Kinetics-driven high power Li-ion battery with a-Si/NiSix core-shell nanowire anodes

Anode architectures are closely related with Li-ion battery performance, particularly when the anodes are three-dimensional at the nanometer scale. Therein, the achievable electrochemical capacity and the power characteristics are inherently determined by a series of phase transitions involved in the anode during lithiation/delithiation. Here, we report an amorphous-silicon (a-Si) supported by metallic NiSi_x nanowire (NW) core grown by simple two-step SiH4 CVD on Ni films for a Li-ion battery anode structure, where the metallic core act as a mechanical supporter and supplies kinetically unlimited electron transport. We achieved the highly reversible capacity over 3000 mAh/g even at 2C rate with its stable cyclic retention. We argue that a-Si/NiSi_x NW follow a potentially ideal route for reversible and fast phase transitions, compared to bare Si NWs, and thus can provide implication for the high power and high capacity energy storage devices.