In the past few years, several lithium-ion (Li-ion) technologies have been studied and developed for its use in electric vehicles (EVs). Among these, Lithium Iron Phosphate (LFP) batteries have become a viable choice due to its key features, such as superior intrinsic safety or very large cycle life. As a result of its advantages and the projected impact on the EV market, further studies and tests have to be carried out in order to obtain EVs battery crucial information, such as cycle life, cell safety, reliability or capacity degradation, to name a few. With this aims in mind, this paper presents the results of extensive battery testing procedures conducted on commercial high power LFP cells. A series of relevant combined cycling schemes, which varied from stressful cycling to mixed cycling protocols were carried out for over 5,000 full charge and discharge cycles. Evaluation on important cell parameters such as capacity degradation, cycle life, energy efficiency or cell temperature were performed and then compared with various requirements and targets defined by the United States Advanced Battery Consortium (USABC). In this study, two high power commercial 2.3 Ah LFP cells were tested and evaluated under a series of stressful-cycling testing procedures. The cells succesfully achieved important USABC long-term goals and exhibited an overall good performance, after more than 5,700 cycles in total. The evaluation results showed that the tested cells are safe and can support fast charge/discharge rates without any significant damage for the cycling life. Even though, final cost and specific energy need to be improved for practical and cost-effective EV applications. Stressful, and mixed-cycle tests in particular, revealed a complicated capacity retention, which is rate and history-dependent. Therefore, reference tests are useful to evaluate the real capacity available on the cell. The design of appropiate battery testing procedures is essential in order to understand and evaluate the tested-cell behaviour more accurately. Hence, further development and improvements are needed to effectively simmulate and predict the tested-battery performance and capacity fade.
Evaluation of lithium iron phosphate batteries for electric vehicle under stressful cycling
EVS, Electric Vehicle Symposium, 26 ; 150-161
2012
12 Seiten, 16 Bilder, 3 Tabellen, 24 Quellen
Aufsatz (Konferenz)
Englisch
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