title: Towards an Understanding of Li2O2Evolution in Li-O2Batteries: An In Operando Synchrotron X-ray Diffraction Study.
abstract: One of the major challenges in developing high-performance Li-O2batteries is to understand the Li2O2formation and decomposition during battery cycling. In this study, this issue was investigated by synchrotron radiation powder X-ray diffraction. The evolution of Li2O2morphology and structure was observed under actual electrochemical conditions of battery operation. By quantitatively tracking Li2O2during discharge and charge, a two-step process was suggested for both growth and oxidation of Li2O2owing to different mechanisms during two stages of both oxygen reduction reaction and oxygen evolution reaction. From an observation of the anisotropic broadening of Li2O2in XRD patterns, it was inferred that disc-like Li2O2grains are formed rapidly in the first step of discharge. These grains can stack together so that they facilitate the nucleation and growth of toroidal Li2O2particles with a LiO2-like surface, which could cause parasitic reactions and hinder the formation of Li2O2. During the charge process, Li2O2is firstly oxidized from the surface, followed by a delithiation process with a faster oxidation of the bulk by stripping the interlayer Li atoms to form an off-stoichiometric intermediate. This fundamental insight brings new information on the working mechanism of Li-O2batteries.
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden.
authors.forename: Chenjuan
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden.
authors.forename: William R
authors.initials: WR
authors.lastname: Brant
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden.
authors.forename: Reza
authors.initials: R
authors.lastname: Younesi
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden.|Beijing Key Laboratory of Lignocellulosic Chemistry, College of Materials Science and Technology, Beijing Forestry University, Beijing, 100083, P.R. China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Dong
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Edström
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden.
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Gustafsson
authors.affiliation: Department of Chemistry-Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden.|State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116024, P.R. China.
authors.forename: Jiefang
authors.identifier: 0000-0002-6326-8106
authors.initials: J
authors.lastname: Zhu
mesh_terms: D011211:Electric Power Supplies; D004566:Electrodes; D008094:Lithium / Q000737:chemistry*; D018020:Lithium Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010545:Peroxides / Q000737:chemistry*; D017356:Synchrotrons; D014961:X-Ray Diffraction
chemical_list: D018020:Lithium Compounds; D010545:Peroxides; D008094:Lithium; D010100:Oxygen
keywords: X-ray diffraction; electrochemistry; lithium peroxide; lithium-oxygen battery; metal-air