Tuesday, December 19, 2006

Potentially huge electric battery breakthrough

Driving back from Modesto, early Sunday morning, I heard an amazing piece on NPR about an electric car called the Phoenix. It was amazing because of the Lithium Titanate batteries, a product of Altairnano, developer of a nano-tech material to replace the graphite in lithium batteries. The carbon seems to be the source of the heat and instability that have precipitated those laptop recalls recently. You remember -- laptops bursting into flames and such.

What prevents the graphite electrodes from reacting explosively in a regular Li-Ion cell is what's called a Solid Electrolyte Interphase (SEI) barrier, which also makes recharging impossible at low temperatures. Without need for this barrier, and with tiny nano-particles with vastly greater surface area, charging is possible in ten minutes! This barrier also impedes the flow of the Lithium ions, reducing possible power, and further reducing power as the temperature decreases. They won't recharge at all below 0 degrees C. And since the nano-particles are much smaller than the graphite particles, the distances the lithium ions have to travel is much smaller, increasing the potential power. These all add up to potentially four times as much power per kg.

It also seems that when graphite is recharged with lithium ions the ions are larger than the spots they fill, causing the graphite to flex and, over time, fail. With no graphite in the system, the deep charging/recharging cycles are stress free, allowing upwards of 15,000 charge/recharge cycles, meaning the batteries could actually outlast the car.

The gory details are in this pdf.

These folk in Maui are planning to rent them in 2007.


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