The nEXO Collaboration is performing R&D towards a detector with ∼ 5 t of enriched liquid 136Xe to search for neutrinoless double-beta decay. The experiment is based on the success of the EXO-200 detector, an ultra-low background time projection chamber with collection of both scintillation light and ionization charge from xenon. The projected sensitivity of the nEXO detector will probe the inverted hierarchy of neutrino masses.