Sunday, March 21, 2010

Dr. Cui's Amazing Battery, Take 2

Dr. Yi Cui of Stanford, inventor of a paper battery, is creating more breathtaking scientific breakthroughs.

As reported in Technology Review (which, unlike Popular Science, doesn't normally tout mere-pie-in-the-sky research),
[B]y using lithium sulfide, a non-metallic form of lithium, instead of a lithium metal, the researchers have overcome a key safety issue that has plagued lithium-metal batteries.

During normal battery use, lithium metal can grow branchlike structures that can penetrate a thin polymer layer that separates the battery's two electrodes. When this occurs, the battery can short-circuit and potentially explode. With lithium sulfide, the branching does not occur.
By combining the new cathode with the previously developed silicon anode, the team created a battery with an initial discharge of 630 watt-hours per kilogram of active ingredients. This represents an approximately 80 percent increase in the energy density over commercially available lithium-ion batteries...
As evidence of TR's greater reliability, they put in this caveat.
The new battery still has significant issues, particularly in maintaining capacity. After just five discharge and recharge cycles, the cells lost one-third of their initial energy storage capacity and ceased to function after 40 to 50 cycles.
To be competitive with lithium-ion batteries, the batteries developed at Stanford would have to operate for 300 to 500 charge cycles for consumer electronics applications and as many as 1,000 cycles for vehicle use, according to Cui.
Even so, bravo Dr. Cui!

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