(594f) Vertically Ordered Titanium Nitride Nanotube As a Highly Efficient Cathode Material for Lithium Sulfur Batteries
Lithiumâ??sulfur (Li-S) batteries could potentially revolutionize the rechargeable battery market due to their low cost and high energy density. However, low active material utilization due to poor sulfur conductivity, high rate of capacity fade due to the dissolution of lithium polysulfide intermediates in the liquid electrolyte, and active material loss due to the irreversible deposition of insoluble lithium sulfide (Li2Sn, nâ?¤2) on the electrodes surface are the main challenges facing further Li-S battery development.
Our recent study on TiN nanoparticles as a cathode material for Li-S battery using X-ray photoelectron spectroscopy (XPS), revealed that sulfur interacts with TiN nanoparticles during the discharge process. The resultant S-Ti-N retains the sulfur species on the cathode surface which can also adsorb higher order polysulfide species and undergo reduction to lower order polysulfides by transfer of electrons from the TiN electrode. In our current research, we used vertically aligned titanium nitride (VATN) nano-tubes as a cathode material for a Li-S battery with lithium/dissolved polysulfide configuration. VATN enhanced Li-S battery performance by increasing the active material utilization, and decreasing the volumetric expansion and redox shuttle reaction. In addition, the effect of nanotube size and length on Li-S battery cell capacity performance and retention were investigated. Electrochemical performance and the surface chemical environment of this new cathode material for the lithium polysulfide conversion reactions was studied by cyclic voltammetry, AC impedance spectroscopy and XPS analysis. The results may be of great significance to electrode material design for more efficient Li/S batteries.