Abstract: The biggest advantage of supercapacitor lies in not only the excellent pulse and fast charging-discharging performance, but also the characteristics of long cycle life and wide operating temperature window with no pollution. However, the energy density of supercapacitor is low. In this paper, the working principle, the development status, defects and improvement method of supercapacitors are introduced. Based on the research workes of the supercapacitors with high energy density in our group, combined with the literature reports in recent years, the strategies to promote the energy density of supercarpacitors will be focused. The strategies for the enhancement of energy density include: 1) to increase the specific capacitance of the electrode by reducing the existing materials to nano sizes or to develop new materials with high capacity; 2) to increase the voltage window of the supercapacitor by developing ionic liquid electrolyte with high voltage window or to adopt asymmetric supercapacitors in which one electrode is pseudocapacitive, while the other utilizes double layer capacitance; 3) to build lithium ion hybrid supercapacitors with both high energy density and high power density by “internal cross” the supercapacitor and lithium ion battery. Finally, the prospects in the future development of supercapacitors will be provided.

Key words: supercapacitor, asymmetric supercapacitor, lithium-ion hybrid supercapacitor, energy density, power density