Safety Evaluation of All-Solid-State Batteries: An Innovative Methodology Using In Situ Synchrotron X-ray Radiography

All-solid-state batteries (ASSBs) are expected to be a relevant solution to increase the energy density in lithium-ion battery (LiB) technology. However, the energy management requires high-energy storage capacities, which make the safety a crucial issue. Unfortunately, it is difficult so far to assess the safety of nonfully mature battery technologies. In this paper, we describe a methodology to study the thermal runaway of a wide range of ASSB technologies. We specifically designed a closed calorimeter to be used in operando experiments with high-speed synchrotron X-ray radiography for the validation of the principle. Electrodes removed from LiB at 100% state of charge have been reassembled in ASSB, with an LLZO (lithium lanthanum zirconium niobium oxide) electrolyte. For the first time, we were able to observe and compare the thermal runaway of ASSB and liquid electrolyte (LiB) using this methodology. An 11% decrease of heat release was measured in comparison with LiB during the thermal runaway. Such a methodology can assist in the development of future battery technologies, by evaluating battery safety from the start of the design to battery composition to cell shape.