Triggering Thermal Runaway in Lithium-ion Batteries

The proliferation of lithium-ion batteries enables electric devices such as cell phones to electric vehicles to become a reality. A latent danger, however, exists in these batteries. Mechanical, thermal, or electrical damage can initiate a phenomenon known as thermal runaway (TR). This damage causes internal short circuits within the battery, releasing heat and triggering exothermic decomposition reactions. The battery will catch fire if rapid cooling is not present. While experimental designs exist for evaluating TR, significant safety hazards and impracticality may impede testing efforts. Finite element analysis, therefore, becomes a vital tool in modeling TR and mitigation techniques. However, there is limited literature on modeling and evaluating TR in generalized models. This research saw the development of a generalized battery holder which can prevent TR propagation in different applications. Two objectives were met in the research. The first was a simulation of TR in a single 18650 cell from which temperature and heat generation data was calculated. Upon successful triggering in this single cell, the second objective involved inserting the battery into a generalized battery case called the “honeycomb”. This honeycomb holds seven total cells with one cell forced to undergo TR. The surrounding six cells would have their temperatures monitored. Multiple studies were then performed to see effects of properties such as materials, dimensions, or trigger cell arrangements on surrounding cell temperatures. Parametric combinations of properties can be trialed, and optimal values found to reduce weight, cost, and other real-world considerations. The symmetric honeycomb geometry can be linked with other honeycombs, expanding the number of cells indefinitely for various applications