An Advanced MoS 2 / Carbon Anode for High-Performance Sodium-Ion Batteries

attracted much attention due to low cost, large resource availability, and similar insertion chemistry with lithium ions. [ 4–6 ] Inspired by Li-ion battery chemistry, a large number of cathode materials such as transitional metal oxides were investigated in Na-ion batteries. [ 7,8 ] However, there are not as many attempts on improving electrochemical performance of anode materials as that for cathode materials. Up to now, proposed anode materials include carbonaceous materials, [ 9 ] Na-alloys (Sn, Sb) [ 10,11 ] and binary compounds (metal oxides, metal sulfi des). [ 12–14 ] Due to the similar chemistry to Li-ion batteries, carbonaceous anode materials are widely used in Na-ion batteries. [ 15 ] Recent reports on carbon nanosheet derived from peat moss [ 16 ] and hollow carbon nanowires [ 17 ] demonstrate a reversible sodium-ion intercalation/deintercalation with specifi c capacities in the range of 200–300 mAh g −1 . Some metals (Sn, Sb) can alloy with Na exhibiting high capacities of 400–600 mAh g −1 . [ 10,11 ] However, it is very diffi cult to maintain the high capacity during charge/discharge cycles due to large volume change. To this regard, anode materials with high capacity and superior cycling stability are urgently needed for Na-ion batteries. Molybdenum disulfi de (MoS 2 ) is a promising anode for high performance sodium-ion batteries due to high specifi c capacity, abundance, and low cost. However, poor cycling stability, low rate capability and unclear electrochemical reaction mechanism are the main challenges for MoS 2 anode in Na-ion batteries. In this study, molybdenum disulfi de/carbon (MoS 2 /C) nanospheres are fabricated and used for Na-ion battery anodes. MoS 2 /C nanospheres deliver a reversible capacity of 520 mAh g −1 at 0.1 C and maintain at 400 mAh g −1 for 300 cycles at a high current density of 1 C, demonstrating the best cycling performance of MoS 2 for Na-ion batteries to date. The high capacity is attributed to the short ion and electron diffusion pathway, which enables fast charge transfer and low concentration polarization. The stable cycling performance and high coulombic effi ciency (∼100%) of MoS 2 /C nanospheres are ascribed to (1) highly reversible conversion reaction of MoS 2 during sodiation/desodiation as evidenced by ex-situ X-ray diffraction (XRD) and (2) the formation of a stable solid electrolyte interface (SEI) layer in fl uoroethylene carbonate (FEC) based electrolyte as demonstrated by fourier transform infrared spectroscopy (FTIR) measurements. Sodium-Ion Batteries