Expanding batteries are bad news! It is caused by the chemicals within releasing gasses causing them to swell. This is particularly bad with modern electronics which use Lithium-Polymer technology. Remember secondary school chemistry? Remember group 1 metals … the ones that spontaneously combust on contact with water? Yep, Lithium is one of those.
Expanding Li-Po batteries, in our experience, are more common among Apple MacBooks where they’re often placed beneath the (glass) trackpad. When the MacBook batteries swell, they often push the trackpad up out of the case and can often damage them.
Thankfully, for this battery from an HP Omen gaming laptop, the bodywork of the laptop is made of plastic which, being flexible, allowed the battery to expand without putting too much pressure on it. It looked terrifying with its distorted and bulging keyboard, but with a replacement battery, the laptop was a-OK and still works fine.
Does your laptop not hold a charge at all? Does it report a high percentage and power-off suddenly? Is the laptop bulging at all? These could all be signs of a failing battery. Get them in fast! Failing Li-Po batteries can be a non-ticking time-bomb if not addressed quickly. Be safe; get it replaced!