Electrolyte-Triggered Crosslinked Separator for Li-Ion Shutdown Stability
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Solution Overview
Problem
Existing lithium ion battery separators face challenges in achieving both a low-temperature shutdown function and high-temperature membrane rupture resistance, while ensuring safety, output, and cycle stability, with conventional crosslinking methods leading to production defects, stress, and unpredictable secondary reactions.
Innovation Solution
A silane-modified polyolefin separator that crosslinks during contact with the electrolyte solution, allowing controlled crosslinking timing and formation of an amorphous crosslinked structure, enhancing shutdown function and membrane rupture resistance without increasing internal stress or deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If crosslinking is performed before battery assembly using conventional methods (water contact or thermal treatment), then membrane rupture resistance is improved, but production defects and internal stress increase
Solution Approach 1:
The separator is pre-modified with silane groups during manufacturing, but the actual crosslinking reaction is postponed until after battery assembly when the separator contacts the electrolyte. This preliminary preparation allows the crosslinking to occur at the optimal time without causing manufacturing defects
Solution Approach 2:
The electrolyte serves as an intermediary medium that triggers and facilitates the crosslinking reaction. Instead of using water or external heat treatment that cause defects, the electrolyte naturally present in the battery initiates the crosslinking of silane-modified polyolefin through trace water or chemical reactions
2Temperature
If crosslinking is performed early in production, then membrane rupture temperature is improved, but separator deformation and stress occur
Solution Approach 1:
The separator is pre-modified with silane groups during manufacturing, but the actual crosslinking reaction is postponed until after battery assembly when the separator contacts the electrolyte. This preliminary preparation allows the crosslinking to occur at the optimal time without causing manufacturing defects
Solution Approach 2:
The crosslinking reaction conditions are changed from external water contact or high-temperature treatment to in-situ reaction with electrolyte at battery operating conditions. This parameter change allows crosslinking to occur without thermal stress or mechanical deformation
3Strength
If crosslinking density is increased to improve membrane rupture resistance, then high-temperature strength is improved, but cycle stability decreases due to unpredictable secondary reactions
Solution Approach 1:
The electrolyte serves as an intermediary medium that triggers and facilitates the crosslinking reaction. Instead of using water or external heat treatment that cause defects, the electrolyte naturally present in the battery initiates the crosslinking of silane-modified polyolefin through trace water or chemical reactions
Solution Approach 2:
The crosslinking reaction conditions are changed from external water contact or high-temperature treatment to in-situ reaction with electrolyte at battery operating conditions. This parameter change allows crosslinking to occur without thermal stress or mechanical deformation
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 provides both low-temperature shutdown and high-temperature resistance, improving cycle stability and safety, while reducing production defects and stress, and enhancing the strength between device components.
Implementation Method 1
silane crosslinking reaction of the silane-modified polyolefin is initiated when it contacts with the electrolyte solution
Implementation Method 2
In order to ensure battery safety, separators must have both an active shutdown function and high membrane rupture temperature
Implementation Method 3
heat release due to interior battery short circuiting is inhibited by a shutdown function when the degree of crystallinity and gel fraction are in specific ranges
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(b)
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.