Toshiba has developed a new fast-charging lithium-ion battery with an extended lifecycle that has significant potential for application in hybrid and full-electric vehicles.
According to the company, the prototype of the battery can recharge 80% of its energy capacity in only one minute, approximately 60 times faster than the typical lithium-ion batteries in wide use today, and will lose only 1% of its capacity after 1,000 cycles of discharging and recharging.
On those two criteria, the Toshiba battery meets the long-term specifications for advanced battery technology for vehicles set by the US Advanced Battery Consortium.
|Toshiba Li-Ion vs. Select USABC Criteria|
|Parameter||USABC Mid-term||USABC Long-term||Toshiba Li-Ion|
|Energy Density (Wh/l)||135||300||150–250|
|Fast Recharge (40%–80%)||<15 min||<15 min||80% in 1 min|
|Normal Recharge||<6 hours||3–6 hours||10 minutes|
Pragmatically, the speed and capacity of the recharge isn’t as major a factor for grid-connected plug-in recharging of the battery (which presumably would happen at night), as it is for the capture of energy from regenerative braking. (Although I suppose you could hypothesize a widespread infrastructure of electric recharging stations where drivers could queue for a quick jolt.)
The current crop of more slowly charging batteries let much of the converted kinetic braking energy go to waste—they just can’t capture the charge fast enough. To counter that, some hybrid and full EV applications use ultracapacitors as a means of burst capture and release. The US Advanced Battery Consortium in funding the development of ultracapacitors for use in hybrids for that purpose. (Earlier post.)
Although Toshiba did not release full performance specs for its new battery, the company is positioning it as nearly equivalent in terms of speed of recharge to capacitors. (Nothing said about the speed of discharge, which is the other critical aspect to ultracapacitors in electric vehicles.)
The energy density of the new battery is between is 150 to 250 Wh (Watt-hour)/liter, equal to the lower range of energy densities existing lithium ion batteries have, according to a report by EE Times. Ni-MH batteries have lower energy densities.
The battery’s voltage, which Toshiba did not specifically disclose, is lower than the 3.6 volts of present lithium ion batteries. The prototype has a capacity of 600mAh and measures 8mm thick, 62mm high and 35mm deep.
A description of the technology comes from the EE Times report:
The battery employs a cobalt-based anode and a non-carbon material cathode in place of carbon material that is used for conventional lithium ion batteries, but Toshiba calls it a lithium ion battery because the electric charge movement depends on lithium ion.
Toshiba achieved the breakthrough by using nanoparticles of several hundred nanometers coated uniformly on the negative electrode and newly developed electrolytic solution. This stable formulation does not react with lithium ions at the cathode in a manner that would lower the battery’s cycle time. The electrolytic solution and nanoparticles enable large number of lithium ions move quickly to the cathode and store in the particles in recharging mode.
Now Toshiba just has to figure out how to scale it and manufacture it. That latter may be complicated by Toshiba’s closing its Li-Ion battery subsidiary last year and selling the plants to Sanyo. Toshiba plans to produce the battery in its fiscal 2006 (ending March 2007).