期刊
ACS MATERIALS LETTERS
卷 1, 期 5, 页码 573-581出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsmaterialslett.9b00347
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资金
- Virginia Tech Department of Chemistry Startup Funds, 4-VA Collaborative Research
- National Science Foundation [CBET-1912885]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-76SF00515]
- DOE Office of Science [DE-AC02-06CH11357]
- National Natural Science Foundation of China [11805034, 21704105]
- Natural Science Foundation of Guangdong Province [2017A030313021]
Developing stable cathode materials represents a crucial step toward long-life sodium-ion batteries. P2-type layered oxides are important as cathodes for their reversibility, but their long-term performance in full cells remains a key challenge. Herein, we report Na0.75Co0.125Cu0.125Fe0.125Ni0.125Mn0.5O2 with an intergrowth of ordered P2 and P3 phases, studied by neutron diffraction and Rietveld refinement. A stable electrochemical performance is achieved in Na half cells with 100% capacity retention at a rate of C/10 after 100 cycles (initial capacity of 90 mAh/g), 96% capacity retention at a rate of 1 C after 500 cycles (initial capacity of 70 mAh/g), and 85% capacity retention at a rate of 5 C after 1000 cycles (initial capacity of 55 mAh/g). Stable full cell performance is achieved with 84.2% capacity retention after 1000 cycles at a rate of 1 C. Synchrotron X-ray diffraction, spectroscopy, and imaging are applied to elucidate the relationship between chemical/structural evolution and battery performance. A reversible local and global structural evolution is observed during initial cycles. Meanwhile, the challenges with enabling prolonged cycling (beyond 1000 cycles) may be associated with Fe dissolution and formation of a copper oxide phase. This study implies that cathodes with complex chemical and structural formations may stabilize electrochemical performance and highlights the importance of decoupling the contribution of each transition metal to performance degradation.
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