固体核磁共振研究单斜磷酸钒锂的进展（英文）.docx

固体核磁共振研究单斜磷酸钒锂的进展（英文）
ProgressinSolid-stateNuclearMagneticResonanceStudiesofLiVPO4F
Introduction:
Lithiumvanadiumfluorophosphate(LiVPO4F)isapromisingcathodematerialforrechargeablelithium-ionbatteries.However,itsstructuralcomplexityanddisorderposeachallengeforunderstandingitsfunctionalproperties.Solid-statenuclearmagneticresonance(NMR)techniqueshavebeenwidelyemployedtoinvestigateandcharacterizethelocalenvironmentsanddynamicsofLiVPO4F.Inthispaper,wesummarizetherecentprogressinsolid-stateNMRstudiesofLiVPO4F.
BasicStructuralCharacteristics:
LiVPO4FhasamonoclinicstructurewithspacegroupC2/c.Thevanadium(V)ionsoccupytwocrystallographicallydistinctsites,V(1)andV(2),whilethephosphorus(P)andfluorine(F)ionsarelocatedatoctahedralsitesandthelithium(Li)ionsarefoundintetrahedralsites.Thearrangementoftheseionsintheunitcellleadstotheexistenceofvariouslocalstructuraldistortionsanddisorder.
NMRTechniquesUsed:
Solid-stateNMRexperimentshavebeenextensivelyusedtoinvestigatethelocalstructuralanddynamicpropertiesofLiVPO4F.ThemostcommonlyusedNMRtechniquesinthesestudiesincludemagicanglespinning(MAS)NMR,cross-polarizationMAS(CP-MAS)NMR,andtwo-dimensional(2D)NMR.
MagicAngleSpinningNMR:
MASNMRexperimentsprovideinformationaboutthelocalsymmetryandchemicalshiftsoftheatomsinthesolid-statesamples.MASNMRspectraofLiVPO4FhaveshownthattheV(1)andV(2)sitesexhibitdistinctpeaksowingtotheirdifferentlocalenvironments.Thechemicalshiftanisotropiesofthesesitesaresignificantlydifferent,andthisdifferencehasbeenattributedtotheJahn-TellerdistortionoftheV(1)site.ThePandFsitesalsoexhibitdistinctpeaksintheMASNMRspectra,highlightingthestructuraldisorderinLiVPO4F.
Cross-polarizationMASNMR:
CP-MASNMRexperimentsprovideinformationonthedipolarinteractionsbetweenthenucleiinthesampleandhavebeenusedtostudythedynamicsofLiVPO4F.TheLiionsareknowntobemobileinLiVPO4F,andtheirmobilityhasbeenstudiedusingCP-MASNMRexperiments.TheresultsoftheseexperimentshaveshownthattheLiionsexhibitisotropicmotionuptoroomtemperature.
Two-dimensionalNMR:
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