Over the years, one of the biggest obstacles to widespread electric vehicle adoption has been the issue of how far the car can travel on one charge.s the issue Tesla Motors is trying to solve with an innovative new type of battery it has just filed to patent — a hybrid lithium-ion and metal-air battery pack that could extend the range of the company’s electric vehicles to 400 miles between charges.

The hybrid battery will rely on the more expensive, but more durable lithium-ion component for short-term travel, switching only to the metal-air battery for longer trips.