Yes, to my knowledge that was only done with living donors, but you are correct:

The large majority of liver transplants use the entire liver from a non-living donor for the transplant, particularly for adult recipients. A major advance in pediatric liver transplantation was the development of reduced size liver transplantation, in which a portion of an adult liver is used for an infant or small child. Further developments in this area included split liver transplantation, in which one liver is used for transplants for two recipients. [wiki]

Interestingly, "living donor liver transplantation for pediatric recipients involves removal of approximately 20% of the liver", but you can't just take any 20% unfortunately.

If only there were more focused, high-scale, no-holds-barred research efforts on growing organs in the vat, xenotransplants from engineered e.g. pigs, for all of which proofs-of-concept and actual human trials by isolated low-funded groups exist (e.g. artificially grown trachea for a swedish girl if I recall correctly)! We have the technology, as they say, we're just too reluctant to use it.