Design of nickel cobalt molybdate regulated by boronizing for high-performance supercapacitor applications

Abstract

Nickel–cobalt-based molybdates have been intensively investigated because of their high theoretical specific capacitance and multifarious oxidation states. Here, we have successfully synthesized hierarchical structures (Ni₃B/Ni(BO₂)₂@Ni_xCo_yMoO₄) by boronizing Ni_xCo_yMoO₄ nanosheets on flexible carbon cloth substrates. Benefitting from the synergistic effect among Ni₃B, Ni(BO₂)₂ and Ni_xCo_yMoO₄ in hybrid architectures, the electrode material possesses higher capacity of 394.7 mA h g⁻¹ at 1 A g⁻¹ and a good rate performance (309.5 mA h g⁻¹ maintained at 20 A g⁻¹). Then, a hybrid supercapacitor assembled with Ni₃B/Ni(BO₂)₂@Ni_xCo_yMoO₄ and activated carbon as the positive and the negative electrode, displays a high specific capacitance of 370.7 F g⁻¹ at 1 A g⁻¹ (210 F g⁻¹ at 10 A g⁻¹), a high voltage of 1.7 V, and a high energy density of 131.8 W h kg⁻¹ at the power density of 800 W kg⁻¹ (still 74.7 W h kg⁻¹ maintained at 8000 W kg⁻¹). This study widens the research scope of boronizing pseudocapacitance materials and reveals a high application potential of Ni₃B/Ni(BO₂)₂@Ni_xCo_yMoO₄ for energy storage devices in the future.