All-round supramolecular zwitterionic hydrogel electrolytes enabling environmentally adaptive dendrite-free aqueous zinc ion capacitors

Abstract

Aqueous zinc ion capacitors (ZICs) with hydrogel electrolytes (HEs) exhibit the advantages of high sustainability, inherent safety, appealing energy/power densities, and extraordinary mechanics, and thus have long been considered exceptional technology for large-scale flexible energy storage. However, the Zn anode is limited by dendrite failure, corrosion, and H₂ evolution in aqueous electrolyte, together with the difficulty of integrating multiple functions into a single HE, all of which resonate with each other leading to severe performance degradation in flexible ZICs in various complex scenarios. Herein, we propose a molecular engineering strategy to design an all-round supramolecular zwitterionic hydrogel electrolyte (SZHE) with built-in fast ion shuttles, yielding a critical series of performances of mechano-interfacial-environmental robustness, exceptional ionic conductivity (48 mS cm⁻¹), outstanding Zn²⁺ transference number (0.86), and desired self-healing ability. The in-depth characterization indicated that the SZHEs have superior capability to in situ repair the cycling-induced cracks and tune the Zn²⁺-solvation structure, coupled with superiority in guiding uniform Zn deposition and building an H₂O-poor interface at the Zn/electrolyte interface, which can protect Zn from dendrite growth and side reactions, as revealed by theoretical simulations and experimental characterizations. Considering these properties, collectively, our as-assembled ZICs performed much better in terms of capacity, energy density, and cycling lifespan from −20 °C to 60 °C than the state-of-the-art devices, with demonstrative applications ranging from biomedical devices to wearable electronics operating in harsh environments. This work may give insights into the development of SZHEs for dendrite-free and environment-adaptable Zn-based energy storage systems.