This thesis examines electrode materials such as mesoporous carbons, manganese oxides, iron oxides and their nanohybrids with graphene. It also explores several of the key scientific issues that act as the governing principles for future development of supercapacitors, which are a promising class of high-efficiency energy storage devices for tackling a key aspect of the energy crisis. However, critical technical issues, such as the low energy density and reliability, need to be addressed b...