Inhomogeneous degradation of graphite anodes in automotive lithium ion batteries under low-temperature pulse cycling conditions

• Published in: Journal of power sources 2016-03, Vol.307, p.806-814
• Main Authors: Burow, Daniel, Sergeeva, Kseniya, Calles, Simon, Schorb, Klaus, Börger, Alexander, Roth, Christina, Heitjans, Paul
• Format: Article
• Language: English
• Subjects: Charging method; Lithium plating; Lithium-ion battery; Low temperature aging; Post-mortem analysis; State-of-charge distribution
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2016.01.033

The aging of graphite anodes in prismatic lithium ion cells during a low temperature pulse charging regime was studied by electrical tests and post-mortem analysis. The capacity decrease and impedance increase mainly occurs in the beginning of cycling and lithium plating was identified as the major aging mechanism. The degradation and the local states of charge show an inhomogeneous distribution over the anode, which is confirmed from spatially resolved XRD studies and SEM combined with EDX performed on electrode cross sections. Comparing a charged cell with a discharged cell reveals that ca. 1/3 of the lithium is plated reversibly at the given SOH of 60%. It is proposed that high charge rates at low temperatures induce inhomogeneities of temperature and anode utilization resulting in inhomogeneous aging effects that accumulate over lifetime. •Low temperature pulse cycling induces fast aging due to lithium plating.•Charged and discharged anodes are studied.•XRD reveals inhomogeneous intercalation phase distributions.•Plated and intercalated lithium is distributed inhomogeneously over the anode.•Lithium is plated in partly reversible thick surface deposits.