Solid Electrolyte Free-Standing Membrane Without Solvent Binders
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Solution Overview
Problem
Sulfide-based solid electrolytes in all-solid-state batteries suffer from poor mechanical properties and processability, leading to difficulties in mass production and reduced lithium ion conductivity due to the use of solvents and separators, which can compromise battery stability and performance.
Innovation Solution
A method involving the mixing of sulfide-based solid electrolyte powder with fibrillizable polymer powder, applying shear stress to fibrillize the polymer, and rolling the mixture to form a free standing membrane without a solvent, optimizing the polymer content and processing conditions to enhance mechanical strength and ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfide-based solid electrolyte is used to achieve high lithium ion conductivity, then lithium ion conductivity is improved, but mechanical properties deteriorate
Solution Approach 1:
The patent uses composite materials by combining sulfide-based solid electrolyte particles with polymer binder particles to create a free-standing membrane that maintains high lithium ion conductivity while improving mechanical properties. The composite structure allows the sulfide particles to provide ionic conductivity pathways while the polymer matrix provides mechanical strength and flexibility.
2Reliability
If sulfide-based solid electrolyte is processed in powder form to achieve high density, then lithium ion conductivity is improved, but processability deteriorates
Solution Approach 1:
The patent creates a composite material where sulfide-based solid electrolyte particles are dispersed in a polymer matrix, enabling the processing of free-standing membranes through conventional techniques like pressing and lamination. This composite approach maintains high density and ionic conductivity while dramatically improving processability for mass production.
Solution Approach 2:
The polymer binder acts as an intermediary material that facilitates the processing of sulfide-based solid electrolyte. It enables the powder to be formed into handleable free-standing membranes while maintaining the electrochemical performance of the sulfide particles.
3Ease of manufacture
If separator is added to coating method for mass production, then ease of manufacture is improved, but lithium ion conductivity deteriorates
Solution Approach 1:
The patent extracts the separator function from the traditional coating method by incorporating binding agents directly into the solid electrolyte membrane formulation. This eliminates the need for a separate separator layer, maintaining high lithium ion conductivity while enabling mass production through conventional coating techniques.
Solution Approach 2:
The patent merges the functions of the solid electrolyte and separator into a single free-standing membrane by incorporating polymer binder particles within the membrane structure. This unified structure provides both ionic conductivity and mechanical separation functions, eliminating the need for additional separator layers.
4Strength
If binder dissolved in solvent is used for free standing membrane, then mechanical strength is improved, but lithium ion conductivity deteriorates
Solution Approach 1:
The patent changes the physical state of the binder from dissolved (in solvent-based methods) to particulate form. The binder particles are dispersed throughout the solid electrolyte matrix, providing mechanical strength through particle-particle and particle-matrix interactions while minimizing interference with ionic conductivity pathways.
Solution Approach 2:
The patent uses a minimal amount of polymer binder (1-10 wt%) as a sacrificial component that provides necessary mechanical strength during processing and operation but does not significantly impede lithium ion transport. The low concentration ensures the binder serves its structural function without compromising electrochemical performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting solid electrolyte membrane achieves improved tensile strength and lithium ion conductivity, exceeding 0.2 MPa and 3 mS/cm respectively, while maintaining the advantages of high lithium ion conductivity and stability, facilitating mass production and enhancing battery performance.
Implementation Method 1
applying shear stress to the mixture to fibrillize the fibrillizable polymer powder
Data Source
AI summary
A method for preparing a solid electrolyte free standing membrane involves mixing sulfide-based solid electrolyte powder with fibrillizable polymer powder to produce a mixture, applying shear stress to fibrillize the polymer, and rolling the mixture to form the membrane. The process parameters include performing the shear stress application for 3 to 25 minutes at 20° C. to 125° C., and rolling for 3 to 25 minutes at 38° C. to 125° C. The mixture contains 0.06% to 0.6% fibrillizable polymer by weight. Specific variations include using polymer powders with average diameters from 1 μm to 1,000 μm, performing the mixing step without solvent, and selecting polymer types such as PTFE. Additionally, the method details the conditions for shear stress application and rolling, as well as the resultant polymer diameters and mixture consistency. The resulting solid electrolyte free standing membrane, comprising sulfide-based solid electrolyte and fibrillized polymer, demonstrates tensile strengths of at least 0.2 MPa and lithium ion conductivity of at least 3 mS/cm. This membrane is particularly suitable for use in all-solid-state batteries.