EVA-PE Battery Separator for Electrolyte Wetting and Strength
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Solution Overview
Problem
Wet separators for lithium secondary batteries exhibit poor electrolyte impregnation due to low affinity for electrolytes, which is a challenge in achieving higher capacity and energy density required for applications like electric vehicles, while maintaining mechanical strength.
Innovation Solution
A separator for electrochemical devices is developed using a resin mixture of ethylene vinyl acetate copolymer and polyethylene, with a controlled content of vinyl acetate to enhance electrolyte impregnation without compromising mechanical strength, featuring a specific range of vinyl acetate content, molecular weight, melting point, and crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If wet separator is used to achieve excellent insulation, chemical resistance, withstand voltage stability, and mechanical strength, then mechanical strength is improved, but electrolyte impregnation deteriorates due to low affinity for electrolyte
Solution Approach 1:
The patent changes the chemical composition parameters of the separator by incorporating vinyl acetate copolymer (with 1-30 mol% vinyl acetate content) and controlling the ratio of polyethylene to vinyl acetate copolymer (90:10 to 70:30 by weight). This parameter change improves electrolyte affinity while maintaining mechanical strength, resolving the contradiction between mechanical strength and electrolyte impregnation.
Solution Approach 2:
The patent creates a composite separator material combining polyethylene and vinyl acetate copolymer in specific ratios. This composite structure leverages the mechanical strength of polyethylene and the electrolyte affinity of vinyl acetate copolymer, simultaneously achieving both improved mechanical strength and electrolyte impregnation.
2Reliability
If vinyl acetate content is increased to improve electrolyte impregnation, then electrolyte impregnation is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent optimizes the vinyl acetate content parameter within the specific range of 1-30 mol% and controls the weight ratio of polyethylene to vinyl acetate copolymer at 90:10 to 70:30. This precise parameter control ensures sufficient electrolyte affinity while preventing excessive softening that would compromise mechanical strength.
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 improves electrolyte impregnation and maintains mechanical strength, with a lower shut-down temperature, enhancing the safety and stability of electrochemical devices.
Implementation Method 1
a separator for an electrochemical device with improved electrolyte impregnation
Implementation Method 2
the ethylene vinyl acetate copolymer contains 20 wt.% or less of vinyl acetate
Data Source
AI summary
The present disclosure relates to a separator for an electrochemical device and an electrochemical device comprising the same, and more specifically, to a separator for an electrochemical device comprising a resin mixture containing ethylene vinyl acetate copolymer (EVA) and polyethylene (PE), wherein the ethylene vinyl acetate copolymer (EVA) contains 20 wt.% or less of vinyl acetate (VA) based on the total amount of the ethylene vinyl acetate copolymer (EVA)., and an electrochemical device comprising the separator.