The battery needs to be replaced, as soon as possible.  Remove it from the system before the swelling destroys other components such as the touchpad.

What's the best way to go about replacing the battery?

I called Dell support but they won't help as my laptop is 2 mo past the 1 yr warranty and apparently Dell warranty will never cover battery beyond 1 year. Are there any third party vendors that could help?

You need either to contact Dell Out of Warranty repair:

www.dell.com/.../out-of-warranty

or replace the battery yourself -- is this a 9333 or a 9350?

Dell have been replacing these out of warranty as they are defective and dangerous.

I have a dell xps13 9350. I called Out of Warranty repair and was told that "it's normal for battery to expand/swell after a year of use and is not related to any defect".

The quote for repair seems high for a simple battery so i'm not sure if i want to continue using Dell laptop after this experience.

Apple charges $199 for a Macbook Retina battery replacement - it would not be surprising if Dell's charge is similar, as the systems are sold in the same market position.

Were you able to get Dell to replace the battery out of warranty without charge? I have an xps15 with a swollen battery and am awaiting a PAID service call from a technician to replace it at a cost of $249. I think Dell has a legal obligation to disclose this potential problem as a danger to users, yet I have never seen the swollen battery issue noted in an advertisement or other Dell literature. Had to do some real searching to find out about it on the web.

Dell wouldn't fix it for me because my laptop is 2 months outside of the 1 year warranty. I ended up getting it replaced at a local shop for $120.

The dell reps were pretty rude on the phone and basically try to put the blame on me for "not using the battery properly". Overall a terrible experience and i will never go with dell again.

I had the same issue: a swollen battery pushing up the trackpad, and Dell refusing to do anything because although I have a 3-year warranty on the laptop it doesn't cover the battery. They offered me a refurb battery with a 90 day warranty at a cost of over £70, with a total cost of around £150 if I wanted their engineer to fit it.

So I purchased a battery from laptop-ac-adapters.co.uk for around £50. It's supposed to be a genuine brand new Dell battery with a 9 month warranty, and it looked the part when it arrived, but who knows. It was shipped from Hong Kong and took longer than expected to arrive but when it turned up it was well-packaged.

I replaced it myself, today, using a youtube video for advice. It was very simple to do (as long as you have the correct screwdrivers) and the new battery is charging up nicely. I came here to find advice on how to dispose of the old battery safely.

The whole experience reinforced my opinion of Dell as a company that I'll avoid like the plague in future. The battery was still working well in terms of charging, but I don't think it's normal for it to swell up in this way, and I think it's a design fault. If I could have been bothered I'd have tried the UK small claims court; I've since used it for another supplier of electronic goods and it works a charm in getting a more reasonable response to design faults.

Most electronics stores, home improvement stores, and municipalities will take lithium ion batteries for recycling.