LiF-Armored Lithium Anode Enables Ultra-Stable, Fire-Safe Batteries

A new study demonstrates how a lithium fluoride-rich artificial solid electrolyte interphase (SEI) stabilizes lithium metal anodes in flame-retardant batteries, enabling both exceptional safety and long-term performance. Lithium metal batteries offer exceptional energy density but face challenges from dendrite growth, unstable interfacial chemistry, and electrolyte flammability. While gel polymer electrolytes with flame retardants like triphenyl phosphate (TPP) address safety concerns, high concentrations of these additives typically corrode lithium anodes and dramatically shorten battery life. Researchers from Hebei University of Science and Technology, City University of Hong Kong, and Hainan University have reported a significant advancement in electrolyte-anode interface engineering in a study published on September 23, 2025, in Carbon Energy (DOI: 10.1002/cey2.70077).

The team designed a dual-confinement flame-retardant gel polymer electrolyte containing 70 wt.% TPP using coaxial electrospinning, creating a TPP/PVDF-HFP core encased within a PAN/PVDF-HFP shell. This structure limits molecular leakage through strong chemical interactions and physical containment, maintaining high flame retardancy while curbing corrosive side reactions. To further protect the anode, researchers immersed lithium metal in a 5% FEC-containing electrolyte to produce a uniform, dense LiF-rich SEI layer. Multi-modal analyses showed this engineered SEI blocks penetration of TPP-derived species and substantially reduces anode corrosion depth while enhancing lithium-ion mobility and promoting dendrite-free plating.

Electrochemical tests validated the design's effectiveness: Li||Li cells operated stably for 2400 hours at 0.5 mA cm⁻² and 1500 hours at 5 mA cm⁻². In full-cell configurations, LFP||Li cells retained 98.9% capacity after 1500 cycles at 1 C and preserved 81.7% capacity after 6000 cycles at 10 C, demonstrating exceptional endurance under fast-charging conditions. The lead corresponding scientist noted that precise interface engineering is essential to advancing both safety and durability of lithium metal batteries, explaining that integrating dual-confinement flame-retardant electrolyte with LiF-rich artificial SEI resolves the conflict between fire protection and anode stability while improving lithium-ion transport for reliable high-rate operation.

This combined SEI-electrolyte strategy represents a promising direction for developing high-performance, intrinsically safer lithium metal batteries suitable for electric vehicles, grid-level storage, aerospace systems, and next-generation flexible pouch cells. The underlying design principle of merging chemical confinement, structural encapsulation, and deliberate SEI engineering can be applied to other reactive anodes and high-voltage cathodes, potentially accelerating practical adoption of lithium metal technologies as global demand for high-energy batteries intensifies alongside strict safety requirements. The study was supported by multiple funding sources including The National Natural Science Foundation of China (52404316, 52474325), The S&T program of Hebei Province (225A4404D), and The Natural Science Foundation of Hainan Province (524RC475).