A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Algorithm to Determine the Knee Point on Capacity Fade Curves of Lithium-Ion Cells(MDPI, 2019-07-29) Diao, Weiping; Saxena, Saurabh; Han, Bongtae; Pecht, MichaelLithium-ion batteries typically exhibit a transition to a more rapid capacity fade trend when subjected to extended charge–discharge cycles and storage conditions. The identification of the knee point can be valuable to identify the more severe degradation trend, and to provide guidance when scheduling battery replacements and planning secondary uses of the battery. However, a concise and repeatable determination of a knee point has not been documented. This paper provides a definition of the knee point which can be used as a degradation metric, and develops an algorithm to identify it. The algorithm is implemented on various data cases, and the results indicate that the approach provides repeatable knee point identification.Item Development of an Informative Lithium-Ion Battery Datasheet(MDPI, 2021-09-01) Diao, Weiping; Kulkarni, Chetan; Pecht, MichaelLithium-ion battery datasheets, also known as specification sheets, are documents that battery manufacturers provide to define the battery’s function, operational limit, performance, reliability, safety, cautions, prohibitions, and warranty. Product manufacturers and customers rely on the datasheets for battery selection and battery management. However, battery datasheets often have ambiguous and, in many cases, misleading terminology and data. This paper reviews and evaluates the datasheets of 25 different lithium-ion battery types from eleven major battery manufacturers. Issues that customers may face are discussed, and recommendations for developing an informative and valuable datasheet that will help customers procure suitable batteries are presented.Item DEGRADATION ANALYSIS OF LITHIUM-ION BATTERIES WITH KNEE POINTS(2021) Diao, Weiping; Pecht, Michael; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The commercialization of lithium-ion batteries has enabled applications ranging from portable consumer devices to high-power electric vehicles to become commonplace. The capacity, which has been used to determine if lithium-ion batteries have reached the end of life, decreases during usage (cycling) and storage (rest). After some charge-discharge cycles, the capacity fade rate has been observed to increase, and the capacity fade curve visibly bends, the onset of which is described as a knee point. The occurrence of the knee point during the useful life of the battery leads a shorter life than expected based on the initial capacity fade rate. Although various degradation mechanisms are generally known in the literature, the degradation mechanisms responsible for the knee point phenomenon have been in contention. Understanding why and when the knee point will appear on the capacity fade curves is valuable to battery manufacturers and device companies to predict or mitigate the knee point. This study presents the degradation behavior with knee point identification algorithms, experimental analysis that identifies the degradation mechanisms for the knee point, and accelerated aging tests and modeling methods to predict the capacity fade trend, including the knee point. Finally, this study discusses how to delay the knee point from chemical design perspectives and how battery users should qualify batteries