Yes, Beijing Capital International Airport has Free Wifi… and a Star Alliance Gold Lounge
However, you do have to go to a kiosk and register to get the user number and password. You will also need your passport to do this.
I’ve only done so in the Star Alliance Gold lounge, which has okay food (you can always find noodles in the lounges in China), warm beer, juice but no booze. There’s a kiosk right by the check-in counter where you can scan in your passport and get a login good for a few hours.