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An unstable solid electrolyte interphase (SEI) layer on a metal electrode leads to issues of severe dendrite formation and side reactions, resulting in low cycle stability and safety hazards of metal-based batteries. Herein, a functional quinoid polymer (poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene), PDBM) is introduced on the surface of Na/Li metal, forming a flexible and uniform polymer–salt (PDBM-Na/Li)-based SEI with Na+/Li+ enriching property and low ion dissociation energy. The PDBM-Na layer enables a stable Na plating/stripping behavior with over 1200 h cycles at 2 mA cm–2 and Na∥Na3V2(PO4)3 full batteries with a capacity retention of 93% after 2400 cycles at 5 C. Equally important, a comparison study of PDBM-Na/Li layers on the cycling stability of Na/Li metals demonstrates that not only an appropriate ion adsorption energy but also a low dissociation energy is important for extending the cyclic lifespan of metal electrodes. This study provides deep insights into the structural design of functional polymers for alkaline anode protection.
Yue et al. (Fri,) studied this question.