Analysis of Electrochemical Impedance Spectroscopy on Zinc-Air Batteries Using the Distribution of Relaxation Times

Robert Franke-Lang,Julia Kowal

doi:10.3390/batteries7030056

Abstract

Zinc-air batteries could be a key technology for higher energy densities of electrochemical energy storage systems. Many questions remain unanswered, however, and new methods for analyses and quantifications are needed. In this study, the distribution of relaxation times (DRT) based on ridge regression was applied to the impedance data of primary zinc-air batteries in a temperature range of 253 K and 313 K and at different State-of-Charges for the first time. Furthermore, the problem of the regularization parameter on real impedance spectroscopic measurements was addressed and a method was presented using the reconstruction of impedance data from the DRT as a quality criterion. The DRT was able to identify a so far undiscussed process and thus explain why some equivalent circuit models may fail.

Highlights

The restructuring of electrical energy production to renewable energies is accompanied by a volatile energy generation and requires energy storage in order to regulate production and demand
Lower values lead to more peaks and correspondingly to additional resistor and capacitor (RC) elements, which in principle improves the reconstruction of the measurement; the physical interpretation of the distribution of relaxation times (DRT) becomes more and more impossible
The applicability of the DRT to the process analysis of Zinc-air batteries (ZABs) was confirmed for the first time

Summary

Introduction

The restructuring of electrical energy production to renewable energies is accompanied by a volatile energy generation and requires energy storage in order to regulate production and demand. Zinc-air batteries (ZABs), for example, are comparatively cheaper, safer, and have a three times higher theoretical gravimetric capacity of about 820 Ah kg−1 based on the active material compared to an LiCoO2 LIB. The reason is mainly due to the working principle of ZABs, as two electrons are moved per mass transfer and the required oxygen is extracted from the ambient air. The interpretation of the impedance data using the universal distribution of relaxation times (DRT) approach is becoming increasingly popular [32,33,34,35,36,37,38,39], since no deeper prior knowledge of chemical-physical or electrical models is required and superimposed processes can possibly be distinguished

Methods

Results

Discussion

Conclusion