The Effect of Low-Temperature Exposures on LFP/Graphite Li-Ion Batteries

Li-ion batteries (LIBs) are at the forefront of modern-day sustainable energy storage solutions, with an ever-increasing interest in lithium iron phosphate (LFP) cathodes. With a growing need for energy storage solutions at extreme temperature conditions (e.g., space and electric vehicle applications), which are known to have detrimental effects on battery performance [1–2], mechanistically determining the low-temperature effects on these battery systems is of utmost necessity. Recent studies indicate that storing NMC-based LIBs at low temperatures can lead to electrode degradation and hence, reduced performance under normal temperatures [3]. Moreover, our previous studies reveal that numerous freeze-thaw cycles on NMC-based LIBs typically results in reduced performance due to electrode degradation and other detrimental effects on the electrolyte. However, the effects of low-temperature exposure on LFP-based LIBs are currently not well understood. In this work, we investigate these effects using single-layer LFP/Gr pouch cells. These cells are thermally cycled using controlled heating and cooling rates between 25°C and -60°C. Galvanostatic cycling and electrochemical impedance spectroscopy are performed between the thermal cycles to quantify the electrochemical performance and the effects of the low-temperature exposures. Overall, the cells exhibit increased capacity fade, polarization, and interface resistance, even with a relatively low number of thermal cycles. Post-mortem analysis (e.g., X-ray diffraction and scanning electron microscopy) is then performed to further assess the underlying mechanisms. Acknowledgments The authors gratefully acknowledge the NASA Established Program to Stimulate Competitive Research (EPSCoR) Program for funding this research (NASA Grant Number 80NSSC23M0068). The authors also acknowledge Dr. William West and Dr. Marshall Smart (NASA Jet Propulsion Laboratory) for technical discussion of this work and Dr. Sara Nelson, Ms. Hailey Waller, and Ms. Alesha Roll (Iowa NASA EPSCoR) for administrative services. References [1] Li Q, Jiao S, Luo L, Ding MS, Zheng J, Cartmell SS, et al. Wide-Temperature Electrolytes for Lithium-Ion Batteries. ACS Appl Mater Interfaces 2017;9:18826–35. https://doi.org/10.1021/acsami.7b04099. [2] Ng B, Coman PT, Faegh E, Peng X, Karakalos SG, Jin X, et al. Low-Temperature Lithium Plating/Corrosion Hazard in Lithium-Ion Batteries: Electrode Rippling, Variable States of Charge, and Thermal and Nonthermal Runaway. ACS Appl Energy Mater 2020;3:3653–64. https://doi.org/10.1021/acsaem.0c00130. [3] Li J, Li S, Zhang Y, Yang Y, Russi S, Qian G, et al. Multiphase, Multiscale Chemomechanics at Extreme Low Temperatures: Battery Electrodes for Operation in a Wide Temperature Range. Adv Energy Mater 2021;11. https://doi.org/10.1002/aenm.202102122.