Novel massif-like Cu x O nanostructure was directly growing on Cu foam via a facile thermal oxidation method in air atmosphere. The massifs are about 5μm in mean diameter and 4μm in mean height, which consist of a large number of nanoparticles with mean size about 100nm. Cu x O nanowires that evolve from the particles locate at the laps of the massifs. Galvanostatic battery testing shows that the Cu x O/Cu electrode exhibits excellent cycle stability and rate capability. The charge and discharge capacities are both 1.8mAhcm−2 after 100 cycles under a discharge/charge rate of 0.35C. After testing at various rates from 0.2 to 12C over 50 cycles, the 5th-cycle discharge capacity can resume well when lowering the discharge/charge rate to 0.2C. The performances are testified due to a novel electrochemical activation effect that induces the reconstruction of porous forest-like morphology in cycling.