Three-electrolyte electrochemical energy storage systems using both anion- and cation-exchange membranes as separators.

Abstract A three-electrolyte cell configuration, in which an additional compartment filled with salt solution is created between the cation-exchange membrane and the anion-exchange membrane to separate the respective opposite charged ionic species, can be used to realize novel electrochemical systems using promising redox couples. Using lead-acid metal hydride hybrid redox couple as a typical three-electrolyte prototype, we monitored the potential change of individual components during operation to obtain better understanding on the factors affecting the electrochemical performance (including types of salt solution, electrolyte concentration, inter-electrode gap). Key issues (i.e., salting-out) and proposed solutions are discussed. This work offers new solutions to develop promising energy storage techniques. Highlights • Effect of salt solution, concentration and inter-electrode gap of the three-electrolyte battery system was studied. • Salt solution with higher ionic conductivity in the buffer chamber, lowers the change voltage across the membranes. • The inter-electrode gap is optimised to reduce the internal resistance of the system. [ABSTRACT FROM AUTHOR]