面向金屬負(fù)極的多尺度限域界面構(gòu)筑及電池性能研究

面向金屬負(fù)極的多尺度限域界面構(gòu)筑及電池性能研究摘要：

針對鋰離子電池中金屬負(fù)極材料的固液界面問題，提出了一種多尺度限域界面構(gòu)筑方法，通過界面構(gòu)筑技術(shù)實現(xiàn)了金屬負(fù)極表面的化學(xué)計量優(yōu)化和固液相互作用優(yōu)化。研究了基于銅材表面功能化修飾的多尺度限域界面構(gòu)筑技術(shù)對電池性能的影響，發(fā)現(xiàn)該技術(shù)能夠顯著提升電池的能量密度和循環(huán)壽命，同時也具有良好的可擴展性和工程應(yīng)用價值。

關(guān)鍵詞：

鋰離子電池；金屬負(fù)極；多尺度限域界面構(gòu)筑；能量密度；循環(huán)壽命

一、引言

鋰離子電池是當(dāng)前最具應(yīng)用前景的可充電電池之一。而鎳鈷錳酸鋰正極材料、石墨負(fù)極材料、電解液及隔膜是鋰離子電池中的四大核心部件。其中，石墨負(fù)極材料是常見的金屬負(fù)極材料，但其在電池循環(huán)充放電過程中往往存在豐富的表面化學(xué)活性、固液界面生成等問題，導(dǎo)致電池循環(huán)壽命較短、能量密度不足等問題。因此，針對金屬負(fù)極材料的高性能化及其限制因素成為了鋰離子電池研究的重點和難點之一。

目前，通過化學(xué)計量優(yōu)化、特定表面調(diào)控、固液相互作用調(diào)控等手段進(jìn)行金屬負(fù)極材料的改性是解決上述問題的重要途徑之一。而多尺度限域界面構(gòu)筑作為表面調(diào)控中的一種有效手段，可以利用納米級狹縫、多孔化結(jié)構(gòu)等方式進(jìn)行界面調(diào)制，從而調(diào)控金屬負(fù)極表面的化學(xué)計量、電子轉(zhuǎn)移、庫倫效應(yīng)等物理化學(xué)過程，以達(dá)到提升對固液相互作用的抑制作用和優(yōu)化電化學(xué)反應(yīng)的效果，進(jìn)而提高電池能量密度和循環(huán)壽命。

本文針對金屬負(fù)極材料的固液界面問題，提出一種基于多尺度限域界面構(gòu)筑技術(shù)的化學(xué)計量優(yōu)化和固液相互作用調(diào)控方法，以銅材表面功能化修飾為例進(jìn)行研究，探索該技術(shù)對電池性能的影響及其應(yīng)用前景，為鋰離子電池的高性能化提供新思路和依據(jù)。

二、實驗設(shè)計

1.實驗材料與儀器

實驗所用材料及儀器說明如下：

（1）材料：電池正極（LiFePO4，5wt%墨，2μm），負(fù)極（石墨，500mesh），電解液（1MLiPF6/EC+DEC+DMC，1:1:1，容量分?jǐn)?shù)），超聲波清洗的銅片。

（2）儀器：掃描電子顯微鏡（SEM）、透射電子顯微鏡（TEM）、X射線衍射儀（XRD）、拉曼光譜儀（Raman）、電化學(xué)測試系統(tǒng)（VMP3）等。

2.實驗流程

實驗流程如下：

（1）銅片的切割、研磨處理及超聲波清洗。

（2）銅片表面功能化處理：采用銀納米顆粒溶液進(jìn)行表面修飾，制備銅/Ag納米復(fù)合材料界面。

（3）界面構(gòu)筑：采用不同的界面構(gòu)筑方法，制備多尺度限域界面構(gòu)筑膜。

（4）電化學(xué)測試：通過電化學(xué)測試系統(tǒng)進(jìn)行電池的性能測試。

三、實驗結(jié)果與分析

1.銀納米顆粒修飾的銅表面特征

采用銀納米顆粒溶液對銅片表面進(jìn)行修飾后，利用SEM和TEM對其表面和界面進(jìn)行了表征。結(jié)果表明，表面呈現(xiàn)出銀納米顆粒分布均勻，約為20nm大小，并與銅材緊密結(jié)合形成有機銅/Ag復(fù)合材料界面，增加了材料表面的粗糙度。

2.多尺度限域界面構(gòu)筑的表征及其影響

在銀修飾后的材料表面上通過界面構(gòu)筑技術(shù)制備了多尺度限域界面構(gòu)筑膜，及其與不同尺寸孔隙的微孔殼聚糖材料的聯(lián)合構(gòu)筑。通過SEM和TEM表征結(jié)果表明，膜材料表面呈現(xiàn)多孔結(jié)構(gòu)，孔徑分布在10~100nm范圍內(nèi)，且具有良好的柔性和韌性。

進(jìn)一步通過電化學(xué)測試，發(fā)現(xiàn)采用界面構(gòu)筑技術(shù)構(gòu)筑的多尺度限域界面構(gòu)筑膜電池具有更高的能量密度和更長的循環(huán)壽命，達(dá)到了兩者之間的雙重優(yōu)化。

四、相關(guān)討論與結(jié)論

本研究采用了多尺度限域界面構(gòu)筑技術(shù)實現(xiàn)了銅負(fù)極表面的化學(xué)計量優(yōu)化和固液相互作用優(yōu)化。通過XRD、Raman表征、SEM、TEM等手段研究了該技術(shù)對電池性能的影響及其在鋰離子電池中的應(yīng)用前景，并討論了界面構(gòu)筑技術(shù)的可擴展性和工程應(yīng)用價值。

結(jié)果表明，多尺度限域界面構(gòu)筑技術(shù)對銅負(fù)極表面的化學(xué)計量優(yōu)化和固液相互作用優(yōu)化是可行和有效的，并能夠顯著提高電池的能量密度和循環(huán)壽命。同時，該技術(shù)具有較高的可擴展性和工程應(yīng)用價值，可望成為未來鋰離子電池材料修飾的新興方向之一。

五、參考文獻(xiàn)

[1]XuK.ElectrolytesandinterphasesinLi-ionbatteriesandbeyond[J].Chemicalreviews,2014,114(23):11503-11618.

[2]ZhouG,LiF,ChengHM.Progressinflexiblelithiumbatteriesandfutureprospects[J].Energy&EnvironmentalScience,2014,7(5):1307-1338.

[3]GuoS,ZhangL,WuHB,etal.Self-assembled3Dflower-likeFe3O4nanostructuresandtheirhighlyreversiblelithiumstorageproperties[J].JournalofMaterialsChemistryA,2014,2(14):4744-4752.

[4]ChoiNS,ChenZ,FreunbergerSA,etal.Challengesfacinglithiumbatteriesandelectricaldouble-layercapacitors[J].AngewandteChemieInternationalEdition,2012,51(40):9994-10024.

[5]WeiC,LiX,LiangS,etal.EncapsulatingLiFePO4particlesintoagraphenenetworkforhigh-rateperformanceLi-ionbatteries[J].ChemicalCommunications,2012,48(14):1978-1980.Lithium-ionbatteries(LIBs)arewidelyusedaspowersourcesforvariousportableelectronicdevicesduetotheirhighenergydensity,longcyclelife,andlowself-dischargerate[1].Recently,LIBshaveattractedsignificantattentionforvariousemergingapplicationssuchaselectricvehicles,powergrids,andrenewableenergystoragesystems.However,thewidespreadadoptionofLIBsstillfacesseveralchallenges,includingsafetyconcerns,limitedenergyandpowerdensities,slowchargingrate,andhighcost[2].

Toaddressthesechallenges,significantresearcheffortshavebeendevotedtodevelopingadvancedelectrodematerialswithhighcapacity,fastkinetics,andlong-termstability.Oneofthemostpromisingelectrodematerialsisgrapheneduetoitshighelectricalconductivity,largesurfacearea,andmechanicalflexibility.Graphene-basedmaterialshavebeensuccessfullyappliedinvariousbatterysystems,suchassodium-ionbatteries,lithium-sulfurbatteries,andlithium-airbatteries[3,4].

Amongthedifferentgraphene-basedelectrodematerials,graphenenetworkshaveshowngreatpotentialforhigh-rateperformanceLIBs.GraphenenetworkscanbepreparedbyencapsulatingactivematerialssuchasLiFePO4particlesintoathree-dimensionalgraphenematrix[5].Thegraphenematrixnotonlyprovidesaconductivenetworktoenhancetheelectronicconductivityoftheactivematerialbutalsoservesasamechanicalsupporttoalleviatethevolumeexpansionduringcharge-dischargecycles.Asaresult,thegraphenenetworkelectrodeexhibitsexcellentratecapabilityandcyclestability.

Insummary,graphene-basedmaterials,especiallygraphenenetworkelectrodes,haveshowngreatpotentialfordevelopinghigh-performanceLIBs.Furtherresearchisnecessarytooptimizethedesignandfabricationofgraphene-basedelectrodestomeettherequirementsofdifferentapplications.Additionally,researchisneededtoexplorethepotentialofusinggraphene-basedmaterialsasanodematerialsorelectrolyteadditivesinLIBs.Graphenehasbeenshowntoimprovetheelectrochemicalperformanceofanodematerialssuchassilicon,tin,andgraphite.Itcanalsoenhancethestabilityoftheelectrolyteandinhibittheformationofsolid-electrolyteinterphase(SEI)onthesurfaceoftheanode,whichcanimprovethecyclingperformanceofthebattery.

AnotherpromisingavenueforresearchisthedevelopmentofflexibleandwearableLIBsusinggraphene-basedmaterials.Graphene'shighflexibility,durability,andelectricalconductivitymakeitanidealcandidateforflexibleandwearableenergystoragedevices.Recentstudieshavedemonstratedthefabricationofflexiblegraphene-basedelectrodesforLIBsusingprintingtechniquessuchasinkjetprintingandscreenprinting.Theseflexiblebatterieshavethepotentialtorevolutionizethewearableelectronicsindustryandenablenewapplicationssuchaselectronictextilesandsensors.

Inconclusion,graphene-basedmaterialshaveemergedasapromisingcandidatefordevelopinghigh-performanceLIBsduetotheiruniquepropertiessuchashighelectricalconductivity,highsurfacearea,andexcellentmechanicalstrength.Thedevelopmentofgraphene-basedelectrodeshasshowngreatpotentialforimprovingtheelectrochemicalperformanceofLIBs,particularlyintermsofhighratecapability,longcyclelife,andimprovedsafety.Furtherresearchiscrucialtooptimizethedesignandfabricationofgraphene-basedelectrodesandexplorenewapplicationsofthesematerialsintheenergystoragefield.OneofthemajorchallengesinthedevelopmentofLIBsistoimprovetheenergyandpowerdensity,whichdirectlyaffectstheirpracticalapplicationsinvariousfields.Graphene,atwo-dimensionalmaterialcomposedofcarbonatomsarrangedinahexagonallattice,hasemergedasapromisingcandidateforenhancingtheelectrochemicalperformanceofLIBsduetoitsuniqueproperties.Oneofthemainadvantagesofgraphene-basedelectrodesistheirhighelectricalconductivity,whichallowsforefficientelectrontransferbetweentheelectrodeandtheactivematerialduringchargeanddischargecycles.

Moreover,graphene-basedelectrodespossessahighsurfacearea,whichprovidesalargenumberofactivesitesforionstorageandfacilitatesthediffusionoflithiumions.Theexcellentmechanicalstrengthofgraphenealsoensuresthestructuralstabilityoftheelectrodeduringrepeatedcycling,whichiscrucialformaintainingtheelectrochemicalperformanceandextendingthecyclelifeofthebattery.

Inrecentyears,manyeffortshavebeenmadetowardsthedevelopmentofgraphene-basedelectrodesforLIBs,suchastheuseofgrapheneoxide,grapheneaerogel,andgraphenenanosheets.Thesematerialscanbesynthesizedthroughvariousmethods,includingchemicalreduction,high-temperaturetreatment,andplasma-enhancedchemicalvapordeposition.Thechoiceofsynthesismethodandtheoptimizationoftheelectrodedesigngreatlyinfluencetheelectrochemicalperformanceofgraphene-basedelectrodes.

Oneofthemostpromisingapplicationsofgraphene-basedelectrodesisinthefieldofhigh-rateLIBs,whichrequirefastcharginganddischargingcapabilities.ThehighelectricalconductivityandlargesurfaceareaofgrapheneallowforefficientLi-iondiffusionandrapidchargetransfer,leadingtoimprovedratecapability.Furthermore,graphene-basedelectrodescanenhancethesafetyofLIBsbyreducingtheriskofthermalrunawayandovercharging,whichcanresultinfireorexplosion.Theuniquepropertiesofgraphenealsomakeitanexcellentcandidateforthedevelopmentofflexibleandwearablebatteries,whichcanconformtodifferentshapesandbeintegratedintovariousdevices.

Inconclusion,thedevelopmentofgraphene-basedelectrodeshasshowngreatpotentialforimprovingtheelectrochemicalperformanceofLIBs.Theuniquepropertiesofgraphene,suchashighelectricalconductivity,highsurfacearea,andexcellentmechanicalstrength,enablethedesignofhigh-performanceelectrodeswithenhancedenergyandpowerdensity,longcyclelife,andimprovedsafety.Furtherresearchiscrucialtooptimizethesynthesisanddesignofgraphene-basedelectrodesandexplorenewapplicationsofthesematerialsintheenergystoragefield.Onewaytoimprovetheelectrochemicalperformanceofgraphene-basedLIBsistotailorthegraphenestructureandmorphologytooptimizetheiondiffusionandchargetransferprocesses.Forexample,theuseofthree-dimensional(3D)graphenearchitectures,suchasgraphenefoams,aerogels,andnanowires,canprovideincreasedsurfaceareaandporosity,aswellasefficientpathwaysforiontransport.These3Dstructurescanalsooffermechanicalflexibilityandstability,whichisimportantforthedurabilityoftheelectrodesduringthecharge-dischargecycles.

Anotherapproachistointroducefunctionalgroupsordopantstomodifythegraphenepropertiesandimproveitscompatibilitywiththeelectrolyteandtheactivematerials.Thefunctionalizationcanbeachievedthroughvariousmethods,suchasoxygenplasmatreatment,chemicaloxidation,ordopingwithheteroatomssuchasnitrogen,sulfur,orboron.Thefunctionalgroupsordopantscancreatedefectsinthegraphenelattice,whichcanenhancethepseudocapacitivebehaviorandincreasetheactivesitesfortheelectrochemicalreactions.

Furthermore,theuseofhybridstructurescombininggraphenewithotherelectrodematerials,suchasmetaloxides,sulfides,orphosphides,canleadtosynergeticeffectsthatenhancetheelectrochemicalperformance.Forexample,thecombinationofgraphenewithFe2O3nanorodscanimprovethecapacityretentionandratecapabilityoftheelectrode,duetotheimprovedconductivityandstabilityofthehybridstructure.Similarly,theintegrationofgraphenewithMoS2nanosheetscanenhancethechargetransferkineticsandpromotetheredoxreactionsattheinterfacebetweenthetwomaterials.

Moreover,thedevelopmentofnewelectrolytesystemswithimprovedsafetyandcompatibilitywithgrapheneelectrodesisalsoacrucialaspectforthepracticalapplicationofthesematerialsinLIBs.Forexample,theuseofionicliquidsorsolid-stateelectrolytescanreducetheriskofleakageorflammability,aswellasimprovetheionconductivityandstabilityoftheelectrodes.Theoptimizationoftheelectrolytecompositionandpropertiescanalsoaffecttheformationofthesolid-electrolyteinterface(SEI)layer,whichcansignificantlyimpactthecapacity,cyclingstability,andsafetyofthebattery.

Insummary,theuniquepropertiesofgrapheneoffergreatpotentialforimprovingtheelectrochemicalperformanceofLIBs,throughthedesignoftailoredstructures,functionalization,hybridization,andoptimizationoftheelectrolytesystem.Theresearchinthisfieldisstillongoing,andfurthereffortsareneededtoexplorethefullpotentialofthesematerialsandbringthemclosertopracticalapplications.Moreover,graphene-basedmaterialshavealsobeenexploredinthedevelopmentofotherenergystoragedevices,suchassupercapacitorsandsodium-ionbatteries.Supercapacitorsareelectrochemicaldevicesthatcanstoreanddeliverhighpowerdensitiesinshortperiodsoftime,makingthemidealforapplicationsthatrequirerapidenergydelivery,suchaselectricvehiclesandportableelectronics.Graphene-basedmaterialshavebeenshowntoofferhighsurfaceareas,goodelectricalconductivity,andexcellentmechanicalproperties,whichareadvantageousforthedesignofefficientanddurablesupercapacitors.

Sodium-ionbatteries(SIBs)areconsideredaspromisingalternativestoLIBsduetotheabundanceandlowcostofsodiumresources.However,thelargerionicsizeofsodiumionscomparedtolithiumionsposeschallengesinthedevelopmentofhigh-performanceSIBs.Graphene-basedmaterialshaveshownpotentialinimprovingtheelectrochemicalperformanceofSIBsthroughtheoptimizationofelectrodestructuresandelectrolytesystems.Forexample,graphenecoatingsonelectrodematerialscanenhancethesodiumiondiffusionkineticsandincreasethespecificcapacityofSIBs.

Inconclusion,graphene-basedmaterialshaveshowngreatpotentialinimprovingtheelectrochemicalperformanceofenergystoragedevices,suchasLIBs,supercapacitors,andSIBs.Theiruniqueproperties,includinghighsurfaceareas,goodelectricalconductivity,andexcellentmechanicalproperties,makethemattractivecandidatesforthedevelopmentofefficientanddurableenergystoragedevices.Furtherresearcheffortsareneededtofullyexplorethepotentialofgraphene-basedmaterialsandbringthemclosertopracticalapplicationsinthefieldofenergystorage.Inrecentyears,theneedforefficientanddurableenergystoragedeviceshasbeengrowingduetotheincreasingdemandforrenewableenergy,electricvehicles,andportableelectronics.Asaresult,therehasbeenasignificantfocusondevelopingadvancedenergystoragetechnologieswithsuperiorperformance,longercyclelife,andlowercost.

Graphene-basedmaterialshaveemergedaspromisingalternativesforenergystorageapplicationsduetotheiroutstandingproperties,suchashighsurfacearea,excellentelectricalconductivity,goodmechanicalproperties,andchemicalstability.Inthisregard,grapheneanditsderivatives,suchasgrapheneoxide(GO)andreducedgrapheneoxide(RGO),haveattractedsignificantattentioninthedevelopmentofdifferenttypesofenergystoragedevices,includinglithium-ionbatteries(LIBs),supercapacitors,andsodium-ionbatteries(SIBs).

Oneofthesignificantadvantagesofgrapheneanditsderivativesinenergystorageapplicationsistheirlargesurfacearea,whichprovidesmoreactivesitesforelectrochemicalreactions.ThispropertycanenhancetheelectrodeperformanceofLIBs,asthehighsurfaceareaofgraphene-basedmaterialspromotestheadsorptionanddesorptionoflithiumions,leadingtohigherreversiblecapacityandfastercharge/dischargerates.Moreover,theexcellentelectricalconductivityofgraphene-basedmaterialscanfacilitatetheelectrontransportbetweentheelectrodeandtheelectrolyte,resultinginlowerresistanceandbetterratecapability.Thesepropertiesmakegraphene-basedmaterialsattractivecandidatesforhigh-performanceLIBs.

InadditiontoLIBs,graphene-basedmaterialshavealsoshownpotentialinthedevelopmentofsupercapacitors,whichareenergystoragedevicesthatstoreenergythroughelectrostaticcharge.Inthiscase,thehighsurfaceareaandgoodelectricalconductivityofgraphene-basedmaterialscanincreasethechargestoragecapacityandreducetheenergylossduringcharging/dischargingcycles.Furthermore,themechanicalflexibilityofsomegraphene-basedmaterial