Crosslinked Battery Separator Coating for Compression Resistance
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Solution Overview
Problem
Lithium secondary battery separators face degradation due to local compression from heat and pressure during manufacturing and volumetric swelling during charge/discharge cycles, particularly when using silicon as a negative electrode, leading to reduced compression resistance and increased risk of short-circuits.
Innovation Solution
A separator for electrochemical devices featuring a porous polymer substrate with a polymer layer containing a crosslinked binder polymer, formed by reacting a boron-containing compound with a hydroxyl group-containing binder polymer, such as poly(vinyl alcohol) and borax, providing improved compression resistance and elasticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional separator is used with silicon negative electrode, then energy density is improved, but compression resistance deteriorates due to high hardness of silicon causing local compression
Solution Approach 1:
The separator comprises a porous polymer substrate combined with a polymer layer containing crosslinked binder polymer, creating a composite structure that leverages the porosity of the substrate for ion transport while the crosslinked polymer layer provides compression resistance against silicon electrode expansion
Solution Approach 2:
The binder polymer is crosslinked through reaction with boron-containing compounds, fundamentally changing the physical and mechanical parameters of the polymer layer to achieve both elasticity for thickness recovery and compression resistance against silicon hardness
2Ease of manufacture
If heat and pressure are applied during manufacturing, then electrodes are stacked and sealed, but separator undergoes local compression leading to degradation of physical properties
Solution Approach 1:
The binder polymer is pre-crosslinked before electrode assembly to establish a stable, elastic network structure that can withstand subsequent manufacturing processes including heat and pressure application without degrading
3Duration of action of moving object
If separator is compressed during charge/discharge cycles, then volumetric swelling occurs, but separator degradation increases leading to short-circuit risk
Solution Approach 1:
The crosslinked polymer layer provides dynamic elasticity, allowing the separator to flexibly expand and contract with silicon electrode volumetric changes during charge/discharge cycles while maintaining structural integrity and preventing short-circuits
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 crosslinked polymer layer maintains a thickness decrease of 4% or less under lamination conditions, enhancing the separator's compression resistance and preventing degradation, thus improving the performance and lifespan of lithium secondary batteries.
Implementation Method 1
the binder polymer having a crosslinked structure includes a crosslinked product of a boron-containing compound with a hydroxyl group-containing binder polymer
Data Source
AI summary
A separator for an electrochemical device having excellent compression resistance, an electrochemical device including the same, and a method of manufacturing the same. The separator for an electrochemical device includes a polymer layer on at least one surface of a porous polymer substrate. The polymer layer includes a binder polymer having a crosslinked structure including a structure represented by the following Chemical Formula 1:wherein each of R1 and R2 independently represents any one selected from the group consisting of a substituted or non-substituted C1-C10 alkylene group, a substituted or non-substituted C3-C10 cycloalkylene group and a substituted or non-substituted C6-C20 arylene group, and n is an integer ranging from 1 to 200.