The effect of composition and microstructure of NiO on the electrochemical properties of NiO/reduced graphene oxide-based supercapacitor electrodes prepared by solvothermal methods were investigated systematically. The findings reveal that the influences of reduced graphene oxide (RGO) coating on electrode systems are essentially 2-fold. One is to increase the electrical conductivity of the electrodes, especially when the electrodes are not very conductive. However, this influence is not that obvious when the electrodes are already highly conductive to begin with. The second influence is to improve the mechanical stability of the electrode, thus increasing the cyclability of the electrodes. Moreover, adding glucose during the electrode synthesis reduces the particle size as well as the thickness of deposited active material (NiO) on the substrate under similar mass loading. These thinner but denser NiO structures exhibited much improved electrochemical performance. These understandings will be important in the designing of high performance energy storage devices, especially from materials with limited electrical conductivity.