Embedding amorphous MoSx within hierarchical porous carbon by facile one-pot synthesis for superior sodium ion storage

Abstract

The design of anode materials with a high specific capacity, high cyclic stability, and superior rate performance is required for the practical applications of sodium-ion batteries (SIBs). In this regard, we introduce in this work a facile, low-cost and scalable method for the synthesis of nanocomposites of amorphous molybdenum sulfide (a-MoSx) and hierarchical porous carbon and have systematically investigated their performance for sodium ion storage. In the synthesis, ammonium molybdate tetrahydrate and thioacetamide are used as molybdenum and sulfur sources, respectively, with abundant corn starch as the carbon source and KOH as an activation agent. A simple pyrolysis of their mixtures leads to the formation of nanocomposites with a-MoSx embedded within a hierarchical porous carbon (MoSx@HPC), which are featured with a high surface area of up to 518.4 m2 g−1 and hierarchical pores ranging from micropores to macropores. It has also been shown that the annealing of MoSx@HPC results in the formation of crystalline MoS2 nanosheets anchored in the hierarchical porous carbon matrix (MoS2@HPC). The as-prepared nanocomposite MoSx@HPC1 at an optimum carbon content of 32 wt% delivers a high specific sodium storage capacity of 599 mAh g−1 at 0.2 A g−1 and a high-rate performance with a retained capacity of 289 mAh g−1 at 5 A g−1. A comparison of the electrochemical performances of MoSx@HPC and MoS2@HPC demonstrates the superior specific capacity, rate performance, and charge transfer kinetics of the former, highlighting the unique advantageous role of amorphous MoSx relative to crystalline MoS2.