Silane-Modified Polyolefin Separator Crosslinking
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Solution Overview
Problem
Current lithium ion battery separators face challenges in achieving high-temperature membrane rupture resistance, shutdown function, and cycle stability, with existing methods often resulting in resin aggregates, non-homogeneous crosslinking, and potential secondary reactions that compromise battery safety and performance.
Innovation Solution
A separator for lithium ion batteries comprising a silane-modified polyolefin that crosslinks when contacting the electrolyte solution, with a specific weight ratio of silane-modified polyolefin to polyethylene, and a crosslinking method that avoids the use of dehydrating condensation catalysts, allowing for controlled crosslinking during the production process, thereby preventing resin aggregates and enhancing homogeneity and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin separator is used to ensure chemical inertness and electrochemical stability, then reliability is improved, but heat-resistant stability above the melting point is insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the polyolefin separator through silane grafting, transforming it from a thermoplastic material to a thermosetting crosslinked structure. This chemical modification changes the fundamental thermal properties of the separator, enabling it to maintain structural stability above the original melting point while retaining electrochemical compatibility
Solution Approach 2:
The patent creates a composite material system by combining silane-modified polyolefin with crosslinking agents. The resulting crosslinked polyolefin separator integrates the chemical inertness of polyolefin with the high-temperature stability of crosslinked networks, achieving both reliability and heat resistance simultaneously
2Temperature
If silane crosslinking is formed by contact with water to improve high-temperature membrane rupture properties, then temperature resistance is improved, but resin aggregates and non-homogeneous crosslinking occur
Solution Approach 1:
The patent replaces the chemical mechanism of water-based crosslinking with a physical mechanism using electron beam irradiation. This substitution eliminates the need for water diffusion and chemical catalysts, enabling uniform energy distribution throughout the separator material and producing homogeneous crosslinking without resin aggregation
Solution Approach 2:
The electron beam irradiation process applies periodic energy pulses that uniformly distribute crosslinking activation throughout the separator. This periodic irradiation ensures consistent crosslinking density across the entire material, preventing localized aggregation and achieving homogeneous structural transformation
3Productivity
If dehydrating condensation catalysts are used to accelerate silane crosslinking, then productivity is improved, but secondary reactions compromise battery safety
Solution Approach 1:
The patent replaces chemical catalysis with physical electron beam irradiation to initiate and accelerate crosslinking. This substitution eliminates all catalyst-related secondary reactions while maintaining high crosslinking speed, as the electron beam provides direct energy activation without requiring chemical intermediaries
Solution Approach 2:
The electron beam acts as an intermediary that transfers energy to initiate crosslinking without remaining in the final product. Unlike chemical catalysts that may residue and cause secondary reactions, the electron beam delivers its effect and disappears, leaving no harmful substances that could compromise battery safety
4Temperature
If the separator structure is modified to improve heat-resistant stability, then temperature resistance is improved, but affinity with electrolyte solution and Li ion permeability deteriorate
Solution Approach 1:
The patent applies preliminary action by performing silane grafting and crosslinking modifications before the separator is assembled into the battery. This pre-modification ensures that the crosslinked structure is established in advance, allowing the separator to maintain both high-temperature stability and proper ion permeability characteristics during subsequent battery operation without structural degradation
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 provides a separator with improved high-temperature membrane rupture resistance, shutdown function, and cycle stability, reducing the risk of secondary reactions and ensuring battery safety and performance, while also simplifying the production process by initiating crosslinking in response to the electrolyte solution, thus avoiding internal stress and deformation.
Implementation Method 1
silane crosslinking reaction of the silane-modified polyolefin is initiated when it contacts with the electrolyte solution
Data Source
AI summary
A separator for an electricity storage device comprising a silane-modified polyolefin, wherein silane crosslinking reaction of the silane-modified polyolefin is initiated when it contacts with the electrolyte solution, as well as a method for producing the separator.