Coated Lithium Battery Separator for Thermal Resistance and Adhesion
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Solution Overview
Problem
Existing lithium battery separators face challenges in achieving high thermal resistance and electrode plate adhesion, leading to potential short circuits and reduced lifespan due to thermal shrinkage and detachment issues.
Innovation Solution
A separator design featuring a porous substrate with a first coating layer containing a cross-linked aqueous cross-linking reactive poly(vinylamide)-based copolymer and inorganic particles, and a second coating layer with an acrylic copolymer and polyvinylidene fluoride-based binder in a specific weight ratio, enhancing thermal resistance and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene wax is used to add shutdown function to porous olefin-based polymer substrate, then shutdown function is improved, but thermal resistance deteriorates because the coating layer dissolves at high temperature
Solution Approach 1:
The patent uses a composite coating layer comprising polyethylene wax and polyvinylidene fluoride (PVDF) on a porous olefin-based polymer substrate. The PVDF component maintains coating integrity at high temperatures while the polyethylene wax provides shutdown function, resolving the contradiction between shutdown capability and thermal resistance.
Solution Approach 2:
The patent modifies the coating composition by adding PVDF with specific melting point characteristics (160-200°C) to change the thermal behavior parameters of the coating layer, enabling it to maintain structural integrity at high temperatures while retaining shutdown functionality.
2Temperature
If separator coating layer is designed for high thermal resistance, then thermal resistance is improved, but electrode plate adhesion deteriorates
Solution Approach 1:
The coating layer combines polyethylene wax (providing shutdown function and moderate adhesion) with PVDF (providing high-temperature stability and strong adhesion). This composite structure achieves both high thermal resistance and excellent electrode plate adhesion simultaneously.
Solution Approach 2:
The separator employs different functional components within the coating layer at different operational conditions: polyethylene wax activates shutdown function at shutdown temperatures while PVDF maintains adhesion and structural integrity at high temperatures, achieving local optimization of properties.
3Shape
If olefin-based polymer is used as separator, then flexibility is improved, but strength deteriorates when immersed in liquid electrolyte due to rapid thermal shrinkage at high temperature
Solution Approach 1:
The patent creates a composite structure where the porous olefin-based polymer substrate provides flexibility and shutdown function, while the PVDF-containing coating layer provides thermal stability and prevents rapid shrinkage at high temperatures, resolving the contradiction between flexibility and thermal stability.
Solution Approach 2:
The porous olefin-based polymer substrate maintains flexibility through its porous structure and material properties, while the coating layer acts as a protective thin film that constrains thermal shrinkage at high temperatures, enabling the separator to maintain both flexibility and thermal stability.
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 separator provides improved thermal resistance and electrode adhesion, resulting in enhanced lifespan characteristics and stability of lithium batteries.
Implementation Method 1
the binder includes a cross-linked product of an aqueous cross-linking reactive poly(vinylamide)-based copolymer
Implementation Method 2
a separator having high thermal resistance characteristics
Implementation Method 3
the first coating layer including: a binder and inorganic particles
Implementation Method 4
the second coating layer including an acrylic copolymer and a polyvinylidene fluoride-based binder in a weight ratio of greater than 1:1 and less than 1:4
Data Source
AI summary
The separator includes: a porous substrate; a first coating layer arranged on at least one surface of the porous substrate, the first coating layer including a binder and inorganic particles, wherein the binder includes a cross-linked product of an aqueous cross-linking reactive poly(vinylamide)-based copolymer, wherein the poly(vinylamide)-based copolymer includes repeating units derived from vinylamide monomers and repeating units derived from cross-linking reactive group-containing monomers, and is cross-linked by the cross-linking reactive groups; and a second coating layer arranged on both surfaces of the porous substrate on which the first coating layer is arranged, the second coating layer including an acrylic copolymer and a polyvinylidene fluoride-based binder in a weight ratio of greater than 1:1 and less than 1:4. The separator has high thermal resistance characteristics and enhanced electrode plate adhesion, and therefore, a lithium battery having excellent lifespan characteristics may be provided.