Li4P2O7-stabilized LiNi0.5Mn1.5O4 was prepared by solid-state synthesis. The material was characterized by X-ray diffraction and high-resolution transition electron microscopy, which showed a coating layer (<10nm) of Li4P2O7 crystallite co-existing with a little Li3PO4 on the LiNi0.5Mn1.5O4/Li4P2O7 primary particles. LiNi0.5Mn1.5O4/Li4P2O7 synthesized at 760°C for 200h had a cubic spinel structure with a space group of Fd 3 ¯ m; its estimated crystallite size was 527nm. LiNi0.5Mn1.5O4/Li4P2O7 possessed better rate capability and cycling capability. The introduced Li4P2O7 coating layer acted as a solid electrolyte or artificial SEI layer: by separating the active material from the electrolyte, the coating layer prevented the Ni2+/Ni3+ or Ni3+/Ni4+ redox couple from decomposing the electrolyte. Stress/strain from the Ni2+⇌Ni3⇌Ni4+ spinel phase change caused fractures and pulverization of the cycled stoichiometric LiNi0.5Mn1.5O4 crystal surface, especially noticeable for this well-developed micro-sized crystal. The ordered stoichiometric LiNi0.5Mn1.5O4 had more side reactions, led to a quick fading of the material's capacity. Both the Li4P2O7 coating layer and the disordered Fd 3 ¯ m space group LiNi0.5Mn1.5O4 structure bring benefit to the LiNi0.5Mn1.5O4/Li4P2O7 performance. Thus, the introduced Li4P2O7 coating layer can build an effective solid electrolyte or artificial SEI layer to protect the interface between LiNi0.5Mn1.5O4 and electrolyte.