Solid-state battery interface stress buffer layer and construction method thereof
By introducing an interface buffer and optimizing the process in solid-state batteries, a stress buffer layer is constructed, which solves the problem of interface stress accumulation caused by material mismatch, improves battery stability and cycle performance, and extends battery life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QINGDAO NEW WEISHI NEW ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2025-12-25
- Publication Date
- 2026-05-01
AI Technical Summary
During the charge-discharge cycle of solid-state batteries, the mismatch between the mechanical properties of the positive electrode active material and the sulfide solid electrolyte leads to significant accumulation of cyclic stress at the interface, which can easily cause microcracks, contact failures, and increased interface impedance, affecting battery capacity and cycle life.
An interfacial buffer is introduced into the composite cathode, and an interfacial stress buffer layer is constructed by optimizing the densification and molding process, including mechanical mixing, hot pressing, and the addition of conductive agents and binders, to form a stable buffer layer to relieve interfacial stress and inhibit crack propagation.
It significantly improves the interface stability and long-cycle performance of solid-state batteries, reduces interface impedance, enhances the mechanical stability and electrochemical compatibility of electrode materials and solid electrolytes, and extends battery life.
Abstract
Description
A stress buffer layer for solid-state battery interface and its construction method Technical Field
[0001] This invention relates to the field of electrochemical energy storage device technology, specifically to a solid-state battery interface stress buffer layer and its construction method. Background Technology
[0002] Solid-state batteries are a new type of battery system that uses solid electrolytes instead of traditional liquid electrolytes. Compared to traditional lithium-ion batteries, solid-state batteries have potential advantages such as high energy density, good safety, and long cycle life.
[0003] During battery charge-discharge cycles, positive electrode active materials such as high-nickel layered oxides undergo repeated lattice volume expansion and contraction, while sulfide solid electrolytes, as brittle ceramic materials, have limited mechanical deformation capabilities. This mismatch in mechanical properties between materials leads to significant cyclic stress accumulation at the solid-solid interface, easily causing the generation and propagation of microcracks at the interface, contact failure, and a sharp increase in interface impedance, ultimately resulting in rapid capacity decay and shortened cycle life.
[0004] To address this, a solid-state battery interface stress buffer layer and its construction method were designed. This technical solution introduces a specific interface buffer agent into the composite cathode, coupled with optimized densification and molding processes. This buffer layer effectively dissipates and redistributes interface stress during charge and discharge, suppresses interface delamination and crack initiation and propagation, thereby ensuring the long-term connectivity of ion / electron pathways and ultimately significantly improving the interface stability, structural durability, and long-cycle performance of all-solid-state batteries. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a solid-state battery interface stress buffer layer and its construction method, solving the technical problems mentioned in the background section.
[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for constructing an interfacial stress buffer layer for a solid-state battery, comprising the following steps: S1. Composite powder preparation: under an inert atmosphere, a positive electrode active material, a sulfide solid electrolyte, and an interfacial buffer are mechanically mixed to obtain a composite precursor powder; S2. Densified preform preparation: the composite precursor powder is hot-pressed to obtain a densified composite positive electrode preform; S3. Electrode material preparation: a conductive agent and a binder are added to the densified composite positive electrode preform and mixed uniformly to obtain a composite positive electrode material containing an interfacial stress buffer layer.
[0007] Preferably, in step S1, the interface buffer is a fast ion conductor material.
[0008] Preferably, the fast ion conductor material includes a lithium oxide fast ion conductor, preferably at least one of Li3PO4, Li3BO3, and Li2SiO3.
[0009] Preferably, in step S1, the mass ratio of the positive electrode active material, the sulfide solid electrolyte, and the interface buffer is (70-90):(30-10):(1-10).
[0010] Preferably, in step S2, the hot pressing treatment is isostatic pressing or unidirectional molding; preferably, the pressure of the hot pressing treatment is 100-300 MPa, the temperature is 100-250 ℃, and the time is 10-120 minutes.
[0011] Preferably, in step S3, the adhesive is a fluoropolymer; more preferably, the adhesive is polytetrafluoroethylene, and even more preferably, it is a mixture of nano-sized polytetrafluoroethylene and micron-sized polytetrafluoroethylene.
[0012] Preferably, in step S3, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, graphene, and conductive graphite.
[0013] Preferably, after step S3, the method further includes: S4. Electrode sheet forming: pressing the composite positive electrode material containing the interface stress buffer layer to obtain a composite positive electrode sheet.
[0014] A solid-state battery interface stress buffer layer is disclosed, wherein the interface stress buffer layer is distributed between the positive electrode active material and the sulfide solid electrolyte, and includes the interface buffer agent. Beneficial effects
[0015] This invention provides a solid-state battery interface stress buffer layer and its construction method. By introducing a specific interface buffer and optimizing its composite process with electrode materials and the molding process, a structurally stable interface stress buffer layer for solid-state batteries is constructed. This approach effectively alleviates the interface stress caused by volume changes during charge-discharge cycles, suppresses the generation and propagation of microcracks, and thus significantly improves the interfacial mechanical stability and electrochemical compatibility between the electrode material and the solid electrolyte. Simultaneously, this construction method promotes the optimization of ion and electron transport paths within the electrode, which is beneficial for reducing interfacial impedance and improving reaction kinetics. Detailed Implementation
[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0017] This invention provides a technical solution: a method for constructing an interfacial stress buffer layer for a solid-state battery, comprising the following steps: S1. Composite powder preparation: under an inert atmosphere, a positive electrode active material, a sulfide solid electrolyte, and an interfacial buffer are mechanically mixed to obtain a composite precursor powder; S2. Densified preform preparation: the composite precursor powder is hot-pressed to obtain a densified composite positive electrode preform; S3. Electrode material preparation: a conductive agent and a binder are added to the densified composite positive electrode preform and mixed uniformly to obtain a composite positive electrode material containing an interfacial stress buffer layer.
[0018] In this embodiment, the interface buffer is further configured to be a fast ion conductor material in step S1.
[0019] In this embodiment, the fast ion conductor material is further configured to include a lithium oxide fast ion conductor, preferably at least one of Li3PO4, Li3BO3, and Li2SiO3.
[0020] In this embodiment, the mass ratio of the positive electrode active material, the sulfide solid electrolyte and the interface buffer in step S1 is (70-90):(30-10):(1-10).
[0021] In this embodiment, the hot pressing process in step S2 is further configured to be isostatic pressing or unidirectional molding; preferably, the pressure of the hot pressing process is 100-300 MPa, the temperature is 100-250 ℃, and the time is 10-120 minutes.
[0022] In this embodiment, the adhesive in step S3 is a fluoropolymer; preferably, the adhesive is polytetrafluoroethylene, more preferably a mixture of nano-sized polytetrafluoroethylene and micron-sized polytetrafluoroethylene.
[0023] In this embodiment, the conductive agent in step S3 includes at least one of conductive carbon black, carbon nanotubes, graphene, and conductive graphite.
[0024] This embodiment is further configured such that, after step S3, it also includes: S4. Electrode sheet forming: pressing the composite positive electrode material containing the interface stress buffer layer to obtain a composite positive electrode sheet.
[0025] A solid-state battery interface stress buffer layer, wherein the interface stress buffer layer is distributed between the positive electrode active material and the sulfide solid electrolyte, and contains the interface buffer agent.
[0026] Its detailed connection method is a well-known technology in this field. The following mainly introduces the working principle and process, and the specific work is as follows.
[0027] Example: In an argon-atmospheric glove box, high-nickel ternary cathode material LiNi0.8Co0.1Mn0.1O2 (NCM811), sulfide solid electrolyte Li6PS5Cl, and interfacial buffer Li3PO4 were precisely weighed at a mass ratio of 8:2:1 and placed in a planetary ball mill jar. Zirconia grinding balls were used, with a ball-to-material ratio of 1:1, and mechanically ground and mixed at 350 rpm for 3 hours to obtain a homogeneous composite precursor powder. Subsequently, the composite powder was loaded into a flexible mold and placed in the cavity of a hot isostatic pressing (HIP) apparatus. The mixture was held at 200 MPa pressure and 170 °C for 45 minutes to allow the powder particles to achieve close contact and preliminary interfacial bonding under the synergistic effect of heat and pressure. The mixture was then cooled to room temperature at a controlled rate of 5 °C / min to obtain a dense composite cathode preform. Subsequently, the blank was crushed and sieved. Under an inert atmosphere, 2 wt% conductive carbon black and 4 wt% binder were added according to the total mass of the composite cathode material for dry mixing. The binder was pre-blended from nano-sized polytetrafluoroethylene and micron-sized polytetrafluoroethylene at a mass ratio of 1:3 to optimize the toughness and ion conduction pathway of the bonding network. After uniform mixing, the resulting composite cathode material was placed in a mold and first cold-pressed at room temperature with a pressure of 12 MPa to achieve preliminary compaction and fibrous network construction of the active material, conductive agent, and binder. Then, it was transferred to a hot press and hot-pressed at 15 MPa pressure and 90 °C for 5 minutes to promote further melting and flow of the binder and uniformly coat the particles, finally shaping a composite cathode sheet with excellent mechanical integrity and internal ion / electron dual continuous pathways. In this electrode, Li3PO4 acts as an interfacial buffer, forming a transition layer with good chemical / electrochemical stability and moderate flexibility between the positive electrode active particles and the sulfide solid electrolyte. This effectively buffers the stress generated by volume changes and interfacial side reactions during battery cycling, significantly reducing interfacial impedance and inhibiting crack initiation and propagation. The electrode obtained in this embodiment was assembled with a lithium indium alloy negative electrode and a Li6PS5Cl electrolyte layer to form a CR2032 coin cell all-solid-state battery for testing. Electrochemical performance characterization showed that, compared with the control sample without the Li3PO4 buffer layer, the battery's initial discharge specific capacity at 0.1C rate increased by approximately 12%, and the capacity retention after 200 cycles at 1C rate increased from 75% to 92%, with a significant reduction in interfacial charge transfer impedance. This demonstrates the significant effect of the stress buffer layer constructed in this invention in improving interfacial stability, enhancing mechanical integrity, and improving long-cycle performance.
[0028] It should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.
Claims
1. A method for constructing a stress buffer layer at the interface of a solid-state battery, characterized in that, Includes the following steps: S1. Composite powder preparation: Under an inert atmosphere, the positive electrode active material, sulfide solid electrolyte, and interface buffer are mechanically mixed to obtain a composite precursor powder; S2. Densified preform preparation: The composite precursor powder is hot-pressed to obtain a densified composite positive electrode preform; S3. Electrode material preparation: A conductive agent and a binder are added to the densified composite positive electrode preform and mixed evenly to obtain a composite positive electrode material containing an interface stress buffer layer.
2. The method for constructing a solid-state battery interface stress buffer layer according to claim 1, characterized in that... In step S1, the interface buffer is a fast ion conductor material.
3. The method for constructing a solid-state battery interface stress buffer layer according to claim 2, characterized in that... The fast ion conductor material includes lithium oxide fast ion conductors, preferably at least one of Li3PO4, Li3BO3, and Li2SiO3.
4. The method for constructing a solid-state battery interface stress buffer layer according to claim 1, characterized in that... In step S1, the mass ratio of the positive electrode active material, the sulfide solid electrolyte and the interface buffer is (70-90):(30-10):(1-10).
5. The method for constructing a solid-state battery interface stress buffer layer according to claim 1, characterized in that... In step S2, the hot pressing treatment is an isostatic pressing treatment or a unidirectional molding treatment; preferably, the pressure of the hot pressing treatment is 100-300 MPa, the temperature is 100-250 ℃, and the time is 10-120 minutes.
6. The method for constructing a solid-state battery interface stress buffer layer according to claim 1, characterized in that... In step S3, the adhesive is a fluoropolymer; preferably, the adhesive is polytetrafluoroethylene, more preferably a mixture of nano-sized polytetrafluoroethylene and micron-sized polytetrafluoroethylene.
7. The method for constructing a solid-state battery interface stress buffer layer according to claim 1, characterized in that... In step S3, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, graphene, and conductive graphite.
8. The method for constructing a solid-state battery interface stress buffer layer according to claim 1, characterized in that... Step S3 is followed by: S4. Electrode sheet forming: The composite positive electrode material containing the interface stress buffer layer is pressed to obtain a composite positive electrode sheet.
9. A stress buffer layer for solid-state battery interfaces, characterized in that, It is constructed by the method according to any one of claims 1 to 8; the interfacial stress buffer layer is distributed between the positive electrode active material and the sulfide solid electrolyte, and contains the interfacial buffer.