Early-Stage Battery Safety Evaluation by Quantitative Analysis of Reaction Thermochemistry Using Calorimetry Measurements

Early-stage battery chemistry work typically focuses on demonstrating performance at the materials, coin, and pouch cell level, with evaluation and design for safety left for later stages.¹ In this work, we will describe the opportunities for assessing the safety of a battery chemistry at the earliest stages of its development using Differential Scanning Calorimetry (DSC) experiments, as soon as the active materials and electrolyte have been identified.<br/>We use DSC samples comprising of Anode-Cathode-Electrolyte (ACE), requiring only tens of milligrams of materials. Measuring and analyzing heat flow from ACE samples is challenging and has not been performed extensively in the past despite its clear advantages. This is because it involves overlapping exotherms over a wide temperature range from gas driven crosstalk reactions and interfacial reactions between the cathode, electrolyte and anode components making careful measurement and analysis difficult. We have demonstrated the value of this approach for a Li_xCoO₂+C+PVDF cathode sheet /LLZO/Li metal material set, where we identified the previously under-appreciated role of the cathode sheet conductive additive and binder in the reaction pathways upon heating to 500°C in a DSC pan.² In this work, we will discuss the insights from DSC heat flow measurements on ACE samples from various chemistries including high-Ni cathodes that are commercially relevant for electric vehicle applications, sulfide electrolytes, liquid electrolytes with graphite and lithium metal anodes. We will also present the DSC methodology required to obtain accurate measurements on milligram-scale samples, emphasizing the sample preparation and DSC methods needed to obtain accurate, repeatable results. Approaches associated with DSC baselining and integration methods will also be presented.<br/><br/>References:<br/>1. Bates, A. M., Preger, Y., Torres-Castro, L., Harrison, K. L., Harris, S. J., & Hewson, J. (2022). Are solid-state batteries safer than lithium-ion batteries?. <i>Joule</i>, <i>6</i>(4), 742-755.<br/>2. Johnson, N. B., Bhargava, B., Chang, J., Zaman, S., Schubert, W., & Albertus, P. (2023). Assessing the Thermal Safety of a Li Metal Solid-State Battery Material Set Using Differential Scanning Calorimetry. <i>ACS Applied Materials & Interfaces</i>, <i>15</i>(49), 57134-57143.