*A Critical Review on the 3D Modeling and Mitigation Strategies in the Thermal Runaway… DOI: http://dx.doi.org/10.5772/intechopen.114319*

reactions are disregarded. At the end of the time-dependent simulation (8560 seconds), the highest temperature is observed on the outer surface of the cell, gradually decreasing toward the center. This observation aligns with the current simulation condition, wherein the external heat input originates from a heater or heat flux.

It is pertinent to acknowledge that the maximum surface temperature achieved in this simulation is 122°C, significantly lower than the experimental temperature value of 176°C. This variance is expected due to the exclusion of internal exothermic reactions in the simulation. The absence of these reactions elucidates the lower temperature recorded in the simulation compared to the empirical values.

**Figure 1(d)** illustrates the implications of the simulation conducted under an overheating test scenario, focusing on the structural deformation and stress distribution within the LIB cell. As illustrated, stress concentration becomes apparent along the cell wall at the conclusion of the time-dependent simulation (8550 seconds). This stress concentration likely arises from the thermal expansion of the active battery material due to the heightened temperature. In summary, the simulation suggests that increased temperature induces thermal expansion, resulting in stress concentration along the cell wall. The observations in **Figure 1** indicate that elevated temperature conditions can significantly impact the structural integrity of the LIB cell.

As the temperature increases within a battery cell, it can trigger several exothermic chemical reactions. These reactions generate additional heat that accumulates inside the cell. If the heat generation rate surpasses the rate at which heat dissipates to the surroundings, TR may become inevitable once the cell reaches a critical temperature.

As thermal runaway (TR) ensues, heightened internal temperatures accelerate chemical reactions among cell components, giving rise to potential hazards including leakage, smoke emission, gas venting, and the initiation or propagation of flames. The unchecked progression of TR ultimately threatens the integrity of battery cells. Thus, it is imperative to comprehend and address the risks inherent in TR to uphold the secure functioning of battery systems. This study considered four specific exothermic reactions [37].


By considering these four exothermic reactions, the study aimed to understand their impact on the thermal behavior and potential for TR in the battery system [38] (**Table 1**).


#### **Table 1.**

*Presents the parameters used to calculate the reactions [38].*

#### **Figure 2.**

*Temperature distribution in the oven heating test (with exothermic reactions) of the LIB.*

The temperature distribution is depicted in **Figure 2**, considering the exothermic reactions within the LIB. As a result of the increased internal temperature, these exothermic reactions are triggered. Consequently, the temperature profile displayed in **Figure 2** shows a distinct and noteworthy pattern that differs significantly from that observed in **Figure 2**. Exothermic reactions notably impact the temperature distribution within the battery cell.

**Figure 3** represents the surface temperature change over time, showing significant insights. Initially, the surface temperature gradually increases due to ohmic heating during charging and discharging cycles. However, a distinct change occurs around 7500 s, when the temperature curve rises sharply, reaching approximately 90°C. This temperature rise indicates the onset of self-heating.

As the temperature exceeds 120°C, the temperature increase becomes exponential, indicating the existence of TR. Notably, the simulation results agree with the findings from destructive tests, where self-heating was observed around 110°C, and the surface temperature reached values of 170–180°C. These results also align well with experimental measurements, precisely with the recorded temperature of 176°C. Additionally, the simulation captures the time trend observed in the experimental results.

Leveraging advanced modeling tools and methodologies, their research has effectively encapsulated the electrochemical and thermal-mechanical intricacies of large*A Critical Review on the 3D Modeling and Mitigation Strategies in the Thermal Runaway… DOI: http://dx.doi.org/10.5772/intechopen.114319*

#### **Figure 3.** *Surface temperature of the LIB cell with time and TR occurrence.*

scale LIBs. These numerical simulations have deepened the understanding of failure mechanisms, empowered thorough risk assessment, and facilitated the formulation of robust safety measures for LIBs. The adoption of such modeling tools stands as a cornerstone in fortifying battery safety protocols and preemptively addressing potential risks.
