The race is on to perfect a plastic battery the size of a playing card that would make electric cars an attractive alternative to gas-powered vehicles, scientists say.

Interest is so great, they say, electric automobiles will be streaming down America's highways by the end of the decade."It's a matter of time," said Duward Shriver, a professor at Northwestern University.

Electric cars use no gasoline and emit no carbon monoxide, making them attractive in a world worried about pollution and nervous about the Persian Gulf crisis cutting off oil. However, electric cars need several batteries to cover long distances without recharging, and standard auto batteries are heavy and bulky.

The solution may be the card-size plastic battery. Scientists here for a symposium say that the technology is available and that such a battery could be developed within a few years, ushering in the mass use of electric cars.

"We're trying to replace batteries of a traditional kind with a battery of a much less traditional kind," said Mark Ratner, a Northwestern University chemistry professor.

General Motors Corp. plans to manufacture an electric car, but it would require 32 standard lead-acid car batteries, said spokeswoman Toni Simonetti.

Ratner said the lead-acid battery is heavy and somewhat dangerous because it gives off toxic substances. But batteries made out of polymers, or plastics, are light, don't pollute and present few if any dangers.