Metal-ion-assisted in-situ fabrication of large-size CoNi-LDH@MXene for robust high-energy supercapacitors

MXene has attracted substantial attention in the field of electrochemical energy storage by virtue of its excellent electrical conductivity and redox activity. Nevertheless, the interaction of hydrogen bonds and van der Waals forces in interlamination made MXene is susceptible to stack and aggregate that severely limits its practical application. In this study, cubic ZIF-67 was in-situ grown on the MXene substrate, with the assistance of a metal-ion-assisted etching strategy stepwise nucleate and grow defective LDH nanosheet arrays, resulting in the formation of large-size CoNi-LDH@MXene composite electrode. The uniformly distributed LDH nanosheet arrays feature with low angle grain boundaries and further leading to the formation of oxygen vacancies, which become reactive reaction sites and offer high-speed channels for ion migration. The large-size CoNi-LDH@MXene composite electrode exhibited a substantially improved electrochemical performance of 1420 F g−1 at 1 A/g. After being assembled into an asymmetric supercapacitor, it manifests a high energy density (energy density of 58.3 Wh kg−1 at 750 W kg−1). This work demonstrates a novel strategy for in situ fabrication of robust supercapacitor devices.