Electrodeposition of Lithium in Polystyrene Sphere Opal Structures on Copper from an Ionic Liquid

In this paper we report on the electrodeposition of lithium on a polystyrene sphere modified electrode from an ionic liquid. By a simple dipping process, polystyrene (PS) spheres with an average diameter of 600 nm arrange in a hexagonal close packed structure onto an electrode surface. Surprisingly, lithium does not grow uniformly from the electrode surface to the electrolyte within the voids of the PS structure. Depending on the experimental conditions a more or less good inverse opal structure made of lithium, lithium spheres or hollow lithium half-spheres can be obtained showing that the growth of lithium in the employed ionic liquid is more complicated than expected. Somehow lithium tends to push away the PS spheres during growth. Applying a slight mechanical pressure on the PS spheres during deposition improves the growth within the voids of the opal structure. Despite this complicated behaviour the PS opal structure seems to suppress a vertical dendritic growth, thus, a lithium/PS composite electrode or other lithium/polymer composite electrodes might be of some interest in rechargeable lithium metal microbatteries where a dendritic vertical growth has to be avoided.