Assembling 2D ultrathin nanosheets into vertical heterostructures offers significant potential for advanced energy storage due to enhanced active sites, improved ion diffusion, and increased electrical conductivity, leading to superior ion/electron transport, higher energy density, and improved rate performance. In case of transition-metal hydroxides, to overcome with challenges such as random assembly, complex synthesis, instability, and poor interfacial contact is critical. This study synthesizes large area, ultrathin, 2D Nickel/Cobalt hydroxide vertical heterostructures (nickel as the top layer) using a wet chemical process, achieving 32% higher areal charge storage compared to cobalt/nickel hydroxide vertical heterostructures, 57% higher than Ni(OH)2 and 330% higher than individual Co(OH)2. The synergistic interaction between nickel and cobalt hydroxides contributes to a high volumetric capacity (710 mAh cm−3) and energy density (285 mAh cm−3) in symmetric devices. The flexible microsupercapacitor retains 75% capacitance after 15,000 cycles and demonstrates stability under bending up to 135°, with a volumetric capacity of 393 mAh cm−3. Density functional theory simulations complement experiments, revealing interaction energy and electronic state redistribution near the Fermi level. This integrated approach serves as a guide for enhancing electrochemical properties in 2D heterostructures, aiding in the development of next-generation, high-performance energy storage materials.