NiO@MXene Nanocomposite as an Anode with Enhanced Energy Density for Asymmetric Supercapacitors

MXene composites with different metal oxides have recently demonstrated good electrochemical performance with enhanced conductivity and also hinder the restacking of MXene. With this motivation, we synthesized the nickel oxide@MXene (NO@MXene) series with varying compositions, which was screen printed on a flexible stainless-steel mesh (FSSM) substrate as an anode for a supercapacitor. The effect of sample composition, i.e., 5% NO@MX, 10% NO@MX, 15% NO@MX, and 20% NO@MX, on the electrochemical properties is studied systematically. The 15% NO@MX composite electrode demonstrated a maximum capacitance of 1542 F g-1@6 mA cm-2 current density in 1 M KOH. An all-solid-state asymmetric supercapacitor (ASC) with 15% NO@ MX (anode) and copper oxide (cathode) displayed a 1 V potential window. The device exhibited a specific capacitance of 73.3 F g-1@10 mA cm-2 current density with a maximum energy density of 10.7 Wh kg-1 and a power density of 3333 W kg-1 in polymer gel of PVA-KOH electrolyte. The cyclic stability of the device demonstrates 90.6% capacitance retention over 5000 cycles. It is envisaged that 15% NO@MX as an anode would serve as a promising electrode for the all-solid-state device for supercapacitor applications.