Lithium metal batteries offer exceptional energy density but face challenges from dendrite growth and flammability. A new study published in Carbon Energy (DOI: 10.1002/cey2.70077) presents a strategy that combines a pre-formed LiF-rich solid electrolyte interphase (SEI) with a dual-confinement flame-retardant gel polymer electrolyte to stabilize the lithium metal anode and enhance safety.
The research, conducted by scientists from Hebei University of Science and Technology, City University of Hong Kong, and Hainan University, addresses the corrosion caused by triphenyl phosphate (TPP) in flame-retardant electrolytes. High TPP concentrations improve fire resistance but degrade battery life. The team designed a gel polymer electrolyte with 70 wt.% TPP using coaxial electrospinning, creating a core-shell structure that confines TPP molecules and reduces leakage. This dual-confinement design maintains flame retardancy while mitigating side reactions.
To protect the lithium anode, the researchers immersed it in a 5% FEC-containing electrolyte, forming a uniform LiF-rich SEI layer. Analyses using UV-vis spectroscopy, TOF-SIMS, XPS, and AFM confirmed that the engineered SEI blocks TPP penetration and reduces corrosion. The LiF layer also enhances lithium-ion mobility and promotes smooth plating, as reported in the study.
Electrochemical tests demonstrated significant improvements: 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 tests, LFP||Li cells retained 98.9% capacity after 1500 cycles at 1 C and 81.7% capacity after 6000 cycles at 10 C, showing exceptional endurance under fast charging. The lead corresponding scientist noted, "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."
The study was supported by the National Natural Science Foundation of China (52404316, 52474325), the S&T program of Hebei Province (225A4404D), the Natural Science Foundation of Hainan Province (524RC475), the Collaborative Innovation Center of Marine Science and Technology of Hainan University (XTCX2022HYC14), and the Xingtai City Natural Science Foundation (2023ZZ027). The findings suggest a practical route for developing intrinsically safer lithium metal batteries for applications in electric vehicles, grid storage, aerospace, and flexible devices. More broadly, the design principle of combining chemical confinement, structural encapsulation, and SEI engineering could be applied to other reactive anodes and high-voltage cathodes, as detailed in the related link.
