Free-Standing N, P Codoped Hollow Carbon Fibers as Efficient Hosts for Stable Lithium Metal Anodes

Constructing 3D hosts has been verified to be an effective strategy to control Li plating/stripping behaviors. Herein, free-standing N, P codoped hollow carbon fibers (NPHCFs) are prepared and regarded as efficient host materials, which can provide more lithiophilic nucleation sites and more volume to accommodate the Li metal. scanning electron microscopy (SEM) images suggest that the Li metal is confined to both the interspace and the inside of hollow carbon fibers without uncontrollable Li dendrites. An initial Coulombic efficiency (>94.6%) is obtained for over 500 h for the NPHCF host at 0.5 mA cm-2 and 0.5 mAh cm-2. The NPHCF@Li symmetric cell successfully runs over 250 cycles at 0.5 mA cm-2 and 0.5 mAh cm-2 without obvious voltage fluctuations. More impressively, the NPHCF@Li||LiFePO4 full cell delivers a first specific discharge capacity of 164 mAh g-1 and an enhanced capacity retention ratio of ∼72.13% after 100 cycles at 0.2 C. These better results indicate that N and P cointroduced into hollow carbon fibers may be a feasible strategy to develop high-energy lithium metal anodes. This work further indicates the feasibility to develop Li metal anodes by designing lithiophilic host materials.