Lowering charge potential of Li-O2 battery to 3.25 V through a facile lithiation of Pd-CN cathode catalyst

Abstract

Li-O2 batteries have attracted much attention due to their high energy density. However, the high charging potential (∼4.5 V) causes serious side reactions and safety issues, which are also accompanied by a low round-trip efficiency and poor cycle life. Designing catalysts is one of the most adopted strategies to decrease the charging potential. But the effects of lowering the charging potential are quite limited. Herein, we propose a distinct strategy of electrochemical lithiation of Pd-CN to significantly reduce the overpotential of Li-O2 batteries from 4.28 V to 3.25 V and reveal the underlying catalysis mechanism. The lithiation promotes the formation of N defects in C3N4 and the alloying of Li-Pd, which improves the conductivity of the catalyst and increases the number of active sites. This promotes the oxygen evolution reaction and decreases the overpotential. Theoretical calculations are further used to prove that the electrochemically tuned Pd-CN with nitrogen vacancies exhibits weak adsorption energy for LiO2, enabling a significant reduction in the charge potential. This study proposes a distinct and facile strategy to address the overpotential issue in Li-O2 batteries.