Are there any electric ultralight aircraft?
ElectraFlyer offers a Part 103 legal trike, and at least as of two years ago, had a flying prototype of a more conventional designed single-seat Part 103 legal ultralight.

Realistically, given the weights of engines and batteries compared to the weights of the Rotax or similar engines usually used on ultralights, it's possible to turn many Part 103 designs into electric power, provided you're willing to do the engineering work yourself. For a fairly extreme example, see Dale Kramer's eLazair, a twin electric motor conversion of the Lazair ultralight that retains its Part 103 status.