Unravel the anchoring effect and charge changes of Li2Sn on 2D-TMDs for Li-S batteries: A DFT study

Abstract

Two-dimensional transition metal dichalcogenides (2D-TMDs) with a large specific surface area and stable layer structure, have been produced as catalysis, photonics, or other discipline materials. In this work, we investigated their strong polysulfide compatibility and new possible usage as lithium-sulfur (Li-S) batteries cathode materials. We explored the anchoring effect and charge changes of polysulfides (Li2Sn, n = 1, 2, 4, 6, 8, including S8) on 2D-TMDs (TM are Fe, Co, Cu, Zn, Ni, Pt, and Pd) matrix materials using first-principles calculations. The electrostatic potentials of 2D-TMDs indicated that they possess a plate structure with a positively charged core and negatively charged outer sides, which facilitates the adsorption of positively charged Li+. It was found that 2D-FeS2 is a special one, and it adsorbs Li2S stronger than other 2D-TMDs, with an adsorption energy of − 4.28 eV and charge changes of 1.32 e. We also confirmed a significant linear relationship between the power of charge changes (Q) and the adsorption energy: E = 0.43 + 1.76 Q2.8 for 2D-FeS2 and E = 0.08 + 2.74 Q1.5 for other 2D-TMDs, respectively. And the correlation coefficient is larger than 0.90. These seven materials are expected to be viable cathode materials, providing a theoretical foundation for the usage of 2D-TMDs in Li-S batteries.