Temperature dependency of state of charge inhomogeneities and their equalization in cylindrical lithium-ion cells

• Published in: Journal of power sources Vol. 329; pp. 546 - 552
• Main Authors: Osswald, P.J., Erhard, S.V., Rheinfeld, A., Rieger, B., Hoster, H.E., Jossen, A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2016
• Subjects: Current density distribution; Lithium-ion battery; Local potential measurements; SOC inhomogeneity; Temperature dependency; Current density distribution; Lithium-ion battery; SOC inhomogeneity; Temperature dependency; Local potential measurements
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2016.08.120

The influence of cell temperature on the current density distribution and accompanying inhomogeneities in state of charge (SOC) during cycling is analyzed in this work. To allow for a detailed insight in the electrochemical behavior of the cell, commercially available 26650 cells were modified to allow for measuring local potentials at four different, nearly equidistant positions along the electrodes. As a follow-up to our previous work investigating local potentials within a cell, we apply this method for studying SOC deviations and their sensitivity to cell temperature. The local potential distribution was studied during constant current discharge operations for various current rates and discharge pulses in order to evoke local inhomogeneities for temperatures ranging from 10 °C to 40 °C. Differences in local potentials were considered for estimating local SOC variations within the electrodes. It could be observed that even low currents such as 0.1C can lead to significant inhomogeneities, whereas a higher cell temperature generally results in more pronounced inhomogeneities. A rapid SOC equilibration can be observed if the variation in the SOC distribution corresponds to a considerable potential difference defined by the open circuit voltage of either the positive or negative electrode. With increasing temperature, accelerated equalization effects can be observed. •Modification of commercial cylindrical cells for individual access to electrode tabs.•Measurement of local potentials under various discharge conditions.•Effect of temperature and current rate on local state of charge distribution.•Analysis of equalization process of local state of charge inhomogeneities.