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Title: On the Source of Conductivity in Alkaline Zn Anodes: Zn Percolation and ZnO Bridging
Alkaline Zn anodes are fundamental to commercial Zn-MnO2batteries as well as emerging rechargeable designs. In these electrodes, Zn particles are both the active material and source of electronic conduction. However, there are known cases in which electronic connectivity between Zn particles or the current collecting pin is lost even though the battery continues to function. Here we use X-ray computed tomography (CT) of AA batteries to demonstrate several examples of Zn particle-to-particle connectivity breakdown, which is observed even in cases at relatively high discharge rate. This indicates maintenance of the electronic network through the less-conductive ZnO discharge product. We introduce a new equation for electronic conductivity maintained through bridges of ZnO formed between percolating Zn particles. This necessitates discarding the Bruggeman correlation and instead redefining effective electronic conductivity using percolation theory. We demonstrate that such a model for conduction enables prediction of an inverted reaction zone, which is an experimentally observed case in which significant Zn dissolution and ZnO formation occurs heavily near the current collecting pin. Current computational Zn-MnO2models never predict an inverted reaction zone, and thus the updated conductivity enables models to accurately explain a wider range of experimental conditions.  more » « less
Award ID(s):
2044602
PAR ID:
10685930
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
IOP
Date Published:
Journal Name:
Journal of The Electrochemical Society
Volume:
172
Issue:
3
ISSN:
0013-4651
Page Range / eLocation ID:
030515
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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