Deciphering the Role of Temperature and Thermal Gradient Magnitude on Li-Ion Battery Performance and Safety

Abstract

Lithium-ion batteries are a transformative technology that have far-reaching implications in applications from consumer electronics to vehicles. The transient environmental conditions of many of these applications combined with internal heat generation and removal from the battery during operation cause it to be subjected to various thermal profiles. It has been shown that the cell’s material properties and kinetics are temperature dependent [1-3] and that thermal gradients can modulate electrochemistry [4, 5]. Our prior studies of externally-applied thermal gradients in batteries found that a gradient of 40 °C across the cell (0 °C anode-side and 40 °C cathode-side) has profound effects on local electrochemistry. However, the sensitivity of the cell to varied local electrode temperatures and the magnitude of the anode-to-cathode thermal gradient remains uncertain. In this work, we decipher the contributions of these two thermal aspects by independently modulating the temperature of each electrode within a single-layer pouch cell. Li-ion full cells are fabricated using lithium-iron-phosphate cathodes and graphite anodes. Local temperature measurements of the electrodes are obtained using thin-film sensors embedded within the cell. Galvanostatic cycling at different current rates and electrochemical impedance spectroscopy are performed on cells with various temperature and thermal gradient magnitudes to quantify thermo-electrochemical coupling phenomena. The implications of the thermal and operating conditions on battery performance and safety are discussed. This work demonstrates the need for effective thermal management strategies that can enable desired operational conditions, such as fast charging, while maintaining safe operation.