The song - which she first performed at the iTunes festival in London back in September - is an emotional piano-led ballad and was co-written by British singer-songwriter Emeli Sandé.
"'Brand New Me' is about the journey it takes to get to a place where you are proud to be a new you," Keys told AOL's The BoomBox.
"There is nothing wrong with growing! There may be people in your life that knew you for a long time and they think of you only as the person you used to be and not the person you now are.
"This song is a conversation introducing them to the new you, where nothing can hold you back and no-one can hold you down."
Keys also tweeted a link to what appears to be cover art for the song, suggesting it may be the second release from her forthcoming album Girl on Fire. The singer revealed the tracklisting for the LP last month, shortly after she unveiled the video for the record's lead single.
Keys is due to perform at this weekend's (November 11) MTV EMAs alongside The Killers, Pitbull and K-Pop sensation Psy.
"I'm crazy excited to share music from my new album Girl on Fire with the world," she said of her upcoming appearance at the show.
"I feel such a powerful energy around me when I'm performing, especially on a night like the EMAs. It's electric! I also get to be inspired by all of the other incredible artists."
Listen Alicia Keys performing 'Brand New Me' live below: