Electrochemical Li Topotactic Reaction in Layered SnP for Superior Li-Ion Batteries.

The development of new anode materials having high electrochemical performances and interesting reaction mechanisms is highly required to satisfy the need for long-lasting mobile electronic devices and electric vehicles. Here, we report a layer crystalline structured SnP and its unique electrochemical behaviors with Li. The SnP was simply synthesized through modification of Sn crystallography by combination with P and its potential as an anode material for LIBs was investigated. During Li insertion reaction, the SnP anode showed an interesting two-step electrochemical reaction mechanism comprised of a topotactic transition (0.7-2.0 V) and a conversion (0.0-2.0 V) reaction. When the SnP-based composite electrode was tested within the topotactic reaction region (0.7-2.0 V) between SnP and LiSnP (x ≤ 4), it showed excellent electrochemical properties, such as a high volumetric capacity (1st discharge/charge capacity was 840/663 mA h cm) with a high initial coulombic efficiency, stable cycle behavior (636 mA h cm over 100 cycles), and fast rate capability (550 mA h cm at 3C). This layered SnP anode will be applicable to a new anode material for rechargeable LIBs.