Last week IDTechEx reported on work at Stanford University tackling the issues of low energy and power densities in lithium-ion batteries using sulphur particles. Now another significant problem associated with electric vehicle batteries is being explored by US based company Leyden Energy by exchanging traditional battery chemistries.
With an increase in battery power density comes the risk of over-heating and thus shortened battery life. The company are currently developing a Li-ion battery with the aim of increasing potential power density whilst maintaining functionality at high temperatures of up to 60 degrees Celsius. A combination of graphite current collector and electrolyte elements formed from imide salt increase the battery life-cycle and temperature resistance.
Imide salt replaces the conventional use of lithium hexafluorophosphate that begins to decompose at room temperature and shortens the battery's life cycle by reacting with water in battery cells. However, solving this issue brought forth another; imide salt corrodes aluminium, the usual material used for current collectors. To overcome this the company substituted aluminium for non-reactive graphite.
"The key advance for Leyden is not the electrolyte. Their magic is, they are not using aluminium as the current collector," says Venkat Srinivasan, a scientist at the Lawrence Berkeley National Laboratory who has seen the company's technology. "This change allowed them to change the electrolyte."
The company claim to have achieved energy density efficiencies 50 per cent higher than current EV batteries at 225 watt-hours per kilogram. Although details regarding how this has been realised have not been revealed.
"Leyden's cell technology presents a very real advantage for a vehicle battery pack in terms of thermal management, life-cycle performance, and energy density," explains Brian Wismann, director of product development at Brammo.
If a significant increase in temperature tolerance can be accomplished, the liquid and thermal cooling systems currently utilised in many EVs could be replaced by smaller, lighter units or even air coolants.
For more attend Electric Vehicles Land Sea Air USA 2012.
Also read Electric Vehicle Traction Batteries 2011-2021 and Car Traction Batteries - The New Gold Rush .
References: Leyden Energy, Technology Review
Image source: Technology Review