Novel Thermal Runaway Degree (TRD) in Li-ion batteries

Image Reference: Cui Y, Shi D, Wang Z, Mou L, Ou M, Fan T, Bi S, Zhang X, Yu Z, Fang Y. Thermal Runaway Early Warning and Risk Estimation Based on Gas Production Characteristics of Different Types of Lithium-Ion Batteries. 2023; 9(9):438.

Image Reference: Cui Y, Shi D, Wang Z, Mou L, Ou M, Fan T, Bi S, Zhang X, Yu Z, Fang Y. Thermal Runaway Early Warning and Risk Estimation Based on Gas Production Characteristics of Different Types of Lithium-Ion Batteries. 2023; 9(9):438.

The essence of the Thermal Runaway (TR) phenomenon lies in an imbalance between heat generation and dissipation within the lithium-ion battery. 

While there have been extensive studies to comprehend the dynamics of LIB safety, there's an urgency to understand the early stages of TR to avert potential disasters. Current techniques to detect TR rely on monitoring the individual cell voltages and temperature readings. Though informative, these methods demand intensive data analysis and often result in delayed alerts, which can be detrimental during a live TR event.

As researchers continue to study the intricacies of TR, there has been a growing interest in 'Gas Production Analysis' during this process. A recent study by Cui Y et. al. (2023) dives deep into this aspect, offering novel insights. The research zeroes in on the gas production patterns of NMC/graphite and LFP/graphite cells under varying trigger conditions. Their findings suggest that certain gas signals can indeed serve as early signs of TR, often signaling potential risks well before traditional temperature or voltage alerts. This could translate to advanced warning times ranging from '16 to 26 minutes'.

Emerging from their study is a novel parameter called 'Thermal Runaway Degree (TRD)'. 

TRD= Molar quantity of gas production x Square root of the peak temperature during TR.

TRD offers a quantitative yardstick to evaluate the severity of TR events. This parameter is influenced by both the energy density of cells and the specific conditions that trigger TR. Impressively, despite the several uncertainties inherent to the TR process, TRD showcases consistent reliability, with a maximum relative deviation less than 5%. Such consistency positions TRD as a potential key parameter for gauging the safety risks of various LIBs.

The study's graphical abstract shows different gases produced during TR, including hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2) etc. By monitoring the release of these gases, the researchers could achieve early warning for both NCM and LFP cells.

The introduction of TRD, in particular, stands out as a promising metric, not just for early detection but also for quantifying the severity of TR events.