Unusual Conformal Li Plating on Alloyable Nanofiber Frameworks to Enable Dendrite Suppression of Li Metal Anode

Li metal anode is deemed the most promising candidate anode for high-energy battery systems such as Li-sulfur and Li-fluoride batteries. However, some severe challenges, for example, facile formation and growth of Li dendrites, large volume evolution of hostless Li, and low Coulombic efficiency of Li plating/stripping, still hinder the commercialization of Li-metal batteries (LMBs). Herein, a free-standing and highly flexible 3D current collector made of carbon nanofibers (CNFs) conformally coated by continuous Sn layer is synthesized by electrospinning method. Sn layer enables a lithiophilic and alloyable carbon skeleton surface and provides uniform and continuous Li nucleation sites, leading to unusual conformal Li plating behavior and effective inhibition of Li dendrites. The spatial confinement of Li plating mitigates the volume expansion and network distortion of CNFs. The electric contact reinforced by Sn interlayer achieves highly reversible Li stripping for more than 850 h for CNF-Sn@Li symmetric cell. The small nucleation overpotential (28 mV) and potential polarization (14 mV for symmetric cell) benefit from the low energy barrier of Li-Sn alloying and following Li nucleation on Li-Sn layer. For CNF-Sn@Li-LiFePO4 full cell, the capacity retention ratio is as high as 92.2% after 150 cycles at 0.5C and the reversible capacities are maintained at 134.3 and 106.7 mAh g(-1) at 2C and 5C respectively. The design of 3D lithiophilic current collector instead of planar Cu is a potential solution to highly safe LMBs.