Energy density is the key measure of electric car batteries to determine driving range and ultimately the usefulness of the vehicle. It was the energy density improvements of lithium-ion batteries that enabled the resurgence of electric cars. But the current crop of lithium ion batteries do not allow for enough energy storage, and driving range, at a low enough cost, to get past the "too expensive" sniff test that is hindering electric car adoption today. A new lithium-ion battery designed by CalBattery, with a silicon-graphene anode, promises a dramatic energy density breakthrough, according to a news release issued by the company on Friday.
The company is a finalist in the Dept of Energy's 2012 Start UP America's Next Top Energy Innovator challenge. Independent test results using full-cell lithium-ion battery cells designed by CalBattery demonstrate an energy density of 525 watt-hours per kilogram, and a specific anode capacity of 1,250 mili-amp-hours per gram. Most commercial batteries have an energy density in the 100-180 watt-hours per kilogram range, and specific anode capacity in the 325 mili-amp-hours per gram range.
For those who don't understand battery capacity measurements, this means that per kilogram of battery weight a battery pack made with CalBattery cells will store 300% more energy than current batteries.
For the same battery pack weight this means the ability to drive 300% as far as with current electric cars, or to have the same driving range as today the battery pack would be about 1/3rd the weight.
"This equates to more than a 300% improvement in lithium-ion battery capacity, and an estimated 70% reduction in lifetime cost for batteries used in consumer electronics, EVs, and grid-scale energy storage," said CalBattery CEO Phil Roberts.
This is based on what the company has dubbed the "GEN3" silicon-graphene composite anode material for lithium-ion batteries. The key to the GEN3 design is use of a breakthrough developed at Argonne National Labs that stabilizes the use of silicon in a lithium battery anode. Silicon is known to absorb lithium better than any other anode material, it quickly deteriorates during use. CalBattery has worked closely with researchers at Argonne and other facilities to develop the new anode material, to integrate it in lithium-ion batteries having multiple cathode and electrolyte materials.
The anode is the electrode by which the electrons leave a battery into the device, while the cathode is the electrode through which electrons return to the battery, and the electrolyte is the material between anode and cathode through which lithium ions move. In other words, the anode is the negative terminal of the battery, and the cathode is the positive terminal.
Conventional lithium-ion batteries use graphite-based anodes. CalBattery's silicon-graphite anode is suitable for use with a number of other electrolyte and cathode materials. The superior results of testing at Argonne Labs led the company to believe this new anode could eventually replace traditional anodes used in most lithium-ion batteries today. Further the cost of the resulting batteries would be low enough to be cost competitive with fossil fuels for energy storage.
The company says it is now in the process of fast-tracking commercialization of the GEN3 battery anode technology. Over the next two years they plan to produce and sell silicon-graphene anodes to battery and electric vehicle OEM's around the world, and (in the U.S.) produce a limited supply of specialized batteries for high end applications. The technology could be transformational in the lithium battery market, with cost for lithium-ion batteries dropping to under $175 per kilowatt-hour.
"We believe that our new advanced silicon graphene anode composite material is so good in terms of specific capacity and extended cycle life that it will become a graphite anode 'drop-in' replacement material for anodes in most lithium ion batteries over the next 2-3 years," said Roberts.
Theirs is not the only battery energy density breakthrough in the works. In February, Envia Systems announced a cathode material breakthrough that should double the energy density at 1/4 the cost of current battery technology. In August, GM's CEO Dan Akerson talked about research between GM and Envia Systems developing battery technology which should allow GM to build 200 mile range affordable electric cars in the next two-to-four years. Earlier this year PolyPlus was named Edison Awards finalist on lithium batteries for 500+ mile electric cars. In July, a report from McKinsey and Company predicted that falling electric car prices, driven in part by battery technology improvements, would make electric cars inevitable by 2020-2025.