The managing director of Deakin University’s Battery Research and Innovation Hub, Dr Timothy Khoo, who was not involved in the research, said he was sceptical about any claims water batteries may one day replace lithium-ion, but said the protective layer developed by the RMIT-led team represents a “novel and quite unique” approach that solves “a key stability issue” with battery technology.

Pretty much my thoughts exactly when I read the article. The lead researcher of this project is bigging it up well beyond any rational scope, but they do have a novel invention here for dealing with dendrites in batteries.

Perhaps their technique could be applied to more conventional batteries, though I'm somewhat doubtful. Bismuth isn't exactly cheap, which is why lead acid dominates for most things.