The big problem with flow batteries has been lack of energy density vs lithium ion batteries. Most of the articles I found were focused on the advantages of flow batteries for energy storage vs lithium ion batteries for energy storage, however I did find one article that suggested there may be a flow battery successful challenge to lithium ion batteries... eventually.  I have not seen any follow up on this approach that was being developed at Purdue University, so I don't know if it is still "in the works" or not.  It is not difficult at all, on the other hand, to find tons of articles from the past and from current publications about the big future for flow batteries in the area of Energy Storage, especially Vanadium Flow Batteries.

https://thedriven.io/2019/02/18/refillable-electric-car-tech-purdue-university/