Silicon anode for all-solid-state battery and all-solid-state battery

Abstract

The application discloses a silicon negative electrode for a full solid-state battery and the full solid-state battery, and belongs to the field of battery materials. The silicon negative electrode comprises a current collector and a silicon negative electrode slurry attached to the current collector. The silicon negative electrode slurry is composed of a silicon active material, a conductive additive and a binder. The binder comprises a viscous polymer and a lithium salt. The viscous polymer is obtained by reacting a polyether polyol with a diisocyanate to form an NCO-terminated prepolymer, and then reacting with a chain extender containing at least two active hydrogen functional groups that can react with isocyanate groups to form urea bonds / urethane bonds. The polymer has ether oxygen soft segments and isocyanate hard segments, and the internal rich hydrogen bond network gives it high elasticity and mechanical stability, which can effectively adapt to and inhibit the volume expansion of the silicon negative electrode in the cycle, maintain the integrity of the electrode structure and the continuity of the ion transmission channel under low pressure, thereby significantly improving the cycle performance of the full solid-state battery.

Description

Technical Field

[0001] This invention belongs to the field of battery materials and relates to a silicon anode for all-solid-state batteries and all-solid-state batteries. Background Technology

[0002] Since their commercialization, lithium-ion batteries have been widely used in mobile phones, computers, electric vehicles, and other fields, promoting a transformation in people's lifestyles. However, traditional lithium-ion batteries use organic electrolytes as their electrolytes, which pose safety hazards such as leakage, flammability, and explosion. Furthermore, their energy density has reached its theoretical limit, making further breakthroughs difficult. In contrast, all-solid-state batteries use solid electrolyte materials as their separators, which not only solves safety issues but also allows for compatibility with lithium metal and silicon anodes and high-voltage cathodes, further improving the battery's energy density.

[0003] Currently, lithium metal anodes are considered one of the most promising solid-state battery anode materials due to their highest theoretical specific capacity and lowest electrochemical potential. However, they still face key challenges in solid-state systems, such as interfacial instability and lithium dendrite growth during cycling, making it difficult to achieve long-term stable operation under high current and high areal capacity conditions. In contrast, silicon anodes have extremely high theoretical specific capacity and suitable operating potential, and are less prone to dendrite formation, making them a promising alternative to lithium metal anodes. Currently, silicon anodes in all-solid-state batteries mainly exist as pure silicon electrodes or silicon-solid electrolyte-conductive agent composite electrodes, where the sulfide electrolyte and conductive additives respectively handle ion and electron transport functions. However, silicon materials have limited intrinsic ion diffusion and electronic conductivity, and significant volume expansion during charge and discharge leads to rapid deterioration of the electrode structure and interfacial contact. This requires batteries to withstand external pressures as high as 50-150 MPa to maintain cycle stability, severely limiting their practical application. Especially in low-pressure solid-state batteries, the reduction in external pressure makes silicon materials more prone to volume expansion, and the loss of high pressure increases the bonding distance between particles, thus reducing the ion transport capacity of the entire silicon anode. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a silicon anode for all-solid-state batteries and an all-solid-state battery, so as to solve the technical problems that silicon anodes are difficult to apply in solid-state batteries, especially low-pressure solid-state batteries, due to their easy volume expansion and low ionic conductivity.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A silicon anode for all-solid-state batteries includes a current collector and a silicon anode slurry attached to the current collector. The silicon anode slurry includes a silicon active material, a conductive additive, and a binder. The binder includes a viscous polymer and a lithium salt. The preparation process of the viscous polymer is as follows: first, the terminal hydroxyl groups of a polyether polyol react with the isocyanate groups of a diisocyanate monomer to generate a prepolymer with NCO terminal groups; then, at least two active hydrogen functional groups at both ends of a chain extender molecule react with the residual NCO groups in the prepolymer to form urea bonds or urethane bonds, thereby achieving chain extension of the molecular chain.

[0006] A further improvement of the present invention is that: Preferably, the mass ratio of the silicon active material, conductive carbon black and binder is (70~90):(5~20):(5~10).

[0007] Preferably, the conductive additive is any one of vapor-grown carbon fiber, conductive carbon black, or carbon nanotubes, and the silicon active material is silicon particles.

[0008] Preferably, the molar ratio of the diisocyanate monomer, polyether polyol and chain extender is (2-5):(1-2):(0.5-3).

[0009] Preferably, based on the total mass of the adhesive, the mass fraction of lithium salt in the adhesive is 20wt%-60wt%, and the remainder is a viscous polymer.

[0010] Preferably, the lithium salt is at least one selected from lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0011] Preferably, the polyether polyol is any one of polytetrahydrofuran, polyethylene glycol, and polyethylene oxide.

[0012] Preferably, the diisocyanate monomer is any one of isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate.

[0013] Preferably, the chain extender is any one of dihydroxyethyl urea or its derivatives, dihydroxypropyl urea or its derivatives, or biuret or its derivatives.

[0014] An all-solid-state battery includes a positive electrode, a silicon negative electrode for an all-solid-state battery as described in any one of the above-mentioned methods, and a sulfide solid electrolyte disposed between the positive electrode and the silicon negative electrode.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a silicon anode for all-solid-state batteries. The binder in this silicon anode is composed of a viscous polymer and a lithium salt. The polymer is obtained by addition polymerization of soft segments containing ether oxygen bonds and hard segments containing isocyanates to obtain a prepolymer, which is then crosslinked with a chain extender containing at least two active hydrogen functional groups that can react with isocyanate groups to obtain an elastomer. By adjusting the -NCO / -OH ratio and the chain extender feed ratio to change the volume fraction, aggregation state, and hydrogen bond network density of the hard segment domain in the polyurethane system, and by adjusting the type and proportion of lithium salt to control the ion transport network and the inorganic rigid layer, a class of binders with different soft and hard segment microphase structures and different ion transport capabilities can be achieved. When all-solid-state batteries cycle under low pressure, on the one hand, the polymer in the binder of this invention possesses excellent mechanical properties, and its abundant internal hydrogen bonds can constrain the volume change of silicon particles during massive expansion, preventing particle structure collapse and electrode failure. On the other hand, the lithium salt in the binder can decompose on the surface of silicon particles to form an inorganic rigid layer, which, together with the outer polymer layer, alleviates the volume change and stress impact of silicon during charge and discharge, further ensuring the structural stability of the silicon electrode during low-pressure cycling. Furthermore, the polymer also has high ion transport performance, which can work with the lithium salt to construct rapid ion transport channels within the electrode, shortening the migration distance of ions throughout the electrode. Even under low-pressure cycling conditions (≤30 MPa), continuous and interconnected ion transport channels can be maintained within the electrode, ultimately achieving high electrode capacity. This binder overcomes the low-pressure operation bottleneck of silicon-based all-solid-state batteries, constructing an internal and interface structure of the electrode that combines mechanical stability with efficient ion / electron transport capabilities. It can buffer the volume change of silicon during cycling and maintain the continuity of ion and electron transport channels under low applied pressure, thereby significantly improving the cycle stability and feasibility of the battery.

[0016] The binder used in the silicon anode of this invention is simple to synthesize, providing a new approach for the development of silicon anodes for all-solid-state batteries. By designing a binder with both high ionic conductivity and high mechanical properties, a three-dimensional ion transport pathway is formed inside the electrode. Simultaneously, thanks to the excellent mechanical properties, a silicon-based all-solid-state battery capable of stable cycling under low pressure is obtained; it also has the following advantages: (1) The binder prepared by this invention has segments rich in ether oxygen bonds, which can promote the dissociation and transport of lithium ions, thus enabling the binder in Example 1 to have a strength of 3.7 × 10⁻⁶. -5 The ionic conductivity is S / cm. High ionic conductivity can create continuous three-dimensional ion transport channels inside the silicon electrode, maintaining effective ion contact between silicon particles and at the electrode / electrolyte interface even under low pressure conditions, significantly reducing interfacial transport impedance.

[0017] (2) The binder prepared in this invention contains lithium salt. On the one hand, during low-potential cycling, lithium salt can decompose in situ at the silicon particle interface to generate inorganic products such as LiF, Li3N and Li2O. This layer has high ionic conductivity and mechanical strength, and presents a "mosaic" distribution to form a stable interface protection layer. On the other hand, the surface elastic polymer covers the outer layer to present an amorphous region, which, together with the rigid layer, uniformly covers the silicon particle surface to form a "rigid and flexible" interface layer, providing inorganic-organic dual protection and realizing the stable operation of silicon-based all-solid-state batteries under low pressure.

[0018] (3) The binder prepared by the present invention has excellent mechanical properties and can constrain the bulk reversible deformation ability of silicon electrodes and the interface stability between silicon particles during long-term cycling, and maintain the elastic displacement of the silicon particle interface.

[0019] (4) The silicon electrode stores a large number of lithium ions, which can shorten the migration distance of lithium ions throughout the electrode during the charging and discharging process, build a fast ion channel, and realize high-rate cycling and high capacity of the battery. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the synthesis of the binder in Example 1 of a silicon-based solid-state battery. Figure 2 Infrared image of the binder in Example 1 of silicon-based solid-state battery; Figure 3 The graph shows the cycle performance of silicon-based solid-state batteries Example 1 and Comparative Example 1 at 10 MPa and 2C rate. Figure 4 Electrochemical performance of silicon-based solid-state full cell Example 1 at 5 MPa; Figure 5 Electrochemical impedance spectroscopy for Example 1 and Comparative Example 1; Figure 6 The load-depth displacement curves obtained by nanoindentation for Example 1 and Comparative Example 1 are shown. Figure 7 The images show the HRTEM and corresponding local Fast Fourier Transform images of silicon anode Example 1 and Comparative Example 1 after cycling. Figure 8 Cross-sectional scan images of Example 1 and Comparative Example 1 of silicon-based solid-state batteries before and after cycling. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings: To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0022] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if 60 is listed for a specific parameter... 120 and 80 The range of 110 is understood to be 60. 110 and 80 The range of 120 is also expected. Furthermore, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1 3.1 4.1 5.2 3, 2 4 and 2 5. In this application, unless otherwise stated, the numerical range "a" "b" represents a shortened representation of any combination of real numbers from a to b, where both a and b are real numbers. For example, the numerical range "0" represents a combination of real numbers from a to b. "5" indicates that all "0"s have been listed in this article. All real numbers between "5" and "0". "5" is simply an abbreviation for these numerical combinations. In addition, when a parameter is expressed as an integer greater than or equal to 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0023] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" is not vertical in the strict sense, but within the allowable tolerance range. "Parallel" is not parallel in the strict sense, but within the allowable tolerance range.

[0024] The directional terms used in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of this application. It should also be noted in the description of this application that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0025] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0026] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B".

[0027] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0028] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0029] The first aspect of the present invention discloses a silicon anode for an all-solid-state battery, comprising a current collector and a silicon anode slurry attached to the current collector. The silicon anode slurry comprises a silicon active material, a conductive additive, and a binder. The binder comprises a viscous polymer and a lithium salt. The viscous polymer is prepared by reacting the terminal hydroxyl groups of a polyether polyol with the isocyanate groups of a diisocyanate monomer to form an NCO-terminated prepolymer. The NCO-terminated prepolymer is extended by reacting at least two active hydrogen functional groups at both ends of a chain extender, which can react with the isocyanate groups, with the residual NCO groups to form urea bonds or urethane bonds.

[0030] The binder prepared in this invention introduces soft segments containing ether oxygen bonds and hard segments containing isocyanates, which combine through addition polymerization to form a polyurethane with excellent mechanical properties. Further chain extenders are used to enhance the polymer's mechanical properties. The synergistic combination of soft and hard segments within the polymer, along with abundant hydrogen bonds, imparts excellent tensile properties and elastic deformation capabilities, adapting to the stress generated in the silicon electrode during cycling. The cascade dissociation and reconstruction of multiple hydrogen bonds formed by the binder and the silicon anode effectively dissipates stress between adjacent particles, transforming the rigid point contact interface in the silicon anode into a conformal and recoverable highly transport elastic contact, thus promoting the structural stability of the silicon electrode under low pressure cycling.

[0031] A specific example discloses a method for preparing the adhesive, including the following steps: Step 1: Place the polyether polyol in a sealed two-necked flask, heat and stir, and then vacuum to completely remove the water to obtain solution A; Step 2: Dissolve the diisocyanate monomer and dibutyltin dilaurate catalyst in ultra-dry N,N-dimethylformamide, and inject it into solution A from step 1. React at -80℃ for 3 hours until polymerization is complete to obtain binder prepolymer B. The amount of dibutyltin dilaurate catalyst added is 3wt‰-5wt‰ of the total amount of polytetrahydrofuran, isophorone diisocyanate and ultra-dry N,N-dimethylformamide.

[0032] Step 3: Dissolve the chain extender in ultra-dry N,N-dimethylformamide and inject it into solution B from step 2. React at 40°C for 3-5 hours until polymerization is complete to obtain pure polymer binder C.

[0033] Step 4: Dry the polymer solution from Step 3 in a vacuum oven at 70°C for 12 hours to obtain a dry polymer. Dissolve the dry polymer and lithium salt in ultra-dry N,N-dimethylformamide to obtain an active polymer binder solution, and then dry it to obtain a polymer binder film.

[0034] In some real-time solutions of the present invention, the mass ratio of silicon active material, conductive additive and binder is (70~90):(5~20):(5~10).

[0035] In some embodiments of the present invention, the molar ratio of the diisocyanate monomer, the polyether polyol and the chain extender is (2-5):(1-2):(0.5-3).

[0036] In some embodiments of the present invention, the mass fraction of lithium salt in the binder is 20wt%-60wt%; preferably 20wt%-40wt%, and most preferably 20wt%±5%.

[0037] In some embodiments of the present invention, the lithium salt is at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0038] In some embodiments of the present invention, the polyether polyol is any one of polytetrahydrofuran, polyethylene glycol, and polyethylene oxide.

[0039] In some embodiments of the present invention, the diisocyanate monomer is any one of isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate.

[0040] In some embodiments of the present invention, the chain extender is dihydroxyethyl urea or a derivative thereof, dihydroxypropyl urea or a derivative thereof, or biuret or a derivative thereof. Specifically, dihydroxyethyl urea or a derivative thereof, and dihydroxypropyl urea or a derivative thereof simultaneously contain a terminal hydroxyl group (-OH) and a urea bond (-NHCONH-), which undergo an addition reaction with isocyanate groups to form a carbamate bond for chain extension; biuret or a derivative thereof has urea nitrogen atoms containing active hydrogen atoms at both ends, which undergo an addition reaction with isocyanate groups to form a urea bond for chain extension.

[0041] In one specific example, an adhesive is disclosed comprising a polymer PU and a lithium salt, wherein the polymer PU is a polymer formed by addition polymerization of polytetrahydrofuran soft segments and isophorone diisocyanate hard segments; the molecular formula of the polymer is:

[0042] Where n is 30-50 and m is 60-80.

[0043] The mechanical properties of this example derive from the hydrogen bonding between the nitrogen-containing functional groups in biuret and isophorone diisocyanate and the surrounding hydrogen. Polytetrahydrofuran, as a soft segment, contributes high ionic conductivity to the binder through the coordination of its ether bonds with lithium ions and the movement of the polytetrahydrofuran segments. Introducing lithium salts into the binder provides lithium ions, and during cycling, some of the lithium salts are reduced on the silicon particle surface to form an inorganic-rich layer, creating a "rigid-flexible" interface layer with the polymer. This protects the structural stability of the silicon anode during all-solid-state battery cycling and improves the battery's rate performance.

[0044] In some embodiments of the present invention, the preparation temperature of the viscous polymer is 40~80℃, preferably 40℃.

[0045] In some embodiments of the present invention, the conductive additive is any one of vapor-grown carbon fiber, conductive carbon black, or carbon nanotubes, and the silicon active material is silicon particles.

[0046] Furthermore, the coating thickness of the negative electrode slurry is 150-300 μm; the particle size of the silicon active material is 30nm-1μm.

[0047] An all-solid-state battery includes a positive electrode, a silicon negative electrode as described in any one of the above, and a sulfide solid electrolyte disposed between the positive electrode and the silicon negative electrode.

[0048] The all-solid-state battery anode includes a copper current collector and a silicon anode slurry attached to the copper current collector. The silicon anode slurry is obtained by ball milling a mixture of silicon active material, conductive carbon black, binder and ultra-dry N,N-dimethylformamide.

[0049] A specific example of the present invention provides a method for preparing a polymer binder, which specifically includes the following steps: Step 1, Dehydration of the precursor. Place 1-2 mmol of polytetrahydrofuran (PTMEG) in a two-necked flask, sealing one flask and connecting the other flask to a dual-purpose vacuum and atmosphere-purifying pipe. Place the sealed flask containing PTMEG in an oil bath on a stirrer equipped with a magnetic stirrer. Stir at 105°C and evacuate under vacuum for 1-3 hours to remove water from the PTMEG, obtaining solution A. Step 2, Synthesis of the binder prepolymer. After completing the above steps, lower the temperature to 80℃ and wait for use. Close the vacuum valve and introduce high-purity nitrogen gas, repeating the evacuation process three times, ensuring appropriate pressure in both flasks. Weigh 2-5 mmol of isophorone diisocyanate (IPDI) and 3-5 wt‰ of dibutyltin dilaurate (DBTDL) catalyst (based on the total mass of the monomers polytetrahydrofuran and isophorone diisocyanate), dissolve them in 10 ml of ultra-dry N,N-dimethylformamide, and slowly inject the ultra-dry dimethylformamide solution into the dehydrated polytetrahydrofuran precursor over 30 min using a vacuum-dried syringe, stirring continuously to obtain prepolymer B. Continuously introduce high-purity nitrogen gas during the reaction and react for 2 h. In this reaction, the hydroxyl groups (-OH) at both ends of PTMEG undergo an addition reaction with the isocyanate groups (-NCO) of IPDI (the core reaction in polyurethane synthesis: the hydroxy-isocyanate reaction), forming urethane bonds (-NH-CO-O-). The final product is an isocyanate-terminated polyurethane prepolymer: the molecular backbone is a flexible polyether segment of PTMEG, connected to the cyclic structure of IPDI at both ends, and retains unreacted -NCO groups at the ends, which can be used for further chain extension or crosslinking. The main reactions are as follows:

[0050] Step 3, Synthesis of Pure Polymer Adhesive. After Step 2 is completed, 0.5-1.5 mmol of biuret is dissolved in 1-3 ml of ultra-dry dimethylformamide solution. Under stirring, the dimethylformamide solution containing biuret is slowly injected into the adhesive prepolymer solution from Step 2 over 30 min. The reaction is continued for 3-5 h under a nitrogen atmosphere at a temperature of 40℃-80℃ to obtain pure polymer adhesive C. During this reaction, the -NCO groups at the ends of the prepolymer undergo an addition reaction with the -NH2 groups of the chain extender (biuret) to form urea bonds (-NH-CO-NH-), connecting multiple prepolymer molecules and achieving chain extension. The main reactions are as follows:

[0051] Step 4, Preparation of the active polymer binder. The binder prepared in Step 3 is dried in a vacuum oven at 70°C for 12 hours to obtain an elastic dry polymer, ensuring the accuracy of the polymer concentration in later stages. To prepare the active polymer binder, the polymer is dissolved in 1-3 ml of ultra-dry N,N-dimethylformamide solvent, and 20wt%-60wt% of LiFSI salt relative to the dry polymer is introduced. After dissolution, an active polymer binder solution is obtained. The solution is poured into a polytetrafluoroethylene mold and dried at 70°C for 12-24 hours to obtain... This invention also provides a method for preparing a silicon anode for all-solid-state batteries, comprising silicon particulate material, conductive carbon additive, and the binder described in the above-mentioned technical solution. The specific steps are as follows: Step 1: Weigh the silicon active material, conductive carbon black and binder in the glove box according to the mass ratio of (70~90):(5~20):(5~10), and disperse the components evenly in the ultra-dry dimethylformamide solution through a planetary ball mill to form a uniform electrode slurry with suitable viscosity. Step 2: Using an automated coating machine in a glove box, the slurry from Step 1 is coated onto an 8 μm copper foil. The coating thickness is set to 150–300 μm, and the foil is vacuum-dried overnight at 70°C. After deducting the mass of the copper foil, the silicon electrode loading is 0.6 mg / cm³. 2 ~1.5 mg / cm 2 ; Step 3: Cut the dried silicon anode sheet from Step 2 into 12mm diameter sheets using a manual cutting machine, and transfer them to a glove box filled with argon gas (O2 < 0.1ppm, H2O < 0.1ppm) for storage.

[0052] This invention also provides a method for preparing a positive electrode for a silicon-based all-solid-state battery, comprising a positive electrode active material, a conductive additive, and an ion conductor. The specific preparation steps are as follows: Step 1: In a glove box, prepare the active material and ionic conductor at a mass ratio of (60~70):(30~40), and introduce 2 wt%~4 wt% of conductive additives by total mass. Manually mix in an agate mortar for 0.5 h~1 h.

[0053] Step 2: After the composite powder from Step 1 is mixed evenly, transfer it to a ball mill jar filled with argon gas and ball mill at a speed of 300~350 r / min for 1~3 h to ensure uniform contact of all components. After ball milling, the final cathode powder is obtained and stored in a glove box for later use.

[0054] The active material used in the positive electrode is either lithium cobalt oxide coated with lithium niobate or ternary NCM, with ternary NCM being more preferred. The conductive additive used in the positive electrode can be either vapor-grown carbon fiber (VGCF), conductive carbon black (CB), or carbon nanotubes (CNT), with vapor-grown carbon fiber (VGCF) being more preferred. The ionic conductor used in the positive electrode can be either Li6PS5Cl (LPSC) or Li3InCl4 (LIC), with Li3InCl4 (LIC) being more preferred.

[0055] This invention also provides a method for assembling a silicon-based all-solid-state half-cell and a full-cell, specifically including the following steps: Step 1: Preparation of the silicon-based all-solid-state half-cell. Weigh approximately 80-100 mg of Li6PS5Cl (LPSC) electrolyte, pour it into a polyetheretherketone (PEEK) ring and compact it, holding the pressure at 2t for 1-3 min. Then, place the silicon electrode obtained above into one side of the LPSC electrolyte and hold it at 3.5-4t for 5-10 min to ensure close contact between the silicon electrode and the electrolyte. Then, release the pressure and use a lithium-indium (Li-In) alloy as its counter electrode: take a 100 μm thick, 12 mm diameter indium foil and a 60 μm thick, 12 mm diameter lithium foil, and place them sequentially into the other side of the LPSC electrolyte, in the order of indium and lithium. After completing the above operations, place the entire assembly, including the current collector, silicon electrode, lithium-indium foil, and electrolyte, into a fixture and fix it, holding the pressure at 2t for 1-3 min to achieve lithium-indium alloying. Finally, the battery operates under a pressure of 5-20 MPa.

[0056] Step 2: Test the half-cell assembled in Step 1. The test voltage range is -0.61~0.88 V (0.01~1.5 V vs. Li). + / Li), using constant current discharge / charge test conditions, where the theoretical capacity is set to 3500 mAh / g, three cycles at 0.2 C rate as activation, and then long cycle test at 0.1C-3C rate.

[0057] Step 3: Preparation of the all-solid-state full cell with silicon anode. Weigh approximately 80-100 mg of Li6PS5Cl (LPSC) electrolyte, pour it into a polyetheretherketone (PEEK) ring and compact it, holding it at 2t for 1-3 min. Place the silicon anode and cathode obtained above on either side of the electrolyte at an N / P ratio of 1.2, where the theoretical capacity of NCM is calculated as 200 mAh / g and the theoretical capacity of LCO is calculated as 137 mAh / g. After completing the above operations, place the entire assembly containing the current collector, silicon electrode, composite cathode powder, and electrolyte into a fixture and fix it, holding it at 3.5-4t for 5-10 min. Finally, depressurize the battery to 5-20 MPa for cycling.

[0058] Step 4: Let the assembled full battery from Step 3 stand for 1 hour. Cycle the full battery at a rate of 0.1C for three cycles within a voltage range of 2.5-4.3V. Then, perform charge-discharge cycles at a rate of 1C and pressures of 5MPa, 10MPa, and 20MPa.

[0059] The present invention will be further described in detail below with reference to embodiments: Example 1 (1) Weigh 1 mmol of polytetrahydrofuran and place it in a two-necked flask. Seal one flask and connect the other flask to a vacuum and venting pipe. Place the sealed flask containing the polytetrahydrofuran in an oil bath on a stirrer with a magnetic stirrer. Stir and evacuate for 2 hours at 105 °C to remove moisture from the polytetrahydrofuran. After completion, lower the temperature to 80 °C for later use. Close the vacuum valve and introduce high-purity nitrogen. Repeat the evacuation process three times to ensure appropriate pressure in the two-necked flask. Weigh 2 mmol of isophorone diisocyanate and 3 wt% dibutyltin dilaurate catalyst and dissolve them in 2 ml of ultra-dry dimethylformamide. Using a vacuum-dried syringe, slowly inject the ultra-dry dimethylformamide solution into the dehydrated polytetrahydrofuran precursor raw material over 30 min while continuously stirring. The ideal feed ratio of polytetrahydrofuran to isophorone diisocyanate is -NCO:-OH = 2:1. High-purity nitrogen is introduced during the reaction, and the reaction is continued for 3 hours to finally obtain the binder prepolymer solution.

[0060] (2) Dissolve 1 mmol of biuret in an ultra-dry dimethylformamide solution. Under stirring, slowly inject the dimethylformamide solution containing biuret into the binder prepolymer solution in (1) over 30 min, wherein -OH: chain extender = 1:1. Continue the reaction for 3 h under nitrogen atmosphere protection to obtain pure polymer binder.

[0061] (3) After drying the adhesive prepared in (2) above in a vacuum oven at 70°C for 12 h to obtain an elastic dry polymer, 40 mg of the polymer is dissolved in 2 ml of ultra-dry dimethylformamide solvent, and 20 wt% of its mass of LiFSI salt is introduced. After dissolution, the solution is poured into a polytetrafluoroethylene mold and dried at 70°C for 24 h to obtain the final adhesive PU1 with high ionic conductivity and high mechanical properties. In the above adhesive, polytetrahydrofuran is used as the soft segment, mainly serving as the ion transport functional region, while the other parts serve as the hard segment of the adhesive, improving the mechanical properties of the adhesive.

[0062] (4) Mix silicon active material, conductive carbon black, binder solution prepared in the above steps and ultra-dry N,N-dimethylformamide in a weight ratio of 85:10:5, and ball mill in a planetary ball mill for 1 hour to make them fully mixed and obtain a uniformly dispersed negative electrode slurry; use an automatic coating machine to coat the slurry onto the copper foil current collector with a coating thickness of 150 μm, and vacuum dry at 70°C for 10 hours to obtain the final negative electrode.

[0063] (5) A silicon-based negative electrode was prepared using binder PU1 according to the above method and assembled into an all-solid-state battery. Electrochemical tests were performed according to the aforementioned method, using silicon particles with a diameter of 30 nm. After deducting the mass of the copper foil, the silicon electrode loading was 0.6 mg / cm³. 2.

[0064] The adhesive prepared above was subjected to performance tests, mainly including the following: (1) The dry polymer, polytetrahydrofuran, isophorone diisocyanate, biuret, and dibutyltin dilaurate obtained by drying the binder prepared in Example 1 (2) were subjected to Fourier transform infrared spectroscopy (FTIR) to confirm their molecular structure and prove the successful realization of the polymerization process. Figure 2 As shown, isophorone diisocyanate at 2243 cm⁻¹ -1 The stretching vibration peak is attributed to the N=C=O functional group. When polytetrahydrofuran, isophorone diisocyanate, and biuret are catalyzed by dibutyltin dilaurate, the N=C=O functional group disappears in the resulting polymer. Furthermore, the peak at 1670 cm⁻¹ in biuret... -1 The peak at the C=O group shifts to blue to approximately 1664 cm⁻¹. -1 This indicates the presence of strong hydrogen bonds between the -NH-CO- groups. This proves that the polymer was successfully obtained through polymerization.

[0065] (2) Using the active binder in Example 1, a silicon anode was obtained by coating silicon active material, conductive additive, and PU1 in a mass ratio of 85:10:5. This anode was then assembled with the silicon anode obtained in Comparative Example 1 to form a solid-state battery. A 2C rate long-cycle test was performed at 10 MPa. Figure 3 As shown, the solid-state battery obtained using PU1 achieved a 2930 mAh g⁻¹ at 2C. -1 The first reversible capacity. After 700 cycles, its remaining capacity is still 2246 mAh g. -1 The retention rate reached 77%, and the average coulombic efficiency was 99.85%. In contrast, the solid-state battery in Comparative Example 1 only demonstrated 1199 mAh g⁻¹ in the first cycle. -1 The initial reversible capacity, after 700 cycles, rapidly declined to 846 mAh g. -1 This demonstrates that the significantly improved mechanical properties and ion conductivity of the binder in this invention are crucial for enhancing the stability of silicon anodes during long-term cycling.

[0066] (3) Using the active binder in Example 1, a silicon anode was obtained by coating silicon active material, conductive additives, and PU1 in a mass ratio of 85:10:5, and then a solid-state battery was assembled. A 1C rate long-cycle test was performed at 5 MPa. Figure 4 As shown, using PU1, a current rating of 1C can achieve 2980 mAh g⁻¹. -1 The reversible capacity and stability over 500 cycles demonstrate that the binder in this invention can operate stably under ultra-low pressure.

[0067] (4) Ionic conductivity tests were performed using the adhesive PU1 from Example 1 and the adhesive used in Comparative Example 1. The AC impedance curves obtained via EIS are shown below. Figure 5 As shown. By fitting the EIS curve, the ionic conductivity of PU1 was found to be 3.7 × 10⁻⁶. -5 The S / cm was significantly higher than that of Comparative Example 1 (ionic conductivity 1.8 × 10⁻⁶). -7 The S / cm indicates that the binder synthesized in this patent is a highly ionicly conductive polymer.

[0068] (5) Nanoindentation tests were performed using the adhesive PU1 from Example 1 and the adhesive used in Comparative Example 1. For example... Figure 6 The load-depth displacement curves of Example 1 and Comparative Example 1, obtained through nanoindentation, are shown. Under the same loading conditions, Example 1 exhibits a maximum indentation depth of 4321 nm and an elastic recovery rate of 58%, both significantly better than Comparative Example 1 (711 nm and 39.8%). The greater indentation depth reflects superior deformability, while the high recovery rate indicates that the binder prepared in this patent has efficient elastic rebound capability.

[0069] (6) Cryo-electron microscopy analysis was performed using the binder PU1 from Example 1 and the binder used in Comparative Example 1. This was used to determine the microscopic distribution of the binder on the surface of the silicon particles. Figure 7 As shown, the structure of the interface layer can be clearly observed in HRTEM high-resolution mode: the outer layer is an amorphous PU1 region, and the inner layer is composed of Li2O, Li2CO3, Li3N, and LiF nanocrystals, exhibiting a mosaic-like distribution. These inorganic phases were verified by TEM local fast Fourier transform, and their corrected interplanar spacings of 0.266 nm, 0.281 nm, 0.308 nm, and 0.201 nm correspond to Li2O (111), Li2CO3 (002), Li3N (100), and LiF (200), respectively. In contrast, the binder in Comparative Example 1 exhibits an inhomogeneous amorphous layer with a thickness of approximately 2–36.8 nm around the silicon core, which not only increases the ion transport impedance inside the electrode but also exacerbates the non-uniform electrochemical reactions within the electrode. This demonstrates the uniformity of the organic + inorganic bidirectional protective layer formed after the binder decomposes in this invention.

[0070] (7) The silicon anodes obtained in Example 1 and Comparative Example 1 were subjected to electrochemical cycling, and the electrode / electrolyte interface before and after cycling was analyzed by cross-sectional scanning electron microscopy. Figure 8As shown, before cycling, no obvious cracks or pores appeared between the electrodes of Example 1 and Comparative Example 1 and the LPSC layer. However, after 50 cycles, the surface morphology of the Comparative Example 1 electrode changed significantly compared to before cycling, with a large number of cracks or pores with a size close to 1 μm appearing, accompanied by through-cracks. In stark contrast, the silicon particles in the Example 1 electrode remained in close contact after cycling, and no obvious micropores or cracks were observed. The thickness of the Example 1 electrode increased by only 0.4 μm from the initial 10.4 μm, while that of the Comparative Example 1 electrode increased from 10.0 μm to 13.6 μm. This proves that the binder in this invention effectively maintains the reversible deformation of the silicon particle interface, thereby ensuring the overall structural stability of the silicon anode during long cycling.

[0071] Example 2 (1) Weigh 2 mmol of polytetrahydrofuran and place it in a two-necked flask. Seal one flask and connect the other flask to a vacuum and venting pipe. Place the sealed flask containing polytetrahydrofuran in an oil bath on a stirrer with a magnetic stirrer. Stir and evacuate for 2 hours at 105 °C to remove moisture from the polytetrahydrofuran. After completion, lower the temperature to 80 °C for later use. Close the vacuum valve and introduce high-purity nitrogen. Repeat the evacuation process three times to ensure appropriate pressure in the two-necked flask. Weigh 3 mmol of isophorone diisocyanate and 3 wt% dibutyltin dilaurate catalyst and dissolve them in 2 ml of ultra-dry dimethylformamide. Using a vacuum-dried syringe, slowly inject the ultra-dry dimethylformamide solution into the dehydrated polytetrahydrofuran precursor raw material over 30 min while continuously stirring. Polytetrahydrofuran is in excess, i.e., -NCO:-OH = 1.5:1. High-purity nitrogen gas was introduced during the reaction and the reaction was continued for 3 hours to finally obtain the binder prepolymer solution.

[0072] (2) Dissolve 1 mmol of biuret in an ultra-dry dimethylformamide solution. Under stirring, slowly inject the dimethylformamide solution containing biuret into the binder prepolymer solution in (1) over 30 min, wherein -OH: chain extender = 1:1. Continue the reaction for 3 h under nitrogen atmosphere protection to obtain pure polymer binder.

[0073] (3) After drying the adhesive prepared in (2) above in a vacuum oven at 70°C for 12 h to obtain an elastic dry polymer, 40 mg of the polymer is dissolved in 2 ml of ultra-dry dimethylformamide solvent, and 20 wt% of its mass of LiFSI salt is introduced. After dissolution, the solution is poured into a polytetrafluoroethylene mold and dried at 70°C for 24 h to obtain the final adhesive PU2 with high ionic conductivity and high mechanical properties. In the above adhesive, polytetrahydrofuran is used as the soft segment, mainly serving as the ion transport functional region, while the other parts serve as the hard segment of the adhesive, improving the mechanical properties of the adhesive.

[0074] (4) Mix silicon active material, conductive carbon black, binder solution prepared in the above steps and ultra-dry N,N-dimethylformamide in a weight ratio of 85:10:5, and ball mill in a planetary ball mill for 1 hour to make them fully mixed and obtain a uniformly dispersed negative electrode slurry; use an automatic coating agent to coat the slurry onto the copper foil current collector with a coating thickness of 150 μm, and vacuum dry at 70°C for 10 hours to obtain the final negative electrode.

[0075] (5) A silicon-based negative electrode was prepared using binder PU2 according to the above method and assembled into an all-solid-state battery. Electrochemical tests were performed according to the aforementioned method, using silicon particles with a diameter of 30 nm. After deducting the mass of the copper foil, the silicon electrode loading was 0.6 mg / cm³. 2 .

[0076] Example 3 (1) Weigh 2 mmol of polytetrahydrofuran and place it in a two-necked flask. Seal one flask and connect the other flask to a vacuum and venting pipe. Place the sealed flask containing polytetrahydrofuran in an oil bath on a stirrer with a magnetic stirrer. Stir and evacuate for 2 hours at 105 °C to remove moisture from the polytetrahydrofuran. After completion, lower the temperature to 80 °C for later use. Close the vacuum valve and introduce high-purity nitrogen. Repeat the evacuation process three times to ensure appropriate pressure in the two-necked flask. Weigh 5 mmol of isophorone diisocyanate and 3 wt% dibutyltin dilaurate catalyst and dissolve them in 2 ml of ultra-dry dimethylformamide. Use a vacuum-dried syringe to slowly inject the ultra-dry dimethylformamide solution into the dehydrated polytetrahydrofuran precursor raw material over 30 min, while continuously stirring. The isophorone diisocyanate is in excess, i.e., -NCO:-OH = 2.5:1. High-purity nitrogen gas was introduced during the reaction and the reaction was continued for 3 hours to finally obtain the binder prepolymer solution.

[0077] (2) Dissolve 1 mmol of biuret in an ultra-dry dimethylformamide solution. Under stirring, slowly inject the dimethylformamide solution containing biuret into the binder prepolymer solution in (1) over 30 min, wherein -OH: chain extender = 1:1. Continue the reaction for 3 h under nitrogen atmosphere protection to obtain pure polymer binder.

[0078] (3) After drying the adhesive prepared in (2) above in a vacuum oven at 70°C for 12 h to obtain an elastic dry polymer, 40 mg of the polymer is dissolved in 2 ml of ultra-dry dimethylformamide solvent, and 20 wt% of its mass of LiFSI salt is introduced. After dissolution, the solution is poured into a polytetrafluoroethylene mold and dried at 70°C for 24 h to obtain the final adhesive PU3 with high ionic conductivity and high mechanical properties. In the above adhesive, polytetrahydrofuran is used as the soft segment, mainly serving as the ion transport functional region, while the other parts serve as the hard segment of the adhesive, improving the mechanical properties of the adhesive.

[0079] (4) Mix silicon active material, conductive carbon black, binder solution prepared in the above steps and ultra-dry N,N-dimethylformamide in a weight ratio of 85:10:5, and ball mill in a planetary ball mill for 1 hour to make them fully mixed and obtain a uniformly dispersed negative electrode slurry; use an automatic coating agent to coat the slurry onto the copper foil current collector with a coating thickness of 150 μm, and vacuum dry at 70°C for 10 hours to obtain the final negative electrode.

[0080] (5) Using binder PU2, a silicon-based negative electrode was prepared according to the above method and assembled into an all-solid-state battery. Electrochemical tests were performed according to the aforementioned method, using silicon particles with a diameter of 30 nm. After deducting the mass of the copper foil, the silicon electrode loading was 0.6 mg / cm³. 2 .

[0081] Example 4 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, but the feeding ratios of polytetrahydrofuran, isophorone diisocyanate, and chain extender are different: polytetrahydrofuran is 1 mmol, isophorone diisocyanate is 2 mmol, and biuret is 0.5 mmol. The feeding ratio of polytetrahydrofuran to isophorone diisocyanate is ideal, i.e., -NCO:-OH = 2:1, but the proportion of chain extender is reduced, i.e., terminal hydroxyl group: chain extender = 1:0.5, to obtain the final adhesive PU4 with high ionic conductivity and high mechanical properties.

[0082] Example 5 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 2, but the feeding ratios of polytetrahydrofuran, isophorone diisocyanate, and chain extender are different. The polytetrahydrofuran is 2 mmol, the isophorone diisocyanate is 3 mmol, and the biuret is 1 mmol. Polytetrahydrofuran is in excess, i.e., -NCO:-OH = 1.5:1, but the chain extender ratio is reduced, i.e., -OH:chain extender = 1:0.5, to obtain the final adhesive PU5 with high ionic conductivity and high mechanical properties.

[0083] Example 6 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 3, but the feeding ratios of polytetrahydrofuran, isophorone diisocyanate, and chain extender are different: 2 mmol of polytetrahydrofuran, 5 mmol of isophorone diisocyanate, and 1 mmol of biuret. The isophorone diisocyanate is added in excess, i.e., -NCO:-OH = 2.5:1, but the chain extender ratio is reduced, i.e., terminal hydroxyl group: chain extender = 1:0.5, resulting in the final adhesive PU6 with high ionic conductivity and high mechanical properties.

[0084] Example 7 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, but the feeding ratios of polytetrahydrofuran, isophorone diisocyanate, and chain extender are different: polytetrahydrofuran is 1 mmol, isophorone diisocyanate is 2 mmol, and biuret is 1.5 mmol. The feeding ratio of polytetrahydrofuran to isophorone diisocyanate is ideal, i.e., -NCO:-OH = 2:1, but by increasing the proportion of chain extender, i.e., -OH:chain extender = 1:1.5, the final adhesive PU7 with high ionic conductivity and high mechanical properties is obtained.

[0085] Example 8 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 2, but the feeding ratios of polytetrahydrofuran, isophorone diisocyanate, and chain extender are different. The polytetrahydrofuran is 2 mmol, the isophorone diisocyanate is 3 mmol, and the biuret is 3 mmol. Polytetrahydrofuran is added in excess, i.e., -NCO:-OH = 1.5:1, but the chain extender ratio is increased, i.e., -OH:chain extender = 1:1.5, resulting in the final adhesive PU8 with high ionic conductivity and high mechanical properties.

[0086] Example 9 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 3, but the feeding ratios of polytetrahydrofuran, isophorone diisocyanate, and chain extender are different. The polytetrahydrofuran is 2 mmol, the isophorone diisocyanate is 5 mmol, and the biuret is 3 mmol. The isophorone diisocyanate is in excess, i.e., -NCO:-OH = 2.5:1, but the chain extender ratio is increased, i.e., -OH:chain extender = 1:1.5, to obtain the final adhesive PU9 with high ionic conductivity and high mechanical properties.

[0087] Example 10 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, except that the ether-containing polyol is replaced with polyethylene glycol, i.e., 1 mmol of polyethylene glycol, 2 mmol of isophorone diisocyanate, and 1 mmol of biuret. The ratio of polyethylene glycol to isophorone diisocyanate is ideal, i.e., -NCO:-OH = 2:1, -OH:chain extender = 1:1, resulting in the final adhesive PU10 with high ionic conductivity and high mechanical properties.

[0088] Example 11 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, except that the ether-containing polyol is replaced with polyethylene oxide, i.e., 1 mmol of polyethylene oxide, 2 mmol of isophorone diisocyanate, and 1 mmol of biuret. The ratio of polyethylene oxide to isophorone diisocyanate is ideal, i.e., -NCO:-OH = 2:1, -OH:chain extender = 1:1, resulting in the final adhesive PU11 with high ionic conductivity and high mechanical properties.

[0089] Example 12 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, except that the diisocyanate hard segment is replaced with hexamethylene diisocyanate, i.e., 1 mmol of polytetrahydrofuran, 2 mmol of hexamethylene diisocyanate, and 1 mmol of biuret. The ratio of polytetrahydrofuran to hexamethylene diisocyanate is ideal, i.e., -NCO:-OH = 2:1, -OH:chain extender = 1:1, resulting in the final adhesive PU12 with high ionic conductivity and high mechanical properties.

[0090] Example 13 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, except that the diisocyanate hard segment is replaced with dicyclohexylmethane diisocyanate, i.e., 1 mmol of polytetrahydrofuran, 2 mmol of dicyclohexylmethane diisocyanate, and 1 mmol of biuret. The ratio of polytetrahydrofuran to dicyclohexylmethane diisocyanate is ideal, i.e., -NCO:-OH = 2:1, -OH:chain extender = 1:1, resulting in the final adhesive PU13 with high ionic conductivity and high mechanical properties.

[0091] Example 14 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, except that biuret is replaced with dihydroxyethylurea, i.e., 1 mmol of polytetrahydrofuran, 2 mmol of isophorone diisocyanate, and 1 mmol of dihydroxyethylurea. The ratio of polytetrahydrofuran to isophorone diisocyanate is ideal, i.e., -NCO:-OH = 2:1, -OH:chain extender = 1:1, resulting in the final adhesive PU14 with high ionic conductivity and high mechanical properties.

[0092] Example 15 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, except that biuret is replaced with dihydroxypropylurea, i.e., 1 mmol of polytetrahydrofuran, 2 mmol of isophorone diisocyanate, and 1 mmol of dihydroxypropylurea. The ratio of polytetrahydrofuran to isophorone diisocyanate is ideal, i.e., -NCO:-OH = 2:1, -OH:chain extender = 1:1, resulting in the final adhesive PU15 with high ionic conductivity and high mechanical properties.

[0093] Example 16 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, but the mass ratio of the introduced LiFSI salt is 30 wt%. The designed proportions in the synthesized adhesive remain unchanged, and it is used as adhesive PU16.

[0094] Example 17 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, but the mass ratio of the introduced LiFSI salt is 40 wt%. The designed proportion in the synthesized adhesive remains unchanged, and it is used as adhesive PU17.

[0095] Example 18 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, but the mass ratio of the introduced LiFSI salt is 50 wt%. The designed proportions in the synthesized adhesive remain unchanged, and it is used as adhesive PU18.

[0096] Example 19 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties adhesive are the same as in Example 1, but the mass ratio of the introduced LiFSI salt is 60 wt%. The designed proportions in the synthesized adhesive remain unchanged, and it is used as adhesive PU19.

[0097] Example 20 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties binder are the same as in Example 1, but the lithium salt introduced is replaced with LiTFSI at a mass ratio of 20 wt%. The designed proportions in the synthesized binder remain unchanged, serving as binder PU20.

[0098] Example 21 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties binder are the same as in Example 1, but the lithium salt introduced is replaced with LiPF6 at a mass ratio of 20 wt%. The designed proportions in the synthesized binder remain unchanged, serving as binder PU21.

[0099] Example 22 The preparation method and reaction conditions of the high ionic conductivity and high mechanical properties binder are the same as in Example 1, but the lithium salt introduced is replaced with LiBF4 at a mass ratio of 20 wt%. The designed proportions in the synthesized binder remain unchanged, serving as binder PU22.

[0100] Example 23 The preparation method, reaction conditions and ratio of the binder with high ionic conductivity and high mechanical properties are the same as in Example 1. The silicon-based negative electrode is prepared by the binder PU1 according to the above method and assembled into an all-solid-state battery. Electrochemical tests are performed according to the aforementioned method, using silicon particles with a diameter of 100 nm.

[0101] Example 24 The preparation method, reaction conditions and ratio of the binder with high ionic conductivity and high mechanical properties are the same as in Example 1. The silicon-based negative electrode is prepared by the binder PU1 according to the above method and assembled into an all-solid-state battery. Electrochemical tests are performed according to the aforementioned method, using silicon particles with a diameter of 1 μm.

[0102] Example 25 The preparation method, reaction conditions and ratio of the binder with high ionic conductivity and high mechanical properties are the same as in Example 1. The silicon-based negative electrode is prepared and assembled into an all-solid-state battery using binder PU1 according to the above method. The weight ratio of silicon active material, conductive carbon black and binder solution obtained in the above steps is adjusted to 70:20:10.

[0103] Example 26 The preparation method, reaction conditions and ratio of the binder with high ionic conductivity and high mechanical properties are the same as in Example 1. The silicon-based negative electrode is prepared and assembled into an all-solid-state battery using binder PU1 according to the above method. The weight ratio of silicon active material, conductive carbon black and binder solution obtained in the above steps is adjusted to 80:10:10.

[0104] Example 27 The preparation method, reaction conditions and ratio of the binder with high ionic conductivity and high mechanical properties are the same as in Example 1. The silicon-based negative electrode is prepared and assembled into an all-solid-state battery using binder PU1 according to the above method. The weight ratio of silicon active material, conductive carbon black and binder solution obtained in the above steps is adjusted to 90:5:5.

[0105] Comparative Example 1 (1) In a glove box, silicon active material, conductive additive and sulfide electrolyte LPSC with a weight ratio of 70:10:15 were dissolved in xylene solution, and 5% polyethylene oxide (PEO) was added as a binder. After sealing with sealing glue, the mixture was ball-milled in a planetary ball mill for 1 hour to make it fully mixed and obtain a uniformly dispersed negative electrode slurry. The slurry was coated onto the copper foil current collector with an automatic coating agent and the coating thickness was 150 μm. After vacuum drying at 70°C for 10 hours, the final negative electrode was obtained.

[0106] (2) The dried silicon anode sheet from (1) was cut into 12mm diameter sheets using a manual cutting machine and stored in an argon-filled glove box (O2 < 0.1ppm, H2O < 0.1ppm). A silicon-based anode was prepared using polyethylene oxide (PEO) according to the above method and assembled into an all-solid-state battery. Electrochemical tests were performed as described above, using silicon particles with a diameter of 30nm. After deducting the mass of the copper foil, the silicon electrode loading was 0.6 mg / cm³. 2 .

[0107] Comparative Example 2 (1) In a glove box, silicon active material, conductive additive and sulfide electrolyte LPSC in a weight ratio of 70:10:15 were dissolved in xylene solution, and 5% nitrile rubber (NBR) was added as a binder. After sealing with sealing glue, the mixture was ball-milled in a planetary ball mill for 1 hour to make it fully mixed and obtain a uniformly dispersed negative electrode slurry. The slurry was coated onto the copper foil current collector with an automatic coating agent and the coating thickness was 150 μm. After vacuum drying at 70 °C for 10 hours, the final negative electrode was obtained.

[0108] (2) The dried silicon anode sheet from (1) was cut into 12mm diameter sheets using a manual cutting machine and stored in an argon-filled glove box (O2 < 0.1ppm, H2O < 0.1ppm). A silicon-based anode was prepared using nitrile rubber (NBR) according to the above method and assembled into an all-solid-state battery. Electrochemical tests were performed as described above, using a silicon particle size of 30nm. After deducting the mass of the copper foil, the silicon electrode loading was 0.6 mg / cm³. 2 .

[0109] Comparative Example 3 (1) In a glove box, silicon active material, conductive additive and sulfide electrolyte LPSC in a weight ratio of 70:10:15 were dissolved in xylene solution, and 5% styrene-ethylene-butene-styrene block copolymer (SEBS) was added as a binder. After sealing with sealing glue, the mixture was ball-milled in a planetary ball mill for 1 hour to make it fully mixed and obtain a uniformly dispersed negative electrode slurry. The slurry was coated onto the copper foil current collector with an automatic coating agent and the coating thickness was 150 μm. After vacuum drying at 70 °C for 10 hours, the final negative electrode was obtained.

[0110] (2) The dried silicon anode sheet from (1) was cut into 12mm diameter sheets using a manual cutting machine and stored in an argon-filled glove box (O2 < 0.1ppm, H2O < 0.1ppm). A silicon-based anode was prepared using styrene-ethylene-butene-styrene block copolymer (SEBS) according to the above method and assembled into an all-solid-state battery. Electrochemical tests were performed according to the aforementioned method, using silicon particles with a diameter of 30nm. After deducting the mass of the copper foil, the silicon electrode loading was 0.6 mg / cm³. 2 .

[0111] Comparative Example 4 (1) In a glove box, silicon active material, conductive additive and sulfide electrolyte LPSC in a weight ratio of 70:10:15 were dissolved in xylene solution, and 5% polymethyl methacrylate (PMMA) was added as a binder. After sealing with sealing glue, the mixture was ball-milled in a planetary ball mill for 1 hour to make it fully mixed and obtain a uniformly dispersed negative electrode slurry. The slurry was coated onto the copper foil current collector with an automatic coating agent and the coating thickness was 150 μm. After vacuum drying at 70 °C for 10 hours, the final negative electrode was obtained.

[0112] (2) The dried silicon anode sheet from (1) was cut into 12mm diameter sheets using a manual cutting machine and stored in an argon-filled glove box (O2 < 0.1ppm, H2O < 0.1ppm). A silicon-based anode was prepared using polymethyl methacrylate (PMMA) according to the above method and assembled into an all-solid-state battery. Electrochemical tests were performed as described above, using silicon particles with a diameter of 30nm. After deducting the mass of the copper foil, the silicon electrode loading was 0.6 mg / cm³. 2 .

[0113] Comparative Example 5 (1) In a glove box, silicon active material, conductive additive and sulfide electrolyte LPSC in a weight ratio of 70:10:15 were dissolved in xylene solution, and 5% poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) was added as a binder. After sealing with sealing glue, the mixture was ball-milled in a planetary ball mill for 1 hour to make it fully mixed and obtain a uniformly dispersed negative electrode slurry. The slurry was coated onto the copper foil current collector with an automatic coating agent and the coating thickness was 150 μm. After vacuum drying at 70 °C for 10 hours, the final negative electrode was obtained.

[0114] (2) The dried silicon anode sheet from (1) was cut into 12mm diameter sheets using a manual cutting machine and stored in an argon-filled glove box (O2 < 0.1ppm, H2O < 0.1ppm). A silicon-based anode was prepared using poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) according to the above method and assembled into an all-solid-state battery. Electrochemical tests were performed according to the aforementioned method, using a silicon particle size of 30nm. After deducting the mass of the copper foil, the silicon electrode loading was 0.6 mg / cm³. 2 .

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A silicon anode for all-solid-state batteries, characterized in that, The invention includes a current collector and a silicon anode paste attached to the current collector. The silicon anode paste comprises a silicon active material, a conductive additive, and a binder. The binder comprises a viscous polymer and a lithium salt. The preparation process of the viscous polymer is as follows: first, the terminal hydroxyl groups of the polyether polyol react with the isocyanate groups of the diisocyanate monomer to generate a prepolymer with NCO terminal groups; then, at least two active hydrogen functional groups at both ends of the chain extender molecule react with the residual NCO groups in the prepolymer to form urea bonds or urethane bonds, thereby achieving chain extension of the molecular chain.

2. The silicon anode for all-solid-state batteries according to claim 1, characterized in that, The mass ratio of the silicon active material, conductive additive and binder is (70~90):(5~20):(5~10).

3. The silicon anode for all-solid-state batteries according to claim 1, characterized in that, The conductive additive is any one of vapor-grown carbon fiber, conductive carbon black, or carbon nanotubes, and the silicon active material is silicon particles.

4. The silicon anode for all-solid-state batteries according to any one of claims 1-3, characterized in that, The molar ratio of the diisocyanate monomer, polyether polyol and chain extender is (2-5):(1-2):(0.5-3).

5. A silicon anode for an all-solid-state battery according to any one of claims 1-3, characterized in that, Based on the total mass of the adhesive, the mass fraction of lithium salt in the adhesive is 20wt%-60wt%, and the remainder is a viscous polymer.

6. A silicon anode for an all-solid-state battery according to any one of claims 1-3, characterized in that, The lithium salt is at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, and lithium tetrafluoroborate.

7. A silicon anode for an all-solid-state battery according to any one of claims 1-3, characterized in that, The polyether polyol is any one of polytetrahydrofuran, polyethylene glycol, and polyethylene oxide.

8. A silicon anode for an all-solid-state battery according to any one of claims 1-3, characterized in that, The diisocyanate monomer is any one of isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate.

9. A silicon anode for an all-solid-state battery according to any one of claims 1-3, characterized in that, The chain extender is any one of dihydroxyethyl urea or its derivatives, dihydroxypropyl urea or its derivatives, or biuret or its derivatives.

10. An all-solid-state battery, characterized in that, It includes a positive electrode, a silicon negative electrode for an all-solid-state battery as described in any one of claims 1-9, and a sulfide solid electrolyte disposed between the positive electrode and the silicon negative electrode.

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