Intercalation-type electrodes of copper–cobalt oxides for high-energy-density supercapacitors

A series of Cu_xCo_3-xO₄ nanostructures (CCO) with a controllable surface morphology and oxygen vacancy density are directly grown on charge-collecting substrates via an electrochemical deposition process and subsequently used as intercalation-type electrodes for high-energy-density supercapacitors (SCs). The capacitive performance of the CCOs is strongly dependent on the rate of oxygen diffusion via intercalation in oxygen-deficient CCOs. The nanopetal electrode of Cu_0.95Co_2.05O₄ calcined at 200 °C (CCO-200) exhibits a capacitance of ~1890 F g⁻¹ at a scan rate of 10 mV s⁻¹, whereas it decreases gradually with increasing sintering temperature. A symmetric CCO-200@stainless steel SCs exhibits a capacitance and an energy density as high as ~865.50 F g⁻¹ and 108.18 W h kg⁻¹, respectively, at a current density of 1.25 A g⁻¹ with high durability for 10,000 cycles. The enhanced capacitive performance is attributed to the high electrical conductivity and high oxygen diffusion rate in CCO-200.