Salting-out aided dispersive extraction of Mn3O4 nanoparticles and carbon nanotubes for application in supercapacitors

In this study, results from a conceptually new method for the preparation of Mn3O4-multiwalled carbon nanotube (MCNT) composites are presented. High active mass (HAM) Mn3O4-MCNT cathodes are prepared and tested for supercapacitors. The method is based on a salting-out aided dispersive extraction of Mn3O4 particles precipitated in an aqueous phase to isopropanol and their co-dispersion with MCNT. The use of lauryl gallate as an extractor is a key factor for the phase transfer. Lauryl gallate is used as a co-dispersant for Mn3O4 and MCNT. The mechanisms of lauryl gallate adsorption on Mn3O4 and MCNT and the salting-out aided extraction mechanism are discussed. Enhanced electrochemical performance of the electrodes with HAM of 41 mg cm-2 is achieved due to enhanced mixing and co-dispersion of Mn3O4 and MCNT. The electrodes show a high capacitance of 6 F cm-2 in aqueous Na2SO4 and low electrical resistance. The obtained areal capacitance is substantially higher than that for Mn3O4-MCNT composites, prepared by other methods. The capacitance increase during initial cycling is linked to the microstructure changes. The salting-out aided extraction method overcomes the limitations of other extraction techniques and opens a new strategy for the manufacturing of nanocomposites with advanced functional properties.