A pencil-coating-based solid-state battery self-buffer interface structure, a preparation method thereof, and applications thereof

Abstract

The application discloses a pencil-coating-based self-buffering interface structure of a solid-state battery, which is a graphite-based composite thin layer formed by pencil friction coating, wherein the graphite-based composite thin layer is in a discontinuous porous form, the surface resistance of the graphite-based composite thin layer is 10 Ω / sq-10 kΩ / sq, and the coating coverage of the graphite-based composite thin layer is 30%-80%. The application uses a single step of pencil coating to in-situ construct a unique multifunctional interface layer, and the discontinuous porous structure of the interface layer synchronously realizes three functions of electronic seepage conduction, lithium ion transmission across the interface and stress elastic buffering, thereby fundamentally and cooperatively solving the electric-ion-force transmission contradiction of the interface of the solid-state battery, and the interface engineering can be completed only by using a drawing pencil, the material cost is negligible, the process operation is simple and has good repeatability, and the process is easy to integrate in large-scale production.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, specifically to a solid-state battery self-buffered interface structure based on pencil coating, its preparation method, and its application. Background Technology

[0002] All-solid-state lithium-ion batteries are considered an important direction for the development of next-generation energy storage technology due to their high safety and high energy density potential. However, their industrialization faces two major bottlenecks: First, the poor solid-solid interface contact between the solid electrolyte and the electrodes, especially between the solid electrolyte and the positive electrode, leads to extremely high interfacial impedance and severe electrochemical polarization; Second, in order to maintain close interfacial contact during cycling, the battery must operate under high external pressure of several megapascals to tens of megapascals, which requires a complex and bulky pressurization system, seriously impairing the energy density, reliability, and cost of the battery system.

[0003] In existing technologies, conductive layers such as metals, graphene, or pyrolytic carbon materials are often introduced into the interface to solve the interfacial impedance problem. However, most of these conductive layer introduction methods form dense and continuous thin films, which, while providing electronic pathways, severely hinder the cross-interface transport of lithium ions. Furthermore, due to their rigidity, they cannot buffer changes in electrode volume, thus exacerbating the dependence on high external pressure. Therefore, developing a simple interface engineering technology that can simultaneously take into account mixed electron / ion conduction, possess intrinsic elasticity, and significantly reduce the battery operating pressure requirements has significant theoretical and applied value. To this end, we propose a solid-state battery self-buffered interface structure based on pencil coating, its preparation method, and its application. Summary of the Invention

[0004] The purpose of this invention is to provide a solid-state battery self-buffered interface structure based on pencil coating, its preparation method, and its application, so as to solve the problems that need to be solved in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a solid-state battery self-buffering interface structure based on pencil coating, wherein the solid-state battery self-buffering interface structure based on pencil coating is a graphite-based composite thin layer formed by friction coating with a drawing pencil, the graphite-based composite thin layer is a discontinuous porous morphology, the surface resistivity of the graphite-based composite thin layer is 10Ω / sq-10kΩ / sq, and the coating coverage of the graphite-based composite thin layer is 30%-80%.

[0006] In existing technologies, conductive layers such as metals, graphene, or pyrolytic carbon materials are often introduced at the interface to solve the interfacial impedance problem. However, most of these conductive layer introduction methods form dense, continuous films, which, while providing electronic pathways, severely hinder the cross-interface transport of lithium ions. Furthermore, due to their rigidity, they cannot buffer changes in electrode volume, thus exacerbating dependence on high external pressure. Therefore, developing a simple interface engineering technology that can simultaneously achieve mixed electron / ion conduction, possess intrinsic elasticity, and significantly reduce battery operating pressure requirements has significant theoretical and applied value. The graphite-based composite thin layer in this invention has a sheet resistance range of 10Ω / sq-10kΩ / sq, ensuring sufficient electronic conductivity while avoiding the formation of a dense, continuous conductive film. This effectively reduces the interfacial contact impedance between the solid electrolyte and the electrode, improving battery rate performance. Because this thin layer is discontinuous, porous, and covers… With an efficiency controlled between 30% and 80%, it provides an electron permeation network while retaining a large number of open pores, offering a low-resistance pathway for lithium-ion cross-interface migration and avoiding the shielding effect of traditional dense carbon layers on ion transport. The three-dimensional network structure composed of graphite microcrystals and clay or amorphous carbon binder phases has a certain degree of flexibility and compressibility. During battery charging and discharging, it can absorb the interfacial stress caused by electrode volume changes through microstructure elastic deformation, dynamically maintaining tight electrical contact and reducing contact failure during cycling. Moreover, this functional interface can be constructed in situ by directly using commercially available drawing pencils for friction coating, without the need for vacuum equipment, high-temperature treatment, or complex slurry preparation, greatly simplifying the manufacturing process and making it suitable for large-scale production. Furthermore, by selecting pencils of different hardness, the ratio of graphite to binder phase can be adjusted, thereby precisely controlling the conductivity, porosity, coverage, and mechanical properties of the thin layer to meet the needs of different solid-state battery systems.

[0007] As a further description of the above technical solution:

[0008] The graphite-based composite thin layer comprises graphite microcrystals and a binder phase.

[0009] As a further description of the above technical solution:

[0010] The binder phase is made of one or a combination of clay or amorphous carbon.

[0011] As a further description of the above technical solution:

[0012] The method for preparing a solid-state battery self-buffered interface structure based on pencil coating includes the following steps:

[0013] Step 1: Select a solid electrolyte substrate;

[0014] Step 2: Select a drawing pencil with a hardness rating of 6H-6B and apply a pressure of 0.2N-5N to the solid electrolyte substrate for coating. The coating is applied 1-50 times to form a solid battery self-buffering interface structure based on pencil coating.

[0015] As a further description of the above technical solution:

[0016] The pencil-coated solid-state battery self-buffering interface structure is applied to a composite solid-state electrolyte assembly, including a solid electrolyte matrix and a pencil-coated solid-state battery self-buffering interface structure formed by a preparation method.

[0017] As a further description of the above technical solution:

[0018] The pencil-coated solid-state battery self-buffering interface structure is applied to an all-solid-state lithium-ion battery. The all-solid-state lithium-ion battery includes a solid electrolyte layer and a positive electrode. The solid electrolyte layer and the positive electrode are coated with a pencil-coated solid-state battery self-buffering interface structure formed by the preparation method of the pencil-coated solid-state battery self-buffering interface structure.

[0019] As a further description of the above technical solution:

[0020] The all-solid-state lithium-ion battery operates under a constant external pressure of less than 2 MPa.

[0021] As a further description of the above technical solution:

[0022] The all-solid-state lithium-ion battery operates under a constant external pressure of less than 0.5 MPa.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This invention utilizes a single step of drawing pencil coating to construct a unique multifunctional interface layer in situ. Its discontinuous porous structure simultaneously realizes three major functions: electron permeation conduction, lithium-ion cross-interface transport, and stress elastic buffering. It fundamentally and synergistically solves the contradiction of electro-ion-force transport at the solid-state battery interface. Moreover, the interface engineering can be completed using only a drawing pencil, the material cost is negligible, the process is simple to operate, has good repeatability, is easy to integrate in large-scale production, and has extremely high commercialization potential.

[0025] 2. The solid-state battery self-buffered interface structure based on pencil coating has excellent elasticity and self-adaptability, and can continuously compensate for interface stress during cycling. Therefore, it can greatly reduce or even eliminate the battery's need for an external high-voltage system. This simplifies the packaging design of the solid-state battery module, which is conducive to significantly improving the overall energy density, reliability and production efficiency of the system, and reducing system costs.

[0026] 3. By selecting drawing pencils of different hardness, pressure, and coating times, the conductivity, porosity, thickness, and elasticity of the interface layer can be precisely controlled, thereby optimizing the interface performance for different battery systems and obtaining stable and excellent electrochemical performance.

[0027] 4. By using a specific process of coating with a drawing pencil, the graphite sheets are peeled and transferred under the action of shear friction, and combined with the spacing effect of the binder phase, a discontinuous porous elastic network is naturally formed. This structure is not pre-designed, but it does meet the multifunctional requirements of the solid-state battery interface. The graphite sheets construct electronic pathways, the pores ensure ion transport, and the weakly connected sheet network provides elasticity. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] This invention provides a technical solution: a solid-state battery self-buffering interface structure based on pencil coating. The solid-state battery self-buffering interface structure based on pencil coating is a graphite-based composite thin layer formed by friction coating with a drawing pencil. The graphite-based composite thin layer has a discontinuous porous morphology, a surface resistivity of 10Ω / sq-10kΩ / sq, and a coating coverage of 30%-80%. The graphite-based composite thin layer includes graphite microcrystals and a binder phase. The graphite microcrystals and the binder phase form a three-dimensional network. The binder phase is manufactured from one or a combination of clay and amorphous carbon.

[0031] The graphite-based composite thin layer features a sheet resistance ranging from 10 Ω / sq to 10 kΩ / sq. This ensures sufficient electronic conductivity while avoiding the formation of a dense, continuous conductive film, effectively reducing the interfacial contact impedance between the solid electrolyte and the electrode, and improving the battery's rate performance. Because this thin layer is discontinuous and porous, with a coverage rate controlled between 30% and 80%, it provides an electron permeation network while retaining a large number of open pores, offering a low-resistance pathway for lithium-ion cross-interface migration. This avoids the shielding effect of traditional dense carbon layers on ion transport. Furthermore, the three-dimensional network structure composed of graphite microcrystals and clay or amorphous carbon binders... The structure possesses a certain degree of flexibility and compressibility. During battery charging and discharging, it can absorb the interfacial stress caused by changes in electrode volume through elastic deformation of the microstructure, dynamically maintain tight electrical contact, and reduce contact failure during cycling. Moreover, the functional interface can be constructed in situ by directly using commercially available drawing pencils for friction coating, without the need for vacuum equipment, high-temperature treatment, or complex slurry preparation, which greatly simplifies the manufacturing process and makes it suitable for large-scale production. Furthermore, by selecting pencils of different hardness, the ratio of graphite to binder phase can be adjusted, thereby precisely controlling the conductivity, porosity, coverage, and mechanical properties of the thin layer to meet the needs of different solid-state battery systems.

[0032] During the coating process, the graphite microcrystals in the pencil lead are sheared and transferred to the surface of the solid electrolyte. When the coverage reaches more than 30%, these flake graphites form an electron permeation network through point-to-point or edge-to-surface contact, achieving effective in-plane electron conduction and meeting the electron supply requirements of the positive electrode active material. Since the coating is a discontinuous structure and the coverage does not exceed 80%, a large number of exposed areas or micron-sized pores are still retained on the surface of the solid electrolyte, allowing lithium ions to migrate directly between the electrolyte and the electrode through these open channels, avoiding being blocked by the dense carbon layer, thereby maintaining a high interfacial ionic conductivity. The binder phase made of clay or amorphous carbon not only adheres the graphite flakes to the substrate, but also serves as a flexible connector to connect each graphite unit, giving the entire network a certain compressive resilience. During battery cycling, when the positive electrode material expands or contracts in volume due to lithium insertion or extraction, this interfacial layer can absorb stress through local deformation, preventing interfacial peeling or contact deterioration, and achieving a "self-buffering" function.

[0033] Example 2:

[0034] The method for preparing a solid-state battery self-buffered interface structure based on pencil coating includes the following steps:

[0035] Step 1: Select a solid electrolyte substrate;

[0036] Step 2: Select a drawing pencil with a hardness rating of 6H-6B and apply a pressure of 0.2N-5N to the solid electrolyte substrate for coating. The coating is applied 1-50 times to form a solid battery self-buffering interface structure based on pencil coating.

[0037] The aforementioned manufacturing method can complete the interface construction simply by manually or mechanically rubbing a drawing pencil onto the surface of a solid electrolyte. It eliminates the need for complex processes and expensive equipment such as vacuum sputtering, chemical vapor deposition, slurry coating, or high-temperature sintering, significantly lowering the manufacturing threshold. By adjusting the hardness of the drawing pencil, the applied pressure, and the number of coatings, the thickness, coverage, sheet resistance, and porosity of the formed interface layer can be precisely controlled, thereby adapting to the requirements of different solid-state battery systems for interface conductivity, ion permeability, and mechanical properties. Moreover, this preparation method is a dry process that does not use organic solvents or generate waste liquid or waste gas. Furthermore, the solid-state battery self-buffered interface structure prepared by this method based on pencil coating is applicable to the surfaces of various oxide-based solid electrolytes and can be completed quickly at room temperature without damaging the substrate. It is easy to integrate into existing battery assembly processes. This simple coating process naturally forms a functional interface layer with discontinuous, porous, and elastic three-dimensional network characteristics, realizing the three major functions of electron conduction, ion permeation, and stress buffering in one step.

[0038] Example 3:

[0039] The pencil-coated solid-state battery self-buffering interface structure is applied to a composite solid-state electrolyte assembly, including a solid electrolyte matrix and a pencil-coated solid-state battery self-buffering interface structure formed by a preparation method.

[0040] The pencil-coated solid-state battery self-buffering interface structure is applied to an all-solid-state lithium-ion battery. The all-solid-state lithium-ion battery includes a solid electrolyte layer and a positive electrode. The solid electrolyte layer and the positive electrode are coated with a pencil-coated solid-state battery self-buffering interface structure formed by the preparation method of the pencil-coated solid-state battery self-buffering interface structure.

[0041] The all-solid-state lithium-ion battery operates under a constant external pressure of less than 2 MPa.

[0042] The all-solid-state lithium-ion battery operates under a constant external pressure of less than 0.5 MPa.

[0043] By introducing the self-buffered interface structure between the solid electrolyte and the positive electrode, the all-solid-state lithium-ion battery can achieve stable cycling under a constant external pressure of less than 2 MPa, or even as low as 0.5 MPa, which is far lower than the 5-30 MPa pressure required by traditional oxide-based solid-state batteries. Since there is no need for bulky high-pressure clamps or complex pressurization mechanisms, the battery packaging structure can be greatly simplified, effectively improving the volumetric and weight energy density. It is more suitable for applications such as portable electronic devices, electric vehicles, and flexible energy storage. Under low pressure, the interface structure can still maintain close contact between the electrode or electrolyte through its own elastic deformation, effectively suppressing interface debonding, impedance growth, and capacity decay caused by cyclic stress, significantly extending battery life. Moreover, the composite solid electrolyte component can be integrated into the standard battery assembly line through a simple coating process without major modifications to the existing production line, and has good potential for industrial application.

[0044] Moreover, the coating coverage is controlled at 30%–80%, ensuring that the graphite sheets form a percolation network to conduct electrons while retaining sufficient exposed solid electrolyte areas or channels for direct lithium-ion migration. This discontinuous yet functionally complete design breaks through the traditional dense conductive layer's obstruction of ion transport, achieving efficient co-transport of electrons and ions at the interface. During the charging and discharging process of the cathode material, volume changes occur, which can easily lead to cracking or peeling of rigid interfaces. However, by utilizing the weakly connected sheet structure and the flexibility of the binder phase, local strain can be absorbed, and the interface morphology can be dynamically adjusted, thereby maintaining low-impedance electrical contact continuously through hundreds of cycles. Since the interface itself has buffering capacity, the battery no longer relies on external mechanical pressure to maintain performance, achieving a dual breakthrough of internalized interface function and simplified system structure, fundamentally changing the design paradigm of solid-state batteries.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A solid-state battery self-buffering interface structure based on pencil coating, characterized in that: The solid-state battery self-buffered interface structure based on pencil coating is a graphite-based composite thin layer formed by friction coating with a drawing pencil. The graphite-based composite thin layer has a discontinuous porous morphology, a surface resistivity of 10Ω / sq-10kΩ / sq, and a coating coverage of 30%-80%.

2. The solid-state battery self-buffering interface structure based on pencil coating according to claim 1, characterized in that: The graphite-based composite thin layer comprises graphite microcrystals and a binder phase.

3. The solid-state battery self-buffering interface structure based on pencil coating according to claim 2, characterized in that: The binder phase is made of one or a combination of clay or amorphous carbon.

4. A method for preparing a solid-state battery self-buffering interface structure based on pencil coating, applicable to the solid-state battery self-buffering interface structure based on pencil coating as described in claims 1-3, characterized in that: The method for preparing a solid-state battery self-buffered interface structure based on pencil coating includes the following steps: Step 1: Select a solid electrolyte substrate; Step 2: Select a drawing pencil with a hardness rating of 6H-6B and apply a pressure of 0.2N-5N to the solid electrolyte substrate for coating. The coating is applied 1-50 times to form a solid battery self-buffering interface structure based on pencil coating.

5. An application of a solid-state battery self-buffering interface structure based on pencil coating, applicable to the preparation method of a solid-state battery self-buffering interface structure based on pencil coating as described in claim 4, characterized in that: The pencil-coated solid-state battery self-buffering interface structure is applied to a composite solid-state electrolyte assembly, comprising a solid electrolyte matrix and a pencil-coated solid-state battery self-buffering interface structure formed by the preparation method of the pencil-coated solid-state battery self-buffering interface structure as described in claim 4.

6. An application of a solid-state battery self-buffering interface structure based on pencil coating, applicable to the preparation method of a solid-state battery self-buffering interface structure based on pencil coating as described in claim 4, characterized in that: The pencil-coated solid-state battery self-buffering interface structure is applied to an all-solid-state lithium-ion battery, which includes a solid electrolyte layer and a positive electrode. The solid electrolyte layer and the positive electrode are coated with a pencil-coated solid-state battery self-buffering interface structure formed by the preparation method of the pencil-coated solid-state battery self-buffering interface structure as described in claim 4.

7. The application of the solid-state battery self-buffering interface structure based on pencil coating according to claim 6, characterized in that: The all-solid-state lithium-ion battery operates under a constant external pressure of less than 2 MPa.

8. The application of the solid-state battery self-buffering interface structure based on pencil coating according to claim 6, characterized in that: The all-solid-state lithium-ion battery operates under a constant external pressure of less than 0.5 MPa.