Enhanced electrochemical performance of lamellar structured Co–Ni(OH)2/reduced graphene oxide (rGO) via hydrothermal synthesis

Abstract

Lamellar Co–Ni(OH)₂/rGO structures were prepared by co-precipitation followed by hydrothermal synthesis. Lamellar and crystalline Co–Ni(OH)₂/rGO delivered better specific capacitance (C_s) and rate capability than low-crystallinity composites due to improved ionic and electronic conductivity. A high value of the C_s was achieved with Co–Ni(OH)₂/rGO prepared at 150 °C for 12 h with a graphite oxide (GO)-to-metal precursor ratio of 1 : 5. This condition gave a C_s of 617 F g⁻¹ at 2 mV s⁻¹ and 811 F g⁻¹ at 0.5 A g⁻¹ with the highest capacitance retention of 90% at 2 A g⁻¹ and good cycling stability (∼77% at 70 mV s⁻¹) at 5000 cycles. Furthermore, high mass loading, ∼4.5–5.5 mg cm⁻², was used in the fabrication of the electrodes, which is higher than that of most previous reports.