Hydrothermal design of CoMoO4@CoWO4 core-shell heterostructure for flexible all-solid-state asymmetric supercapacitors

Abstract

As electrode material, cobalt-molybdenum oxide (CoMoO4) attracts more attention for energy storage device through its various oxidation states and good electrochemical properties. However, its low conductivity and energy density still hinder its applicability. To integrate its practicability as advanced electrode material in supercapacitor, we chose CoWO4 as conductive shell material to boost the conductivity on the core surface. Herein, a kind of novel CoMoO4@CoWO4 nanorods core-shell heterostructure is designed with two-step hydrothermal strategy. The CoMoO4 nanorods fully covered by CoWO4 nanoparticles provides ultrahigh specific surface area of 331.1 m2·g−1. Benefiting from synergistic effect, CoMoO4@CoWO4 electrode results superb specific capacitance of 2070 F·g−1 at 0.5 A·g−1 and marvelous stability behavior of 92% after 10,000 cycles. The charge storage mechanism is dominated by the capacitive contribution. Meaningfully, at 0.5 Aˑg−1, all-solid-state asymmetric CoMoO4@CoWO4//activate carbon supercapcitor device delivers ultrahigh specific energy of 71.8 Wh·kg−1 at 354 W·kg−1 specific power. Interestingly, two asymmetric devices can illuminate red and green LEDs.