Silicon Diphosphide: A Si-Based Three-Dimensional Crystalline Framework as a High-Performance Li-Ion Battery Anode

The development of an electrode material for rechargeable Li-ion batteries (LIBs) and the understanding of its reaction mechanism play key roles in enhancing the electrochemical characteristics of LIBs for use in various portable electronics and electric vehicles. Here, we report a three-dimensional (3D) crystalline-framework-structured silicon diphosphide (SiP<sub>2</sub>) and its interesting electrochemical behaviors for superior LIBs. During Li insertion in the SiP<sub>2</sub>, a three-step electrochemical reaction mechanism, sequentially comprised of a topotactic transition (0.55–2 V), an amorphization (0.25–2 V), and a conversion (0–2 V), was thoroughly analyzed. On the basis of the three-step electrochemical reaction mechanism, excellent electrochemical properties, such as high initial capacities, high initial Coulombic efficiencies, stable cycle behaviors, and fast-rate capabilities, were attained from the preparation of a nanostructured SiP<sub>2</sub>/C composite. This 3D crystalline-framework-structured SiP<sub>2</sub> compound will be a promising alternative anode material in the realization and mass production of excellent, rechargeable LIBs.