Lithium-ion batteries are the hottest new thing in rechargeables. They're easier on the environment than nickel-cadmium batteries and have much higher voltages. Lithium batteries do trail slightly in so-called specific capacity, or the ampere-hours they produce per iilogram. But researchers keep plugging away at that. In the Apr. 22 Science, a team led by Kenji Sato of Honda Research & Development Co. in Saitama, Japan, reports lifting the specific capacity to a record 680 ampere-hours per kilogram, a 15% gain.
The researchers did it by stuffing an electrode with more lithium "fuel." Instead of making the negative electrode from dense graphite, they produced a spongier type of carbon by heating the chemical polyphenylene. Working with scientists at Shinshu University, the Honda team found holes big enough not only for lithium ions but also for loosely bonded lithium molecules, which are twice as big.