In‐Situ Synergistic 2D/2D MXene/BCN Heterostructure for Superlative Energy Density Supercapacitor with Super‐Long Life

The 2D/2D layered materials are gaining much‐needed attention owing to the unprecedented results in supercapacitors by their robust structural and electrochemical compatibility. Here, a facile scalable synthesis of 2D/2D MXene/boron carbon nitride (BCN) heterostructure through no residue direct pyrolysis is reported. The process allows the in‐situ growth of BCN nanosheets unravelling the surfaces of MXene synergistically that provide an interconnected conductive network with wide potential window, augmented proportion of Ti sites at elevated temperature removing terminal groups enabling high pseudocapacitive activity and impressive stability. As a result, the as‐assembled MXene/BCN electrode records a high specific capacitance of 1173 F g−1 (1876 C g−1) at 2 A g−1 and an energy density of 45 Wh kg−1. Further, the fabricated solid‐state device exhibits an ultra‐high cyclability of 100% capacitive retention after 100 000 cycles. This will be an epitome for future 2D/2D heterostructures with commendable electrochemical properties as an expedient solution for energy storage applications. This work communicates facile and scalable preparation of synergistically interplayed 2D/2D MXene/boron carbon nitride (BCN) heterostructure allowing in‐situ BCN nanosheet growth on MXene. Owing to interconnected conductive network, the electrode delivered high energy density of 45 Wh kg−1 at wider potential of 1.6 V, the solid‐state device exhibits a stability over 100 000 cycles with no capacitive decay.