The band's singer Ana Matronic revealed that the band have decided to play one of their new tracks during the live set.
"I'm hoping that we'll actually be playing a new song that people have not heard at all," she told Metro.
"I might get in trouble for telling you that but who cares? What are they going to do, fire me?"
Matronic explained that they are currently working on the album without fellow member Jake Shears, but they will all get together soon to finish the record.
"Jake is out in San Francisco finishing up work on his musical which debuts in just a few weeks. We're writing without him and he's going to come back in June and then we are all going to work together and try and put out a new album."
Matronic also teased that a fellow Lovebox performer will join them on stage, saying: "I'm hoping there is an on-stage collaboration between us and another that is playing that day. We will leave the surprise for July."
2ManyDJs, Blondie, Robyn, Kelis and Beth Ditto are confirmed to be appearing on the Sunday lineup.
Lovebox is due to take place from July 15 to 17 in East London's Victoria Park. Other confirmed headline acts include Snoop Dogg and The Wombats.
Tickets for the music event are on sale now.
Watch the video for 'Fire With Fire' by Scissor Sisters below: