Electrode Kinetics of Organodisulfide Cathodes for Storage Batteries

The electrode kinetics of a diverse group of organodisulfide cathode materials have been systematically investigated. The electrochemical behavior of these redox couples was studied as a function of the organic moiety (R) in the organodisulfide compounds (RSSR). These studies were performed with a variety of working electrodes, including platinum, glassy carbon, graphite, stainless steel, aluminum, and copper. The possible reaction pathways and mechanisms have been hypothetically postulated, theoretically analyzed, and experimentally verified. Observations showed that while electron transfer rate constants varied with organic moiety, the mechanistic details of the redox path were invariant with the R groups of the organodisulfides studied. The reaction mechanism, as determined from experimental observations, can be expressed as for the oxidation of thiolate anions (RS − ) to the corresponding organodisulfides. The first step in the redox mechanism, charge transfer, is rate determining, while the second step, chemical reaction, is at equilibrium. The observed transfer coefficients are quite asymmetric and vary as a function of the R group in RSSR and the electrode materials. The standard rate constants are also affected by the nature of the organic moiety, R, and are in the range of 10 −8 –10 −6 from ambient to 100°C. Further, and in particular, electrode kinetics have been enhanced by the addition of several electrocatalysts.