Copper-coated Porous Polyimide as Ultralight and Safe Current Collectors for Advanced LIBs

Metallic copper is widely used as current collector (CC) for graphite anode of lithium-ion batteries (LIBs) due to its high electrical conductivity and electrochemical stability. However, the large volume density of commercial copper foil (∼8.9 g·cm −3 ) limits the increase of energy density of battery. Here, copper-coated porous polyimide (Cu@PPI) was prepared by vacuum evaporation as collector for the graphite anode. The sandwich structure connects the copper metal on both sides of the collector with excellent electrical conductivity. Compared to commercial Cu foil, Cu@PPI has lighter mass (≤3.9 mg for disc of 12 mm diameter versus 9.9 mg of ∼10 µm Cu foil) and lower volume density (≤3.3 g·cm −3 ). In addition, the porous structure allows of better adhesion of reactive substances and electrochemical properties than pure Cu foils. It is estimated that the energy density of Cu@PPI should be much higher than that of Cu foil. This strategy should be applicable for other current collectors.