Lyocell Battery Separator Alkali Resistance
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Solution Overview
Problem
Current battery separators made from cellulosic fibers, such as lyocell, face challenges in achieving optimal alkali resistance and fibrillation ability, especially in alkaline batteries, due to variations in R10 and R18 values and hemicellulose content, which affect their dimensional stability and ion mobility.
Innovation Solution
The use of lyocell fibers with specific R10 and R18 values greater than 83% and 93%, respectively, and low hemicellulose content, along with mercerization treatment, enhances the alkali resistance and fibrillation ability of battery separators, leading to improved porosity and dimensional stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cellulosic fibres like rayon or mercerized pulp are used in battery separators, then the separators can be manufactured, but they exhibit poor fibrillation ability leading to insufficient density, porosity and dimensional stability
Solution Approach 1:
The patent applies parameter changes by selecting cellulosic fibres with specific R10 and R18 values greater than 83% and 93% respectively, and controlling hemicellulose content, to achieve optimal fibrillation ability, density, and porosity in battery separators
2Ease of manufacture
If standard lyocell fibres are used in alkaline battery separators, then the separators can be manufactured, but they exhibit insufficient alkali resistance in the presence of strong electrolytes like 30-40% KOH
Solution Approach 1:
The patent applies parameter changes by specifying R10 > 83% and R18 > 93% for lyocell fibres to achieve enhanced alkali resistance in battery separators exposed to strong electrolytes like 30-40% KOH
Solution Approach 2:
The patent applies preliminary action by pre-selecting lyocell fibres with high R10 and R18 values before separator manufacturing to ensure inherent alkali resistance, avoiding the need for post-manufacturing treatments
3Productivity
If cellulosic fibres with high fibrillation ability are used, then good porosity and ion mobility are achieved, but dimensional stability and shrinkage resistance are reduced
Solution Approach 1:
The patent applies parameter changes by selecting cellulosic fibres with specific R10 > 83% and R18 > 93% values that simultaneously provide high fibrillation ability for good ion mobility and dimensional stability with low shrinkage
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 specified lyocell fibers exhibit reduced weight and area reduction in 40% KOH solutions, maintaining high air permeability and fibrillation, resulting in enhanced alkali resistance and battery performance.
Implementation Method 1
cellulosic fibres are widely employed in battery separators due to their ability to absorb and retain the electrolytes
Implementation Method 2
the use of lyocell fibres with specific R10 and R18 values greater than 83% and 93%, respectively, and low hemicellulose content, along with mercerization treatment, enhances the alkali resistance and fibrillation ability
Data Source
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AI summary
The present invention relates to a battery separator, comprising cellulosic fibres of the lyocell genus, wherein the R10-value, the R18-value and the hemicellulose content of the lyocell fibres is as follows: R10 > 83%, preferably > 84% R18 > 93%, preferably > 94% Hemicellulose content < 3%. The present invention furthermore relates to novel lyocell fibres useful for battery separators, as well as batteries comprising the inventive battery separator.