Liquid metal anode enables zinc-based flow batteries with ultrahigh areal capacity and ultralong duration.

Zinc-based flow batteries (Zn-FBs) are promising candidates for large-scale energy storage because of their intrinsic safety and high energy density. Unlike that conventional flow batteries operate on the basis of liquid-liquid conversions, the Zn anode in Zn-FBs adopts a solid-liquid conversion reaction, presenting challenges such as dendrite formation, poor reversibility, and low areal capacity, limiting its long-duration energy storage (LDES) applications. Here, we developed a liquid metal (LM) electrode that evolves the deposition/dissolution reaction of Zn into an alloying/dealloying process within the LM, thereby achieving extraordinary areal capacity and dendrite-free Zn-FBs with outstanding cycling stability. Both Zn-I and Zn-Br flow batteries using LM electrodes exhibited an ultrahigh areal capacity of 640 milliampere-hours per square centimeter, corresponding to an ultralong discharge duration of ~16 hours, thus exceeding the LDES standard defined by the US Department of Energy. This study breaks the solid-liquid working mode of the Zn anode, offering an effective solution for LDES applications with Zn-FBs.