Well, when PDF recently shipped some RC LiPo to me, he had all the hazmat papers and labelling, properly packed, etc., but the UPS guy didn't know what to do with that and I guess was afraid to ship it labelled like that, so the UPS guy stuck it inside another box with no labelling whatsoever.
Personally, given their complete lack of caring or knowledge, I'd just call it a "power supply" and ship it as-is.
But if you want to completely comply with all the regulations, you'll probably have to call the main UPS line to get links to all the paperwork and whatnot, and there will also probably be extra fees to ship it that way.
Here's a search on the UPS site for Hazmat and Lithium:
http://www.ups.com/search/quick?loc=en_US&results=25&view=both&query=hazmat+lithium&searchButton=
one of which brings up this page:
http://www.ups.com/content/us/en/resources/ship/hazardous/variations.html?srch_pos=2&srch_phr=hazmat+lithium
and this page:
http://www.ups.com/content/us/en/resources/ship/packaging/supplies/hazmat.html?srch_pos=1&srch_phr=hazmat+lithium&WT.svl=SRCH
which are probably the most relevant.