A new study published in Carbon Energy reports a breakthrough in lithium metal battery design that reconciles the long-standing trade-off between fire safety and anode stability. Researchers from Hebei University of Science and Technology, City University of Hong Kong, and Hainan University engineered a LiF-rich artificial solid electrolyte interphase (SEI) on lithium metal and paired it with a dual-confinement flame-retardant gel polymer electrolyte. This strategy enables batteries to operate stably for thousands of cycles while maintaining intrinsic fire resistance.
Lithium metal anodes offer high theoretical capacity but suffer from dendrite growth and interfacial instability. Conventional gel polymer electrolytes incorporate flame retardants like triphenyl phosphate (TPP) to reduce flammability, but high TPP concentrations corrode the lithium anode, drastically shortening battery life. The new approach addresses this by pre-engineering a dense LiF-rich SEI on the lithium surface, which blocks TPP penetration and suppresses corrosion.
The team developed a gel polymer electrolyte containing 70 wt.% TPP using coaxial electrospinning, creating a TPP/PVDF-HFP core encased in a PAN/PVDF-HFP shell. This dual-confinement design limits TPP leakage and mitigates side reactions. To further protect the anode, lithium metal was immersed in a 5% FEC-containing electrolyte to form a uniform LiF-rich SEI. Multi-modal analyses including UV–vis spectroscopy, TOF-SIMS, XPS, and AFM confirmed that the engineered SEI blocks TPP-derived species and reduces anode corrosion depth.
Electrochemical tests showed exceptional performance: Li||Li cells cycled stably for 2400 hours at 0.5 mA cm⁻² and 1500 hours at 5 mA cm⁻². Full-cell LFP||Li batteries retained 98.9% capacity after 1500 cycles at 1 C and 81.7% capacity after 6000 cycles at 10 C, demonstrating outstanding endurance under fast charging. "The study compellingly shows that precise interface engineering is essential to advancing both the safety and durability of lithium metal batteries," said the lead corresponding scientist. "By integrating a dual-confinement flame-retardant electrolyte with a LiF-rich artificial SEI, we resolved the long-standing conflict between fire protection and anode stability."
This combined SEI–electrolyte strategy represents a promising direction for high-performance, intrinsically safer lithium metal batteries. Its ability to sustain thousands of cycles at high current densities positions it for electric vehicles, grid-level storage, aerospace systems, and flexible pouch cells. The design principle—merging chemical confinement, structural encapsulation, and deliberate SEI engineering—can be applied to other reactive anodes and high-voltage cathodes. As demand for high-energy batteries grows alongside strict safety requirements, this approach may accelerate the practical adoption of lithium metal technologies.
The study is published in Carbon Energy with DOI: 10.1002/cey2.70077. Funding was provided by the National Natural Science Foundation of China, S&T program of Hebei Province, Natural Science Foundation of Hainan Province, and others. For more information, visit Chuanlink Innovations.
