Gasoline cars almost do not explode anymore, when you consider miles driven. However, they have not, as of this moment, figured out how to make lithium-ion batteries as safe as gasoline in a car.
Au contraire. For example, despite the publicity surrounding the handful of Tesla fires, they are one-fifth as likely to catch on fire as gasoline cars. There are 150,000 gasoline fires a year averaging 200 fatalities (source). It is just that it is so common that it is no longer newsworthy.