Iodine network speeds reactions in experimental solid-state sulfur batteries
In experimental solid-state batteries, a peer-reviewed study placed iodine near sulfur within porous carbon to aid electron transfer. Reaction with the solid electrolyte created a mediator network across the positive electrode. Experimental cells sustained charging and cycling under different test conditions. The results describe an electrode architecture tested in pressure cells at room temperature.
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Iodine mediates electron transfer between solids
A single peer-reviewed laboratory study tested an iodine-containing positive electrode in lithium-sulfur cells containing only solid components. The sulfur electrode offers high theoretical storage capacity, but slow reactions and weak electron and ion transport restrict conversion between solid particles. Researchers placed sulfur and iodine close together inside small carbon pores. The resulting amorphous mixture had no well-defined crystal arrangement.[1]
A connected mediator network extends across the electrode
Iodine undergoes rapid oxidation and reduction and mediates electron transfer across particle boundaries. It also reacts with the sulfide solid electrolyte, creating connected iodine and iodide regions throughout the positive electrode. Structural and chemical measurements accompanied electrochemical tests. Carbon-and-sulfur comparison electrodes provided a baseline for the iodine-containing composition. The network extended the mediator’s reach beyond an individual carbon particle.[1]
At higher charging rates, capacity declined while the iodine-containing cells sustained solid-state conversion. Extended cycling and higher active-material loading were examined in separate experiments using different currents and compositions.[1]
Capacity is measured against sulfur and iodine mass
The experiments used custom pressure cells at room temperature, with contact between solid particles maintained in that arrangement. Specific capacity was normalised to sulfur and iodine mass, excluding electrolyte, carbon and cell hardware. The reported results concern this experimental electrode architecture. The authors identify iodine movement and its reaction kinetics with sulfur compounds as needing a more quantitative explanation.[1]
