Two-dimensional metal carbide and nitride materials (MXenes) with controlled Cl-and O-surface terminations (MS-Ti 3 C 2 T x) were prepared by a molten salt etching route and their electrochemical properties were investigated in nitrile-based electrolytes. The results show that the power performance of MS-Ti 3 C 2 T x was greatly improved in acetonitrile (ACN)-based non-aqueous organic electrolytes, which are conventional electrolytes for electrochemical capacitors. The addition of a lithium salt to produce 2 M LiTFSI in ACN results in an increase in the specific capacitance. Moreover, replacing LiTFSI by LiFSI drastically improves the power performance of MXenes at a high scan rate (95 mAh g − 1 at 900C). These results highlight the importance of properly matching the electrolyte composition to the electrode material and shed light on MXenes as high-rate electrode materials for energy storage applications.