A high performance hybrid capacitor with Li2CoPO4F cathode and activated carbon anode

Abstract

For the first time, we report the possibility of utilizing Li2CoPO4F as a novel cathode material for hybrid capacitor applications. Li2CoPO4F powders were prepared by a conventional two-step solid state method. A hybrid cell was fabricated using Li2CoPO4F as the cathode along with activated carbon (AC) as the anode in 1 M LiPF6 dissolved in 1:1 EC/DMC electrolyte and its electrochemical properties were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and constant current charge–discharge (C–D) techniques. The Li2CoPO4F/AC cell is capable of delivering a discharge capacitance of 42 F g−1 at 150 mA g−1 current density within 0–3 V region having excellent coulombic efficiency of over 99% even after 1000 cycles. Furthermore, the Li2CoPO4F/AC cell exhibited excellent rate performance with an energy density of ~24 W h kg−1 at 1100 mA g−1 current and maintained about 92% of its initial value even after 30000 C–D cycles. Electrochemical impedance spectroscopy was conducted to corroborate the results that were obtained and described.