A Development of High-Capacity Organosulfur Cathodes for Li-ion Batteries – A DFT Study: Development of High-Capacity Organosulfur Cathodes for Li-ion Batteries – A DFT Study

Lithium-ion batteries have dominated the portable electronics market and show great promise in large-scale applications such as smart grids and EVs. To date, commercial metal oxide cathodes like LiCoO2, LiFePO4, or LiNixMnyCoZO2, are mainly used. However, ores and the resources of these metal oxides are very limited [1-3]. Several research groups focused on searching for a new generation of rechargeable lithium battery technologies with low cost using more environmentally friendly and naturally abundant materials. The advantages of organic materials are discussed in three aspects, compared with inorganic cathode materials [4]. Firstly, organic compounds consisting of a lightweight elements such as C, H, O, N, and S, which leads to low cost and high gravimetric energy density. Secondly, these materials are structurally flexible and stable. In contrast, inorganic materials undergo structural changes during dis/charging, leading to diffusion of alkali ions from the structure is very difficult. Thirdly, organic compounds can provide multiple lithiation sites leading to high energy densities and tune the redox properties by different substituents [5]. The current study is focused on organo sulphur compounds as they possess high theoretical capacities due to multi-electron reactions of S-S bonds [6-7]. In the present study, DFT methods are applied to investigate the redox properties of several organosulfur organic compounds, namely benznesulphur, napthasulphur, anthrasulphur, tetrasulphur, petnasulphur, sumanenesulphur, and coronenesulphur. The computed redox properties are described based on the position of sulphur atoms on aromatic ring structures. Also, we understood the redox values are affecting as increasing the number of reacted lithiums. This investigation reveals an essential finding of mono sulphur, disulphide bond containing organic cathodes and their redox potential differences. Also, we calculated the theoretical performance of the highest redox potential exhibiting molecules. Finally, we found that pentacene sulfur has the highest redox potential and theoretical performance. It can take up to eight lithium per molecule, showing an exceptionally high charge capacity (409 mAhg-1). The lithiation mechanism of the Pentacene molecule is given in Figure (B), where the electron from Li-metal is added to the molecule followed by Li+-ion. A total of eight lithium reacted with the molecules showing a theoretical capacity of ~400 mAh/g. The complete findings will be presented.