Charge storage mechanism of MnO<inf>2</inf> cathodes in Zn/MnO<inf>2</inf> batteries using ionic liquid-based gel polymer electrolytes

© 2015 Elsevier B.V.All rights reserved. Cathode reactions in Zn/MnO<inf>2</inf> batteries using aqueous electrolytes have been usually interpreted by the reduction of Mn^{4 +} to Mn^{3 +} while protons and/or cations penetrate inside the cathode. However, until now, the MnO<inf>2</inf> storage charge mechanism using a non-aqueous gel polymer electrolyte (GPE) has not been investigated. In this work, ionic liquid-based GPEs including BMIM Tf and ZnTf<inf>2</inf> have been employed in Zn/MnO<inf>2</inf> batteries. Different states of charge of MnO<inf>2</inf> cathodes used in Zn/IL-GPE/MnO<inf>2</inf> batteries have been analyzed by XPS and EDX techniques. XPS analysis showed that Mn^{4 +} is reduced during the discharge process at the same time as Zn^{2 +} cations are incorporated into the cathode. Besides, Zn^{2 +} cations insertion is accompanied by triflate anions.