Interfacial lithium-nitrogen bond catalyzes sulfide oxidation reactions in high-loading Li2S cathode

Lithium sulfur batteries have exhibited unparalleled advantages in energy density. However, the sulfide oxidation reactions (SORs) in sulfur cathode are much more sluggish, which is mainly restricted by high conversion barriers. Herein, the catalytic Li-N bond sites are designed to activate SORs in high areal loading cathode with the multi-functions of bridging the active materials and carbon matrix tightly. The presence of catalytic Li-N bonds is co-revealed by X-ray photoelectronic spectroscopy and electronic energy loss spectroscope. As unraveled by theoretical physical van der Waals interaction analysis and various electrochemical tests, the improved kinetics and mechanism of SORs are achieved by motivating polysulfide interconversions and propelling lithium ion diffusion. Consequently, the so-fabricated electrode with abundant Li-N bond catalytic sites deliveries 900 mA h g-1 at 0.05 C and a stable retention of 74.3% at 1 C after 300 cycles. More impressively, high-loading with high-weight-content cathodes remain rapid SORs kinetics, high capacity utilization and retention from 3.0 to 6.9 mg cm-2. At 6.5 mg cm-2, the cathode displays 550 mA h g-1 at 0.76 mA cm-2 corresponded to 3.58 mA h cm-2, which is better than many reports. These results shed light on using intrinsic catalytic sites to realize application of batteries.

Automated summary

By introducing catalytic Li-N bond sites to activate the slow sulfide oxidation reactions in lithium-sulfur batteries, the kinetics and mechanism of the reactions are improved, leading to enhanced cycle performance and utilization of capacities.