A Comparative Study of Agarose and Sodium Alginate-Based Gel Polymer Electrolytes for Zn-Based Batteries With CaV6O16·3H2O Cathode

Aqueous zinc-based batteries (ZIBs) are considered promising energy storage solutions, particularly targeting low-cost applications needed for levelling electricity production from renewable energy sources. However, numerous challenges need to be overcome to bring the technology to the market, chiefly including cathode dissolution, dendrite formation, hydrogen evolution reaction, and zinc corrosion. The optimisation of the electrolyte, particularly the use of gel-polymer electrolytes (GPEs), is demonstrated as a viable approach to solve or mitigate such issues. In this respect, a comparative study of two GPEs based on biopolymers, agarose and sodium alginate, is presented here. Despite the fast and facile preparation procedure, the GPEs demonstrate to be strongly effective in suppressing dendrite and byproduct formation on zinc metal anodes, due to the abundant ─OH groups along the chains in polymeric matrices. The electrochemical behaviour of GPEs is evaluated in terms of galvanostatic cycling in laboratory-scale zinc metal cells with a CaV6O16·3H2O cathode at low and high active material loadings of 2.5 and 5 mg cm−2, respectively. Resulting cycling performances in terms of specific capacity and rate capability are comparable (low loading electrodes) and even outperform (high loading electrodes) those obtained with a standard liquid electrolyte (2M ZnSO4) laboratory-scale cell, thus accounting for the promising prospects of the bio-polymer GPEs as an alternative green, sustainable electrolyte for next-generation Zn-based batteries.