Building electrode/electrolyte interphases in aqueous zinc batteries via self-polymerization of electrolyte additives

Aqueous zinc batteries offer promising prospects for large-scale energy storage, yet their application is limited by undesired side reactions at the electrode/electrolyte interface. Here, we report a universal approach for the in situ building of an electrode/electrolyte interphase (EEI) layer on both the cathode and the anode through the self-polymerization of electrolyte additives. In an exemplified Zn||V₂O₅·nH₂O cell, we reveal that the glutamate additive undergoes radical-initiated electro-polymerization on the cathode and polycondensation on the anode, yielding polyglutamic acid-dominated EEI layers on both electrodes. These EEI layers effectively mitigate undesired interfacial side reactions while enhancing reaction kinetics, enabling Zn||V₂O₅·nH₂O cells to achieve a high capacity of 387 mAh g^-1 at 0.2 A g^-1 and maintain >96.3% capacity retention after 1500 cycles at 1 A g^-1. Moreover, this interphase-forming additive exhibits broad applicability to varied cathode materials, encompassing VS₂, VS₄, VO₂, α-MnO₂, β-MnO₂ and δ-MnO₂. The methodology of utilizing self-polymerizable electrolyte additives to construct robust EEI layers opens a novel pathway in interphase engineering for electrode stabilization in aqueous batteries.