Fast-charging effects on ageing for energy-optimized automotive LiNi1/3Mn1/3Co1/3O2/graphite prismatic lithium-ion cells

• Published in: Journal of power sources 2019-05, Vol.422, p.175-184
• Main Authors: Mussa, Abdilbari Shifa, Liivat, Anti, Marzano, Fernanda, Klett, Matilda, Philippe, Bertrand, Tengstedt, Carl, Lindbergh, Göran, Edström, Kristina, Lindström, Rakel Wreland, Svens, Pontus
• Format: Article
• Language: English
• Subjects: Ageing; Electric vehicle; Energy battery; Fast charging; Lithium-ion battery
• ISSN: 0378-7753; 1873-2755; 1873-2755
• DOI: 10.1016/j.jpowsour.2019.02.095

The reactions in energy-optimized 25 Ah prismatic NMC/graphite lithium-ion cell, as a function of fast charging (1C4C), are more complex than earlier described. There are no clear charging rate dependent trends but rather different mechanisms dominating at the different charging rates. Ageing processes are faster at 3 and 4C charging. Cycling with 3C-charging results in accelerated lithium plating but the 4C-charging results in extensive gas evolution that contribute significantly to the large cell impedance rise. Graphite exfoliation and accelerated lithium inventory loss point to the graphite electrode as the source of the gas evolution. The results are based on careful post-mortem analyses of electrodes using: scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). SEM results show particle cracking independent of the charging rate used for the cycling. XPS and EIS generally indicate thicker surface film and larger impedance, respectively, towards the edge of the jellyrolls. For the intended application of a battery electric inner-city bus using this type of cell, charging rates of 3C and above are not feasible, considering battery lifetime. However, charging rates of 2C and below are too slow from the point of view of practical charging time. [Display omitted] •Fast charging increased the rate of ageing.•The cell capacity fading is dominated by the lithium-inventory loss.•Gas evolution and lithium plating limit the fast charging capability.•NMC particle cracking observed after long-time cycling at lower charging rates.•Ageing is non-uniform in the cell.