Free-Standing Hollow Carbon Fibers as High-Capacity Containers for Stable Lithium Metal Anodes

Lithium metal has been deemed as the most attractive anode due to its high theoretical capacity and low anode potential. Unfortunately, its development still faces various challenges, including dendritic Li growth and low Coulombic efficiency. Here, we demonstrate that a light-weight, flexible, and free-standing 3D hollow carbon fiber (3D-HCF) container with high electroactive surface area can significantly reduce local current density and improve the Li deposition behavior. Li is confined within the interspace among the fibers and inside the hollow tubular fibers without uncontrollable Li dendrites. The Li anode in the 3D-HCFs exhibits high Coulombic efficiency (similar to 99.5% over 350 cycles), large areal capacity, and long-running lifespan (>1,200 hr) with an exceptionally low overpotential (<20 mV). A full cell with a LiFePO4 cathode shows flat voltage profiles and good cycle life. We expect this work to inspire other Li container designs to promote the development of Li metal anodes.