A MOF-MXene-BN three-component heterostructure exhibits impressive pseudocapacitive behavior with fast charge injection facilitated by an ultrathin dielectric h-BN. To address the MOF's low electronic conductivity, a 2D NiCo-MOF is grown on MXene nanosheets, enhancing conductivity and providing abundant redox-active sites. BN (boron nitride) serves a dual purpose, preventing restacking and facilitating charge injection toward NiCo-MOF. Synergistic contributions of 2D materials and a heterostructure with favorable charge injection dynamics among MOF, MXene, and BN contribute to enhanced electrochemical performance. Charge transfer mechanisms are elucidated using distribution of relaxation time technique to analyze complex EIS data and to differentiate electrode kinetics based on their respective relaxation time constants. An asymmetric supercapacitor, MOF-MXene-BN//activated carbon, achieves a specific capacity of 798 C/g, an energy density of 81 Wh/kg at 365 W/kg, and 81% capacitance retention over 5,000 cycles.