From liquid to solid: Advanced electrolyte design strategies for next-generation high-performance anode-free lithium/sodium/potassium batteries

Anode-free lithium/sodium/potassium batteries have emerged as promising candidates for next-generation energy storage due to their simplified structure, high energy density, low cost, and enhanced safety. However, their practical application is still hindered by finite metal sources and the high reactivity of metals. Recent progress in electrolyte design has demonstrated great potential to overcome these limitations. In liquid electrolytes, tailored electrolyte formulations have significantly improved the cycling performance of anode-free batteries (AFBs). Furthermore, advancements in solid-state electrolytes have further enhanced the stability of AFBs by suppressing side reactions at the solid-solid interface. This review summarizes advanced electrolyte design strategies for high-performance anode-free lithium/sodium/potassium batteries, spanning from liquid to solid-state systems. The underlying mechanisms are thoroughly analyzed, with an emphasis on electrolyte formulation and interface engineering strategies. A systematic comparison between liquid and solid electrolytes is also presented. Future directions are outlined to guide the practical application of AFBs. This review may further inspire the development of other anode-free systems, such as Al-, Mg-, and Zn-based batteries.