Solid Electrolyte Membrane Binder Composition for Crack-Free Densification
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Solution Overview
Problem
The brittleness of solid electrolyte membranes increases during the densification process in large-area and mass production, leading to microcracks and fractures, which affect the battery cell assembly process.
Innovation Solution
A solid electrolyte membrane is developed using a high-molecular-weight polymer binder and a low-molecular-weight non-polar liquid rubber as a plasticizer, improving the membrane's flexibility and reducing the occurrence of microcracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the solid electrolyte membrane is subjected to pressing and drying processes to increase density, then the density of the membrane is improved, but the brittleness of the solid electrolyte rapidly increases, resulting in microcracks or fractures
Solution Approach 1:
The invention uses a composite binder system comprising both a polymer binder and an elastomer binder in combination with a plasticizer. The polymer binder provides structural integrity while the elastomer binder and plasticizer maintain flexibility during pressing. This composite material approach allows the solid electrolyte membrane to achieve high density through pressing without developing microcracks or fractures, as the elastomer component absorbs stress and prevents brittle failure.
Solution Approach 2:
The invention modifies the physical and chemical parameters of the binder system by selecting specific molecular weight ranges for the polymer binder (75,000-1,000,000 g/mol) and elastomer binder (2,000-75,000 g/mol), along with controlling the plasticizer viscosity (1-100,000 cps). These parameter optimizations ensure the binder maintains appropriate viscoelastic properties during pressing and drying, enabling high density achievement while preventing brittleness-induced cracking.
2Strength
If a high-molecular-weight polymer binder is used to improve membrane strength, then the bending strength is improved, but the flexibility of the membrane may be reduced
Solution Approach 1:
The invention merges two types of binders with complementary properties: a high-molecular-weight polymer binder (75,000-1,000,000 g/mol) that provides bending strength and structural integrity, and a low-molecular-weight elastomer binder (2,000-75,000 g/mol) that provides flexibility and elasticity. This combination allows the membrane to simultaneously achieve high bending strength and sufficient flexibility for handling and densification without compromising either property.
Solution Approach 2:
The invention introduces a plasticizer as an intermediary substance with viscosity of 1-100,000 cps that mediates between the rigid polymer binder and the flexible elastomer binder. The plasticizer fills spaces between binder molecules and electrolyte particles, lubricating the matrix to enhance flexibility while allowing the high-molecular-weight polymer to maintain its strength-providing function. This intermediary enables the coexistence of strength and flexibility in the binder system.
Data Source
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AI summary
A solid electrolyte membrane includes a solid electrolyte, a high-molecular-weight polymer binder having a weight average molecular weight of about greater than 75,000 gram/mole (g/mol) but less than or equal to 1,000,000 g/mol, and a low-molecular-weight non-polar liquid rubber (non-polar elastomer), wherein the low-molecular-weight non-polar liquid rubber has a weight average molecular weight of about 2,000 g/mol to about 75,000 g/mol, and a viscosity of about 1 centipoises (cps) to about 100,000 cps. An all-solid-state secondary battery includes the solid electrolyte membrane.