Separator Surface Layer Design for Battery Oxidation Resistance
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Solution Overview
Problem
Current separators for lithium ion secondary batteries, particularly those with polyolefin microporous films, lack sufficient oxidation resistance and heat resistance, which can lead to electrode deterioration due to the expansion of alloy-based negative electrode materials during charging.
Innovation Solution
A separator with a porous substrate layer and a surface layer featuring first particles forming convexities and second particles with a smaller average size, which absorb electrode expansion and enhance oxidation resistance and heat resistance by covering the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin microporous film is used as a separator to absorb negative electrode expansion, then electrode deterioration is suppressed, but oxidation resistance and heat resistance are insufficient
Solution Approach 1:
The separator is constructed as a composite structure combining a polyolefin microporous film base layer with a surface layer containing inorganic particles (such as alumina, silica, or boehmite) dispersed in a binder resin. This composite structure allows the separator to simultaneously achieve expansion absorption through the microporous structure while gaining oxidation and heat resistance from the inorganic particle surface layer.
Solution Approach 2:
The separator utilizes a microporous film structure with controlled pore size and distribution. The porous substrate provides expansion absorption capacity while the surface layer with inorganic particles maintains oxidation and heat resistance. The porosity is optimized to balance ion permeability, expansion absorption, and structural integrity.
2Object-affected harmful factors
If the separator structure is enhanced to improve oxidation resistance and heat resistance, then safety is improved, but the ability to absorb negative electrode expansion may be reduced
Solution Approach 1:
The separator employs a layered structure where different regions serve different functions: the base polyolefin microporous film provides expansion absorption capacity, while the surface layer with inorganic particles provides oxidation and heat resistance. This local differentiation of material properties allows both requirements to be satisfied simultaneously without compromising either function.
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 effectively suppresses electrode deterioration, improves oxidation resistance, and enhances heat resistance, thereby ensuring the stability and performance of lithium ion secondary batteries.
Implementation Method 1
second particles that have a smaller average particle size than the first particles, cover at least a part of a surface of the first particles, and cover at least a part of a surface of the substrate layer that is exposed between the first particles
Implementation Method 2
a substrate layer that is porous, and a surface layer that is provided on at least one main face of the substrate layer and that has an uneven shape
Data Source
AI summary
A separator includes a substrate layer that is porous, and a surface layer that is provided on at least one main face of the substrate layer and that has an uneven shape. The surface layer includes first particles that are for forming convexities of the uneven shape and that are a main component of the convexities, second particles that have a smaller average particle size than the first particles, cover at least a part of a surface of the first particles, and cover at least a part of a surface of the substrate layer that is exposed between the first particles, and a resin material.