Lithium Ion Battery Separator Resin Binder Control
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving both high safety and high-rate characteristics due to the limitations of porous films used as separators, which struggle to maintain sufficient lithium ion conductivity while ensuring heat resistance and strength, often leading to internal short circuits and thermal runaway issues.
Innovation Solution
A lithium ion secondary battery design that incorporates a porous film with a controlled resin binder content of 1.5 to 8 parts by weight per 100 parts of filler, featuring an acrylonitrile, acrylate, or methacrylate unit resin binder, and a specific pore size distribution to enhance lithium ion conductivity and stress tolerance, while minimizing resin binder usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If resin binder content is increased to improve strength and prevent short circuits, then safety improves, but lithium ion conductivity and high-rate characteristics deteriorate
Solution Approach 1:
The patent precisely controls the resin binder content parameter within 1.5 to 8 parts by weight per 100 parts of filler. This optimized range ensures sufficient strength to prevent short circuits while maintaining adequate porosity for high-rate lithium ion transport, thus resolving the contradiction between strength and high-rate characteristics.
Solution Approach 2:
The patent creates a porous structure with specific local pore size distribution (0.02 to 0.09 μm) that provides both mechanical strength and ion transport pathways. The localized porous architecture allows the film to be strong enough to prevent short circuits while maintaining channels for rapid lithium ion movement, resolving the contradiction between strength and high-rate performance.
2Reliability
If microporous membrane separator is used to achieve electronic insulation, then safety improves, but heat resistance deteriorates due to shrinkage at low temperature
Solution Approach 1:
The patent replaces conventional organic microporous membrane separators with a composite porous film consisting of inorganic filler particles (such as alumina) dispersed in a resin binder matrix. This inorganic-based composite structure provides both electronic insulation and superior heat resistance, eliminating the shrinkage problem of organic membranes while maintaining safety functions.
Solution Approach 2:
The patent fundamentally changes the material composition parameter from organic polymer-based membranes to inorganic filler-based porous films. This material parameter change transforms the thermal properties, providing heat resistance while maintaining the electronic insulation and safety functions of the separator.
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 battery achieves balanced heat resistance, necessary strength, and high-rate characteristics, reducing the risk of internal short circuits and thermal runaway, thereby improving safety and reliability.
Implementation Method 1
a porous film which includes a filler and a resin binder and is adhered to a surface of at least one of a positive electrode and a negative electrode
Implementation Method 2
a porous film including a filler and a resin binder, and adhered to a surface of at least one of a positive electrode and a negative electrode
Data Source
AI summary
A lithium ion secondary battery includes a positive electrode capable of absorbing and desorbing lithium ion, a negative electrode capable of absorbing and desorbing lithium ion, a porous film interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte: the porous film being adhered to a surface of at least one of the positive electrode and the negative electrode; the porous film including a filler and a resin binder; the resin binder content in the porous film being 1.5 to 8 parts by weight per 100 parts by weight of the filler; and the resin binder including an acrylonitrile unit, an acrylate unit, or a methacrylate unit.