Fabrication of FePO4 layer coated LiNi1/3Co1/3Mn1/3O2: Towards high-performance cathode materials for lithium ion batteries

FePO4 coated LiNi1/3Co1/3Mn1/3O2 showed an improved cycle and rate capacities. The FePO4 coating layer significantly suppressed the increase of charge-transfer resistance (Rct) upon cycling and reduced the activation energy of the charge transfer processes. The surface of layered LiNi1/3Co1/3Mn1/3O2 was coated with nano-layer FePO4 by co-precipitation method and followed by heat treatment. The prepared samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). FePO4 coated samples exhibited both improved rate and cycle capacity compared with the pristine LiNi1/3Co1/3Mn1/3O2. The capacity retention after 100 cycles increased from 62.0% to 87.7%. The sample coated with 2wt% FePO4 and treated at 400°C showed the optimum cyclability. The electrochemical impedance spectroscopy (EIS) results indicated that the FePO4 coating layer significantly suppressed the increase of charge-transfer resistance (Rct). The activation energy of the charge transfer processes at the electrode/electrolyte interface was reduced by FePO4 coating. Differential scanning calorimetry analysis showed the FePO4 coating improved the thermal stability of the cathode material.