Crosslinkable Li-Ion Separator for Shutdown and Rupture Resistance
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Solution Overview
Problem
Current lithium ion battery separators face challenges in achieving both low-temperature shutdown functions and high-temperature membrane rupture resistance, while maintaining cycle stability and safety. Existing methods often result in resin aggregates, non-homogeneous physical properties, and unpredictable secondary reactions, leading to compromised battery performance and safety.
Innovation Solution
A separator for electricity storage devices is developed, comprising a silane-modified polyolefin that crosslinks during contact with the electrolyte solution, allowing for controlled crosslinking timing. This approach inhibits the generation of resin aggregates and internal stress, while enhancing the separator's shutdown function and high-temperature membrane rupture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a silane crosslinked structure is constructed in a polyolefin separator to improve high-temperature membrane rupture resistance, then membrane rupture temperature increases, but resin aggregates and non-homogeneous physical properties occur during production
Solution Approach 1:
The separator is pre-modified with silane groups and peroxide during manufacturing, but the actual crosslinking reaction is postponed to occur later during battery formation or initial charging cycles. This preliminary preparation allows uniform distribution of crosslinking agents without premature reaction, avoiding resin aggregation while enabling subsequent high-temperature resistance.
Solution Approach 2:
A peroxide initiator is introduced as an intermediary substance that remains dormant during separator production and only activates the silane crosslinking reaction under specific conditions (heat, moisture) after battery assembly. This mediator enables controlled crosslinking timing, separating the manufacturing phase from the crosslinking phase to maintain physical property uniformity.
2Stability of the object's composition
If crosslinking is performed during separator production to enhance membrane rupture resistance, then high-temperature stability improves, but internal stress and production complexity increase
Solution Approach 1:
The separator performs self-crosslinking within the battery using the battery's own operating conditions (temperature, moisture from electrolyte) as triggers. The silane-modified polyolefin and peroxide embedded in the separator automatically react under battery formation conditions, eliminating the need for separate crosslinking equipment or complex production processes while achieving high-temperature stability.
Solution Approach 2:
The crosslinking reaction is triggered by changing physical parameters (temperature increase during battery formation, moisture from electrolyte) rather than requiring complex chemical processing equipment. This parameter-based activation simplifies production by using naturally occurring battery conditions to initiate crosslinking after assembly.
3Strength
If crosslinking is performed before battery assembly to improve separator strength, then membrane rupture resistance increases, but heat shrinkage control and production efficiency decrease
Solution Approach 1:
The separator is prepared with silane modification and peroxide incorporation during standard production processes, maintaining normal production efficiency. The actual crosslinking that enhances strength occurs as a preliminary action during battery formation before the battery enters service, avoiding disruption to separator manufacturing productivity while achieving the desired strength improvement.
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 proposed separator achieves both low-temperature shutdown and high-temperature membrane rupture resistance, ensuring improved cycle stability and safety of electricity storage devices. The controlled crosslinking process reduces production defects and maintains high productivity and economy.
Implementation Method 1
a first porous layer (layer A) that includes a silane-modified polyolefin and is capable of forming a crosslinked structure
Implementation Method 2
PTLs 1 to 6, for example, describe a silane crosslinking structure formed by contact between a silane-modified polyolefin-containing separator and water
Implementation Method 3
In order to ensure battery safety, separators must have both an active shutdown function and high membrane rupture temperature
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(b)
AI summary
A separator for an electricity storage device comprising a first porous layer (layer A) that includes a silane-modified polyolefin and is capable of forming a crosslinked structure, and a second porous layer (layer B) that includes inorganic particles, wherein the heat shrinkage factor at 150°C after formation of the crosslinked structure is 0.02 to 0.91 times the heat shrinkage factor at 150°C before formation of the crosslinked structure.