Sodium and Manganese Stoichiometry of P2‐Type Na2/3MnO2 |
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| Authors: | Shinichi Kumakura Yoshiyuki Tahara Dr Kei Kubota Kuniko Chihara Prof Shinichi Komaba |
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| Institution: | 1. Department of Applied Chemistry, Tokyo University of Science, Tokyo, Japan;2. Umicore Japan KK, Tokyo, Japan;3. Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, Kyoto, Japan |
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| Abstract: | To realize a reversible solid‐state MnIII/IV redox couple in layered oxides, co‐operative Jahn–Teller distortion (CJTD) of six‐coordinate MnIII (t2g3–eg1) is a key factor in terms of structural and physical properties. We develop a single‐phase synthesis route for two polymorphs, namely distorted and undistorted P2‐type Na2/3MnO2 having different Mn stoichiometry, and investigate how the structural and stoichiometric difference influences electrochemical reaction. The distorted Na2/3MnO2 delivers 216 mAh g?1 as a 3 V class positive electrode, reaching 590 Wh (kg oxide)?1 with excellent cycle stability in a non‐aqueous Na cell and demonstrates better electrochemical behavior compared to undistorted Na2/3MnO2. Furthermore, reversible phase transitions correlated with CJTD are found upon (de)sodiation for distorted Na2/3MnO2, providing a new insight into utilization of the MnIII/IV redox couple for positive electrodes of Na‐ion batteries. |
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| Keywords: | Jahn– Teller distortion layered compounds polymorphism positive electrode materials sodium-ion batteries |
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