Without a super-efficient battery, Plug-in hybrid electric vehicles (PHEV) are little more than scrap metal. The more efficient the battery, the longer a car can run–and the more attractive it is to people who need to drive long distances. That’s why Hitachi’s announcement that it has developed the world’s most efficient lithium-ion battery for hybrid cars–the newest battery of choice– is so important. In the past, car companies have relied on clunky and inefficient nickel metal hydride batteries.

According to Japanese Web site Nikkei, Hitachi’s battery has an output per kilogram of 4,500 watts–70% more than its current li-ion batteries and 50% more than a new model that will be released next year. The super-battery has a lifespan of 10 years, so it can stay put in a PHEV for life (or close to it).

No word yet from Hitachi on pricing, but the battery, scheduled to be released in mid-2010, will almost certainly be more expensive than its less efficient counterparts. One thing is for sure, though. Li-ion battery makers like Johnson Controls-Saft and Blue Energy should watch their backs.

[Via CrunchGear]