Chloride-regulated Cu_xO/RuCu heterostructure electrocatalyst towards high-performance Li-CO₂ batteries

Lithium-carbon dioxide (Li-CO₂) batteries have attracted extensive attention since they provide a distinctive approach to mitigate CO₂ accumulation and simultaneously deliver high-energy-density electricity. However, an abnormally high voltage is usually applied to decompose lithium carbonate (Li₂CO₃) discharge products in a reversible charge direction, which leads to low energy efficiency and poor reversibility, thereby seriously hindering the advancement of Li-CO₂ batteries. Herein, a novel chloride-regulated Cu_xO/RuCu heterostructure (Cu_xO-Cl/RuCu) electrocatalyst is designed and prepared for considerably reducing the decomposition barrier of Li₂CO₃ in Li-CO₂ batteries. Cu_xO-Cl/RuCu is characterized by a porous octahedral microstructure with numerous Cu^δ+/Cu⁰ heterointerfaces modified by both non-metallic Cl and metallic Ru. Thus, the Cu_xO-Cl/RuCu electrocatalyst with a downshifted d-band center exhibits a boosted electrocatalytic decomposition ability towards Li₂CO₃. The Li-CO₂ battery with Cu_xO-Cl/RuCu displays a large discharge capacity of 8041.73 μAh cm^-2, a durable cycling performance of 180 cycles, and an impressive rate capability at 200 μA cm^-2, outperforming its Cu₂O counterpart. The diverse characterizations after charge-discharge periods and systematic theoretical calculations further confirm the superb electrocatalytic ability and durability of Cu_xO-Cl/RuCu for Li₂CO₃ decomposition. Notably, these results offer new insights into the previously unknown role of chloride residues and a strategy to improve the performance of Cu-based electrocatalysts for Li-CO₂ batteries.