Poly(ionic liquid) additive: Aqueous electrolyte engineering for ion rectifying and calendar corrosion relieving

Apart from the key function of regulating zinc (Zn) ions transport kinetics of aqueous Zn-ion energy storage devices, electrolytes also play an important role in restraining the inevitable parasitic reaction and intense dendrite growth on the Zn anode interface. Hence, in this work, a novel poly(ionic liquid) (poly(1-carboxymethyl-3-vinylimidazolium bromide, PCMVIm) additive is rationally designed and applied for Zn ion electrolyte optimization. The carboxyl-rich poly(ionic liquid) additive with polymer chain structure stabilizes the electrode/electrolyte interphase via strong Zn adsorption, and remarkably promotes uniform Zn deposition on its surface, endowing it with strong ion rectifying effects. The PCMVIm additive also effectively reduces byproduct formations on the Zn anode and maintains stable surface impedance against calendar corrosion. Notably, the optimized electrolyte with a 5 % PCMVIm additive ratio exhibits enhanced ionic conductivity (15.13 mS·cm⁻¹) and remarkable Coulombic efficiencies of over 99.4 % for 700 h. The exceptional electrochemical performance of the modified electrolyte endows ultra-long cycle stability, high Coulombic efficiency, and outstanding rate capability for both Zn ion hybrid supercapacitor and Zn ion battery applications. This study provides a novel electrolyte additive engineering for durable aqueous energy storage devices. © 2023 Elsevier B.V.