The lightest alkali metal, high reactivity Lithium can be used for very safe rechargeable green power source, although its enthalpy is only twentieth of unrecyclable gasoline.
As we know, temperature is major factor about chemical reaction in kinetic and collision
Fire happens in chemical inside battery and gas tank while uncontrollable temperature rising due to heat.
In 2006 Heat Resistance Layer Technology was developed by Panasonic (Matsushida)
It will prevent overheat to cause fire in battery even if a short-circuit occurs.