New Battery Design Resolves Critical Safety-Performance Trade-off in Lithium Metal Batteries

A study published on September 23, 2025, in the journal Carbon Energy details a breakthrough in lithium metal battery technology that reconciles the long-standing conflict between high energy density and fire safety. The research, conducted by teams from Hebei University of Science and Technology, City University of Hong Kong, and Hainan University, presents a finely tuned strategy to stabilize the lithium metal anode against the corrosive effects of essential flame-retardant additives. The findings, accessible via the study's DOI 10.1002/cey2.70077, point toward a practical route for creating durable, inherently safe batteries critical for electric vehicles and grid storage.

Lithium metal anodes offer exceptional theoretical capacity but are plagued by dendrite growth and unstable chemistry, while conventional electrolytes are flammable. Gel polymer electrolytes improve safety but require large quantities of organic phosphate flame retardants like triphenyl phosphate (TPP). These additives, however, penetrate the battery's protective solid electrolyte interphase (SEI), triggering decomposition reactions that severely corrode the lithium anode and dramatically shorten battery life. This trade-off has been a major barrier to the commercial viability of lithium metal batteries.

The research team's solution involves a two-pronged approach: a novel electrolyte design and a pre-engineered anode interface. They developed a flame-retardant gel polymer electrolyte with a high 70 wt.% TPP loading using a coaxial electrospinning technique. This creates a dual-confinement structure where a TPP/PVDF-HFP composite core is physically encapsulated within a PAN/PVDF-HFP shell. Strong chemical interactions and physical containment work together to maintain high flame retardancy while curbing the leakage of TPP molecules that cause corrosive side reactions.

To fortify the anode, the researchers pre-treated lithium metal to form a uniform, dense artificial SEI layer rich in lithium fluoride (LiF). Multi-modal analyses confirmed this engineered SEI effectively blocks the penetration of TPP-derived corrosive species and substantially reduces anode corrosion depth. Beyond protection, the LiF layer enhances lithium-ion mobility, lowers activation energy for transport, and promotes smooth, dendrite-free lithium plating.

Electrochemical performance validated the design's effectiveness. Li||Li symmetric cells demonstrated remarkable stability, operating for 2400 hours at 0.5 mA cm⁻² and 1500 hours at 5 mA cm⁻². In full-cell tests with a lithium iron phosphate (LFP) cathode, the batteries retained 98.9% capacity after 1500 cycles at a 1 C rate and maintained 81.7% capacity after an extraordinary 6000 cycles at a high 10 C rate, showcasing exceptional endurance under fast-charging conditions.

The lead corresponding scientist stated that the study shows precise interface engineering is essential for advancing both safety and durability. By integrating the dual-confinement flame-retardant electrolyte with the LiF-rich artificial SEI, the team resolved the conflict between fire protection and anode stability. This approach halts severe corrosion from phosphate additives while improving lithium-ion transport for reliable high-rate, long-cycle operation.

This combined 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 well for demanding applications like electric vehicles, grid-level energy storage, aerospace systems, and next-generation flexible electronics. More broadly, the underlying design principle—merging chemical confinement, structural encapsulation, and deliberate SEI engineering—can be applied to other reactive battery materials. As global demand for high-energy batteries intensifies alongside stringent safety regulations, this advancement may accelerate the practical adoption of lithium metal technologies, potentially impacting energy storage across multiple industries.