Li-Ion polymer cells thermal property changes as a function of cycle-life

• Published in: Journal of power sources 2014-10, Vol.263, p.223-230
• Main Authors: Maleki, Hossein, Wang, Hsin, Porter, Wally, Hallmark, Jerry
• Format: Article
• Language: English
• Subjects: Anodes; Applied sciences; Cycles; Direct energy conversion and energy accumulation; Electric potential; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Graphite; High temperature; High voltage Li-Ion polymer cells; High voltages; Si:C Li-Ion polymer cells; Thermal conductivity; Thermal modeling; Thermal properties; Voltage
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2014.04.033

The impact of elevated temperature charge–discharge cycling on thermal conductivity (K-value) of Lithium Ion Polymer (LIP) cells of various chemistries from three different manufacturers was investigated. These included high voltage (Graphite/LiCoO2:3.0–4.35 V), wide voltage (Si:C/LiCoO2:2.7–4.35 V) and conventional (Graphite/LiCoO2:3.0–4.2 V) chemistries. Investigation results show limited variability within the in-plane and through-plane K-values for the fresh cells with graphite-based anodes from all three suppliers. After 500 cycles at 45 °C, in-plane and through-plane K-values of the high voltage cells reduced less vs. those for the wide voltage cells. Such results suggest that high temperature cycling could have a greater impact on thermal properties of Si:C cells than on the LIP cells with graphite (Gr) anode cells we tested. This difference is due to the excess swelling of Si:C-anode based cells vs. Gr-anode cells during cycling, especially at elevated temperatures. Thermal modeling is used to evaluate the impact of K-value changes, due to cycles at 45 °C, on the cells internal heat propagation under internal short circuit condition that leads to localized meltdown of the separator. •45 °C cycling impacts on thermal conductivity (K) of LIP cells were studied.•Extended cycling at 45 °C reduces K-values of all LIP cells.•K-values thought the thickness of the cell reduces more than along the length/width.•In-plane K-values are dominated by the high K-values of current collectors.•Current 4.35 V LIP cells have higher K-values than the past designed 4.2 V cells.