Synthesis of mesoporous Zn-doped MnCo2O4 nanoparticles for high-energy density solid-state asymmetric supercapacitor

Abstract

This study aims to determine how Zn doping at the cobalt site of MnCo2O4 (MCO) affects its electrochemical properties. Synthesized MnZn0.4Co1.6O4 (0.4ZMCO) sample's electrode provides an enormous improvement in electrochemical characteristics as compared to that of MCO because of its higher BET surface area (74 m2/ g) and mesoporous distribution of pore sizes. The 0.4ZMCO exhibits specific capacitances of 720 F g−1 at 0.5 A g−1, along with satisfactory rate capability. In addition, this electrode exhibits outstanding cyclability, maintaining a capacitance retention of 91 % and a coulombic efficiency of 99.78 % throughout 10,000 continuous cycles, even under high current density of 10 A g−1. An asymmetric supercapacitor (ASC) device is constructed using 0.4ZMCO as the cathode and activated carbon as the anode electrode. This ASC device performs with a good specific energy density of 49 Wh kg−1 and a power density of 8.64 kW kg−1. Furthermore, the ASC device exhibits 99.40 % coulombic efficiency and 91.84 % capacitance retention up to 30,000 GCD cycles in PVA/KOH gel electrolyte at a specific current density of 8 A g−1. Additionally, a single device illuminates a red LED, while connecting two devices in series illuminates red and green LED for more than 15 and 12 min, respectively. We believe Zn-doped MCO has great potential in constructing higher-performance supercapacitor devices due to its straightforward synthesis process and excellent electrochemical properties.