High-Performance Aprotic Li-CO₂ Battery Enabled by the Ru Heterophase Catalyst

Aprotic Li-CO₂ batteries (LCBs) hold promise for mitigating the greenhouse effect while generating electric power, yet their development remains nascent due to the sluggish CO₂ activation and irreversible discharge product formation, requiring efficient catalysts to address these challenges. Herein, we developed ∼5.5 nm fcc + hcp Ru heterophase nanoparticles on a Ketjen black (KB) matrix (Ru_fcc+hcp/KB) as a dual-functional catalyst for LCBs. X-ray absorption spectroscopy revealed charge redistribution in the fcc + hcp heterophase and under-coordinated Ru sites, which serve as abundant active sites to boost catalytic activity. Theoretical calculations evidenced that the heterophase interface lowers the free energy barriers of the desorption of the *Li₂CO₃ step (*Li₂CO₃ → Li₂CO₃) and the decomposition of the *Li₂C₂O₄ step (*Li₂C₂O₄ → *LiC₂O₄ + Li), facilitating both the nucleation and decomposition of Li₂CO₃. Thus, the Ru_fcc+hcp/KB catalyst exhibited a low overpotential of 0.73 V and long-term cycling stability exceeding 2260 h (at 100 mA g^-1 with a capacity of 1000 mA h g^-1), outperforming Ru_fcc/KB (1.14 V, 1260 h), Ru_hcp/KB (0.90 V, 1480 h), and previously reported Ru-based catalysts. Our findings highlight crystalline phase engineering as an effective strategy to enhance catalytic performance in LCBs.