Lithium-ion batteries (LIBs) are the dominant energy storage technology for portable electronics and electric vehicles. However, their widespread use raises concerns about safety, particularly the risk of fire hazards. These hazards can stem from thermal runaway effects within the cell, making it highly relevant to understand heat generation at the micrometer scale inside batteries.¹

To study heat generation, we apply luminescence thermometry during galvanostatic cycling in a model battery system of TiS₂/Li-metal/1M LiPF₆ in EC/DMC with a inverted fluorescence microscopy set-up. To access the anode, cathode, and electrolyte with an optical microscope, we use a specialized cell with an optical window for characterization. This setup allows us to track local temperature fluctuations and gradients on the micrometer scale by analyzing the luminescence of embedded microcrystals.² These thermal data are correlated with physical changes observed via optical microscopy.

¹ G. Yasin, M. Arif, T. Mehtab, X. Lu, D. Yu, N. Muhammad, M. Tariq Nazir, H. Song, Energy Storage Mater. 2020, 25, 644

² T. P. v an Swieten, T. Van Omme, D. J. van den Heuvel, S. J. W. Vonk, R. G. Spruit, F. Meirer, H.   H. P. Garza, B. M. Weckhuysen, A. Meijerink, F. T. Rabouw, ACS Appl. nano Mater. 2021, 4, 4208.

Jur de Wit is a postdoc in the Materials Chemistry and Catalysis group of the Debye Institute at Utrecht University. Jur earned his PhD from UU (2024), focusing on luminescent materials for lighting and display applications. His research now focuses on applying the tool of luminescence thermometry to study heat generation inside Li-ion batteries and is a part of the BatteryNL consortium.