Modeling of alkaline batteries and investigation of the relationship between electrochemical impedance and Raman spectroscopy

This work presents an in-depth investigation of the electrochemical behavior of alkaline manganese dioxide batteries, focusing on the correlation between electrical and chemical characterizations through galvanostatic electrochemical impedance spectroscopy and Raman spectroscopy. A physics-based equivalent electric circuit model is proposed to capture the battery's impedance response at different state of charge (SOC) levels, accounting for ohmic resistance, charge-transfer processes, and diffusion phenomena. The evolution of the model parameters throughout the discharge process highlights critical transitions in internal battery dynamics, including the formation of zinc oxide layers and the increase in interfacial resistances. Concurrently, Raman spectroscopy measurements performed on the cathode surface at various SOC levels reveal significant structural and compositional changes, most notably the gradual transformation of manganese dioxide (MnO2) into manganese(III) oxide (Mn2O3) and mixed zinc-manganese oxides with a spinel structure (ZnMn2O4) resulting from zinc migration through the separator. Finally, this work provides new insights into degradation mechanisms by establishing a direct correlation between electrical parameters and chemical transformations.