Real Time Observation of Electrochemical Deposition Process of Zinc Dendrites Via Correlative Optical and X-Ray Microscopy

Abstract

Low cost, durable, and relatively safe electrode materials are highly desirable for electrochemical energy storage devices, but the implementation of many materials, including zinc, is limited by morphological transformations that take place during electrochemical cycling [1]. The formation of unstable growth morphologies, notably dendrites with highly anisotropic and porous structures is vulnerable to mechanical vibrations and can cause catastrophic failure by shorting the anode and the cathode [2]. The development of improved secondary batteries depends critically on a detailed understanding of the physical and electrochemical processes at the electrode-electrolyte solid-liquid interface [3]. Recent advances in in situ electrochemical microscopy [4], with its unique ability to provide simultaneous temporally and spatially resolved information as well as electrochemical parameters, enable exploration of the underlying physics of electrochemical reactions at the solid-liquid interface [5]. In this work, we investigate electrodeposition process that forms and takes place on the surface and inside of metal electrodes at real time. By employing a microfluidic cell and the capability for liquid flow, we can introduce electrolytes (i.e. 8.9M KOH + 0.61M ZnO or 0.5M H2SO4 + 0.1M ZnSO4) with varying composition of metal ions, pH and chemical additives (i.e. Bi2O3 or PbSO4), and apply different current and voltage parameters to investigate their effects on the deposited morphology. We employ in situ correlative light and transmission X-ray microscopies to track nucleation, growth, and propagation of Zn dendrites. We also discuss the effects of additives to the electrolyte, which can change the onset of dendrite formation during the electrodeposition of Zn. We also compare these microfluidic cell results to liquid cell electron microscopy experiments in which we have recorded Zn morphology after galvanostatic deposition, and we will discuss the benefits and pitfalls of the correlative microscopy technique for the study of processes during battery operation.