A Hybrid Electrochemical Supercapacitor Based on a 5 V Li-Ion Battery Cathode and Active Carbon

LiNi 0.5 Mn 1.5 O 4 is the most promising 5 V cathode material for Li-ion batteries because of its high voltage and good cycling behavior. We introduced LiNi 0.5 Mn 1.5 O 4 as a positive electrode for a hybrid electrochemical supercapacitor with an active carbon negative electrode in 1.0 M LiPF 6 ethylene carbonate/dimethyl carbonate ( 1 : 2 in volume) solution. It has a sloping voltage profile from 2.8 to 1.5 V, delivers a capacity of 55 Wh ∕ kg based on the total active materials, and shows a good cycling profile with capacity retention of 80% over 1000 cycles.