Critical effects of electrolyte recipes for Li and Na metal batteries

The pursuit of rechargeable batteries with high energy density has triggered enormous efforts in developing Li/Na metal batteries considering the extremely high specific capacity of Li/Na metal anodes. As is typical for a new battery system, electrolyte design should immediately keep up with the specific electrode chemistry. This is especially true since Li/Na metal anodes face the problems of dendritic growth, hyper-reactivity, and an intrinsic safety concern, but the conventional electrolytes used for Li/Na-ion batteries fall short in sustaining their stable cyclability. Here, we intend to identify and elucidate the critical effects brought by the electrolyte recipes in stabilizing Li/Na metal batteries. In addition, the working mechanism of fluoroethylene carbonate (FEC) and the controversial role of LiF were reviewed. Based on a thorough discussion on these effects, we propose strategies that should be taken further. Finally, the remaining open questions and potential research directions for future development have been emphasized.