Optimization of diffusion dynamics in Mn-doped Co3O4/rGO hybrid electrodes for efficient energy storage in asymmetric supercapacitors

Abstract

Use of efficient electrode materials is required to meet the growing modern-day energy needs. In this context, a series of electrodes composed of Co3O4 with varying levels of Mn doping (4% and 8%) and varying rGO contents (4% and 8%) was prepared using a combination of hydrothermal and solvothermal methods. The samples were labeled as Co3O4 (CoO), Co2.96Mn0.04O4 (MDCoO-I), Co2.92Mn0.08O4 (MDCoO-II), Co2.92Mn0.08O4@4%rGO (MDCoO-III), and Co2.92Mn0.08O4@8%rGO (MDCoO-IV). Various tests confirmed the formation of the desired phase, with X-ray diffraction showing a cubic structure that remained consistent throughout the series. Following this survey, comprehensive electrochemical testing of all samples was conducted in a three-electrode setup to identify the best candidate for practical device applications. For example, the sample (MDCoO-IV) showed enhanced ion transport properties, including ion conductivity (0.62 S/cm), transference number (0.45), rate constant (2.21×10-7 cm/s), exchange current density (0.021 A/g), and favorable diffusion behavior (1.72 ×10-13 m2/s), along with the highest energy density (121.86 Wh/kg). At this instance, a constructed asymmetric device using MDCoO-IV demonstrated good rate performance, with an energy density of 33.75 Wh/kg at 750 W/kg, and maintained 87.27% stability after 10000 cycles, with diffusion dynamics of 5.51×10-13 m2/s at 10 mA in 6 M KOH. The discovery of these features suggests that this material has potential for use in future energy storage devices.