Reuters: General Motors Corp’s plug-in Chevy Volt and other electric vehicles have generated widespread consumer fervor for cleaner, less fuel-dependent cars, but the high battery cost means it will be years before those cars are affordable to most Americans. Executives attending the Reuters Autos Summit this week agreed that low-emission electric cars are critical to the future of the U.S. auto market due to sky-high gasoline prices and increased concerns about global warming. But at …