Thermal Runaway and Propagation in Lithium Batteries: Understanding the Issue and Proposed Solutions

Introduction

Thermal runaway and propagation in lithium-ion batteries present significant safety risks, potentially leading to disastrous outcomes. Understanding the triggers and mechanisms of thermal runaway is vital for devising effective preventive strategies. This post provides an overview of the issue, delving into factors influencing thermal runaway propagation, and proposes a potential solution to mitigate this problem.

Understanding Thermal Runaway and Propagation

Thermal runaway refers to an uncontrolled temperature increase within a battery that leads to a self-sustaining exothermic reaction. It can be initiated by various factors such as overcharging, overheating, mechanical abuse, or internal short circuits. Once initiated in one battery cell, it can propagate to adjacent cells resulting in a chain reaction that could lead to fire or explosion.

Several elements influence the propagation of thermal runaway including thermal conductivity and heating rate of the battery, its diameter, ambient pressure, and state of charge. Two different types of propagation fronts have been identified: regular polygons and circles with heating power also play a role in influencing the mode & speed at which thermal runaway propagates.

Proposed Solution: Emergency Spray Cooling

Emergency spray cooling has shown promise as an effective method for suppressing individual cell's thermal runaway but when dealing with multi-cell battery packs precisely focusing spray on affected cells becomes challenging; understanding how spray cooling affects spread among batteries is crucial here.

By controlling spraying time it was aimed at determining its impact on inhibiting such events.

Experimental Setup & Findings

18650-type lithium-ion batteries were used along with an apparatus consisting of modules for battery pack assembly, spray system setup & data acquisition respectively; batteries were subjected to induced-thermal-runaway via heaters while activating the spraying system simultaneously for cooling purposes.

Results indicated continuous spraying effectively inhibited the overall module's propensity towards experiencing propagated-thermal-runaway events; it increased the time between transmissions by approximately 4 minutes. It was observed that the thermal runaway propagated in concentric circles with batteries on the same circle forming a group.

Conclusion

Thermal runaway and propagation in lithium-ion batteries pose significant safety risks; understanding the factors influencing its propagation is crucial for developing effective preventive measures. The potential of emergency spray cooling as a solution to inhibit such events has been highlighted; continuous spraying was found to be effective in suppressing propagation within battery modules but further exploration is needed to understand complex interactions between spray cooling & thermal runaway within multi-cell battery packs.

Addressing the issue of thermal runaway and propagation requires a multifaceted approach including improved battery design, advanced thermal management systems along with preventive measures like emergency spray cooling. Continued efforts are essential for ensuring safe & reliable operation of lithium-ion batteries across various applications.