Jeffrey Bell, Rachel Ye, Kazi Ahmed, Chueh Liu, Mihrimah Ozkan, Cengiz S. Ozkan
Here we present a low cost, free-standing, high capacity, stable, and environmentally benign nickel–nickel oxide (Ni–NiO) nanofiber cloth anode for Li-ion batteries. Ni–NiO nanofibers are fabricated by simple electrospinning and thermal oxidation processes which create a free-standing, core–shell nanofiber structure. The nickel backbone mitigates poor conductivity issues observed in Li-ion anodes due to repeated volume change during lithiation/delithiation. The Ni–NiO nanofiber anode possesses a high surface area compared to that of a slurry cast electrode which helps facilitate Li-ion diffusion into the active material. Electrochemical impedance spectroscopy indicates improved capability of current collecting metal (nickel in this case) to withstand volume change in our free-standing structure. Furthermore, scanning electron microscopy indicates the stability of the Ni–NiO nanofiber cloth anode in excess of 400 charge/discharge cycles, partly evidenced by the stable evolution of solid-electrolyte interphase. As an anode, the Ni–NiO nanofiber cloth shows impressive results with a gravimetric capacity of 1054 mA h g−1 at a current density of 2154 mA g−1 or 3 C (1 C=718 mA g−1), a long cycle life of more than 1500 cycles, and exceptional stability throughout its cycle life with a Coulombic efficiency >99%. Performance evaluation enables the Ni–NiO cloth material for next-generation high capacity, high rate, stable, and environmentally benign Li-ion batteries.