Composite electrode tab, method of manufacturing the same, and solid-state battery and electric device

Abstract

This application relates to the field of secondary battery technology, and discloses a composite electrode sheet and its preparation method, a solid-state battery, and an electrical device thereof. The composite electrode sheet of this application includes a current collector and an electrode layer. By setting a continuous gradient distribution of electronically conductive and ionicly conductive components in the electrode layer, the electron transport path is optimized on the current collector side, while the ion transport path is optimized on the electrode layer surface. This specifically addresses the bottleneck of transport dynamics within thick electrodes, effectively improving the synergistic transport efficiency of ions and electrons within the electrode, reducing interfacial impedance, and enhancing the capacity utilization and cycle stability of thick electrodes.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a composite electrode sheet and its preparation method, as well as solid-state batteries and electrical devices. Background Technology

[0002] Sulfide solid electrolyte materials, such as sulfide-germanium sulfide Li6PS5Cl, have excellent room-temperature lithium-ion conductivity (up to 10). -2 Solid-state batteries, with a capacity on the order of S / cm, are considered a key material system for driving the commercialization of high-energy-density all-solid-state batteries. However, these batteries face significant technical bottlenecks in practical applications. The primary problem lies in the limited capacity utilization of thick electrode structures; when electrode thickness is increased to achieve high areal capacity (typically exceeding 4 mAh / cm²),... 2 During battery cycling, the diffusion path of lithium ions within the electrode is significantly prolonged due to the tortuous nature of the porous structure. Simultaneously, electron transport is constrained by the uniformity and connectivity of the conductive network, making it difficult for the active material in the deeper regions of the electrode to fully participate in the electrochemical reaction, resulting in a significant discrepancy between the actual discharge capacity and the theoretical value. Secondly, the binders commonly used in traditional electrodes, such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), are insulating materials. They form isolated, non-conductive regions within the electrode, unable to conduct lithium ions or electrons, thus not only occupying effective space for the active material but also disrupting the ion and electron transport channels. More seriously, during battery cycling, the volume expansion and contraction of the active material particles due to lithium insertion / extraction can easily trigger mechanical separation at the binder-particle interface, causing localized failure of the transport network and further exacerbating internal resistance and capacity decay.

[0003] To address the aforementioned issues, existing technologies attempt optimization through gradient design. Some solutions focus on binder modification, such as using composite binder systems that combine rigid and flexible components to improve the rheological properties of the slurry and the mechanical strength of the electrode. However, these methods still rely on insulating binders and fail to endow the binders with the intrinsic ionic and electronic dual conductivity. Other technologies construct three-dimensional network structures through chemical crosslinking to enhance interfacial stability, but they do not consider the directional distribution of binder components along the electrode thickness direction, thus failing to specifically address internal transport dynamics issues. Furthermore, some external gradient coating strategies introduce polymer concentration gradient layers at the electrolyte membrane-electrode interface. While this can improve local contact, it requires additional multi-layer coatings, resulting in high process complexity. Moreover, the coating only acts on the external region of the electrode, offering no substantial improvement to the ion-electron co-transport within the electrode body. These limitations highlight the inadequacies of existing technologies in the design of the electrode's internal microstructure. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a composite electrode sheet and its preparation method, so that the composite electrode sheet can effectively improve the ion and electron co-transmission efficiency inside the electrode, reduce the interface impedance, and improve the capacity utilization and cycle stability of the thick electrode.

[0005] Another objective of this application is to provide a solid-state battery and electrical device based on the composite electrode sheet described in this application.

[0006] To achieve all or part of the above objectives, as a first aspect of this application, a composite electrode sheet is provided, comprising a current collector and an electrode layer, wherein the electrode layer is disposed on at least one surface of the current collector; the electrode layer comprises an electronically conductive component and an ionicly conductive component; the content of the electronically conductive component decreases continuously in a gradient along the thickness direction of the electrode layer from the side closer to the current collector to the side farther from the current collector, and the content of the ionicly conductive component increases continuously in a gradient along the thickness direction of the electrode layer from the side closer to the current collector to the side farther from the current collector.

[0007] Optionally, the ratio of the average electronic conductivity within a thickness range of 0-50% from the current collector on the side closer to the current collector to the average electronic conductivity within a thickness range of 0-50% from the electrode layer surface on the side closer to the electrode layer surface is >1:1; The ratio of the average ionic conductivity within a thickness range of 0-50% of the electrode layer surface near the electrode layer surface to the average ionic conductivity within a thickness range of 0-50% of the current collector surface near the current collector is >1:1. Further optionally, the ratio of the average electronic conductivity within a thickness range of 0-20% of the current collector surface near the current collector to the average electronic conductivity within a thickness range of 0-20% of the electrode layer surface near the electrode layer surface is ≥2:1. The ratio of the average ionic conductivity within a thickness range of 0-20% from the electrode layer surface on the side closest to the electrode layer surface to the average ionic conductivity within a thickness range of 0-20% from the current collector on the side closest to the current collector is ≥2:1.

[0008] Optionally, the electrode layer comprises an electrode active material, a solid electrolyte, and a charged dual-conducting binder, wherein the charged dual-conducting binder comprises an electronically conductive component and an ionicly conductive component. Further optionally, the charged dual-conducting binder further comprises a crosslinking agent. Further optionally, the crosslinking agent comprises dicumyl peroxide and / or benzophenone.

[0009] Optionally, the electronically conductive component comprises sulfonated poly(3,4-ethylenedioxythiophene) and / or carboxylated carbon nanotubes, and the ionicly conductive component comprises one or more polymers containing polar coordinating groups, or comprises one or more ionicly conductive components obtained by combining a polymer containing polar coordinating groups with an electrolyte lithium salt. The polymer containing polar coordinating groups comprises one or more of polyethylene oxide, polypropylene carbonate, and polytrimethylene carbonate. Further optionally, the molar ratio of the polar coordinating group to lithium in the electrolyte lithium salt is (15-25):1.

[0010] Optionally, the mass ratio of the electronically conductive component to the ionicly conductive component is 1:(2-5).

[0011] Optionally, the mass ratio of the electrode active material, solid electrolyte and charged dual-conducting binder is (70-80):(10-20):(1-10).

[0012] Optionally, the electrode active material is a positive electrode active material, including one or more of single-crystal cobalt ternary, lithium iron phosphate, lithium cobalt oxide, and lithium-rich manganese-based materials; the solid electrolyte includes a sulfide solid electrolyte.

[0013] As a second aspect of this application, a method for preparing a composite electrode sheet as described in this application is provided, comprising: Provide electrode slurries comprising electrode active materials, solid electrolytes, and charged dual-conducting binders; An electrode layer is formed by depositing the electrode slurry on at least one surface of the current collector along the thickness direction. Before the electrode layer is completely dry, a positive power supply electrode is placed on the side of the current collector and a negative power supply electrode is placed on the surface of the electrode layer. An electric field is applied to treat the electrode layer, causing the electronic conductive component in the charged dual-conductive binder to migrate and accumulate towards the current collector side, and the ionic conductive component in the charged dual-conductive binder to migrate and accumulate towards the surface of the electrode layer as the solvent evaporates. Depending on whether the electrode layer contains a crosslinking agent and the type of crosslinking agent, heat treatment, thermal initiation, or photoinitiation treatment is selected to cure the electrode layer to obtain the composite electrode sheet.

[0014] Optionally, the residual solvent content of the electrode layer before it is completely dried is 20-60%.

[0015] Optionally, the treatment by applying an electric field includes treatment at a field strength of 0.1-20 V / mm and a temperature of 20-80℃ for 5-30 minutes.

[0016] Optionally, the heat treatment includes treatment at 80-200℃ for 30-120 min; the thermal initiation includes treatment at 20-500℃; and the photoinitiation involves irradiation with light of the appropriate wavelength and power according to the type of crosslinking agent.

[0017] As a third aspect of this application, a solid-state battery is provided, including the composite electrode sheet described in this application, an electrode sheet with the opposite polarity to the composite electrode sheet, and an electrolyte.

[0018] As a fourth aspect of this application, an electrical device is provided, including the solid-state battery described in this application, wherein the secondary battery provides electrical energy to the electrical device or serves as an energy storage unit for the electrical device.

[0019] This application addresses the bottleneck of transport dynamics within thick electrodes by setting a continuous gradient distribution of electronically and ionicly conductive components in the electrode layer. This optimizes the electron transport path on the current collector side and the ion transport path on the electrode layer surface, thereby effectively improving the efficiency of ion and electron co-transport within the electrode, reducing interfacial impedance, and enhancing the capacity utilization and cycle stability of thick electrodes. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application. Figure 1 The diagram shown is a process flow chart for the fabrication of the composite electrode sheet of this application. Figure 2 The diagram shown illustrates the fabrication principle of the composite electrode sheet of this application. Detailed Implementation

[0021] This application discloses a composite electrode sheet and its preparation method, as well as a solid-state battery and electrical device. Those skilled in the art can refer to the content of this application and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The products and processes described in this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the products and processes described herein without departing from the content, spirit, and scope of this application to realize and apply the technology of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0022] It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Moreover, the embodiments and features described in this application can be combined with each other without conflict.

[0023] Existing sulfide-based all-solid-state batteries face challenges in thick-electrode applications, including long lithium-ion and electron transport paths and obstructed transport, resulting in low utilization of active materials. Traditional insulating binders create transport islands, further exacerbating the ion / electron transport bottleneck. Current gradient electrode designs have failed to effectively address the conductivity issues of the binder itself, or their processes are complex and cannot optimize the internal transport dynamics of the electrode.

[0024] In response, the first aspect of this application proposes a composite electrode sheet comprising a current collector and an electrode layer. The electrode layer is disposed on at least one surface of the current collector, which refers to two opposing main surfaces of the current collector, i.e., two surfaces perpendicular to the thickness direction of the current collector. The electrode layer may be disposed on one of the main surfaces or on both main surfaces simultaneously. The electrode layer contains both electronically conductive and ionicly conductive components. By continuously decreasing the content of the electronically conductive component along the thickness direction of the electrode layer from the side closer to the current collector to the side farther away from the current collector, while continuously increasing the content of the ionicly conductive component along the thickness direction of the electrode layer from the side closer to the current collector to the side farther away from the current collector, the charge transport path within the electrode is optimized.

[0025] Among them, the electronically conductive component is usually a negatively charged material, which refers to a material that is responsible for electron transport in the electrode layer and carries a negative charge itself. It can form a conductive network with other components in the electrode layer.

[0026] Ion-conducting components are typically neutral or weakly charged materials. They are materials that are responsible for ion transport in the electrode layer and are uncharged or only have a weak charge. They can promote the migration of lithium ions inside the electrode layer. Ion-conducting components are uncharged or weakly charged to avoid neutralization with negatively charged electronically conductive components. The zeta potential of uncharged or weakly charged materials is 0 to ±10 mV.

[0027] A continuous gradient decrease / increase refers to the smooth and uninterrupted trend of the content change of electronic conductive components or ionic conductive components in the thickness direction of the electrode layer, rather than a step-like or abrupt distribution; correspondingly, the conductivity of the two components will also show a smooth and uninterrupted decreasing / increasing trend.

[0028] In the composite electrode sheet described in this application, the current collector can be made of various conductive materials, such as copper foil, aluminum foil, nickel foil, or stainless steel mesh. The electrode layer can be formed on the surface of the current collector by coating, printing, or spraying.

[0029] The composite electrode sheet of this application can effectively solve the problems of long lithium-ion and electron transport paths and transport obstruction in thick electrode applications. By achieving a bidirectional continuous gradient distribution of electronically and ionicly conductive components, the anisotropic optimization of charge transport capability inside the electrode is realized, reducing electron transport impedance and enhancing ion transport capability, thereby improving the utilization rate of active materials and overcoming the transport bottleneck caused by traditional insulating binders.

[0030] In some embodiments of this application, the ratio of the average electronic conductivity within a thickness range of 0-50% from the current collector on the side closer to the current collector to the average electronic conductivity within a thickness range of 0-50% from the electrode layer surface on the side closer to the electrode layer surface is >1:1; The ratio of the average ionic conductivity within a thickness range of 0-50% from the electrode layer surface on the side closest to the electrode layer surface to the average ionic conductivity within a thickness range of 0-50% from the current collector on the side closest to the current collector is >1:1.

[0031] The terms "0-50% thickness range from the current collector side" and "0-50% thickness range from the electrode layer surface side" refer to areas extending inward from the current collector side and the electrode layer surface side, respectively, to 50% of the total electrode layer thickness in the electrode layer thickness direction. These two regions represent two key macroscopic regions for electron / ion transport within the electrode layer. Quantifying the average electron / ion conductivity of these regions can effectively assess the distribution of electron / ion conductive components within the electrode layer and their impact on electron / ion transport capabilities. Specifically, the average electron / ion conductivity of regions of different thicknesses can be obtained through techniques such as micro-electrochemical impedance spectroscopy (EIS), scanning probe microscopy (SPM) combined with conductive atomic force microscopy (C-AFM), and theoretical calculations and simulations based on actual distribution data of electron / ion conductive components in the electrode layer.

[0032] By quantitatively defining the ratio of average electronic to ionic conductivity in different regions along the thickness of the electrode layer, precise control over the gradient distribution of electronic / ionic conductive components is achieved. By specifying that the average electronic conductivity near the current collector is higher than that near the electrode surface, and that the average ionic conductivity near the electrode surface is higher than that near the current collector, efficient electron / ion transport channels are ensured within the electrode. This ratio definition not only clarifies the distribution trend of electronic / ionic conductive components along the thickness direction but also ensures, through quantification, that the non-uniform design of electron / ion transport capacity within the electrode layer meets expectations, effectively solving the problems of hindered electron transport deep within the electrode and hindered ion transport on the electrode surface.

[0033] In other embodiments of this application, the present application further proposes to optimize the composite electrode sheet. Specifically, the ratio of the average electronic conductivity within a thickness range of 0-20% from the current collector on the side near the current collector to the average electronic conductivity within a thickness range of 0-20% from the electrode layer surface on the side near the electrode layer surface is ≥2:1; at the same time, the ratio of the average ionic conductivity within a thickness range of 0-20% from the electrode layer surface on the side near the electrode layer surface to the average ionic conductivity within a thickness range of 0-20% from the current collector on the side near the current collector is ≥2:1.

[0034] Specifically, the ratio of "the average electronic conductivity within a 0-20% thickness range near the current collector to the average electronic conductivity within a 0-20% thickness range near the electrode layer surface ≥ 2:1" aims to ensure that electrons can be transported with minimal contact resistance when entering or leaving the current collector, thereby constructing an efficient electron collection and transport channel. The ratio of "the average ionic conductivity within a 0-20% thickness range near the electrode layer surface to the average ionic conductivity within a 0-20% thickness range near the current collector ≥ 2:1" is primarily aimed at promoting rapid ion entry and exit at the electrode-electrolyte interface and ensuring a sufficient ion supply near the surface-active material particles. Through these technical solutions, this application can effectively compensate for the problem of insufficient conductivity in local areas in conventional gradient designs, enabling the electron transport network and ion transport network to exhibit more targeted distribution characteristics in the electrode thickness direction.

[0035] In some embodiments of this application, the electrode layer includes an electrode active material, a solid electrolyte, and a charged dual-conductive binder. The charged dual-conductive binder includes an electronically conductive component and an ionicly conductive component. This application introduces a charged dual-conductive binder into the electrode layer, transforming the binder, which originally served as a structural support, into an active component with charge transport capabilities, thereby fundamentally eliminating the transport bottleneck caused by traditional insulating binders. The electrode active material, as the core of the electrochemical reaction, achieves the reconstruction of ion and electron transport paths through the synergistic effect of the solid electrolyte and the charged dual-conductive binder. The negatively charged electronically conductive component in the charged dual-conductive binder can form good electrical contact with the electronic conductive network within the electrode layer, ensuring that electrons can be smoothly transported to the surface of the active material; simultaneously, the ionicly conductive component provides a continuous migration channel for lithium ions, solving the problem of ion transport obstruction within the electrode. By integrating electronically conductive and ionicly conductive components into the same binder system, not only is the internal microstructure of the electrode optimized, but the charge properties of the binder also enhance its interfacial compatibility with the active material and solid electrolyte. This allows the electrode to maintain more uniform electrochemical activity in the thickness direction, effectively improving the overall performance of the thick electrode during charge and discharge.

[0036] In some embodiments of this application, the charged dual-conducting adhesive further includes a crosslinking agent, used in an amount of 0.1-1% of the total mass of the charged dual-conducting adhesive, for example, 0.2%, 0.5%, 0.8%, or any value between the two. A crosslinking agent is a substance that can promote the formation of chemical bonds between polymer molecular chains, thereby connecting independent polymer chains into a three-dimensional network structure. This chemical bond can be a covalent bond, ionic bond, or coordinate bond, etc. Its main function is to enhance the mechanical strength, thermal stability, solvent resistance, and dimensional stability of the polymer material. Introducing a crosslinking agent into the charged dual-conducting adhesive enables the molecular chains of the adhesive to be connected through chemical bonding, forming a more stable and robust three-dimensional network structure. This helps to improve the bonding force between the adhesive and the electrode active material, and enhances the mechanical strength and structural stability of the adhesive itself, thereby effectively coping with the stress caused by volume changes in the electrode during cycling, and preventing the adhesive network from dissociating or failing.

[0037] In some other embodiments of this application, the crosslinking agent includes dicumyl peroxide and / or benzophenone. Dicumyl peroxide is an organic peroxide, belonging to the category of thermally initiated free radical crosslinking agents. Its molecular structure contains peroxide bonds, which easily decompose under heating conditions to generate free radicals. These free radicals can initiate crosslinking reactions of polymer molecular chains, forming a three-dimensional network structure, thereby improving the mechanical strength, heat resistance, and dimensional stability of the polymer material. In practical applications, dicumyl peroxide can be uniformly dispersed in a charged dual-conductive binder, and then decomposed at a specific temperature in a subsequent heat treatment step to initiate crosslinking of the binder components. Alternatively, dicumyl peroxide can be added as an additive during the preparation of the electrode slurry to ensure thorough mixing with the binder components, so that effective crosslinking and curing can be achieved by heating after the electrode layer is formed. Meanwhile, benzophenone is an organic compound, often used as a photoinitiator. Its molecular structure contains carbonyl groups, which can be excited and generate free radicals after absorbing ultraviolet light of a specific wavelength. These free radicals can initiate polymer polymerization or crosslinking reactions, achieving rapid curing of the material. In practical applications, benzophenone can be incorporated into charged dual-conductivity binders. After the electrode layer is formed, ultraviolet light irradiation can generate free radicals, thereby inducing cross-linking reactions in the binder components. Alternatively, benzophenone can be added to the electrode slurry, and after the electrode layer has dried and formed, it can be treated with light of a specific wavelength (such as ultraviolet light) to achieve rapid photocuring and cross-linking of the binder components.

[0038] In some embodiments of this application, the electronically conductive component includes sulfonated poly(3,4-ethylenedioxythiophene) and / or carboxylated carbon nanotubes, and the ionicly conductive component includes one or more polymers containing polar coordinating groups, or includes one or more ionicly conductive components obtained by combining a polymer containing polar coordinating groups with an electrolyte lithium salt. The polymer containing polar coordinating groups includes one or more of polyethylene oxide, polypropylene carbonate, and polytrimethylene carbonate.

[0039] The electronically conductive component is crucial for achieving efficient electron transport within the electrode layer and ensuring its directional migration under an electric field. This application preferably employs sulfonated poly(3,4-ethylenedioxythiophene) and / or carboxylated carbon nanotubes. Sulfonated poly(3,4-ethylenedioxythiophene) is a conjugated polymer with good electronic conductivity. Sulfonation imparts a negative charge to its surface, allowing it to effectively migrate and accumulate towards the current collector under an electric field, thus forming a high electronic conductivity region on the electrode layer near the current collector. Carboxylated carbon nanotubes utilize the excellent electronic conductivity and high aspect ratio of carbon nanotubes themselves. Carboxylation introduces a negative charge to their surface, enabling them to also possess the ability to induce electron migration under an electric field and contributing to the construction of a continuous and stable electron transport network. Both materials effectively reduce the contact resistance between the electrode and the current collector and improve electron transport efficiency deep within the electrode.

[0040] The ionicly conductive component is designed to facilitate lithium-ion transport within the electrode layer. This component may include one or more polymers containing polar coordinating groups (polymer repeating units). These polymers coordinate with lithium ions through polar groups (such as ether bonds, carbonyl groups, etc.) with lone pairs of electrons on their molecular chains, thereby promoting the dissociation of the electrolyte lithium salt and providing a transport channel for lithium ions. Due to its neutral or weakly charged charge, under the influence of an electric field, this component mainly migrates and accumulates on the electrode layer surface as the solvent evaporates, thus forming a region of high ionic conductivity on the electrode layer surface.

[0041] To further enhance the ionic conductivity of the ionic conductive component, the ionic conductive component may further include one or more of the following: a polymer containing polar coordinating groups combined with an electrolyte lithium salt. By combining the polymer with an electrolyte lithium salt (e.g., LiTFSI, LiFSI, LiPF6, etc.), the electrolyte lithium salt dissociates within the polymer matrix, providing mobile lithium ions, while the polar coordinating groups of the polymer help stabilize lithium ions and promote their hopping transport within the polymer chain segments, forming a highly efficient solid-state polymer electrolyte system.

[0042] The preferred polymers containing polar coordinating groups in this application include one or more of polyethylene oxide, polypropylene carbonate, and polytrimethylene carbonate. Polyethylene oxide (PEO) is a classic polymer solid electrolyte matrix because its repeating ether oxygen group (-CH2-CH2-O-) can effectively coordinate with lithium ions. Polypropylene carbonate (PPC) and polytrimethylene carbonate (PTMC) have repeating carbonate groups (-CH(CH3)-CH2-O-(C=O)-O- and -CH2-CH2-CH2-O-(C=O)-O-), in which both carbonyl oxygen and ether oxygen can coordinate with lithium ions, and they generally have good mechanical properties and the ability to dissolve lithium salts, providing diverse transport pathways for lithium ions.

[0043] The specific combination of the above materials not only further optimizes the functionalized gradient distribution of electronically and ionicly conductive components in the electrode thickness direction, but also ensures the effectiveness of electric field-induced migration during the preparation process through the polarity and charge characteristics of the materials themselves. This creates a complementary network of electron and ion transport inside the electrode, significantly improving the utilization rate of active materials and the overall electrochemical performance of thick electrodes in all-solid-state batteries. It effectively solves the problems of insufficient capacity utilization of thick electrodes and transport bottlenecks caused by inert binders.

[0044] In other embodiments of this application, the molar ratio of the polar coordinating group to lithium in the electrolyte lithium salt is (15-25):1, for example, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, or any value between the two; when the polymer containing the polar coordinating group is selected as PCC, the relationship with Li is taken into consideration. + The coordination mechanism of PPC is complex and its molecular weight distribution is wide, making it difficult to control by the molar ratio of polar coordinating groups. Therefore, a mass ratio can be used to limit the proportion of PPC and the electrolyte lithium salt. For example, the amount of electrolyte lithium salt added is generally 4-6% of PPC. Within this range, the aim is to optimize the dissociation and transport efficiency of lithium ions, ensuring that the polar groups on the polymer chain can form appropriate coordination with lithium ions. This effectively promotes the full dissociation of the electrolyte lithium salt, ensuring a sufficient concentration of free lithium ions, while avoiding excessive binding of lithium ions due to overly strong coordination, thus guaranteeing efficient hopping transport of lithium ions within the polymer chain. One way to achieve this molar ratio is to accurately calculate and proportion the mass or molar amount of polymer and lithium salt based on the content of polar coordinating groups in the selected polymer and the molecular weight of the electrolyte lithium salt during the preparation of the ionicly conductive component. Another approach is to adjust the degree of polymerization or functional group density of the polymer so that, when combined with a specific amount of lithium salt, it can naturally form a molar ratio within this optimized range. In some embodiments of this application, the mass ratio of the electronically conductive component to the ionicly conductive component is 1:(2-5), for example, 1:1, 1:2, 1:3, 1:4, 1:5, or any value between the two. Within this range, the problem of unbalanced transport network construction caused by component ratio imbalance can be effectively solved. Specifically, in the electrode layer, the electronically conductive component, as the main body of electron transport, ensures sufficient electron conductivity within the electrode to meet the electrochemical reaction requirements of the active material, given its appropriate ratio. Simultaneously, the ionicly conductive component, while ensuring unobstructed ion transport channels, works synergistically with the electronically conductive component, avoiding the problem of transport impedance mismatch caused by an excess of a single component.

[0045] In some embodiments of this application, the mass ratio of the electrode active material, solid electrolyte, and charged dual-conductive binder is (70-80):(10-20):(1-10), for example, 70:20:10, 72:19:9, 76:20:4, 78:20:2, 80:10:10, or any ratio between the two. 70-80 parts of electrode active material ensure the electrode has a high energy density, meeting the battery's energy storage requirements; 10-20 parts of solid electrolyte provide ample and efficient transport channels for lithium ions within the electrode, effectively alleviating the bottleneck of limited ion transport in solid-state batteries; and 1-10 parts of charged dual-conductive binder, while ensuring the integrity and mechanical strength of the electrode structure, provide a key functional component for the gradient distribution of electronically and ionicly conductive components under electric field induction. Furthermore, the electrode layer may also include a conductive agent, which can be added as needed according to rate performance requirements, with a mass ratio of (1-5) for reference. Within this range, without sacrificing electrode energy density, the charge transport efficiency inside the electrode is significantly improved, maximizing the capacity utilization of thick electrodes. This effectively overcomes the problems of insufficient capacity utilization of traditional thick electrodes and transport bottlenecks caused by inert binders, providing key support for realizing high-performance all-solid-state batteries.

[0046] In some embodiments of this application, the electrode active material is a positive electrode active material, including one or more of single-crystal cobalt ternary, lithium iron phosphate, lithium cobalt oxide, and lithium-rich manganese-based materials; the solid electrolyte includes a sulfide solid electrolyte.

[0047] The positive electrode active material is the core functional component of the composite electrode sheet, and its performance directly determines the energy density, power characteristics, and cycle life of the battery. The positive electrode active materials selected in this application, such as single-crystal cobalt ternary materials, possess excellent structural stability and high energy density; lithium iron phosphate has good safety and long cycle life; lithium cobalt oxide has high energy density and is a commonly used positive electrode material for lithium-ion batteries; and lithium-rich manganese-based materials have ultra-high capacity potential. In addition, the positive electrode active material can also be layered oxides such as lithium nickel cobalt manganese oxide (NCM) or lithium nickel cobalt aluminum oxide (NCA), or spinel-type lithium manganese oxide. These materials can stably insert and extract lithium ions during charge and discharge, providing sufficient capacity reserves and good electrochemical activity for the electrode.

[0048] Sulfide solid-state electrolytes are ideal for realizing high-energy-density all-solid-state batteries due to their extremely high ionic conductivity. Typical sulfide solid-state electrolytes include, but are not limited to, sulfide-germanium sulfide type (such as Li6PS5Cl, Li7P3S6I) and thiolicon type (such as Li...). 10 GeP2S 12 ) and glass-ceramic type (such as Li7P3S) 11 These sulfide solid electrolytes not only possess high ionic conductivity but also good mechanical properties and chemical stability, enabling them to effectively construct ion transport networks that span the thickness of the electrode, thereby overcoming the problem of limited ion transport paths in thick electrodes.

[0049] In a second aspect of this application, a method for preparing the composite electrode sheet described in this application is provided, comprising providing an electrode slurry comprising an electrode active material, a solid electrolyte, and a charged dual-conductive binder; depositing the electrode slurry on at least one surface of a current collector along its thickness direction to form an electrode layer; before the electrode layer is completely dry, placing a positive electrode on the current collector side and a negative electrode on the electrode layer surface, and applying an electric field to treat the electrode layer, causing the electronically conductive component in the charged dual-conductive binder to migrate and accumulate towards the current collector side, and the ionicly conductive component in the charged dual-conductive binder to migrate and accumulate towards the electrode layer surface as the solvent evaporates; and, depending on whether the electrode layer contains a crosslinking agent and the type of crosslinking agent, selecting heat treatment, thermal initiation, or photoinitiation treatment to treat the electrode layer to obtain the composite electrode sheet.

[0050] The preparation method of this application achieves a directional and continuous gradient distribution of components within the electrode through the synergistic effect of electric field induction and solvent evaporation, thereby constructing a highly efficient electron and ion transport network. Specifically, an electric field is applied before the electrode layer is completely dry. Utilizing the directional migration characteristics of electronically conductive components under the influence of the electric field, these components are enriched towards the current collector side, thus establishing a region with high electronic conductivity near the current collector and effectively reducing electron transport resistance. By utilizing the characteristic of ionicly conductive components migrating to the electrode layer surface with solvent evaporation, a high ionic conductivity region is constructed on the electrode layer surface, improving the ion transport efficiency at the electrode-electrolyte interface and solving the problem of limited ion transport paths.

[0051] Finally, depending on the presence and type of crosslinking agent in the electrode layer, heat treatment, thermal initiation, or photoinitiation can be selected to solidify the already formed gradient structure, ensuring the stability of the gradient distribution and preventing component rearrangement during subsequent battery cycling, thereby maintaining the long-term transport performance of the electrode.

[0052] In some embodiments of this application, the residual solvent content of the electrode layer before complete drying is 20-60%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any value between the two; wherein the solvent can be a low-polarity solvent such as xylene or ethyl acetate. Applying an electric field before the electrode layer is completely dried mainly utilizes the principle of "electrophoresis" to actively overcome the negative effects of the drying process in order to construct an ideal continuous gradient structure. Under the action of an external vertical electric field (DC), the electronically conductive components in the slurry will migrate directionally towards the positively charged current collector side in the liquid medium; at the same time, as the solvent evaporates, the ionicly conductive components will migrate directionally towards the surface of the electrode layer. Within this residual solvent content range, the electrode layer has lost its overall fluidity and presents a "wet gel" state, but the migration channels still exist, and the electronic / ionicly conductive components can move in the liquid phase channels formed by the residual solvent; although capillary flow begins to appear, it has not yet become dominant, and the external electric field can counteract the capillary flow and directionally drive the components. When the residual solvent content is above 60%, the electrode layer is relatively sparse, resembling a slurry. At this point, although component migration is rapid, the strong convection effect makes it difficult to form a stable gradient. Simultaneously, the electrode layer strength is extremely low, and the electric field may cause irregular deformation of the liquid surface. When the residual solvent content is below 20%, the electrode layer surface begins to dry out, and the viscosity increases sharply. The resistance to component migration increases significantly, and the "electrophoresis" efficiency drops drastically.

[0053] In some embodiments of this application, the treatment by applying an electric field includes treatment for 5-30 minutes at a field strength of 0.1-20 V / mm and a temperature of 20-80°C. The electric field strength can be selected from 0.1 V / mm, 1 V / mm, 2 V / mm, 3 V / mm, 4 V / mm, 5 V / mm, 6 V / mm, 7 V / mm, 8 V / mm, 9 V / mm, 10 V / mm, 11 V / mm, 12 V / mm, 13 V / mm, 14 V / mm, 15 V / mm, 16 V / mm, 17 V / mm, 18 V / mm, 19 V / mm, 20 V / mm, or any value between any two. The temperature can be selected from 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, or any value between any two. The time can be selected from 5min, 10min, 15min, 20min, 25min, 30min, or any value between any two.

[0054] By optimizing and controlling the field strength, temperature, time, and solvent content during the electric field treatment process, this application ensures that the electronically and ionicly conductive components in the charged dual-conducting binder migrate and accumulate efficiently and stably along the expected gradient direction before the electrode layer is completely dry. Through the above-mentioned optimized parameter control, this application successfully constructs efficient and stable electron and ion transport channels within the electrode layer, significantly improving the electrochemical performance of the thick electrode. This effectively solves the problems of insufficient capacity utilization in thick electrodes and transport bottlenecks caused by inert binders, enabling the composite electrode sheet to achieve higher utilization of active materials and better cycle stability.

[0055] In some embodiments of this application, the heat treatment includes treatment at 80-200°C for 30-120 min; the thermal initiation includes treatment at 20-500°C; and the photoinitiation involves irradiation with light of a corresponding wavelength and power selected according to the type of crosslinking agent.

[0056] Heat treatment is a process for polymers without added crosslinking agents. It alters the physical or chemical properties of the ion-conducting components through heating, achieving adhesion through long-chain entanglement, van der Waals forces, and partial hydrogen bonding. Additionally, electronically conductive components can also play a supporting role in adhesion; for example, sulfonated PEDOT, being a polymer, works on the same principle. Carboxylated carbon nanotubes can also enhance adhesion through hydrogen bonds with -COOH groups. The heat treatment temperature can be selected from 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, or any value between two of these. The time can be selected from 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, or any value between two of these.

[0057] Thermal initiation is a method that uses heat energy to trigger chemical reactions (such as polymerization and crosslinking). In this application, thermal initiation treatment is used to activate the decomposition or reaction of a specific heat-sensitive crosslinking agent in the electrode layer, thereby achieving the curing of the electrically conductive adhesive. The wide temperature range of 20-500°C is designed to accommodate different types of thermal initiators or heat-sensitive crosslinking agents. For example, some initiators may be activated at lower temperatures (such as 50°C), while others require higher temperatures (such as 200°C or higher) for effective decomposition. By selecting an appropriate temperature, it is possible to ensure efficient initiation of crosslinking reactions in different material systems, firmly locking the gradient distribution components induced by the electric field within the electrode layer.

[0058] Photoinitiation is a method that uses light radiation of a specific wavelength to trigger a chemical reaction (such as photopolymerization or photocrosslinking). In this application, photoinitiation treatment is used to activate the reaction of the photosensitive crosslinking agent in the electrode layer, thereby achieving rapid curing of the charged dual-conductivity adhesive. The wavelength and power of the light irradiation are selected according to the type of crosslinking agent. For example, for UV-curable crosslinking agents, a specific band of UV light (such as UVA, UVB, or UVC) can be selected for irradiation, and the light power is adjusted according to the absorption spectrum and reaction rate requirements of the crosslinking agent. This precise light control enables rapid curing, either locally or globally. It not only effectively regulates the crosslinking rate and depth but also avoids potential thermal damage to the electrode active material or solid electrolyte caused by prolonged or high-intensity heat treatment, thus better preserving the gradient structure already formed within the electrode layer.

[0059] In a third aspect of this application, a solid-state battery is provided, comprising the composite electrode sheet described in this application, an electrode sheet with the opposite polarity to the composite electrode sheet, and an electrolyte. Integrating the composite electrode sheet with a continuous gradient conductivity structure into the solid-state battery constructs a complete electrochemical energy storage system. As a core component, the composite electrode sheet's continuous gradient distribution of electronically and ionicly conductive components effectively alleviates the mismatch between electron and ion transport paths in thick electrodes. By introducing an electrode sheet with the opposite polarity to the composite electrode sheet and an electrolyte, this scheme ensures the integrity of the ion transport channels within the battery. The enrichment of electronically conductive components near the current collector in the composite electrode sheet reduces the contact resistance between the electrode and the current collector, while the increase in ionicly conductive components near the electrode surface optimizes the ion transport kinetics at the electrode-electrolyte interface. This configuration allows for more uniform electrochemical reactions within the electrodes during charging and discharging, avoiding polarization caused by excessive local current density, thereby improving the overall electrochemical performance of the solid-state battery.

[0060] In a fourth aspect of this application, an electrical device is provided, including the solid-state battery described in this application, wherein the solid-state provides electrical energy to the electrical device or serves as an energy storage unit for the electrical device.

[0061] Solid-state batteries provide electrical energy to electrical devices by converting stored chemical energy into electrical energy through a discharge process and supplying it to the devices to power their operation. For example, in electric vehicles, solid-state batteries power the drive motor; in portable electronic devices, solid-state batteries directly power the internal circuitry.

[0062] Solid-state batteries, used as energy storage units in electrical devices, refer to batteries that not only provide electrical energy but also act as energy buffers and storage media. They can be charged when powered by an external power source and released when needed. For example, in smart grids or home energy storage systems, solid-state batteries can be charged during off-peak hours and discharged during peak hours, achieving peak shaving and valley filling, thus optimizing energy utilization. In hybrid vehicles, solid-state batteries can recover and store braking energy, providing auxiliary power during acceleration and improving fuel efficiency.

[0063] The electrical equipment may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0064] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials remain consistent to ensure comparability. Furthermore, all materials used in this application are commercially available.

[0065] The following provides a further description of a composite electrode sheet, its preparation method, solid-state battery, and electrical device provided in this application.

[0066] Example 1: Electric field-induced gradient composite electrode of PEO / sulfonated PEDOT system Reference Figure 1 Preparation of the process flow chart. First, prepare the dual-conductive binder precursor solution by weighing 10g PEO and the corresponding amount of LiTFSI (EO:Li molar ratio 20:1) and adding them to 500mL xylene. Stir at 60℃ for 2 hours until completely dissolved to obtain a PEO-LiTFSI solution. After cooling to room temperature, weigh 2.5g sulfonated PEDOT and add it to the above solution. Continue stirring for 1 hour to obtain a homogeneous solution with a solid content of 2 wt%, wherein the mass ratio of PEO-LiTFSI to sulfonated PEDOT is 4:1.

[0067] Weigh 7.6 g NCM811 and 2.0 g Li6PS5Cl in a glove box and dry mix for 10 min in a stirrer. Add the above precursor solution (0.4 g on a dry basis) and add an appropriate amount of xylene to adjust the slurry solid content to 65%. Continue stirring for 2 hours to obtain a uniform slurry. Use a scraper to coat the slurry onto a 14 μm thick aluminum foil current collector, adjusting the coating gap until the areal density on one side of the electrode is 30 mg / cm³. 2 Immediately after coating, the electrode is transferred to an electric field treatment device, at which point the residual solvent content in the electrode is approximately 30%.

[0068] The electric field treatment equipment is a modified flatbed hot press. The upper and lower electrodes are made of stainless steel and can be connected to a DC power supply. The electrode spacing is set to 1 cm. The electrode is placed on the lower electrode, with the current collector facing downwards and in contact with the lower electrode to connect to the positive electrode. The upper electrode is connected to the negative electrode. A DC voltage of 10V (corresponding to an electric field strength of 1V / mm) is applied at a temperature of 40℃ for 20 minutes. During this process, sulfonated PEDOT migrates in the opposite direction of the electric field under the drive of the electric field, i.e., towards the current collector side, gradually accumulating there. Meanwhile, PEO-LiTFSI gradually migrates towards the electrode surface and accumulates as the solvent evaporates. See the schematic diagram below. Figure 2 .

[0069] After the electric field treatment, the electrode was transferred to a vacuum drying oven and dried at 80°C for 2 hours to completely evaporate the residual solvent. Finally, it was heat-treated at 120°C for 30 minutes to allow the PEO segments to fully entangle and form a stable physical network, thus obtaining the composite electrode.

[0070] The prepared composite electrode was punched into a 12mm diameter disc to serve as the positive electrode. 200mg of Li6PS5Cl powder was weighed and pressed into shape in a 13mm diameter mold to serve as the electrolyte layer. The negative electrode was made of an indium-lithium alloy foil with a diameter of 12mm and a thickness of 100μm. The electrodes were stacked in the order of positive electrode / electrolyte layer / negative electrode, and the mold battery was assembled under a pressure of 125MPa for 5 minutes. The pressure was maintained at 125MPa during the testing process.

[0071] Example 2: Gradient composite electrode induced by electric field of different intensities The difference between this embodiment and Embodiment 1 is that a DC voltage of 5V (corresponding to a field strength of 0.5V / mm) is applied to the electric field strength and maintained for 20 minutes. The remaining steps are the same as in Embodiment 1.

[0072] Example 3: Gradient composite electrode induced by electric field at different times The difference between this embodiment and Embodiment 1 is that the electric field intensity induction time is adjusted by applying a DC voltage of 10V and holding it for 10 minutes. The remaining steps are the same as in Embodiment 1.

[0073] Example 4: Electric field-induced gradient composite electrode with different solvent contents The difference between this embodiment and Embodiment 1 is that: Immediately after coating, the first stage of drying was performed at 40℃ for 30 minutes, at which point the solvent content in the electrode decreased to 25%. Then, a 10V DC electric field was applied and maintained for 20 minutes. Following this, a second stage of rapid drying was performed, after which the electric field was removed, and drying continued at 80℃ for 1 hour to completely evaporate the solvent. Finally, a heat treatment at 120℃ for 30 minutes was performed.

[0074] Example 5: Electric field-induced gradient composite electrode of carboxylated carbon nanotube system The difference between this embodiment and Example 1 is that the electronically conductive component is replaced by carboxylated carbon nanotubes (CNT-COOH) instead of sulfonated PEDOT. First, 2.5 g of CNT-COOH was ultrasonically dispersed in 500 mL of xylene at 200 W for 1 hour to obtain a uniform dispersion. Then, 10 g of PEO and an appropriate amount of LiTFSI (EO:Li = 20:1) were added, and the mixture was stirred at 60°C for 2 hours until the PEO was completely dissolved. The remaining steps were the same as in Example 1.

[0075] Example 6: Electric field induced gradient composite electrode of polypropylene carbonate system The difference between this embodiment and Example 1 is that the ion-conducting component is replaced by polypropylene carbonate (PPC) instead of PEO. 10g of PPC and the corresponding amount of LiTFSI (added at 5% of the PPC mass) were weighed and added to 500mL of xylene. The mixture was stirred at 60°C for 2 hours until completely dissolved. After cooling, 2.5g of sulfonated PEDOT was added, and the mixture was stirred for 1 hour. Considering the low glass transition temperature of PPC, the electric field induction temperature was adjusted to 60°C; the remaining steps were the same as in Example 1.

[0076] Example 7: Thermally Crosslinked Enhanced Gradient Composite Electrode This embodiment introduces chemical crosslinking based on Example 1. Dicumyl peroxide (DCP) at 0.5% of the total polymer mass is added to the precursor solution as a thermal crosslinking agent. The electric field induction step is the same as in Example 1. After the electric field treatment, the electrode is heat-treated at 120°C for 2 hours to decompose DCP and generate free radicals, initiating crosslinking between PEO chains. The remaining steps are the same as in Example 1.

[0077] Comparative Example 1: Uniform Electrode without Electric Field Treatment The precursor solution was the same as in Example 1. After coating, no electric field was applied, and the mixture was dried directly at 80°C for 2 hours, followed by heat treatment at 120°C for 30 minutes. The remaining steps were the same as in Example 1.

[0078] Comparative Example 2: Conventional Insulating Adhesive Electrode 0.5g of SEBS was dissolved in 9.5g of xylene to form a uniform gel solution. 7.6g of NCM811, 2.0g of Li6PS5Cl, 0.2g of SuperP and 4g of gel solution were mixed and coated onto aluminum foil. The mixture was then vacuum dried at 80°C for 2 hours to obtain a conventional electrode.

[0079] Comparative Example 3: Multilayer Coated Gradient Electrode Simulates traditional multilayer gradient design. Two slurries are prepared: a bottom slurry containing high electronic conductivity components, with a mass ratio of NCM811:Li6PS5Cl:SuperP:sulfonated PEDOT=76:20:3:1; and a top slurry containing high ionic conductivity components, with a mass ratio of NCM811:Li6PS5Cl:SuperP:PEO-LiTFSI=76:20:1:3. The bottom layer is applied first, with an areal density of 15 mg / cm³. 2 After drying, a surface layer is applied, with a total areal density of 30 mg / cm³. 2 .

[0080] Comparative Example 4: Electrode treated with electric field after complete drying The importance of the timing of applying the electric field was verified. The precursor solution was the same as in Example 1. After coating, it was completely dried at 80°C for 2 hours before the electric field was applied, and the electric field conditions were the same as in Example 1.

[0081] Experimental example: Electrochemical tests were performed using the Blue Battery Testing System CT2001A and the Electrochemical Workstation CHI660E.

[0082] During the rate performance test, the charging was uniformly performed at a constant current of 0.1C to 3.7V, and then discharged at 0.1C, 0.2C, 0.5C and 1C to 1.9V respectively. The discharge capacity at each rate was recorded, and the capacity ratio of 1C to 0.1C was calculated.

[0083] Cyclic stability testing was performed at a 0.2C rate for 100 charge-discharge cycles, and the ratio of the discharge capacity in the 100th cycle to that in the 1st cycle was recorded as the capacity retention rate.

[0084] The AC impedance test was performed after the battery was assembled and allowed to stand for 2 hours. The frequency range was 1MHz to 0.1Hz, the amplitude was 10mV, and the test was repeated after 100 cycles. The impedance growth rate was then calculated.

[0085] All examples and comparative samples were assembled into mold batteries and tested according to the above method. The results are summarized in Table 1 below: Table 1

[0086] The rate performance (1C / 0.1C capacity ratio 82-89%) and cycle stability (87.3-95.1%) of Examples 1-7 are significantly better than those of Comparative Example 1 (55% and 64.1%) without gradient, demonstrating that the continuous gradient distribution of "high electron conductivity on the current collector side and high ion conductivity on the surface side" constructed in this application can effectively optimize the transport dynamics inside the thick electrode and improve the utilization rate of the active material. Examples 2, 3, and 4, using different electric field induction conditions and different solvent contents, show that the performance is improved to varying degrees, proving that precise control of process windows such as electric field induction conditions and solvent content is the key to further improving the continuous gradient effect.

[0087] Examples 1, 5, and 6, using different ion-conducting polymers such as PEO and PPC and different electronically conductive components such as sulfonated PEDOT and CNT-COOH, successfully achieved continuous gradient structures and obtained good performance.

[0088] Comparative Example 2 uses a traditional insulating adhesive, with a rate capability of only 48% and a cycle retention rate of 52.3%, which is far inferior to the dual-conductive adhesive design of this application. Comparative Example 3 uses a multi-layer coating gradient, which shows some improvement (62% and 75.3%), but is still inferior to the electric field-induced integrated gradient of this application, demonstrating that the electric field-induced method has advantages in terms of gradient continuity and interface bonding.

[0089] In Example 7, the cycle retention rate increased to 93.5% after the introduction of chemical crosslinking, indicating that chemical crosslinking can enhance the stability of the network structure and extend the cycle life, and can be regarded as a preferred solution.

[0090] In summary, this application effectively solves the transport bottleneck and interfacial side reaction problems of thick electrodes in sulfide all-solid-state batteries by constructing a gradient dual-conducting binder network induced by an electric field, and has significant technical advantages and industrialization prospects.

[0091] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A composite electrode sheet, characterized in that, The device includes a current collector and an electrode layer, wherein the electrode layer is disposed on at least one surface of the current collector; the electrode layer includes an electronically conductive component and an ionicly conductive component; the content of the electronically conductive component decreases continuously in a gradient along the thickness direction of the electrode layer from the side closer to the current collector to the side farther away from the current collector, and the content of the ionicly conductive component increases continuously in a gradient along the thickness direction of the electrode layer from the side closer to the current collector to the side farther away from the current collector.

2. The composite electrode sheet according to claim 1, characterized in that, The ratio of the average electronic conductivity within a thickness range of 0-50% from the current collector on the side closer to the current collector to the average electronic conductivity within a thickness range of 0-50% from the electrode layer surface on the side closer to the electrode layer surface is >1:1; The ratio of the average ionic conductivity within a thickness range of 0-50% from the electrode layer surface on the side closest to the electrode layer surface to the average ionic conductivity within a thickness range of 0-50% from the current collector on the side closest to the current collector is >1:

1.

3. The composite electrode sheet according to claim 1 or 2, characterized in that, The ratio of the average electronic conductivity within a thickness range of 0-20% from the current collector on the side closer to the current collector to the average electronic conductivity within a thickness range of 0-20% from the electrode layer surface on the side closer to the electrode layer surface is ≥2:1; The ratio of the average ionic conductivity within a thickness range of 0-20% from the electrode layer surface on the side closest to the electrode layer surface to the average ionic conductivity within a thickness range of 0-20% from the current collector on the side closest to the current collector is ≥2:

1.

4. The composite electrode sheet according to claim 1, characterized in that, The electrode layer comprises an electrode active material, a solid electrolyte, and a charged dual-conducting binder, wherein the charged dual-conducting binder comprises an electronically conductive component and an ionicly conductive component.

5. The composite electrode sheet according to claim 4, characterized in that, The charged dual-conducting adhesive also includes a crosslinking agent.

6. The composite electrode sheet according to claim 5, characterized in that, The crosslinking agent includes dicumyl peroxide and / or benzophenone.

7. The composite electrode sheet according to claim 1 or 4, characterized in that, The electronically conductive component includes sulfonated poly(3,4-ethylenedioxythiophene) and / or carboxylated carbon nanotubes, and the ionicly conductive component includes one or more polymers containing polar coordinating groups, or includes one or more ionicly conductive components obtained by combining a polymer containing polar coordinating groups with an electrolyte lithium salt. The polymer containing polar coordinating groups includes one or more of polyethylene oxide, polypropylene carbonate, and polytrimethylene carbonate.

8. The composite electrode sheet according to claim 7, characterized in that, The molar ratio of the polar coordinating group to lithium in the electrolyte lithium salt is (15-25):

1.

9. The composite electrode sheet according to claim 1 or 4, characterized in that, The mass ratio of the electronically conductive component to the ionicly conductive component is 1:(2-5).

10. The composite electrode sheet according to claim 4, characterized in that, The mass ratio of the electrode active material, solid electrolyte and charged dual-conducting binder is (70-80):(10-20):(1-10).

11. The composite electrode sheet according to claim 4 or 10, characterized in that, The electrode active material is a positive electrode active material, including one or more of single-crystal cobalt ternary, lithium iron phosphate, lithium cobalt oxide, and lithium-rich manganese-based materials; the solid electrolyte includes a sulfide solid electrolyte.

12. A method for preparing a composite electrode sheet as described in any one of claims 1-11, characterized in that, include: Provide electrode slurries comprising electrode active materials, solid electrolytes, and charged dual-conducting binders; An electrode layer is formed by depositing the electrode slurry on at least one surface of the current collector along the thickness direction. Before the electrode layer is completely dry, a positive power supply is placed on the current collector side and a negative power supply is placed on the surface of the electrode layer. An electric field is applied to treat the electrode layer so that the electronic conductive component in the charged dual-conductive binder migrates and accumulates on the current collector side, and the ionic conductive component in the charged dual-conductive binder migrates and accumulates on the surface of the electrode layer as the solvent evaporates. Depending on whether the electrode layer contains a crosslinking agent and the type of crosslinking agent, heat treatment, thermal initiation, or photoinitiation treatment is selected to cure the electrode layer to obtain the composite electrode sheet.

13. The preparation method according to claim 12, characterized in that, The residual solvent content of the electrode layer before electric field treatment is 20-60%.

14. The preparation method according to claim 12, characterized in that, The treatment by applying an electric field includes treatment for 5-30 minutes at a field strength of 0.1-20 V / mm and a temperature of 20-80℃.

15. The preparation method according to claim 12, characterized in that, The heat treatment includes treatment at 80-200℃ for 30-120 minutes; the thermal initiation includes treatment at 20-500℃; the photoinitiation involves irradiation with light of the appropriate wavelength and power according to the type of crosslinking agent.

16. A solid-state battery, characterized in that, It includes the composite electrode sheet as described in any one of claims 1-11, an electrode sheet with the opposite polarity to the composite electrode sheet, and an electrolyte.

17. An electrical appliance, characterized in that, Includes the solid-state battery of claim 16, wherein the secondary battery provides electrical energy to the electrical device or serves as an energy storage unit for the electrical device.

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