<p>Using CO₂ as an active material for energy storage is an innovative approach for developing Li–CO₂ batteries. Despite the tremendous potential of Li–CO₂ batteries, their practical deployment is constrained by slow kinetics (leading to high overpotentials) and poor cycle life, primarily due to the sluggish decomposition of the discharge product, Li₂CO₃. To overcome the challenges associated with Li–CO₂ batteries, we synthesized electrospun polyacrylonitrile (PAN)-derived carbon nanofibers (CNF) via electrospinning. The synthesized CNFs were then subjected to hydrothermal treatment for synthesizing hierarchical metallic ruthenium (Ru)-anchored carbon nanofibers (CNF–Ru) for use as a cathode electrocatalyst in Li–CO₂ batteries. The CNF–Ru composite-based cathode exhibited a large specific surface area with numerous catalytically active sites, enhancing reaction rates and efficiency. The Li–CO₂ cell fabricated utilizing the CNF–Ru composite-based cathode exhibited an impressive and consistent charge–discharge performance over 191 cycles at a cutoff capacity of 500 mAh g^–1. To elucidate the origin of this enhancement, first-principles calculations were performed. The calculations revealed that nitrogen in the carbon support critically modulates the electronic structure of the Ru active sites, shifting the d-band center upward toward the Fermi level. This upshift enhances the intrinsic reactivity of the catalyst, facilitating the decomposition of Li₂CO₃ and providing a robust theoretical basis for the observed reduction in charge overpotential and improved cycling stability. This study, combining experimental evidence with theoretical validation, demonstrates the potential of hierarchically structured CNF–Ru nanocomposites for designing high-performance Li–CO₂ batteries.</p> Graphical abstract <p></p>