期刊
JOURNAL OF POWER SOURCES
卷 391, 期 -, 页码 106-112出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jpowsour.2018.04.077
关键词
Na-ion battery; Cathode; Surface coating and doping; Cycle stability; Air exposure
资金
- Research Grant Council of Hong Kong [CityU 21202014]
- City University of Hong Kong [7004471]
P2-type Na0.7MnO2, with high capacity and excellent Na ion conductivity, is a promising cathode material for Na-ion batteries. However, its rapid capacity decay upon repeated cycles restricts its practical application. In this study, we demonstrate a facile method to surface coat and dope P2-Na0.7MnO2 with a P2-Na0.7Ni0.33Mn0.67O2 layer in a single step to enhance its cycle stability. The coating suppresses the dissolution of Mn ions into electrolyte, and the Ni dopant suppresses orthorhombic distortion, inhibits Na+ /vacancy ordering and improves structural stability upon cycling. As a consequence, the coating enhances capacity retention from 62.2% (Na0.7MnO2) to 87.7% (Na0.7MnO2/20 wt% Na0.7Ni0.33Mn0.67O2) over 50 cycles, and from 20.7% (Na0.7MnO2) to 68.9% (Na0.7MnO2/20 wt% Na0.7Ni0.33Mn0.67O2) over 100 cycles without sacrificing the initial discharge capacity. In addition, the air-stable Na0.7Ni0.33Mn0.67O2 surface layer protects Na0.7MnO2 against air exposure.
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