Sunghyun Ko1,Yiseul Yoo2,Jinkwan Choi2,Hee-Dae Lim2,Chan Beum Park1,Minah Lee2
Korea Advanced Institute of Science and Technology (KAIST)1,Korea Institute of Science and Technology (KIST)2
Sunghyun Ko1,Yiseul Yoo2,Jinkwan Choi2,Hee-Dae Lim2,Chan Beum Park1,Minah Lee2
Korea Advanced Institute of Science and Technology (KAIST)1,Korea Institute of Science and Technology (KIST)2
Li-air batteries (LABs) have received considerable attention as a potential alternative to conventional lithium-ion batteries due to their exceptional energy density (~3,500 Wh/kg) enabled by the reversible conversion reaction between O<sub>2</sub> and Li<sub>2</sub>O<sub>2</sub>. However, current development of ambient air operational LABs is hindered by formation of insulating Li<sub>2</sub>CO<sub>3</sub> during discharge under CO<sub>2</sub>-containing atmosphere. Herein, we provide several p-type redox-active organic molecules that can decompose Li<sub>2</sub>O<sub>2</sub> as a new class of redox mediators (RM) for Li<sub>2</sub>CO<sub>3</sub> decomposition. Through systematic investigation, we successfully demonstrated that the selected RMs possessing a higher redox potential than 3.7 V (vs. Li/Li<sup>+</sup>) can oxidize Li<sub>2</sub>CO<sub>3</sub> with significantly lowered overpotential. The in situ gas analysis further supports the reaction mechanism of RM-catalyzed Li<sub>2</sub>CO<sub>3 </sub>decomposition. Moreover, we firstly report the suppression of highly reactive singlet oxygen (<sup>1</sup>O<sub>2</sub>) generation during RM-catalyzed Li<sub>2</sub>CO<sub>3 </sub>decomposition. We further showed the enhanced cycle life of RM-containing LABs under air-like atmosphere, confirming the compatibility of employing RMs under practical operating conditions. Collectively, our results provide new possibilities for designing multifunctional catalysts to promote the decomposition of major discharge products (Li<sub>2</sub>O<sub>2 </sub>and Li<sub>2</sub>CO<sub>3</sub>) during the ambient air operation of LABs.