Fabricating a Gel Electrolyte Based on Lignin-Coated Nanosilica to Enhance the Reversibility of Zinc Anodes for Rechargeable Aqueous Zn/MnO₂Batteries

When a conventional aqueous ZnSO4 solution is used as the electrolyte, rechargeable aqueous Zn/MnO2 batteries suffer from inferior electrochemical performance because of the corrosion, dendrites, and passivation on zinc anodes. Herein, a novel gel electrolyte was fabricated by adding lignin/fumed silica composites to the reference aqueous electrolyte (RAE) (2 M ZnSO4 + 0.2 M MnSO4) for the purpose of mitigating the aforementioned issues of zinc anodes. Results of linear polarization and chronoamperometry showed that the as-prepared gel electrolyte reduced deterioration on zinc (up to 38.9%) and supported planar zinc deposits. Batteries using this gel electrolyte presented a higher open-circuit voltage after 24 h of monitoring and superior rate performance compared to batteries using the RAE. Most importantly, the discharge capacity of the batteries using this gel electrolyte after 3000 cycles at 1.5 A g-1 was still up to 106.2 mA h g-1, which was much higher than that (39.6 mA h g-1) of the batteries using the RAE. Observation through X-ray diffraction and scanning electron microscopy characterizations of the post-run zinc anodes revealed that this gel electrolyte could strongly inhibit the formation of zinc dendrites and reduce the production of byproducts (3Zn(OH)2·ZnSO4·xH2O) during the operation of the battery. This study is highly significant to the development of advanced aqueous batteries with high safety.