Enhanced capacitive performance of MnO2- multiwalled carbon nanotube electrodes, prepared using lauryl gallate dispersant

Abstract

Composite MnO2-multiwalled carbon nanotube (MWCNT) electrodes for electrochemical supercapacitors (ES) have been prepared by the colloidal methods based on the use of lauryl gallate (LG). In this investigation LG was used for efficient dispersion of MnO2 and MWCNT and for their improved mixing in the heterocoagulation method. Moreover, LG was utilized as a vehicle for the particle transfer in the liquid-liquid extraction method. The analysis of the experimental data provided an insight into the mechanisms of LG adsorption on MnO2 and MWCNT. It was found that the heterocoagulation method is not limited to the fabrication of MnO2-MWCNT composites. The improved mixing of the individual components allowed for improved capacitive performance of the MnO2-MWCNT electrodes. The liquid-liquid extraction method offers the additional benefit of reduced agglomeration, which resulted in improved mixing at the nanometric scale. Good capacitance performance and low impedance were achieved at high active mass loadings, which allowed for high integral and differential capacitances, especially at high charge-discharge rates. Graphene coated Ni foam current collectors allowed for significant improvement in capacitance performance of MnO2-MWCNT electrodes, compared to the electrodes prepared using uncoated Ni foam current collectors. It was found that the increase in capacitance is not related to capacitive properties of graphene. The high capacitance of 4.8Fcm−2 and excellent capacitance retention of 67% achieved in the scan rate range from 2 to 100mVs−1 are promising for practical ES applications.