Achieving a Reversible and Durable Zn Anode Using the Polyzwitterionic Hydrogel Electrolyte for Efficient Zn-Ion Energy Storage

Rechargeable aqueous Zn-ion hybrid supercapacitors (ZHSCs), featuring high safety, ecofriendliness, and cost effectiveness, have been regarded as a compelling complement to traditional lithium-ion batteries and have attracted increasing attention. However, the notorious dendrite growth and side reactions reduce the durability and reversibility of the Zn anode, causing a serious challenge for the application of ZHSCs. Herein, a polyzwitterionic P(HEA-co-SBMA)-based hydrogel electrolyte (denoted as PHSHE) for highly reversible Zn plating/stripping is fabricated to tackle tricky issues of Zn anodes and achieve high-performance ZHSCs. The zwitterionic groups carried by the polymer chains construct ion migration channels to facilitate ion migration, endowing the PHSHE with high ionic conductivity and Zn²⁺ transference number. Experimental findings reveal that the PHSHE can promote even Zn deposition and restrain side reactions. Accordingly, Zn anodes can be operated steadily in the PHSHE-intensified Zn//Cu cell for 650 cycles and Zn//Zn cell for 400 h. Furthermore, the quasi-solid-state ZHSC based on the PHSHE delivers a high capacity retention (80.8% after 14,000 cycles), mechanical flexibility, and application feasibility. This study is a step forward for stable Zn-based energy storage enabled by polyzwitterionic hydrogel electrolytes.