The visitors trailed to a 26th-minute goal from Robert Cornthwaite but turned things in their favour with an Eninho penalty (57) and a Seo Sang-Min strike (71).
The scores were level eight minutes later thanks to Flavio Oliva, but Jeonbuk had the final say with Lee's goal.
Second-placed FC Seoul lost ground on the leaders as they battled out a 3-3 draw at Jeju United.
The home side were in front after just four minutes through Junior Santos and Bae Il-Hwan doubled that advantage after 26 minutes.
Mauricio Molina pulled a goal back for Seoul five minutes later before Dejan Damjanovic's double (40 and 49) gave them the lead for the first time in the match.
However, Jair's 65th-minute effort for Jeju ensured the points were shared.
Daejeon Citizen continue to prop up the standings after a goalless draw at home to Ulsan Hyundai, while Choi Chul-Soon's late goal earned Sangju Sangmu Phoenix a 1-0 victory over Gyeongnam.