Polyanionic hydrogel electrolyte enables reversible and durable Zn anode for efficient Zn-based energy storage

Aqueous Zn-ion energy storage systems, which are expected to be integrated into intelligent electronics as a secure power supply, suffer poor reversibility of Zn anodes, predominantly associated with dendritic growth and side reactions. This study introduces a polyanionic strategy to address these formidable issues by developing a hydrogel electrolyte (PACXHE) with carboxyl groups. Notably, the carboxyl groups within the hydrogel structure establish favorable channels to promote the transport of Zn2+ ions. They also expedite the desolvation of hydrated Zn2+ ions, leading to enhanced deposition kinetics. Additionally, these functional groups confine interfacial planar diffusion and promote preferential deposition along the (002) plane of Zn, enabling a smooth surface texture of the Zn anode. This multifaceted regulation successfully achieves the suppression of Zn dendrites and side reactions, thereby enhancing the electrochemical reversibility and service life during plating/stripping cycles. Therefore, such an electrolyte demonstrates a high average Coulombic efficiency of 97.7% for 500 cycles in the Zn||Cu cell and exceptional cyclability with a duration of 480 hat 1 mA cmz/1 mA h cm-2 in the Zn||Zn cell. Beyond that, the Zn-ion hybrid micro-capacitor employing PACXHE exhibits satisfactory cycling stability, energy density, and practicality for energy storage in flexible, intelligent electronics. The present polyanionic-based hydrogel strategy and the development of PACXHE represent significant advancements in the design of hydrogel electrolytes, paving the way for a more sustainable and efficient future in the energy storage field.(c) 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.