The pressure of aging on lithium-ion batteries
Few technologies are paving the way for innovation and catalyzing product advancements like lithium-ion batteries. The market is projected to double in size within the next three years as the batteries continue to be adopted in industries such as automotive, aerospace, renewable energy, utilities and telecom.
The interest in lithium-ion batteries is attributed to the evolution of secondary (or rechargeable) technology. As a result, these batteries provide greater energy density, longer life cycle, higher efficiency and improved reliability and performance standards. Given the critical importance of lithium-ion batteries to electric cars, advanced commercial jets and electric grids, it is imperative to conduct research and advance battery standards, maximizing safety as well as safeguarding the adoption of new applications and uses.
The continuing advancements in high power and energy applications require a sustained effort in analyzing cell and battery safety and performance. In addition, the expected demands on the high power and energy cells and batteries (i.e., “duty cycle”) puts greater emphasis on understanding the limits of the electrochemical reactions. Advancing safety is critical to facilitating progress, as innovation is not possible without assessing and mitigating risk.
While the rate of failure is small for lithium-ion batteries, there have been incidents that call attention to their potential risks. These concerns for safety must be addressed, and standards have been enacted to mandate a number of tests designed to assess specific risks associated with their use, thus helping to ensure minimal risk and maximum efficiency.
Challenges and testing
The widespread commercial use of lithium-ion batteries began in the 1990s, and designs were developed to meet an array of product demands. Normally, the choice of battery is driven by considerations such as application requirements for power and energy, the anticipated environment in which the battery-powered product will be used, and cost. With lithium-ion batteries, the selection means choosing something generally more expensive than alternatives, but offering significant advantages including higher energy and energy-to-volume or energy-to-weight ratios.
Challenges in performance and safety still exist for all batteries in various applications. Users increasingly expect lithium-ion batteries to last for longer periods of time, with some applications expected to have a battery life of five to 20 years. Also, some lithium-ion cells used in large format applications such as electric vehicles may be considered for reuse in energy storage applications since they often still have as much as 80 percent of their usable capacity left at the end of their life in a vehicle. These long-term usages are important to consider when developing safety requirements, because failures may be dependent on how the state of the lithium-ion cell changes over time. Current safety standards either do not address the potential impact of battery aging or do not go far enough in the aging process to understand long-term usage effects. Given the trend toward lithium-ion battery long-term usage and potential for reuse, the effects of aging need to be studied to understand how it affects battery failure.