Bidentate coordination by cucurbituril for synergistic solvation and interface regulations toward stable Zn metal batteries

Abstract

Additives are frequently utilized to tackle dendrite and corrosion problems haunting zinc anode, thanks to their abundant functional groups. However, the relationship between functional groups geometric structures of additives and their working mechanisms stays rarely focused. Herein, in this work, through comparatively study cucurbit[6]uril (CB[6]) and cucurbit[8]uril (CB[8]) as additive, we reveal the critical role of functional groups structures in achieving solvation and interface chemistry regulations for advanced aqueous zinc-metal batteries (AZMBs). Bestowed with abundant carbonyl groups and characteristic cavity structure, both CB molecules enhance the electrolyte stability via reshaping hydrogen bond network. Besides, they both preferentially adsorb on Zn anode to induce a N-containing functional solid electrolyte interphase (SEI) to suppress corrosions. Still, among the two, CB[6] demonstrates more effective in solvation regulations. With its optimized cavity size and carbonyl oxygen spacing, higher nucleophilicity is obtained and bidentate coordination is achieved with enhanced control over Zn²⁺ deposition guidance, contributing to a dendrite-free Zn anode. As a result, CB[6] delivers exceptional performance, achieving a cycle life exceeding 5000 h and maintaining high capacity retention over 1000 cycles in PANI//Zn full cells. This work highlights the critical role of functional group geometric structures in additive design, providing a theoretical basis for the development of advanced multifunctional additives for AZMBs.

Graphical abstract