What answer did the nursery give you? Can you post pics of the whole tree and the base of the trunk where it's planted in the ground?

They said it was an infection of some kind and the tree will die or it might not.

Possibly a fungal or bacterial disease/canker.
What is black is unfortunately dead tissue and will peel/flake off in time. If this goes around the entire trunk, the tree will likely die, sorry. If there is some healthy tissue left on the other side that we cannot see in the picture, it may recover in time, but there will be a large visable area it will have to heal over like if you pruned a large limb off of a big tree.

What maple cultivar is it? Do you know who the grower was or where it originated? What did the label/tag look like?.....it can sometimes help identify the grower. I have a similar yellow leaved Japanese maple in a 20gal pot that has the exact same disease that I've been watching for the last few months. Ill have to check which cultivar it is. Mine is still in the pot and will be planted in October if it survives. This same disease was on another Acer cultivar last year, 'Seiryu' I think. It survived after it sloughed off the layer and is callusing over. Its growing fine now.

Does the dead tissue go around the entire trunk or is it on one side only? Is it getting larger? Currently my Acer palmatum 'Ukon' has this disease.