Separator with PAA Binder for Thermal Stability
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Solution Overview
Problem
Secondary battery separators face challenges with heat resistance and thermal shrinkage, which can lead to internal short circuits and reduced stability during high-temperature charging/discharging.
Innovation Solution
A separator with a porous base layer and a coating layer containing inorganic particles and a binder, such as polyacrylic acid or sodium polyacrylate, is developed, providing improved dispersibility and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional separator is used, then the battery can be manufactured with standard materials, but the separator exhibits poor heat resistance and thermal shrinkage at high temperatures
Solution Approach 1:
The separator is constructed as a composite material consisting of a polyolefin base layer combined with a coating layer containing inorganic particles (alumina, silica, boehmite) dispersed in a binder resin. This composite structure provides both the mechanical properties of the base layer and the thermal stability of the inorganic coating layer, preventing thermal shrinkage while maintaining heat resistance.
Solution Approach 2:
The separator utilizes a porous structure with controlled porosity (30-80%) in both the base layer and coating layer. The porous base layer allows efficient ion transport, while the porous coating layer provides thermal stability without blocking ion flow. The pore size is controlled at 0.01-10 μm to balance ion conductivity and thermal resistance.
2Temperature
If the separator thickness is increased to improve thermal stability, then heat resistance improves, but the battery internal resistance increases and energy efficiency decreases
Solution Approach 1:
The separator applies local quality by concentrating the thermal stability function in a thin coating layer (1-20 μm) on the surface of the base layer, rather than increasing the overall thickness. The coating layer contains high thermal stability inorganic particles locally where heat resistance is needed, while the bulk of the separator maintains thin dimensions (15-50 μm) for low ion transport resistance and high energy efficiency.
3Temperature
If a coating layer is added to improve heat resistance, then thermal properties improve, but the manufacturing process becomes more complex
Solution Approach 1:
The manufacturing process merges the coating application with the base layer formation by using a slurry coating method where the coating layer is applied as a liquid slurry containing inorganic particles and binder, then dried and sintered in one integrated process. This combining of steps simplifies manufacturing compared to applying pre-formed ceramic coatings or multiple separate coating processes.
4Temperature
If inorganic particles are used in the coating layer to improve thermal stability, then heat resistance improves, but the dispersibility of particles becomes challenging
Solution Approach 1:
The patent uses a binder resin as an intermediary substance to disperse and bind the inorganic particles in the coating layer. The binder resin creates a matrix that holds the inorganic particles (alumina, silica, boehmite) in uniform distribution, preventing particle aggregation and ensuring consistent thermal stability throughout the coating layer while maintaining structural integrity.
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 enhances the mechanical and thermal properties of the separator, reducing thermal shrinkage and preventing internal short circuits, thereby ensuring the safety and cycle life of secondary batteries.
Implementation Method 1
the binder includes one selected from the group consisting of polyacrylic acid (PAA), polyacrylate or a mixture of polyacrylic acid (PAA) and polyacrylate
Implementation Method 2
providing improved dispersibility and thermal stability... reducing thermal shrinkage
Data Source
AI summary
Provided are a separator having high heat resistance, a manufacturing method thereof and a secondary battery including the separator, which provides excellent dispersibility and reduced thermal shrinkage. The separator includes separator includes a porous base layer, and a coating layer formed on at least one surface of the base layer, wherein the coating layer includes inorganic particles and a binder, and the binder includes one selected from the group consisting of polyacrylic acid (PAA), polyacrylate or a mixture of polyacrylic acid (PAA) and polyacrylate, having a molecular weight of 100,000 to 1,000,000, as a first binder.