Realizing high zinc reversibility in rechargeable batteries

Rechargeable zinc metal batteries (RZMBs) offer a compelling complement to existing lithium ion and emerging lithium metal batteries for meeting the increasing energy storage demands of the future. Multiple recent reports have suggested that optimized electrolytes resolve a century-old challenge for RZMBs by achieving extremely reversible zinc plating/stripping with Coulombic efficiencies (CEs) approaching 100%. However, the disparity among published testing methods and conditions severely convolutes electrolyte performance comparisons. The lack of rigorous and standardized protocols is rapidly becoming an impediment to ongoing research and commercialization thrusts. This Perspective examines recent efforts to improve the reversibility of the zinc metal anode in terms of key parameters, including CE protocols, plating morphology, dendrite formation and long-term stability. Then we suggest the most appropriate standard protocols for future CE determination. Finally, we envision future strategies to improve zinc/electrolyte stability so that research efforts can be better aligned towards realistic performance targets for RZMB commercialization. Zinc metal batteries (ZMBs) provide a promising alternative to lithium metal batteries but share the formidable challenges in reversibility. The authors discuss the key performance metrics of ZMBs and propose a protocol to assess the true reversibility of zinc metal anodes.