Synthesis and electrochemical properties of dual doped spinels LiNixAlyMn2-x-yO4 via facile novel chelated sol–gel method as possible cathode material for lithium rechargeable batteries

LiMn2O4andLiNixAlyMn2-x-yO4（x=0.50;y=0.05-0.50）powdershavebeensynthesizedviafacilesolgelmethodusingBehenicacidasactivecheiatingagent.Thesynthesizedsamplesaresubjectedtophysicalcharacterizationssuchasthermogravimetricanalysis（TG/DTA）,X-raydiffraction（XRD）,Fouriertransforminfraredspectroscopy（FT-IR）,field-emissionscanningelectronmicroscopy（FESEM）,transmissionelectronmicroscopy（TEM）andelectrochemicalstudiesviz.,galvanostaticcyclingproperties,electrochemicalimpedancespectroscopy（EIS）anddifferentialcapacitycurves（dQ/dE）.FingerprintXRDpatternsofLiMn2O4andLiNixAlyMn2-x-yO4fortifythehighdegreeofcrystallinitywithbetterphasepurity.FESEMimagesoftheundopedpristinespinelillustrateuniformsphericalgrainssurfacemorphologywithanaverageparticlesizeof0.5μmwhileNidopedparticlesdepictthesphericalgrainsgrowth（50nm）withice-cubesurfacemorphology.TEMimagesofthespinelLiMn2O4showstheuniformsphericalmorphologywithparticlesizeof（100nm）whilelowlevelofAl-dopingspinel（LiNio.5Alo.05Mn1.45O4）displayingcloudyparticleswithagglomeratedparticlesof（50nm）.TheLiMn2O4samplescalcinedat850℃deliverthedischargecapacityof130mAh/ginthefirstcyclecorrespondsto94%coiumbicefficiencywithcapacityfadeof1.5mAh/g/cycleovertheinvestigated10cycles.Amongallfourdopantcompositionsinvestigated,LiNi0.5Al0.05Mn1.45O4deliversthemaximumdischargecapacityof126mAh/gduringthefirstcycleandshowsthestablecyclingperformancewithlowcapacityfadeof1mAh/g/cycle（capacityretentionof92%）overtheinvestigated10cycles.ElectrochemicalimpedancestudiesofspinelLiMn2O4andLiNi0.5Al0.05Mn1.45O4depictthehighandlowrealpolarizationof1562and1100Ω.