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Electrochemical Impedance Spectroscopy on the Performance Degradation of LiFePO4/Graphite Lithium-Ion Battery Due to Charge-Discharge Cycling under Different C-Rates

Department of Mathematical Science and Electrical-Electronic-Computer Engineering, Akita University, Tegatagakuen-machi 1-1, Akita 010-8502, Japan
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Energies 2019, 12(23), 4507; https://doi.org/10.3390/en12234507
Received: 21 October 2019 / Revised: 18 November 2019 / Accepted: 23 November 2019 / Published: 27 November 2019
(This article belongs to the Special Issue Testing and Management of Lithium-Ion Batteries)
Lithium-ion batteries (LIBs) using a LiFePO4 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. View Full-Text
Keywords: lithium-ion battery; degradation; capacity fading; electrochemical impedance spectroscopy; LiFePO4; graphite lithium-ion battery; degradation; capacity fading; electrochemical impedance spectroscopy; LiFePO4; graphite
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MDPI and ACS Style

Abe, Y.; Hori, N.; Kumagai, S. Electrochemical Impedance Spectroscopy on the Performance Degradation of LiFePO4/Graphite Lithium-Ion Battery Due to Charge-Discharge Cycling under Different C-Rates. Energies 2019, 12, 4507.

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