Interrogation of Alkaline AA Batteries Using in Operando Electrochemical ­Acoustic Time-of­-Flight Analysis and in Operando energy Dispersive X-Ray Diffraction

Abstract

Recently, in operando Electrochemical ­Acoustic Time-of­-Flight (EAToF) analysis has been shown to provide information about the state of charge (SoC) and state of health (SoH) of a number of battery geometries and chemistries using ultrasonic interrogation of the density and modulus shifts that occur during charge and discharge. The technique has thus far offered a general understanding of these batteries, but has not been used for in depth analysis of individual battery chemistries. In this work, we performed EAToF measurements on commercially available alkaline Zn/MnO2 AA batteries of a number of different brands under discharge and charge conditions. The data from this method were compared to in situ energy-dispersive x-ray diffraction (EDXRD) data from comparable alkaline AA batteries. Changes in the waveforms in the ultrasonic time-of-flight measurements were shown to correlate with phase transitions in the MnO2 cathode and densification and dehydration of the Zn anode, as shown by peak evolution in the EDXRD data. The mechanisms by which the phase and morphology transitions can change the transmission and reflection of an ultrasonic pulse and the utility of EAToF analysis in determining material differences between different brands of alkaline cells are discussed.