The developments in mobile/portable electronics and alternative energy vehicles prompted engineers and researchers to develop electrochemical energy storage devices called supercapacitors, as the third-generation type capacitors. Most of the research and development on supercapacitors focus on electrode materials, electrolytes, and hybridization. Some attempts have been directed towards increasing the energy density by employing electroactive materials, such as metal oxides and conducting polymers. However, the high cost and toxicity of applicable metal oxides and poor long-term stability of the conducting polymers paved the way for alternative electrode materials. The electroactive materials with carbon particles in composites have been used substantially to improve the stability of supercapacitors. Furthermore, the use of carbon particles and metal oxides could significantly increase the energy density of supercapacitor electrodes compared to metal oxides. Recent developments in carbon materials, such as carbon nanotubes (CNTs), activated carbon, reduced graphene oxide, and graphene, have found applications in supercapacitors because of their enhanced double-layer capacitance due to the large surface area, electrochemical stability, and excellent mechanical and thermal properties.