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Native Vacancy Enhanced Oxygen Redox Reversibility and Structural Robustness
Author(s) -
Li Yejing,
Wang Xuefeng,
Gao Yurui,
Zhang Qinghua,
Tan Guoqiang,
Kong Qingyu,
Bak Seongmin,
Lu Gang,
Yang XiaoQing,
Gu Lin,
Lu Jun,
Amine Khalil,
Wang Zhaoxiang,
Chen Liquan
Publication year - 2019
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201803087
Subject(s) - redox , materials science , cathode , manganese , density functional theory , vacancy defect , synchrotron , oxygen , ion , chemical physics , x ray photoelectron spectroscopy , chemical engineering , chemistry , crystallography , computational chemistry , physics , organic chemistry , metallurgy , engineering , nuclear physics
Cathode materials with high energy density, long cycle life, and low cost are of top priority for energy storage systems. The Li‐rich transition metal (TM) oxides achieve high specific capacities by redox reactions of both the TM and oxygen ions. However, the poor reversible redox reaction of the anions results in severe fading of the cycling performance. Herein, the vacancy‐containing Na 4/7 [Mn 6/7 (◻ Mn ) 1/7 ]O 2 (◻ Mn for vacancies in the MnO slab) is presented as a novel cathode material for Na‐ion batteries. The presence of native vacancies endows this material with attractive properties including high structural flexibility and stability upon Na‐ion extraction and insertion and high reversibility of oxygen redox reaction. Synchrotron X‐ray absorption near edge structure and X‐ray photoelectron spectroscopy studies demonstrate that the charge compensation is dominated by the oxygen redox reaction and Mn 3+ /Mn 4+ redox reaction separately. In situ synchrotron X‐ray diffraction exhibits its zero‐strain feature during the cycling. Density functional theory calculations further deepen the understanding of the charge compensation by oxygen and manganese redox reactions and the immobility of the Mn ions in the material. These findings provide new ideas on searching for and designing materials with high capacity and high structural stability for novel energy storage systems.