Nickel-Metal-Hydride--Battery-(Thesis)

Zr-BasedAB2AlloysforNegativeElectrodeofNickel-MetalHydrideBatteryADissertationSubmittedfortheMasterDegreeofMechanicalEngineeringAuthor:WangGuoliangSupervisor:AkibaEtsuo2015Fukuoka,JapaniAbstractNi-MHbatterywithhighenergydensityandsafetyandwithoutheavymetalpollution,isveryimportantincurrenthumansocietybecauseofitswidespreaduseinmanyfieldssuchasvehicleandelectronicproduct.InNi-MHbatteries,thepositiveelectrodeisusuallyfabricatedbyNiOOH;thenegativeelectrodeiscomprisedofdifferenttypesofmetalhydridematerials.Forpracticalapplication,themetalhydridematerialshavetofulfillsomedemandssuchashighhydrogenstoragecapacity,moderateequilibriumpressure,outstandinginitialhydrogenation/dehydrogenationpropertiesandsoon.Zr-basedLavesphase(AB2)alloyswithhigherhydrogenstoragecapacitythanthoseofAB5andA2B7-typealloys,areconsideredasagroupofthepotentialnegativeelectrodematerialsfornickel-metalhydride(Ni-MH)batteries.However,Zr-basedAB2alloysconfrontwithhighH2plateaupressureandpoorinitialhydrogenationpropertieswhichneedtobesolvedbeforetheircommercialapplication.Inthisstudy,ZrMn2-basedalloyscomprisedofdifferentproportionsofZr,Ti,Ni,MnandAlwereemployedtotunethehydrogenplateaupressure.TheplateaupressuresweresuccessfullyadjustedtothetargetpressurebysubstitutionofNiwithAlinZrMn2-basedalloys.TheplateaupressuresofsamplesM03-M06changedfrom0.02MPato0.08MPa,M06withthemaximumhydrogenstoragecapacityof1.38wt.%exhibitedlowestplateaupressure0.02MPaamongallsamples.Interestingly,thenegativecorrelationbetweenplateaupressureandunitcellvolumeofZrMn2-basedalloyswasobserved.Moreover,heattreatmentandhotalkalinesolutiontreatmentwerecarriedoutinordertoimprovetheinitialactivationpropertiesofZrMn2-basedalloys.M01andM02wereadoptedforheattreatmentstudy,therewasnoobviousimprovementofinitialactivationinbothM01andM02samplesafter6hheatiitreatmentat1100˚C,longerheattreatmenttimeispossiblyneeded.M03-M06wereemployedforhotalkalinesolutiontreatmentstudyunder110˚Cfor70min.Itwasfoundthattheinitialactivationabilitiesofthesesampleswithhotalkalinesolutiontreatmentwereimprovedsignificantlybycomparingwiththosewithouthotalkalinesolutiontreatment,whichindicateshotalkalinesolutiontreatmentisanefficientmethodtoachievethepracticalapplicationofZr-basedAB2alloysforcommercialNi-MHbattery.iiiContentsChapter1Introduction……………………………………………………………...11.1Background…………………………………………………………...............11.2Ni-MHbattery……………………………………………………………….....51.2.1HistoryofNi-MHbattery………………………………………………....51.2.2FundamentalsofNi-MHbattery………………………………………...61.2.3RequirementsofalloysfornegativeelectrodeofNi-MHbattery........91.2.4Mechanismofhydrogenabsorptionanddesorption………………..101.3Hydrogenstoragealloys……………………………………………………121.3.1AB5rareearthalloys…………………………………………………...121.3.2ABalloys………………………………………………………………...131.3.3A2Balloys…………………………………………………………….....141.3.4A2B7alloys………………………………………………………………141.3.5AB2alloys………………………………………………………………..141.4Zr-basedAB2alloys………………………………………………………....161.4.1Researchhistory………………………………………………………..161.4.2ResearchachievementsandIssues………………………………….161.4.3IssueofZr-basedAB2Lavesphasealloy…………………………....18Chapter2Thepurposeoftheresearch……………………………………….....20Chapter3Experimental…….……………………………………………………...233.1Preparationofsamples……………………………………………………..233.1.1Melt-spunandrollercooling……………………………………….......233.1.2Grindingandsieving…………………………………………………...233.1.3Heattreatment…………………………………………………………..243.1.4Hotalkalinesolutiontreatment………………………………………..243.2Characteristicevaluation…………………………………………………...253.2.1X-raydiffraction(XRD)…………………………………………………253.2.2Scanningelectronmicroscopy/energydispersivespectroscopy(SEM/EDS)…………………………………………………………….…263.2.3Pressure-concentration-temperature(PCT)…………………………28Chapter4ElementsubstitutionforadjustmentofPCTplateaupressure…....304.1XRD………………………………………………………………………......304.2SEM………………………………………………………………………......314.3PCT…………………………………………………………………………...33Chapter5Heattreatmentforimprovementofinitialhydrogenation…………..355.1XRD………………………………………………………………………….365.2SEM/EDS……………………………………………………………………385.3PCT…………………………………………………………………………...42ivChapter6Alkalinetreatmentforimprovementofinitialhydrogenation...........446.1XRD………………………………………………………………………......446.1.1Beforehotalkalinetreatment………………………………………….446.1.2Afterhotalkalinetreatment………………………….………………...456.2SEM/EDS………………………………………………………………….…466.3PCT…………………………………………………………………………...506.4XRDafterPCTmeasurement……………………………………………...53Chapter7Conclusions…………………………………………………………….55References………………………………………………………………………......571Chapter1Introduction1.1BackgroundItiswellknownthatTomasEdisoninventedthefirstlampin1879,hebroughtthelighttohumansociety.Fromthenon,electricenergybecamemoreandmoreconvenienttous.Theelectricitycouldconverttolight,heat,andmotionandsoon.Batteries,whichstoresenergyinaconvenientandefficientmanner,havebeenwidelyusedinelectricdevices.Accordingtothechargeability,batteriescanbeclassifiedintotwotypes:primarybatteriesandsecondarybatteries.Theprimarybatteriese.g.zine-carbonbattery,alkalinebattery,silveroxidebattery,couldnotbere