A new study published in Carbon Energy on September 23, 2025, reports a significant advancement in electrolyte–anode interface engineering that could pave the way for ultra-stable and fire-safe lithium metal batteries. The research team from Hebei University of Science and Technology, City University of Hong Kong, and Hainan University developed a dual-confinement flame-retardant gel polymer electrolyte paired with a pre-formed LiF-rich solid electrolyte interphase (SEI) on lithium metal. This combined strategy suppresses corrosion, accelerates Li⁺ transport, and enables stable cycling even under demanding conditions.
Lithium metal batteries offer exceptional energy density but are plagued by dendrite growth, unstable interfacial chemistry, and the flammability of conventional electrolytes. Gel polymer electrolytes improve safety but rely on large quantities of flame retardants like triphenyl phosphate (TPP), which can corrode the lithium anode and shorten battery life. The new approach resolves this conflict by building a LiF-rich artificial SEI that blocks TPP-derived species from penetrating the anode.
The team began by developing a gel polymer electrolyte containing 70 wt.% TPP using a coaxial electrospinning technique. This structure features a TPP/PVDF-HFP core encased within a PAN/PVDF-HFP shell, forming a dual-confinement design that limits TPP leakage and curbs corrosive side reactions. To fortify the anode interface, researchers immersed lithium metal in a 5% FEC-containing electrolyte, producing a uniform and dense LiF-rich SEI layer. Multi-modal analyses confirmed that the engineered SEI blocks TPP penetration and reduces anode corrosion depth.
Electrochemical tests validated the design: 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% of their capacity after 1500 cycles at 1 C and preserved 81.7% capacity after 6000 cycles at 10 C. “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.
This combined SEI–electrolyte strategy represents a promising direction for developing high-performance, intrinsically safer lithium metal batteries. Its ability to sustain thousands of cycles at high current densities positions it well for electric vehicles, grid-level storage, aerospace systems, and next-generation flexible pouch cells. The underlying design principle—merging chemical confinement, structural encapsulation, and deliberate SEI engineering—can be applied to other reactive anodes and high-voltage cathodes. As global demand for high-energy batteries intensifies alongside strict safety requirements, this approach may accelerate the practical adoption of lithium metal technologies.
