Their are reports from more than a few owners of these units failing withing a year or two with any steady use. They seem to be a copy of the one built by Clipper Creek - but manufactured by Delphi Auto Parts. I'd try your Dealership - but I've seen postings where the Dealer refused to replace them, citing "un-warranted damage".
If your plug shows heat-damage, the dealer could claim your receptacle was bad, and caused the damage - and may be right. Builder-grade receptacles, with worn internal contacts, will arc and generate heat, like a toaster element. Commercial grade receptacles are available at most big-box stores, and you can tell the difference - very tight contacts when you plug in to them.
First, I'd try the Dealership and see if they will replace under warranty. If they won't, I'd cut the plug off, and replace it with a heavy-duty plug, and see if that fixes the problem - the internals of the old plug may be melted/shorting out - likely killing your ground wire..
If still no joy, you can get OEM i3 chargers on eBay for under $200. - well below the $500 or $600 the dealer will want for a new one.
And, I'd see if you can get the receptacle at work changed out to a commercial grade one. I charge with the charger that came with my i3, for now, and changed out the receptacle in the garage to a commercial grade 20 amp receptacle from HD,. The charger draws 15 amps, so extended use on a 15 amp-rated builder-grade receptacle is pushing it. Lower amp "appliances" run fine on higher amp rated circuits, - and they stay cooler.
2015 i3 Rex, Capparis White, Tera World, Technology & Driving Assistant, Parking Assistant, Harman Kardon Audio System, 19 inch Rial X10-i wheels, EVoInnovate EVSE