Mechanistic Insights into Surface Chemical Interactions between Lithium Polysulfides and Transition Metal Oxides
journal contributionposted on 15.06.2017, 00:00 by Yiren Zhong, Ke R. Yang, Wen Liu, Peng He, Victor Batista, Hailiang Wang
The design and development of materials for electrochemical energy storage and conversion devices requires fundamental understanding of chemical interactions at electrode/electrolyte interfaces. For Li–S batteries that hold the promise for outperforming the current generation of Li ion batteries, the interactions of lithium polysulfide (LPS) intermediates with the electrode surface strongly influence the efficiency and cycle life of the sulfur cathode. While metal oxides have been demonstrated to be useful in trapping LPS, the actual binding modes of LPS on 3d transition metal oxides and their dependence on the metal element identity across the periodic table remain poorly understood. Here, we investigate the chemical interactions between LPS and oxides of Mn, Fe, Co, and Cu by combining X-ray photoelectron spectroscopy and density functional theory calculations. We find that Li–O interactions dominate LPS binding to the oxides (Mn3O4, Fe2O3, and Co3O4), with increasing strength from Mn to Fe to Co. For Co3O4, LPS binding also involves metal–sulfur interactions. We also find that the metal oxides exhibit different binding preferences for different LPS, with Co3O4 binding shorter-chain LPS more strongly than Mn3O4. In contrast to the other oxides, CuO undergoes intense reduction and dissolution reactions upon interaction with LPS. The reported findings are thus particularly relevant to the design of LPS/oxide interfaces for high-performance Li–S batteries.