Interlayer engineering of Ti3C2Tx MXene towards high capacitance supercapacitors
Electrochemical pseudocapacitors store energy via intercalation or electrosorption and Faradaic charge transfer with redox reactions. MXenes represent the promising intercalation pseudocapacitive electrode materials for supercapacitors due to their ultrahigh theoretical capacitances. Achieving the high capacitance will greatly advance the large-scale applications as in power grids. However, a rational design concept has not been exploited to approach the theoretical limit. Here, we show how interlayer engineering helps to approach the limit. Interlayer engineering in such a way that simultaneously creating a broadened yet uniform interlayer spacing-providing a “highway” for fast ion diffusion and incorporating heteroatoms with lower electronegativity-offering “trucks” (redox active sites) on such a “highway” for speeding charge transfer, enables high capacitance. Following the concept, through annealing the as-prepared Ti3C2Tx MXene in ammonia atmosphere, the engineered MXene delivers much improved capacitance with excellent rate performance and cyclability. The overall performance of the engineered MXene outperforms all other pseudocapacitive electrode materials.