Cross-Linked Lithium Battery Separator Coating for Electrolyte Shrinkage
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in maintaining stability due to thermal shrinkage of the separator in the electrolyte, which can compromise the battery's performance.
Innovation Solution
A separator for rechargeable lithium batteries is developed with a coating layer comprising a cross-linked product of a (meth)acryl-based binder, carboxyalkyl cellulose or its salt, and a filler, using aziridine-based and carbodiimide-based cross-linking agents, which reduces dry shrinkage and electrolyte shrinkage rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used in rechargeable lithium batteries, then the battery can operate, but the separator undergoes thermal shrinkage in the electrolyte causing instability
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition and cross-linking density of the coating layer to control the separator's thermal and electrolyte shrinkage behavior. The cross-linked network structure with specific binding agents and fillers creates a stable framework that resists dimensional changes under operating conditions.
Solution Approach 2:
The patent uses composite materials by combining multiple components in the coating layer including binding agents (polymer resins), fillers (inorganic particles), and cross-linking agents. This composite structure provides both mechanical integrity and thermal stability, preventing separator shrinkage while maintaining porosity for ion transport.
2Reliability
If the separator maintains low shrinkage rates, then heat resistance and mechanical stability improve, but the complexity of the coating composition increases
Solution Approach 1:
The patent applies local quality by creating a coating layer with spatially distributed functional components - binding agents providing structural framework, fillers providing thermal stability at specific locations, and cross-linking agents creating localized rigid networks. This localized functional distribution achieves overall stability without requiring uniform complexity throughout the entire separator.
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 separator exhibits significantly low shrinkage rates, maintaining heat resistance and mechanical stability, thereby enhancing the overall performance and stability of the lithium battery.
Implementation Method 1
The coating layer includes a cross-linked product of a binder, a cross-linking agent, and carboxyalkyl cellulose or a salt thereof
Implementation Method 2
The separator is impregnated with an electrolyte
Data Source
AI summary
Examples of the present disclosure include a separator for a rechargeable lithium battery, and a rechargeable lithium battery including the separator. The separator for a rechargeable lithium battery includes a porous substrate, and a coating layer on at least one surface of the porous substrate. The coating layer includes a cross-linked product of a binder, a cross-linking agent, and carboxyalkyl cellulose or a salt thereof, and a filler. The binder includes a (meth)acryl-based binder including a first structural unit derived from (meth)acrylamide and a second structural unit derived from (meth)acrylamido sulfonic acid or a salt thereof. The cross-linking agent includes one or more of an aziridine-based cross-linking agent and a carbodiimide-based cross-linking agent.