Electrochemical Characteristics of Zn-Ion Hybrid Supercapacitors Based on Aqueous Solution of Different Electrolytes

Abstract

Electrochemical behaviour of Zn cation based various aqueous electrolytes (ZnSO4, Zn(BF4)2, zinc di[bis(trifluoromethylsulfonyl)imide], Zn(TFSI)2, and zinc trifluoromethanesulfonate, Zn(OTf)2) has been studied in thin Zn foil∣ carbon cloth hybrid supercapacitor cell and compared with Zn(ClO4)2 aqueous electrolyte electrochemical characteristics using cyclic voltammetry, constant current charge/discharge and electrochemical impedance methods. The Ragone plots have been calculated from constant power measurements data. At moderate specific power values (10 kW kg−1) noticeable decrease of specific energies can be seen in the order of electrolytes: Zn(ClO4)2 ≥ Zn(BF4)2 > Zn(OTf)2 > Zn(TFSI)2 > ZnSO4. The stability of Zn-ion hybrid supercapacitor cells under study has been tested using the long lasting (up to 10000 cycles) constant current charge/discharge method and is very good for Zn(OTf)2, Zn(ClO4)2 and ZnSO4.