LiNi0.5Mn1.5O4 (LNMO) nanostructures (microspheres composed of nanoparticles) are prepared from urchin-like gamma-MnO2 by calcinating under 800 degrees C, the product shows Fd3m-based phase involving minor rock salt phase and Mn3+ ions confirmed by its Raman spectra, X-ray diffraction pattern and electrochemical activities. Furthermore, HRTEM images and EDS line-scanning spectroscopy patterns focusing on a single nanoparticle provide direct observation of intergrowth of two phases that minor P4(3)32 phase is found on the edge of Fd3 m body coupled with the varying Mn/Ni ratio. In comparison, the other sample is obtained by adding an annealing treatment at 700 degrees C after calcinating at 800 degrees C, which preserves the nanostructured architecture of C800 and displays all the structural characteristics of pure P4(3)32 phase. As cathode materials for lithium-ion batteries, merely calcined sample receives discharge capacities of 91 mAh.g(-1) even at 50 C, and 100.5 mAh.g(-1) after 300 cycles at 5 C, which shows better combination of rate and cycling performances than its counterpart with pure P4(3)32 phase. (C) 2014 Elsevier Ltd. All rights reserved.