[ad#post_ad]A battery research group out of MIT and led by Dr. Gerbrand Ceder just published remarkable research findings in the journal Nature.
The scientists were able to develop a new formulation of lithium iron phosphate that allows for extremely rapid charging, and massive specific power.
In the typical lithium ion cell when a current is applied to charge the cell, lithium ions move away from the cathode compound and are trapped at the anode storage medium. When the battery discharges producing current , those ions travel back to the cathode medium and in so doing produce current flow.
Speed of charging in typical lithium-ion cells is slowed by virtue of the fact that it takes time for the lithium ion to move off the cathode material. Various techniques have been tried to increase that speed including the nanoparticle doping strategy that A123 Systems uses. However recharge times still can take hours, and specific power is limited.
The scientists noted that lithium iron phosphate forms a lattice that creates small tunnels through which the lithium ions flow, but that although the cathode seemed ideal it still took some time for those ions to travel.
The novel solution they devised was to create a lithium phosphate glassy surface to coats these tunnels. This glassy surface acts as a speedway of sorts rapidly transporting the lithium ions on and off the cathode.
The result was startling.
Per the article "extremely high rates can be achieved for the active material: at a 200C rate (corresponding to an 18-s total discharge) more than 100mAh g can still be achieved, and a capacity of 60mAh g is obtained at a 400C rate (9 s to full discharge). Such discharge rates are two orders of magnitude larger than those used in today’s lithium ion batteries."
The authors note that "Typical power rates for lithium ion battery materials are in the range of 0.5 to 2 kWkg. The specific power we observed for the modified LiFePO4 (170kWkg21 at a 400C rate and 90kWkg at a 200C rate) is two orders of magnitude higher."
At this point the researchers have only tested the cells to 50 cycles but have noted no degradation.
The authors note that this new ability to charge and discharge lithium-ion batteries within seconds blurs the distinction between batteries and ultracapacitors, and may result in radical lifestyle change in terms of consumer electronic devices and plug-in cars.
Besides being able to charge one's cellphone in seconds, this will have a major impact on electric cars.
The authors note that if electric grid power was available, an electric car with a 15kWh battery could be charged in 5 minutes. This would require the delivery of 180 kw of energy in that time frame. Further those cars could have extremely powerful acceleration and be useful in other power applications such as towing.
Lead author Ceder said "If manufacturers decide they want to go down this road, they could do this in a few years," and noted the technology has already been licensed by two companies one of which includes, you guessed it, A123 Systems.
Source ( Nature ) and ( ArsTechnica )