Amorphous phosphorus chalcogenide as an anode material for lithium-ion batteries with high capacity and long cycle life

Abstract

The ever-increasing demands for modern energy storage applications drive the search for novel anode materials of lithium (Li)-ion batteries (LIBs) with high storage capacity and long cycle life, to outperform the conventional LIBs anode materials. Hence, we report amorphous ternary phosphorus chalcogenide (a-P4SSe2) as an anode material with high performance for LIBs. Synthesized via the mechanochemistry method, the a-P4SSe2 compound is endowed with amorphous feature and offers excellent cycling stability (over 1500 mA h g−1 capacity after 425 cycles at 0.3 A g−1), owing to the advantages of isotropic nature and synergistic effect of multielement forming Li-ion conductors during battery operation. Furthermore, as confirmed by ex situ X-ray diffraction (XRD) and transmission electron microscope (TEM), the a-P4SSe2 anode material has a reversible and multistage Li-storage mechanism, which is extremely beneficial to long cycle life for batteries. Moreover, the autogenous intermediate electrochemical products with fast ionic conductivity can facilitate Li-ion diffusion effectively. Thus, the a-P4SSe2 electrode delivers excellent rate capability (730 mA h g−1 capacity at 3 A g−1). Through in situ electrochemical impedance spectra (EIS) measurements, it can be revealed that the resistances of charge transfer (Rct) and solid electrolyte interphase (RSEI) decrease along with the formation of Li-ion conductors whilst the ohmic resistance (RΩ) remains unchanged during the whole electrochemical process, thus resulting in rapid reaction kinetics and stable electrode to obtain excellent rate performance and cycling ability for LIBs. Moreover, the formation mechanism and electrochemical superiority of the a-P4SSe2 phase, and its expansion to P4S3−xSex (x = 0, 1, 2, 3) family can prove its significance for LIBs.