B-Site and Oxygen Vacancy Tuning of Free-Standing La_0.8Sr_0.2Ni<i>_x</i>Cu_1–<i>x</i>O₃/Multiwalled Carbon Nanotube Paper for Low Overpotential Long-Cycling Li-CO₂ Batteries

Li-CO2 batteries with unique reaction pathways and high theoretical capacity are powerful tools for addressing greenhouse issues. Thus, it is critical and urgent to develop highly active catalysts for the cathodes of Li-CO2 batteries to promote both CO2 reduction (CRR) and evolution reactions (CER). Herein, La0.8Sr0.2NixCu1–xO3 perovskite is in situ synthesized on multiwalled carbon nanotubes (LSNC/MWCNTs) paper as cathodes of Li-CO2 batteries. The morphology, structure, and electrochemical performance of the as-prepared cathodes are investigated systematically, as well as the reaction products and reversible reaction mechanism. As a result, the Li-CO2 batteries constructed with La0.8Sr0.2Ni0.7Cu0.3O3 (N7C3)/MWCNTs cathode exhibit remarkable electrochemical properties, showcasing a large specific capacity of 16.90 mAh cm–2 at a high specific current of 0.07 mA cm–2, a low overpotential of 0.76 V after 15 cycles rate test, and good cycling stability, maintaining a low overpotential throughout the 500 h of discharge–charging at 0.02 mA cm–2 with a cutoff capacity of 0.1 mAh cm–2 (50 cycles). The superior electrochemical performance of the N7C3/MWCNTs cathodes is attributed to the high Ni3+ content and a large amount of oxygen vacancies caused by the tuning of the atomic ratio on B-sites of perovskite crystals. The results of this work would provide an easy design option for the free-standing cathodes of Li-CO2 batteries and will inspire more original high-performance metal–air batteries.