Hydrothermal synthesis of rGO-decorated NiMn2O4 nanoneedles for high-performance positive electrode in asymmetric supercapacitors

Pseudocapacitive electrode materials inherently have low electron conductivity, which prevents an energetic material from being fully utilised. We were able to produce effective hierarchical NiMn₂O₄/rGO composites, which provide an appealing solution to this issue. The composites were synthesised using a one-step hydrothermal approach. Due to the high electrical conductivity of reduced graphene oxide (rGO), the needles on plate like morphology of NiMn₂O₄, and the strong hold of dynamic materials to the current collector, the resulting hybrid electrodes exhibit a specific capacitance of 1628 Fg⁻¹ at a current density of 1 Ag⁻¹. They also demonstrate excellent rate performance and remarkable cycling stability, with a capacitance retention of 97.4 % after 10,000 cycles. In addition, the NiMn₂O₄/rGO//AC asymmetric supercapacitor (ASC) exhibits a peak energy density of 45Whkg⁻¹ when operated at a power density of 3240 Wkg⁻¹. The ASC device has an impressive ultralong cycling life, with a capacitance retention rate of 89.1 % after undergoing 10,000 charge/discharge cycles. The NiMn₂O₄/rGO composites provide a scalable production method and demonstrate outstanding electrochemical performance. This presents an opportunity to create innovative hybrid electrodes for enhanced supercapacitors.