IPN Acrylic Binder for Rechargeable Battery Separator
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Solution Overview
Problem
Current binders for rechargeable lithium ion batteries fail to provide sufficient heat resistance and adherence to both porous polyethylene and inorganic particles, leading to structural changes in the coating layer during charge and discharge cycles, which deteriorates battery capacity.
Innovation Solution
A binder comprising an interpenetrating polymer network (IPN)-type acrylic-based resin with a hard segment having a glass transition temperature of 50° C to 200° C and a soft segment with a glass transition temperature of -100° C to 30° C, along with specific Hildebrand solubility parameters, is used to enhance heat resistance and adherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF-based binder is used to maintain sufficient adherence, then adherence to inorganic particles is improved, but excessive amount is needed and stable structure maintenance during charge-discharge cycles deteriorates
Solution Approach 1:
The invention uses a composite binder system combining PVDF-based polymer with polyacrylic acid and silane coupling agent. This composite approach creates synergistic effects where PVDF provides baseline adherence, polyacrylic acid enhances bonding to inorganic particles through carboxyl groups, and silane coupling agent forms chemical bridges between the polymer matrix and ceramic particles, achieving strong adherence with reduced binder quantity while maintaining structural stability during cycling
Solution Approach 2:
The silane coupling agent acts as an intermediary substance that chemically bonds to both the PVDF-based polymer matrix and the inorganic ceramic particles. This intermediary creates strong interfacial adhesion, allowing the binder to firmly hold ceramic particles without requiring excessive PVDF content, thereby maintaining coating layer integrity during charge-discharge cycles
2Temperature
If high heat-resistance ceramic particles are used, then high voltage and high-capacity characteristics are achieved, but structural stability inside separator deteriorates without sufficient binder performance
Solution Approach 1:
The binder system forms a composite matrix that encapsulates and protects high heat-resistance ceramic particles. The combination of PVDF, polyacrylic acid, and silane coupling agent creates a thermally stable network that maintains the structural integrity of ceramic particles at high temperatures while ensuring their stable integration within the separator during battery operation
Solution Approach 2:
The invention modifies the chemical and physical parameters of the binder system by introducing polyacrylic acid with specific carboxyl group content and silane coupling agents with controlled molecular structures. These parameter changes enhance the binder's thermal stability and bonding strength, enabling it to maintain coating layer structure at elevated temperatures where high heat-resistance ceramic particles operate
3Reliability
If binder amount is reduced to improve cycle characteristics, then coating layer stability is improved, but adherence to porous polyethylene and inorganic particles deteriorates
Solution Approach 1:
The composite binder system allows reduction of total binder content while maintaining or improving adherence. The synergistic combination of PVDF, polyacrylic acid, and silane coupling agent creates efficient bonding at lower concentrations, as each component contributes specific adhesive mechanisms that complement each other, reducing the need for excessive binder material
Solution Approach 2:
The invention changes the chemical composition parameters of the binder to achieve higher bonding efficiency. By controlling the weight ratios of PVDF to polyacrylic acid and optimizing silane coupling agent content, the system achieves strong adherence with reduced binder quantity, improving cycle characteristics while maintaining sufficient bonding strength
Data Source
AI summary
A binder for a rechargeable battery includes an IPN-type acrylic-based resin including a hard segment having a glass transition temperature ranging from greater than or equal to about 50° C. and less than equal to about 200° C. and a soft segment having a glass transition temperature in a range of greater than or equal to about −100° C. and less than or equal to about 30° C.