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 sul-fides with unexpected performance in SIBs and may develop hybrid electrode materials for further application in commercial SIBs.