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 Zn^(2+)ions.They also expedite the desolvation of hydrated Zn^(2+)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 h at 1 mA cm^(-2)/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.

An integrated portable bio-monitoring system based on tough hydrogels for comprehensive detection of physiological activities

Advanced soft ion-conducting hydrogels have been developed rapidly in the integrated portable health monitoring equipment due to their higher sensitivity,sensory traits,tunable conductivity,and stretchability for physiological activities and personal healthcare detection.However,traditional hydrogel conductors are normally susceptible to large deformation and strong mechanical stress,which leads to inferior electro-mechanical stability for real application scenarios.Herein,a strong ionically conductive hydrogel(poly(vinyl alcohol)-boric acid-glycerol/sodium alginate-calcium chloride/electrolyte ions(PBG/SC/EI))was designed by engineering the covalently and ionically crosslinked networks followed by the salting-out effect to further enhance the mechanical strength and ionic conductivity of the hydrogel.Owing to the collective effects of the energy-dissipation mechanism and salting-out effect,the designed PBG/SC/EI with excellent structural integrity and robustness exhibits exceptional mechanical properties(elongation at break for 559.1%and tensile strength of 869.4 kPa)and high ionic conductivity(1.618 S·m^(-1)).As such,the PBG/SC/EI strain sensor features high sensitivity(gauge factor=2.29),which can effectively monitor various kinds of human motions(joint motions,facial micro-expression,faint respiration,and voice recognition).Meanwhile,the hydrogel-based Zn||MnO_(2)battery delivers a high capacity of 267.2 mAh·g^(-1)and a maximal energy density of 356.8 Wh·kg^(-1)associated with good cycle performance of 71.8%capacity retention after 8000 cycles.Additionally,an integrated bio-monitoring system with the sensor and Zn||MnO_(2)battery can accurately identify diverse physiological activities in a real-time and non-invasive way.This work presents a feasible strategy for designing high-performance conductive hydrogels for highly-reliable integrated bio-monitoring systems with excellent practicability.