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 30 000 C–D cycles. Electrochemical impedance spectroscopy was conducted to corroborate the results that were obtained and described.