A solid-state lithium battery and its preparation method

Abstract

This invention provides a solid-state lithium battery and its fabrication method. The solid-state lithium battery includes a positive electrode, a solid electrolyte layer, and a negative electrode, which are sequentially stacked. The negative electrode includes a first conductive polymer, and the solid electrolyte layer includes a second conductive polymer. This battery can reduce solid-solid interface impedance and improve the transport continuity and structural stability at the interface, thereby helping to suppress interfacial side reactions and structural degradation under cycling and high-voltage conditions, achieving stable operation over long cycles and a wide temperature range.

Description

Technical Field

[0001] This application relates to the field of batteries, and more particularly to a solid-state lithium battery and its preparation method. Background Technology

[0002] Lithium-ion rechargeable batteries are key energy devices in large-scale industrial and commercial energy storage, electric vehicles, and portable mobile devices. However, mainstream lithium-ion batteries generally use organic carbonate-based liquid electrolytes, which pose safety risks of electrolyte leakage, combustion, and even explosion under harsh operating conditions such as high temperature and high current charging and discharging. This severely restricts the development of lithium battery technology towards higher performance. Currently, solid-state batteries, by replacing flammable liquid electrolytes with solid electrolytes, can effectively avoid the risks of electrolyte leakage, combustion, and even explosion. Therefore, solid-state lithium batteries are now widely used in new energy vehicles, large-scale energy storage systems, aerospace, and other fields.

[0003] However, solid-state batteries also face the technical challenge of high solid-solid interface impedance in practical applications. The solid-solid interface contact characteristics of solid-state batteries directly affect the ion transport efficiency and cycle stability, thereby impacting the energy density, cycle life, and low-temperature performance. Therefore, it is urgent to optimize the solid-solid interface contact performance of solid-state batteries to achieve a balance between energy density, low-temperature performance, and cycle stability.

[0004] To improve the solid-solid interface contact performance of solid-state batteries, existing technologies attempt to prepare solid electrolyte membranes through high solid content film-forming processes to reduce solvent usage and minimize damage to the membrane's microstructure, thereby improving the interface stability of solid-state batteries. Furthermore, gradient particle size design is combined to enhance the compactness of the solid electrolyte membrane, thereby reducing the interfacial contact resistance problem caused by excessive porosity of the solid electrolyte membrane.

[0005] However, even with the improvements made by existing technologies, solid-state batteries still suffer from capacity decay due to interface degradation in low-temperature environments and during long-term cycling. Especially in high-voltage systems, insufficient interface stability becomes a key bottleneck restricting solid-state battery performance. Therefore, how to reduce interface impedance and improve interface stability in solid-state lithium batteries to achieve stable operation over long cycles and a wide temperature range has become an urgent technical problem to be solved. Summary of the Invention

[0006] This application provides a solid-state lithium battery that can reduce solid-solid interface impedance and improve transmission continuity and structural stability at the interface, thereby helping to suppress interface side reactions and structural degradation under cycling and high-voltage conditions, so as to achieve stable operation under long cycling and wide temperature range.

[0007] This application provides a method for preparing the above-mentioned solid-state lithium battery. The method is simple, highly reproducible, and can prepare a solid-state lithium battery with reduced interfacial contact impedance between the electrode layer and the solid electrolyte layer at a lower cost.

[0008] In a first aspect, this application provides a solid-state lithium battery, comprising a positive electrode, a solid electrolyte layer and a negative electrode stacked sequentially, wherein the negative electrode comprises a first conductive polymer and the solid electrolyte layer comprises a second conductive polymer.

[0009] In the solid-state lithium battery described above, a first quasi-solid-state electrolyte layer is provided between the solid electrolyte layer and the negative electrode, and the first quasi-solid-state electrolyte layer includes a third conductive polymer.

[0010] The solid-state lithium battery described above, wherein the positive electrode includes a fourth conductive polymer; and / or,

[0011] A second quasi-solid electrolyte layer is provided between the positive electrode and the solid electrolyte layer, and the second quasi-solid electrolyte layer includes a third conductive polymer.

[0012] In the solid-state lithium battery described above, at least one of the first conductive polymer, the second conductive polymer, the third conductive polymer, and the fourth conductive polymer is grafted with modified multifunctional groups, wherein the modified multifunctional groups include at least one of diacrylate double bonds, thiophene-sulfonic acid groups, and ether-carboxyl multi-branched chains.

[0013] In the solid-state lithium battery described above, the negative electrode comprises the following components and their contents:

[0014] 75-98% negative electrode active material, 0.2-3% conductive carbon, 0.3-4% binder, 1-15% lithium powder, 0.55-7% primary conductive polymer.

[0015] The solid-state lithium battery described above, wherein the lithium powder comprises a lithium metal core and a graphite layer coating at least a portion of the surface of the lithium metal core; and / or,

[0016] The negative electrode active material includes at least one of the following: mesophase carbon microspheres, natural graphite, artificial graphite, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, silicon-carbon composites, lithium metal, and lithium metal alloys; and / or,

[0017] The positive electrode sheet includes a positive electrode active material, which includes at least one of lithium cobalt oxide, lithium iron phosphate, nickel-cobalt-manganese ternary, lithium manganese iron phosphate, lithium manganese oxide, and lithium-rich manganese-based materials.

[0018] Secondly, this application provides a method for preparing a solid-state lithium battery, comprising the following steps:

[0019] The solid-state lithium battery is obtained by stacking and fixing a negative electrode sheet including the first conductive polymer, a solid electrolyte layer including the second conductive polymer, and a positive electrode sheet.

[0020] The solid electrolyte layer is located between the negative electrode and the positive electrode.

[0021] The preparation method described above further includes, before the fixation treatment, sequentially subjecting the laminated body after the lamination treatment to gel electrolyte injection treatment and heat curing treatment;

[0022] After processing, a first quasi-solid electrolyte layer containing a third conductive polymer is formed between the negative electrode and the solid electrolyte layer, and a second quasi-solid electrolyte layer containing a third conductive polymer is formed between the positive electrode and the solid electrolyte layer.

[0023] In the preparation method described above, the polymer monomers of the first conductive polymer, the second conductive polymer, the third conductive polymer, and the fourth conductive polymer are respectively selected from at least one of poly(ethylene glycol) methyl ether methacrylate, polyethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol dimethyl ether, 1,3-dioxane, and poly(ethylene glycol) methyl ether acrylate; and / or,

[0024] The polymer monomer is selected from at least one of the following: poly(ethylene glycol) methyl ether methacrylate grafted with modified polyfunctional groups, poly(ethylene glycol) diacrylate grafted with modified polyfunctional groups, poly(ethylene glycol) diacrylate grafted with modified polyfunctional groups, triethylene glycol dimethacrylate grafted with modified polyfunctional groups, triethylene glycol dimethyl ether grafted with modified polyfunctional groups, 1,3-dioxane, and poly(ethylene glycol) methyl ether acrylate grafted with modified polyfunctional groups.

[0025] In the preparation method described above, the injection coefficient of the gel electrolyte injection treatment is 3-6 g / Ah, and after injection, it is maintained at a pressure of 0.15-0.3 MPa for 5-20 min; and / or,

[0026] The heat curing process includes the following steps: first, curing at a temperature of 40-60℃ for 4-6 hours; then, curing at a temperature of 70-80℃ for 2-4 hours to obtain a solid-state lithium battery.

[0027] This application provides a solid-state lithium battery, which sequentially stacks a positive electrode, a solid electrolyte layer, and a negative electrode. A first conductive polymer is disposed in the negative electrode, and a second conductive polymer is disposed in the solid electrolyte layer. The first and second conductive polymers, through their elastically deformable three-dimensional cross-linked network structure, eliminate interfacial gaps and buffer stress at the solid-solid interface between the negative electrode and the solid electrolyte layer, thereby improving the interfacial contact state between the negative electrode and the solid electrolyte layer and significantly reducing the solid-solid interface impedance. Simultaneously, the high elastic modulus cross-linked electrolyte network effectively buffers the interfacial volume expansion generated during the negative electrode lithium replenishment process, significantly improving the electrode structure stability and ensuring the long-term cycle performance of the battery cell. This lithium battery can significantly reduce the solid-solid interface impedance, improve the continuity of ion transport channels and the structural stability at the interface, and simultaneously enhance the compatibility and structural stability of the two-phase interface between the negative electrode and the electrolyte. This helps to suppress interfacial side reactions and structural degradation under cycling and high-voltage conditions, thereby achieving stable operation over long cycles and a wide temperature range. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] Solid-state lithium battery technology belongs to the high-safety battery category within the field of electrochemical energy storage, and is widely used in new energy vehicles, energy storage power stations, and portable electronic devices with high reliability requirements. In practical applications, solid-state lithium batteries are typically composed of a positive electrode, a solid electrolyte layer, and a negative electrode stacked together, and rely on ion conduction between the electrodes and the electrolyte to achieve the charging and discharging process.

[0030] Current solid-state lithium batteries mostly employ a stacked structure of a solid electrolyte membrane and positive and negative electrodes, replacing the traditional liquid electrolyte with a solid medium to reduce the risks of leakage, combustion, and thermal runaway. During operation, lithium ions need to migrate continuously between the positive electrode, the solid electrolyte layer, and the negative electrode, and this migration efficiency is highly dependent on the consistency of the interlayer contact state and interface morphology. Although existing technologies have made improvements by increasing the density of the electrolyte membrane, optimizing electrode materials, and improving compaction processes, insufficient contact, residual local pores, and uneven interface adhesion between the solid electrolyte layer and the electrode sheets are still prone to occur, resulting in high contact resistance. Especially under cyclic charge-discharge and high-voltage conditions, the electrode structure undergoes volume changes, making it easier for stress concentration, microcrack propagation, and side reaction accumulation to occur at the interface, further leading to interface degradation, accelerated capacity decay, and even affecting the ion transport efficiency and output stability of the battery at low temperatures. Therefore, how to maintain the safety advantages of the solid-state system while further improving the interface consistency and long-term stability between the electrode and the electrolyte remains a key problem that current technologies struggle to solve.

[0031] In view of this, facing the problems of high interfacial impedance, insufficient interfacial stability during cycling, and limited performance over a wide temperature range in solid-state lithium batteries, providing a structural solution that can improve the synergistic working between the electrode and the solid electrolyte layer has become an urgent technical direction. To achieve this, the relevant technical solution adopts a battery structure in which a positive electrode, a solid electrolyte layer, and a negative electrode are stacked sequentially, with a first conductive polymer introduced into the negative electrode and a second conductive polymer introduced into the solid electrolyte layer. By simultaneously incorporating conductive polymers in the relevant layers at key interfaces, a more continuous conductive and contact relationship can be formed between the electrode side and the electrolyte side, thereby improving the interlayer matching state overall, reducing interfacial impedance, and enhancing the battery's stable operation under cycling and different temperature conditions, providing a structural foundation for subsequent long-cycle and wide-temperature-range applications.

[0032] Based on this, the first aspect of the present invention provides a solid-state lithium battery, comprising a positive electrode, a solid electrolyte membrane, and a negative electrode stacked sequentially, wherein the negative electrode comprises a first conductive polymer, the solid electrolyte membrane comprises a solid electrolyte layer, and the solid electrolyte layer comprises a second conductive polymer.

[0033] Specifically, the solid-state lithium battery of the present invention can be constructed as a stacked all-solid-state or quasi-solid-state electrochemical energy storage unit, wherein the positive electrode, the solid electrolyte layer and the negative electrode are arranged sequentially along the thickness direction, and are formed into an integral structure that is bonded to each other by stacking, laminating, rolling or hot pressing.

[0034] A first conductive polymer is disposed in the negative electrode sheet, and a second conductive polymer is disposed in the solid electrolyte layer. The first and second conductive polymers are located in the interface-related regions close to the negative electrode sheet and the solid electrolyte layer, respectively. This allows interface regulation to be improved through a two-sided synergistic approach, rather than being limited to a single level. The first and second conductive polymers, through their elastically deformable three-dimensional cross-linked network structure, eliminate interfacial gaps and buffer stress at the solid-solid interface between the negative electrode sheet and the solid electrolyte layer, thereby improving the interfacial contact state and significantly reducing the solid-solid interface impedance. At the same time, the cross-linked electrolyte network with high elastic modulus can effectively buffer the interfacial volume expansion generated during the lithium replenishment process of the negative electrode, significantly improving the stability of the electrode structure and ensuring the long-term cycle performance of the cell. The above-mentioned lithium battery can not only significantly reduce the solid-solid interface impedance, but also improve the continuity of ion transport channels and the structural stability of the interface, and simultaneously enhance the compatibility and structural stability of the two-phase interface between the negative electrode and the electrolyte. This helps to suppress interfacial side reactions and structural degradation under cycling and high-voltage conditions, so as to achieve stable operation under long-cycle and wide-temperature range conditions.

[0035] Furthermore, to compensate for the active lithium consumed during the first charge and discharge of the battery, lithium powder is usually added to the negative electrode for lithium replenishment. However, adding lithium powder further increases the volume of the negative electrode active layer in the early stages of battery cycling, thus exacerbating the contact resistance at the solid-solid interface. This invention, by introducing a first conductive polymer into the negative electrode active layer, can effectively improve the contact failure and overall cell impedance growth problems caused by the volume change of lithium powder in the early stages of cycling.

[0036] Furthermore, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on the surface of the negative electrode current collector;

[0037] The negative electrode current collector includes at least one of copper foil, nickel foam, and copper foam;

[0038] The negative electrode active layer includes at least one of a negative electrode active material, a conductive agent, a binder, lithium powder, and a first conductive polymer;

[0039] The negative electrode active material includes at least one of the following: mesophase carbon microspheres, natural graphite, artificial graphite, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, silicon-carbon composite, lithium metal, and lithium metal alloys.

[0040] Conductive agents include at least one of conductive carbon and carbon nanotubes;

[0041] The adhesive includes at least one of PEO-based polymers, polyethylene glycol diacrylate, and polytetrafluoroethylene;

[0042] The lithium powder is graphite-coated passivated lithium powder.

[0043] Furthermore, the first conductive polymer can be dispersed inside the negative electrode active layer, or it can be coated on the surface of the negative electrode active material particles, or it can form a composite network together with the conductive agent and the binder.

[0044] Specifically, the first conductive polymer is formed from polymer monomers through in-situ polymerization, photocuring, thermocuring, or chemical cross-linking.

[0045] Specifically, the polymer monomers of the second conductive polymer include at least one of poly(ethylene glycol) methyl ether methacrylate, polyethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol dimethyl ether, 1,3-dioxopentane, poly(ethylene glycol) methyl ether acrylate, polyethylene dioxythiophene, polystyrene sulfonic acid, polythiophene, and polyanionic polymers.

[0046] In one possible embodiment, polymer monomers and an initiation system can be introduced into the negative electrode slurry. After the slurry is coated and the solvent has evaporated, the monomers are cured in situ at room temperature or under heating conditions, thereby forming a flexible conductive polymer network between the negative electrode active material particles and between the particles and the current collector. This network can improve the overall electron transport continuity of the negative electrode sheet. On the other hand, due to the flexibility of the polymer chain segments, it can buffer particle deformation during negative electrode charging and discharging, especially when silicon-based negative electrodes undergo volume expansion and contraction, reducing the risk of particle cracking, conductive network breakage, and interface detachment.

[0047] Furthermore, the first conductive polymer can also be prepolymerized and coated onto the surface of the negative electrode active material or passivated lithium powder before being mixed with other components to form a sheet, thereby creating a coating layer on the surface of the negative electrode active particles that has both conductivity and adhesion. Through this coating layer, the local roughness and micropores on the negative electrode surface are mitigated, and the contact stress distribution tends to be more uniform, making it easier for the negative electrode sheet to form an effective bond with the adjacent solid electrolyte layer and reducing local high-resistance areas caused by contact discontinuities.

[0048] Furthermore, the negative electrode active layer comprises the following components and their mass percentages (the sum of the contents of each component is 100%):

[0049] 75-98% negative electrode active material, 0.2-3% conductive agent, 0.3-4% binder, 1-15% lithium powder, 0.55-7% primary conductive polymer.

[0050] Specifically, the mass percentage of the negative electrode active material is 80%, 85%, 90%, 95%, 98%, or any two of these components; the mass percentage of the conductive agent is 0.2%, 0.5%, 1%, 2%, 3%, or any two of these components; the mass percentage of the binder is 0.3%, 1%, 2%, 3%, 4%, or any two of these components; the mass percentage of the lithium powder is 1%, 3%, 6%, 8%, 10%, 13%, 15%, or any two of these components; and the mass percentage of the first conductive polymer is 0.55%, 1%, 2%, 5%, 7%, or any two of these components.

[0051] The negative electrode active layer is synergistically composed of the above components. 80-98% of the negative electrode active material provides the main lithium storage framework and determines the capacity basis of the electrode. 0.2-3% of conductive carbon establishes continuous electron transport pathways between active particles, and 0.3-4% of binder enhances interparticle bonding and the adhesion stability between the electrode and the current collector. By controlling the lithium powder content to 1-15%, lithium loss can be compensated for in the first and subsequent cycles, reducing irreversible capacity loss and contributing to improved initial efficiency and cycle life. The introduction of the first conductive polymer at a content of 0.55-7% into the negative electrode improves the contact uniformity between the active material, conductive agent, and lithium powder, and provides buffering and stress release during charge / discharge volume changes, thereby suppressing interface cracking and localized debonding.

[0052] By limiting the components to the above range, the negative electrode can achieve a balance between capacity retention, initial efficiency, mechanical stability and interface matching, thereby reducing the contact resistance of the negative electrode / solid electrolyte interface in solid-state lithium batteries and improving cycle stability and wide-temperature-range operational reliability.

[0053] Furthermore, the solid electrolyte in the solid electrolyte layer includes at least one of garnet-type oxides, NASICON-type oxides, perovskite-type oxides, sulfide glass ceramics, and electrolyte halides.

[0054] Furthermore, the second conductive polymer in the solid electrolyte layer can be distributed throughout the entire solid electrolyte layer, or it can be mainly distributed on the side near the negative electrode, the side near the positive electrode, or form a gradient distribution along the thickness direction of the solid electrolyte layer.

[0055] Furthermore, the second conductive polymer is formed from polymer monomers through in-situ polymerization, photocuring, thermocuring, or chemical cross-linking.

[0056] Because the second conductive polymer can form a flexible filling phase and a binder phase between solid electrolyte particles, the pores, cracks, and local voids caused by particle accumulation can be filled, improving the density of the electrolyte layer and consequently enhancing interfacial wettability and adhesion. When the second conductive polymer is enriched near the negative electrode side, it can more effectively match the dimensional changes of the negative electrode due to cycling and reduce the tendency for solid-solid interface separation. When it forms a gradient distribution along the thickness direction, it can take into account the different requirements of mechanical modulus, adhesion, and ion transport in different interfacial regions.

[0057] Furthermore, the solid electrolyte membrane also includes a base membrane, with a solid electrolyte layer coated and fixed on the side of the base membrane away from the negative electrode.

[0058] Furthermore, the base membrane is at least one of polypropylene (PP), polyethylene (PE), polypropylene / polyethylene double-layer composite membrane (PP / PE), polypropylene, polyethylene, and polypropylene triple-layer composite membrane (PP / PE / PP), and cellulose nonwoven membrane. Furthermore, a first quasi-solid electrolyte layer is provided between the solid electrolyte layer and the negative electrode sheet, and the first quasi-solid electrolyte layer includes a third conductive polymer.

[0059] Furthermore, the third conductive polymer is formed from polymer monomers through in-situ polymerization, photocuring, thermocuring, or chemical cross-linking.

[0060] The first quasi-solid electrolyte layer is disposed between the solid electrolyte layer and the negative electrode, serving as a buffer layer for the transition from solid to quasi-solid, and improving potential issues such as point contact, residual pores, and uneven adhesion between the two. The third conductive polymer can be a polymer system with ion conductivity and a certain degree of flexibility. It can form continuous conductive channels within the layer and fill the microscopic unevenness of the interface through its deformability, thereby improving interface wettability and contact area. The addition of the third conductive polymer further enhances the continuity and flexibility of the first quasi-solid electrolyte layer, allowing ions to migrate more smoothly between the solid electrolyte layer, the first quasi-solid electrolyte layer, and the negative electrode, thus ensuring the battery's output consistency and capacity retention under long-cycle and wide-temperature conditions.

[0061] Furthermore, the positive electrode includes a fourth conductive polymer.

[0062] Furthermore, the positive electrode includes a positive current collector and a positive active layer disposed on the surface of the positive current collector, and a fourth conductive polymer is contained within the positive active layer.

[0063] Specifically, the positive current collector is an aluminum foil, an aluminum alloy foil, or a metal foil with a conductive coating on its surface;

[0064] The positive electrode active layer includes at least one of the following: positive electrode active material, conductive agent, binder, lithium salt, fourth conductive polymer, and solid electrolyte;

[0065] The positive electrode active material includes at least one of lithium cobalt oxide, lithium iron phosphate, nickel-cobalt-manganese ternary, lithium manganese iron phosphate, lithium manganese oxide, and lithium-rich manganese-based materials.

[0066] Conductive agents include at least one of conductive carbon and carbon nanotubes;

[0067] The adhesive includes at least one of PEO-based polymers, polyethylene glycol diacrylate, and polytetrafluoroethylene;

[0068] The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide.

[0069] Furthermore, the fourth conductive polymer is formed from polymer monomers through in-situ polymerization, photocuring, thermocuring, or chemical cross-linking.

[0070] The fourth conductive polymer serves as a flexible conductive and binding phase to enhance electron conduction continuity and improve interparticle contact stability without significantly sacrificing the cathode compaction density. Introducing the fourth conductive polymer into the cathode sheet makes electron transport within the cathode more uniform and simultaneously strengthens the compatibility and structural stability of the cathode-electrolyte interface, thereby improving structural integrity and capacity retention under high-rate and high-voltage cycling.

[0071] Furthermore, a second quasi-solid electrolyte layer is disposed between the positive electrode and the solid electrolyte layer, and a third conductive polymer is introduced therein.

[0072] The second quasi-solid electrolyte layer can construct a transition buffer interface on the positive electrode side. This layer combines wetting, interstitial filling, and ion conduction functions, achieving continuous adhesion between the positive electrode surface and the solid electrolyte, and reducing the contact gap between the hard and brittle solid electrolyte layer and the porous positive electrode. The third conductive polymer can form a composite network with lithium salt, solvent, or inorganic electrolyte particles, providing ions with a lower impedance migration channel in the second quasi-solid electrolyte layer, while absorbing interfacial stress and suppressing debonding and microcrack propagation during cycling. Through this quasi-solid transition structure, the interface roughness on the positive electrode side is effectively smoothed, and the charge transfer impedance is reduced, which is particularly beneficial for suppressing interfacial side reactions under high-voltage conditions.

[0073] By introducing a first conductive polymer into the negative electrode, a second conductive polymer into the solid electrolyte layer, a fourth conductive polymer into the positive electrode, and a third conductive polymer into the first and second quasi-solid electrolyte layers, a multi-layer integrated structure of "positive electrode active layer / second quasi-solid electrolyte layer / solid electrolyte layer / first quasi-solid electrolyte layer / negative electrode active layer" is constructed. In-situ crosslinking of each component with polymer monomers is achieved in each layer, thereby forming a three-dimensional interpenetrating polymer network that runs through the entire cell. This can significantly improve the interfacial contact state between solid and solid interfaces in all-solid batteries, reduce interfacial impedance, and enhance the continuity and stability of ion transport channels at the interface. This helps to suppress interfacial side reactions and structural degradation under cycling and high-voltage conditions in solid-state lithium batteries, enabling stable operation of solid-state lithium batteries under long-cycle and wide-temperature range conditions.

[0074] Furthermore, at least one of the first conductive polymer, the second conductive polymer, the third conductive polymer, and the fourth conductive polymer is grafted with modified multifunctional groups, which include at least one of the following: diacrylate double bond, thiophene-sulfonic acid group, ether-carboxyl multi-branched chain.

[0075] By suspending the aforementioned modified multifunctional groups onto the first, second, third, or fourth conductive polymer, their compatibility with inorganic particles, binders, electrode active materials, and solid electrolytes can be improved, further reducing interfacial porosity and enhancing interlayer adhesion consistency. Under heating conditions, the conductive polymers containing modified multifunctional groups achieve covalent cross-linking through free radical reactions triggered by initiators. Through the synergistic effect of functional groups, a three-dimensional cross-linked quasi-solid electrolyte network with high mechanical strength, high ionic conductivity, and uniform dispersion of the conductive phase is constructed throughout the entire battery cell.

[0076] Furthermore, the diacrylate double bond is grafted onto the α-methyl site of the acrylate main chain and the terminal hydroxyl site of the polyether side chain, as well as the secondary carbon site of the polyether ring carbon, with a molar grafting degree of 8-25%.

[0077] Furthermore, the thiophene-sulfonic acid group is grafted at the β-position of the thiophene ring, the para-position of the styrene sulfonic acid benzene ring, and the ortho-methylene site of the polyether side chain ether bond, with a molar grafting degree of 5-20%.

[0078] Furthermore, ether-carboxyl groups are multi-branched at the active hydroxyl sites at the end of the conductive polymer backbone and at the methylene sites of the side chains, with a molar grafting degree of 6-22%. A second aspect of this invention provides a method for preparing a solid-state lithium battery, comprising the following steps:

[0079] A solid-state lithium battery is obtained by stacking and fixing a negative electrode sheet including a first conductive polymer, a solid electrolyte layer including a second conductive polymer, and a positive electrode sheet.

[0080] The solid electrolyte layer is located between the negative electrode and the positive electrode.

[0081] Specifically, the preparation method of the negative electrode includes the following steps:

[0082] A negative electrode slurry is prepared, comprising main raw materials and solvent. The main raw materials (by mass percentage) include 75-98% negative electrode active material, 0.2-3% conductive agent, 0.3-4% binder, 1-15% lithium powder, 0.5-5% polymer monomer, and 0.05-2% initiator. The solid content of the negative electrode slurry is 40-60%. The prepared positive electrode slurry is coated onto the copper foil of the negative electrode sheet and cured at room temperature during the coating process to obtain the negative electrode sheet.

[0083] Specifically, the preparation method of the positive electrode includes the following steps:

[0084] The positive electrode slurry is prepared by means of main raw materials and solvent. The main raw materials (by mass percentage) include 90-98% positive electrode active material, 0.5-5% conductive agent, 0.8-5% binder, 0.5-5% lithium salt, 0.5-5% polymer monomer, 0.05-2% initiator, and 0.5-2.5% solid electrolyte. The solid content of the positive electrode slurry is 50-70%. The prepared positive electrode slurry is coated on the copper foil of the positive electrode sheet and cured at room temperature during the coating process to obtain the positive electrode sheet.

[0085] First, a negative electrode containing a first conductive polymer, a solid electrolyte layer containing a second conductive polymer, and a positive electrode are prepared separately. The negative electrode can be a sheet-like structure coated on a metal current collector, the solid electrolyte layer can be a self-supporting film, a composite film, or a supported film, and the positive electrode can be a sheet-like structure coated on another metal current collector. Then, the negative electrode, solid electrolyte layer, and positive electrode are stacked and aligned in that order, ensuring the solid electrolyte layer is completely sandwiched between the negative and positive electrodes. Fixation is then achieved through methods such as rolling, hot pressing, pressure bonding, local bonding, or in-situ curing to form a solid-state lithium battery structure with continuous interfaces and stable positions. The stacking process is typically carried out in a clean, low-humidity environment to reduce the impact of moisture on the solid electrolyte and electrode interfaces. During the fixation process, the temperature and pressure can be set according to the adhesion characteristics of the selected conductive polymer to achieve sufficient contact between the layers without damaging the material structure.

[0086] The first conductive polymer in the negative electrode improves the electron pathway within the active layer, enhances the flexibility of the negative electrode, and improves interfacial wettability. The second conductive polymer in the solid electrolyte layer maintains ion conduction channels while improving film formation, interfacial adhesion, and structural integrity, thus ensuring the stability of the stacked battery under mechanical pressing and cyclic stress. Based on these settings, the stacking sequence and fixing method can be coordinated to ensure that the solid electrolyte layer forms a continuous and uniform isolation and conduction interface between the negative and positive electrodes. The above method is concise, highly reproducible, and can prepare solid-state lithium batteries with reduced interfacial contact impedance between the electrode layer and the solid electrolyte layer at a lower cost.

[0087] Furthermore, prior to the fixation process, the laminated body after the lamination process is subjected to gel electrolyte injection and heat curing processes in sequence.

[0088] After processing, a first quasi-solid electrolyte layer containing a third conductive polymer is formed between the negative electrode and the solid electrolyte layer, and a second quasi-solid electrolyte layer containing a third conductive polymer is formed between the positive electrode and the solid electrolyte layer.

[0089] By forming an effective first quasi-solid electrolyte layer and a second quasi-solid electrolyte layer between the positive electrode, the solid electrolyte layer, and the negative electrode with a gel electrolyte, the liquid content of the battery cell can be reduced while achieving uniform coating of each layer of materials by the gel electrolyte. Furthermore, by integrating and solidifying the positive / negative electrode active layers, the solid electrolyte layer, and the conductive polymer in the gel electrolyte to form a flexible interface bonding layer, the interface stability can be further improved, and good electrochemical adaptability can be exhibited even under high voltage conditions.

[0090] Furthermore, the gel electrolyte includes polymer monomers, initiators, and an electrolyte;

[0091] The polymer monomers are in the range of 1%, 2%, 3%, or any combination thereof by mass percentage;

[0092] The initiator has a mass percentage of 0.5%, 1%, 2%, or any combination thereof, and the initiator is azobisisobutyronitrile;

[0093] The electrolyte has a mass percentage of 96%, 97%, 98%, or any combination thereof, and the electrolyte is a commercially available conventional electrolyte.

[0094] Furthermore, the injection coefficient for the gel electrolyte injection treatment is 3 g / Ah, 4 g / Ah, 5 g / Ah, 6 g / Ah, or any combination thereof; after injection, it is maintained under a pressure of 0.15-0.3 MPa for 5-20 min, specifically 5 min, 10 min, 15 min, 20 min, or any combination thereof.

[0095] The electrolyte injection coefficient is controlled at 3-6 g / Ah to ensure that the gel electrolyte fully wets the interfaces between the positive electrode, the solid electrolyte layer, and the negative electrode, while avoiding excessive liquid intake that could lead to increased residual free phase, intensified interfacial side reactions, or uneven subsequent curing shrinkage. During injection, quantitative dripping, vacuum-assisted injection, or immersion injection methods can be used to ensure uniform liquid penetration along the pores and interfaces of the laminated cells. After injection, the cells are held under pressure applied by a fixture, mold, or roller press for 5-20 minutes to further bond the layers and eliminate interfacial air bubbles, thereby reducing contact resistance and improving the uniformity of electrolyte penetration.

[0096] Furthermore, the heat curing process includes the following steps: first, curing at a temperature of 40-60℃ for 4-6 hours; then, curing at a temperature of 70-80℃ for 2-4 hours to obtain a solid-state lithium battery.

[0097] The process involves segmented heating and curing. First, the temperature is maintained at 40-60℃ for 4-6 hours, preferably at 45-55℃ for 4.5-5.5 hours, to slowly initiate the polymer monomer reaction and complete the initial crosslinking, avoiding localized excessively rapid heat release that could lead to phase separation. Then, the temperature is maintained at 70-80℃ for 2-4 hours, preferably at 72-78℃ for 2.5-3.5 hours, to further promote the conversion of residual polymer monomers and network densification.

[0098] Furthermore, the polymer monomers of the first conductive polymer, the second conductive polymer, the third conductive polymer, and the fourth conductive polymer are each selected from at least one of poly(ethylene glycol) methyl ether methacrylate, polyethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol dimethyl ether, 1,3-dioxane, and poly(ethylene glycol) methyl ether acrylate.

[0099] Polymer monomers are used as precursors for in-situ interfacial polymerization or film formation. They can be added alone or in combination of two or more to control crosslinking density, flexibility, and ion conductivity. In this invention, they are added to a mixture containing lithium salt, solvent, initiator, and necessary filler. The mixture is first stirred until homogeneous under an inert atmosphere, and then introduced into the negative electrode, solid electrolyte layer, positive electrode, or quasi-solid electrolyte layer by coating, impregnation, or injection. Subsequently, polymerization, crosslinking, or ring-opening reactions occur under thermal, light, or chemical initiation conditions, forming a continuous conductive polymer network in situ between the layers.

[0100] Furthermore, the polymer monomer is selected from at least one of the following: poly(ethylene glycol) methyl ether methacrylate grafted with modified polyfunctional groups, poly(ethylene glycol) diacrylate grafted with modified polyfunctional groups, poly(ethylene glycol) diacrylate grafted with modified polyfunctional groups, triethylene glycol dimethacrylate grafted with modified polyfunctional groups, triethylene glycol dimethyl ether grafted with modified polyfunctional groups, 1,3-dioxopentane, and poly(ethylene glycol) methyl ether acrylate grafted with modified polyfunctional groups.

[0101] The present invention will be further described below through specific embodiments.

[0102] Example 1:

[0103] The solid-state lithium battery preparation method of this embodiment includes the following steps:

[0104] Positive electrode preparation: A positive electrode slurry is prepared, comprising main raw materials and a solvent. The main raw materials (by mass percentage) include 94.4% wt lithium iron phosphate, 1.6% wt conductive carbon, 1.2% wt PEO-based polymer, 2% wt solid electrolyte, 0.7% wt polyethylene glycol diacrylate, and 0.1% wt azobisisobutyronitrile. The solid content of the positive electrode slurry is 60%. The prepared positive electrode slurry is coated onto aluminum foil for the positive electrode sheet and cured at room temperature during the coating process to obtain the positive electrode sheet.

[0105] Negative electrode preparation: A negative electrode slurry is prepared, comprising main raw materials and a solvent. The main raw materials include 82.1%wt graphite active material, 12%wt graphite-coated passivated lithium powder, 0.8%wt conductive carbon, 3%wt PEO-based polymer, 2%wt polyethylene glycol diacrylate, and 0.1%wt azobisisobutyronitrile. The solid content of the negative electrode slurry is 60%. The prepared negative electrode slurry is coated onto the copper foil of the negative electrode sheet and cured at room temperature during the coating process to obtain the negative electrode sheet.

[0106] Solid-state lithium battery manufacturing:

[0107] The prepared positive and negative electrode sheets were stacked with a solid electrolyte membrane to obtain a laminate, with the solid electrolyte membrane located between the positive and negative electrode sheets. The solid electrolyte membrane, model LG(9+3)A01-02, was purchased from Langgu New Energy Technology Co., Ltd.

[0108] The laminated bodies after the lamination process were sequentially subjected to gel electrolyte injection treatment: the gel electrolyte consisted of 2 wt% PEGMA, 1 wt% AIBN, and 97 wt% commercially available conventional electrolyte. The injection coefficient for the gel electrolyte injection treatment was 3 g / Ah, and after injection, the system was maintained at a pressure of 0.2 MPa for 10 min.

[0109] Then, a heat curing process is performed: first, it is cured at 50°C for 5 hours; then, it is cured at 70°C for 3 hours to obtain a solid-state lithium battery.

[0110] Example 2:

[0111] The solid-state lithium battery preparation method of this embodiment includes the following steps:

[0112] Positive electrode preparation: A positive electrode slurry is prepared, comprising main raw materials and a solvent. The main raw materials include 95.2% wt lithium iron phosphate, 1.6% wt conductive carbon, 1.2% wt PEO-based polymer, and 2% wt solid electrolyte. The solid content of the positive electrode slurry is 60%. The prepared positive electrode slurry is coated onto aluminum foil for the positive electrode sheet and cured during the coating process to obtain the positive electrode sheet.

[0113] Negative electrode preparation: A negative electrode slurry is prepared, comprising main raw materials and a solvent. The main raw materials include 82.1%wt graphite active material, 12%wt graphite-coated passivated lithium powder, 0.8%wt conductive carbon, 3%wt PEO-based polymer, 2%wt polyethylene glycol diacrylate, and 0.1%wt azobisisobutyronitrile. The solid content of the negative electrode slurry is 60%. The prepared negative electrode slurry is coated onto the copper foil of the negative electrode sheet and cured during the coating process to obtain the negative electrode sheet.

[0114] The solid electrolyte membrane (model LG(9+3)A01-02, purchased from Langgu New Energy Technology Co., Ltd.) and the above-prepared positive and negative electrode sheets are laminated to form an integral structure that is bonded together, thus obtaining a laminate.

[0115] The laminated bodies after the stacking process were subjected to conventional electrolyte injection treatment. The electrolyte injection coefficient was 5 g / Ah. After the injection was completed, the body was kept under a pressure of 0.2 MPa for 10 min.

[0116] Then, a heat curing process is performed: first, it is cured at 50°C for 5 hours; then, it is cured at 70°C for 3 hours to obtain a solid-state lithium battery.

[0117] Example 3:

[0118] The method for preparing the solid-state lithium battery in this embodiment differs from that in Example 1 in that the gel electrolyte is replaced with a conventional electrolyte.

[0119] Example 4:

[0120] The method for preparing the solid-state lithium battery in this embodiment differs from that in Example 1 in that the main raw materials of the negative electrode slurry include 77.2%wt of graphite active material, 12%wt of graphite-coated passivated lithium powder, 0.8%wt of conductive carbon, 3%wt of PEO-based polymer, 0.5%wt of polyethylene glycol diacrylate, and 0.05%wt of azobisisobutyronitrile.

[0121] Example 5:

[0122] The method for preparing the solid-state lithium battery in this embodiment differs from that in Example 1 in that the main raw materials of the negative electrode slurry include 82.1%wt of graphite active material, 12%wt of graphite-coated passivated lithium powder, 0.8%wt of conductive carbon, 3%wt of PEO-based polymer, 5%wt of polyethylene glycol diacrylate, and 2%wt of azobisisobutyronitrile.

[0123] Example 6:

[0124] The method for preparing the solid-state lithium battery in this embodiment differs from that in Example 1 in that the polymer monomer is polyethylene glycol diacrylate grafted with modified multifunctional groups, wherein the modified multifunctional groups are diacrylate double bonds, the grafting sites of the diacrylate double bonds are limited to the methylene sites of the side chains of the ethylene glycol repeating units of the polyethylene glycol diacrylate molecular chain and the carbonyl adjacent carbon sites of the acrylate end groups, and the molar grafting degree of the diacrylate double bonds is 13%.

[0125] Example 7:

[0126] The method for preparing the solid-state lithium battery in this embodiment differs from that in Embodiment 1 in that lithium iron phosphate in the positive electrode slurry is replaced with lithium manganese iron phosphate.

[0127] Comparative Example 1:

[0128] The method for preparing the solid-state lithium battery in this embodiment differs from that in Example 1 in that:

[0129] The main raw materials of the negative electrode slurry (by mass percentage) include 84.2%wt of graphite active material, 12%wt of graphite-coated passivated lithium powder, 0.8%wt of conductive carbon, and 3%wt of PEO-based polymer.

[0130] Comparative Example 2:

[0131] The difference between the solid-state lithium battery preparation method in this embodiment and that in Embodiment 1 is that the solid electrolyte membrane is replaced with a PE membrane.

[0132] Experimental example:

[0133] The quasi-solid-state lithium-ion batteries prepared through the above examples and comparative examples were subjected to performance tests. The test methods are as follows (the voltages of Examples 1-6 and Comparative Examples 1-2 are as shown in the test methods below, and the voltage of Example 7 is uniformly adjusted to 2.7-4.25V in the test methods below). The test results are shown in Table 1 below.

[0134] (1) 5% SOC DC internal resistance: After the battery capacity is divided, discharge it to 2.5V with a constant current of 2P (1P=320w) and let it stand for 30min; charge it with a constant power of 1P for 6min and let it stand for 60min, and record the internal resistance and voltage.

[0135] (2) Room temperature rate performance test: Each battery was left to stand at (25±2℃) for 4 hours. After initial charge and discharge, the room temperature rate performance test was started. The test steps were as follows: charge at 1P constant power to the battery charging cutoff condition and let stand for 30 minutes; discharge at 1P constant current to 2.5V and let stand for 30 minutes; charge at 2P constant power to the battery charging cutoff condition and let stand for 30 minutes; charge at 1P constant power to the battery charging cutoff condition and let stand for 30 minutes; discharge at 2P constant current to 2.5V and let stand for 30 minutes; discharge at 1P constant current to 2.5V and let stand for 30 minutes. Record the energy, time, voltage, and temperature information. Record the 2P discharge energy / 1P discharge energy as the discharge energy retention rate.

[0136] (3) Low-temperature performance test: Each battery was left to stand at (5±2)℃ for 20 hours before a charge-discharge capacity test was conducted. The test conditions were as follows: at (5±2)℃, the battery was charged at a constant power of 1P until the battery charging cutoff condition was met, left to stand for 30 minutes, and the time, voltage, temperature, and charging energy were recorded; at (5±2)℃, the battery was discharged at a constant power of 1P until the battery discharging cutoff condition was met, left to stand for 30 minutes, and the power, time, voltage, temperature, and discharging energy were recorded. The ratio of discharging energy to charging energy is the energy efficiency at 5℃.

[0137] (4) Cyclic performance test: The battery prepared above was subjected to a cyclic performance test at a high temperature of 45°C. The test process is as follows: 1P constant current charging to the battery charging cutoff condition, rest for 30 min, 1P constant current discharge to 2.5V, rest for 30 min, and so on for 600 cycles to obtain the energy retention rate.

[0138] Table 1:

[0139]

[0140] First, as shown in Table 1, the solid-state lithium battery prepared in Example 1 has excellent 5% SOC DC internal resistance, discharge energy retention rate, low-temperature energy efficiency, and high-temperature 600-cycle energy retention rate. This indicates that the solid-state lithium battery prepared in Example 1 can reduce solid-solid interface impedance and improve the transmission continuity and structural stability at the interface, thereby helping to suppress interface side reactions and structural degradation under cycling conditions, so as to achieve stable operation under long cycling and wide temperature range.

[0141] Compared to Example 1, Comparative Example 1 did not introduce a conductive polymer into the negative electrode. As shown in Table 1, Comparative Example 1 has a lower initial internal resistance than Example 1, and its short-term rate performance is not significantly different from Example 1. However, due to the lack of a complete cross-linked gel network and the inability to effectively suppress the volume expansion and gas generation problems caused by the negative electrode lithium replenishment material, the low-temperature energy efficiency and 600-cycle energy retention rate of Comparative Example 1 are significantly lower than those of Example 1. This indicates that Comparative Example 1 differs significantly from Example 1 in low-temperature discharge performance, especially in long-term high-temperature cycling. The above demonstrates that, compared to introducing conductive polymers only into the positive electrode and solid electrolyte membrane, introducing conductive polymers into the negative electrode to form a multilayer integrated structure, with in-situ cross-linking of polymer monomers in the positive and negative electrodes and the solid electrolyte membrane to form a three-dimensional interpenetrating polymer network throughout the entire cell, can help suppress interfacial side reactions and structural degradation during cycling, thereby achieving stable operation over long cycles and a wide temperature range.

[0142] Compared to Example 1, Example 2 did not introduce a conductive polymer into the positive electrode, nor did it introduce the first and second quasi-solid electrolyte layers into the solid-state lithium battery. Example 3 did not introduce the first and second quasi-solid electrolyte layers into the solid-state lithium battery. As shown in Table 1, in terms of rate discharge performance, Example 1 achieved a 99.54% energy retention rate for 2P / 1P discharge, a significant improvement compared to Examples 2-3, effectively suppressing concentration polarization under high current. In terms of low-temperature discharge performance, the 5℃ energy efficiency of the Example 1 cell reached 95.03%, a significant improvement compared to Examples 2-3, significantly mitigating the problems of electrolyte viscosity increase and interface impedance degradation at low temperatures. In terms of high-temperature cycling performance, the 600-cycle energy retention rate of the Example 1 cell was significantly improved compared to Examples 2-3. The integrated cross-linked gel network construction effectively suppressed electrolyte decomposition, side reaction gas generation, and electrode volume expansion, improving long cycle life. The above indicates… Adding conductive polymer monomers to the positive electrode side and solidifying them in situ with the injected gel electrolyte forms an integrated cross-linked gel network. Compared with the solution of adding conductive polymers only to the negative electrode or only to the electrode and solid electrolyte membrane, although the initial performance is slightly affected by the cross-linked polymer network, which slightly increases the ion transport path length and the lower injection coefficient, resulting in slightly higher internal resistance, it does not affect the use of the battery. Instead, it brings about comprehensive optimization of rate, low temperature and cycle performance.

[0143] Compared to Example 1, the content of polymer monomers and initiators in Example 4 is the minimum value within the range set in this application, while the content of polymer monomers and initiators in Example 5 is the maximum value within the range set in this application. As shown in Table 1, the internal resistance of Example 4 is higher than that of Example 1, and the discharge energy retention rate, low-temperature energy efficiency, and high-temperature 600-cycle energy retention rate are all lower than those of Example 1. This indicates that when the polymer content is low, the cross-linking network is not complete enough, resulting in limited improvement in rate performance, low-temperature performance, and cycle performance. The low-temperature energy efficiency of Example 5 is higher than that of Example 1, but the discharge energy retention rate and high-temperature 600-cycle energy retention rate are slightly lower than those of Example 1. This indicates that when the polymer content is high, although it can improve the electrolyte retention, excessively high cross-linking density will significantly increase ion transport resistance, leading to increased internal resistance and decreased rate performance. Furthermore, excessive polymer can easily trigger side reactions, which in turn reduces the cycle stability of the battery cell. Therefore, the content of polymer monomers and initiators within the range set in this application can help suppress interfacial side reactions and structural degradation under cycling, thereby achieving stable operation over long cycles and a wide temperature range.

[0144] Compared to Example 1, the polymer monomer in Example 6 is polyethylene glycol diacrylate grafted with diacrylate double bonds. As shown in Table 1, the internal resistance of Example 6 is comparable to that of Example 1, while the discharge energy retention rate, low-temperature energy efficiency, and high-temperature 600-cycle energy retention rate are all superior to those of Example 1. This indicates that using modified polyethylene glycol diacrylate grafted with diacrylate double bonds, with defined grafting sites and molar grafting degree, can further enhance the stability of the polymer crosslinking network structure, improve the electrolyte-electrode interface affinity, and improve the lithium-ion conductivity of the system while maintaining a basically unchanged battery internal resistance and no performance degradation. The diacrylate double bonds grafted onto the polymer monomer can synergistically interact with the ether bonds in the molecular chain, effectively reducing the electrolyte freezing point and low-temperature viscosity, and optimizing lithium-ion transport kinetics at low temperatures. Simultaneously, the additional diacrylate double bonds increase the crosslinking site density of the system, enhance the thermal stability of the polymer crosslinking network, effectively suppress electrolyte decomposition and interfacial side reactions under high-temperature conditions, and ultimately achieve a simultaneous and significant improvement in the battery's low-temperature discharge performance and high-temperature long-cycle performance.

[0145] Compared to Example 1, Example 7 replaces the positive electrode active material with lithium manganese iron phosphate (LMFP). As shown in Table 1, the low-temperature performance of Example 7 is basically the same as that of Example 1. Other performance indicators show slight changes due to the intrinsic physicochemical properties of the materials: Due to the slightly lower intrinsic electronic / ionic conductivity of LMFP, the internal resistance of the cell in Example 7 increases slightly, and the rate discharge energy retention rate decreases slightly. Simultaneously, because LMFP is prone to manganese ion dissolution under high-temperature conditions, the high-temperature cycle stability of Example 7 is slightly lower than that of Example 1, but the test results are only slightly different from those of Example 1 and are generally better than Comparative Examples 1-2. The above results indicate that the polymeric crosslinking network formed by the present invention has good versatility for different phosphate-based positive electrode materials, can adapt to the usage requirements of different positive electrode material systems, can operate stably under high-voltage conditions, and plays a certain role in inhibiting side reactions and structural degradation at the electrode interface.

[0146] Compared to Example 1, Comparative Example 2 replaced the solid electrolyte membrane with a PE membrane. As shown in Table 1, the discharge energy retention rate, low-temperature energy efficiency, and high-temperature 600-cycle energy retention rate of Comparative Example 2 were significantly lower than those of Example 1. This indicates that, under the premise that all other parameters and materials are exactly the same, using the solid electrolyte membrane of this invention instead of the conventional PE membrane allows the solid electrolyte membrane of this invention to form a synergistic matching effect with the conductive polymers inside the positive and negative electrodes and the gel cross-linked network formed by liquid injection and curing. This effectively reduces the overall internal resistance of the battery, constructs a continuous and stable lithium-ion transport channel, and reduces polarization losses during high-rate charge and discharge processes. Simultaneously, it improves the lithium-ion transport kinetics under low-temperature conditions, enhances low-temperature energy utilization efficiency, and effectively suppresses electrolyte decomposition, membrane thermal shrinkage, and interfacial side reactions during high-temperature cycling, significantly improving the battery's high-temperature long-cycle capacity retention rate and overall operational stability.

[0147] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A solid-state lithium battery, characterized in that: It includes a positive electrode, a solid electrolyte layer and a negative electrode layer stacked in sequence, wherein the negative electrode includes a first conductive polymer and the solid electrolyte layer includes a second conductive polymer.

2. The solid-state lithium battery according to claim 1, characterized in that: A first quasi-solid electrolyte layer is provided between the solid electrolyte layer and the negative electrode, and the first quasi-solid electrolyte layer includes a third conductive polymer.

3. The solid-state lithium battery according to claim 2, characterized in that: The positive electrode includes a fourth conductive polymer; and / or, A second quasi-solid electrolyte layer is provided between the positive electrode and the solid electrolyte layer, and the second quasi-solid electrolyte layer includes a third conductive polymer.

4. The solid-state lithium battery according to claim 3, characterized in that: At least one of the first conductive polymer, the second conductive polymer, the third conductive polymer, and the fourth conductive polymer is grafted with modified multifunctional groups, wherein the modified multifunctional groups include at least one of diacrylate double bonds, thiophene-sulfonic acid groups, and ether-carboxyl multi-branched chains.

5. The solid-state lithium battery according to claim 1, characterized in that, The negative electrode sheet comprises the following components and their mass percentages: 75-98% negative electrode active material, 0.2-3% conductive carbon, 0.3-4% binder, 1-15% lithium powder, 0.55-7% primary conductive polymer.

6. The solid-state lithium battery according to claim 5, characterized in that: The lithium powder comprises a lithium metal core and a graphite layer covering at least a portion of the surface of the lithium metal core; and / or, The negative electrode active material includes at least one of the following: mesophase carbon microspheres, natural graphite, artificial graphite, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, silicon-carbon composites, lithium metal, and lithium metal alloys; and / or, The positive electrode sheet includes a positive electrode active material, which includes at least one of lithium cobalt oxide, lithium iron phosphate, nickel-cobalt-manganese ternary, lithium manganese iron phosphate, lithium manganese oxide, and lithium-rich manganese-based materials.

7. A method for preparing a solid-state lithium battery as described in any one of claims 1-6, characterized in that, Includes the following steps: The solid-state lithium battery is obtained by stacking and fixing a negative electrode sheet including the first conductive polymer, a solid electrolyte layer including the second conductive polymer, and a positive electrode sheet. The solid electrolyte layer is located between the negative electrode and the positive electrode.

8. The method for preparing a solid-state lithium battery according to claim 7, characterized in that: Before the fixation process, the laminated body after the lamination process is subjected to gel electrolyte injection and heat curing processes in sequence. After processing, a first quasi-solid electrolyte layer containing a third conductive polymer is formed between the negative electrode and the solid electrolyte layer, and a second quasi-solid electrolyte layer containing a third conductive polymer is formed between the positive electrode and the solid electrolyte layer.

9. The method for preparing a solid-state lithium battery according to claim 7, characterized in that: The polymer monomers of the first, second, third, and fourth conductive polymers are respectively selected from at least one of poly(ethylene glycol) methyl ether methacrylate, polyethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol dimethyl ether, 1,3-dioxane, and poly(ethylene glycol) methyl ether acrylate; and / or, The polymer monomer is selected from at least one of the following: poly(ethylene glycol) methyl ether methacrylate grafted with modified polyfunctional groups, poly(ethylene glycol) diacrylate grafted with modified polyfunctional groups, poly(ethylene glycol) diacrylate grafted with modified polyfunctional groups, triethylene glycol dimethacrylate grafted with modified polyfunctional groups, triethylene glycol dimethyl ether grafted with modified polyfunctional groups, 1,3-dioxane, and poly(ethylene glycol) methyl ether acrylate grafted with modified polyfunctional groups.

10. The method for preparing a solid-state lithium battery according to claim 8, characterized in that: The injection coefficient of the gel electrolyte injection treatment is 3-6 g / Ah, and after injection, it is maintained at a pressure of 0.15-0.3 MPa for 5-20 min; and / or, The heat curing process includes the following steps: first, curing at a temperature of 40-60℃ for 4-6 hours; then, curing at a temperature of 70-80℃ for 2-4 hours to obtain a solid-state lithium battery.

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