Remaining Useful Life of Lithium-ion Batteries as a Function of the Joule Effect

The main purpose of this article is to propose a novel definition for the remaining useful life of lithium-ion batteries based on the increase of the inefficiency related to the Joule effect due to the growth on the internal impedance of the battery as it degrades. The applied methodology consists in the cycling of a rechargeable lithium-ion cell at different discharge current rates considering and a defined charging protocol. The experiment was conducted inside an environmental chamber allowing a constant ambient temperature of 25°C, and 50% of relative humidity. The results show that even though that heat generation does not increase significantly as the battery degrades, the evolution of the proportional generated heat in time has a notorious increment since the cycles have a shorter duration. As a consequence, the battery experiences a temperature rise according to the ventilation it has. Finally, the proportion of heat generated in time is proposed as a metric to define the remaining useful life of a lithium-ion battery.