期刊
ELECTROCHIMICA ACTA
卷 176, 期 -, 页码 270-279出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.electacta.2015.06.096
关键词
Lithium iron phosphate; Graphite; Deterioration; Cycling performance; High-rate discharge
资金
- Suzhou (Wujiang) Automotive Research Institute, Tsinghua University [2012 WJ-A01]
- National Key Basic Research Program of China [2014CB932400]
- National Natural Science Foundation of China [51232005]
- Key Project for Basic Research for three main areas of Shenzhen [JC201104210152A]
- Guangdong Province Innovation R&D Team Plan for Energy and Environmental Materials [2009010025]
- National Science and Technology Support Program [2015BAG01B01]
In this study, the deterioration of lithium iron phosphate (LiFePO4) /graphite batteries during cycling at different discharge rates and temperatures is examined, and the degradation under high-rate discharge (10C) cycling is extensively investigated using full batteries combining with post-mortem analysis. The results show that high discharge current results in an instability of electrode/electrolyte interface and unstable solid electrolyte interphase (SEI) layers are expected to form on the newly exposed graphite anode surface, which cause sustainable consumption of active lithium and further lead to the performance degradation of active materials. For LiFePO4 cathode, the initial capacity is largely recovered under low rate (0.1-0.2C), whereas a decline in the capability is observed at higher rates (0.5-3.0C). For graphite anode, half-cell study shows that considerable capacity loss occurs even at low rates. A small amount of Fe deposition is observed on graphite anode after cycling under 10C discharge at 55 degrees C. X-ray photoelectron spectroscopy (XPS) analysis confirms that a layer composed of lithium compounds is formed on the surface of anode, which can not participate in the reversible electrochemical reaction again. In addition, electrochemical impedance spectrum (EIS) measurements of half-cell indicate that the increased resistance of the positive electrode is suggested to be the root cause of power fading under high-rate discharge cycling, especially at high temperature. (C) 2015 Published by Elsevier Ltd.
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