Self-Healing Composite Separator for Li-Ion Thermal Runaway
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Solution Overview
Problem
Current lithium-ion battery separators undergo irreversible structural changes such as thermal shrinkage, deformation, and pore closure during high temperature or thermal runaway conditions, leading to short-circuit currents and heat release, compromising the electrochemical performance of the cell.
Innovation Solution
A composite separator comprising a base film layer with a self-healing functional layer containing a thermally cyclopolymerizable precursor material that forms a crosslinked polymer structure upon thermal cyclopolymerization, preventing structural changes and maintaining the separator's pore structure under high temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used, then the battery can operate under normal conditions, but under high temperature or thermal runaway conditions the separator undergoes irreversible structural changes such as thermal shrinkage, deformation, and pore closure
Solution Approach 1:
The patent applies a self-healing functional layer containing thermally cyclopolymerizable precursor material onto the separator surface before thermal runaway occurs. This preliminary action enables the separator to autonomously repair thermal damage (shrinkage, deformation, pore closure) after exposure to high temperature, converting a passive structure into an active self-repairing system that restores its protective function post-thermal-event.
Solution Approach 2:
The patent changes the physical and chemical parameters of the separator by introducing a functional layer with thermally cyclopolymerizable precursor material. Upon thermal runaway, this material undergoes cyclopolymerization to form a crosslinked polymer structure, fundamentally altering the separator's thermal response from irreversible degradation to reversible self-healing, thereby improving high-temperature reliability.
2Strength
If the separator undergoes thermal shrinkage and pore closure, then the structural integrity is compromised, but this leads to contact between positive and negative electrode plates causing short-circuit current and heat release
Solution Approach 1:
The patent converts the harmful effect of thermal runaway into a beneficial self-healing response. The thermal energy that would normally cause irreversible damage (shrinkage, deformation) instead triggers the cyclopolymerization of precursor material in the functional layer, forming a crosslinked polymer structure that repairs the separator and prevents short-circuit current and heat release.
Solution Approach 2:
The self-healing functional layer acts as an intermediary between the base separator and the thermal runaway event. This functional layer absorbs and responds to thermal stress by undergoing cyclopolymerization, mediating the interaction between thermal energy and the separator structure to prevent direct contact between electrodes and eliminate harmful short-circuit effects.
3Reliability
If a self-healing functional layer with thermally cyclopolymerizable precursor material is applied to the separator, then the separator gains self-healing capability and thermal stability, but the device complexity increases
Solution Approach 1:
The patent applies the self-healing functional layer locally on the separator surface rather than throughout the entire separator structure. This localized application provides self-healing capability exactly where it is needed (on the surface exposed to thermal runaway) while minimizing the addition of complex materials and maintaining the simplicity of the base separator structure.
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 composite separator effectively isolates positive and negative electrodes, preventing short circuits and maintaining normal current and heat generation, enhancing mechanical strength, thermal stability, and providing a thermal protective effect on the cell.
Implementation Method 1
the self-healing functional layer contains a thermally cyclopolymerizable precursor material, and/or after the self-healing functional layer has self-healed, the precursor material forms a crosslinked polymer structure
Implementation Method 2
The separator is an electrically insulating thin film with a porous structure and serves to isolate a positive electrode from a negative electrode in a battery, preventing free passage of electrons in the battery while also enabling ions to freely pass between the positive and negative electrodes
Implementation Method 3
after the self-healing functional layer has self-healed, the precursor material forms a crosslinked polymer structure
Data Source
AI summary
A composite separator comprises at least one base film layer and a self-healing functional layer laminated on a surface of the base film layer, wherein the self-healing functional layer contains a thermally cyclopolymerizable precursor material, and/or after the self-healing functional layer has self-healed, the precursor material forms a crosslinked polymer structure. The surface of the base film layer of the composite separator of the present application is provided with a self-healing functional layer, and the composite separator functions to isolate the positive electrode plate from the negative electrode plate and conduct lithium ions while blocking electrons when the secondary battery is under normal working conditions. When overheating or thermal runaway occurs inside the secondary battery, the precursor material in the self-healing functional layer undergoes a thermal polymerization reaction to generate a high-temperature-resistant and high-mechanical-strength crosslinked polymer.