Reviewed by Frances BriggsJun 24 2025
A study published in Nano-Micro Letters reveals a novel bi-layered battery covering, measuring just 320 microns thick. This covering offers rapid-fire response and long-lasting protection.
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Fire safety is critical in all industries, particularly construction, transportation, electronics, and energy storage. Current flame-retardant coatings fail to provide instant and long-term protection, limiting their applicability.
Why This Bi-Layered Coating Matters
The bi-layered coating developed in this study shows rapid responses and extended protection from fire due to an intumescent flame-retardant (IFR) exterior layer and a ceramifiable inner layer.
The coating can endure fire temperatures up to 1400 °C for more than 900 seconds, substantially surpassing standard coatings. This level of protection is essential for materials such as aluminum and glass fabric-reinforced epoxy resin, which are otherwise burned through in under 200 seconds.
When applied to lithium soft-package batteries, the bi-layered coating inhibits the production and degradation of solid interface layers, resulting in improved electrochemical stability and fire safety.
Innovative Design and Mechanisms
The bi-layered structure acts as a relay, with the IFR layer providing immediate protection and the ceramifiable layer supplying long-term stability.
At temperatures below 300 °C, the IFR layer quickly produces a char barrier, but the ceramifiable layer undergoes a phase change at roughly 550 °C to form a long-lasting ceramic barrier.
The researchers optimized the formulations of both layers to enhance the covering's overall performance. Reinforced with alumina synergists, the IFR layer retained 31 % of its mass at 800 °C.
In contrast, the ceramifiable layer, composed of low-melting glass powder and other fillers, maintained more than 97 % residue, ensuring robust structural integrity even under extreme heat.
These results showed that the novel bi-layered covering responded quickly and provided outstanding thermal insulation. The char layers generated during combustion efficiently impede heat conduction, shielding underlying substrates from long-term exposure to high temperatures.
Future Outlook
The research demonstrated the bi-layered coating's thin and efficient design, making it highly scalable. Its capacity to provide immediate and long-term protection makes it suitable for commercial use in various sectors.
The study also showed that the coating was effective on a variety of different substrates, including polyurethane foam, aluminum, and glass fabric-reinforced epoxy resin. By combining an IFR and ceramifiable layer and showing its effective flame retardant properties, this study provides a framework for future development of high-performance flame-retardant coatings.
Journal Reference
Tang, W. et al. (2025) Bi-Layered, Ultrathin Coating Initiated Relay Response to Impart Superior Fire Resistance for Polymeric and Metallic Substrates. Nano-Micro Letters. doi.org/10.1007/s40820-025-01739-8.