Alkali metal-modified P2 NaxMnO2: crystal structure and application in sodium-ion batteries

dc.contributor.authorSehrawat, Den_AU
dc.contributor.authorRawal, Aen_AU
dc.contributor.authorCheong, Sen_AU
dc.contributor.authorAvdeev, Men_AU
dc.contributor.authorLing, CDen_AU
dc.contributor.authorKimpton, JAen_AU
dc.contributor.authorSharma, Nen_AU
dc.description.abstractSodium-ion batteries (NIBs) are an emerging alternative to lithium-ion batteries because of the abundance of sodium resources and their potentially lower cost. Here we report the Na0.7MnO2 solid state synthesized at 1000 °C that shows two distinct phases; one adopts hexagonal P2-type P63/mmc space group symmetry, and the other adopts orthorhombic Pbma space group symmetry. The phase ratio of P2 to the orthorhombic phase is 55.0(5):45.0(4). A single-phase P2 structure is found to form at 1000 °C after modification with alkali metals Rb and Cs, while the K-modified form produces an additional minor impurity. The modification is the addition of the alkali elements during synthesis that do not appear to be doped into the crystal structure. As a cathode for NIBs, parent Na0.7MnO2 shows a second charge/discharge capacity of 143/134 mAh g–1, K-modified Na0.7MnO2 a capacity of 184/178 mAh g–1, Rb-modified Na0.9MnO2 a capacity of 159/150 mAh g–1, and Cs-modified Na0.7MnO2 a capacity of 171/163 mAh g–1 between 1.5 and 4.2 V at a current density of 15 mA g–1. The parent Na0.7MnO2 is compared with alkali metal (K, Rb, and Cs)-modified NaxMnO2 in terms of surface morphology using scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy, scanning electron microscopy, 23Na solid-state nuclear magnetic resonance, and X-ray photoelectron spectroscopy and in terms of electrochemical performance and structural electrochemical evolution using in situ or operando synchrotron X-ray diffraction. © 2020 American Chemical Societyen_AU
dc.identifier.citationSehrawat, D., Rawal, A., Cheong, S., Avdeev, M., Ling, C. D., Kimpton, J. A., & Sharma, N. (2020). Alkali metal-modified P2 NaxMnO2: crystal structure and application in sodium-ion batteries. Inorganic Chemistry, 59(17), 12143-12155. doi:10.1021/acs.inorgchem.0c01078en_AU
dc.identifier.journaltitleInorganic Chemistryen_AU
dc.publisherAmerican Chemical Societyen_AU
dc.subjectCrystal latticesen_AU
dc.subjectTransition elementsen_AU
dc.subjectAlkali metalsen_AU
dc.subjectTransmission electron microscopyen_AU
dc.subjectX-ray diffractionen_AU
dc.subjectElectric batteriesen_AU
dc.titleAlkali metal-modified P2 NaxMnO2: crystal structure and application in sodium-ion batteriesen_AU
dc.typeJournal Articleen_AU
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