Though the cell setup developed will only serve for application in a laboratory context, we emphasize that engineering approaches can have a large impact on the performance of FIBs, and must be necessarily taken into account to establish the full potential of this battery technology . In special, previous reports on the performance of ASS-FIBs must be reconsidered under the aspect of cell engineering; the reversibility of fluoride materials is likely better than assumed, and cell design is a necessary development to distinguish materialspecific factors from cell-related factors such as stability of the percolation network and charge transfer processes at the interfaces.