Heat Generation Mechanisms of 18650 Lithium-Ion Battery Cells: An in-Depth Analysis

Abstract

Lithium-ion batteries are known for their exceptional properties such as high energy density and long-life cycle, making them popular in various applications, including electric vehicles and energy storage systems. However, the growing concern over the safety of lithium-ion batteries in hot environments with limited cooling has prompted an in-depth analysis of their heat generation mechanisms.To address this concern, it is important to understand the heat generation mechanisms of lithium-ion batteries. In this study, we conducted an in-depth analysis of the heat generation mechanisms of 18650 lithium-ion battery cells. We investigated the impact of temperature on the primary aging mechanisms of the batteries, such as capacity fade and impedance growth. We also studied the thermal behavior of the batteries, including the heat generation and thermal stability.Our analysis involved the disassembly of both fresh and aged 18650 lithium-ion battery cells, followed by a physico-chemical analysis on the electrodes at the microscale level to investigate the chemical and physical changes in the electrodes. We used advanced techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to analyze the cells.Our results showed that high temperatures can accelerate the chemical reactions within the battery, leading to an increase in heat generation. We also found that the aged battery cells had a higher degree of degradation in the electrodes compared to the fresh cells, which affected the battery's overall performance. Our analysis revealed changes in the surface morphology of the electrodes, which could impact the thermal behavior of the battery.During the presentation, I will delve into the specific findings of our analysis of the 18650 lithium-ion battery cells. I will provide a more detailed explanation of the state of health, capacity fade, and impedance growth of the batteries, including how these aging mechanisms were affected by the high temperatures. Additionally, I will discuss the specific changes observed in the electrodes, such as the changes in the surface morphology, and how they impacted the battery's overall performance.Overall, the presentation will provide a comprehensive overview of our study's findings and their significance for the future of lithium-ion batteries in high-temperature environments.