Thermal characterization of lithium-ion batteries under fast charging conditions using infrared imaging.

Lithium-ion batteries are widely used across various industries due to their long lifespan, high energy density, low self-discharge rate, and absence of memory effect. However, fast charging of Li-ion batteries can cause problems like lithium plating, mechanical damage, and overheating. Temperature plays a key role in battery performance. Measuring temperature accurately is important to improve battery life, efficiency, and safety. However, accurately measuring a battery's internal temperature remains challenging, and the appropriate measurement method depends on factors like range, accuracy, resolution, and cost. Choosing the right temperature measurement method depends on range, accuracy, resolution, and cost. In this study, we developed a custom-designed lithium-ion battery cell to closely monitor thermal and electrochemical behaviors under controlled testing conditions. Using both infrared (IR) and optical cameras simultaneously, we captured thermal and visual images that revealed detailed variations in electrolyte temperature and lithiation effects across different C-rates. Our results show that higher C rates significantly influence the lithiation process and accelerate the onset of lithium plating. We directly extracted electrolyte temperature from thermal images and calculated current density using thermal modeling. This integrated approach provided reliable temperature measurements and unveiled spatial thermal heterogeneity during fast charging. Our study introduces an imaging-based approach to evaluate electrochemical and thermal behavior, while also identifying key factors responsible for heat generation in a custom battery cell under different C rates.