Supervisors - Leonard Berlouis, University of Strathclyde, Alan Davidson, Edinburgh Napier University
PhD Student - Declan Bryans
Status - Complete
The project will investigate the use of new complexing agents to enhance the ability of the positive electrolyte to contain and store the bromine, thus increasing energy density and reducing self-discharge. We will investigate complexing agents which will suppress the presence of free bromine and promote its dispersal throughout the electrolyte, rather than separation into a new phase. Long chain alkyl ammonium or phosphonium salts and other organic heterocyclic salts with polar tails (e.g. carboxylates or sulphonates) will render the polybromide species more dispersible in the aqueous medium, while still encapsulating them in micelle-like structures.
What is important, in the choice of these or other ligands, is that the kinetics of discharge of the bromine species must not be compromised. The nature of the electrode surface species formed during charging, at various current densities, will be examined using spectroscopy and electroanalytical techniques. The improved dispersal method will be examined for its enhancement of the electrode kinetics during both charge and discharge processes. The build-up of any ‘organic’ layer on the positive carbon composite electrode during charge will be closely monitored through electrochemical impedance spectroscopy measurements as well as by the simpler current interrupt method. Any process which contributes to Ohmic losses in the system will be very carefully examined to quantify its real benefits.