Lithium manganese nickel oxides Li{sub x}(Mn{sub y}Ni{sub 1{minus}y}){sub 2{minus}x}O{sub 2}. 1: Synthesis and characterization of thin films and bulk phases

Journal Article · Tue Dec 01 04:00:00 EST 1998 · Journal of the Electrochemical Society

DOI:https://doi.org/10.1149/1.1838929· OSTI ID:316274

Neudecker, B J; Zuhr, R A; Kwak, B S; Bates, J B ^[1]; Robertson, J D ^[2]

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1. Oak Ridge National Lab., TN (United States). Solid State Div.
2. Univ. of Kentucky, Lexington, KY (United States). Dept. of Chemistry

The series Li{sub x}(Mn{sub y}Ni{sub 1{minus}y}){sub 2{minus}x}O{sub 2} for x {le} 1.33 and 0.38 {le} y {le} 0.50 shows a very close relationship to its parent series Li{sub x}Ni{sub 2{minus}x}O{sub 2}. The refined lattice parameters for at least 0.93 {le} x {le} 1.26 are a linear function of the concentration ratio Li/(Mn + Ni) which in turn is proportional to the averaged valence state of the transition metals. Li{sub x}(Mn{sub y}Ni{sub 1{minus}y}){sub 2{minus}x}O{sub 2} is able to reversibly coprecipitate/reinsert Li{sub 2}O and release/absorb O{sub 2}. This self-regulation mechanism seems to always adjust the number of cations to an undisturbed oxygen sublattice according to the rule cations/anions = 1, which holds true at least for temperatures up to 800 C and oxygen partial pressures above 10{sup {minus}5} atm. Samples prepared in air and under O{sub 2} did not show nucleation of Li{sub 2}O, not even for x > 1.0. The series Li{sub x}(Mn{sub y}Ni{sub 1{minus}y}){sub 2{minus}x}O{sub 2} where 0.38 {le} y {le} 0.50 crystallizes in a rhombohedral unit cell (space group R{bar 3}m) for x < 1.15 and transforms into a single monoclinic phase (space group C2/c) for x > 1.25. The similarity between Li{sub x}Ni{sub 2{minus}x}O{sub 2} and Li{sub x}(Mn{sub y}Ni{sup 1{minus}y}){sub 2{minus}x}O{sub 2} strongly suggests a rhombohedral {r_arrow} cubic transition at x {approx} 0.6 for the latter series. Derived from the linear dependence of the X-ray density on the stoichiometric parameter x, an equation was found with which the lithium concentration of Li{sub x}(Mn{sub y}Ni{sub 1{minus}y}){sub 2{minus}x}O{sub 2} thin film phases over the entire range 0 {le} x {le} 1.33 can be determined accurately without extensive ion-beam analysis. XPS measurements on a film with the bulk stoichiometry Li{sub 1.10}Mn{sub 0.39}Ni{sub 0.51}O{sub 2} gave evidence for Mn{sup 4+} and Mn{sup 3+}, but no indication was found for nickel valence states other than Ni{sup 2+}. In order to meet the above-given stoichiometry, the averaged nickel valence state had to increase with film depth.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-96OR22464
• OSTI ID: 316274
• Journal Information: Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 12 Vol. 145; ISSN JESOAN; ISSN 0013-4651
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
36 MATERIALS SCIENCE
CATHODES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
LITHIUM OXIDES
MANGANESE OXIDES
METAL-NONMETAL BATTERIES
NICKEL OXIDES
SYNTHESIS
VALENCE