Phase transfer of oxide particles for application in thin films and supercapacitors

This paper reports efficient liquid-liquid extraction strategies for concentrated suspensions of oxide particles and demonstrates the benefits of using such strategies for thin film applications and the fabrication of supercapacitor electrodes. We performed materials synthesis in an aqueous phase and achieved efficient materials transfer to an organic phase, avoiding agglomeration during the drying stage. The metal oxides, suspended in an organic solvent were used directly for the deposition of polymer-titania composite films and fabrication of Mn₃O₄-carbon nanotube composite electrodes for supercapacitors. Strategy E1 involved the modification of particles in-situ during synthesis and a Schiff base reaction with an extractor at the liquid-liquid interface. In the one-step E2 procedure the interface reactions were used for the extraction. We discuss advantages of the E1 and E2 strategies. Both strategies featured a biomimetic approach for the surface modification of the particles, which allowed for strong adsorption of the extractors. The ability to perform efficient extraction using concentrated suspensions allowed for the fabrication of Mn₃O₄–carbon nanotube electrodes with high active mass loading. The electrodes showed a capacitance of 2.63 F cm⁻², good capacitance retention at high charge-discharge rates and low impedance. The results of this investigation pave the way for the agglomerate free processing of various functional materials for applications in advanced films, coatings and devices