Reduction of Dendrite Formation in Zn Electrodes By Controlled Pulse Electrodeposition

Great efforts have been devoted to extending the use of Zinc for secondary batteries due to its high energy density, abundance and environmental sustainability. Nevertheless, there are several drawbacks preventing the implementation of Zn electrode in rechargeable batteries. One of the major limitations of a reversible Zn electrode is the formation of dendrites upon cycling. The morphology of the electrode undergoes significant changes leading to the formation of metallic Zinc needles. In a battery, these dendrites can penetrate through the separators, resulting in short-circuit and reducing significantly the lifetime of the battery.

Several strategies have been proposed to address this issue, ranging from incorporating certain additives in the electrolyte, to the use of special separators as a physical barrier between electrodes. Here, we present a strategy to suppress dendrite formation based on controlling the electrodeposition using designed charge pulse profiles. Understanding and designing a suitable pulse profile requires a large number of experiments. In order to make this possible in a reasonable amount of time, high throughput evaluation of the influence of a chosen electrochemical pulse deposition profile on the morphology was carried out using a specifically designed Scanning Droplet Cell (SDC). The SDC offers the advantage of performing automatically many experiments in a short timeframe enabling the evaluation of a wide vari­ety of parameters that may affect electrodeposition of Zinc. The electroreduction of ZnO proceed via a two-step process. Zincates dissolved in the pores of the paste electrode are reduced to metallic zinc. Due to the consumption of zincates, ZnO dissolves in the solution. Therefore, controlling the very early stage of the formation and growth of Zn nuclei from the reduction of zincates allows the redistribution of the material during charge. In addition, diffusion limitation of zincates was considered as a key factor for controlling the electrodeposition of Zn. Finally, our study envisions the application of these pulse profiles in a three electrode prototype cell.