Route of irreversible transformation in layered tin thiophosphite and enhanced lithium storage performance

Abstract

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 LiNi0.33Co0.33Mn0.33O2 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.