Route of Irreversible Transformation in Layered Tin Thiophosphite and Enhanced Lithium Storage Performance

Novel materials with high lithium-storage capacities are indispensable to substantially increase the gravimetric and volumetric energy densities of lithium-ion batteries. In this context, metal thiophosphites (MTPs) possessing a layered structure are considered ideal candidates to serve as alkali-ion hosts. Herein, the lithium storage properties of layered tin thiophosphite (SnPS₃) crystals have been investigated in coin-cell configuration. The results reveal that SnPS₃ undergoes a conversion and alloying reaction to deliver high lithiation capacities. The SnPS₃ anode delivered a significant lithiation capacity of ∼800 mAh g^-1 at a specific current of 100 mA g^-1. Moreover, the layered structure was able to accommodate the volume changes upon (de)lithiation as evident from its excellent cycling stability. Additionally, the SnPS₃ anode demonstrated excellent rate capability as well and delivered ∼315 mAh g^-1 at a high specific current of 2 A g^-1. Furthermore, the lithium-storage mechanism was investigated through cyclic voltammetry and ex situ X-ray diffraction and X-ray photoelectron spectroscopy studies. Studies of SnPS₃ anode in a full cell configuration by coupling with commercial LiNi_0.33Co_0.33Mn_0.33O₂ cathode are also presented. The outstanding electrochemical performance demonstrated by the SnPS₃ anode calls for further research into this novel class of metal thiophosphites for energy storage applications.