Cellulose Separator Fibrillation for Battery Short Circuit Resistance
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Solution Overview
Problem
Existing electrochemical element separators face challenges in maintaining a balance between short circuit resistance, electrolyte impregnation performance, and electrolyte retention performance while being thinned for downsizing, with microporous polyolefin membranes experiencing heat shrinkage and poor electrolyte affinity, and cellulose fiber separators having limited density control and fibrillation issues.
Innovation Solution
A cellulose fiber separator with a specific fibrillation range of 7.0 to 15.0% and a calculated distance-to-thickness ratio of 0.80 to 1.35, manufactured through beating and soft calendering to optimize fiber arrangement and movement, enhancing both short circuit resistance and electrolyte retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the separator thickness is reduced for downsizing, then the electrochemical element size decreases, but the short circuit resistance deteriorates
Solution Approach 1:
The invention changes the structural parameters of the separator by controlling the distance between cellulose stem fibers and their fibrillation degree. Specifically, it sets the distance-to-thickness ratio to 0.80 to 1.35 and fibrillation to 7.0 to 15.0%, which optimizes the balance between thinness and short circuit resistance without requiring increased thickness
Solution Approach 2:
The invention uses a composite structure where cellulose stem fibers are partially fibrillated to create a hierarchical composite material. The combination of intact stem fibers and fibrillated cellulose creates a network that provides both mechanical strength and electrical insulation, enabling thin separator design with maintained short circuit resistance
2Length of stationary object
If the separator is thinned for downsizing, then the electrochemical element height decreases, but the electrolyte retention performance deteriorates
Solution Approach 1:
The invention optimizes the separator structure by controlling the distance-to-thickness ratio (0.80 to 1.35) and fibrillation degree (7.0 to 15.0%), which creates an optimal pore structure that retains electrolyte effectively even at reduced thickness. This parameter optimization ensures sufficient electrolyte capacity without increasing separator thickness
Solution Approach 2:
The invention utilizes the porous structure created by controlled fibrillation of cellulose stem fibers to enhance electrolyte retention. The fibrillated cellulose creates a three-dimensional porous network that increases surface area and electrolyte holding capacity, compensating for the reduced thickness and maintaining adequate electrolyte volume for device operation
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 solution improves short circuit resistance and thins the separator without compromising electrolyte impregnation and retention performance, contributing to the downsizing of electrochemical elements while maintaining reliability and performance.
Implementation Method 1
a separator for an electrochemical element including a beaten cellulose fiber
Implementation Method 2
The main role of a separator in an electrochemical element is the separation of a pair of electrodes and the retention of the electrolyte
Data Source
AI summary
A heat-resistant separator for an electrochemical element in which the thickness of the separator is reduced while maintaining the balance between the short circuit resistance, resistance, electrolyte impregnation performance, and electrolyte retention performance of the separator. A separator for an electrochemical element includes beaten cellulose fibers, wherein the value obtained by dividing the average value for the distance between the center point of a cellulose stem fiber constituting part of the separator and the center point of another cellulose stem fiber nearest to said cellulose stem fiber by the thickness of the separator is 0.80 to 1.35.