Improving Energy Density of Supercapacitors to Increase Hold-Up Time for Frequency Regulation in Power Grids

Supercapacitors are attracting attention as candidates for replacing lithium-ion batteries (LiB) because of their high durability and power density. However, the energy density is only 10% of LiB, making it difficult to apply large-capacity ESS. In this study, graphene composites were pre-doped with different ratio of lithium oxide to improve the energy density of electrodes. A 30F cylindrical cell was fabricated based on the high energy density electrode materials, which was operated stably at 10C (85.6%) and 150C (71.8%). Furthermore, it showed 84.8% of specific capacitance even after 200,000 charge/discharge cycles at 100C-rate, expecting to be able to respond to ultra-short time in the frequency regulation of the power system.