Steady cycling of lithium metal anode enabled by alloying Sn-modified carbon nanofibers

Abstract

The practical application of lithium (Li) metal anode, the most promising potential candidate for upgraded Li batteries, is impeded by the uncontrollable growth of Li dendrites and the infinite volume variation during cycling. Here, a self-supporting Sn-modified porous carbon nanofiber skeleton (Sn/CNF) is constructed to boost dendrite-free Li deposition. During the initial lithiation stage, the three-dimensional skeleton with a homogeneous distribution of ultrafine Sn is activated from an in situ electrochemically generated alloying reaction of Li to form lithiophilic Li₅Sn₂. The Li₅Sn₂ alloy delivers a low nucleation overpotential, works as continuous Li nucleation grains, and homogenizes Li⁺ flux with fast charge-transfer kinetics. Meanwhile, restrained volume expansion with large Li accommodation is available owing to the confinement of Li plating on the high porous Sn/CNF with fine mechanical properties. As expected, a prolonged lifespan of symmetrical cells of Sn/CNF@Li for 2000 h at 0.5 mA cm⁻² with a low polarization is achieved. The cell with a LiFePO₄ cathode exhibits steady cycling for 300 cycles with an average coulombic efficiency of 99.6%. This work offers new insights for alloy-modified three-dimensional scaffolds to guide Li nucleation and ionic transport for Li-metal anode.