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Sodiation Kinetics of Metal Oxide Conversion Electrodes: A Comparative Study with Lithiation
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posted on 2015-09-09, 00:00 authored by Kai He, Feng Lin, Yizhou Zhu, Xiqian Yu, Jing Li, Ruoqian Lin, Dennis Nordlund, Tsu-Chien Weng, Ryan M. Richards, Xiao-Qing Yang, Marca
M. Doeff, Eric A. Stach, Yifei Mo, Huolin L. Xin, Dong SuThe development of sodium ion batteries
(NIBs) can provide an alternative to lithium ion batteries (LIBs)
for sustainable, low-cost energy storage. However, due to the larger
size and higher m/e ratio of the
sodium ion compared to lithium, sodiation reactions of candidate electrodes
are expected to differ in significant ways from the corresponding
lithium ones. In this work, we investigated the sodiation mechanism
of a typical transition metal-oxide, NiO, through a set of correlated
techniques, including electrochemical and synchrotron studies, real-time
electron microscopy observation, and ab initio molecular dynamics
(MD) simulations. We found that a crystalline Na2O reaction
layer that was formed at the beginning of sodiation plays an important
role in blocking the further transport of sodium ions. In addition,
sodiation in NiO exhibits a “shrinking-core” mode that
results from a layer-by-layer reaction, as identified by ab initio
MD simulations. For lithiation, however, the formation of Li antisite
defects significantly distorts the local NiO lattice that facilitates
Li insertion, thus enhancing the overall reaction rate. These observations
delineate the mechanistic difference between sodiation and lithiation
in metal-oxide conversion materials. More importantly, our findings
identify the importance of understanding the role of reaction layers
on the functioning of electrodes and thus provide critical insights
into further optimizing NIB materials through surface engineering.
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LIBlithium oneslithiationNa 2O reaction layerSodiation Kineticslithium ion batteriesLithiationThe developmentNiO latticecandidate electrodesLi insertionsodiation reactionssodium ion batteriessodiation mechanismNIB materialsreaction layerssurface engineeringsodium ionsMetal Oxide Conversion Electrodesab initio MD simulationsenergy storageNiO exhibitssynchrotron studiesreaction rateelectron microscopy observationsodium ionLi antisite defectsroleComparative Studyab initio
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