Si₇Ti₄Ni₄ as a buffer material for Si and its electrochemical study for lithium ion batteries

Nano-Si embedded Si₇Ti₄Ni₄ is synthesized with the melt spinning method, which is facile, and applicable to mass-production. Si₇Ti₄Ni₄, the buffer material, is electrochemically inactive toward lithium. Nevertheless, Si ₇Ti₄Ni₄ has good electrical conductivity, in the order of 10⁵ S m^-1, which is more conductive than amorphous carbon that is usually used as a coating material for active material. Furthermore, the surrounding grain boundaries of Si₇Ti ₄Ni₄ effectively relax volume expansion of Si. Therefore, it plays a critical role in maintaining the structure of electrode and the integrity of active materials. As a result, nano-Si embedded in Si ₇Ti₄Ni₄ shows outstanding cycle performance over 50 cycles at 400 mA g^-1, and it maintains 86% of its specific capacity at 3200 mA g^-1, compared with that of 400 mA g^-1. This indicates that nano-Si embedded in Si₇Ti₄Ni ₄ can be a promising anode material for lithium ion batteries.