AlPO4 nanoparticles were synthesized via chemical deposition method and used for the surface modification of MoO2 to improve its structural stability and electrochemical performance. Structure and surface morphology of pristine and AlPO4-coated MoO2 anode material were characterized by electron microscopy imaging (SEM and TEM) and X-ray diffraction (XRD). AlPO4 nanoparticles were observed, covering the surface of MoO2. Surface analyses show that the synthesized AlPO4 is amorphous, and the surface modification with AlPO4 does not result in a distortion of the lattice structure of MoO2. The electrochemical properties of pristine and AlPO4-coated MoO2 were characterized in the voltage range of 0.01–2.5？V versus Li/Li+. Cyclic voltammetry studies indicate that the improvement in electrochemical performance of the AlPO4-coated anode material was attributed to the stabilization of the lattice structure during lithiation. Galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) studies reveal that the AlPO4 nanoparticle coating improves the rate capability and cycle stability and contributes toward decreasing surface layer and charge-transfer resistances. These results suggest that surface modification with AlPO4 nanoparticles suppresses the elimination of oxygen vacancies in the lattice structure during cycling, leading to a better rate performance and cycle life. 1. Introduction Lithium ion batteries are extensively used in a variety of portable electronic devices due to their high power density and long cycle life [1]. As reported, they are critically important for electric/hybrid vehicles as the power storage of the future [2]. Therefore, lithium ion batteries have attracted much interest in the field of fundamental study and applied research. Most commercialized lithium ion batteries use graphite as an anode material due to its accessibility and low cost; but its theoretical capacity is only 372？mAh g？1 calculated by forming the compound of LiC6 and cannot meet the ever-increasing demands for high capacity lithium ion technology [3]. By replacing graphite with transition metal oxides as anode materials, the capacity is enhanced. This is due to their close packed oxygen array, providing a framework structure and specific site for topotactic insertion and removal of lithium ions during charge/discharge process. A number of transition metal oxides have been studied and reported so far, including Mn3O4, Co3O4, MnO, TiO2, NiO, MoO2, and SnO2, because of their possibility of various oxidation states and the search of new materials for
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