Free-Standing 3D-Sponged Nanofiber Electrodes for Ultrahigh-Rate Energy-Storage Devices

We have designed a self-standing anode built-up from highly conductive 3D-sponged nanofibers, that is, with no current collectors, binders, or additional conductive agents. The small diameter of the fibers combined with an internal spongelike porosity results in short distances for lithium-ion diffusion and 3D pathways that facilitate the electronic conduction. Moreover, functional groups at the fiber surfaces lead to the formation of a stable solid-electrolyte interphase. We demonstrate that this anode enables the operation of Li-cells at specific currents as high as 20 A g^-1 (approx. 50C) with excellent cycling stability and an energy density which is >50% higher than what is obtained with a commercial graphite anode.