Kinetic Enhancement of Sulfur Cathodes by N-Doped Porous Graphitic Carbon with Bound VN Nanocrystals.

Abstract

The reaction kinetics of sulfur cathodes generally control the performance of lithium-sulfur (Li-S) batteries. Here, N-doped porous graphitic carbon with bound VN nanocrystals (3D VN@N-PGC), which is synthesized in one pot by heating a mixture of glucose as C source, urea as N source, and NH4 VO3 as V source, is reported to be an superior electrocatalytic cathode host for Li-S batteries. Notably, the VN nanocrystals, strongly bound to the N-PGC network, form via in situ reactions among the thermolytic products of starting materials. The dopant N atoms and bound VN nanocrystals exhibit synergistic electrocatalytic effects to promote the cathode reactions of the Li-S cells. The observed enhancements are supported by density functional theory simulations and by the observation of electrocatalytic N- and V-intermediate species, via X-ray absorption near-edge structure spectroscopy. Li-S cells assembled using 3D VN@N-PGC as cathode host exhibit superior performance in terms of specific capacity (1442mA h g-1 at 0.1 C), rate capability (641mA h g-1 at 4 C), and cycle life (466mA h g-1 after 1700 cycles at 2 C, corresponding to a capacity decay of 0.020% per cycle). The one-pot methodology is facile and scalable and offers a new approach for synthesis of various metal nitride-containing materials for other electrocatalytic applications.