Electrochemical Impedance Spectroscopy on the Performance Degradation of LiFePO 4 /Graphite Lithium-Ion Battery Due to Charge-Discharge Cycling under Different C-Rates

Yusuke Abe, Natsuki Hori and Seiji Kumagai
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Yusuke Abe: Department of Mathematical Science and Electrical-Electronic-Computer Engineering, Akita University, Tegatagakuen-machi 1-1, Akita 010-8502, Japan
Natsuki Hori: Department of Mathematical Science and Electrical-Electronic-Computer Engineering, Akita University, Tegatagakuen-machi 1-1, Akita 010-8502, Japan
Seiji Kumagai: Department of Mathematical Science and Electrical-Electronic-Computer Engineering, Akita University, Tegatagakuen-machi 1-1, Akita 010-8502, Japan

Energies, 2019, vol. 12, issue 23, 1-14

Abstract: Lithium-ion batteries (LIBs) using a LiFePO 4 cathode and graphite anode were assembled in coin cell form and subjected to 1000 charge-discharge cycles at 1, 2, and 5 C at 25 °C. The performance degradation of the LIB cells under different C-rates was analyzed by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy. The most severe degradation occurred at 2 C while degradation was mitigated at the highest C-rate of 5 C. EIS data of the equivalent circuit model provided information on the changes in the internal resistance. The charge-transfer resistance within all the cells increased after the cycle test, with the cell cycled at 2 C presenting the greatest increment in the charge-transfer resistance. Agglomerates were observed on the graphite anodes of the cells cycled at 2 and 5 C; these were more abundantly produced in the former cell. The lower degradation of the cell cycled at 5 C was attributed to the lowered capacity utilization of the anode. The larger cell voltage drop caused by the increased C-rate reduced the electrode potential variation allocated to the net electrochemical reactions, contributing to the charge-discharge specific capacity of the cells.

Keywords: lithium-ion battery; degradation; capacity fading; electrochemical impedance spectroscopy; LiFePO 4; graphite (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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