Executive Summary : | Currently, rechargeable Li-ion batteries have dominated the portable electronic market as the power source, because of their high energy density. However, the non-aqueous electrolytes used in Li-ion batteries are flammable, which cause safety issues. On the other hand, aqueous rechargeable metal batteries are of low cost, non-toxic, environmentally friendly and safer as compared to non-aqueous batteries. However, aqueous batteries possess low energy density due to the limited potential window (about 2.0 V). These aqueous batteries with lower energy density can find applications in large scale energy (grid) storage, where energy density is not that important. Here in this proposal, we would like to develop a prototype of novel aqueous rechargeable Mn||MO2 battery, consisting of Mn metal as anode and MO2 (M is transition metal) as cathode and aqueous electrolyte of Mn salt. Mn metal is abundant (1100 ppm in earth crust), non-toxic, having low reduction potential (-1.19 V vs. SHE) and high theoretical specific capacity (976 mAh g-1). Aqueous Mn-ion batteries using metal oxide cathodes have many advantages such as high theoretical capacity (about 300 mAh. g-1), low cost and environmental friendliness, with its capability to reach up to 2.0 V by using MnSO4/Mn(CF3SO3)2 electrolyte (as reported in one of few studies). This battery is based on the intercalation/deintercalation of Mn2+ ions into/from the cathode during discharge/charge process of the electrode. In the point of view of Mn reserve, India ranked second, which means if commercialized, India would be self-sustainable on raw materials as well as poise itself as an energy exporter. Various metal oxides such as MnO2 (various crystallographic forms), NaxMnO2, Na2Mn3O7 etc. will be investigated as the cathode material for Mn-ion batteries. Our research will focus on synthesis, structural analysis, and electrochemical performance of various oxide cathodes in Mn-ion batteries. In order to understand the charge storage mechanism, the metal oxide electrodes will be analyzed by ex-situ XRD, Raman and XPS upon charge-discharge. The diffusion kinetics of Mn2+ ions into/from the cathode will be evaluated by galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectra (EIS). Finally, we would like to reach a high specific capacity (around 200 mAh g-1) laboratory prototype of Mn-ion battery. |