(Invited) Experimental and Data Analysis Platforms to Better Understand the Corrosion and Discharge of Powdered Zn

Abstract

Zinc anodes have been a cornerstone of many commercial and pre-commercial battery technologies including primary and secondary alkaline cells, Zn-air batteries and Zn-ion batteries. To maximize the performance of devices at both the lab and commercial scales, moderate surface area (mm-sized) Zn powder is used – either immobilized onto a diffusion electrode or incorporated into a slurry. Unlike nano-sized materials, micron-sized materials are poorly characterized by traditional electrochemical techniques like thin-film rotating disk electrodes, because the roughness introduced by the relatively large particles disrupts the ideal fluid flow near the surface, negating the mathematical description of the electrode behavior. This leads many researchers to try and characterize the Zn behavior in more application-like cells. The downside of doing this is that there is a strong influence of the counter electrode, electrolyte solution and the efficacy of the specific individual in assembling the cells. Therefore, there is a need to develop new platforms that have the ability to determine the electrochemical properties of powdered Zn – most notably achievable capacity and corrosion current – and to develop analytical models to describe their behavior.Over the past several years, our group has been developing new platforms to understand how Zn behaves during discharge and charge, including 1-D cells and cells that mimic the geometry of a primary alkaline battery [1]. However, those platforms have their limitations. In this talk, another new cell, coined the “gravity cell” will be discussed. The gravity cell has a small well where Zn (either as raw powder or in slurry form) is gravity deposited onto an indium foil current collector. Typically, a gel electrolyte is placed on top of the Zn bed, followed by liquid electrolyte, which also contains the counter and reference electrodes. The gravity cell is used to both discharge the Zn powder and to measure its corrosion characteristics. This can be done as a function of mass loading, which introduces limitations into the behavior as the Zn discharges from the Zn/gel interface towards the current collector. This type of discharge, limited by Ohmic resistance, requires new mathematical frameworks to extract the desired parameters. This talk will focus on the design of the cell as well as the derivation of the mathematical framework. Then, data will be shown using several types of Zn powder both in the presence and absence of surfactants that aim to reduce the corrosion rate.