Microporous Battery Separator for High Planar Elastic Recovery
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Solution Overview
Problem
Existing microporous separators for lithium-ion batteries have low planar elastic recovery rates, especially those prepared by the wet process, which can lead to irreversible deformation and affect electrochemical safety performance.
Innovation Solution
A microporous separator with improved planar elastic recovery is achieved by controlling the proportion of low molecular weight chain segments in a polyolefin resin, combined with a low-temperature multi-point distributed stretching process in the machine-direction and a low-ratio stretching in the transverse-direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyolefin-based microporous membrane is used as separator for lithium-ion battery, then excellent membrane mechanical strength and shutdown characteristics are achieved, but planar elastic recovery rate is low (lower than 14% in both transverse and machine directions)
Solution Approach 1:
The patent changes the molecular weight distribution parameter of the polyolefin resin by controlling the proportion of low molecular weight chain segments (10-30 mol %) to improve planar elastic recovery rate while maintaining mechanical strength. This parameter optimization resolves the contradiction between strength and elastic recovery.
2Productivity
If wet process is used to prepare separator for lithium-ion battery, then production is achieved, but planar elastic recovery rate is particularly low and irreversible deformation occurs during battery assembly
Solution Approach 1:
The patent optimizes the molecular weight distribution parameter of the polyolefin resin used in wet process preparation, specifically controlling low molecular weight chain segment proportion (10-30 mol %), to achieve both productive manufacturing and high planar elastic recovery rate (>14%), preventing irreversible deformation during battery assembly.
3Ease of manufacture
If commonly used polyolefin resin is used as main raw material, then material availability and cost are maintained, but planar elastic recovery rate remains low and surface resistance is high
Solution Approach 1:
The patent modifies the molecular weight distribution parameter of commonly used polyolefin resin by controlling low molecular weight chain segment proportion (10-30 mol %), thereby improving planar elastic recovery rate and reducing surface resistance while maintaining material availability and ease of manufacture.
4Length of stationary object
If separator thickness is reduced to achieve small thickness requirement, then battery size is minimized, but mechanical strength and electrochemical safety performance may be compromised
Solution Approach 1:
The patent optimizes the molecular weight distribution parameter of the polyolefin resin, specifically controlling low molecular weight chain segment proportion (10-30 mol %), to enhance planar elastic recovery rate. This allows the use of thinner separators with maintained mechanical strength and electrochemical safety performance.
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 resulting separator exhibits a machine-direction and transverse-direction elastic recovery rate greater than or equal to 14%, reduced surface resistance by 20% or more, and maintains suitable pore diameter, air permeability, and mechanical strength, making it suitable for lithium-ion batteries.
Implementation Method 1
the microporous separator has a machine-direction elastic recovery rate greater than or equal to 14% and a transverse-direction elastic recovery rate greater than or equal to 14%
Data Source
AI summary
The present disclosure relates to a microporous separator for lithium battery and its preparation method. Specifically, the present disclosure provides a microporous separator for lithium battery, which is a single-layer porous membrane containing polyolefin resin, having excellent elastic recovery performance in both a machine direction and a transverse direction. The present disclosure further provides a preparation method for a separator for lithium-ion battery with high planar elastic recovery.