Acidic hydrogel electrolytes

Replacement of liquid electrolyte with a gelled one in batteries and other chemical devices has attracted increasing attention especially in terms of reliability, safety, flexibility and process fabrication. The research for the most suitable gel with high ionic conductivity, good electrochemical stability and mechanical strength has been the challenge to create new solid polymeric electrolytes (SPEs) for application in the field of batteries. A polymeric-based hydrogel has been recently developed for application in lead-acid batteries with peculiar chemical features allowing the tailoring of its properties by either varying the hydrolysis degree or blending it with other polymers.


The polymer is nontoxic, biodegradable and can swell at large extent without dissolution. In addition, it shows good chemical stability and can be easily gelled by a crosslinking agent. We prepared an acidic hydrogel electrolyte by mixing polymers and crosslinking agent in acid aqueous solution: the concentration of each component was optimized in order to enhance the performance of the gel as an solid polymeric electrolyte. We found that it is possible to synthetize a gelled electrolyte with conductivity values comparable to those of acid solutions.



Advantages

Oxygen and hydrogen evolution in the presence of hydrogels occur in the same potential range of the liquid acid solution supported by the hydrogels, but the current values were lower than those of the liquid electrolyte.
Our hydrogels showed a thermodynamic stability window greater than that of pure water that is only 1.23V. Besides, in comparison to the common organic electrolytes, hydrogels have a lower thermodynamic stability window, but are not toxic and flammable, and are less expensive.