BMW hopes the promise of eco-friendly performance will lure more buyers into showrooms.

BMW will update the all-electric i3 once again before the end of the year. The big news this time around is that the i3 lineup will be expanded with a range-topping model named S, according to British magazine Autocar. It will benefit from an array of performance-oriented powertrain and chassis updates including a more powerful electric motor.

Minor styling tweaks will set the S apart from the standard i3. Like the rest of the range, it will receive a redesigned front end and a new-look rear fascia inspired by the plug-in hybrid i8. Inside, the bulk of the upgrades will center around the infotainment system, which will be completely new and developed with all-electric driving in mind.

More details about the 2018 BMW i3 -- and the rumored i3 S -- will emerge in the coming months. The Geneva Auto Show is right around the corner, but we'll have to wait until this fall's Frankfurt show for the updated EV to break cover.

When it lands, the i3 S will become the most expensive member of the lineup, meaning it will start in the vicinity of $50,000 before federal incentives are factored in. That's a large sum for a compact car, but BMW executives hope the promise of eco-friendly performance will be enough to lure more buyers into showrooms.