Not a lot to go on here, but I'm going to throw out Redakai (2011–2013) as a possibility, since it fits your timeframe, and stars a black-haired boy who can transform into a humanoid battle creature.
Redakai: Conquer the Kairu, also known simply as Redakai, is an animated series that premiered on YTV and later Teletoon in Canada on July 9, 2011, on Cartoon Network in the United States on July 16, 2011 and on Canal J and Gulli in France on October 22, 2011. The series was created by Vincent Chalvon Demersay and David Michel and was co-produced by Canada's Spin Master Entertainment and France's Marathon Media in association with Canal J and Gulli. Like Totally Spies! and Martin Mystery, which were also produced by Marathon, the show's animation style has been compared to that of anime.
From TV Tropes:
The Cartoon centers around a boy named Ky Stax and his friends Boomer and Maya who quest around the world trying to collect an energy called "Kairu", the life energy of the universe before the villain Lokar and his minions find it first. They do this by fighting other teams and transforming into monsters. The episodes are different every week without much of an overarching plot.