In-situ etching and ion exchange induced 2D-2D MXene@Co9S8/CoMo2S4 heterostructure for superior Na+ storage

2D-2D MXene@Co9S8/CoMo2S4 heterostructure has been successfully prepared by anchoring Co9S8/CoMo2S4 nanosheets on few-layered MXene through In-situ etching and ion exchange methods, as well as the subsequent sulfidation processes. MXene flakes used as substrate can effectively suppress the aggregation of Co9S8/CoMo2S4 nanosheets, which further increase reactive sites, ensure the full contact/infiltration of electrolyte, as well as promote charge transfer to improve the reversibility of redox reactions. Besides, this hierarchical structure of 2D-2D MXene@Co9S8/CoMo2S4 hybrids can provide buffer space for the volume expansion of electrode materials during the discharge/charge process. When applied as anode for SIBs, the hierarchical hybrids present superior electrochemical performances with outstanding rate capability (172 mAh/g at 5.0 A/g) and cycling stability (196 mAh/g at 1.0 A/g after 350 cycles), which were further demonstrated by the Ex-situ XRD and XPS results. This work provides an effective way to prepare heterostructure hybrid by combining MXene with binary metal sulfides with unexpected performance in SIBs and may develop hybrid electrode materials for further application in commercial SIBs.