Sledge is the best way if you are at home. Had the same issue with some rally wheels I had powder coated. Could not unseat the rim. I loosened all the lug nuts so the wheel didn't dislodge and fly off when I hit it and had to beat the tire/wheel with a sledge and used a 2x4 to spread the load so I didn't damage the rim. It took a lot of force to dislodge it.
I put grease between the hub and the wheels when it went back on and it did not stick again. I think the powder heats up and bonds the rim to the hub.