Lithium-air batteries are considered highly promising technologies for electric cars and portable electronic devices because of their potential for delivering a high energy output in proportion to their weight. But such batteries have some pretty serious drawbacks: They waste much of the injected energy as heat and degrade relatively quickly. They also require expensive extra components to pump oxygen gas in and out, in an open-cell configuration that is very different from conventional sealed batteries. But a new variation of the battery chemistry, which could be used in a conventional, fully sealed battery, promises similar theoretical performance as lithium-air batteries, while overcoming all of these drawbacks.

Source: New lithium-oxygen battery greatly improves energy efficiency, longevity | MIT News