Hydrogen-Bond-Mediated Solvation Reconfiguration Homogenizes Ion Flux for Stable Sodium Metal Batteries

Abstract Anode-free sodium metal batteries (AFSMBs) offer the promise of high energy density and low cost; however, dendrite growth caused by nonuniform Na deposition severely compromises the battery’s cycling stability. In this study, the Na+ solvation structure is dynamically optimized through the synergistic interaction between weak hydrogen bonds formed by cyclic ether and chain ether, along with trace amounts of lithium nitrate (LiNO3), thereby lowering the desolvation energy barrier. This strategy not only achieves a uniform ion flux but also forms the solid electrolyte interphase (SEI) layer with high mechanical strength, thereby significantly improving the uniformity of Na+ distribution at the interface, which helps enhance the cycling stability of sodium metal batteries. Consequently, the sodium anode demonstrates a long cycle life of 1,300 cycles with a Coulombic efficiency (CE) as high as 99.97%. Furthermore, a 1 Ah anode-free pouch cell employing a Na4Fe3(PO4)2P2O7 (NFPP) cathode achieves a cycle life exceeding 280 cycles, with a capacity maintains above 93.3%, delivering a high energy density of 185 Wh kg–1. This work provides new insights into the design of electrolytes for AFSMBs and other metal batteries.