Influence of Relative Humidity on the Reaction Kinetics in Rubidium Silver Iodide Based All-Solid-State Battery

Our previous study on a rechargeable rubidium silver iodide (RbAg4I5) based all-solid-state battery has shown an exponentially improved performance with increasing relative humidity (RH). Previous galvanostatic charge-discharge measurements revealed that while operating in an ambient environment with a relative humidity (RH) of 100%, the specific energy and energy density of the all-solid-state battery reached 68 Wh kg-1 and 400 Wh L-1, respectively; however, the specific energy decreased by 90% under 10% RH. Here, we investigated the effect of humidity on the electrochemical reaction kinetics in the RbAg4I5 based all-solid-state battery. Four-electrode conductivity measurements of the solid electrolyte unveiled that the humidity had no appreciable influence (~4%) on the conductivity, whilst series cell resistances of half cells evaluated from electrochemical impedance spectroscopy measurements change only 3% within an RH ranging from 35% to 100%. On the other hand, linear sweep voltammetry measurements of anode and cathode half cells showed that increasing the RH from 35% to 100% increased the exchange current density by three orders of magnitude. The relationship between the water vapor adsorption and reaction kinetics was examined by constructing water vapor adsorption isotherms. The trend of exchange current density was attributed mainly to the water adsorption/desorption at the electrode/electrolyte interfaces and a model was proposed to explain the impact of water adsorption on the electrochemical kinetics. These results suggest that the all-solid-state battery operates effectively when exposed to a high humidity environment and can be used in the applications requiring very high reliability. Figure 1