Volvo has shifted its green car strategy to focus on developing plug-in hybrid technology over standard hybrid and electric-only vehicles. The carmaker has announced that it will be building a plug-in electric hybrid, most probably based on its V70 model, by the year 2012. The concept version – introduced at a Monday press conference – unites a lithium-ion battery with a diesel powertrain.

“This is a significant leap compared to our earlier plans of offering a regular full-hybrid on the market by 2012,” Volvo chief executive Stephen Odell said in his presentation.

The new initiative will be a joint venture with Nordic electricity firm Vattenfall, which will help develop the plug-in charged lithium-ion battery. The partnership should fast-track the technology and allow Volvo to begin mass-production within three years.

As a diesel hybrid, the V70 plug-in will recharge either directly from the home outlet, or from a network of charging stations that Volvo hopes will have been established by the time the car becomes available. This infrastructure, however, is highly speculative at this point. The car will fully charge in just five hours, allow almost 50 kilometers (31 miles) on electric-only power, and produce emissions below 50 grams of carbon dioxide per kilometer. That’s less then half the number produced by the average hybrid currently on the market.

Volvo’s new plans come during a time when the company’s exact future remains an uncertainty. The brand has been put up for sale by parent, Ford, and there are reportedly several interested buyers.

It’s unclear as to where the plug-in car will initially be marketed, and how long it will be before it even reaches U.S. shores. Regardless, Odell calls the effort “a giant step toward offering our customers cars with an even smaller environmental footprint.” Three separate V70 plug-in demonstration models will be unveiled later this summer.