Investigating the Impact of Solid-Electrolyte Interface on Dendrite Formation: A Case Study Based on Zinc Metal Electrodes

The formation of dendrites is the bottleneck to harvest the high theoretical capacities of metal anodes such as Li, Na, Mg, and Zn batteries. The critical current density, interfacial instabilities, and the characteristic of the solid-electrolyte interface (SEI) layer play a major role in the formation mechanisms of dendrites. In this study, we investigated the impact of the SEI layer on the electroplating of zinc metals in organic and aqueous electrolytes by using electrochemical techniques coupled with electron microscopy and X-ray photoelectron spectroscopy. First, the electrochemical response of Zn plating in organic or aqueous electrolytes was compared with the ones for Li and Na metal plating by using analogous perchlorate salt dissolved in the same organic solvent. Under similar charge conditions, the cycle life of the metal electrodes was longer in the order of Zn (aqueous) > Li > Zn (organic) > Na. The impact of the SEI layer is then investigated by electroplating Zn in aqueous for 20 cycles, and then switching it to organic electrolytes and vice versa. In organic electrolytes, the cycle life of the PAO-Zinc is almost three-fold longer than the as-received zinc electrodes. PAO stands for pre-cycled in aqueous electrolyte for twenty times. Overall, our study demonstrated the impact of surface chemistry and morphology on the formation of Zn dendrites. The methodology established here can be used to study the impact of electrolyte salt and additives on the formation of dendrites on metal electrodes.