(719d) Highly Structured Titanium Nitride As Novel Cathode Materials of Lithium Sulfur Batteries

The Lithium Sulfur battery could recognized as one of the most promising options for electric vehicles (EV) to achieve a larger range of drive, because of its higher energy density of around 1680 mA h/g, compared to conventional lithium ion batteries. However, there are some challenges facing Li−S battery application and further commercialization, such as: low electron transfer due to the insulating nature of sulfur, high self-discharge rate due to soluble polysulfide shuttle mechanism, and high rate of capacity fade due to the precipitation of insoluble polysulfide on the cathode and Li anode surface.

In this research, we investigated titanium nitrides as novel cathode materials for Li/S batteries, aiming to mitigate the capacity decay as one of the most severe issues to deteriorating battery performance. Titanium nitrides are reported as polysulfide mediator to introduce a bonding between sulfur and titanium, thus the shuttle mechanism could be inhibited. Also, the use of nanostructure could serve as a spatial confinement to host active material sulfur. In this way, either the size of sulfur molecule or insulating precipitates could be restricted. In order to obtain a better understanding of the electrochemical performance and the mechanisms underlying polysulfides redox reactions of all cathode materials, X-ray diffraction (XRD), scanning electron microscopy (SEM) in addition to electrochemical spectra (EIS) measurement have been applied. TiN exhibited the most promising capacity performance as it can adsorb lithium polysulfides effectively and transfer electrons in a facile manner. As a result, the active material and surface area loss were reduced and the capacity and capacity retention of the cell were enhanced.