Anionic redox and high-energy-density electrodes

        Conventional cathode materials used are typically lithium-containing transition metal oxides and phosphides (e.g., LiCoO2, LiFePO4, LiMn2O4) which store (release) electrical energy via (de-)insertion of Li+ ions, accompanied by redox reactions of the transition metal cation. The specific capacity of the cathode is therefore limited by the number of electrons per transition metal cation that can participate in the redox reaction. This exclusive dependence on the transition metal cations as the redox center has been challenged by the recent discovery of oxygen redox reactivity in Li-excess cathode materials. Exploration of the novel combined cationic and anionic redox chemistries with the goals of high energy density, no O2 loss, and low-cost are still ongoing and have drawn significant attention from the electrochemical energy storage field. Using first-principles tools, we were able to identify one special "Li6-O" local configuration, which is anionic redox active and can be used to realize significantly enhanced energy density in transition metal oxide electrodes.
Representative Publications
  1. C. Zhan, Z. Yao, J. Lu, L. Ma, V. Maroni, L. Li, E. Lee, E. E. Alp, T. Wu, J. Wen, Y. Ren, C. S. Johnson, M. M. Thackeray, M. Chan, C. Wolverton, K. Amine, Enabling the High Capacity of Lithium-rich Anti-fluorite Lithium Iron Oxide by Simultaneous Anionic and Cationic Redox, Nature Energy 2, 963–971 (2017).
  2. Z. Yao, S. Kim, J. He, V. I. Hegde, C. Wolverton, Interplay of Cation and Anion Redox in Li4Mn2O5 Material and Prediction of Improved Li4(Mn,M)2O5 Cathodes for Li-ion Batteries, Science Advances, 4, eaao6754 (2018).
  3. Q. Li, Z. Yao, J. Wu, M. M. Thackeray, C. Wolverton, V.P. Dravid, Dynamically visualization of the electrochemical delithiation of Li2MnO3, Under review.   
  4. Z. Yao, C. Zhan, J. Lu, L. Li, M. K. Y. Chan, M. M. Thackeray, C. Wolverton, Exploring the Combined Anionic and Cationic Redox Reactivity in the Super Li-rich Li5FeO4 Based High-Energy-Density Cathode Materials, Under review.
  5. L. Li, F. Castro, J. S. Park, E. Lee, J.W. Freeland, Z. Yao, T. T. Fister, J. Vinson, E. L. Shirley, C. Wolverton, V. P. Dravid, M. M. Thackeray, and M. K.Y. Chan, Probing Electrochemically-Induced Oxygen Redox Reactions in Li2IrO3, Under review.