Investigations on electrical and electrochemical properties of Ag⁺ion conducting quaternary solid electrolyte systems: x[0.75 AgI : 0.25 AgCl] : (1−x)RbI

Abstract

Investigations on ion transport behaviour of new Ag+ ion conducting quaternary solid electrolyte systems: x[0.75AgI : 0.25AgCl] : (1 − x)RbI, where 0.1 ≤ x ≤ 1 mol.wt fractions, are reported. The solid electrolyte systems were synthesized adopting different routes of solid solution reactions. An alternative host salt, ‘a quenched [0.75AgI : 0.25AgCl] mixed system solid solution’, discovered at the present laboratory, has been used in place of AgI. The compositional dependent conductivity studies at room temperature revealed the quaternary systems 0.7[0.75AgI : 0.25AgCl] : 0.3RbI as the optimum conducting composition (OCC). AgI has been traditionally and most widely used as host salt in the past to prepare the majority of well-known fast Ag+ ion conductors including the ternary superionic solids MAg4I5 (M = Rb, K, NH4). Also, RbAg4I5 has been recognized as one of the highest conducting superionic solids with conductivity σrt ∼ 10−1 S cm−1 at room temperature. However, it has been observed that RbAg4I5 is thermodynamically unstable, particularly in the open ambient conditions, while the newly synthesized quaternary solid electrolyte, having OCC 0.7[0.75AgI : 0.25AgCl] : 0.3RbI, has been observed to be much more stable than RbAg4I5. For direct comparison of the ion conduction behaviour of the newly synthesized OCC, the ternary superionic solid RbAg4I5 (0.8AgI : 0.2RbI) has also been synthesized in an identical manner. The room temperature conductivity (σrt) of the newly synthesized quaternary OCC was slightly lower than that of RbAg4I5. However, σrt remained practically stable for a fairly long time in the open ambient conditions as compared with that of RbAg4I5. The mechanism of ion transport in OCC has been characterized on the basis of experimental studies on various ionic parameters namely conductivity (σ), ionic mobility (μ), mobile ion concentration (n), ionic drift velocity (vd), ionic transference number (tion) etc. The temperature dependent studies on these ionic parameters provided information regarding various energies involved in the respective thermally activated processes. Solid state batteries have been fabricated using OCC as electrolyte in the cell configuration Ag-metal (anode)/0.7[0.75AgI : 0.25AgCl] : 0.3RbI (solid electrolyte)/C+I2 (cathode) and the cell potential discharge characteristics have been studied under various load conditions.

Ion transport property studies on PEO–PVP blended solid polymer electrolyte membranes

“…The formation of the solid polymer electrolyte and thermal behaviour were explained on the basis of XRD and DSC results. The basic ion transport parameters, namely ionic conductivity (σ ), ionic mobility (µ), mobile ion concentration (n) and ionic transference number (t ion ), have been measured employing different experimental techniques, as reported in our earlier communications [9,10]. Solid-state polymeric batteries were fabricated in the following cell configuration: The cell performances were studied under different load conditions and the cell-potential discharge profiles were drawn as a function of time and the important cell parameters were calculated from the plateau of the profiles.…”

Ionic Drift Velocity Measurements on A Nano-composite Polymer Electrolyte: 95[90PEO: 10AgNO[sub 3]]: 5SiO[sub 2]

“…In this d.c. polarization TIC measurements on ionic/ superionic systems, including polymer electrolytes, it has been always assumed that the initial total current I T , obtained in the 'current-time' TIC plots, would be directly proportional to the applied d.c. voltage (V) i.e. the Ohm's law would be valid and hence, the effect of polarization charge build-up would be negligible during the measurements [10,15]. 'I T vs V' plot for the OCC NCPE, as shown in Fig.…”

Ion transport and electrochemical cell performance studies on hot-press-synthesized Ag+ion conducting electroactive polymeric membranes: (1 −x)PEO:x[0.7(0.75AgI : 0.25AgCl) : 0.3MI]

“…The hot-press dry casting of electroactive SPE membranes: (1 − x)PEO : x[0.7(0.75AgI : 0.25AgCl) : 0.3MI] (M ≡ Rb, K), where x = 0 < x < 50 wt(%), was done with AR grade precursor chemicals: poly(ethylene oxide) PEO (10 5 MW, Aldrich, USA), AgI, AgCl (>98%, Reidel, India), RbI (>99%, Aldrich), KI (>99%, Merck). Firstly, the quaternary superionic solids: 0.7(0.75AgI : 0.25AgCl) : 0.3RbI and 0.7(0.75AgI : 0.25AgCl) : 0.3KI, were prepared by solid solution reactions, as reported in our earlier communication [13,14]. For hot-press casting of SPE films, dry powders of these quaternary superionic solids, as complexing salts and poly(ethylene oxide) PEO, as polymeric host, in different wt(%) ratios were ground thoroughly at room temperature for about ∼1 h in an agate pestle and mortar.…”

“…The solution cast procedure could not be used here due to the non-availability of a common solvent dissolving both the salt and the PEO host. It is worth mentioning here that the salts: 0.7(0.75AgI : 0.25AgCl) : 0.3 MI, chosen for the complexation into the poly(ethylene oxide) PEO host, have recently been investigated at the present laboratory as Ag + ion conducting quaternary superionic systems in the polycrystalline phase exhibiting conductivity σ ∼ 10 −3 S cm −1 at 27 • C [13,14]. It has been observed that the newly investigated quaternary solid electrolyte systems exhibited much superior conductivity behaviour than the well-known ternary superionic solids: RbAg 4 I 5 and KAg 4 I 5 .…”