It's encroaching on Tesla's Power Wall territory too, with lithium-ion batteries that can be taken directly from an i3 and put into service powering a home. Then there's BMW's partnership with Solid Power, a Colorado-based facility researching solid-state batteries, the future of battery architecture. For Stefan Juraschek, BMW's head of electric powertrains, these are necessary steps in the automaker's grand plan to go all-in on electric.

"What we are doing right now," he said in an interview last week at the North American International Auto Show in Detroit, "is we are setting up a new generation."

He describes this next generation as a modular electrification kit that BMW's entire fleet can use, be it a full electric drivetrain or the hybrids the automaker currently offers. You can see this platform in action with the hybrid Mini Countryman S E that debuted in late 2016. The all-wheel-drive compact uses the i8's dual-motor setup, with a gas engine providing power to one set of wheels while an electric motor drives the other. It's a smart stop-gap solution until reality catches up with the battery technology and charging infrastructure required to go full electric.

Current lithium-ion battery capacity grows between 5 percent and 7 percent each year -- just look at the i8's jump from 2017 to 2018 if you need proof -- and Juraschek expects those gains to continue. By 2025, they could as much as double from where Li-ion battery capacity was last year. He also predicts Li-ion will be the dominant power supply for at least the next decade.

Come 2025, Juraschek expects that research and development on solid-state batteries will potentially have evolved such that next-gen power supplies can be put into BMW's cars. However, he doesn't anticipate high demand initially, nor does he seem particularly sold on the power supply just yet.

"We assume or expect [solid-state batteries] might be an increase in energy of 20 to 30 percent, but in terms of power," he said, "we aren't sure if we can increase key figures to a higher level." And by key figures, he was referring to things like overall capacity and output. There's also an issue with battery temperature. Solid-state batteries generate (and can withstand) lots of heat, but BMW isn't sure how that will affect performance or passenger comfort.