Operando Visualization and Multi-scale Tomography Studies of Dendrite Formation and Dissolution in Zinc Batteries

Alternative battery technologies are required to meet growing energy demands and address the limitations of present technologies. As such, it is necessary to look beyond lithium-ion batteries. Zinc batteries enable high power density while being sourced from ubiquitous and cost-effective materials. This paper presents, for the first time known to the authors, multi-length scale tomography studies of failure mechanisms in zinc batteries with and without commercial microporous separators. In both cases, dendrites were grown, dissolved, and regrown, critically resulting in different morphology of dendritic layer formed on both the electrode and the separator. The growth of dendrites and their volume-specific areas were quantified using tomography and radiography data in unprecedented resolution. High-resolution ex situ analysis was employed to characterize single dendrites and dendritic deposits inside the separator. The findings provide unique insights into mechanisms of metal-battery failure effected by growing dendrites. Rechargeable metal batteries form the next generation of energy storage devices aiming to replace lithium-ion technology. Nonetheless, these batteries suffer from dendrites formation during repeated battery charging. Understanding how dendrites form is a key to building safer batteries. In the current work, we report multi-scale tomography studies of formation and dissolution of the dendrites in rechargeable zinc batteries. Using operando radiography we found that the dendrites form on surface inhomogeneities, with larger dendrites formed at higher current. The dendrite dissolution and regrowth results in formation of a porous metal network sparsely attached to the anode. The presence of separator does not prevent dendritic growth. Dendrites start growing inside, filling the submicron pores as dense deposits and penetrate the separator. They continue growing on top of the separator, forming a compact entangled network that cannot be re-dissolved back, causing permanent battery failure. This work emphasizes the importance of understanding the phenomena of dendrite formation occurring in rechargeable metal batteries. These batteries can reach quite a high specific energy but have inherently short life due to dendritic growth. The current work implements different tomographic methods to visualize dendritic growth in real time and to quantify various dendrite characteristics at submicron and nanoscale levels. The methodology presented here can be also extended to study the growth of other metal dendrites in aqueous and non-aqueous batteries.