Donald Sadoway, professor of materials chemistry at the Massachusetts Institute of Technology, said in an email: "If they get hot, they'll bloat, and the case could rupture. Explosion as a result of autogeneous heating perhaps could happen if one cell in an array caught fire and the fire spread. But I'd be surprised if a single cell would explode."
Experts also said that prospective EV buyers and owners should not worry that their electric car batteries could explode during a collision.
"If a battery is operating normally and there's a collision that causes the cell case to rupture, the contents would still be at normal temperatures, and you wouldn't have an explosion, or even a fire," Cairns said.
Battery experts emphasized that lithium-ion batteries contain a flammable electrolyte, which has a well-understood fire risk. But they said today's conventional vehicles burn gasoline, which also carries a fire risk.
"You have to put it perspective," Cairns said. "The fire danger from the battery is still far less than the fire danger from a tank of gasoline.
For a close-up look at GM's Chevy Volt, go to the Drive for Innovation site and follow the cross-country journey of EE Life editorial director, Brian Fuller.