1.   Because the gel is less flammable, the change will let manufacturers create batteries with thinner walls and less expensive safety circuitry than current lithium ion cells require.

2.   For more sustained power, high-energy batteries, like nickel metal hydride and lithium ion, are better suited, Ms. Brush said.

3.   Nickel metal-hydride is a leading contender, but the answer might be lithium ion, which is also in commercial use in portable electronic devices.

4.   Lithium ion is a new battery technology that allows for higher power output and greater storage capacity than lead or nickel-based batteries.