In the rapidly evolving world of energy storage, lithium-ion batteries reign supreme, powering everything from electric vehicles to grid storage systems. Yet, understanding and predicting their lifespan remains a complex challenge. A recent study published in Mechanics of Machines, Mechanisms and Materials, led by Kirill V. Dobrego of Aktiv OMZ LLC, part of 1AK-GROUP, sheds new light on this critical issue, offering a novel approach to cycle life testing that could revolutionize how we assess and manage battery degradation.
The research focuses on NMC (nickel manganese cobalt) cells, a popular choice for their high energy density and stability. Traditional testing methods can be time-consuming and costly, often involving years of real-world use to gather meaningful data. Dobrego and his team, however, have developed an “accelerated” approach that promises to significantly speed up this process.
“We obtained one basic degradation track and then extrapolated the results to other temperature and current operating conditions of the cell,” Dobrego explains. This method involves long-term cycling of a lithium-ion NMC cell at a current mode of 0.5C at room temperature, providing a foundation for predicting performance under different conditions.
One of the key findings of the study is the behavior of internal resistance. Contrary to some expectations, internal resistance does not show a clear, monotonic trend of change during cycling. This means it cannot be reliably used as an indicator of the state of health for these types of cells. “The internal resistance does not demonstrate a pronounced monotonic trend of change during cycling and cannot be used as an indicator of the state of health of cells of this type,” the study states.
The research also introduces a model of continuous cell degradation that can account for varying current conditions and load patterns. This model could be integrated into battery management modules, providing real-time monitoring of capacity loss trends. The implications for the energy sector are profound. By better understanding and predicting battery degradation, companies can optimize their products, reduce costs, and enhance the reliability of energy storage systems.
The study’s findings could also influence the development of new battery technologies. As Dobrego notes, “Using the manufacturer’s data on cycling at room and elevated (45 °C) temperatures, a correction factor (Arrhenius function with an activation energy of 55 kJ/mol) was obtained, which makes it possible to extrapolate the results of the experimental study to the region of higher temperatures.” This could lead to more robust and efficient batteries, capable of withstanding a wider range of operating conditions.
The research, published in Mechanics of Machines, Mechanisms and Materials, represents a significant step forward in battery testing methodology. As the demand for energy storage solutions continues to grow, so too will the need for accurate and efficient testing methods. Dobrego’s work offers a promising path forward, one that could shape the future of lithium-ion battery technology and the broader energy sector.