A hydrogel electrolyte with ultrahigh ionic conductivity and transference number benefit from Zn2+?highways? for dendrite-free Zn-MnO2 battery

Aqueous zinc ion batteries (AZIBs) have been regarded as promising energy storage devices owing to high safety and abundant resources. However, it still remains a great challenge to solve the issue of Zn dendrites. So far, some efforts have been made to inhibit dendrites using hydrogels as electrolytes. Nevertheless, it's more chal-lenging to improve ionic conductivity of hydrogel electrolyte to ensure it's high enough to provide an envi-ronment for rapid transmission of Zn2+. Therefore, new strategies that can simultaneously solve above problems must be explored. Herein, a semi-interpenetrating network P(PEGMEA-AM)/PAM hydrogel electrolyte (s- PPMHE) with molecular chain designability was innovatively constructed. Abundant functional C-O-C groups in linear polymer chain of s-PPMHE can reduce the electrostatic potential of hydrated Zn2+ and release trapped Zn2+, thus significantly accelerating Zn2+ migration with an ultrahigh transference number (tZn2+ = 0.82). Thanks to the unique structural design, s-PPMHE has good mechanical stability and coordination ability with Zn2+, which is conducive to constructing ion migration channels and immobilizing water molecules, thus alle-viating water-related parasitic reactions. The theoretical calculation results reveal that s-PPMHE can regulate Zn2+ electric field distribution and boost desolvation kinetics. Therefore, the Zn||s-PPMHE||MnO2 cells exhibit excellent electrochemical performance involving high average coulombic efficiency of 98.9% and ultrahigh specific capacity of similar to 300 mAh/g at 0.05C (97% of theoretical capacity). Furthermore, s-PPMHE delivers excellent ionic conductivity of 82.65 mS/cm and over 350 h zinc stripping/plating cycling properties. Moreover, the flexible pouch AZIBs based on s-PPMHE show stable voltage under different conditions. This work provides a novel and exploratory strategy for design of hydrogel electrolyte at molecular chain level, and opens up a new avenue to design functional hydrogel matrix for high-performance electrochemical devices.

Automated summary

A novel semi-interpenetrating network P(PEGMEA-AM)/PAM hydrogel electrolyte (s- PPMHE) with molecular chain designability was successfully constructed in this study. The abundant C-O-C functional groups in the linear polymer chain of s-PPMHE could significantly accelerate Zn2+ migration and regulate the electric field distribution of Zn2+, resulting in excellent electrochemical performance.