Mo-doped VS4 with interlayer-expanded and engineering sulfur vacancies as cathode for advanced magnesium storage

Abstract Magnesium ion batteries (MIBs) are considered as the next potential candidate due to the low reduction potential, high theoretical volumetric capacity, economicaland low degree of dendrite formation. However, it is still a great challenge for enhancing its electrochemical properties by decorating cathode materials. Herein, Mo-doped VS4 with various Mo content has been synthesized via one-step hydrothermal method. The characterization results show that Mo-doping not only regulate the morphology and enhance the electrical conductivity, but also expand the interlayer spacing and generate rich sulfur vacancies. Based on the synergistic effect of above various factors, Mo-doping has shortened the diffusion path for fast reaction kinetics, maintained the structure stability and provided more active sites for the increasing of reversible capacity, resulting in the excellent electrochemical properties. As for Mo-doped VS4 with various Mo content, 3% Mo-VS4 exhibits the superior cycling stability with the high specific capacity about 120 mAh g−1 at 50 mA g−1 over 350 cycles and excellent rate performance under the high current density of 500 mA g−1. In addition, pesudocapaticance-like contribution analysis as well as galvanostatic intermittent titration technique (GITT) further confirm that rich sulfur vacancies and hollow flower-like microsphere are beneficial for the fast Mg2+ diffusion and enhanced reaction kinetics. Our design strategy of the metal ion doping provides a favorable reference for developing various alkali metal ion batteries.