Multi-Electron Reactions Enabled by Anion-Based Redox Chemistry for High-Energy Multivalent Rechargeable Batteries |
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Authors: | Dr. Zhenyou Li Dr. Bhaghavathi P. Vinayan Dr. Piotr Jankowski Dr. Christian Njel Ananyo Roy Prof. Tejs Vegge Dr. Julia Maibach Prof. Juan Maria García Lastra Prof. Maximilian Fichtner Dr. Zhirong Zhao-Karger |
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Affiliation: | 1. Helmholtz Institute Ulm (HIU) Electrochemical Energy Storage, Helmholtzstrasse 11, 89081 Ulm, Germany;2. Department of Energy Conversion and Storage, Technical University of Denmark (DTU), Anker Engelunds Vej, 2800 Kgs. Lyngby, Denmark;3. Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany |
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Abstract: | The development of multivalent metal (such as Mg and Ca) based battery systems is hindered by lack of suitable cathode chemistry that shows reversible multi-electron redox reactions. Cationic redox centres in the classical cathodes can only afford stepwise single-electron transfer, which are not ideal for multivalent-ion storage. The charge imbalance during multivalent ion insertion might lead to an additional kinetic barrier for ion mobility. Therefore, multivalent battery cathodes only exhibit slope-like voltage profiles with insertion/extraction redox of less than one electron. Taking VS4 as a model material, reversible two-electron redox with cationic–anionic contributions is verified in both rechargeable Mg batteries (RMBs) and rechargeable Ca batteries (RCBs). The corresponding cells exhibit high capacities of >300 mAh g−1 at a current density of 100 mA g−1 in both RMBs and RCBs, resulting in a high energy density of >300 Wh kg−1 for RMBs and >500 Wh kg−1 for RCBs. Mechanistic studies reveal a unique redox activity mainly at anionic sulfides moieties and fast Mg2+ ion diffusion kinetics enabled by the soft structure and flexible electron configuration of VS4. |
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Keywords: | anions magnesium-ion batteries multi-electron reactions rechargeable calcium batteries VS4 |
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