All-solid-state battery equipped with stress relaxation local layer at electrode interface and manufacturing method thereof

Abstract

This application relates to the field of solid-state battery technology, and discloses an all-solid-state battery with a stress-relieving localization layer at the electrode interface and its manufacturing method. The localization layer includes a stress-relieving localization layer with a thickness of 1μm-5μm, which is composed of 5wt%-20wt% of a conductive elastomer containing polar side-chain functional groups and 80wt%-95wt% of nano-sized sulfide solid electrolyte particles. During charge-discharge cycles, this localization layer disperses the localized mechanical stress generated by the lattice expansion of the electrode through the deformation of the flexible polymer segments, inhibiting microcrack propagation and interface delamination; and spontaneously rebuilds physical and electrical contacts by recombining dynamically reversible non-covalent chemical bonds at the points where the polar side-chain functional groups detach from the interface. This invention achieves spatial decoupling between interface stress buffering and low bulk impedance, improving the battery's long cycle life and high-rate output performance.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, specifically to an all-solid-state battery equipped with a stress-relieving localization layer at the electrode interface and its manufacturing method. Background Technology

[0002] All-solid-state batteries use solid electrolytes instead of traditional liquid electrolytes, showing high application potential in terms of safety and energy density. Among them, sulfide solid electrolytes have become a key research direction due to their high room-temperature ionic conductivity and good room-temperature cold-pressing properties. However, the solid-solid contact between the components inside an all-solid-state battery and the physical instability of the electrode-solid electrolyte interface are key obstacles to long cycle life.

[0003] During battery charge-discharge cycles, the positive electrode active material undergoes periodic volume expansion and contraction due to the insertion and extraction of lithium ions. This volume change generates significant localized mechanical stress at the interface between the positive electrode and the solid electrolyte layer. Because the purely inorganic sulfide solid electrolyte exhibits significant brittleness, it cannot absorb and dissipate the strain energy generated by these volume changes through elastic deformation, leading to a high concentration of stress at the microscopic interface. Under long-term cyclic alternating stress, microcracks form at the interface and propagate, eventually causing irreversible physical delamination between the positive electrode particles and the solid electrolyte. This interface delamination directly severs the microscopic ion and electron conduction channels, causing a sharp increase in the interfacial contact resistance within the battery, macroscopically manifested as a rapid decrease in the battery's usable capacity.

[0004] To address the aforementioned interfacial stress concentration and delamination phenomena, the conventional approach is to uniformly add elastic polymer materials to the inorganic powder during the solid-state electrolyte preparation process, hoping to utilize the polymer's flexibility to buffer mechanical stress. While this method of uniformly mixing the polymer with the inorganic particles reduces the overall brittleness of the material to some extent, it introduces a serious bulk impedance problem. Since the ion conductivity of most polymers at room temperature is far lower than that of sulfide inorganic materials, the polymer network present in large quantities within the bulk phase inevitably encapsulates the inorganic particles, physically blocking direct contact between the inorganic particles and disrupting the originally continuous high-speed ion conduction path. This homogeneous mixed structure significantly increases the bulk ohmic impedance of the solid-state electrolyte layer, leading to severe polarization and significant degradation of rate performance in all-solid-state batteries when facing high load current output demands. Existing techniques struggle to achieve an effective balance between buffering interfacial mechanical stress and maintaining low bulk impedance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an all-solid-state battery equipped with a stress-relieving localized layer at the electrode interface and its manufacturing method. This solves the problem that all-solid-state batteries are prone to interface stress concentration and physical delamination due to electrode volume changes during charge-discharge cycles, while adding polymers globally to the solid electrolyte to buffer stress can block the inorganic ion conduction network and increase the battery's bulk phase impedance.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides an all-solid-state battery with a stress-relieving localization layer at the electrode interface, employing the following technical solution: an all-solid-state battery with a stress-relieving localization layer at the electrode interface, wherein the stress-relieving localization layer is provided at the electrode interface of the all-solid-state battery, and the stress-relieving localization layer is made of components comprising the following mass fractions: 5wt%-20wt% of a conductive elastomer containing polar side chain functional groups; 80wt%-95wt% of nano-sized sulfide solid electrolyte particles; and the thickness of the stress-relieving localization layer is controlled to be 1μm-5μm.

[0008] By employing the above technical solution, and due to the use of a stress-relieving localized layer with a specific thickness and composition ratio, the present invention achieves a unity of interface stability and low bulk impedance in both physical structure and chemical mechanism, specifically obtaining the following effects: First, spatial functional decoupling is achieved. The conductive elastomer, which performs stress buffering function, is strictly confined within a physical space of 1μm-5μm from the interface, blocking the disordered diffusion of the polymer into the bulk solid electrolyte layer. The bulk solid electrolyte layer maintains a pure inorganic state, ensuring the low impedance ionic conductivity of the pure inorganic lattice network. After crossing the micron-thick interface localized layer, lithium ions rapidly enter the bulk layer for high-speed transport, meeting the output requirements of high-current-rate charging and discharging in all-solid-state batteries. Second, mechanical stress dispersion is achieved. 5wt%-20wt% of conductive elastomer constructs a continuous high-strength bonding network within the localized layer. The flexible polymer backbone of the elastomer possesses the physical and mechanical properties of absorbing and dissipating mechanical strain energy. During battery charging and discharging, the local tensile and shear stresses generated by the expansion of the positive electrode lattice induce the stretching and deformation of the elastomer chain segments. This deformation process absorbs external mechanical energy, disperses stress concentration areas, and inhibits the propagation of microcracks into the bulk inorganic layer. Third, a dynamic interface self-repair mechanism is achieved. Its chemical fracture and recombination process includes the following steps: Step 1, stress peeling stage: When the local stress extreme value exceeds the physical bonding limit of the interface, the positive electrode particles or solid electrolyte particles undergo microscopic physical separation from the conductive elastomer, and the original non-covalent chemical bonds at the interface break. Step 2, molecular creep stage: After peeling, the conductive elastomer polymer chain segments undergo spontaneous creep driven by room temperature thermal motion, and the polymer network extends into the peeling gap, refilling the microscale interfacial pores. Step 3, Chemical Bond Reorganization Stage: The polar side chain functional groups suspended by the elastomer side chain re-engage with the exposed inorganic material surface. The spontaneous reaction process is as follows: Polymer polar side chain functional groups + inorganic surface polar active sites ⇌ Non-covalent chemical bond network. Due to the dynamic reversibility of the above reaction, hydrogen bonds or coordination bonds are re-established at the peeling interface. The microscopic electrical and ion contact channels are spontaneously rebuilt, so that the interfacial contact resistance spontaneously recovers from the high resistance state at the moment of peeling to the initial low resistance state, maintaining the stable operation of the battery during long-term cycling.

[0009] Preferably, the polar side chain functional group is one of carboxyl, amide, or polyurethane groups; the conductive elastomer is one of a carboxyl-containing conductive elastomer, an amide-containing conductive elastomer, or a polyurethane-containing conductive elastomer. By adopting the above technical solution, the functional group possesses high polarity, enabling it to form stable non-covalent chemical bonds with the surface of the positive electrode active material and the sulfide solid electrolyte surface. The strong chemical bonding enhances the initial mechanical adhesion strength of the interface and provides a chemical reaction driving force for the dynamic self-healing process after interface peeling.

[0010] Preferably, when the conductive elastomer is a carboxyl-containing conductive elastomer, the carboxyl-containing conductive elastomer is obtained by oxidative copolymerization and drying of a mixture of 3,4-ethylenedioxythiophene monomer and 3,4-ethylenedioxythiophene-formic acid monomer in an aqueous solution of polystyrene sulfonic acid; wherein the molar ratio of 3,4-ethylenedioxythiophene monomer to 3,4-ethylenedioxythiophene-formic acid monomer is (3-5):1, and the mass ratio of polystyrene sulfonic acid solids to total monomers is (2-3):1. By adopting the above technical solution and setting a specific monomer ratio, the electronic conductivity of the conjugated structure of the conductive polymer backbone is maintained, while ensuring that the side chains provide sufficient carboxyl group density for interfacial chemical bonding. Polystyrene sulfonic acid acts as a dispersant to ensure the stability of the polymer emulsion and as an anionic dopant to further improve the electronic conductivity inside the material, ensuring the continuity of the electron transport channels within the local layer.

[0011] Preferably, when the conductive elastomer is a polyurethane-based conductive elastomer, the polyurethane-based conductive elastomer is composed of a polyurethane elastomer generated by reacting an isocyanate-terminated polyurethane prepolymer with a chain extender, and a carboxyl-based conductive elastomer mixed at a mass ratio of (0.8-1.2):1; wherein the molar ratio of the prepolymer, 2,2-dimethylolpropionic acid (as a chain extender), and 1,4-butanediol is 1:(0.4-0.6):(0.4-0.6). By adopting the above technical solution, the polyurethane elastomer provides large deformation capacity and high elongation at break. When polyurethane and carboxyl-based conductive elastomer are mixed, they form an interpenetrating polymer network structure at the microscopic level. This structure combines excellent electrochemical conductivity with macroscopic physical elasticity, and significantly improves the upper limit of the interface's mechanical resistance to lattice volume expansion through a multiple hydrogen bond network.

[0012] Preferably, the average particle size (D50) of the nano-sized sulfide solid electrolyte particles is 100 nm-200 nm; the thickness of the bulk solid electrolyte layer is 50 μm-100 μm, and the bulk solid electrolyte layer is formed from raw materials including sulfide solid electrolyte powder with an average particle size (D50) of 2.0 μm and polytetrafluoroethylene powder. By adopting the above technical solution, the local layer uses nano-sized solid electrolyte particles, increasing the contact surface area between the solid particles and the conductive elastomer, and constructing a dense permeation and conduction network. The bulk electrolyte layer is formed independently from micron-sized powder, reducing the number of grain boundaries between inorganic particles inside the bulk phase and reducing the grain boundary resistance during long-distance ion transport.

[0013] Secondly, the present invention provides a method for manufacturing an all-solid-state battery with a stress-relieving localized layer at the electrode interface, employing the following technical solution: A method for manufacturing an all-solid-state battery with a stress-relieving localized layer at the electrode interface includes the following steps: forming an independent solid electrolyte membrane from bulk solid electrolyte powder as a bulk electrolyte layer; pulverizing sulfide solid electrolyte particles, dispersing the pulverized nanoparticles in a conductive elastomer dispersion containing polar side chain functional groups, adjusting the slurry viscosity with a solvent to obtain an interface stress-relieving slurry; coating and drying the interface stress-relieving slurry to form an interface localized layer with a thickness of 1 μm to 5 μm; stacking a positive electrode layer, a bulk electrolyte layer, and a lithium metal negative electrode layer, such that the interface localized layer directly contacts the active material layer of the positive electrode layer and the bulk electrolyte layer; placing the stacked assembly in a press for multi-stage hot-pressing curing, so that the polar side chain functional groups in the interface localized layer establish chemical bonds with adjacent interfaces, and encapsulating after cooling to obtain an all-solid-state battery with a stress-relieving localized layer at the electrode interface.

[0014] By employing the above technical solutions, a liquid-phase dispersion process is used to prepare the slurry, promoting uniform mixing of conductive elastomer polymer chains and nano-sized sulfide particles at the molecular scale in a liquid environment. After drying, a uniform stress buffer network without macroscopic physical defects is formed. The independent molding process of the bulk electrolyte layer avoids polymer wetting into the bulk phase. The multi-stage hot-pressing curing process utilizes the synergistic effect of temperature and pressure to promote the deformation and adhesion of the localized layer on the surface of the solid electrolyte and electrode, simultaneously establishing tight physical microscopic contact and non-covalent chemical bonding.

[0015] Preferably, in the step of obtaining the interfacial stress-relieving slurry, anhydrous acetonitrile is used as a solvent to adjust the viscosity of the slurry, controlling the viscosity of the adjusted interfacial stress-relieving slurry to be between 15 mPa·s and 50 mPa·s. By adopting the above technical solution, the viscosity of the slurry is limited to a specific range, matching the hydrodynamic requirements of subsequent coating or spraying processes. This prevents the slurry from sagging or unevenly drying due to evaporation during coating, ensuring that the thickness of the localized layer after drying is precisely controlled at the micrometer level, and maintaining surface smoothness.

[0016] Preferably, the specific implementation of the step of forming the interface localized layer is as follows: The interface stress-relieving slurry is directly coated onto the surface of the positive electrode layer or the bulk electrolyte layer using a spraying or printing process, and then dried under vacuum conditions to evaporate the solvent and form the interface localized layer; alternatively, the interface stress-relieving slurry is pre-coated onto a substrate film, dried to form the interface localized layer, and then transferred to the surface of the positive electrode layer using a pressure roller. By adopting the above technical solutions, a layering process suitable for different production environments is provided. The direct coating process ensures the tightness of the bond between the localized layer and the substrate. The substrate film transfer process avoids direct contact between the liquid solvent and the positive electrode sheet or electrolyte layer, eliminating the potential wetting effect of residual solvent on the active material lattice or solid electrolyte structure.

[0017] Preferably, the multi-segment hot-press curing molding process includes a preheating activation stage. Specific process parameters are: applying a pressure of 20MPa-50MPa at a temperature of 50℃-70℃ and holding the pressure for 10-20 minutes to activate the polymer chain segment movement. By adopting the above technical solution, a specific preheating temperature is set that crosses the glass transition temperature of the conductive elastomer, activating the thermal mobility of the flexible polymer chain segments. Under relatively low initial pressure, the polymer network undergoes slow creep, filling the macroscopic pore spaces between layers, expelling residual gas, and establishing a preliminary uniform bonding interface, providing a smooth physical contact basis for subsequent bonding stages.

[0018] Preferably, the multi-stage hot-press curing process, after the preheating and activation stage, also includes a high-temperature and high-pressure bonding stage. Specific process parameters are: heating to 100℃-120℃ and applying pressure of 300MPa-500MPa, holding at that temperature and pressure for 5-15 minutes, to achieve dense physical bonding and chemical bonding between the layers. By adopting the above technical solution, increasing the temperature enhances the thermodynamic reactivity of the molecules, and applying high pressure forces the physical distance between interfaces to shorten to within the atomic radius range of chemical bond formation. Polar side-chain functional groups extensively combine with polar sites on adjacent interfaces under high temperature and high pressure, completely transforming the original physically stacked interfaces into robust chemically bonded interfaces, thus solidifying the microstructure network of the stress-relieving localized layers.

[0019] This invention provides an all-solid-state battery with a stress-relieving localization layer at the electrode interface and a method for manufacturing the same. It offers the following advantages:

[0020] 1. This invention achieves physical and electrical decoupling of the internal spatial functions of the battery by strictly controlling the thickness of the stress-relieving local layer containing conductive elastomer to 1μm to 5μm. It provides mechanical buffering at the electrode interface, while preventing polymer materials from entering the bulk solid electrolyte layer and avoiding the blockage of inorganic ion conduction network by polymers. This ensures the low impedance characteristics of lithium ion long-distance transmission, enabling the all-solid-state battery to still have high capacity output performance under high current density.

[0021] 2. This invention utilizes a specific mass fraction of conductive elastomer mixed with nano-sized sulfide particles to construct a stress dispersion network between the electrode and the bulk electrolyte. During the battery charge-discharge cycle, the local stress generated by the repeated expansion and contraction of the positive electrode active material lattice volume can be effectively absorbed and dissipated through the physical extension and deformation of the flexible polymer backbone, avoiding excessive stress concentration at the interface, blocking the propagation of strain-induced microcracks into the solid electrolyte, and maintaining the physical continuity of the interface.

[0022] 3. This invention employs a conductive elastomer with polar side chain functional groups, which endows the physical interface with the ability to dynamically and spontaneously repair itself. When the electrode interface undergoes microscopic peeling due to stress exceeding the bonding limit, the polymer chain segments creep under the drive of thermal motion to fill the physical gaps. The polar functional groups suspended by the side chains then reform reversible non-covalent chemical bonds with the detached positive electrode or inorganic electrolyte surface, promoting the spontaneous reconstruction of microscale ion and electron channels, restoring the increased interfacial contact resistance to a low impedance level, and ensuring the long cycle life of the all-solid-state battery. Attached Figure Description

[0023] Figure 1 This is a diagram showing the change in physical intensity from the interface to the interior of the present invention.

[0024] Figure 2 This is a graph showing the charge / discharge cycle count and the rate of increase in internal resistance of the present invention.

[0025] Figure 3 This is a diagram showing the capacity retention rate during high-rate discharge according to the present invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Preparation Examples 1-3:

[0028] Preparation Example 1: This preparation example provides a method for preparing a carboxyl-containing conductive elastomer dispersion, including the following steps:

[0029] 3,4-Ethylenedioxythiophene monomer and 3,4-ethylenedioxythiophene-formic acid monomer were mixed at a molar ratio of 4:1. This monomer mixture was added to an aqueous solution of polystyrene sulfonate with a solid content of 18 wt%, maintaining a polystyrene sulfonate solids to total monomer mass ratio of 2.5:1. The mixture was ultrasonically dispersed at room temperature for 30 minutes to form an emulsion. Under nitrogen protection, sodium persulfate and anhydrous ferric sulfate were added to the emulsion, with a sodium persulfate to total monomer molar ratio of 1.5:1 and anhydrous ferric sulfate added at 1% of the total monomer mass. The reaction was continuously stirred at 20°C for 24 hours. After the reaction, the mixture was dialyzed in deionized water for 4 days using a dialysis bag with a molecular weight cutoff of 14,000. Subsequently, water was removed by freeze-drying to obtain a solid powder. This solid powder was added to a mixed solvent of anhydrous acetonitrile and propylene carbonate at a mass ratio of 9:1, and ultrasonically dispersed to obtain a carboxyl-containing conductive elastomer dispersion with a solid content of 5 wt%.

[0030] Preparation Example 2: This preparation example provides a method for preparing a conductive elastomer dispersion containing amide groups, including the following steps:

[0031] 3,4-Ethylenedioxythiophene monomer and 3,4-ethylenedioxythiophene-acetamide monomer were mixed at a molar ratio of 6:1. This monomer mixture was added to an aqueous solution of polystyrene sulfonate with a solid content of 18 wt%, maintaining a polystyrene sulfonate solids to total monomer mass ratio of 2:1. The mixture was ultrasonically dispersed at room temperature for 40 minutes to form an emulsion. Under nitrogen protection, sodium persulfate and anhydrous ferric sulfate were added to the emulsion, with a sodium persulfate to total monomer molar ratio of 1.2:1 and anhydrous ferric sulfate added at 0.8% of the total monomer mass. The reaction was continuously stirred at 25°C for 20 hours. After the reaction, the mixture was dialyzed in deionized water for 5 days using a dialysis bag with a molecular weight cutoff of 14000. Subsequently, water was removed by freeze-drying to obtain a solid powder. This solid powder was added to a mixed solvent of anhydrous acetonitrile and propylene carbonate at a mass ratio of 8:2, and ultrasonically dispersed to obtain a 5 wt% amide-containing conductive elastomer dispersion.

[0032] Preparation Example 3: This preparation example provides a method for preparing a polyurethane-based conductive elastomer dispersion, including the following steps:

[0033] Polytetrahydrofuran ether glycol was dehydrated under vacuum at 110°C for 2 hours. After cooling to 80°C, 4,4'-diphenylmethane diisocyanate was added, with the molar ratio of polytetrahydrofuran ether glycol to 4,4'-diphenylmethane diisocyanate strictly controlled at 1:2. The reaction was carried out under nitrogen protection with constant temperature stirring for 2 hours to obtain an isocyanate-terminated polyurethane prepolymer. 2,2-dimethylolpropionic acid and 1,4-butanediol were added to the prepolymer as chain extenders, with the molar ratio of prepolymer, 2,2-dimethylolpropionic acid, and 1,4-butanediol controlled at 1:0.5:0.5. The reaction was continued at 80°C for 3 hours to generate a highly elastic thermoplastic polyurethane elastomer. This polyurethane elastomer was ground into powder and added to anhydrous acetonitrile, then dissolved under reflux at 60°C to prepare a polyurethane solution with a solid content of 5 wt%. The polyurethane solution was mixed with the carboxyl-containing conductive elastomer dispersion obtained in Preparation Example 1 at a mass ratio of 1:1, and mechanically stirred at room temperature for 2 hours to obtain a polyurethane-containing conductive elastomer dispersion.

[0034] Examples 1-3:

[0035] Example 1: This example provides an all-solid-state battery with an electrode interface stress buffer layer, including the following steps:

[0036] Li6PS5Cl sulfide solid electrolyte powder with an average particle size D50 of 2.0 μm was mixed with 0.1 wt% polytetrafluoroethylene powder and dry-rolled to prepare an independent solid electrolyte membrane with a thickness of 50 μm, which served as the bulk electrolyte layer. Li6PS5Cl particles were pulverized to an average particle size D50 of 200 nm using high-energy wet ball milling. These nano-sized Li6PS5Cl particles were dispersed in the carboxyl-containing conductive elastomer dispersion obtained in Preparation Example 1. The mass fraction of the polymer material in the total weight of the dried interfacial localized layer was controlled to be 10 wt%, and the viscosity of the slurry was adjusted to 30 mPa·s with anhydrous acetonitrile to obtain an interfacial stress-relieving slurry. The above interfacial stress-relieving slurry was uniformly sprayed onto the surface of the positive electrode active material layer of the positive electrode using an automatic spraying device. The solvent was evaporated under vacuum conditions, and the thickness of the dried interfacial localized layer was controlled to be 3 μm. A positive electrode with a localized interface layer on one side, a bulk electrolyte layer, and a lithium metal negative electrode are stacked sequentially, so that the localized interface layer directly contacts the positive electrode active material layer and the bulk electrolyte layer. The stacked component is placed in a uniaxial press and preheated at 60°C with a pressure of 30 MPa for 15 minutes to activate polymer chain segment movement. Then, the temperature is raised to 110°C and a pressure of 400 MPa is applied and held for 10 minutes to achieve dense physical bonding and chemical bonding of each layer. After cooling, it is encapsulated to obtain an all-solid-state battery with an electrode interface stress buffer layer.

[0037] Example 2: This example provides an all-solid-state battery with an electrode interface stress buffer layer, including the following steps:

[0038] Li6PS5Cl powder with an average particle size D50 of 2.0 μm was mixed with 0.1 wt% polytetrafluoroethylene powder and a freestanding solid electrolyte membrane with a thickness of 80 μm was prepared by dry roll forming as the bulk electrolyte layer. Li6PS5Cl particles were pulverized to an average particle size D50 of 150 nm using high-energy wet ball milling and dispersed in the amide-containing conductive elastomer dispersion obtained in Preparation Example 2. The mass fraction of the polymer material in the total weight of the interface localized layer after drying was controlled to be 5 wt%, and the viscosity of the slurry was adjusted to 15 mPa·s with anhydrous acetonitrile to obtain an interface stress-relieving slurry. The interface stress-relieving slurry was coated onto one side of the pre-formed bulk electrolyte membrane using gravure printing. The solvent was evaporated by vacuum drying, and the thickness of the interface localized layer after drying was controlled to be 1 μm. The positive electrode, the bulk electrolyte layer with the interface localized layer, and the lithium metal negative electrode were stacked sequentially to bond the interface localized layer to the positive electrode. The battery is placed in a uniaxial press and preheated at 60°C with a pressure of 20 MPa for 20 minutes. Then, the temperature is raised to 100°C and a pressure of 300 MPa is applied for 15 minutes. After cooling, the battery is packaged to obtain an all-solid-state battery with an electrode interface stress buffer layer.

[0039] Example 3: This example provides an all-solid-state battery with an electrode interface stress buffer layer, including the following steps:

[0040] Li6PS5Cl powder with an average particle size D50 of 2.0 μm was mixed with 0.1 wt% polytetrafluoroethylene powder, and a 100 μm thick independent solid electrolyte membrane was prepared by dry roll forming as the bulk electrolyte layer. Li6PS5Cl particles were pulverized to an average particle size D50 of 100 nm using high-energy wet ball milling and dispersed in the polyurethane-based conductive elastomer dispersion obtained in Preparation Example 3. The mass fraction of the polymer material in the total weight of the interface localized layer after drying was controlled to be 20 wt%, and the viscosity of the slurry was adjusted to 50 mPa·s with anhydrous acetonitrile to obtain an interface stress-relieving slurry. This slurry was pre-coated onto a Teflon substrate film, and after drying, a 5 μm thick interface localized layer was formed. This interface localized layer was then transferred to the surface of the positive electrode using a pressure roller. A positive electrode with an interface localization layer, a bulk electrolyte layer, and a lithium metal negative electrode are stacked sequentially and placed in a uniaxial press. The battery is preheated at 60°C with a pressure of 50 MPa for 10 minutes. Then, the temperature is raised to 120°C and a pressure of 500 MPa is applied for 5 minutes. After cooling, the battery is packaged to obtain an all-solid-state battery with an electrode interface stress buffer layer.

[0041] Comparative Examples 1-4:

[0042] Comparative Example 1: Compared with Example 1, the difference is that the interface localization layer is not set separately. Instead, the carboxyl-containing conductive elastomer dispersion obtained in Example 1 is directly and uniformly mixed with Li6PS5Cl powder with an average particle size D50 of 2.0 μm and dried. It is then dry-pressed into a single solid electrolyte membrane with a thickness of 53 μm and uniform distribution of polymer material. All other aspects are the same.

[0043] Comparative Example 2: Compared with Example 1, the difference is that no interface localization layer is set, and no conductive elastomer polymer material with polar functional groups is added. The positive electrode is directly contacted and stacked with a pure bulk solid electrolyte membrane with a thickness of 50 μm. All other aspects are the same.

[0044] Comparative Example 3: Compared with Example 1, the difference is that when preparing the interfacial stress-relieving slurry, the conductive elastomer used is a conventional poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid dispersion without any polar side chain functional groups; all other aspects are the same.

[0045] Comparative Example 4: Compared with Example 1, the difference is that the amount of interfacial stress-relieving slurry sprayed is increased, the thickness of the local interfacial layer after drying is controlled to be 15 μm, and the thickness of the bulk solid electrolyte membrane is adjusted to 38 μm, while the rest are the same.

[0046] Test Examples 1-4:

[0047] Test Example 1: Verification Test of Local Mechanical Strength and Spatial Distribution of Interface

[0048] The all-solid-state batteries obtained in Examples 1 to 3 and Comparative Examples 1 and 3 were disassembled in an argon glove box with a dew point below -60°C. Effective cross-sectional samples containing the positive electrode layer and the solid electrolyte layer were cut off, embedded in epoxy resin, and treated with an argon ion cross-section polisher to expose a flat physical interface between the positive electrode and the solid electrolyte.

[0049] The polished sample is fixed on the sample stage of the cutting interface property evaluation device, a diamond cutting tool is configured, and the cutting edge of the tool is adjusted to be parallel to the interface.

[0050] The horizontal cutting speed was set to 0.5 μm / s, and the vertical feed rate was set to 0.05 μm / s. The tool was controlled to perform continuous vertical cutting from the interface (0 μm from the interface depth) toward the bulk electrolyte layer, with the maximum cutting depth set to 20 μm.

[0051] Continuously record the horizontal force variation data during the cutting process, and extract the cutting horizontal force value at the set depth node, with the unit being N / m. Record the basic cutting force at the depth of the bulk electrolyte layer as the reference value Fb to calculate the strength ratio.

[0052] Test results:

[0053] Table 1. Cutting horizontal force data (N / m) at different depths for each embodiment and comparative example.

[0054]

[0055] Results analysis:

[0056] The test data results in Table 1 reflect the findings of this invention. Figure 1 middle. Figure 1 The curves showing the relationship between electrode interface distance and cutting horizontal force in the embodiments and comparative examples are illustrated. Figure 1 The horizontal axis label is Distance from the interface (μm), which represents the distance from the bonding interface in micrometers. The coordinate 0 represents the interface between the electrode and the solid electrolyte. An increasing value indicates deeper penetration into the electrolyte phase layer. The vertical axis label is Cutting horizontal force (N / m), which represents the cutting horizontal force in Newtons per meter. It represents the physical cutting strength of the material at the corresponding depth. A larger value indicates a stronger physical bonding force and is less prone to peeling.

[0057] Based on the data in Table 1 and Figure 1 The curve trend shows that the cutting horizontal force in Examples 1 to 3 exhibited extreme value ranges within a depth range of 1 μm to 5 μm from the interface. For example... Figure 1 As shown by the solid line (corresponding to Example 1, thickness 3 μm) and the dashed line (corresponding to Example 2, thickness 1 μm), the maximum cutting horizontal force Fi reached 856.3 N / m, 905.2 N / m, and 845.3 N / m, respectively. When the cutting depth exceeded the designed thickness of the interface localization layer and entered the bulk electrolyte layer, the cutting horizontal force rapidly decayed, stabilizing at a basic cutting force Fb level of approximately 220 N / m after the depth exceeded 10 μm. In each example, the ratio of the maximum cutting horizontal force Fi to the bulk cutting horizontal force Fb was greater than 3.0. The test results demonstrate that the functionalized polymer material did not undergo disordered diffusion into the bulk layer during the hot pressing process, achieving localized control of the material's spatial distribution, ensuring the low impedance characteristics of the pure inorganic state of the bulk electrolyte layer, and confirming the precise realization of the spatial functional decoupling mechanism in the physical structure.

[0058] correspond Figure 1 The horizontal dashed line in the figure (Comparative Example 1) shows that the cutting horizontal force of the battery using the overall uniform mixing process is uniformly distributed across the entire test depth range of 0μm to 20μm, remaining between 285.4 N / m and 331.4 N / m. The overall cutting force is slightly higher than that of a pure inorganic phase layer, but the interface-specific enhancement effect is not achieved. Figure 1The single-point dashed line in Example 3 (Comparative Example 3) shows a localized layer at the same position as in the embodiment, but using a conductive elastomer without polar functional groups. Its maximum interfacial cutting horizontal force is only 425.8 N / m. The peak interfacial strength of the embodiment is significantly higher than that of Comparative Example 3, indicating that the formation of non-covalent chemical bonds between the polar functional groups of the polymer side chains and the surfaces of the positive electrode active material and the sulfide electrolyte is the decisive factor in significantly improving the interfacial mechanical adhesion energy. The high-strength bonding network formed within a thickness range of 1 μm to 5 μm serves as a buffer layer, providing the mechanical basis for absorbing the mechanical strain energy generated by the volume change of the positive electrode active material during charging and discharging. This prevents the propagation of microcracks caused by stress concentration into the bulk phase layer, confirming the mechanical dispersion mechanism of interfacial stress.

[0059] Test Example 2: Interface Contact Resistance Recovery Test under No Pressure

[0060] The all-solid-state batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were placed in a constant temperature environment of 25°C, and all external packaging fixtures and pressurizing devices were removed, so that the batteries were in a free state without any external mechanical pressure.

[0061] The positive and negative leads of the battery were connected to an electrochemical workstation, and the initial interfacial contact resistance of the battery was measured by electrochemical impedance spectroscopy under the conditions of AC amplitude of 10mV and frequency range of 1MHz to 0.1Hz.

[0062] By applying a momentary quantitative tensile stress in a direction perpendicular to the electrode interface using a microelectromechanical stretching stage, an artificial mechanical peel of about 1 μm is generated at the interface between the positive electrode and the solid electrolyte inside the battery. It is confirmed that the semicircular arc representing the interface contact resistance in the impedance spectrum increases significantly at this time, and the resistance value at this time is recorded as the initial peel resistance.

[0063] The battery in the stripped state was left to stand in situ for 12 hours without external pressure. During this period, the AC impedance spectrum was automatically collected by the electrochemical workstation at specified intervals to record the changes in interfacial contact resistance at different time points.

[0064] Test results:

[0065] Table 2. Changes in contact resistance at the interface during the resting period after micromechanical peeling for each embodiment and comparative example.

[0066]

[0067] Results analysis:

[0068] The test data results in Table 2 reflect the findings of this invention. Figure 2 middle. Figure 2 The dynamic curves showing the relationship between the battery's resting time and the interface contact resistance after interface separation are shown. Figure 2 The horizontal axis label is Restingtime (h), which represents the resting time at room temperature without pressure, in hours; the vertical axis label is Interface contact resistance (Ω), which represents the contact resistance of the interface, in ohms. A decrease in the value indicates the re-establishment of physical and electrical contact at the interface.

[0069] Based on the data in Table 2 and Figure 2 The curves show that the contact resistance of Examples 1 to 3 rapidly increased to between 318.4 Ω and 365.1 Ω at the moment of peeling, but during the subsequent resting process, the resistance values ​​showed a continuous and significant decreasing trend. After 12 hours of resting, the resistance of Example 1 decreased from 342.7 Ω to 28.5 Ω, the resistance of Example 2 decreased to 39.4 Ω, and the resistance of Example 3 decreased to 24.1 Ω, all returning to a low impedance level close to the initial state. The test results show that, without relying on external large-scale mechanical pressure devices, the high-concentration functionalized polymer material aggregated in the localized layer of the interface can re-creep and fill the peeling gap under the driving force of the molecular thermal motion of its flexible chain segments. At the same time, the polar functional groups suspended by the polymer side chains spontaneously reform non-covalent interactions such as hydrogen bonds or coordination bonds with the detached positive electrode active material surface and sulfide electrolyte surface. This chemical bond breaking and recombination characteristic promotes the spontaneous reconstruction of ion and electron conduction channels at the microscale, confirming the existence and effectiveness of the dynamic interface restoring mechanism in the present invention.

[0070] Comparative Example 2, lacking any polymer material, exhibited a high contact resistance of 489.3 Ω after peeling, which remained at 485.9 Ω for 12 hours, demonstrating the irreversible nature of interface fracture in pure inorganic solids. Comparative Example 1, employing a uniformly mixed structure with extremely low polymer concentration at the interface, maintained a high contact resistance of 382.1 Ω, proving that insufficient concentration cannot achieve interface repair. Although Comparative Example 3 incorporated a localized layer at the interface, the selected conductive elastomer lacked polar side-chain functional groups, resulting in a contact resistance of 291.3 Ω after 12 hours, showing a very limited decrease. The data from Comparative Example 3 further confirms that physical creep of the polymer backbone alone cannot rebuild high-strength interfacial contacts; an active side-chain polar chemical bond network is a necessary condition for achieving spontaneous interface repair and maintaining stable operation of all-solid-state batteries over the long term.

[0071] Test Example 3: Comparison Test of Long Cycle Life and Interface Physical Stability

[0072] The all-solid-state batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were placed in a constant temperature test chamber at 25°C and left to stand for 2 hours to ensure that the internal temperature of the battery reached thermal equilibrium.

[0073] Connect the positive and negative terminals of the battery to a high-precision battery charge-discharge testing system, and set the operating voltage range to 2.5V to 4.2V. Perform one activation charge-discharge cycle at a current density of 0.1C in the first cycle.

[0074] After the first activation cycle, the charge / discharge current density was adjusted to 0.5C, and long-term cyclic testing of constant current / constant voltage charging and constant current discharging was conducted, with the number of cycles set to 500. 4. At the end of the discharge phase of the 1st (initial state), 100th, 200th, 300th, 400th, and 500th cycles, a DC internal resistance test method was used. A 1C discharge pulse current was applied for 10 seconds, the voltage drop was recorded, and the total internal resistance of the battery was calculated. The rate of increase in internal resistance after 500 cycles was statistically analyzed.

[0075] Test results:

[0076] Table 3. Internal resistance changes of each embodiment and comparative example during a long-cycle process at 0.5C.

[0077]

[0078] Results analysis:

[0079] The test data results in Table 3 are reflected in the present invention. Figure 3 middle. Figure 3 The dynamic curves showing the relationship between the number of cycles and the total internal resistance of an all-solid-state battery during a 0.5C cycle test are presented. Figure 3 The horizontal axis label is Cyclenumber (times), representing the number of charge-discharge cycles, in units of cycles; the vertical axis label is Internal resistance (Ω), representing the total internal resistance of the battery, in units of ohms. The magnitude of the increase in the value reflects the degree of degradation and peeling of the internal physical interfaces of the battery during charge-discharge cycles.

[0080] Based on the data in Table 3 and Figure 3The curves show that the initial internal resistance of Examples 1 to 3 remained at a low level of 20.3Ω to 24.5Ω. After 500 charge-discharge cycles, the resistance increased to 26.2Ω, 29.3Ω, and 24.1Ω, respectively, with the resistance increase rate strictly controlled within 20%. This result indicates that the interface localization layer set in the examples maintained a high degree of physical continuity and electrical connectivity after long-term expansion and contraction of the positive electrode active material lattice. The localized conductive elastomer network effectively absorbed and dispersed the local tensile and shear stresses at the interface through the extension and deformation of the flexible polymer backbone. At the same time, even if microscale interface peeling occurs during cycling, the polar functional groups suspended by the side chains can undergo creep through molecular thermal motion, reforming non-covalent chemical bonds with the inorganic layer surface, achieving dynamic restabilization of the electrical and ion contact channels, and maintaining excellent long-term cycling physical stability.

[0081] Comparative Example 2, lacking any polymer elastomer material, initially exhibited a low resistance of 18.4 Ω. However, with increasing cycle count, the interface could not withstand the mechanical strain energy generated by lattice volume changes, causing the resistance to surge exponentially, reaching a high of 534.8 Ω after 500 cycles. This demonstrates that the pure inorganic interface undergoes irreversible brittle fracture and large-area delamination under cyclic stress. Comparative Example 1, employing a uniform mixing process, not only had an initial resistance as high as 41.2 Ω but also, due to insufficient buffer material concentration at the interface during cycling, failed to form a continuous stress dispersion network, resulting in a resistance increase to 88.5 Ω, indicating significant degradation. Comparative Example 3, although possessing an interfacial localized layer, lacked a dynamic fracture-recombination mechanism for polar chemical bonds, preventing self-repair at the interface. Microcracks accumulated and propagated continuously during cycling, causing the resistance to steadily climb from 23.1 Ω to 76.9 Ω. Comparative Example 4 increased the localization layer thickness to 15 μm. Although its structural mechanical stability was acceptable and the increase in resistance after 500 cycles was small, its initial internal resistance was as high as 35.6 Ω, and its absolute resistance value was relatively high throughout its entire life cycle. The above comparative data confirms that strictly localizing the conductive elastomer with polar side chains within the 1 μm to 5 μm interface region is the only effective way to simultaneously resolve the contradiction between the low bulk impedance requirement and high interface cycle stability of all-solid-state batteries.

[0082] Test Example 4: High-load output characteristics (rate performance) comparison test

[0083] The all-solid-state batteries prepared in Examples 1 to 3, as well as Comparative Examples 1 and 4, were placed in a constant temperature test chamber at 25°C and left to stand for 3 hours to ensure that the batteries reached thermal equilibrium.

[0084] Connect the positive and negative leads of the battery to a high-precision battery charge-discharge testing system, and set the operating voltage test range to 2.5V to 4.2V. In the first cycle, perform constant current charging at a current density of 0.1C until the voltage reaches 4.2V, then switch to constant voltage charging until the current drops to 0.02C. Next, perform constant current discharge at a current density of 0.1C to 2.5V to complete the basic electrochemical activation and record the 0.1C discharge specific capacity.

[0085] In subsequent test cycles, a constant current and constant voltage charging regime of 0.2C was maintained, and constant current discharge tests were conducted sequentially using current densities of 0.5C, 1C, and 2C. Three charge-discharge cycles were performed consecutively at each discharge rate, and the discharge capacity of the last cycle was extracted as the effective discharge specific capacity data at that discharge rate.

[0086] Test results:

[0087] Table 4. Specific capacity data (mAh / g) of each embodiment and comparative example at different discharge rates

[0088]

[0089] Results analysis:

[0090] According to the data in Table 4, at a base discharge rate of 0.1C, Examples 1 to 3 achieved discharge specific capacities of 185.4 mAh / g, 188.1 mAh / g, and 182.6 mAh / g, respectively. When the discharge rate was increased to the high-load 2C, the discharge specific capacities remained at 128.5 mAh / g, 133.2 mAh / g, and 124.7 mAh / g, respectively, demonstrating a high capacity retention rate at 2C compared to 0.1C. The test results indicate that completely confining the polymer material responsible for interface bonding and stress buffering within an extremely thin region of 1 μm to 5 μm from the interface allows the bulk solid electrolyte layer, with a thickness of tens of micrometers, to maintain a completely inorganic state. After crossing the extremely thin interface localization layer, lithium ions can rapidly enter the low-resistivity bulk inorganic lattice network for long-distance transport. This spatial functional decoupling mechanism physically avoids the obstacle of flexible polymer materials to the bulk ion conductivity of the battery, ensuring the power output characteristics of the all-solid-state battery at high current densities.

[0091] Comparative Example 1, employing a process of uniformly mixing polymer materials with a solid electrolyte, exhibited a discharge specific capacity of only 165.8 mAh / g at a low rate of 0.1C. When the discharge rate was increased to 2C, the specific capacity plummeted to 24.6 mAh / g. This result demonstrates that introducing a large amount of polymer material into the bulk layer physically blocks point-to-point contact between sulfide inorganic particles, significantly increasing the ohmic impedance of bulk ion transport and leading to severe capacity degradation under high load conditions. Comparative Example 4, although employing an interface localization design, increased the localization layer thickness to 15 μm, resulting in a 2C discharge specific capacity decrease to 41.8 mAh / g. The data further confirms that an excessively thick localization layer significantly elongates the migration path of lithium ions through the polymer-rich region, exacerbating concentration polarization at the electrode interface and thus impairing the battery's rate performance. Based on the above results, it can be concluded that the conductive elastomer must be strictly confined to the interface region below 5 μm in spatial scale in order to meet the performance requirements of all-solid-state batteries for high load current output while suppressing interface peeling through mechanical dispersion mechanism.

Claims

1. A fully solid-state battery with a stress-relieving localization layer at the electrode interface, characterized in that, A stress-relieving localization layer is disposed at the electrode interface of the all-solid-state battery, and the stress-relieving localization layer is made of components comprising the following mass fractions: 5wt%-20wt% of conductive elastomers containing polar side chain functional groups; 80wt%-95wt% nano-sized sulfide solid electrolyte particles; The thickness of the stress-relieving localization layer is controlled to be 1μm-5μm.

2. The all-solid-state battery with a stress-relieving localization layer at the electrode interface according to claim 1, characterized in that, The polar side chain functional group is one of carboxyl, amide, or polyurethane groups; The conductive elastomer is one of a carboxyl-containing conductive elastomer, an amide-containing conductive elastomer, or a polyurethane-containing conductive elastomer.

3. The all-solid-state battery with a stress-relieving localization layer at the electrode interface according to claim 2, characterized in that, When the conductive elastomer is a carboxyl-containing conductive elastomer, the carboxyl-containing conductive elastomer is obtained by oxidative copolymerization and drying of a mixture of 3,4-ethylenedioxythiophene monomer and 3,4-ethylenedioxythiophene-formic acid monomer in an aqueous solution of polystyrene sulfonic acid. The molar ratio of the 3,4-ethylenedioxythiophene monomer to the 3,4-ethylenedioxythiophene-formic acid monomer is (3-5):1, and the mass ratio of polystyrene sulfonate solids to total monomers is (2-3):

1.

4. The all-solid-state battery with a stress-relieving localization layer at the electrode interface according to claim 2, characterized in that, When the conductive elastomer is a polyurethane-based conductive elastomer, the polyurethane-based conductive elastomer is composed of a polyurethane elastomer generated by reacting an isocyanate-terminated polyurethane prepolymer with a chain extender, and a carboxyl-based conductive elastomer mixed at a mass ratio of (0.8-1.2):

1. The molar ratio of the prepolymer, 2,2-dimethylolpropionic acid as a chain extender, and 1,4-butanediol is 1:(0.4-0.6):(0.4-0.6).

5. The all-solid-state battery with a stress-relieving localization layer at the electrode interface according to claim 1, characterized in that, The average particle size D50 of the nano-sulfide solid electrolyte particles is 100nm-200nm. The thickness of the bulk solid electrolyte layer is 50μm-100μm, and the bulk solid electrolyte layer is formed from raw materials including sulfide solid electrolyte powder with an average particle size D50 of 2.0μm and polytetrafluoroethylene powder.

6. A method for manufacturing an all-solid-state battery with a stress-relieving localization layer at the electrode interface, characterized in that, The method for preparing an all-solid-state battery with a stress-relieving localization layer at the electrode interface as described in any one of claims 1-5 includes the following steps: Bulk solid electrolyte powder is molded to prepare an independent solid electrolyte membrane as a bulk electrolyte layer; The sulfide solid electrolyte particles were pulverized, and the pulverized nanoparticles were dispersed in a conductive elastomer dispersion containing polar side chain functional groups. The viscosity of the slurry was adjusted by solvent to obtain an interfacial stress-relieving slurry. The interfacial stress-relieving slurry is coated and dried to form an interfacial localized layer with a thickness of 1 μm to 5 μm. The positive electrode layer, the bulk electrolyte layer, and the lithium metal negative electrode layer are stacked so that the interface localization layer directly contacts the active material layer of the positive electrode layer and the bulk electrolyte layer. The stacked components are placed in a press for multi-stage hot pressing and curing, which allows the polar side chain functional groups in the interface localization layer to establish chemical bonds with the adjacent interfaces. After cooling, the components are encapsulated to obtain an all-solid-state battery with an electrode interface equipped with a stress-relieving localization layer.

7. The all-solid-state battery with a stress-relieving localization layer at the electrode interface according to claim 6, and its manufacturing method, characterized in that, In the step of obtaining the interfacial stress relief slurry, anhydrous acetonitrile is used as a solvent to adjust the viscosity of the slurry, and the viscosity of the adjusted interfacial stress relief slurry is controlled to be 15 mPa·s-50 mPa·s.

8. The all-solid-state battery with a stress-relieving localization layer at the electrode interface according to claim 6, and its manufacturing method, characterized in that, The specific implementation method for forming the local interface layer is as follows: The interfacial stress-relieving slurry is directly coated onto the surface of the positive electrode layer or the surface of the bulk electrolyte layer using a spraying or printing process, and the solvent is dried and evaporated under vacuum conditions to form an interfacial localized layer. Alternatively, the interfacial stress-relieving slurry can be pre-coated onto a substrate film, dried to form an interfacial localization layer, and then transferred to the surface of the positive electrode layer using a pressure roller.

9. The all-solid-state battery with a stress-relieving localization layer at the electrode interface according to claim 6, and its manufacturing method, characterized in that, The multi-stage hot-press curing process includes a preheating and activation stage, with specific process parameters as follows: Applying a pressure of 20MPa-50MPa at a temperature of 50℃-70℃ and maintaining the temperature and pressure for 10-20 minutes activates the movement of polymer chain segments.

10. The all-solid-state battery with a stress-relieving localization layer at the electrode interface according to claim 6, and its manufacturing method, characterized in that, The multi-stage hot-press curing molding process, following the preheating and activation stage, also includes a high-temperature and high-pressure bonding stage. Specific process parameters are as follows: The temperature is raised to 100℃-120℃ and a pressure of 300MPa-500MPa is applied. The temperature and pressure are maintained for 5-15 minutes to achieve dense physical bonding and chemical bonding between the layers.

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