Layered Vanadium Phosphates as Electrodes for Electrochemical Capacitors Part II: The Case of VOPO 4 •CTAB and K 0.5 VOPO 4 •1.5H 2 O

Abstract

In the present work two layered vanadium phosphates were prepared, VOPO 4 • CTAB and K 0.5 VOPO 4 • 1.5H 2 O 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 VOPO 4 • 2H 2 O, with water molecules in the interlayer space. In the case of VOPO 4 • 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 K 0.5 VOPO 4 • 1.5H 2 O, 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.