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

•We report a facile method for synthesis of nano-Si embedded in Si7Ti4Ni4 complex.•Microstructure change of Si7Ti4Ni4 relaxes volume expansion of Si.•Si7Ti4Ni4 inhibits further synthesis of SEI layer.•Discharge capacity is maintained at almost 800 mAh g−1 over 50 cycles.•It retains 86% of capacity at 3200 mA g−1 compared to that of 400 mA g−1.

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, Si7Ti4Ni4 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 Si7Ti4Ni4 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 Si7Ti4Ni4 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 Si7Ti4Ni4 can be a promising anode material for lithium ion batteries.