Application of Porous Carbon Material As Electrode Material of Polyvalent Cation Electric Double Layer Capacitor (EDLC) for High Capacity

An electric double layer capacitor (EDLC) is charged and discharged by the physical adsorption and desorption of electrolyte ions on the electrode surface. EDLC has the advantage that it can be charged and discharged at high speed and has a long life. EDLC is used in memory backup power supplies for personal computers and energy recovery systems for power regenerative brakes in hybrid vehicles and other applications. Therefore, higher energy density is required. E = 1/2 CV2 ... (1) Therefore, the energy density increases by increasing the electrostatic capacity and the potential. In the conventional adsorption and desorption of monovalent cations, only one electron can be transferred per cation. Therefore, by adsorption / desorption of divalent cations, two electrons can be exchanged for each cation. Therefore, it was considered that the capacitance can be increased by using an electrolyte solution of divalent cations. In this study, Li + was used as the monovalent cation and Ca2 + was used as the divalent cation. As the anion, Li +, Ca2 + and ClO4 - and BF4 -, which have a stable anion structure, were used. An organic electrolyte with a wide potential window was used. Propylene carbonate (PC) and γ-butyrolactone (GBL), which are commonly used in EDLC research as a solvent for organic electrolytes, can dissolve the electrolyte used. Was used. As a result, the capacitance increased when Ca2 + was used as the cation. This is thought to be due to the increase in electron transfer due to the use of the divalent cation. In addition, when GBL is used as the solvent, the electrostatic capacity is further increased. The capacity was increased. We considered that there was a difference in the solvation structure, and evaluated the solvation structure using Raman spectroscopy. As a result, when GBL was used, the coordination number of the solvent molecule decreased and solvation It was thought that the size of the electrode became smaller, the amount of adsorption to the electrode increased, and the capacitance increased.