Separator for electrochemical device with heat resistant layer
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Solution Overview
Problem
Conventional separators for electrochemical devices, such as lithium secondary batteries, face challenges with heat shrinking and adhesion issues due to the use of polyolefin-based porous substrates, leading to potential short circuits and degradation of battery performance.
Innovation Solution
A separator design incorporating a heat-resistant layer with inorganic particles and a high-melting-point binder resin, along with an adhesive layer featuring fluorinated and non-fluorinated binder resins, is introduced to enhance peel strength and adhesion between the substrate and electrodes, while maintaining high thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the content of inorganic particles in the porous coating layer is increased to inhibit heat shrinking, then heat resistance is improved, but adhesion between the porous coating layer and the polyolefin-based porous substrate deteriorates
Solution Approach 1:
The patent introduces a specific binder polymer as an intermediary substance between the inorganic particles and the porous substrate. This binder polymer with controlled molecular weight and functional groups acts as a mediator that bonds both the inorganic particles and the substrate, allowing high inorganic particle content (5-20 wt%) while maintaining strong adhesion. The binder polymer resolves the contradiction by providing a chemical bridge that enables both heat resistance and adhesion simultaneously.
Solution Approach 2:
The patent optimizes specific parameters of the binder polymer including molecular weight (10,000-1,000,000), functional group content (1-10 mmol/g), and composition ratio to achieve the desired balance. By changing these parameters, the system can maintain strong adhesion even with high inorganic particle content, resolving the contradiction between heat resistance and adhesion strength.
2Strength
If the content of binder polymer in the porous coating layer is increased to improve adhesion, then adhesion is improved, but the effect of inhibiting heat shrinking is degraded
Solution Approach 1:
The patent precisely controls the binder polymer content at 5-20 wt% of the porous coating layer, avoiding excessive binder polymer that would fill pores and reduce heat shrinkage resistance. This optimized parameter range ensures sufficient adhesion while maintaining the porous structure's heat shrinkage inhibition capability.
Solution Approach 2:
The patent creates a composite porous coating layer combining inorganic particles, binder polymer, and porous substrate in specific ratios. This composite structure leverages the heat resistance of inorganic particles and the adhesion of binder polymer, achieving both functions simultaneously without compromising either property.
3Strength
If the porosity in the porous coating layer is decreased to improve mechanical strength, then mechanical strength is improved, but ion conductivity and battery performance are degraded
Solution Approach 1:
The patent creates different local structures within the porous coating layer: the region near the substrate provides mechanical support through the substrate-binder-particle composite structure, while the outer region maintains high porosity for ion transport. This local differentiation allows the coating to have both mechanical strength and high ion conductivity simultaneously.
Solution Approach 2:
The patent utilizes a porous coating layer with controlled porosity (30-70%) that maintains mechanical integrity through the composite structure while preserving sufficient pore space for ion conduction. The porous structure is optimized to provide both mechanical support and ion transport pathways.
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 exhibits improved heat resistance, thermal stability, and enhanced peel strength, thereby increasing ion conductivity and resistance characteristics, and ensuring better thermal safety and battery performance.
Implementation Method 1
the inorganic particles in the porous coating layer coated on the polyolefin-based porous substrate functions as a kind of spacer which can retain the physical shape of a porous active layer, and thus can inhibit the polyolefin-based porous substrate from heat shrinking upon overheating of an electrochemical device
Implementation Method 2
an adhesive layer featuring fluorinated and non-fluorinated binder resins, is introduced to enhance peel strength and adhesion between the substrate and electrodes
Data Source
AI summary
A separator for an electrochemical device including a heat resistant layer and an adhesive layer and a method for manufacturing the same. The separator uses a heat resistant polymer having a high melting point for a heat resistant layer and shows excellent peel strength between the separator substrate and the heat resistant layer and high adhesion between the separator and an electrode.