Unveiling optical isomerism as a new dimension for electrolyte design in aqueous zinc-ion batteries

Stereochemistry, exemplified by optical isomerism, plays a pivotal yet underexplored role in determining the electrochemical behavior of electrolyte additives in aqueous zinc-ion batteries (AZIBs). Although sharing identical molecular compositions, different optical isomers can exhibit distinct interfacial interactions, which significantly influence battery performance. Here, sodium malate with well-defined stereochemical configurations is employed as a model system to systematically decipher the correlation between molecular chirality and interfacial stabilization. Theoretical calculations reveal that malate anions preferentially adsorb on the zinc surface via carboxyl coordination, effectively reconstructing the Zn²⁺ solvation sheath and suppressing water-induced side reactions. More importantly, compared to the single enantiomers (L-SM and D-SM) that form fragile adsorption layers, the racemic DL-SM establishes a dynamically robust interfacial hydrogen-bond network, facilitating Zn²⁺ diffusion and facile desorption for uniform deposition. Benefiting from these synergistic effects, the Zn||Zn symmetric cells with the DL-SM additive achieve ultralong cycling stability of 5000 h at 1 mA cm⁻² and 0.25 mAh cm⁻² and maintain over 800 h even under harsh conditions of 10 mA cm⁻² and 5 mAh cm⁻². This study unveils the unique mechanistic role of racemic molecules in regulating electrode-electrolyte interfaces and opens a stereochemistry-guided paradigm for designing molecular additives toward high-performance AZIBs.