Stop syncing a SharePoint library

In the system tray at the right end of the Windows taskbar, select the blue  OneDrive icon, then select  Help & Settings > Settings.

Select  Account. 

Your OneDrive and any SharePoint libraries you're syncing are listed here.

To stop syncing a SharePoint library, select its Stop sync button.

(You also have the option to un-sync specific folders, rather than the entire library. Select Choose folders to do so.)