title: Hierarchical Porous Carbon Spheres for High-Performance Na-O2Batteries.
abstract: As a new family member of room-temperature aprotic metal-O2batteries, Na-O2batteries, are attracting growing attention because of their relatively high theoretical specific energy and particularly their uncompromised round-trip efficiency. Here, a hierarchical porous carbon sphere (PCS) electrode that has outstanding properties to realize Na-O2batteries with excellent electrochemical performances is reported. The controlled porosity of the PCS electrode, with macropores formed between PCSs and nanopores inside each PCS, enables effective formation/decomposition of NaO2by facilitating the electrolyte impregnation and oxygen diffusion to the inner part of the oxygen electrode. In addition, the discharge product of NaO2is deposited on the surface of individual PCSs with an unusual conformal film-like morphology, which can be more easily decomposed than the commonly observed microsized NaO2cubes in Na-O2batteries. A combination of coulometry, X-ray diffraction, and in situ differential electrochemical mass spectrometry provides compelling evidence that the operation of the PCS-based Na-O2battery is underpinned by the formation and decomposition of NaO2. This work demonstrates that employing nanostructured carbon materials to control the porosity, pore-size distribution of the oxygen electrodes, and the morphology of the discharged NaO2is a promising strategy to develop high-performance Na-O2batteries.
authors.affiliation: Centre for Clean Energy Technology, University of Technology Sydney, Broadway, Sydney, NSW, 2007, Australia.
authors.forename: Bing
authors.identifier: http://orcid.org/0000-0002-4365-486X
authors.initials: B
authors.lastname: Sun
authors.affiliation: Centre for Clean Energy Technology, University of Technology Sydney, Broadway, Sydney, NSW, 2007, Australia.
authors.forename: Katja
authors.initials: K
authors.lastname: Kretschmer
authors.affiliation: Centre for Clean Energy Technology, University of Technology Sydney, Broadway, Sydney, NSW, 2007, Australia.
authors.forename: Xiuqiang
authors.initials: X
authors.lastname: Xie
authors.affiliation: School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Munroe
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Science, Changchun, Jilin, 130022, China.
authors.forename: Zhangquan
authors.initials: Z
authors.lastname: Peng
authors.affiliation: Centre for Clean Energy Technology, University of Technology Sydney, Broadway, Sydney, NSW, 2007, Australia.
authors.forename: Guoxiu
authors.initials: G
authors.lastname: Wang
keywords: porous carbon electrodes; sodium superoxide; sodium-oxygen batteries