SAN JOSE, Calif. — For years, scientists in laboratories from Silicon Valley to Boston have been searching for an elusive potion of chemicals, minerals and metals that would allow electric vehicles to recharge in minutes and travel hundreds of miles between charges, all for a much lower cost than batteries available now.Now a few of those scientists and the companies they founded are approaching a milestone. They are building factories to produce next-generation battery cells, allowing carmakers to begin road testing the technologies and determine whether they are safe and reliable.The factory operations are mostly limited in scale, designed to perfect manufacturing techniques. It will be several years before cars with the high-performance batteries appear in showrooms, and even longer before the batteries are available in moderately priced cars. But the beginning of assembly-line production offers the tantalizing prospect of a revolution in electric mobil …
