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World Electric Vehicle Journal is published by MDPI from Volume 9 issue 1 (2018). Articles in this Issue were published by The World Electric Vehicle Association (WEVA) and its member the European Association for e-Mobility (AVERE), the Electric Drive Transportation Association (EDTA), and the Electric Vehicle Association of Asia Pacific (EVAAP). They are hosted by MDPI on mdpi.com as a courtesy and upon agreement with AVERE.
Open AccessArticle

Degradation Predictions of Lithium Iron Phosphate Battery

1
Waseda University, 55S-704, 3-4-1 Okubo, Shinjuku-ku, Tokyo, Japan
2
MITSUI ENGINEERING & SHIPBUILDING CO.LTD, 5-6-4 Tsukiji, Chuo-ku, Tokyo, Japan
*
Author to whom correspondence should be addressed.
World Electr. Veh. J. 2015, 7(1), 25-31; https://doi.org/10.3390/wevj7010025
Published: 27 March 2015
PDF [451 KB, uploaded 17 May 2018]

Abstract

Degradation mechanisms of lithium iron phosphate battery have been analyzed with calendar tests and cycle tests. To quantify capacity loss with the life prediction equation, it is seen from the aspect of separating the total capacity loss into calendar capacity and real cycle capacity loss. The real cycle capacity loss of total capacity loss was derived by subtracting the calendar capacity loss parts during cycle tests. It is considered that calendar capacity loss is dominated by SEI formation. On the other hand, real cycle capacity loss includes structure disorder of electrodes and promotion of SEI growth such as delamination and regrowth. Generally, the test results indicated that capacity loss increases under high temperature and SOC condition, and SOC range (ΔSOC) is not related to the loss. However, we founded that the test results under 5℃ condition do not exactly show the same tendency of degradation. As a result, the life prediction equation is based on the chemical kinetics and it can only be adopted only beyond the 15℃ temperature limitation. At this time in life prediction equation, to take ΔSOC into consideration and describe the real cycle capacity loss specifically with amounts of lithium-ion intercalation/deintercalation, the processing amount of current is adopted as the standard of capacity degradation instead of the cycle number. Finally, it is considered to be possible that certain reactions such as further structure disorder or lithium plating caused under low temperature. However, we also founded that DC internal resistance tests results indicated that only calendar capacity loss can apply to chemical kinetics. It is necessary to consider the other construction method of the life prediction equation in the future
Keywords: lithium-ion battery; durability; degradation prediction; lithium iron phosphate battery; BEV (Battery Electric Vehicle) lithium-ion battery; durability; degradation prediction; lithium iron phosphate battery; BEV (Battery Electric Vehicle)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Hato, Y.; Chen, C.H.; Hirota, T.; Kamiya, Y.; Daisho, Y.; Inami, S. Degradation Predictions of Lithium Iron Phosphate Battery. World Electr. Veh. J. 2015, 7, 25-31.

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