Lithium-ion batteries are the state-of-the-art in electric and hybrid automobiles, but market leader Tesla has a history of exploring promising alternatives.

Some of those explorations may be bearing fruit.Tesla was recently granted a patent on a fast charging system for metal-air batteries, suggesting that the company isn't carrying all of its electrical fruit in the same basket.

Metal-air batteries use metal anodes, same as conventional batteries, but draw oxygen from the air to serve as the cathode.This allows the battery to be much later and therefore to achieve a greater energy density compared to conventional lithium-ion batteries.The result?More miles between charges.Happy drivers.More sales.

Tesla has a full portfolio of patents, all open-sourced to allow all manufacturers to use the company's technology without licensing fees as long as the inventions are used to improve electric vehicles.

Among Tesla's patents is a hybrid automobile design that combines a conventional lithium-ion battery pack as the primary power source and a meta-air backup power source that would extend the car's range.

Tesla's latest metal-air patent was granted on January 31.It's for a technology that allows for the rapid charging of metal-air batteries.

Tesla filed the patent originally in 2010, modifying it in 2013.Now the patent has been granted.Tesla co-founder and chief technical officer J.B.Straubel is listed as an inventor of the new charging system.