Silane-Crosslinkable Li-Ion Separator for Heat-Stable Shutdown
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Solution Overview
Problem
Current lithium ion battery separators face challenges in achieving high-temperature membrane rupture resistance and cycle stability while maintaining safety and productivity, with existing methods often resulting in resin aggregates, non-homogeneous crosslinking, and potential secondary reactions that impair battery performance.
Innovation Solution
A separator for lithium ion batteries comprising a silane-modified polyolefin that crosslinks when in contact with 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.
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 introduces an intermediary approach by using silane-modified polyolefin that crosslinks through controlled reaction with water during battery assembly and initial charging cycles. The gradual crosslinking process mediated by electrolyte moisture avoids abrupt aggregation while achieving uniform crosslinked structure throughout the separator
Solution Approach 2:
The patent applies preliminary action by pre-modifying the polyolefin with silane groups before separator fabrication. This preliminary chemical modification prepares the separator for controlled crosslinking during battery operation, ensuring uniform crosslinking throughout the structure rather than forming aggregates during manufacturing
3Productivity
If dehydrating condensation catalysts are used to accelerate silane crosslinking, then productivity is improved, but secondary reactions occur that impair battery performance
Solution Approach 1:
The patent applies self-service by designing a system where the battery's own operating conditions (presence of water in electrolyte and initial charging cycles) trigger the silane crosslinking reaction. The separator crosslinks using the battery's natural environment without requiring external catalysts, eliminating secondary reactions while maintaining productivity through in-situ crosslinking during normal operation
4Temperature
If the separator structure is modified to improve heat-resistant stability, then temperature resistance is improved, but affinity with electrolyte solution and liquid retention decrease
Solution Approach 1:
The patent applies local quality by implementing crosslinking at the molecular level within the polymer chains while maintaining the macroscopic microporous structure unchanged. The crosslinks are formed locally within the polymer matrix, providing heat resistance without affecting the pore architecture that enables electrolyte retention and ionic conductivity
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 enables a separator with both low-temperature shutdown and high-temperature membrane rupture capabilities, reducing internal stress and deformation, and enhancing cycle stability and safety by forming a crosslinked structure within the separator and between electrodes, thus improving the overall performance and reliability of lithium ion batteries.
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.