沥青基炭材料：结构设计、制...法及其在储能中应用（英文）_刘慧超.pdf

Cite this:NewCarbonMaterials,2023,38(3):459-477DOI:10.1016/S1872-5805(23)60743-7Pitch-based carbon materials:a review of their structural design,preparation and applications in energy storageLIUHui-chao,ZHUSheng*,CHANGYun-zhen,HOUWen-jing,HANGao-yi*（Institute of Molecular Science,Key Laboratory of Materials for Energy Conversion and Storage of Shanxi Province,Key Laboratory of Chemical Biologyand Molecular Engineering of Education Ministry,Shanxi University,Taiyuan 030006,China）Abstract：Becauseofitshighcarboncontentandeasygraphitization,pitchisapromisingprecursorforcarbonmaterials.Topro-ducecarbonmaterialswiththedesiredperformance,itisnecessarytoovercometheinherentshortcomingsofpitch.Forexample,itscomplexcompositionandeasymeltingmakeitdifficulttocontrolthestructureoftheresultingcarbonmaterials.Recently,research-ershaveproposedseveralmethodstocontrolthestructureofcarbonmaterialsproducedfrompitchforenergystorageapplications.Thelatestadvancesinthestructuraldesignandpreparationofpitch-basedcarbonmaterialsforuseinenergystoragedevicessuchassupercapacitorsandalkalimetalionbatteriesarereviewed.Key words:Pitch；Carbonmaterials；Preparation；Structuraldesign；Energystorage1IntroductionThispaper reviews the recent research pro-gressesofpitch-basedcarbonmaterialsasshowninFig.1.Inordertoobtainthecarbonmaterialswithcontrollablestructure,variouspreparationmethodsarefirstlyintroduced,suchassolventpartition,templateandpre-oxidationstrategies.Thematerialcharacterist-icsandstructureregulationmechanismofthesemeth-odsarealsothoroughlyanalyzed.Then,thepotentialapplicationsofpitch-basedporouscarboninenergystorage applications including supercapacitors(SCs)andalkalimetalionbatteriesaresummarized.Finally,theremainingchallengesandresearchprospectsinthefieldarediscussed.Withthe large-scale consumption of fossil en-ergy,ithasbecometheresearchfocustosaveenergyanddeveloprenewableenergywhilerealizingthera-tionalandeffectiveutilizationoflimitedresources12.Inthedevelopmentandutilizationofrenewableen-ergy,carbonmaterialsplayacrucialrolebecausetheycanbewidelyusedaselectrodematerialsorimport-antcomponents in energy storage systems.In prin-ciple,carbonmaterialscanbepreparedfromvariouscarbon-containingsources.Generally,peopletendtochooselow-cost precursors such as biomass,poly-mersandpitchtoproducevariouscarbonmaterials.Chinaisrichincoalresourcesandthecokingca-pacityranksfirstintheworld,theyieldofcoaltarpitch(CTP)fromcokingindustryisabout50%-60%.Nowadays,the pitch is mainly used in traditionalfieldssuchasrefractory,adhesive,anti-corrosion,wa-terproofandroadbuildingmaterialsduetoitsgoodcorrosion resistance and cohesiveness36.However,theabove-mentionedtraditionalapplicationscanonlytransformpitchintolowaddedvalueproducts.There-fore,newapplicationsareurgentlyneededtoexploreanddeveloptoconvertpitchintoproductswithhighvalue.Notably,pitchhasmeritsofhighcarboncon-tent,abundanceandinexpensiveprice,whichiscon-sideredaspromisingcandidatetoproducecarbonma-terials.Currently,preparationofcarbonmaterialforenergy storage has become an important route fordeeputilizationofasphaltbecausepitchiseasytobegraphitized compared with biomass and syntheticpolymer79.Uptodate,avarietyofcarbonmaterialsincludingcarbonnanospheres,nanowires,nanosheetsand networks have been prepared from pitch1012.Theyhavebeenwidelyevaluatedtouseaselectrodematerialforsupercapacitor(SCs),lithiumion,sodi-Received date：2023-02-10；Revised date：2023-05-11Corresponding author：ZHUSheng,Lecturer.E-mail:;HANGao-yi,Professor.E-mail:han_Author introduction：LIUHui-chao.E-mail:第38卷第3期新型炭材料（中英文）Vol.38No.32023年6月NEWCARBONMATERIALSJun.2023umionandpotassiumionbatteries1315.Pitchcanbedividedintopetroleumasphaltandcoaltarasphaltduetodifferentsourcesandprocessesof production.Generally,CTP contains polycyclicaromatic hydrocarbons,while the large polycyclicaromatichydrocarbonsareprovedtobeeasilyconver-tedintothegraphitestructure1618.However,thepitchpossesses complex chemical compositions,whichhaveanegativeimpactonregulatingthestructureandcomposition of the final carbon products.In the1970s,researchersusedorganicsolventstosegmentthecomplexpitchcomponentsbasedontheprincipleofsimilarsolubilityintosolublesubstancesindiffer-ent solvents by using the organic solvents ofquinoline,toluene,petroleum ether,n-hexanol,car-bondisulfideandsoon.Then,thesubstancewithsim-ilarcomponentandstructureissubsequentlystudied1921.The other feature for pitch is thermo-plastic,that is,when the temperature reaches thesofteningpointofpitch,thepitchwillchangefromsolidtoliquid.Duetotheexistenceoftheabove-men-tioned characteristics,it is difficult to control thestructureofthefinalcarbonmaterialduringthecon-versionprocessofpitch.Therefore,templatessuchasmagnesiumoxide,calciumoxide,silicondioxideandmoltensalts,areintroducedintothesystemtoregu-latetheporestructureandmorphologyofpitch-basedcarbon materials2224.In addition to the templatemethod,oxidationstrategyhasalsobeendevelopedtopreparepitch-based porous carbon.During the pro-cess,functionalgroupswillbeintroducedintothemo-leculesofpitchtoincreasetheirreactionactivity.Sub-sequently,themoleculesreactwitheachothertoformmacromolecules with similar structure to graphite,thusthestructuralstabilityoftheintermediateproducthas been enhanced as the phase change is avoidedduringpyrolysisprocess2527.Sincethatthemorpho-logyofcarbonmaterialscanbewellcontrolled,thepitch-oxidation method has become an importantstrategytopreparecarbonmaterials.Electrochemical energy storage performance ofcarbon materials is strongly depended on the porestructure,surfacepropertyandspecificsurfacearea.Poreengineeringandheteroatomdopingareeffectivestrategiesto improve the electrochemical perform-anceofcarbonmaterials2829.Fortheporeengineer-ing,itisessentialtocontroltheporestructuresinclud-ingporevolume,diameteranditsdistribution.Gener-ally,therearemicropores,mesoporesandmacroporesexistinthecarbonmaterialsforenergystorage.Themicroporesplayamajorroleinthespecificsurfaceareaofcarbonmaterialsandcanproviderichactivesitesforelectrolyteionadsorption,whereasthemicro-porespreventrapiddiffusionofelectrolyteions.Com-paratively,mesopores can supply high-speed chan-nels for ion transmission and diffusion.Macroporeswith larger size can be used as the storage tank ofelectrolyte ions to shorten the diffusion distance ofelectrolyteions,whereastheymakelesscontributiontothespecificsurfaceareaofcarbonmaterials3031.Uptodate,thehierarchicalporouscarbonmaterialswith micropores,mesopores and macropores havebeensynthesizedbythetemplate,activationmethod,solventpartitionandpre-oxidationmethods.Inaddi-tiontoporeengineering,introductionofheteroatoms(e.g.,oxygen,nitrogen,sulfur,phosphorusandboron,etc.)intocarbonmaterialscannotonlyimprovethehydrophilicitytopromotethechargetransferontheelectrode/electrolyte interface,but also increase thePitchSupercapacitorsPotassium-ion batteriesLithium-ion batteriesSodium-ion batteriesChemical oxidationHard templateSoft templateMolten saltPre-oxidationTemplate methodSolvent partitionOxidation methodFig.1Schematicillustrationofsynthesisstrategyofpitch-basedporouscarbonandtheirapplicationsinenergystorage460新型炭材料（中英文）第38卷pseudo-capacitanceof carbon materials through re-versibleredoxreactions32.2Pre-treatingprocess 2.1 Solvent partition methodCTPisakindofmixturecomposedofpolycyc-licaromatichydrocarbonsandtheirderivatives3335.ThecommonsolventsegmentationmethodisusedtodivideCTPintothecomponentswithsimilarstruc-tureandcharacteristics(e.g.,volatilityandsofteningpoint).Theprincipleisthateachcomponentofpitchhas different aromatization degree,compositionand/orproperty,showingdistinctivesolubilityindif-ferentorganicsolvents.Therefore,theselectionofap-propriateorganicsolventsallowsforefficientlyseg-mentingthe pitch components.The widely-usedor-ganicsolventsincludequinoline,pyridine,tetrahydro-furan,cyclohexane,petroleum ether,gasoline,n-heptane,benzene and toluene3639.After being seg-mented,thepitchsectionshavesimilarpropertiesandbecomeeasytocontrolthestructureoftheobtainedcarbonmaterials.Forexample,Guanetal.haveusedtoluene,quinolineandpyridineasextractantstodi-vide CTP(softening point,274 C)into 2 parts:(1)lightcomponentsoftolueneandpyridinesolublesubstances,(2)heavy components of quinoline andquinolineinsolublesubstances(Fig.2a).ItisfoundthatporouscarbonmaterialsareeasilypreparedfromthelightcomponentbyKOHactivation,asitcontainsmorevolatilealkylsidechains.Onthecontrary,theKOH activated PACs(a)(b)Coal tar pitchToluene-solublefractionPyridine-solublefractionQuinoline-solublefractionQuinoline-insolublefractionBubblesGraphite crystallitesK+H2OH2OH2OSteam activated PACsKOHKOHCoal tar pitchPreparationPorous carbonsTunable 2-4 nmmesoporesAccessiblemicroporesElectrolyte ions60PC-aPC-bPC-cPC-dPC-ePC-fPC-aPC-bPC-cPC-dPC-ePC-fV2-4 nm/Vtotal/%40200020406080100The light component content of coal tar pitch/wt.%Areal capacitance/(mFcm2)600V2-4 nm/Vtotal/%400200001020304050Supercapacitive energy storageFig.2(a)TheillustrationoftheKOH-activatedsamples40.Copyright2018ElsevierLtd.(b)ThepreparationprocessofPCsandtherelationshipbetweentheTScontentofMCTPsandthespecificsurfacearea,cumulativeporevolume,andV24nm/VtotalratioofPCs42.Copyright2020ElsevierLtd第3期LIUHui-chaoetal:Pitch-basedcarbonmaterials:areviewoftheirstructuraldesign,preparation461heavycomponentofCTPiseasiertoformrichporestructures under the activation of steam40.Further,immersingcomponents(-resin)(solubleinquinolineandinsolubleintoluene)inconcentratedsulfuricacidcould obtain the sulfonated pitch molecules41.Theoxygencontainingfunctionalgroupssuchassulfonicgroupsare introduced to the pitch molecules to in-creasestheactivesites,whichcanmakepitcheasiertocrosslink.Furthermore,asshowninFig.2b,theformationofsmallmesopores(2-5nm)inporouscarbonmateri-als has been controlled by adjusting the content oflightcomponentsinpitchmolecules42.Additionally,Zhuangetal.dividedthepitchinto6componentswithcarbondisulfide,acetoneandethylacetate,andactiv-atedeachcomponentathightemperature43.Thecar-bon materials obtained from different componentsshowdifferentelectrochemicalpropertieswhentheyareusedaselectrodematerialsforSCs.Itisfoundthatthecarbonmaterialderivedfromthepitchcomponentextractedfromcarbondisulfidedemonstratesthebestelectrochemical performance.The above-mentionedresultsshowthatdifferentcomponentsofpitchhaveanimportantinfluenceontheporestructureandmor-phologyofthecarbonproduct.2.2 Pre-oxidation methodDue to the conjugation of polycyclic aromatichydrocarbons,the molecules of pitch tend to formstackedstructureduringthepyrolysisprocess,whichisnotconducivetoformporousstructure.Addition-ally,therarefunctionalgroupsinthemoleculesalsogreatlyhindertheinteractionwithothercompounds.Hence,thepitchneedstobemodifiedbeforeundergo-ing the process of synthesizing porous carbon4445.Oxidation method can introduce oxygen containingfunctionalgroupsintopitchmoleculestoimprovethereactivityofpitchmolecules.Thecross-linkingreac-tion between the functional groups makes the pitchmoleculesformarelativelystablestructure,whichismoreconducivetothesubsequentregulationofmi-crostructure46.2.2.1ChemicaloxidationmethodStrongoxidantssuchashydrogenperoxide,nitricacidandpotassiumpermanganatecanintroducefunc-tionalgroupsintothearomaticringofpitch.Thein-troductionoffunctionalgroupsnotonlycanimprovethehydrophilicityofpitch,butalsoincreasetheact-ivesitesforenergystorage4749.Comparedwithhy-drogenperoxide,strongeroxidantofnitricacidcannot only introduce oxygen and nitrogen containingfunctional groups into the side chains of aromaticrings,butalsobreakthesidechainsofaromaticringsinpitchmoleculesorthefatchainsbetweenaromaticrings,whichweakenstheconjugationeffectbetweenpolycyclicaromatichydrocarbonsandreducestheex-cessiveaccumulationofpitchmolecules50.Therefore,the pitch-based carbon materials obtained from theprecursorsoxidizedbynitricacidhadlargerspecificsurfaceareaandmoreporesthanhydrogenperoxide(Fig.3a-c).Yangetal.51haveprepared3Dporouscarbon from nitric acid oxidized pitch(Fig.3d),inwhichthemorphologyofporouscarbonwasadjustedbyaddingferricchlorideandzincchloride(Fig.3e-h).The results show that the layered porous carbon ispreparedundertheconditionofaddingzincchlorideandferricchlorideatthesametimeduetothejointactionoftheactivatorofzincchlorideandthestruc-turedirectingagentofferricchloride.Thestrongox-idantofpotassiumpermanganatehasalsobeenusedtooxidizepitch.Zhuangetal.52haveobtainedtheox-idizedpitchbymixingpitchandpotassiumperman-ganateatroomtemperatureandusedthiskindofpitchoxideasrawmaterialtodirectlysynthesizeoxygendoped 3D porous carbon via salt template method.Summary,afterintroductionoffunctionalgroupsintothePAHssidechainofpitch,thespecificsurfaceareaandporevolumeofthematerialcanbecontrolled.2.2.2Pre-oxidationinairComparedwiththechemicaloxidationmethod,air pre-oxidation method is more environmentallyfriendlybecausenostrongoxidantsarerequired.Pre-oxidationinairreferstointroduceoxygencontainingfunctionalgroupsbyheatingpitchmoleculesatarel-ativelylowtemperature(T400C)intheairatmo-sphere53.Yang et al.54 have used toluene solublepitchasrawmaterialtocontrolthemicrostructureand462新型炭材料（中英文）第38卷propertiesofcarbonproductsbychangingthepre-ox-idationtemperature(Fig.4a).AsshowninFig.4b-c,theoxygencontainingfunctionalgroupscanbecon-trolledbyadjustingthetemperature.Alargenumberofoxygen-containinggroupsinthearomaticringcanavoidthemutualaccumulationofpitchmoleculestoformablockystructure.Besides,theintroductionofoxygen-containingfunctional groups can also im-prove the hydrophilicity of pitch molecules.Lu etal.55reportedanairpre-oxidationmethodtocontrolthemicrostructureofpitch-basedcarbon.Usually,thepitch-based carbon materials obtained by directlypyrolyzingathightemperatureshowhighlygraphit-izedregularstructure.Butafterthepitchispre-oxid-Benzene ring(a)(b)(c)(e)(g)(h)(f)(d)CyclohexaneCTPH2O2CTP(O)CTP(N,O)HNO3600PC-CTPPC-CTP(O)PC-CTP(N,O)Volume adsorbed/(cm3g1)40020000.00.20.40.60.81.0Relative pressure/(p/p0)0.15PC-CTPPC-CTP(O)PC-CTP(N,O)Pore volume/(cm3g1)0.100.050.000.0050.000110100100Pore size/nmPore size/nmHCTPHNO3OxidationActivationFeCl3+ZnCl2O-HCTPLGPC96 nm1 m1 m1 m1 m128 nm124 nm91 nmFig.3(a)Schematicdiagramforadjustinghydrophilyandaromaticitystrategy50,(b)theN2sorptionisothermand(c)poresizedistributionofsampletreatedbyvariousoxidants.Copyright2022ElsevierLtd.(d)SchematicdiagramofLGPC51,SEMimagesofsamples(e)withoutadditionsandwith(f)ZnCl2,(g)FeCl3,(h)ZnCl2,FeCl3.Copyright2021ElsevierLtdAir Pre-oxidationTSOTSx(a)(b)(c)(e)(f)(d)OTSx-PCTSOTS200OTS250OTS3002004006008001000Temprature/oC200020406080100400 600 800 1000Temprature/oCIntensity/(a.u.)3500 3000 2500 2000 1500 1000Wavenumber/cm1Intensity/(a.u.)Mass/%OTS350TSOTS200-OHAliphatic-C-HAromatic-C-HC=OC=C-CH3-CH2-O-OTS250OTS300OTS350OTS200OTS0OTS250OTS300OTS350ActivationN25 m5 mCoal tar pitchO-MsP/O-CMsCPOEmulsificationOxidationAir flowCrosslinkCarbonizationNaH2PO2PH3P/O dopingFig.4(a)SchematicdiagramforOTS-PC54,(b)thethermogravimetriccurveand(c)fourierinfraredimageofsamplestreatedatvarioustemperatures.Copyright2022ElsevierLtd.(d)S