I would say the siege of De'an in China in 1132 is the first recorded battle using black powder weapons. They employed what was called a 'Fire Lance' to shoot flames and shrapnel a few feet out from a bamboo tube attached to a spear.

Black powder as a weapon in other forms, like gunpowder arrows or javelins that burn or explode in fire, go back even further, maybe around the end of the Tang dynasty (900AD) but to my knowledge these finds or texts are not connected to specific battles.