Sandia National Laboratories is researching ways to refine lithium-ion batteries for use in hybrid cars. Commonly used to power a vast array of consumer electronics like notebook PCs, mobile phones, and MP3 players, and portable video game systems, lithium-ion technology is expected to increase the mileage efficiency of hybrid cars by two to three times over conventional models that employ nickel-metal hydride.

Lithium-ion isn't used in vehicles because of a tendency to overheat easily. Sandia's efforts are aimed towards refining these batteries so that they can function alongside gasoline operation without being effected by heat springing from the process.

Via (CNET)