Temperature-Responsive Separator Coating for Lithium-Ion Cell Thermal Runaway
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Solution Overview
Problem
Lithium-ion cells face safety issues due to thermal runaway, where the separator and electrode plates fail to separate timely, leading to increased temperature and difficulty in heat dissipation, potentially causing accidents like explosions, especially when abnormal conditions such as short circuits or overcharge occur.
Innovation Solution
A separator with a coating layer that decreases peel force between the separator and electrode plates at elevated temperatures, either by chemically reacting with acidic substances or softening, thereby increasing the heat dissipation area and improving cell stability. The coating layer includes micromatrix particles and a binder, with the micromatrix particles capable of reacting with acidic substances or softening at specific thresholds, such as 100° C, 130° C, or 150° C, to facilitate separation and enhance heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separator is adhered to the electrode plate through bonding, then the separator and electrode plate are fixed together, but at high temperature the peel force remains high preventing timely separation and heat dissipation
Solution Approach 1:
The coating layer is designed to change its adhesive properties in response to temperature changes. At normal operating temperatures, the coating maintains strong adhesion to keep the separator fixed on the electrode plate. When temperature exceeds a threshold (e.g., 100°C, 130°C, or 150°C), the coating's peel force decreases, enabling automatic separation for heat dissipation.
Solution Approach 2:
The separator comprises a composite structure with a base separator substrate and a functional coating layer. The coating layer contains specific materials (such as polyethylene, polypropylene, or other temperature-responsive polymers) that provide temperature-dependent adhesive characteristics, creating a composite material system that combines structural integrity with thermal response functionality.
2Temperature
If the separator remains bonded to the electrode plate during thermal runaway, then structural integrity is maintained, but heat dissipation area is insufficient leading to continued temperature rise
Solution Approach 1:
The bonding strength between the separator and electrode plate is made dynamic rather than static. The coating layer's adhesive strength automatically adjusts based on temperature conditions, being strong during normal operation and weak during thermal runaway, enabling the system to adapt its structural configuration in response to changing thermal conditions.
Solution Approach 2:
The harmful bonding effect is extracted or removed under specific conditions. When temperature exceeds the threshold, the coating layer's adhesive function is effectively deactivated or removed, allowing the separator to separate from the electrode plate and expose additional heat dissipation surfaces to the electrolyte.
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 effectively reduces the peel force between the separator and electrode plates at high temperatures, increasing the heat dissipation area and improving the stability of lithium-ion cells by allowing for easier separation and more efficient heat dissipation, thereby reducing the risk of safety accidents.
Implementation Method 1
The micromatrix particles are configured to soften or melt when the temperature is higher than the preset threshold
Implementation Method 2
the micromatrix particles are configured to be capable of chemically reacting with an acidic substance
Data Source
AI summary
A separator, a lithium-ion cell including the separator, and an electric apparatus including the lithium-ion cell. The separator includes a separator substrate and a coating layer disposed on the separator substrate, and the separator is adhered to an adjacent first electrode plate or second electrode plate through the coating layer. The coating layer is configured to decrease a peel force between the separator and an external component when a temperature is higher than a preset threshold or to be capable of chemically reacting with an acidic substance. When the temperature is higher than a threshold, the peel force between the separator and an adjacent electrode plate is decreased. To be specific, such lithium-ion cell can improve a current situation that the peel force between the separator and the electrode plate remains relatively great when the temperature of the cell is higher than a threshold.