Porous Membrane Binder Composition for High-Shear Battery Coating
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Solution Overview
Problem
Conventional porous membranes for non-aqueous secondary batteries lack durability, especially under harsh conditions such as those encountered in electric vehicles, and suffer from poor dispersion stability under high shear forces during formation, leading to non-uniform thickness and aggregation issues.
Innovation Solution
A binder comprising a random copolymer with at least 35% alkyl (meth)acrylate and 20-65% aromatic monovinyl monomer units, along with an acidic group-containing monomer unit, is used to create a porous membrane with enhanced durability and stability under high shear, controlling the degree of swelling within a specific range to prevent moisture ingress and improve electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binders are used to form porous membranes, then the membrane can be produced with basic functionality, but the durability under harsh conditions is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by specifying a random copolymer with at least 35 mass% alkyl (meth)acrylate monomer units and at least 20 mass% but not more than 65 mass% aromatic monovinyl monomer units. This parameter optimization resolves the contradiction by achieving both durability and harsh condition performance through controlled monomer composition.
Solution Approach 2:
The patent creates a composite binder system combining alkyl (meth)acrylate monomer units providing durability with aromatic monovinyl monomer units providing harsh condition adaptability. The synergistic combination of these two monomer types in specific proportions resolves the contradiction between durability and harsh condition performance.
2Productivity
If the composition for porous membrane-use receives high shear force during gravure coating, then high-speed formation can be achieved, but aggregation of components occurs and dispersion stability deteriorates
Solution Approach 1:
The patent changes the rheological parameters of the composition by optimizing the binder's molecular structure and composition. The specific copolymer composition provides appropriate viscosity and shear-thinning characteristics that maintain dispersion stability even under high shear conditions during high-speed gravure coating.
Solution Approach 2:
The patent introduces a specifically designed copolymer binder as an intermediary substance that mediates between the non-conductive particles and the dispersion medium. This binder provides steric stabilization and prevents aggregation during high shear processing while maintaining formation speed.
3Reliability
If the degree of swelling of the particulate polymer is increased to improve durability, then the porous membrane shows better performance, but moisture ingress increases affecting electrical characteristics
Solution Approach 1:
The patent optimizes the degree of swelling parameter within the specific range of greater than a factor of 1 but not more than a factor of 2. This parameter control resolves the contradiction by achieving sufficient durability enhancement while limiting moisture absorption that would degrade electrical characteristics.
Solution Approach 2:
The patent applies local quality control by ensuring the porous membrane has appropriate swelling characteristics in the electrolysis solution environment. The binder is designed to swell to a controlled extent to provide durability while maintaining low moisture content to preserve electrical 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 solution results in a porous membrane with improved durability, stability under high shear, and enhanced electrical characteristics for non-aqueous secondary batteries, ensuring consistent performance and extended life.
Implementation Method 1
a degree of swelling of the particulate polymer with respect to a non-aqueous electrolysis solution is greater than a factor of 1 and no greater than a factor of 2
Data Source
AI summary
Provided is a binder for non-aqueous secondary battery porous membrane-use that enables formation of a porous membrane having excellent durability and that can improve stability under high shear of a composition for porous membrane-use. The binder for non-aqueous secondary battery porous membrane-use includes a particulate polymer. The particulate polymer is a random copolymer including at least 35 mass % of an alkyl (meth)acrylate monomer unit and at least 20 mass % and no greater than 65 mass % of an aromatic monovinyl monomer unit. A degree of swelling of the particulate polymer with respect to a non-aqueous electrolysis solution is greater than a factor of 1 and no greater than a factor of 2.