nl7b04937_si_006.avi (65.92 kB)
Operando Monitoring of the Solution-Mediated Discharge and Charge Processes in a Na–O2 Battery Using Liquid-Electrochemical Transmission Electron Microscopy
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posted on 2018-01-22, 00:00 authored by Lukas Lutz, Walid Dachraoui, Arnaud Demortière, Lee R. Johnson, Peter G. Bruce, Alexis Grimaud, Jean-Marie TarasconAlthough in sodium–oxygen
(Na–O2) batteries
show promise as high-energy storage systems, this technology is still
the subject of intense fundamental research, owing to the complex
reaction by which it operates. To understand the formation mechanism
of the discharge product, sodium superoxide (NaO2), advanced
experimental tools must be developed. Here we present for the first
time the use of a Na–O2 microbattery using a liquid
aprotic electrolyte coupled with fast imaging transmission electron
microscopy to visualize, in real time, the mechanism of NaO2 nucleation/growth. We observe that the formation of NaO2 cubes during reduction occurs by a solution-mediated nucleation
process. Furthermore, we unambiguously demonstrate that the subsequent
oxidation of NaO2 of which little is known also proceeds
via a solution mechanism. We also provide insight into the cell electrochemistry
via the visualization of an outer shell of parasitic reaction product,
formed through chemical reaction at the interface between the growing
NaO2 cubes and the electrolyte, and suggest that this process
is responsible for the poor cyclability of Na–O2 batteries. The assessment of the discharge–charge mechanistic
in Na–O2 batteries through operando electrochemical
transmission electron microscopy visualization should facilitate the
development of this battery technology.
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imaging transmission electron microscopyOperando MonitoringNaO 2solution mechanismreaction productNaO 2 cubesdischarge productsodium superoxideCharge ProcessesLiquid-Electrochemical Transmission Electron Microscopyoperando electrochemical transmission electron microscopy visualizationchemical reactionbattery technologystorage systemsSolution-Mediated Dischargesolution-mediated nucleation processformation mechanismcell electrochemistrybatteries show promiseaprotic electrolyte
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