Battery Separator Coating for Heat Resistance and Layer Adhesion
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Solution Overview
Problem
Existing separators for secondary batteries face challenges in achieving improved adherence and durability, particularly in high-power, high-capacity applications such as electric vehicle batteries, which require enhanced heat resistance and stability.
Innovation Solution
A separator for secondary batteries is designed with a porous substrate and a heat-resistant porous layer that incorporates a specific copolymer binder system, including structural units derived from fluorine monomers and (meth)acrylic acid derivatives, along with a vinylidene fluoride-based binder, to enhance adherence and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat-resistance porous layer is included in the separator to improve battery stability and heat resistance, then thermal stability is improved, but adherence and durability of the layer become critical challenges
Solution Approach 1:
The patent employs a composite binder system comprising multiple polymer components including polyvinylidene fluoride-co-hexafluoropropylene and carboxymethyl cellulose, creating a multi-material composition that simultaneously provides heat resistance and improved adherence. This composite approach allows the heat-resistance porous layer to maintain structural integrity while adhering properly to the porous substrate.
Solution Approach 2:
The patent optimizes specific parameters of the binder components, including the molecular weight, composition ratio, and crosslinking degree of the polymer materials. By carefully controlling these parameters, the binder achieves optimal balance between thermal stability and adhesive properties, resolving the contradiction between heat resistance and adherence.
2Power
If the separator is designed for high-power and high-capacity applications, then battery capacity and power are improved, but the requirement for enhanced heat resistance and stability increases
Solution Approach 1:
The patent applies local quality enhancement by concentrating heat-resistant materials specifically in the heat-resistance porous layer that contacts the electrodes, while the bulk separator maintains its primary ion conduction function. This localized approach provides enhanced thermal management where needed without compromising overall battery power and capacity performance.
Solution Approach 2:
The separator utilizes a composite structure combining a porous substrate with a heat-resistance porous layer containing specialized binder materials. This composite design enables the separator to simultaneously support high-power applications and provide the required heat resistance through the synergistic combination of different material properties.
Data Source
Figure 1~2
AI summary
The present invention relates to a separator for a secondary battery and a lithium secondary battery comprising the same, wherein the separator comprises a porous substrate and a heat-resistant porous layer positioned on at least one surface of the porous substrate, the heat-resistant porous layer comprising a first binder, a second binder, and a filler, the first binder comprising a copolymer having: a first structural unit derived from a first fluorine monomer; a second structural unit derived from a second fluorine monomer; and a third structural unit derived from a monomer comprising at least one functional group selected from a hydroxyl group, a carboxyl group, an ester group, an acid anhydride group, and a derivative thereof, the second binder comprising at least one of a vinylidene fluoride homopolymer and a vinylidene fluoride copolymer.