Nb2CT MXene: High capacity and ultra-long cycle capability for lithium-ion battery by regulation of functional groups

MXenes are well known for their potential application in supercapacitors due to their high-rate intercalation pseudocapacitance and long cyclability. However, the reported low capacity of pristine MXenes hinders their practical application in lithium-ion batteries. In this work, a robust strategy is developed to control the functional groups of Nb2CTx MXene. The capacity of pristine Nb2CTx MXene can be significantly increased by Li+ intercalation and surface modification. The specific capacity of the treated Nb2CTx is up to 448 mAh g−1 at 0.05 A g−1, and at a large current density of 2 A g−1 remains a high reversible capacity retention rate of 75% after an ultra-long cycle of 2000 cycles. These values exceed most of the reported pristine MXenes (including the most studied Ti3C2Tx) and carbon-based materials. It demonstrates that this strategy has great help to improve the electrochemical performance of pristine MXene, and the results enhance the promise of MXenes in the application of lithium-ion batteries.