Study On Oxygen Deficiency In Spinel LiNi_0.5Mn_1.5O₄ And Its Fe And Cr-doped Compounds

Spinel LiNi0.5Mn1.5O4 is a very important and promising cathode material for lithium ion batteries,and oxygen deficiency is an important factor to affect the electrochemical properties of spinel LiNi0.5Mn1.5O4.The action mechanism of doping elements in LiNi0.5Mn1.5O4 is complex.In this study,the Cr,Fe-doped compounds LiNi0.45M0.1Mn1.45O4(M=Cr,Fe)and pristine compound LiNi0.5Mn1.5O4 have been synthesized at the same annealing conditions.In this study,it is investigated how oxygen deficiency in spinel LiNi0.5Mn1.5O4 was affected by calcination temperature and oxygen partial pressure.The oxygen deficiency as a function of calcination temperatures has been modeled.Doping elements have influence on oxygen deficiency.The thermogravimetric analysis shows different situation for these samples.Oxygen dissipation in the Cr-doped compound at high temperature is less than the other two samples.The as prepared samples display different morphological features.The XPS spectra display that the doping elements have influences on the chemical valence of Mn,and result in more Mn(?)amount in the Cr,Fe-doped products.Under the same calcination and cooling condition,there more oxygen deficiency remained in Fe and Cr-doped compounds than in pristine LiNi0.5Mn1.5O4.The doped compounds exhibit excellent rate capability.At 10C-charge/10C-discharge rate,their capacities are 85 mAh·g-1,74 mAh·g-1 and 50mAh·g-1 for LiNi0.45Fe0.1Mn1.45O4,LiNi0.45Cr0.1Mn1.45O4 and LiNi0.5Mn1.5O4,respectively.The coulomb efficiencies of LiNi0.45Cr0.1Mn1.45O4 in the first charge and discharge cycle reached a high value of 89.1%.