If the chassis of your laptop or smartphone gets thicker than usual, this is a sign that the battery is swollen. Li-ion batteries are packed into a dense black plastic coat. After some years, all batteries tend to leave some gas. If you search for repair options, they are all giving warnings:

You should never puncture a swollen laptop battery with a needle or any sharp object. Here's why:

Extreme Hazard:

- Fire/Explosion Risk: Lithium-ion batteries contain flammable electrolytes. Puncturing the casing can cause a short circuit, rapid thermal runaway, or ignition, leading to fires or even explosions.