Rational Design of Cu-Free Metal Thin-Film Current Collectors for Balancing Interfacial Resistance and Recyclability

High Resolution Image Download MS PowerPoint Slide As lithium-ion batteries (LIBs) face growing demands for sustainability and resource efficiency, Cu-free, lightweight current collectors have become increasingly important. Ni and Al metal thin films (≤1 μm), deposited onto polymer substrates via electron beam evaporation, were investigated as alternatives to conventional Cu and Al foils. Prototype LIBs employing these thin-film collectors demonstrated a stable electrochemical performance, confirming their practical feasibility. Characterization using sheet resistance measurements, scanning electron microscopy, and electrochemical impedance spectroscopy revealed an increase in interfacial resistance, which was attributed to a decreased electrical conductivity and weakened adhesion arising from the surface characteristics of the thin-film current collectors. Nevertheless, the observed reduction in discharge rate performance remained within an acceptable range. Peel strength tests and ultrasonic delamination experiments further indicated the markedly enhanced separability of electrode composites, particularly in Al-based thin films. These findings demonstrated a rational design trade-off: a moderate reduction in electrical performance was balanced by significant gains in the gravimetric energy density, material efficiency, and recyclability. Overall, metal thin-film current collectors represent a promising strategy for advancing sustainable and resource-conscious LIB technologies.