Bimolecular synergistic chemistry in hybrid electrolytes for high-cycling-stability membrane-free zinc-bromine batteries

Aqueous zinc-ion batteries (AZIBs) are promising candidates for grid-scale energy storage owing to their inherent safety, low cost, and high theoretical capacity (820 mAh/g). However, membrane-free configurations suffer from severe lifespan limitations caused by interfacial side reactions and zinc dendrite growth. In this work, we pioneer a bimolecular synergistic electrolyte strategy based on sorbitol-gluconate complexes regulated by van der Waals interactions. The coordinated molecules simultaneously modulate zinc deposition morphology via anode surface adsorption and reconstruct the electrolyte solvation structure through hydrogen bonding, effectively suppressing dendrite formation, dead zinc accumulation, and parasitic hydrogen evolution. The optimized electrolyte enables Zn//Zn cells to achieve exceptional cycling stability (585 h at 10 mA/cm 2 ) 6-fold longer than baseline systems. When deployed in membrane-free Zn-Br 2 batteries, this synergy-driven chemistry demonstrates unprecedented compatibility with separator-less architectures, enabling more than 4000 stable cycles (1600 h) at 10 mA/cm 2 with 96.2 % Coulombic efficiency–tripling the lifespan of conventional ZnBr 2 electrolytes. Operando characterization confirms the dynamic self-adaptation of van der Waals-bonded complexes during cycling, which maintains stable electrode-electrolyte interfaces. This emergent bimolecular synergy redefines the design rules for high-performance, low-cost zinc batteries that operate without membranes. • Hybrid electrolyte design couples molecular cooperation with membraneless architecture. • Two molecules combine by van der Waals forces. • Zn//Zn symmetric cell stable cycling at 10 mA/cm 2 for 585h. • Synergistic mechanism enables 3 × lifespan extension in Zn-Br 2 batteries without membranes(1600h).