Retrofitting an existing jet seems like a vastly more viable option in 10 years. But, with sufficient funding it's possible to start from scratch and get there in 10 years.
Not when you're dependent on (i) aviation authorities to certify your aircraft and (ii) third parties to improve battery technology to the point where it can happen
Based on another article they are not doing 100% electric. They are basically using battery's to replace the alternator/APU attached to the jet engine. That still adds up to a lot of jet fuel, but is only something like 5% total fuel savings.
That's a little more achievable than the "zero emissions airliner" their website promises and would explain why they're talking about going after the A320 market rather than the ATR one (And a 5% emissions reduction over a 10 year horizon is only half what engine suppliers aim for by improved jet technology, though if it's on top of that improvement it would still be very welcome)
But if what they're building is an APU rather than a new means of propulsion involving radical wing redesigns, I'm not sure why they're talking about building their own airframe rather than getting it certified to go onto the next generation of other manufacturers' airframes
To pull this off efficenctly they are going to want a ~20,000 kg battery pack that's easily swapable on landing. That's going to take a fairly significant change to an airframe and weight distribution is going to an issue. On the other hand they would also want smaller gas tanks if it's really only doing 300 mile trips + buffer.
Longer term, they would want to start using electricity for propulsion and ramp that up as batteries improve.