree is 3~10Pa, and the freeze drying time is 30~42h.

8. The application of the lithium battery silicon-based negative electrode binder according to any one of claims 1 to 2, characterized in that: The binder can be used to prepare a silicon-based negative electrode sheet for lithium batteries. The negative electrode sheet is prepared by mixing silicon powder, the silicon-based negative electrode binder, and conductive carbon black in a mass ratio of 6:2:2, then adding deionized water as a solvent to prepare a slurry, and coating the slurry onto copper foil, followed by two stages of vacuum drying.

9. The application of the lithium battery silicon-based negative electrode binder according to claim 8, characterized in that: The amount of deionized water added is 30% of the mass of the mixed powder; in the two-stage vacuum drying, the temperature of the first stage is 50~70℃ and the drying time is 1.5~3h, and the drying temperature of the second stage is 100~140℃ and the drying time is 6~12h.

10. The application of the lithium battery silicon-based negative electrode binder according to claim 8, characterized in that: The negative electrode can be assembled into a lithium battery; the positive electrode of the lithium battery is a lithium metal sheet, and the negative electrode is a silicon-based negative electrode of the lithium battery as described in any one of claims 8 to 9; the capacity retention rate of the lithium battery after 1000 cycles of 1C charge and discharge is >65%, and the capacity retention rate at 8C charge and discharge rate is >60%.

Images