MnO2-Carbon Nanotube Electrodes for Supercapacitors with High Active Mass Loadings

MnO2-carbon nanotube electrodes with high active mass loadings for supercapacitors have been fabricated with the goal of achieving a high area normalized capacitance, low impedance and enhanced capacitance retention at high charge-discharge rates. Interface synthesis and liquid-liquid extraction of MnO2 particles produced non-agglomerated MnO2 particles which allowed the fabrication of electrodes with good dispersion of carbon nanotubes in the MnO2 matrix. This strategy was used to fabricate electrodes with active mass loadings in the range of 21–50 mg cm−2 and mass ratios of active material to the nickel foam current collector of 0.33–0.78. The comparison of the experimental data for different extractor molecules provided an insight into the influence of the molecular structure, adsorption mechanism and interface phenomena on particle size and electrode performance. The analysis of capacitance data at different charge-discharge rates and different mass loadings was utilized to optimize electrode performance. The highest capacitance of 7.52 F cm−2 was achieved at a scan rate of 2 mV s−1 and active mass loading of 47 mg cm−2. Electrodes with mass loading of 35 mg cm−2 showed improved capacitance retention at high scan rates and the highest capacitance of 2.63 F cm−2 at a scan rate of 100 mV s−1.