Lithium-ion batteries are an extremely common form of rechargeable battery often found in consumer electronics such as laptops and cell-phones. At those smaller scales the batteries’ technology is reliable and well-understood, but at larger sizes there have been challenges.
The electrolyte component in the batteries is typically liquid and quite flammable, and the batteries as a whole are prone to shorts, overheating and catching fire. Boeing’s new Dreamliner 787 fleet was recently grounded worldwide after two separate incidents in which the on-board lithium-ion battery, which supplies the planes with auxiliary and back-up power, caught fire.
Improvements in larger lithium-ion batteries would be a big step forward for technologies such as electric cars or electrical grids, and thus for sustainable transportation and energy. To that end, a group of researchers at Oak Ridge National Laboratory have just published preliminary work on a new form of battery that relies on a solid electrolyte. According to a piece in today’s Climate Wire, as well as a recent report in Technology Review, the new batteries promise to be lighter, safer, and able to store five to ten times more energy than the batteries on Boeing’s 787:
The ORNL researchers, in work published in the current issue of the Journal of the American Chemistry Society, have an easy method for making a nanostructured form of one solid electrolyte. The nanostructure improves the material’s conductivity 1,000 times, enough to make it useful in lithium-ion batteries. The researchers also showed that the new material is compatible with high-energy electrodes.
The solid electrolyte isn’t as conductive as liquid electrolytes, but the researchers say they can compensate for this by making the electrolyte very thin, among other measures. Even then, the batteries might not charge as quickly or provide the same boost of power possible with liquid electrolytes, but this would be okay in many applications, such as in electric cars, where the sheer number of battery cells makes it easy to deliver adequate bursts of power.
The solid electrolyte not only makes batteries safer, it could also enable the use of higher energy electrode materials. As a result, while the rate at which these batteries deliver power may be less than today’s lithium-ion batteries, the total amount of energy they can store would be far higher. A much smaller battery could then be used—saving space and weight on airplanes and greatly reducing the cost of electric vehicles.
The team restructured the solid electrolyte to be porous at the nanoscale, which yielded the far higher level of conductivity. The solid electrolyte also helps prevent shorts, and unlike the liquid counterparts won’t degrade electrodes. That’s particularly important for building better lithium-sulfur batteries, which can store tremendous amounts of energy but have safety problems and o far haven’t been able to recharge enough times to make them useful for something like an electric car.
The ORNL team’s work is still in the embryonic stage: The tests have only been carried out with cells about the size of a coin, and the research into compatibility with lithium-sulfur batteries specifically remains unpublished.