The anchoring effect of Nb-based MXenes lithium-sulfur batteries: A first-principles study

The dissolution and diffusion of S-species in the electrolyte are one of the most important reasons affecting the development of lithium-sulfur batteries. MXenes, a two-dimensional material which has received a lot of attention recently, is investigated in lithium-sulfur (Li–S) batteries due to its excellent properties. Most of the current reports focus on Ti-based MXenes materials, while there are few studies on Nb-based MXenes materials. In this paper, the interactions between lithium polysulfide and Nb2C-MXenes as well as O-functionalization (Nb2CO2 and Nb3C2O2) and S-functionalization (Nb2CS2 and Nb3C2S2) are investigated by using density functional theory calculations (DFT). According to the calculated results, both O-functionalized and S-functionalized have sufficiently large adsorption energy to inhibit the shuttle effect which occurs during the cycling of Li–S battery. As a comparison, O-functionalized MXenes have a more suitable adsorption energy for Li–S battery cathode materials, while S-functionalized MXenes have a lower ion diffusion potential barrier. In addition, all studied materials retain their original metallic properties after adsorption of lithium polysulfide, which contributes significantly to the electrochemical performance of Li–S batteries during charging and discharging. The results may be useful for investigating high-performance storage materials with Nb-based MXene materials.