Detrimental Effects of Surface Imperfections and Unpolished Edges on the Cycling Stability of a Zinc Foil Anode

A zinc foil or sheet is the most common form of anode for aqueous zinc ion batteries since it is massively manufactured and readily accessible. Short circuits from dendrites grown on zinc foil anodes can dramatically decrease the cycling stability and lead to premature failure of the batteries. Here, we show that manufacturing-induced defects, including surface imperfections such as a roughened surface, microcracks, scratches, or fold lines, as well as unpolished edges from cutting can all promote local dendrite growth, leading to drastically decreased cycling stability of the batteries. Such surface imperfections and unpolished edges are quite common during metal sheet manufacturing and processing; therefore, their detrimental effects in zinc ion batteries should be factored in when evaluating and comparing device performances. Mitigation methods and new electrode processing techniques that can minimize these effects must be developed for safe deployment of zinc ion batteries on a large scale.