Computational Perspective of Manganese Cathodes for Aqueous Batteries

Manganese oxide polymophs are promising class of materials for bifunctional OER/ORR applications, metal-ion cathodes as well as very promising cathodes for application in Aqueous Battery (AB). In my talk, I will discuss how theory can contribute to understanding of the electrochemical/water electrolyte stability, catalysis, anionic redox as well as deposition/stripping reversibility and pH effects in these systems. In the first highlight, our theory provides detailed ion-insertion energetics of MnO2 polymorphs studied in water electrolytes from Pourbaix perspective [1]. Later on, we select only the alpha-MnO2, which has significantly improved bifunctional OER/ORR performance at higher alkaline pH [2]. We show that using a grand canonical DFT model, that the adsorption strengths of key OER/ORR intermediates are pH-dependent, leading to non-Nernstian shifts in onset potential. Tuning intermediate adsorption strengths via electrolyte pH offers a way to circumvent adsorbate scaling relations and achieve higher activity. Next, we investigate the role of anionic redox on the capacity of the selenium-doped Na 0.6 Li 0.2 Mn 0.8 O 2 and show that Se stabilizes this system via redox to Se +4/5 which increases the energy barrier step for O─O dimerization [3]. Finally, we discuss how surface effects in the Zn/MnO2 system control the deposition/stripping reversibility for Aqueous Battery applications [4]. In the experimental work led by Yi Cui (Stanford), we show that introduction of surfactant molecules leads to surface templating affecting both Zn and MnO2. This work is supported by the Aqueous Battery Consortium, an energy innovation hub under the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering. [1] Carlson, E. Z.; Chueh, W. C.; Mefford, J. T.; Bajdich, M. Selectivity of Electrochemical Ion Insertion into Manganese Dioxide Polymorphs. ACS Appl. Mater. Interfaces 2023 , 15 (1), 1513–1524. 10.1021/acsami.2c16589. [2] Carlson, E. Z.; Masalkovaite; Jaeheon Lee, Md Delowar Hossain, Xiao Zhao, Paul McIntyre, Bryan D. McCloskey, Hendrik Ohldag, Chueh, W. C, Bajdich, M. Mefford, J. T.; pH Dependence of Bifunctional Oxygen Electrocatalysis (in preparation) [3] Xue, Z.; Bothra, N.; Meng, D.; Feng, G.; Li, Y.; Cui, T.; Hao, H.; Lee, S.-J.; Liu, Y.; Bajdich, M.; Nanda, J.; Zheng, X. Coupling Anionic Oxygen Redox with Selenium for Stable High-Voltage Sodium Layered Oxide Cathodes. Advanced Functional Materials 2025 , 35 (13), 2417758.10.1002/adfm.202417758. [4] Li, Y.; Zheng, X.; Carlson, E. Z.; Xiao, X.; Chi, X.; Cui, Y.; Greenburg, L. C.; Zhang, G.; Zhang, E.; Liu, C.; Yang, Y.; Kim, M. S.; Feng, G.; Zhang, P.; Su, H.; Guan, X.; Zhou, J.; Wu, Y.; Xue, Z.; Li, W.; Bajdich, M.; Cui, Y. In Situ Formation of Liquid Crystal Interphase in Electrolytes with Soft Templating Effects for Aqueous Dual-Electrode-Free Batteries. Nat Energy 2024 , 9 (11), 1350–1359. 10.1038/s41560-024-01638-z.