In situ decoration of 0D-nickel boride on 2D-vanadium MXene composites: An advanced electrode material for high-energy-density supercapacitors

Vanadium carbide-MXene (V2CTx) is considered a rising star among 2D materials and is an ideal electrode material for energy storage due to its unique features. However, oxidation and layer restacking can impair specific capacity (Cs) and cycling performance. Considering this challenge, we have developed a composite material consisting of amorphous nickel boride (NixB NPs) and V2CTx. To prevent oxidation and restacking of the layers and to improve the performance of the supercapacitor, NixB was decorated between the gaps and the surface. The V2CTx and its composites were prepared by simple etching and direct liquid-phase methods. Under the optimized conditions, the NixB/V2CTx modified nickel foam exhibited an improved Cs value of 705.9 C g−1 and a rate capability of 53.8 % at a current density of 10 A g−1; the excellent cycling stability was 120.5 % after 10,000 cycles at 10 A g−1 in 3 M KOH. The improved Cs values, shortened ion diffusion paths, swift electron transfer, and excellent cycling stability of the composites are due to the V2CTx layers surface entrapped/gaps filled by the NixB NPs. For practical application, an asymmetric device with NixB/V2CTx and reduced graphene oxide (rGO) as positive and negative electrodes was fabricated. The NixB/V2CTx//rGO device achieved a maximum energy density of 50.22 Wh kg−1 at 800 W kg−1 and 26 Wh kg−1 at 16000 W kg−1. The capacity retention was 89.98 % and the Coulombic efficiency was 99.9 % after 20,000 continuous cycles at 8 A g−1. These results emphasized that the developed 0D/2D NixB/V2CTx electrode materials with novel composite architecture are suitable for advanced energy storage applications.