Interfacial Properties of Copper-coated Graphite Electrodes: Coating Thickness Dependence

Copper-coated graphite electrodes have been prepared by physical vapour deposition (PVD) and characterised as anodes for Li-ion batteries. The interfacial properties of the electrodes coated with copper layers of different thicknesses have been studied using impedance spectroscopy and com- pared with those of unmodified electrodes. A general enhancement of the performances of the coated electrodes in terms of decreased solid electrolyte interface (SEI) and charge transfer resistances has been found. The charge trans- fer resistance decreases at any intercalation potential for metal layer thickness of the order of 250–300 Å to increase again for thicker deposits. While in general the decrease in the charge transfer resistance may be related to a sort of cata- lytic effect of the metal layer in increasing the lithium deso- lvation rate, it is apparent that above a certain critical thick- ness value the layer acts as a barrier to the lithium ion transfer at the interface.