Browse Topic: Lithium-ion batteries
Innovators at NASA Johnson Space Center have designed a pneumatic nail penetration trigger system that drives a Li-ion battery cell into thermal runaway using a tungsten nail. By creating a targeted rupture in a battery cell’s outer casing, researchers can initiate an exothermic chain reaction within the battery, much like a short circuit, causing a spike in temperature that can lead to battery failure, fire or explosion.
Technological advances have led to the widespread use of electric devices and vehicles. These innovations are not only convenient but also environmentally friendly, offering an alternative to polluting fuel-driven machines. Lithium-ion batteries (LIBs) are widely used in electrical appliances and vehicles. Commercial LIBs comprise an organic electrolyte solution, which is considered indispensable to make them energy efficient. However, ensuring safety becomes a concern and may be difficult to achieve with the rising market demand.
As the main power source for modern portable electronic devices and electric vehicles, lithium-ion batteries (LIBs) are favored for their high energy density and good cycling performance. However, as the usage time increases, battery performance gradually deteriorates, leading to a heightened risk of thermal runaway (TR) increases, which poses a significant threat to safety. Performance degradation is mainly manifested as capacity decline, internal resistance increase and cycle life reduction, which is usually caused by internal factors of LIBs, such as the fatigue of electrode materials, electrolyte decomposition and interfacial chemical reaction. Meanwhile, external factors of LIBs also contribute to performance degradation, such as external mechanical stresses leading to internal structural damage of LIBs, triggering internal short-circuit (ISC) and violent electrochemical reactions. In this paper, the performance degradation of LIBs and TR mechanism is described in detail, as well
Battery cell aging and loss of capacity are some of the many challenges facing the widespread implementation of electrification in mobility. One of the factors contributing to cell aging is the dissimilarities of individual cells connected in a module. This paper reports the results of several aging experiments using a mini-module consisting of seven 5 Ah 21700 lithium-ion battery cells connected in parallel. The aging cycle comprised a constant current-constant voltage charge cycle at a 0.7C C-rate, followed by a 0.2C constant current discharge, spanning the useful voltage range from minimum to maximum according to the cell manufacturer. Charge and discharge events were separated by one-hour rest periods and were repeated for four weeks. Weekly reference performance tests were executed to measure static capacity, pulse power capability and resistance at different states of charge. All diagnostics were normalized with respect to their starting numbers to achieve a percentage change
Batteries in electric vehicles can fail quickly, sometimes catching fire without much warning. Sandia National Laboratories is working to detect these failures early and provide sufficient warning time to vehicle occupants.
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