Enhancing energy storage systems with nickel boride (MBene) electrodes

Abstract

In this study, nickel boride (Ni₂B), an innovative member of the MBene family, was synthesized with high crystallinity via chemical vapor deposition (CVD) and evaluated as a cathode material for supercapacitor applications. MBene materials are particularly attractive due to their metal-like conductivity combined with boron-rich surface chemistry, providing distinct advantages for electrochemical energy storage. In our work, Ni₂B films were directly deposited onto conductive Cu substrates without binders, ensuring homogeneous and strong adhesion. Structural and morphological analyses using Raman spectroscopy, XRD, SEM, and AFM revealed a patterned high-surface-area morphology that enhances ion transport. Electrochemical measurements in a symmetric configuration with 1 M Na₂SO₄ electrolyte demonstrated a specific gravimetric capacitance of 455 F g⁻¹, a specific areal capacitance of 20 mF cm⁻², and excellent rate capabilities. The device exhibited a power density of 28.4 kW kg⁻¹, an energy density of 63.2 Wh kg⁻¹, and 99% capacitance retention over 20 000 cycles, confirming its outstanding electrochemical stability. These results highlight that CVD-grown Ni₂B uniquely combines high crystallinity, tailored surface functionality, and superior electrochemical performance, establishing it as a novel and promising candidate for next-generation asymmetric or hybrid supercapacitor systems.