Pseudocapacitive Charge Storage in Single-Step-Synthesized CoO-MnO2MnCo2O4 Hybrid Nanowires in Aqueous Alkaline Electrolytes

A new pseudocapacitive combination, viz. CoO-MnO2-MnCo2O4 hybrid nanowires (HNWs), is synthesized using a facile single-step hydrothermal process, and its properties are benchmarked with corrventional battery-type flower-shaped MnCo2O4 obtained by similar processing. The HNWs showed high electrical conductivity and specific capacitance (C-s) (1650 F or 184 mA h g(-1) at A g(-1) with high capacity retention, whereas MnCo2O4 nanoflower electrode showed only one-third conductivity and one-half of its capacitance (872 F g(-1) or 96 mA h g(-1) at 1 A g(-1)) when used as a supercapacitor electrode in 6 M KOH electrolyte. The structure-property relationship of the materials is deeply investigated and reported herein. Using the HNWs as a pseudocapacitive electrode and commercial activated carbon as a supercapacitive electrode we achieved battery-like specific energy (E-s) and supercapacitor-like specific power (P-s) in aqueous alkaline asymmetric supercapacitors (ASCs). The HNWs ASCs have shown high E-s (90 Wh kg(-1) (volumetric energy density E-v approximate to 0.52 Wh cm(-3)) with P-s up to similar to 10(4) W kg(-1) (volumetric power density P-v approximate to 5 W cm(-3)) in 6 M KOH electrolyte, allowing the device to store an order of magnitude more energy than conventional supercapacitors.