You've answered your own question there
The battery in all theses devices is not a "user serviceable part". You *could* try to do it of course, but why would you? If it is in warranty, Asus will do it & you are more than likely to have replaced your sl101 within 2/3 years anyway & the battery should easily last that long.
If you really are concerned, you would need to sell your slider & replace it with a different brand that does have a replaceable battery. I think Toshiba make one