Unlocking High-Energy Metal Fluoride Cathodes through Modulated Interfacial Kinetics

Conversion-type cathodes with multiple-electron transfer capability are a promising platform for high-energy lithium-ion batteries. However, their full potential is often unrealized due to sluggish kinetics at the nanoscale, where complex phase transformations disrupt charge transport and ultimately limit performance. To address this fundamental challenge, we reconcile the contrasting electrochemical reversibility of the isostructural FeF₂ and CuF₂ cathode, the latter of which has historically been limited by irreversibility. By infiltrating liquid gallium (Ga) into a CuF₂/carbon matrix, a percolation network (pGa-CuF₂/C) is established, enabling reversible two-electron transfer nanoscale conversion via a displacement-reaction pathway, similar to that of FeF₂. Our mechanistic studies reveal that the Ga interlayer retards fluorine mobility, fostering the Li₂CuF₄ intermediate phase. Crucially, Ga synergistically minimizes the lattice mismatch and interfacial energy at Li₂CuF₄|Cu interfaces, ensuring homogeneous nucleation and the formation of a bicontinuous copper network interconnected with LiF. An optimized pGa-CuF₂/C@TiO₂ core-shell structure achieves a notable capacity of ∼300 mAh/g at an average voltage of 2.8 V after 20 cycles. These mechanistic insights demonstrate that interfacial kinetics dictate the pathway of conversion reactions, highlighting the importance of modulating interfacial energy and lattice mismatch to unlock the broader potential of conversion cathodes.