Energy Storage, 2nd Edition

Chapter 8Polysulfide – Diffusion Analysis

The ensuing analysis was prompted by problems encountered with the sulfur (–) electrode while developing a bromine/sulfide secondary cell for load leveling application possibilities. The lives of our composite carbon/plastic, negative electrodes were severely limited upon extensive cycling. After much research and experimentation, the puzzle of limited electrode cycle life was solved. The problem was caused by the erosion of carbon particles from the composite structure by the formation of hydrogen gas just under the surface of the somewhat porous plate. The polymer (plastic) component adheres very well to the total electrode structure and has a physical continuity that does not characterize the very frangible carbon components. After extended operation of this sort with gasses ejecting carbon, the electrode acquires a very high interface resistance and ceases operating as a functioning electrode, producing mono-sulfides due to starvation in the depths of the holes left by the separated carbon.

It is most important that we try to take into consideration any and all possible processes and mechanisms in our analysis of the experimental observations. It must also be understood that much of what is offered as explanations for cell behavior is in the realm of speculation – to be verified as we continue with these empirical studies.

The dynamics of molecular diffusion, ionic conduction, and the oxidation-reduction processes that occur at the ...