Lithiophilic CoF2@C hollow spheres towards spatial lithium deposition for stable lithium metal batteries

Lithium metal (LM) is a promising anode for next-generation batteries due to its high theoretical capacity and low electrode potential. Nonetheless, side reactions, volume change, and unwanted lithium dendrite growth seriously limit the practical application of LM. Herein, with the aid of a hard template approach, a novel lithiophilic CoF2-carbon hollow sphere (CoF2@C-HS) composite material is successfully prepared via a facile in-situ fluorination and etching strategy. The lithiophilic CoF2 acts as nucleation sites to reduce nucleation overpotential as well as induces the spatial Li deposition and the formation of LiF-rich solid electrolyte interphase (SEI), and the hollow carbon matrix can enhance the electrical conductivity and offer free space for LM deposition. Theoretical simulations reveal that the synergistic effect of lithiophilic CoF2 and hollow carbon matrix homogenizes the electric field distribution and Li+ flux. Benefiting from these advantages, the CoF2@C-HS-modified copper substrate electrode delivers an enhanced Coulombic efficiency (CE) of 93.7% for 280 cycles at 1 mA cm−2 and 1 mA h cm−2. The symmetrical cell using CoF2@C-HS can stably cycle more than 1800 h with a low voltage hysteresis of 11 mV at a current density of 0.5 mA cm−2 and an areal capacity of 0.5 mA h cm−2. Moreover, the Li@CoF2@C-HS composite anode enables more than 300 stable cycles at 1 C with a capacity retention of 95% in LiFePO4-based full cell and 110 stable cycles at 1 C in LiNi0.8Co0.1Mn0.1O2 (NCM811)-based high-voltage full cell. This work might shed a new light on designing lithiophilic hosts to spatially confine LM deposition, realizing dendrite-free LM anodes and the practical applications of LM batteries.