Sandwich-like high-performance Ti3C2Tx MXene/NiCo2O4 nanosphere composites for asymmetric supercapacitor application

NiCo 2 O 4 is a promising electrode material for supercapacitors due to its low cost, high theoretical specific capacitance and good cycling stability. However, NiCo 2 O 4 has the disadvantages of poor electronic and ionic conductivities and easy agglomeration. Moreover, the irreversible structural damage caused by the NiCo 2 O 4 volume expansions during charging and discharging limits its use in supercapacitors. Herein, we fabricated sandwich Ti 3 C 2 T x MXene/NiCo 2 O 4 composites via an electrostatic self -assembly method. The problem of easy agglomeration of the NiCo 2 O 4 nanospheres was solved by intercalating Ti 3 C 2 T x MXene layers with the NiCo 2 O 4 nanospheres. Furthermore, the Ti 3 C 2 T x MXene layer was also utilized as a protective layer to limit serious volume expansion and protect the structure of NiCo 2 O 4 nanospheres from destruction. The results showed that the prepared Ti 3 C 2 T x MXene/NiCo 2 O 4 composite exhibited a high specific capacitance of 1025 F g -1 at a current density of 1 A g -1 and had an initial capacity of 81 % when the current density was increased to 10 A g -1 . The Ti 3 C 2 T x MXene/NiCo 2 O 4 composite cathode and activated carbon anode were assembled in an asymmetric supercapacitor, which showed an energy density of 36.67 Wh kg - 1 at 800 W kg - 1 and a capacity retention of 88.2 % after 5000 cycles.