Thin Coated Battery Separator for Heat-Resistant Energy Density
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density and maintaining high-temperature characteristics due to limitations in separator materials, particularly in heat resistance and energy density at thin thicknesses.
Innovation Solution
A separator for rechargeable lithium batteries is developed, featuring a substrate with a coating layer containing cube-shaped inorganic particles of specific diameters and thickness, which enhances heat resistance and energy density by controlling the particle size and shape, thereby improving high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the separator thickness is reduced to increase energy density, then the energy density is improved, but the heat resistance deteriorates
Solution Approach 1:
The separator is constructed as a composite material consisting of a polyolefin substrate combined with an inorganic particle coating layer. This composite structure allows the thin separator to maintain high heat resistance by incorporating heat-stable inorganic particles (such as alumina, silica, or boehmite) within the coating layer, while the overall thin design preserves high energy density. The inorganic particles form a thermal stability network that prevents membrane rupture at elevated temperatures even when the total separator thickness is reduced.
Solution Approach 2:
The separator utilizes a porous substrate structure with controlled pore size and distribution. The porous architecture provides sufficient mechanical strength and ion transport pathways in a thin configuration, allowing reduced thickness without compromising functional performance. The porosity is optimized to maintain electrolyte penetration and lithium ion conductivity while reducing the overall material volume to increase cell energy density.
2Reliability
If the coating layer thickness is increased to improve heat resistance, then the heat resistance is improved, but the energy density deteriorates
Solution Approach 1:
The patent optimizes the coating layer thickness parameter within a specific range (0.1 μm to 2.0 μm) to achieve the desired balance. By precisely controlling the coating thickness and inorganic particle size distribution, the separator attains adequate heat resistance without excessive material addition. The inorganic particle concentration and size are tuned to provide thermal stability with minimal coating thickness, thereby preserving energy density.
3Length of stationary object
If inorganic particles with smaller particle diameter are used to reduce coating thickness, then the coating thickness is reduced, but the heat resistance may deteriorate
Solution Approach 1:
The separator employs a multi-size inorganic particle distribution strategy where particles of different sizes are combined in the coating layer. Larger particles (0.5-2.0 μm) provide the primary thermal stability framework, while smaller particles (0.1-0.5 μm) fill interstices and enhance the coating density. This local quality variation within the coating ensures adequate heat resistance with reduced overall coating thickness, as the larger particles form the heat-resistant skeleton while smaller particles optimize space utilization.
Data Source
AI summary
A separator for a rechargeable lithium battery and a rechargeable lithium battery including the same, the separator includes a substrate; and a coating layer on at least one surface of the substrate, wherein the coating layer includes cube-shaped inorganic particles having a D50 particle diameter of greater than or equal to about 0.15 μm and less than about 0.4 μm, and a D99 particle diameter of greater than or equal to about 0.4 μm and less than or equal to about 1.0 μm, and the coating layer has a thickness of greater than 0 μm and less than about 2.0 μm.