In situ unveiling the conversion processes on the catalytic cathode in lithium-sulfur batteries.

Abstract

Lithium-sulfur (Li-S) batteries have attracted attention due to their high theoretical capacity of 1675 mAh g^-1. However, a knowledge gap remains regarding nanoscale lithium sulfide (Li₂S) reactions, limiting full S utilization and rational catalyst design. Here, we show how Li₂S nanoclusters transform and distribute under operation using in situ atomic force microscopy, providing the structure-(re)activity relationships. Comparing to the lamellar structures formed at noncatalyzed electrodes, Li₂S deposited at Pt catalytic electrode exhibited a spherical morphology. The zero-order reaction kinetics was captured on catalytic surfaces, differing from noncatalyzed electrodes. The electrodeposition of Li₂S follows the overpotential-driven progressive and instantaneous nucleation processes, showing a promoted deposition and reversible dissolution at the overpotential of 80 mV. The Li₂S transformation under high polysulfides concentrations indicated that an increase of catalytic sites and uniform distribution of Li₂S would be critical for practical Li-S batteries. Our work provides fundamental insights into Li₂S reaction kinetics, advancing the development of energy storage systems.