A novel Ni3N/graphene nanocomposite as supercapacitor electrode material with high capacitance and energy density

Abstract

A novel Ni₃N/graphene nanocomposite of small Ni₃N nanoparticles anchoring on the reduced graphene oxide nanosheets has been successfully synthesized. Due to the quite small size of Ni₃N nanocrystals, the surface for faradic redox reaction of pseudocapacitive materials dramatically increases. The main issue of the volume change obstructing the pseudo-supercapacitor performance is concurrently resolved by the tight attachment of Ni₃N nanoparticles with flexible texture. Importantly, the two-step oxidation/reduction reaction between Ni(I) and Ni(III) endows this nanocomposite with large capacitance by providing more faradic charge. The kind of electrode material behaves excellently both in three-electrode and asymmetric supercapacitors. The biggest specific capacitance reaches to 2087.5 F g⁻¹ (at 1 A g⁻¹), and its asymmetric supercapacitor cell with ethylene glycol modified RGO as negative electrode has a high energy density (50.5 W h kg⁻¹ at 800 W kg⁻¹). The cell capacitance retention exceeds 80% after 5000 cycles at different high current densities, showing its promising prospects for high-energy supercapacitors.