Methods-Ampero-Coulometry: A New Technique for Understanding Lithium-Sulfur Electrochemistry

Despite limited commercial success, lithium sulfur technology (LST) is still far from competing existing Li-ion technology. One of the main reasons hindering the success of LST is the complexity of lithium-sulfur chemistry during electrochemical charging and discharging. Dissolution of sulfur species in the electrolyte solution exacerbates the difficulties of this system. Therefore, a comprehensive understanding of sulfur species and their kinetics during charge/discharge process is paramount for a high-performance lithium-sulfur battery. We present a new technique we refer to as Ampero-Coulometry, which takes the chronoamperometric (galvanostatic) charge-discharge curves and mathematically transforms them to a series of curves that reveal the cation diffusional rate inside carbon-sulfur porous electrodes at different states of charge/capacity. This technique allowed us to track the overall Li+ ion diffusional rate inside a Li-S cell over a complete state of discharge. As dissolution of sulfur species and their interplay inside a porous sulfur electrode has a significant role in limiting Li-S battery capacity, and method allows correlation between the known mechanism of polysulfide dissolution, the kinetics of a sulfur electrode, and its response.

Automated summary

Despite limited commercial success, lithium sulfur technology still lags behind existing Li-ion technology due to the complexity of lithium-sulfur chemistry and sulfur dissolution in the electrolyte solution. A comprehensive understanding of sulfur species and their kinetics is crucial for high-performance lithium-sulfur batteries. We proposed a new technique called Ampero-Coulometry, which mathematically transforms chronoamperometric charge-discharge curves to reveal the cation diffusional rate in carbon-sulfur porous electrodes at different states of charge/capacity. This technique allows tracking of Li+ ion diffusional rate and correlates with the mechanism of polysulfide dissolution and the kinetics of a sulfur electrode.