The fabrication process of porous copper (Cu) current collectors having the pore diameter (3-50 mm) and the rate of opening area (1-4 %) was developed with a system constructed with a pico-second pulse laser and a polygon mirror. The fabricated porous Cu current collectors (Fig. 1) were used to evaluate the porous design on the Cu current collector for exhibiting higher Li⁺ doping reaction rate with cells in which graphite electrodes were laminated with separators and the laminated graphite anode opposites to Li metal through a separator (Fig. 2). It was found in this study that the conditions of hole diameter (5 mm) and the rate of opening area (1%) is the best one to realize high Li⁺ doping rate and that the rate determining step of the pre-doping reaction is the diffusion of Li⁺ion in the pore of the Cu porous current collectors.

Fig. 1 Surface SEM images of prepared porous Cu current collectors. Magnified SEM image of a pore: (A) a view from the plane of incidence of a laser, (B) a view from the plane of emission of a laser. Opening rate of pore on the current collectors: (C) 1 and (D) 2.5 %. The pore size is a constant of 20 mm in all SEM images.

Fig. 2 Schematic description of a cell for pre-doping reaction with graphite layer/porous current collector anodes and a Li metal.