Hi,
Patience Grasshopper patience.
Try a dowel rod or similar and a good quality A&B pack adhesive like araldite.
Mix it and put it on the end of the rod and apply it to the end of the battery.
(you can roughen up the end of the battery with a sharp implement if you want)
Leave the rod glued in position securely for 3 days or so, put the dowel in a vice and get ready to pull the maglite off the battery, wearing gloves.
Why?
Because before pulling, pour boiling water over the maglite to expand the aluminium and it will be hot. Hotter than the battery temporarily, and it should slide off.
cheers