The effect of AlPO4-coating layer on the electrochemical properties in LiCoO2 thin films

AlPO4-coated LiCoO2 thin films showed electrochemical properties superior to those of bare LiCoO2 film. Moreover, the electrochemical properties of the coated LiCoO2 films were affected by the nanostructures of the AlPO4-coating layer, which was deposited at various deposition temperatures. In particular, LiCoO2 coated with AlPO4 deposited at 400 degrees C showed optimal capacity retention. It was found that the AlPO4-coating layer effectively suppressed the increase in the charge-transfer resistance during cycling, as measured by electrochemical impedance spectroscopy. This dependence on the deposition temperature was attributed to the nanostructures of the AlPO4-coating layer, and to interdiffusion at the interface between the LiCoO2 and the nanoscale-coating layer.