For advanced applications such as electric vehicles (EV), Li-O₂ batteries are considered as a prospective candidate for next-generation to replace conventional Li-ion batteries. However, the catalytic effect of the redox mediator for oxygen evolution gradually deteriorates during repeated cycling owing to its decomposition at the surfaces of both the oxygen electrode (cathode) and the Li metal electrode (anode).^1,2 Here, we designed optimized Li-O₂ batteries with a continuously effective redox mediator and a stable protective layer for the Li metal electrode by optimizing the LiBr concentration and introducing a graphene–polydopamine composite layer, respectively.³ These synergistic modifications lead to a reduction of the charge potential to below 3.4 V and significantly improved the stability and cycle life of Li–O₂ batteries. Consequently, a high energy efficiency of above 80% was maintained over 150 cycles. Herein, we confirmed that the relationships between all the battery materials should be understood in order to improve the performance of Li-O₂ batteries.

References

1. W.-J. Kwak, D. Hirshberg, D. Sharon, H.-J. Shin, M. Arfi, J.-B. Park, A. Garsuch, F. F. Chesneau, A. A. Frimer, D. Aurbach, Y.-K. Sun, Mater. Chem. A 2015, 3, 8855.
2. W.-J. Kwak, D. Hirshberg, D. Sharon, M. Arfi, A. A. Frimer, H.-G. Jung, D. Aurbach, Y.-K. Sun, Energy Environ. Sci. 2016, 9, 2334.
3. W.-J. Kwak, S.-J. Park, H.-G. Jung, and Y.-K. Sun, Adv. Energy Mater. 2017, 7, 1702258