Multifunctional conductive binder, negative pole piece, preparation method of negative pole piece and solid-state battery

Abstract

The invention provides a multifunctional conductive binder, a negative pole piece, a preparation method of the negative pole piece and a solid-state battery, and relates to the technical field of solid-state batteries. The raw materials of the multifunctional conductive binder comprise lithium polyacrylate, waterborne polyurethane and polypyrrole; wherein the mass ratio of the lithium polyacrylate to the waterborne polyurethane is (3-7): (7-3); the mass of the polypyrrole is 10-15% of the total mass of the lithium polyacrylate and the waterborne polyurethane. The technical scheme provided by the invention aims to provide good cohesiveness and conductivity. The lithium polyacrylate, the waterborne polyurethane and the polypyrrole are synergistically compounded, so that the huge volume expansion generated in the charging and discharging process of the silicon negative electrode can be effectively coped with.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and in particular to a multifunctional conductive binder, a negative electrode sheet, a method for preparing the same, and a solid-state battery. Background Technology

[0002] Silicon-based anode materials undergo dramatic volume expansion during charge-discharge cycles due to the alloying reaction mechanism, with expansion exceeding 300%. This repeated expansion and contraction process causes multiple damages to the electrode structure: active silicon particles are prone to pulverization and fracture, leading to permanent failure of electrical contact with the current collector; the internal structure of the electrode and the solid-solid interface contact between the electrode and the solid electrolyte are severely damaged, resulting in high contact resistance, hindering the lithium-ion transport path, and causing rapid degradation of battery performance; at the same time, continuous structural damage constantly exposes fresh silicon surfaces, triggering repeated formation and disintegration of the solid electrolyte interface film, consuming a large amount of limited lithium source and electrolyte, resulting in a significant reduction in coulombic efficiency and rapid capacity decay.

[0003] To alleviate the aforementioned problems, existing technologies generally employ a combination of polymer binders (such as polyvinylidene fluoride) and conductive additives (such as carbon black) to maintain electrode structural integrity and electronic pathways. However, this approach has fundamental limitations: traditional binders such as polyvinylidene fluoride have weak intermolecular forces and insufficient mechanical modulus, failing to effectively constrain the movement of silicon particles under high stress, leading to easy breakage of the bonded network; the physical mixing mode of binders and conductive agents is inefficient, with conductive agent particles only forming point contacts with silicon particles, making them prone to separation during volume changes, disrupting the electronic conduction path, and requiring the addition of a high proportion of inert conductive agents (usually exceeding 10%) to maintain conductivity, significantly reducing electrode energy density; furthermore, the existing binder system is mismatched with the mechanical properties of rigid solid electrolytes, failing to buffer interfacial stress and accelerating interfacial delamination. Therefore, there is an urgent need to develop a novel integrated binder material that can dynamically adapt to volume changes and integrate electronic conductivity to solve the structural stability and conductivity challenges of silicon-based anodes in solid-state battery applications.

[0004] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0005] The purpose of this application is to provide a multifunctional conductive binder, a negative electrode sheet, a method for preparing the same, and a solid-state battery to solve the above-mentioned problems.

[0006] To achieve the above objectives, this application adopts the following technical solution: This application provides a multifunctional conductive adhesive, the raw materials of which include lithium polyacrylate, waterborne polyurethane and polypyrrole; The mass ratio of lithium polyacrylate to waterborne polyurethane is 3-7:7-3. The mass of the polypyrrole is 10-15% of the total mass of the lithium polyacrylate and the waterborne polyurethane.

[0007] Optionally, the raw materials of the multifunctional conductive adhesive further include a multivalent metal ion crosslinking agent, wherein the multivalent metal ions include Zn. 2+ Mg 2+ Al 2+ Ca 2+ At least one of them.

[0008] Optionally, the amount of the multivalent metal ion crosslinking agent added is 5-15% of the mass of the lithium polyacrylate.

[0009] This application also provides a negative electrode sheet, the raw materials of which include silicon active material and the multifunctional conductive binder.

[0010] This application also provides a method for preparing a negative electrode sheet, comprising: Prepare an aqueous solution of lithium polyacrylate; mix aqueous polyurethane with the aqueous solution of lithium polyacrylate to obtain a first mixture; Silicon-active material is added to the first mixture, and the mixture is mixed to obtain a slurry; the slurry, pyrrole monomer and oxidant are mixed and polymerized to generate polypyrrole slurry; The slurry is placed on the current collector and dried to obtain the silicon-based anode.

[0011] Optionally, the stirring temperature during the preparation of the lithium polyacrylate aqueous solution is 20-30°C, and the stirring speed is 300-500 rpm.

[0012] Optionally, the stirring temperature during the preparation of the first mixture is 20-30℃, and the stirring speed is 400-600 r / min.

[0013] Optionally, the polymerization reaction is carried out at a temperature of 0-5°C for 3-5 hours.

[0014] Optionally, the drying temperature is 60-70℃ and the time is 12-20h; during the drying process, the ionic crosslinking reaction of the polypyrrole and the lithium polyacrylate is carried out simultaneously.

[0015] Optionally, the oxidant includes ammonium persulfate.

[0016] Optionally, the coating thickness of the slurry is 100-150 μm.

[0017] Optionally, the addition of a multivalent metal ion crosslinking agent to the system may also be included before the addition of the oxidant.

[0018] This application also provides a solid-state battery, including the negative electrode sheet or the negative electrode sheet prepared by the preparation method.

[0019] Compared with the prior art, the beneficial effects of this application include: This application provides a multifunctional conductive binder comprising lithium polyacrylate, aqueous polyurethane, and polypyrrole, designed to provide excellent adhesion and conductivity. By synergistically compounding lithium polyacrylate, aqueous polyurethane, and polypyrrole, the significant volume expansion of the silicon anode during charge and discharge can be effectively addressed. Lithium polyacrylate provides stable adhesion and ion transport capabilities, while the aqueous polyurethane imparts excellent flexibility and elasticity to the binder, thereby buffering mechanical stress and preventing pulverization of the active material and interface damage. Simultaneously, polypyrrole constructs a highly efficient electronic conductive network, ensuring the stability of electron transport within the electrode. Thus, this binder maintains the integrity of the electrode structure, safeguards the transport channels for lithium ions and electrons, thereby improving the cycle stability and coulombic efficiency of the silicon anode and overcoming the limitations of existing binders in solid-state battery applications.

[0020] The negative electrode sheet provided in this application can dynamically adapt to the volume changes of silicon particles during charging and discharging. The elastic network of aqueous polyurethane absorbs expansion stress and prevents the active material from pulverizing; the strong bonding effect of lithium polyacrylate maintains the continuity of electrical contact between silicon particles and the current collector; the conductive network of polypyrrole keeps the electron pathway open during repeated volume changes, avoiding conductive failure caused by point contact separation. Simultaneously, this binder system has good mechanical compatibility with the solid electrolyte, significantly reducing interfacial contact impedance and suppressing side reactions caused by exposure of fresh silicon surfaces, thus effectively solving the problems of structural damage and performance degradation of silicon negative electrodes due to volume expansion. Overall, the negative electrode sheet of this application achieves a synergistic improvement in electrode structural integrity and electron / ion transport stability, providing reliable technical support for the application of high-energy-density silicon-based negative electrodes in solid-state batteries. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0022] Figure 1 This is a schematic diagram of the integrated cross-linked conductive network structure of the negative electrode sheet provided in Example 1. Detailed Implementation

[0023] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0024] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0025] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0026] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0027] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0028] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0029] To better explain the technical solution provided in this application, the technical solution provided in this application will be described in general before the specific implementation.

[0030] Traditional silicon anodes face significant volume expansion during charge and discharge, leading to problems such as active material pulverization, electrical contact failure, interface damage, and rapid capacity decay. To address these challenges, existing binder systems suffer from fundamental defects such as weak molecular chain forces, insufficient modulus, low conductivity, and mismatch with the mechanical properties of solid electrolytes, making it difficult to effectively maintain electrode structural integrity and provide a stable electronic pathway.

[0031] In response, this application proposes a multifunctional conductive adhesive, the raw materials of which include lithium polyacrylate, waterborne polyurethane and polypyrrole; The mass ratio of lithium polyacrylate to waterborne polyurethane is 3-7:7-3. The mass of the polypyrrole is 10-15% of the total mass of the lithium polyacrylate and the waterborne polyurethane.

[0032] Optionally, the mass ratio of lithium polyacrylate to waterborne polyurethane can be 3:7, 4:6, 5:5, 6:4, 7:3, or any value between 3-7:7-3.

[0033] The mass of polypyrrole can be 10%, 11%, 12%, 13%, 14%, or 15% of the total mass of lithium polyacrylate and waterborne polyurethane, or any value between 10% and 15%.

[0034] In an optional embodiment, the raw materials of the multifunctional conductive adhesive further include a multivalent metal ion crosslinking agent, wherein the multivalent metal ions include Zn. 2+ Mg 2+ Al 2+ Ca 2+ At least one of them.

[0035] In one optional embodiment, the amount of the multivalent metal ion crosslinking agent added is 5-15% of the mass of the lithium polyacrylate.

[0036] Optionally, the amount of the multivalent metal ion crosslinking agent added can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15% of the mass of the lithium polyacrylate, or any value between 5% and 15%.

[0037] This application also provides a negative electrode sheet, the raw materials of which include silicon active material and the multifunctional conductive binder.

[0038] The negative electrode sheet provided in this application can dynamically adapt to the volume changes of silicon particles during charging and discharging. The elastic network of aqueous polyurethane absorbs expansion stress and prevents the active material from pulverizing; the strong bonding effect of lithium polyacrylate maintains the continuity of electrical contact between silicon particles and the current collector; the conductive network of polypyrrole keeps the electron pathway open during repeated volume changes, avoiding conductive failure caused by point contact separation. Simultaneously, this binder system has good mechanical compatibility with the solid electrolyte, significantly reducing interfacial contact impedance and suppressing side reactions caused by exposure of fresh silicon surfaces, thus effectively solving the problems of structural damage and performance degradation of silicon negative electrodes due to volume expansion. Overall, the negative electrode sheet of this application achieves a synergistic improvement in electrode structural integrity and electron / ion transport stability, providing reliable technical support for the application of high-energy-density silicon-based negative electrodes in solid-state batteries.

[0039] This application also provides a method for preparing a negative electrode sheet, comprising: Prepare an aqueous solution of lithium polyacrylate; mix aqueous polyurethane with the aqueous solution of lithium polyacrylate to obtain a first mixture; Silicon-active material is added to the first mixture, and the mixture is mixed to obtain a slurry; the slurry, pyrrole monomer and oxidant are mixed and polymerized to generate polypyrrole slurry; The slurry is placed on the current collector and dried to obtain the silicon-based anode.

[0040] In one optional embodiment, the stirring temperature during the preparation of the lithium polyacrylate aqueous solution is 20-30°C, and the stirring speed is 300-500 rpm.

[0041] Optionally, the stirring temperature for preparing the lithium acrylate aqueous solution can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, or 30℃, or any value between 20℃ and 30℃; the stirring speed can be 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm, 400 rpm, 410 rpm, 420 rpm, 430 rpm, 440 rpm, 450 rpm, 460 rpm, 470 rpm, 480 rpm, 490 rpm, or 500 rpm, or any value between 300℃ and 500 rpm.

[0042] In one optional embodiment, the stirring temperature during the preparation of the first mixture is 20-30°C, and the stirring speed is 400-600 r / min.

[0043] Optionally, the stirring temperature during the preparation of the first mixture can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, or 30℃, or any value between 20℃ and 30℃; the stirring speed can be 400 r / min, 410 r / min, 420 r / min, 430 r / min, 440 r / min, 450 r / min, 460 r / min, 470 r / min, 480 r / min, 490 r / min, 500 r / min, 510 r / min, 520 r / min, 530 r / min, 540 r / min, 550 r / min, 560 r / min, 570 r / min, 580 r / min, 590 r / min, or 600 r / min, or any value between 400 and 600 r / min.

[0044] In one optional embodiment, the polymerization reaction is carried out at a temperature of 0-5°C for a time of 3-5 hours.

[0045] Optionally, the temperature of the polymerization reaction can be 0°C, 1°C, 2°C, 3°C, 4°C, 5°C, or any value between 0°C and 5°C.

[0046] In one optional embodiment, the drying temperature is 60-70°C and the time is 12-20 hours; during the drying process, the ionic crosslinking reaction of the polypyrrole and the lithium polyacrylate is carried out simultaneously.

[0047] In an optional embodiment, the oxidant comprises ammonium persulfate.

[0048] In one optional embodiment, the coating thickness of the slurry is 100-150 μm.

[0049] In an optional embodiment, the addition of a multivalent metal ion crosslinking agent to the system prior to the addition of the oxidant is further included.

[0050] This application also provides a solid-state battery, including the negative electrode sheet or the negative electrode sheet prepared by the preparation method.

[0051] Understandably, the core challenge faced by traditional silicon anodes in solid-state battery applications stems from their volume expansion exceeding 300% during charge and discharge. This leads to the pulverization and cracking of active silicon particles, disruption of the solid-solid interface contact between the electrode and the solid electrolyte, interruption of lithium-ion transport channels, and repeated proliferation and collapse of the solid electrolyte interface, ultimately resulting in rapid capacity decay and low coulombic efficiency. Existing technologies rely on the physical mixing mode of traditional polymer binders and conductive agents, which suffers from defects such as weak molecular chain forces, insufficient modulus, easy breakage of electronic pathways, and mismatch with the mechanical properties of the solid electrolyte, making it difficult to effectively maintain the integrity of the electrode structure and stable conductivity. This application provides a solid-state battery, including the aforementioned anode sheet or the anode sheet prepared by the aforementioned method. The core innovation of this embodiment lies in integrating a multifunctional conductive binder into the anode structure. This binder is a synergistic system composed of lithium polyacrylate, aqueous polyurethane, and polypyrrole in a specific mass ratio, thereby simultaneously achieving the triple functions of mechanical buffering, interface stabilization, and electronic conduction during the dynamic volume change of the silicon anode. This effectively suppresses the pulverization of active materials and interface peeling, significantly improving the cycle stability and energy density of the solid-state battery.

[0052] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0053] Example 1 This embodiment provides a multifunctional conductive adhesive: Its raw materials include lithium polyacrylate, waterborne polyurethane, polypyrrole, and ZnSO4·7H2O crosslinking agent; wherein the mass ratio of lithium polyacrylate to waterborne polyurethane is 7:3, and the amount of ZnSO4·7H2O crosslinking agent is 10% of the mass of lithium polyacrylate.

[0054] This embodiment also provides a negative electrode sheet, the specific steps of which are as follows: Preparation of lithium-ionized polyacrylic acid (PAA-Li) solution: Accurately weigh 0.21 g of PAA powder, dissolve it in an appropriate amount of deionized water, and stir magnetically until completely dissolved. Calculate and weigh the corresponding mass of LiOH·H2O based on the 100% neutralization degree of PAA carboxyl groups, dissolve it in water, and slowly add it dropwise to the PAA solution at room temperature with stirring at 400 rpm. Continue stirring for 2 hours to obtain a clear PAA-Li solution.

[0055] Construction of the hybrid binder network: Add 0.09 g of WPU to the PAA-Li solution and stir vigorously (700 rpm) for 2 hours to ensure thorough mixing. Then add ZnSO4·7H2O crosslinking agent at 10% of the mass of PAA solids and continue stirring (500 rpm) for 1 hour for pre-crosslinking.

[0056] Preparation of slurry and introduction of pyrrole monomer: 0.7 g of nano-silica powder was added to the polymer solution in portions. After each addition, the mixture was manually ground and stirred with a spatula to ensure that the silica particles were fully wetted and coated to obtain a uniform slurry. Subsequently, 0.04 g of pyrrole (Py) monomer was added using a pipette, and the mixture was ground and stirred for another 30 minutes to ensure that Py was uniformly dispersed throughout the network.

[0057] In-situ polymerization and coating drying: 0.10 g of ammonium persulfate (APS) was dissolved in 0.5 ml of water to prepare an oxidant solution. Under ice-water bath cooling and stirring (400 rpm), the APS solution was rapidly poured into the slurry. The slurry quickly turned black, indicating the beginning of polypyrrole formation. The reaction was continued for 4 hours to ensure complete polymerization. The final slurry was coated onto copper foil, controlling the wet film thickness to 150 μm. The electrode was then placed in a 60°C forced-air drying oven for 12 hours. During this process, the crosslinking and polymerization reactions were completed simultaneously and thoroughly, forming a three-dimensional integrated network. A schematic diagram of the integrated crosslinked conductive network structure is shown below. Figure 1 As shown.

[0058] Post-processing: The dried electrode sheets are vacuum dried at 120°C for 6 hours to completely remove moisture and are ready for use.

[0059] This embodiment also provides a solid-state battery: The positive electrode active material is NCM. 111 The ternary cathode material uses a sulfide electrolyte, Li7P3S. 11 The conductive agent is conductive carbon black SP. In a glove box, the positive electrode powder, conductive agent and electrolyte are uniformly mixed in a ratio of 70:10:20 and then formed into sheets under high pressure in a mold battery.

[0060] Example 2 This embodiment provides a multifunctional conductive adhesive: Its raw materials include lithium polyacrylate, waterborne polyurethane, polypyrrole, and ZnSO4·7H2O crosslinking agent; wherein the mass ratio of lithium polyacrylate to waterborne polyurethane is 5:5, and the amount of ZnSO4·7H2O crosslinking agent is 10% of the mass of lithium polyacrylate.

[0061] This embodiment also provides a negative electrode sheet, the specific steps of which are as follows: Preparation of lithium-ionized polyacrylic acid (PAA-Li) solution: Accurately weigh 0.15 g of PAA powder, dissolve it in an appropriate amount of deionized water, and stir magnetically until completely dissolved. Calculate and weigh the corresponding mass of LiOH·H2O based on the 100% neutralization degree of PAA carboxyl groups, dissolve it in water, and slowly add it dropwise to the PAA solution at room temperature with stirring at 400 rpm. Continue stirring for 2 hours to obtain a clear PAA-Li solution.

[0062] Construction of the hybrid binder network: Add 0.15 g of WPU to the PAA-Li solution and stir vigorously (700 rpm) for 2 hours to ensure thorough mixing. Then add ZnSO4·7H2O crosslinking agent at 10% of the mass of PAA solids and continue stirring (500 rpm) for 1 hour for pre-crosslinking.

[0063] Preparation of slurry and introduction of pyrrole monomer: 0.7 g of nano-silica powder was added to the polymer solution in portions. After each addition, the mixture was manually ground and stirred with a spatula to ensure that the silica particles were fully wetted and coated to obtain a uniform slurry. Subsequently, 0.04 g of pyrrole (Py) monomer was added using a pipette, and the mixture was ground and stirred for another 30 minutes to ensure that Py was uniformly dispersed throughout the network.

[0064] In-situ polymerization and coating drying: 0.10 g of ammonium persulfate (APS) was dissolved in 0.5 ml of water to prepare an oxidant solution. Under ice-water bath cooling and stirring (400 rpm), the APS solution was rapidly poured into the slurry. The slurry quickly turned black, indicating the beginning of polypyrrole formation. The reaction was continued for 4 hours to ensure complete polymerization. The final slurry was coated onto copper foil, controlling the wet film thickness to 150 μm. The electrode was then placed in a 60°C forced-air drying oven for 12 hours. During this process, the crosslinking and polymerization reactions were completed simultaneously and thoroughly, forming a three-dimensional integrated network.

[0065] Post-processing: The dried electrode sheets are vacuum dried at 120°C for 6 hours to completely remove moisture and are ready for use.

[0066] This embodiment also provides a solid-state battery: The positive electrode active material is NCM. 111 The ternary cathode material uses a sulfide electrolyte, Li7P3S. 11 The conductive agent is conductive carbon black SP. In a glove box, the positive electrode powder, conductive agent and electrolyte are uniformly mixed in a ratio of 70:10:20 and then formed into sheets under high pressure in a mold battery.

[0067] Example 3 This embodiment provides a multifunctional conductive adhesive: Its raw materials include lithium polyacrylate, waterborne polyurethane, polypyrrole, and ZnSO4·7H2O crosslinking agent; wherein the mass ratio of lithium polyacrylate to waterborne polyurethane is 3:7, and the amount of ZnSO4·7H2O crosslinking agent is 10% of the mass of lithium polyacrylate.

[0068] This embodiment also provides a negative electrode sheet, the specific steps of which are as follows: Preparation of lithium-ionized polyacrylic acid (PAA-Li) solution: Accurately weigh 0.09 g of PAA powder, dissolve it in an appropriate amount of deionized water, and stir magnetically until completely dissolved. Calculate and weigh the corresponding mass of LiOH·H2O based on the 100% neutralization degree of PAA carboxyl groups, dissolve it in water, and slowly add it dropwise to the PAA solution at room temperature with stirring at 400 rpm. Continue stirring for 2 hours to obtain a clear PAA-Li solution.

[0069] Construction of the hybrid binder network: Add 0.21 g of WPU to the PAA-Li solution and stir vigorously (700 rpm) for 2 hours to ensure thorough mixing. Then add ZnSO4·7H2O crosslinking agent at 10% of the mass of PAA solids and continue stirring (500 rpm) for 1 hour for pre-crosslinking.

[0070] Preparation of slurry and introduction of pyrrole monomer: 0.7 g of nano-silica powder was added to the polymer solution in portions. After each addition, the mixture was manually ground and stirred with a spatula to ensure that the silica particles were fully wetted and coated to obtain a uniform slurry. Subsequently, 0.04 g of pyrrole (Py) monomer was added using a pipette, and the mixture was ground and stirred for another 30 minutes to ensure that Py was uniformly dispersed throughout the network.

[0071] In-situ polymerization and coating drying: 0.10 g of ammonium persulfate (APS) was dissolved in 0.5 ml of water to prepare an oxidant solution. Under ice-water bath cooling and stirring (400 rpm), the APS solution was rapidly poured into the slurry. The slurry quickly turned black, indicating the beginning of polypyrrole formation. The reaction was continued for 4 hours to ensure complete polymerization. The final slurry was coated onto copper foil, controlling the wet film thickness to 150 μm. The electrode was then placed in a 60°C forced-air drying oven for 12 hours. During this process, the crosslinking and polymerization reactions were completed simultaneously and thoroughly, forming a three-dimensional integrated network.

[0072] Post-processing: The dried electrode sheets are vacuum dried at 120°C for 6 hours to completely remove moisture and are ready for use.

[0073] This embodiment also provides a solid-state battery: The positive electrode active material is NCM. 111 The ternary cathode material uses a sulfide electrolyte, Li7P3S. 11The conductive agent is conductive carbon black SP. In a glove box, the positive electrode powder, conductive agent and electrolyte are uniformly mixed in a ratio of 70:10:20 and then formed into sheets under high pressure in a mold battery.

[0074] Comparative Example 1 The only difference between this comparative example and Example 1 is that the ratio of PAA-Li to WPU is 10:0.

[0075] Comparative Example 2 The only difference between this comparative example and Example 1 is that the ratio of PAA-Li to WPU is 0:10.

[0076] Comparative Example 3 The only difference between this comparative example and Example 1 is that the ratio of CMC to SBR in the adhesive system is 1:1, and the adhesive and conductive agent are physically mixed.

[0077] Comparative Example 4 The only difference between this comparative example and Example 1 is that the adhesive system uses only PAA-Li, and the adhesive and conductive agent are physically mixed.

[0078] Comparative Example 5 The only difference between this comparative example and Example 1 is that the adhesive system uses only WPU, and the adhesive and conductive agent are physically mixed.

[0079] The test results of mechanical strength and electronic conductivity of the electrodes of each embodiment and comparative example are shown in Table 1: Table 1 Mechanical strength and electronic conductivity tests of the electrodes

[0080] The electrochemical performance of the negative electrode is shown in Table 2: Table 2 Electrochemical performance of the negative electrode sheet

[0081] From Tables 1 and 2, we can see that: Mechanical strength: Examples 1 and 2 exhibited the highest peel strength, demonstrating the dominant role of the rigid skeleton (PAA-Li) and ionic crosslinking in enhancing adhesion, and the addition of the flexible component (WPU) did not significantly weaken its strength.

[0082] Electronic conductivity: The conductivity of all integrated in-situ polymerized groups far exceeded that of all physically mixed groups, demonstrating the superiority of in-situ generation of PPy nano-conductive networks.

[0083] First-week coulombic efficiency (ICE): Example 2 exhibited the highest first-week efficiency, demonstrating that its integrated network most effectively suppresses silicon particle breakage and side reactions during the formation stage, reducing irreversible consumption of active lithium. Comparative Example 5 (physically mixed PPy) had the most severe side reactions and the lowest ICE due to interfacial instability.

[0084] Example 2 demonstrates a significantly higher capacity retention rate, highlighting the substantial advantage of the "rigid-flexible" structure in maintaining electrode integrity under long-term, large-volume strain. The purely rigid (Comparative Examples 1 and 4) or purely flexible (Comparative Examples 2 and 5) systems exhibited poor cycling performance.

[0085] All embodiments exhibit significantly superior rate performance compared to the comparative example. This is directly attributable to their superior intrinsic electronic conductivity, ensuring rapid charge transport at high rates with minimal polarization. The comparative example relies on a physically mixed, easily failing conductive network, resulting in poor rate performance.

[0086] A lower Rct value indicates a healthier electrode interface and easier charge transfer. Example 2 showed the lowest Rct value and the slowest increase, demonstrating that its interface remained stable after long-term cycling. The comparative examples (especially Comparative Example 5) exhibited large and rapidly increasing Rct values, indicating continuous interface deterioration and deactivation of the active material, which is the fundamental reason for the sharp capacity decay.

[0087] In summary, the PPy / PAA-Li / WPU integrated conductive binder described in this invention (especially Example 2) significantly outperforms traditional physically mixed binder systems in terms of first-efficiency performance, cycle life, rate performance, and interface stability. Its "mechanical-electronic" synergistic network, constructed through chemical fusion, is an effective strategy for addressing the core bottlenecks of silicon-based anodes and propelling them towards practical applications.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0089] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A multifunctional conductive adhesive, characterized in that, The raw materials of the multifunctional conductive adhesive include lithium polyacrylate, waterborne polyurethane and polypyrrole. The mass ratio of lithium polyacrylate to waterborne polyurethane is 3-7:7-3. The mass of the polypyrrole is 10-15% of the total mass of the lithium polyacrylate and the waterborne polyurethane.

2. The multifunctional conductive adhesive according to claim 1, characterized in that, The raw materials of the multifunctional conductive adhesive also include a multivalent metal ion crosslinking agent, wherein the multivalent metal ions include Zn. 2+ Mg 2+ Al 2+ Ca 2+ At least one of them.

3. The multifunctional conductive adhesive according to claim 2, characterized in that, The amount of the multivalent metal ion crosslinking agent added is 5-15% of the mass of the lithium polyacrylate.

4. A negative electrode sheet, characterized in that, Its raw materials include silicon-active materials and the multifunctional conductive binder as described in any one of claims 1-3.

5. A method for preparing the negative electrode sheet according to claim 4, characterized in that, include: Prepare an aqueous solution of lithium polyacrylate; mix aqueous polyurethane with the aqueous solution of lithium polyacrylate to obtain a first mixture; Silicon-active material is added to the first mixture, and the mixture is then mixed to obtain a slurry. The slurry, pyrrole monomer, and oxidant are mixed and subjected to a polymerization reaction to generate polypyrrole slurry; The slurry is placed on the current collector and dried to obtain the negative electrode sheet.

6. The method for preparing the negative electrode sheet according to claim 5, characterized in that, At least one of the following conditions must be met: A. The stirring temperature during the preparation of the lithium polyacrylate aqueous solution is 20-30℃, and the stirring speed is 300-500 rpm; B. The stirring temperature during the preparation of the first mixture is 20-30℃, and the stirring speed is 400-600 r / min; C. The polymerization reaction is carried out at a temperature of 0-5℃ for 3-5 hours. D. The drying temperature is 60-70℃ and the time is 12-20h; during the drying process, the ionic crosslinking reaction of the polypyrrole and the lithium polyacrylate is carried out simultaneously.

7. The method for preparing the negative electrode sheet according to claim 5, characterized in that, The oxidant includes ammonium persulfate.

8. The method for preparing the negative electrode sheet according to claim 5, characterized in that, The coating thickness of the slurry is 100-150 μm.

9. The method for preparing the negative electrode sheet according to any one of claims 5-8, characterized in that, Before adding the oxidant, a multivalent metal ion crosslinking agent is also added to the system.

10. A solid-state battery, characterized in that, Includes the negative electrode sheet as described in claim 4 or the negative electrode sheet prepared by the preparation method described in any one of claims 5-9.

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