The safety of lithium-ion batteries is directly related to the increase in the internal temperature of the battery, because the increase in battery temperature causes the activation and occurrence of undesirable side reactions inside the battery and ultimately leads to the phenomenon of thermal runaway. This phenomenon is a sharp and uncontrollable increase in the temperature of the battery due to exothermic reactions inside the fluid. In general, this phenomenon has several phases: the first phase, also called the initial heating phase of the battery or external heating, is in the temperature range of 90-120 °C. In this temperature range, the destruction of the solid electrolyte interface (SEI) layer occurs, which leads to further oxidation of the electrolyte on the anode surface and the regrowth of this layer. The second phase, from 120 °C onwards, is the beginning of the range in which the internal exothermic reactions of the battery begin to occur. As a result of these reactions and the increase in battery temperature above 130 °C, the separator begins to melt, and with an increase in temperature to 180 °C, the separator completely loses its function. The third phase is subsequently accompanied by an increase in temperature and decomposition of the cathode structure, which leads to the onset of the thermal runaway phenomenon. Also, in this phase, when the temperature reaches above 200 °C, the decomposition of the electrolyte also occurs. The simultaneous occurrence of the two phenomena of cathode and electrolyte decomposition leads to a sharp temperature increase and the occurrence of the thermal runaway phenomenon. The temperature at which thermal runaway begins for different cathodes is somewhat different. This temperature is around 150, 210: NMC for LCO and NCA cathodes and 270 °C for LFP. The noteworthy point here is that the thermal runaway process begins with the anode and separator, and if the internal temperature of the battery increases to such an extent that the conditions for internal exothermic reactions are provided (>120 °C), it is almost impossible to avoid the thermal runaway phenomenon for all cathodes because the heat from the side reactions of the initial stages ultimately makes this phenomenon possible. Another important issue regarding thermal runaway of different cathode materials is the amount of gases produced during this phenomenon. Investigating these gases in terms of toxicity and intensity of explosion is a matter worth considering. Scientific studies show that in thermal runaway of different cathodes, the gases produced are mostly ethylene, propylene, carbon dioxide, carbon monoxide and hydrogen. In the case of LFP cathode, the dominant gas is hydrogen gas, and in the case of NMC cathode, the dominant gases are carbon dioxide and carbon monoxide. Therefore, in the event of thermal runaway, the intensity of the explosion will be much higher in the case of LFP cathode than in the case of NMC cathode.