Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150647

150647 - Operando Monitoring and Analytics of Internal Temperature Dynamics in Li-Ion Batteries 

Lithium-ion (Li-ion) batteries are the cornerstone of modern electronics, electric vehicles, and renewable energy systems, particularly as the energy paradigm shifts towards sustainability. These batteries are esteemed for their superior energy density, minimal self-discharge, and prolonged cycle life. However, challenges related to suboptimal thermal management, safety, and performance degradation under extreme operating conditions must be addressed to broaden their application. The state-of-the-art battery thermal management systems (BTMS) rely on external temperature sensors to regulate internal temperatures. These external measurements do not accurately reflect the actual core temperatures of the cells due to rapid temperature variations and poor thermal conductivity of cell components. This research focuses on the operando monitoring of internal temperatures during the cycling of Li-ion cells at various operating temperatures and current rates (C-rates). Core temperatures were measured experimentally by integrating temperature sensors into 5 Ah pouch cells that underwent cycling in varying thermal environments and C-rates. The results revealed that cell internal temperatures increased non-linearly during cycling, with discharge temperatures (both internal and external) being higher than during charge. Cell temperatures also rose consistently throughout cycling, with an increasing disparity between internal and external measurements. Low-temperature operations (0°C) caused internal temperatures to surge as high as 29°C, with a 9°C disparity in internal/external temperatures, and demonstrated the highest capacity degradation, primarily due to Li plating. Nominal operations at 30°C displayed the second-highest temperature increases while achieving the best capacity retention. High-temperature operations at 60°C generated the least heat, showing comparatively low temperature rises due to improved kinetics. However, this scenario exhibited higher capacity fade than nominal conditions, indicating degradation due to solid electrolyte interphase (SEI) growth.

Informed by experiments, a physics-based thermo-electrochemical model was employed to elucidate the intrinsic mechanisms leading to temperature differences and cell degradation. The coupled model quantified three primary modes of heat generation (kinetic, reversible, and ohmic) and heat dissipation from specific cell layers. These mechanisms collectively drive the significant temperature differences observed between the external and internal layers. The model delineated that total heat generation from the three modes is higher during discharge and for the low-temperature and higher C-rate conditions, corroborating experimental results. The model also captures the evolution of Li plating and SEI growth in the anode and quantifies the cell capacity losses at various operating conditions. It was conclusively demonstrated that lithium plating predominantly drives degradation at low temperatures, whereas SEI growth is the principal degradation mechanism at high temperatures. By coupling experimental setups with computational modeling, this study provides valuable insights into internal temperature non-linearity under various cycling conditions and the effect of inter-electrode thermal gradients on heterogeneous cell degradation. The findings underscore the importance of real-time internal temperature as a key descriptor for cell degradation and safety, offering critical insights to advance the BMTS in Li-ion batteries.

Presenting Author: Anuththara Alujjage Purdue University

Presenting Author Biography: Anuththara Alujjage is a third-year PhD student under the mentorship of Dr. Partha Mukherjee at Purdue University. She earned her Bachelor's degree in Mechanical Engineering from Northern Arizona University (NAU) before joining Dr. Mukherjee's lab as a direct Ph.D. student. Anuththara's research focuses on thermo-electrochemical analytics of Li-ion cells. She is dedicated to developing both invasive and non-invasive sensing techniques to elucidate intrinsic thermal dynamics. By coupling electrochemical mechanisms, her work aims to uncover the impact of true core temperatures and thermal gradients on cell degradation, safety, and performance, contributing to the advancement of battery technology.
She was the first recipient of the Udea Collaborative Research Grant, awarded to encourage interdisciplinary projects between undergraduate students at NAU. She also won the First Place Award for this collaborative work in the University Virtual Symposium. Anuththara recently presented her work at the 245th Electrochemical Society conference, where she was awarded a travel grant. She has several research publications under review and hopes her work will advance the field of battery thermal management systems (BTMS).

Authors:

Anuththara Alujjage Purdue University
Avijit Karmakar Purdue University
Bairav Vishnugopi Purdue University
Partha Mukherjee Purdue University