Nanostructured Electrocatalysts of Metal Compounds for Facile Sulfur Conversion Kinetics of Lithium-Sulfur Batteries and Regulated Growth of Lithium Sulfide

Lithium-sulfur (Li-S) batteries, a secondary battery using elemental sulfur as the main cathode material, have been attracting attention as next-generation energy storage systems due to their high theoretical energy density (2600 Wh kg-1) based on the theoretical capacity of 1675 mAh g-1. Sulfur is abundant and nontoxic, but it still suffers from dissolution of polysulfides and sluggish conversion of insulating sulfur, and randomly deposited solid lithium sulfide (Li2S) from lithium polysulfides (LiPSs), which leads to short cycle life and low sulfur utilization during cycling. To tackle these issues, we introduced several nanostructured electrocatalysts decorated with sulfiphilic metal compounds that facilitated the sulfur conversion and regulated Li2S growth for high sulfur utilization. Surprisingly, it enhanced sulfur utilization in harsh conditions for the commercialization of Li-S batteries, such as ultra-high C-rate and high areal loading mass, which is essential for replacing the current state of lithium-ion battery technology. Highly conductive Janus-structured CNT particles, amorphous metal oxide, metal boride/oxide heterojunction, and phosphorus-doped metal compounds were proposed as electrocatalysts to enhance sulfur utilization and regulate Li2S growth. Density functional theory calculation presents a mechanism for enhanced sulfur conversion and particulate Li2S growth by promoted diffusion and favorable clustering of Li2S. Highly reversible sulfur conversion and utilization were obtained. Morphological and chemical approaches successfully enabled high energy of Li-S batteries, even under kinetically limited conditions, by simply enhancing the local adsorption properties of LiPSs.

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