Temperature plays an important role in battery aging rate. Previous reports^1-3of commercial batteries with different cathode materials revealed the relationship between aging rate and cycling temperature ( between 25^oC and 70^oC ) can be described by Arrhenius plot. In other words, battery aging rate increases with increasing cycling temperature within range from 25^oC to 70^oC. While most Li-ion batteries suffer significant capacity loss when cycled at elevated temperatures, previous report⁴ has suggested that high temperature abuse testing had nearly no effect on aging rate of commercial 18650 NCA-based batteries, an effect not reported for batteries with LiCoO₂or other common chemistries. We have investigated this effect further and reported that long-term constant current cycle testing of commercial 18650 NCA–based batteries at elevated temperature showed less capacity loss than control testing performed at room temperature, as shown in figure 1. Furthermore, the batteries cycled at room temperature exhibited excessive SEI formation on anode surface whereas there was much less SEI formation in the elevated temperature testing.

Mechanisms such as excessive lithium plating have been put forward as a possible cause⁴, though this would not explain why NCA-based batteries outperform batteries based on other similar cathode chemistries. We will present several possible hypotheses that describe this aging mechanism with a focus on understanding the relationship between SEI formation on the anode and cathode surface chemistry.

Reference:

1. Ramadass, P.; Haran, B.; White, R.; Popov, B. N., Capacity fade of Sony 18650 cells cycled at elevated temperatures Part I. Cycling performance. J Power Sources 2002, 112(2), 606-613.

2. Situ, W. F.; Yang, X. Q.; Li, X. X.; Zhang, G. Q.; Rao, M. M.; Wei, C.; Huang, Z., Effect of high temperature environment on the performance of LiNi0.5Co0.2Mn0.3O2 battery. Int J Heat Mass Tran 2017, 104, 743-748.

3. Waldmann, T.; Wilka, M.; Kasper, M.; Fleischhammer, M.; Wohlfahrt-Mehrens, M., Temperature dependent ageing mechanisms in Lithium-ion batteries - A Post-Mortem study. J Power Sources 2014, 262, 129-135.

4. Waldmann, T.; Kasper, M.; Wohlfahrt-Mehrens, M., Optimization of Charging Strategy by Prevention of Lithium Deposition on Anodes in high-energy Lithium-ion Batteries – Electrochemical Experiments. Electrochim Acta 2015, 178, 525-532.