Ag nanodots-induced interfacial fast electronic/ionic diffusion kinetics of carbon capsule supported CoMn2O4 for high-voltage supercapacitors

The low energy density of SCs (<10 Wh kg−1) severely limits their commercial application, increasing either specific capacitance or broadening the potential window of the device is the effective pathway to improve the device energy density. Herein, nitrogen-doped carbon capsule (NC) supported Ag nanodots-decorated CoMn2O4 nanoflower (NC/CoMn2O4/Ag) electrode material has been successfully designed and synthesized. NC/CoMn2O4/Ag exhibits superior discharge capacity of 1806.4C/g, superior to NC/CoMn2O4 electrode (without Ag nanodots, 1319.2C/g at 1 A g−1). Theoretical calculations analysis demonstrates that decorated Ag nanodots on CoMn2O4 plays a fundamental role in improving the band gap, electrical conductivity, diffusion and transfer of electrolyte ions. In addition, asymmetric gel electrolytes of PVA-Na2SO4//PVA-KOH were designed for the assembly of asymmetric devices. This device delivers gravimetric energy density up to 89.9 Wh kg−1 at 894 W kg−1. The device can reach a large electrochemical voltage of up to 2.3 V, which could drive a remote-controlled toy easily. This work showcases a promising approach to rationally design conductive nanodots-decorated transition metal oxide-based materials towards high energy density supercapacitors. And it also sheds light on an in-depth understanding of their charge storage mechanisms.