Trilithium is an element featured in the episode The Big Rip-Off from the 1987-1996 animated TV series. A rare crystal of trilithium was being kept in an airtight vault in Fort Charles and guarded by the CY-CLOMPS supercomputer.
Krang dismissed the trilithium as being too unstable to be useful to them, but Shredder came up with the idea of feigning an attempt at stealing it in order to distract the Turtles. He went after the crystal in earnest later on, believing that it was the only option to repower the Technodrome, but the Turtles tossed the crystal to one another to keep it out of his grasp. When it destabilized, Shredder threw it back at them, only to have Donatello bat it down after his escaping module. The crystal then exploded.