LiF Splitting Catalyzed by Dual Metal Nanodomains for an Efficient Fluoride Conversion Cathode

The critical challenges for fluoride conversion cathodes lie in the absence of built-in Li source, poor capacity retention, and rate performance. For lithiated fluorides, the reason to limit their competitiveness is rooted in the facile coarsing of insulating LiF (as built-in Li source) and its insufficient splitting kinetics during charging. Previous efforts on blending LiF nanodomains with reductive metal, metal oxide, or fluoride by ball-milling method still face the problems of large overpotential and low current density. Herein we propose a strategy of dual-metal (Fe–Cu) driven LiF splitting to activate the conversion reaction of fluoride cathode. This lithiated heterostructure (LiF/Fe/Cu) with compact nanodomain contact enables a substantial charge process with considerable capacity release (300 mAh g–1) and low charge overpotential. Its reversible capacity is as high as 375–400 mAh g–1 with high energy efficiency (76%), substantial pseudocapacitance contribution (>50%), and satisfactory capacity retention (at least 200 cycles). The addition of Cu nanodomains greatly catalyzes the kinetics of Fe–Cu–F formation and decomposition compared with the redox process of Fe–F, which lead to the energy and power densities exceeding 1000 Wh kg–1 and 1500 W kg–1, respectively. These results indicate that LiF-driven cathode is promising as long as its intrinsic conductive network is elegantly designed.