I'm still not convinced there's a market, except for those who want to greenwash their lawn care practices. Given that most lawn mowers sit and do nothing for the bulk of their life(residential ones at least), they're perfectly suited for a plug-in recharge cycle for pure electric operation. I have no idea if the batteries could be large enough to let the thing operate for say an hour to an hour and half (thinking of the riding mower I use in the country every now and then). Wow, and the only noise would be the blade turning? That would be a really welcome change.
Someone in the comments pointed out the GE Elek-trak. Of course, they didn't mention that the devices aren't made anymore and are used by a set of dedicated enthusiast's. Too bad, based on the comments and the info I've seen on them it was a good system. And that they are still in operation over 20 (30?) years later is a testament. The device sports a full range of plug in accessories for lawn care, recharges on a 110 outlet and has enough juice to mow about 2 acres. Sounds perfect to me. More info at elec-trak.org or do a google search for elec trak.
Pictures and commentary can be found at AutoBlogGreen