Solid-State Chemistry and Electrochemistry of LiCo[sub 1∕3]Ni[sub 1∕3]Mn[sub 1∕3]O[sub 2] for Advanced Lithium-Ion Batteries

Abstract

LiCo1∕3Ni1∕3Mn1∕3O2LiCo1∕3Ni1∕3Mn1∕3O2 was prepared and characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS) to examine whether or not our first-principles calculation properly predicted a new lithium insertion material of LiCo1∕3Ni1∕3Mn1∕3O2LiCo1∕3Ni1∕3Mn1∕3O2 . High-resolution TEM image directly showed the layered structure having a cubic close-packed oxygen array. The [00.1]-zone electron diffraction pattern showed a [3×3]R30°[3×3]R30° -type superlattice ordering in the transition metal layers. Rietveld analysis of powder XRD indicated that a structural model with a space group symmetry of P3112P3112 to present a [3×3]R30°[3×3]R30° -type superlattice based on α-NaFeO2α-NaFeO2 -structural type was adequate rather than that simply formulated with R3¯mR3¯m . The Me-O bond lengths, i.e., 1.93, 2.03, and 1.92Å1.92Å , respectively, for Co, Ni, and Mn, obtained by KK -edge EXAFS, were compared with those calculated from structural data determined by XRD assuming P3112P3112 and also with those of the first-principles calculation. These values were consistent with each other, which indicated that LiCo1∕3Ni1∕3Mn1∕3O2LiCo1∕3Ni1∕3Mn1∕3O2 was a superlattice structure ( P3112P3112 ; a=4.959Åa=4.959Å , and c=14.254Åc=14.254Å ) consisting of Co3+(t2g6eg0)Co3+(t2g6eg0) , Ni2+(t2g6eg2)Ni2+(t2g6eg2) , and Mn4+(t2g3eg0)Mn4+(t2g3eg0) .