Apple has determined that, in a limited number of older generation 15-inch MacBook Pro units, the battery may overheat and pose a fire safety risk. Affected units were sold primarily between September 2015 and February 2017.
If you think you may have an affected device you need to go to the official Apple page concerning this safety issue: https://support.apple.com/en-gb/15-inch-macbook-pro-battery-recall
Then choose a store and take your laptop in to get the battery replaced. Not sure on the turnaround for this.