Acrylic Binder Separator for Li-Ion Battery Adherence and Stability
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Solution Overview
Problem
Current rechargeable lithium ion battery separators face challenges with binders that lack sufficient heat resistance and adherence, leading to unstable structures and deteriorating battery capacity during extended charge/discharge cycling.
Innovation Solution
A separator with a coating layer using a binder composed of an acrylic resin, including a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer in a specific mole ratio, along with a non-water-soluble resin and inorganic particles, enhances heat resistance and adherence, improving cycling characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF-based binder is used to maintain adherence in coating separator, then adherence between binder and inorganic particles is improved, but the structure becomes unstable due to electrolyte impregnation and lithium ion mass transfer during charge/discharge cycling
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by incorporating carboxyl group-containing polymers (such as polyacrylic acid, polyacrylamide, or carboxymethyl cellulose) in specific amounts (0.1-10 wt% based on total binder weight). This parameter change enables the binder to maintain both strong adherence to inorganic particles and structural stability during battery cycling, resolving the contradiction between adherence and stability.
Solution Approach 2:
The patent creates a composite binder system combining PVDF-based polymer with carboxyl group-containing polymer. This composite material leverages the electrochemical stability of PVDF and the strong chelating ability of carboxyl groups to form stable complexes with lithium ions and inorganic particles, simultaneously achieving adherence and structural stability during charge/discharge cycles.
2Strength
If excessive amount of PVDF-based binder is used to maintain sufficient adherence, then adherence is improved, but the coating layer structure becomes unstable due to electrolyte impregnation
Solution Approach 1:
The patent optimizes the binder composition parameters by introducing carboxyl group-containing polymers at controlled concentrations (0.1-10 wt% of total binder). This parameter optimization allows the binder to achieve sufficient adherence without requiring excessive PVDF, thereby preventing electrolyte impregnation-induced structural instability while maintaining reliable coating layer integrity during cycling.
3Temperature
If ceramic particles with high heat resistance are used to form coating layer, then heat resistance is improved, but the ceramic particles need stable maintenance inside separator during charge/discharge
Solution Approach 1:
The carboxyl group-containing polymer acts as an intermediary between the inorganic ceramic particles and the PVDF binder. The carboxyl groups form strong chelating bonds with metal ions on the ceramic particle surfaces, creating a stable intermediary layer that anchors the heat-resistant ceramic particles firmly within the separator structure during charge/discharge cycling, preventing particle displacement while maintaining heat resistance.
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 proposed separator design improves the cycling characteristics and safety of rechargeable lithium ion batteries by maintaining structural integrity and reducing thermal shrinkage, thereby enhancing the battery's cycle life and heat resistance.
Implementation Method 1
a binder including an acrylic resin, and the binder including the acrylic resin includes a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer
Implementation Method 2
the binder stably maintains the structure of the ceramic coating layer during charge and discharge of the rechargeable lithium ion battery
Data Source
AI summary
A separator for a rechargeable battery includes a substrate and a coating layer on at least one surface of the substrate, wherein the coating layer includes a binder including an acrylic resin, the binder including the acrylic resin includes a carboxyl group-containing acrylic monomer and an acrylic acid derivative monomer, and the carboxyl group-containing acrylic monomer and the acrylic acid derivative monomer are present in a mole ratio of about 20:80 to about 80:20. The binder for a rechargeable battery has high heat resistance and strong adherence, and improves the cycling characteristics of the battery.