September 14, 2010
by Gillian Goward
The hunt is on for the for the right battery to power a plug-in electric car.
The hunt is on for advanced battery technologies that will power electric vehicles. One of these is lithium iron phosphate, which is environmentally benign and delivers excellent cycling performance.
Lithium technology just might be the answer for plug-in electric vehicles. The batteries are low-maintenance, rechargeable and provide high voltage and great capacity for a high energy density.
Most of today’s hybrid vehicles are not fully electric because they use nickel-metal hydride batteries combined with gasoline-fuelled engines and electric motors that provide extra power to assist the engine in accelerating, passing or climbing hills.
Rechargeable lithium-ion batteries used in cellphones and digital cameras have already had a significant impact on the consumer electronics revolution. Devices have become lighter and smaller; however, most consumers accept that the battery must be replaced in one to three years. Plug-in electric car batteries will be much larger, more costly, last longer and must be able to stand up to the abuses of daily driving.
Researchers from McMaster University, the University of Calgary, and the University of Saskatchewan supported by the AUTO21 Network of Centres of Excellence are searching for a battery technology that will power tomorrow’s electric cars, and they’re guided by insights gained as they peer into the tiniest of worlds where electrically charged ions move about within rechargeable battery materials in milliseconds.
They must see the movements of ions to learn how a battery performs and understand its ionic conductivity. Solving this puzzle involves powerful images provided by nuclear magnetic resonance (NMR) spectroscopy. NMR spectra are correlated to chemical interactions (how batteries hold a charge), and to what happens when a battery gets hot. This imaging helps to characterize ion-hopping processes in real-time, which is in the range of five to 10 milliseconds.
A reasonable industry goal is to develop a battery that can be recharged efficiently up to 10,000 times. Current research is focusing on tradeoffs between safety, energy density, the length of storage time, the degradation of a battery’s capacity and extended cycle-life.
There is interest in electrolyte materials other than iron phosphates as cathode alternatives. Solid-state electrolytes would mitigate the risk of fire in liquid-based electrolytes, which are susceptible to chemical degradation under heat or rapid cycling, and are the culprits in thermal runaway reactions.