Li-ion batteries play an ever-increasing role in our daily life. Therefore, it is important to understand the potential risks involved with these devices. In this work we demonstrate the thermal runaway characteristics of three types of commercially available Li-ion batteries with the format 18650. The Li-ion batteries were deliberately driven into thermal runaway by overheating under controlled conditions. Cell temperatures up to 850 °C and a gas release of up to 0.27 mol were measured. The main gas components were quantified with gas-chromatography. The safety of Li-ion batteries is determined by their composition, size, energy content, design and quality. This work investigated the influence of different cathode-material chemistry on the safety of commercial graphite-based 18650 cells. The active cathode materials of the three tested cell types were (a) LiFePO₄, (b) Li(Ni_0.45Mn_0.45Co_0.10)O₂ and (c) a blend of LiCoO₂ and Li(Ni_0.50Mn_0.25Co_0.25)O₂.

Thermal runaway characteristics of two types of commercially available 18650 cells, based on Li_xFePO₄ and Li_x (Ni_0.80Co_0.15Al_0.05)O₂ were investigated in detail. The cells were preconditioned to state of charge (SOC) values in the range of 0% to 143%; this ensured that the working SOC window as well as overcharge conditions were covered in the experiments. Subsequently a series of temperature-ramp tests was performed with the preconditioned cells. Charged cells went into a thermal runaway, when heated above a critical temperature. The following thermal runaway parameters are provided for each experiment with the two cell types: temperature of a first detected exothermic reaction, maximum cell temperature, amount of produced ventgas and the composition of the ventgas. The dependence of those parameters with respect to the SOC is presented and a model of the major reactions during the thermal runaway is made.

Damaged or heavily over-heated Li-ion batteries in electric vehicles can transit into a thermal runaway reaction with further heat and gas release.

We use a photoreactive interfacial layer of poly(endo,exo-bis(2-nitrobenzyl) bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate) (PBHND) between the gate dielectric and the pentacene active layer to tune the effective hole mobility in organic thin film transistors over approximately one order of magnitude. This can be explained by the photoconversion of the PBHND layer changing its surface energy and thus strongly impacting pentacene growth. A linear relationship between the mobility and the grain size is observed.

Lithium-Ion battery cells and automotive battery systems are constantly improving as a result of the rising popularity of electric vehicles. With higher energy densities of the cells, the risks in case of failure rise as well. In the worst case, a fast exothermic reaction known as thermal runaway can occur. During thermal runaway, the cell can emit around 66% of its mass as gas and particles. An experimental setup was designed and showed that the gas-particle-vent of a cell going through thermal runaway can cause electric breakthroughs. These breakthroughs could start electric arcing in the battery system, which could lead to additional damages such as burning through the casing or igniting the vent gas, making the damage more severe and difficult to control. Uncontrollable battery fires must be prevented. The emitted gas was analyzed and the ejected particles were examined to discuss the potential causes of the breakthroughs.

Understanding thermal runaway (TR) is essential for ensuring the safety of battery systems, particular with regard to released energy and vented materials. To design an effective system, it is crucial to separately account for the increase in internal energy within the cell body, as well as the energy associated with particles and gases. This study introduces a novel experimental approach to analyze the energy balance of a TR event in a prismatic 156 Ah lithium-ion cell. The total internal energy increase was quantified and divided into energy retained in the cell and energy released via venting. For the first time, the latter was further resolved into contributions from solid particles and gases using a calorimeter combined with a custom cyclone separator in an autoclave. Results show an energy increase of 2.5 MJ–2.8 MJ, with 31%–40% retained in the cell and 60%–69% discharged via venting components. 55%–63% could be assigned to particles. Considering the mass fraction reveals that the particles exhibit a higher energy release capacity relative to the remaining cell body. These findings help to derive the energy transport through venting components and provide data for the validation of TR simulation models to assess the impact of TR on system level.