Facile synthesis of reduced graphene oxide nanosheet modified NiMn-LDH nanoflake arrays as a novel electrode for asymmetric supercapacitor

Abstract

Composite electrodes that possess both appropriate integration and reasonable structures are needed to provide eminent electrochemical performance in energy storage devices. At this work, an innovative electrode material with a composite structure of NiMn-LDH nanosheets fixed on the reduced graphene oxide/Ni Foam (rGO/NF) was fabricated by a convenient two-step hydrothermal process. Designing the heterostructure with the hydrothermal reaction to grow LDH layers has engineered NiMn LDH/rGO, a highly active towards the electrochemical performance. The formation of hybrid structure is characterized using X-ray diffraction, and scanning electron microscopy, which confirmed as well as showed the uniform growth of NiMn-LDH nanoflakes on rGO sheets. The intriguing compositional/componential advantages significantly facilitate the efficient penetration of the electrolytes and increase active sites of redox reactions in energy storage application. The NiMn LDH/rGO composite exhibited the highest specific capacitty of 1090 Cg⁻¹ at 1 Ag⁻¹ with an excellent cyclic stability of 92.2 % over 10,000 charging and discharging cycles at 20 Ag⁻¹. An asymmetric supercapacitor (ASC) with NiMn LDH/rGO//activated carbon (AC) demonstrates a remarkable capacity of 330.5 Cg⁻¹ at 1 Ag⁻¹ with excellent cycling stability. Moreover, the device achieving a high energy density of 45.8 Whkg⁻¹ at 623 Wkg⁻¹ and favourable cycle life, where 98.3 % of the capacitance was retained after 10,000 cycles. The coupling and synergistic effects of NiMn LDH and rGO provide a convenient channel for the electrochemical process, which is beneficial to spread widely within the realm of electrochemical energy storage.