Bonan Zhu1,2,David Scanlon1,2
University College London1,The Faraday Institution2
Bonan Zhu1,2,David Scanlon1,2
University College London1,The Faraday Institution2
Lithium-excess manganese-based disordered rock salts offer great opportunities for further increasing the capacities of lithium-ion batteries (> 300 mAhg<sup>-1</sup>). However, the existing materials are known to exhibit undesirable capacity fading and hysteresis<sup>1,2</sup>. Doping with high-valance transition metals offers the opportunity for tuning the short-range order of the disordered lattice as well as lowering the valance state of Mn, thereby mitigate the capacity fading though cationic redox. In this study, we construct cluster expansion models to investigate the effect of incorporating W dopants. The short-range orderings are extracted from Monte-Carlo simulations. While the inclusion of W raises the cationic redox capacity of Mn, the preferential configuration of W-Li cation nearest neighbour reduces the concentration of zero-transition-metal channels that allow Li conduction. Quantitative analysis shows a moderate reduction of active Li content, but the existence of Li-percolating networks remains affected. On the other hand, analysis of the charge densities shows that the oxidation state of W dopants can be different from the assumed 6+ state as in WO<sub>3</sub>, highlighting the delicate coupling between ionic and electronic structures in defective disordered materials. Effects of doping with other high-valance dopants, such as Sb, as well as co-anion doping will also be discussed.<br/><br/>(1) Lun, Z.; Ouyang, B.; Cai, Z.; Clément, R. J.; Kwon, D.-H.; Huang, J.; Papp, J. K.; Balasubramanian, M.; Tian, Y.; McCloskey, B. D.; Ji, H.; Kim, H.; Kitchaev, D. A.; Ceder, G. Design Principles for High-Capacity Mn-Based Cation-Disordered Rocksalt Cathodes. <i>Chem</i> <b>2020</b>, <i>6</i> (1), 153–168. https://doi.org/10.1016/j.chempr.2019.10.001.<br/>(2) Clément, R. J.; Lun, Z.; Ceder, G. Cation-Disordered Rocksalt Transition Metal Oxides and Oxyfluorides for High Energy Lithium-Ion Cathodes. <i>Energy Environ. Sci.</i> <b>2020</b>, <i>13</i> (2), 345–373. https://doi.org/10.1039/C9EE02803J.