Wet-chemical assisted synthesis of MnSe/ZnO nanostructures as low-resistance robust novel cathode material for advanced hybrid supercapacitors

Abstract

Electrode materials are the key to defining the overall electrochemical performance of energy storage devices and have been an essential hot topic for decades. This study synthesized MnSe-based ZnO composites with MnSe weight ratios (10 and 40%) denoted as ZK-1 and ZK-2 using a simple, cost-effective and economical wet-chemical technique. It investigated their electrochemical characteristics for high-performance hybrid supercapacitors. The comparatively lower resistance of MnSe than that of ZnO (2.40 Ω and 1.45 Ω, respectively) and ZK-2 relative to ZK-1 (1.10 Ω and 0.8 Ω, respectively) give the evident advantages of an improved capacitive energy storage performance owing to their fast faradaic redox reactions due to Mn³⁺/Mn⁴⁺, superior charge storage process, good reversibility and high capacitances of 470 F g⁻¹ and 680 F g⁻¹ at low current rates, respectively. More specifically, at 12 000 cycles, an extraordinarily steady cycling stability of 95.5% was achieved, with a superior energy and power supply of 57.8 W h kg⁻¹ at 13 005 W kg⁻¹ and deficient solution and charge transfer resistance of 1.3 and 6.4 when built as a ZK-2‖AC hybrid supercapacitor. The capacitance, energy and power densities, and low resistance prove the synergistic effect between the MnSe and ZnO nanostructures in a hybrid supercapacitor. Notably, a stable voltage window of 1.75 V in an aqueous solution as an electrolyte boosts the capacitance and power delivery, and thus these seem to be promising electrode materials for advanced hybrid supercapacitors.