Wow, time is rather tight, I have to say~
From airport to Badaling Great Wall, the quiest trip takes more than 2 hours and the domestic check-in usually stops 30 minutes ahead the flight departure while the international is 45 minutes ahead.
Also, 2-3 hours are needed on the wall. So make a rough estimate and then make the decision.
If you decide to go, I recommend take Airport Express to Dongzhimen, change to subway line 2 to Jishuitan, then walk to Deshengmen to take bus no. 919 fast line or through line to reach Badaling directly. FYI: Badaling Great Wall Transportation(https://www.travelchinaguide.com/cityguides/beijing/greatwall.htm)