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Sodium and Manganese Stoichiometry of P2‐Type Na 2/3 MnO 2
Author(s) -
Kumakura Shinichi,
Tahara Yoshiyuki,
Kubota Kei,
Chihara Kuniko,
Komaba Shinichi
Publication year - 2016
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201606415
Subject(s) - stoichiometry , electrochemistry , redox , manganese , chemistry , aqueous solution , phase (matter) , oxide , inorganic chemistry , ion , crystallography , electrode , organic chemistry
To realize a reversible solid‐state Mn III/IV redox couple in layered oxides, co‐operative Jahn–Teller distortion (CJTD) of six‐coordinate Mn III (t 2g 3 –e g 1 ) 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 Na 2/3 MnO 2 having different Mn stoichiometry, and investigate how the structural and stoichiometric difference influences electrochemical reaction. The distorted Na 2/3 MnO 2 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 Na 2/3 MnO 2 . Furthermore, reversible phase transitions correlated with CJTD are found upon (de)sodiation for distorted Na 2/3 MnO 2 , providing a new insight into utilization of the Mn III/IV redox couple for positive electrodes of Na‐ion batteries.