Purpose. To experimentally determine the combustion temperature of a lithium-ion battery (LIB) due to mechanical damage to its case by a sharp object. At the same time, to determine the cooling-down time of the lithium-ion battery after combustion and the further mathematical description of this process. Methodology. To achieve the set goal, a laboratory bench with the appropriate measuring equipment was prepared. For mathematical modelling of the cooling process, experimental values and methods for studying heat transfer processes in solid multilayer cylindrical structures were applied. Findings. Experimental studies showed that the maximum temperature on the lithium-ion battery case reached 715 C. In turn, the average values showed a temperature of 665 . The average cooling time to a temperature of 50 C was at least 17 minutes. Mass loss studies showed that after combustion are complete, all elements lose about 53% of their original mass. Originality. The combustion temperature and cooling-down time of Panasonic NCR18650B (LiNi0.8Co0.15Al0.05O2) LIB specifically have been determined for the first time. In parallel with experimental studies, mathematical modelling of the cooling process of the LIB was carried out using the theory of heat transfer. It was found that the results of the mathematical modelling correlate well with the experimental values. This approach allows, in the future, carrying out analytical studies on LIB without the need (where possible) to conduct experiments. Practical value. Further implementation and application of the obtained mathematical model will make it possible to determine the cooling time, the possibility of heating other (adjacent) LIB to a critical temperature, the possibility of ignition from overload, various LIB using only geometric parameters without the need for experimental research. Determining the cooling time of the LIB after combustion is a valuable indicator since it allows one to practically estimate the time during the LIB remains a potential source of danger.

This paper considers the deformation properties of the body of the lithium-ion power cell (LIPC) Panasonic NCR18650B (LiNi0.8Co0.15Al0.05O2) exposed to the action of static load at various techniques of fixing the cell. Determining the properties of LIPCs under appropriate conditions makes it possible to fill the gap in existing studies, which will further ensure the safety of their use. Based on the results of experimental studies, the LIPC rigidity and temperature indicators were determined in accordance with the applied load. The most dangerous variant, from the point of view of fire danger, of applying a static load on the cell has been established. It was experimentally established that, on average, the Panasonic NCR18650B LIPC housing can withstand a load of about 80 kg·s/cm2 (or 7.84 MPa) without further ignition. An increase in pressure force in the range exceeding 85–90 kg·s/cm2 leads to an irreversible chain thermochemical reaction, which, within 2–3 seconds, leads to LIPC ignition. Compressing the LIPC evenly along its lateral surface showed the occurrence of combustion at the load on the cell equal to 150 kg·s/cm2. The average temperature of the cell during combustion caused by the deformation of the housing is 350–450 °C, and the maximum value is registered in the range of 580–680 °C. The mathematical model built on the basis of the mathematical theory of thin shells adequately describes the stressed-strained state of the cylindrical body of cells under the action of a force concentrated and distributed load. The estimation model is satisfactorily verified by experimental results, making it possible to improve the strength and rigidity of LIPC housing by choosing the appropriate steel grade for its body, the geometric dimensions, and the structural technique of its fastening.

Panasonic NCR18650B (LiNi0.8Co0.15Al0.05O2) lithium-ion power cell (LIPC) and its performance after exposure to excess direct current are considered in this paper. The basic fire hazard indicators (element ignition temperature, flame temperature, element heating time, etc.) were experimentally established and mathematically confirmed for the examined LIPC. According to the results of experimental studies, the time of occurrence of an irreversible thermochemical reaction in a lithium-ion power cell was determined depending on the different DC current strengths. Additionally, the critical temperature of the onset of an irreversible thermochemical reaction and the total combustion temperature of the element have been established. The application of the Joule-Lenz and Fourier laws allowed for a mathematical notation of the dependence (influence) of DC strength over time and the heating of the element to a critical temperature. The heating time of Panasonic NCR18650B LIPC (LiNi0.8Co0.15Al0.05O2) to a critical temperature of 100–150 °C under the influence of excess current was experimentally established and mathematically confirmed. The determined critical indicators of the element (temperature, time, etc.) make it possible to further devise a number of necessary regulatory documents that will allow them to be certified, tested, and, in general, to better understand the dangers that they may pose. A mathematical model was built, which, taking into account the geometrical parameters of the element, makes it possible to calculate the onset of the critical temperature of such elements with excellent geometric parameters without conducting experimental studies