Te-S covalent bond induces 1T&2H MoS2 with improved potassium-ion storage performance.

Abstract

The modulation of the characteristics of an MoS2 anode via substitutional doping, particularly N, P and Se, is vital for promoting the potassium-ion storage performances. However, these traditional chalcogen doping can only take the place of a sulfur element and not essentially change the inherent electrical nature of MoS2. Herein, novel Te-MoS2 materials have been synthesized via a simple hydrothermal process under Te doping. A half-metallic Te occupies the position of an Mo atom to form Te-S bonds, which is different from the same group Se element. After theoretical modeling and electrochemical measurements, it was observed that the formation of Te-S bonds can increase the electrical conductivity (about 530 times increment) and mitigate the mechanical stress to ensure the whole structural stability during the repeated insertion/extraction of K-ions. Moreover, the insertion of Te into the lattice of MoS2 generated the fractional phase transformation from 2H to the 1T phase of MoS2 and 1T&2H in-plane hetero-junction. Benefiting from these advantages, the 1T&2H Te-MoS2 anode delivered high capacities of 718 and 342 mA h g-1 at 50 and 5000 mA g-1, respectively, and an ultra-stable cycling performance (88.1% capacity retention after 1000 cycles at 2 A g-1). Moreover, the potassium-ion full cell assembled with K2Fe[Fe(CN)6] as the cathode demonstrates its practical application.