Long-life reversible Li-CO₂ batteries with optimized Li₂CO₃ flakes as discharge products on palladium-copper nanoparticles

Li-CO₂ batteries have attracted lots of attention owing to their high working potential and large theoretical energy density, while they still suffer from the sluggish kinetics of CO₂ reduction and evolution reactions. Previous research studies on catalysts for photo/electrochemical CO₂ reduction have inspired the potential application of copper-based catalysts in Li-CO₂ batteries. However, metallic Cu is easy to be oxidized and forms a passivation layer, leading to decreased active sites. Here, we demonstrate PdCu decorated nitrogen doped carbon nanofiber (PdCu/N-CNF) as a stable and efficient cathode for high-performance Li-CO₂ batteries. The PdCu/N-CNF cathode delivers a large discharge capacity of 18 550 mA h g⁻¹ at 100 mA g⁻¹, and cycles for 1350 h with the lowest discharge/charge polarization of 1.17 V in a limited capacity of 1000 mA h g⁻¹ at 400 mA g⁻¹. The ex situ analysis shows that flake-like Li₂CO₃ is formed through conformal growth instead of large bulk particles. Besides, the oxidation of Cu in the PdCu/N-CNF cathode has been effectively suppressed during the discharge/charge process. Therefore, bimetallic alloys can not only enhance the stability of Cu-based metal materials, but also improve the catalytic properties with the synergistic effect of the two elements.