Influence of CNTs/Graphene Oxide Hybridization and Mn Doping on the Electrochemical Behavior of Ni-Co Hydroxides

Abstract Nickel–cobalt layered double hydroxide (NiCo–LDH) is a promising supercapacitor electrode material owing to its high theoretical specific capacitance and remarkable electrochemical activity. However, its intrinsically low electrical conductivity and limited structural stability can lead to performance degradation in practical applications, particularly during repeated charge–discharge cycles, when partial collapse of the layered structure may occur, compromising stability and energy storage capability at high current densities. To address these challenges, this study integrates conductive substrates, carbon nanotubes (CNTs) and graphene oxide (GO), with compositional modulation via manganese (Mn) incorporation to examine the resulting structural and electrochemical effects. NiCo–LDH, NiCoMn–LDH, and NiCo/CNTs–GO composites were synthesized through precipitation and hydrothermal methods. The incorporation of CNTs–GO facilitated the formation of uniform microspheres through urea-assisted complexation, yielding a three-dimensional conductive network with a high specific surface area of 161 m²·g⁻¹. Electrochemical measurements showed that NiCo/CNTs–GO achieved a specific capacity of 2034 C·g⁻¹ at 1 A·g⁻¹, retained 84.1% at 5 A·g⁻¹, and maintained 74.6% after 5000 cycles. These findings provide a comparative basis for understanding the roles of conductive network integration and Mn incorporation in layered hydroxide electrodes, and offer design principles for the development of advanced energy storage materials.