Influence of Substitution on the Structure and Electrochemistry of Layered Manganese Oxides

Abstract

Layered substituted lithium manganese oxides were prepared by ion-exchange of compounds with the nominal composition Na 0.7 MnO 2 or Na 0.7 Mn 0.89 M 0.11 O 2 , (where M=Fe, Co, Ni, Cu, Zn, Li or Al) and were characterized structurally and electrochemically. The sodium-containing materials have P2 stacking or are P2/P3 intergrowths, whereas the lithiated analogs have O2 or stacking faulted O2/O3 structures.Compounds with O3 components exhibit higher capacity (or faster intercalation kinetics) than the pure O2 materials. Neither O2 nor, surprisingly, O2/O3 structures converted to spinel upon repeated charging in lithium cells to high voltages, for sixty or more cycles.The results presented herein suggest that it might be possible to design an electrode with an acceptable compromise between the phase stability of the O2 structure and the higher capacity (or better rate capability) of O3 compounds by manipulating the relative amounts and distributions of these two phases in intergrowth structures.

Investigation of layered intergrowth LixMyMn1?yO2+z (M=Ni, Co, Al) compounds as positive electrodes for Li-ion batteries

“…The potential drop during the 15 minutes of relaxation occurring after each oxidation and reduction (for the same current density) is also larger in materials with high O2 content. This is evident in Figure 3 [6,7]. Further investigation of the effect of structure on phase conversion using 7 Li-MAS NMR and in situ XRD is underway in this laboratory.…”

“…This is evident in Figure 3 [6,7]. Further investigation of the effect of structure on phase conversion using 7 Li-MAS NMR and in situ XRD is underway in this laboratory.…”

“…A rough estimate of the relative proportions of P2 and P3 components can be made from the xray powder diffraction data, although satisfactory Rietveld refinements of intergrowth patterns 4 are difficult to obtain [7]. These values are reported in Table 1, along with the elemental analyses.…”

“…O2 layered lithium manganese oxides, prepared from P2-Na 0.7 MnO 2+z , do not have a cubic closepacked oxygen array and do not convert to spinel under normal cycling conditions [6]. Recently, several layered Li x M y Mn 1-y O 2 compounds (y=0.1, M=Ni, Co, Al) with O2/O3 intergrowth structures have been prepared by ion exchanging P2/P3 sodium-containing precursors [7]. These intergrowth structures have better electrochemical characteristics than pure O2 compounds and do not appear to convert to spinel.…”

Synthesis and electrochemical characterization of M2Mn3O8 (M=Ca, Cu) compounds and derivatives

“…In actuality, the electrochemical properties of these materials are very dependent upon the stacking arrangements, the nature and amount of any substituents, [1] and the presence or absence of vacancies in the transition metal layers [2,3]. In this context, the family of manganese oxides having the general formula M 2 Mn 3 O 8 , where M is a +2 cation such as Co [4], Mn, Cd [5], Zn [6], Cu [7], or Ca [8] is of considerable interest.…”