A spare tire would fit in the hatch area. However, it would take up a significant portion of the cargo area that is already reduced by the battery. You would need to come up with a way to secure the spare tire in the cargo area either horizontally on top of the cargo organizer or vertically in place of the cargo organizer. They make tire covers for spare tires that may also help and provide a means to secure it.
I was afraid that this might be the only solution. I understand that all OEM's want to reduce vehicle weight, but this seems like the wrong way to go about it. I notice that the Ford Focus Electric, 2013 Fusion Hybrid, and 2013 C-MAX all lack a spare tire. Yet Toyota's Prius and Camry Hybrid have no trouble providing one.