Cupric oxide (CuO) nanoparticles (NPs) with three-dimensional (3D) sponge structure are obtained through the sintering of Cu NPs at 360°C. Their morphology is analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and their crystal structure is checked by X-ray diffraction. CuO NPs have a 3D porous structure. The NPs are assembled to form larger secondary particles with many empty spaces among them, and they have a CuO phase after the heat treatment. CuO NPs with this novel architecture exhibit good electrochemical performance as anode material. The anode material with a sponge-like structure is prepared at 360°C, as the Li-ion battery exhibits a high electrochemical capacity of 674mAhg−1. When the sample is sintered at 360°C, the charge/discharge capacities increase gradually and cycle up to 50 cycles at a C/10 rate, exhibiting excellent rate capability compared with earlier reported CuO/CuO-composite anodes. Electrochemical impedance spectroscopy (EIS) measurements suggest that the superior electrical conductivity of the sample sintered at 360°C is the main factor responsible for the improved power capability.