In situ electrochemical dilatometry (ECD) was performed on Fe3O4/reduced graphene oxide (RGO) nanocomposite during galvanostatic charge and discharge tests in order to investigate the volume change of the metal-oxide/RGO nanocomposites and the role of RGO as a buffering agent in the composite. Fe3O4/RGO nanocomposite with Fe3O4 particles (2-3 nm in size) was successfully prepared through selective heterogeneous precipitation of nanosized Fe3O4 on RGO. A combined analysis of the thickness (t)-change curve of the composite electrode measured via ECD and the differential t-change curve along with the charge/discharge and differential capacity curves clearly indicated the buffering role of RGO in the composite, which exhibited excellent energy efficiency and cycling stability. (C) 2015 The Electrochemical Society.