Nanostructured materials can exhibit phase change behavior that deviates from the macroscopic phase behavior. This is exemplified by the ambiguity for the equilibrium phases driving the first open-circuit voltage (OCV) plateau for the lithiation of Fe 3 O 4 nanocrystals. Adding complexity, the relaxed state for Li x Fe 3 O 4 is observed to be a function of electrochemical discharge rate. The phases occurring on the first OCV plateau for the lithiation of Fe 3 O 4 nanocrystals have been investigated with density functional theory (DFT) through the evaluation of stable, or hypothesized metastable, reaction pathways. Hypotheses are evaluated through the systematic combined refinement with X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) measurements, neutron-diffraction measurements, and the measured OCV on samples lithiated to x = 2.0, 3.0, and 4.0 in LixFe 3 O 4 . In contrast to the Li-Fe-O bulk phase thermodynamic pathway, Fe 0 is not observed as a product on the first OCV plateau for 10-45 nm nanocrystals. The phase most consistent with the systematic refinement is LiFe 3 O 4 , showing Li+Fe cation disorder. The observed equilibrium concentration for conversion to Fe 0 occurs at x = 4.0. These definitive phase identifications rely heavily on the systematic combined refinement approach, which is broadly applicable to other nanoand mesoscaled systems that have suffered from difficult or crystallite-sizedependent phase identification.