Abstract
In recent years, the storage of energy produced by renewable sources has become a topic of great interest. Lead-acid batteries are widely used in this field, in particular those based on VRLA (Valve-Regulated-Lead Acid) technology, in which the electrolyte is immobilized inside the battery. In this paper, the use of a hydrogel as an electrolyte was considered. Hydrogel can be described as a three-dimensional network of a hydrophilic polymer that can absorb large amounts of water (or aqueous solutions) without dissolving. Pb and PbO2 nanostructured electrodes were used in the battery that used hydrogel as an electrolyte. Two different types of hydrogels were synthesised, both based on PVA that is a biodegradable, biocompatible, non-toxic, and non-carcinogenic polymer. The first one was obtained through physical gelling, the second one was obtained using borax (sodium tetraborate decahydrate) as a cross-linking agent. Preliminary tests of nanostructured lead-acid batteries using both types of hydrogels as an electrolyte were conducted for 100 cycles at 1C. The physically gelled hydrogel gave the best results in terms of efficiency, likely, owing to its greater absorption capacity. It was also verified that the recombination of the gases evolved during the charge phase (hydrogen and oxygen) takes place inside the battery itself. This is the major advantage of the gelled electrolyte in comparison with the liquid one.
