Improvement of electrochemical properties of natural graphite anode materials with an ovoid morphology by AlPO4 coating

Abstract

AlP O4 -coated natural graphite was prepared by mixing precipitated AlP O4 nanoparticles with natural graphite (NG) powders that had an ovoid morphology in water, followed by vacuum-drying at 150°C for 24 h. This simple coating method did not require any further heat-treatment above 400°C, which is an essential process for the sol-gel driven coating methods (Al2 O3 and Zr O2). The electrochemical properties of the AlP O4 -coated NG were compared with bare and pitch-coated samples and are reported. Impedance analysis revealed that, although the value of the surface film impedance of the AlP O4 -coated sample was 2.4 times larger than the bare NG, its charge-transfer (CT) impedance was 7.5 times smaller than the bare NG. Consequently, we believe that CT was a critical factor that affected the cycle life performance of the sample.