Identifying the Cause of Rupture of Li-Ion Batteries during Thermal Runaway

As the energy density of lithium-ion cells and batteries increases, controlling the outcomes of thermal runaway becomes more challenging. If the high rate of gas generation during thermal runaway is not adequately vented, commercial cell designs can rupture and explode, presenting serious safety concerns. Here, ultra-high-speed synchrotron X-ray imaging is used at >20 000 frames per second to characterize the venting processes of six different 18650 cell designs undergoing thermal runaway. For the first time, the mechanisms that lead to the most catastrophic type of cell failure, rupture, and explosion are identified and elucidated in detail. The practical application of the technique is highlighted by evaluating a novel 18650 cell design with a second vent at the base, which is shown to avoid the critical stages that lead to rupture. The insights yielded in this study shed new light on battery failure and are expected to guide the development of safer commercial cell designs.

Evaluation of quantitative CT vertebral bone mineral density measurement and the Singh index in elderly females with hip fractures--a case control study

This study aims to evaluate the ability of quantitative computed tomography (QCT) bone mineral density (BMD) measurement of vertebral bodies to predict risk of hip fracture. We also examine the predictive value of the radiographic Singh index and its relationship to the vertebral BMD. The vertebral BMD (using a QCT protocol) and radiographic Singh index were evaluated in 86 white females who had sustained a hip fracture after minor trauma. 86 age-matched female controls were also studied. All patients were post-menopausal, the age range was 52-95 years. BMD values were found to be low in both the study group and controls; there was no statistically significant difference between the groups. A low Singh index did not correlate with hip fracture, nor did it correlate with low vertebral BMD measurement. We conclude that vertebral BMD and radiographic Singh index are not reliable predictors of hip fracture in the elderly female.