Microbial Cellulose Separator for Lithium Battery Thermal Stability
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Solution Overview
Problem
Current lithium battery separators made from olefin-based polymers lack sufficient heat resistance and tensile strength, leading to safety concerns, especially in high-energy density applications, and existing alternatives like lignocelluloses have poor durability against external impacts.
Innovation Solution
Development of a separator using microbial cellulose nanofibers with a tensile strength of 39 MPa to 290 MPa, produced by culturing microorganisms to obtain microbial cellulose, which is then processed into a non-woven fabric structure with enhanced mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If olefin-based polymers (polyethylene or polypropylene) are used for separators, then the separators are inexpensive and easy to manufacture, but they exhibit low heat resistance leading to thermal runaway events
Solution Approach 1:
The patent uses microbial cellulose nanofibers as a composite material to create separators with high heat resistance. The microbial cellulose forms a three-dimensional network structure that maintains structural integrity at elevated temperatures, preventing thermal runaway while maintaining manufacturing feasibility through wet-laying and drying processes.
Solution Approach 2:
The separator is designed with controlled porosity (30-80%) using microbial cellulose nanofibers, creating a porous structure that allows ion transport while providing thermal stability. The porous network structure enables heat dissipation and prevents catastrophic failure under thermal stress.
2Temperature
If lignocelluloses are used for separators, then heat resistance is improved, but tensile strength is poor reducing durability against external impacts
Solution Approach 1:
The patent changes the material parameters by using microbial cellulose instead of lignocellulose, achieving both high tensile strength (39-290 MPa) and heat resistance. The microbial cellulose nanofibers have superior mechanical properties due to their highly crystalline structure and strong intermolecular hydrogen bonding, while maintaining thermal stability up to 200°C.
Solution Approach 2:
The separator exhibits local quality enhancement through the three-dimensional network structure of microbial cellulose nanofibers, where the nanofiber network provides localized strength reinforcement throughout the separator structure, ensuring uniform mechanical performance and impact resistance across the entire separator.
3Strength
If high-strength cellulose materials are used for separators, then tensile strength and durability are improved, but heat resistance may be compromised
Solution Approach 1:
The patent copies the superior mechanical properties of natural microbial cellulose (produced by bacteria like Gluconacetobacter xylinus) and replicates its three-dimensional network structure in the separator. This natural template provides both high tensile strength and inherent heat resistance, as microbial cellulose maintains its structural integrity at temperatures up to 200°C while achieving tensile strengths of 39-290 MPa.
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 microbial cellulose nanofiber separator provides improved heat resistance and tensile strength, addressing safety and durability issues in lithium batteries while maintaining high porosity and air permeability, thus enhancing battery performance and safety.
Implementation Method 1
culturing a microorganism to obtain a microbial cellulose; and preparing the separator comprising a cellulose nanofiber from the obtained microbial cellulose
Data Source
AI summary
Provided is a separator including microbial cellulose, a battery comprising the separator, and a method of producing the separator.