Biomass-based 3D micro-meso-macroporous carbon for hybrid-capacitance characteristics and incredible energy density: Reversible charge transfer of multivalent Mn ions

Abstract

To achieve the coordination of energy density and power density, the metal oxide (MnO2) that endow pseudo-capacitance in 3D porous carbon can build high energy density and specific capacitance at high-power density. Here we have showed the synthetization of a composites (JSPCC-MnO2) with a specific capacitance of 310.6 F/g, an energy density of 42.4 Wh/kg, and a power density of 1425 W/kg. The percentage of pseudo-capacitance caused by the element Mn is 31.17 %, the pseudo-capacitance process of the JSPCC-MnO2 has involved reversible charge transfer from Mn (II) to Mn (IV) to achieve high specific capacitance and energy density via multiple charge transfer dynamics. And the 3D micro-meso-macro porous structure has provided the electrolyte sufficient active sites and smooth ion migration channels. Atomic-scale information has been provided by classical molecular dynamics. In polarized states, the non-polar water molecular layer is at a higher energy level, and the electrostatic adsorption force between carbon atom and K ion is higher than the hydrophobic force of carbon. The loading MnO2 has disturbed the density distribution in the local region, changed the ordered structure, and made the loading sites form defects. Green, affordable and renewable biomass has been used as the precursor achieving the high energy density of the carbon-based electrode.