There have been new developments of new sulfur cathode materials to enhance the cycling stability of (Li-S) batteries. These new sulfur cathodes are based on metal oxides, which are intrinsically polar materials that can strongly interact with polar polysulfides species because the surface doesn’t need modification for interfacial adsorption ^[1,2]. I will first present the hybrid functional calculations we performed using the Auxiliary Dynamics Matrix Method (ADMM) ^[3,4] with varying percentages of exact Hartree−Fock exchange (hfx), ranging from 10 to 50% hfx to compute accurately the band gaps, and to determine the stable surface orientations of the Magnéli-phase of Ti₄O₇, and Anatase TiO₂. Relying on the previous results, I will discuss the first principles molecular dynamics simulations ^[4] we conducted to investigate the interaction mechanisms, and the dynamics properties of the polysulfides Li₂S_x  (x=1, 2, 4, 6) on the identified stable surfaces of the Magnéli-phase of Ti₄O₇, and Anatase TiO₂. Finally, I will discuss the role of the explicit solvent molecules in the solubility of the lithium polysulfides at the interfaces of the investigated models.

References:

[1] Tao, Xinyong and Wang, Jianguo and Ying, Zhuogao and Cai, Qiuxia and Zheng, Guangyuan and Gan, Yongping and Huang, Hui and Xia, Yang and Liang, Chu and Zhang, Wenkui and Cui, Yi, Nano Letters, 14, 5288-5294, (2014).

[2] Pang, Quan and Kundu, Dipan and Cuisinier, Marine and Nazar, L. F., Nat Commun, 5, 4579, (2015).

[3] Guidon, Manuel and Hutter, Jürg and VandeVondele, Joost, Journal of Chemical Theory and Computation, 6, 2348-2364, (2010).

[4] CP2K, http://www.cp2k.org/