title: Dissolution and ionization of sodium superoxide in sodium-oxygen batteries.
abstract: With the demand for high-energy-storage devices, the rechargeable metal-oxygen battery has attracted attention recently. Sodium-oxygen batteries have been regarded as the most promising candidates because of their lower-charge overpotential compared with that of lithium-oxygen system. However, conflicting observations with different discharge products have inhibited the understanding of precise reactions in the battery. Here we demonstrate that the competition between the electrochemical and chemical reactions in sodium-oxygen batteries leads to the dissolution and ionization of sodium superoxide, liberating superoxide anion and triggering the formation of sodium peroxide dihydrate (Na2O2·2H2O). On the formation of Na2O2·2H2O, the charge overpotential of sodium-oxygen cells significantly increases. This verification addresses the origin of conflicting discharge products and overpotentials observed in sodium-oxygen systems. Our proposed model provides guidelines to help direct the reactions in sodium-oxygen batteries to achieve high efficiency and rechargeability.
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Jinsoo
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Hyeokjun
authors.initials: H
authors.lastname: Park
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.|Center for Nanoparticle Research at Institute for Basic Science, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Byungju
authors.initials: B
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Won Mo
authors.initials: WM
authors.lastname: Seong
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Hee-Dae
authors.initials: HD
authors.lastname: Lim
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Youngjoon
authors.initials: Y
authors.lastname: Bae
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.|Center for Nanoparticle Research at Institute for Basic Science, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Haegyeom
authors.initials: H
authors.lastname: Kim
authors.affiliation: Environment and Energy Research Team, Division of Automotive Research and Development, Hyundai Motor Company, 37 Cheoldobangmulgwan-ro, Uiwang, Gyeonggi-do 437-815, Republic of Korea.
authors.forename: Won Keun
authors.initials: WK
authors.lastname: Kim
authors.affiliation: Environment and Energy Research Team, Division of Automotive Research and Development, Hyundai Motor Company, 37 Cheoldobangmulgwan-ro, Uiwang, Gyeonggi-do 437-815, Republic of Korea.
authors.forename: Kyoung Han
authors.initials: KH
authors.lastname: Ryu
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.|Center for Nanoparticle Research at Institute for Basic Science, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: Kisuk
authors.initials: K
authors.lastname: Kang