Layered Vanadium Phosphates as Electrodes for Electrochemical Capacitors Part II: The Case of VOPO4•CTAB and K0.5VOPO4•1.5H2O

Abstract

In the present work two layered vanadium phosphates were prepared, VOPO4 • CTAB and K0.5VOPO4 • 1.5H2O as electrode materials for electrochemical capacitors. These materials contain different molecular species in their interlayer space leading to an electrochemical behavior that drastically differs from the crystalline phase VOPO4 • 2H2O, with water molecules in the interlayer space. In the case of VOPO4 • CTAB, it was found that CTAB molecules block the pathway of electrolyte ions into the crystalline structure avoiding an intercalation/deintercalation process. In the case of K0.5VOPO4• 1.5H2O, the K+ ions from the crystalline structure hinder the intercalation/deintercalation process leading around 73 and 71 percent of the charge arise from a capacitive process in 3 M LiOH and 3 M KOH, respectively.