In that case, I'm going to guess that it's just the humidity making it feel sticky, especially if you don't actually see any residue on it. (You didn't say, so I'm only guessing re: residue.) Battery warms up, attracts moisture from the air, battery feels sticky/ tacky. Not sure if there is anything you can do to fix it. If there is a residue, then, again, I'm at a loss.
Also, just a word of caution, and take it with a grain of salt as I am by no means an expert, BUT: my understanding is that your battery itself shouldn't ever be getting warm/ hot if it is functioning properly. The atty might warm up with use, but the battery shouldn't be any warmer than room temperature (or your hands, if you don't put it down often).