If you’ve ever had your cell phone die mid-conversation, you know the importance of long-lasting batteries.
Jeff Dahn, professor and researcher in the Department of Physics and Atmospheric Science, also knows their importance. He’s dedicated years of research focused on finding long-lasting Lithium-ion (Li-ion) batteries – rechargeable batteries that can store around twice the energy per unit mass of traditional batteries. Li-ion batteries can be used for electric vehicles, grid energy storage and implantable medical devices. In other words, batteries that have a significant impact on our everyday lives.
Dr. Dahn and his team built the world’s only high precision charger and automated storage system used for testing Li-ion batteries thanks to $120,000 from the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Accelerator Supplements (DAS).
Along with his graduate students Aaron Smith and Chris Burns, along with postdoctoral fellow, Nupur Sinha, Dr. Dahn completed the unit in November 2009 and since then, Dr. Dahn says the high precision charger has been making big waves.
Why?
“We need to know whether a Li-ion battery is going to last two years, 10 years, or 15 years,” explains Dr. Dahn who’s recognized worldwide as one of the pioneering developers of the Li-ion battery. “To do this, we constructed a 60 channel high precision charger to explore the usefulness of high precision coulombic efficiency measurements.”
Getting to number one
Coulombic efficiency is the ratio of the number of electrons delivered by the battery during discharge to those stored during recharge. Since building the charger in 2009, Dr. Dahn and his students have been able to identify changes to Li-ion battery chemistry that improve coulombic efficiency, and do experiments that show increases in coulombic efficiency translate to increases in battery life.
“A perfect Li-ion cell would have a coulombic efficiency of exactly 1.000000 – this is a battery that would last forever.”
Unfortunately, explains Dr. Dahn, on every charge/discharge cycle, about 0.1 per cent of charge is lost due to parasitic reactions within the Li-ion battery cell, which reduces the life cycle of the battery. Such a Li-ion battery would have a coulombic efficiency of 99.9 per cent.
Increasing the coulombic efficiency from 99.9 per cent to 99.99 per cent and beyond translates to Li-ion batteries with projected cycle lifetimes increasing from 1000 to 10,000 charge/discharge cycles. Electric vehicles and grid energy storage applications demand 10,000 cycles or more.
Like in most research experiments, precision is key: a more precise measurement of colombig efficiency means that the lifetimes of the batteries can be projected, often in only a few weeks of testing under actual conditions. This is incredibly exciting to battery companies, many of whom are used to doing testing that takes years.
Collaborative partnerships
The NSERC-DAS grant enabled Dr. Dahn and his group to build the high precision charger and the results generated allow them to demonstrate its use and potential for advancing Li-ion battery technology.
Dr. Dahn has assembled a group of industrial partners including: General Motors, producer of electric vehicles like the Chevy Volt; Magna E-Car systems, producer of Li-ion batteries for automotive applications; Nova Scotia Power; Medtronic Energy and Component Centre, producer of Li-ion batteries for implantable medical devices like pacemakers and defibrillators; and 3M Co., Li-ion battery materials producer.
Dr. Dahn and these partners have applied for major project funding from the NSERC Automotive Partnership Canada program and from Canada Foundation for Innovation. This funding will allow three additional state-of-the-art labs to be constructed in the Dunn Building and increase the number of students working in this exciting area.