Solid State Proton Conducting Secondary Battery at Room Temperature K. Singh, S. S. Bhoga, S. M. Bansod and R. U. Tiwari 1 Department of Physics, Nagpur University, Nagpur-440 033 (India) 1 Department of Applied Physics, R.K.N.E.C, Katol Road, Nagpur-440 013 (India) E-mail:msrl1@hotmail.com Abstract: Using P2O5, SiO2 and Al2O3, a proton conducting electrolyte, zinc anode and with three different cathodes MnO2, PbO2 and V2O5 few electrochemical cells were fabricated. The open circuit voltage (OCV) and short circuit current (SCC) of the cells found to be 1.82, 2.23 and 1.91 V and 3, 2.1 and 0.8 mA, respectively. The performance of MnO2 cathode is better over other two materials viz. PbO2 and V2O5. The materials used in the cells are environment friendly and no special atmospheric conditions are required for cell fabrication as in case of lithium cells. Keywords: Room temperature proton conductors, Solid-state battery, Cathode. PACS: 66.30, 61.7, 82.45 1. Introduction Proton ion conductors have attracted a great deal of attention in recent past due to their practical applications in solid state electrochemical power sources, sensors, electrochromic displays and fuel cells [1-3]. Since last decade a lot of efforts have been directed towards the development of all solid state batteries because of the following potential advantages: 1. Absence of electrolyte leakage from sealed battery. 2. Absence of problem related with the vaporization of liquid. 3. Easy of miniaturization and choice of multiple shape factors. A major disadvantage with all solid-state batteries has been their high internal impedance associated with the poor ionic conductivity of solid electrolyte [4]. In this direction, a considerable attention, in more recent past, has been focus on the development of Ag + and Li + conductors. In comparison, a moderate effort has been made to develop proton conductors from all solid-state battery point of view. Protonic conduction in liquid electrolytes has been common but is relatively rare in solids. There has been currently much interest world wide in proton conducting solids, both from the scientific aspect, as materials with novel properties, but also for their possible applications in high-energy-density solid-state batteries. Proton conductors have been very attractive due to low weight of hydrogen and high Gibb's energy of formation of hydrogen compounds. In an ideal solid-state battery, involving protonic reaction, the solid electrolyte has to have high proton conduction and transport number  unity. All above factors have prompted to undertake the present work. 2. Experimental The initial ingredient phosphorous pentoxide (P 2 O 5 ) and silicon dioxide (SiO 2 ) with Aluminate (Al 2 O 3 ), obtained from E-Merk, India, were used. Different compositions of solid electrolyte P 2 O 5 : SiO 2 : Al 2 O 3 were prepared by mixing them together. On the basis of thermodynamic stability and better conductivity the optimized composition of the electrolyte with zinc as anode and MnO 2 , PbO 2 and V 2 O 5 as cathode materials, three electrochemical cell were fabricated. The cells were discharged obtained under constant load and constant current drain conditions. The readings were recorded at the interval of two hours till the load voltage falls to 60% of its initial value using in house experimental setup. The complex impedance data of the electrochemical cells before, during and after the discharge was measured over the frequency range 10Hz – 13MHz with the help of computer controller HP-4192A LF impedance analyzer. The open circuit voltage (OCV) and short–circuit current (SCC) and other parameters of cells I-III were also determined. 3. Results and Discussion Figure 1 shows the discharge characteristics at constant current drain. The constant current drain 20,10, and 10 A are set for cell I, II and III respectively. As expected, the cell voltage initially decreases exponentially with increase in time and attains a constant value within few hours. A clear plateau is seen for each current drains. The drop in the voltage followed by a plateau indicates the discharge of cell. The discharge parameters of the cell are obtained from the discharge characteristics and presented in table-1. The cell with MnO 2 , as one of the constituents in the cathode and zinc composite anode gives