Electrochemical performance of a hybrid lithium-ion capacitor with a graphite anode preloaded from lithium bis(trifluoromethane)sulfonimide-based electrolyte

A hybrid LiC capacitor combining a lithium-ion battery type (graphite) electrode and an electrical double-layer (activated carbon) one has been developed by preloading graphite from 2 mol L−1 lithium bis(trifluoromethane)sulfonimide (LiTFSI) organic electrolyte. The graphite intercalation compound was formed by applying ca. 10 successive charge/self-discharge pulses. The optimized hybrid device operates in the voltage range from 1.5 to 4.2 V and displays 60% higher gravimetric capacitance than an electric double-layer (EDL) capacitor using the same activated carbon for both electrodes. As a result, the energy density reaches 80 Wh kg−1, which is four times higher than the value for the EDL capacitor with the same total mass of carbon.