Google Pixel has really bad battery life

My google pixel works fine though in Android and Linage Os but the battery drains a bunch. When it is on 100% it drains quickly from 100% to 0% shut down in 20 mins and sometimes just randomly shuts down. After this you have to plug it back into power else it just won't boot. The only way to use this currently is to have it always on a powerbank so any help is very appreciated. Also something I noticed is that the battery is able to keep a charge for a while as it is on 30% after not using for a while so I think it may be the motherboard. Thank you in advance.