Bin Xu1,2, Weiping Diao2, Guangrui Wen1, Choe Song-Yul3, Jonghoon Kim4 and Michael Pecht2
1School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi, 710049, China
2 Center for Advanced Life Cycle Engineering, University of Maryland, Maryland, USA
3Department of Mechanical Engineering, Samuel Ginn College of Engineering, Auburn University, Auburn, AL, 36849, USA
4Energy Storage Conversion Laboratory, Department of Electrical Engineering, Chungnam National University, Daejeon, 34134, South Korea
In battery-powered electronic devices, an increase in the discharge C-rate is expected when using functions that require more power. Temperature rise is the thermal effect of discharge C-rate due to ohmic heating, causing lithium-ion batteries to degrade faster. There are also non-thermal effects, such as increased mechanical stress on electrode particles and structure. How much each of the thermal and non-thermal effects contributes to the capacity fade is valuable for understanding the discharge C-rate-related degradation mechanisms in lithium-ion batteries. This paper decouples the thermal and non-thermal effects of discharge C-rate on the capacity fade of lithium-ion batteries. Pouch cells are subject to continuous charge-discharge cycling under six testing conditions. Two stress factors are investigated: discharge C-rate (0.5C, 1.75C, and 3C) and temperature control (constant battery surface temperature at 45oC and constant ambient temperature at 45oC). The capacity degradation mechanisms associated with thermal and non-thermal effects of discharge C-rate is revealed using cycling data, impedance measurement, incremental capacity analysis, and scanning electron microscopy/energy dispersive X-ray spectroscopy analysis. A capacity fade model is developed as the function of discharge C-rate and cycle numbers. The contributions of the thermal and non-thermal effects at different discharge C-rates on the capacity loss are quantified.