Tuning the electronic structure of NiMoO4 by coupling with SnO2 for high-performance hybrid supercapacitors

Abstract

Nickel molybdate (NiMoO4) has been regarded as a promising battery-type electrode material for hybrid supercapacitors (HSCs) because of its low cost, high theoretical capacity and richer redox reactions. However, its large-scale application is limited by the poor rate performance and low stability. In this work, we suggest that the electronic structure tuning can effectively improve the capacity but also enhance the stability. Such tuning can be readily realized by coupling NiMoO4 with SnO2. The introduction of SnO2 promotes the electron transfer from NiMoO4 to SnO2 and therefore reduces the electron density of NiMoO4, which leads to an enhanced adsorption of OH− ions and thus boosts the capacity. As a result, the SnO2@NiMoO4/CP core-shell electrode exhibits a high capacity of 0.65 mA h cm−2 (257.8 mAh g−1) at a current density of 5 mA cm−2 (2 mA g−1) along with greatly enhanced stability. Besides, the assembled HSC device using SnO2@NiMoO4/CP as cathode and active carbon/CP as anode shows a superior specific capacity of 109.5 mAh g−1 at 5 mA cm−2 and excellent cycling performance with a capacity retention of 92.2% at 50 mA cm−2, as well as a high specific energy of 78.4 Wh kg−1 at a power density of 895 W kg−1, outperforming many other reported hybrid supercapacitors.