A 3D Nitrogen-Doped Graphene/TiN Nanowires Composite as a Strong Polysulfide Anchor for Lithium-Sulfur Batteries with Enhanced Rate Performance and High Areal Capacity.

Abstract

Lithium-sulfur (Li-S) batteries have attracted remarkable attention due to their high theoretical capacity of 1675 mAh g-1 , rich resources, inexpensiveness, and environmental friendliness. However, the practical application of the Li-S battery is hindered by the shuttling of soluble lithium polysulfides (LiPSs) and slow redox reactions. Herein, a 3D nitrogen-doped graphene/titanium nitride nanowires (3DNG/TiN) composite is reported as a freestanding electrode for Li-S batteries. The highly porous conductive graphene network provides efficient pathways for both electrons and ions. TiN nanowires attached on the graphene sheets have a strong chemical anchor effect on the polysulfides, which is proved by the superior performance and by density functional theory calculations. As a result, the 3DNG/TiN cathode exhibits an initial capacity of 1510 mAh g-1 and the capacity remains at 1267 mAh g-1 after 100 cycles at 0.5 C. Even at 5 C, a capacity of 676 mAh g-1 is reached. With a high sulfur loading of 9.6 mg cm-2 , the 3DNG cathode achieves an ultrahigh areal capacity of 12.0 mAh cm-2 at a high current density of 8.03 mA cm-2 . This proposed unique structure gives a bright prospect in that high energy density and high power density can be achieved simultaneously for Li-S batteries.