Separator Surface Layer for Battery Anode Expansion
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Solution Overview
Problem
Current lithium ion secondary battery separators, such as polyolefin microporous membranes, lack sufficient oxidation resistance and heat resistance, which can lead to electrode deterioration and safety issues when used with alloy-based anode materials that expand during charging.
Innovation Solution
A separator with a porous substrate layer and a surface layer containing specific particles and resin material, where the surface layer has distinct regions of first and second particles and resin material, designed to absorb anode expansion and enhance oxidation and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin microporous membrane is used as the separator, then the manufacturing cost is reduced and the basic separation function is achieved, but the oxidation resistance and heat resistance are insufficient
Solution Approach 1:
The patent applies composite materials by forming a surface layer on the polyolefin microporous membrane that contains heat-resistant particles and oxidation-resistant particles. This composite structure combines the low-cost polyolefin base material with functional particles that provide oxidation resistance and heat resistance, resolving the contradiction between maintaining simple/low-cost structure and achieving high reliability.
Solution Approach 2:
The patent applies local quality by concentrating the heat-resistant and oxidation-resistant particles specifically in the surface layer that contacts the electrode, rather than throughout the entire separator. This localized approach provides the necessary protection at the critical interface while maintaining the simplicity and low cost of the bulk polyolefin membrane structure.
2Quantity of substance
If alloy-based anode material is used to increase capacity, then the battery capacity is improved, but the anode expansion causes damage to battery members and deformation
Solution Approach 1:
The patent applies beforehand cushioning by forming a surface layer with heat-resistant particles and oxidation-resistant particles on the separator before the anode expansion occurs. This pre-established protective layer absorbs and cushions the mechanical stress from anode expansion, preventing damage to the separator and electrode while allowing the use of high-capacity alloy-based anode materials.
3Quantity of substance
If the cathode potential is increased to realize capacity increase, then the energy density is improved, but the oxidation resistance and heat resistance requirements of the separator are not met
Solution Approach 1:
The patent applies composite materials by incorporating oxidation-resistant particles and heat-resistant particles into the separator's surface layer. This composite structure enables the separator to withstand the harsh oxidative and thermal environments created by high-potential cathodes, allowing energy density improvement without compromising separator durability.
Solution Approach 2:
The patent applies local quality by concentrating the oxidation-resistant and heat-resistant particles in the surface layer that directly contacts the high-potential cathode. This localized enhancement provides the necessary resistance to oxidation and heat at the critical interface where these harmful factors are most severe, while maintaining the overall simplicity of the separator structure.
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 effectively absorbs anode expansion, suppresses electrode deterioration, and enhances oxidation and heat resistance, improving the safety and performance of lithium ion secondary batteries.
Implementation Method 1
a technique of forming a concave and convex shape in the separator to absorb the expansion of the alloy-based anode material has been reported
Implementation Method 2
a technique of providing a surface layer using heat-resistant particles on the separator and the electrode to enhance the heat resistance and oxidation resistance of the battery
Implementation Method 3
a technique of providing a surface layer using heat-resistant particles on the separator and the electrode to enhance the heat resistance and oxidation resistance of the battery
Data Source
AI summary
A separator includes a substrate layer and a porous surface layer that is provided on at least one major surface of the substrate layer and contains a first particle, a second particle, and a resin material. The surface layer includes a first region configured by the first particle and a second region configured by the second particle and the resin material.