A Highly Reversible Nano-Si Anode Enabled by Mechanical Confi nement in an Electrochemically Activated Li x Ti 4 Ni 4 Si 7 Matrix

This paper reports a Si-Ti-Ni ternary alloy developed for commercial application as an anode material for lithium ion batteries. Our alloy exhibits a stable capacity above 900 mAh g − 1 after 50 cycles and a high coulombic effi ciency of up to 99.7% during cycling. To enable a highly reversible nano-Si anode, melt spinning is employed to embed nano-Si particles in a Ti 4 Ni 4 Si 7 matrix. The Ti 4 Ni 4 Si 7 matrix fulfi lls two important purposes. First, it reduces the maximum stress evolved in the nano-Si particles by applying a compressive stress to mechanically confi ne Si expansion during lithiation. And second, the Ti 4 Ni 4 Si 7 matrix is a good mixed conductor that isolates nano-Si from the liquid electrolyte, thus preventing parasitic reactions responsible for the formation of a solid electrolyte interphase. Given that a coulombic effi ciency above 99.5% is rarely reported for Si based anode materials, this alloy’s performance suggests a promising new approach to engineering Si anode materials.