Synthesis, characterization, and effect of electrolyte concentration on the electrochemical performance of Li2Cu(WO4)2 as a high-performance positive electrode for hybrid supercapacitors

Abstract

In the present work, a polycationic dilithium copper bis(tungstate) oxide was prepared. The electrochemical performances of the synthesized material were evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD), and cyclic stability studies. First, the electrochemical performance of the Li2Cu(WO4)2 electrode was studied in lithium hydroxide electrolyte with different concentrations 1, 2, 3, 4, and 5 M. A mechanism of electrochemical OH-ions intercalation in different concentrations of LiOH into the Li2Cu(WO4)2 electrode material was studied. This study showed that the Li2Cu(WO4)2 electrode has a specific capacity that varies with the concentration of the electrolyte. The 4 M LiOH electrolyte showed a maximum capacity value of 505C/g at a current density of 5 A/g, indicating that the electrolyte concentration effects on the electrochemical performance of the electrode. The results showed that the Li2Cu(WO4)2 electrode had a specific capacity of 722C/g at 1 A/g in the 4 M LiOH electrolyte. The electrode shows excellent retention of 80.7 % of its initial specific capacity after 10,000 galvanostatic charge-discharge cycles at 20 A/g. In addition, the hybrid supercapacitor device is further fabricated with activated carbon as cathode materials and a Li2Cu(WO4)2 electrode as the anode and improved a high energy density of 69.6 Wh/kg at a power density of 900 W/kg as well as an excellent retention capacity (84.8 %) after 10,000 cycles at 10 A/g.