Low-CoLa1.8Ti0.2MgNi8.9Co0.1alloyswerepreparedbymagneticlevitationmeltingfollowedbyannealingtreatment.TheeffectofannealingonthehydrogenstoragepropertiesofthealloyswasinvestigatedsystematicallybyX-raydiffraction（XRD）,pressure-compositionisotherm（PCI）,andelectrochemicalmeasurements.TheresultsshowthatallsamplescontainLaNi5andLaMg2Ni9phases.LaCo5phaseappearsat1,000℃.Theenthalpychangeofallhydridesiscloseto-30.6kJ·mol-1H2ofLaNi5compound.Annealingnotonlyincreaseshydrogencapacityandimprovescyclingstabilitybutalsodecreasesplateaupressureat800and900℃.Afterannealing,thecontractionofcellvolumeandtheincreaseofhydridestabilitycausethehighratedischargeabilitytoreduceslightly.Theoptimumalloyisfoundtobeoneannealedat900℃,withitshydrogencapacityreachingupto1.53wt%,anddischargecapacityremaining225.1mAh·g-1after140charge–dischargecycles.
