Synthesis and electrode properties of metastable Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}} spinel oxides
Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}} spinel oxides with 0.36 < {delta} < 0.46 were synthesized by oxidation of aqueous Mn{sup 2+} with hydrogen peroxide or lithium peroxide in the presence of lithium carbonate or lithium hydroxide followed by firing the precursor in air at 300--400 C. Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}} spinel is metastable and disproportionates at about 500 C to give a lithium-rich spinel Li{sub 1{minus}x}Mn{sub 2{minus}x}O{sub 4+{delta}} and Mn{sub 2}O{sub 3}. The disproportionation temperature and the amount of Mn{sub 2}O{sub 3} impurity formed depended on the synthesis procedure and raw materials used. Use of lithium peroxide and lithium hydroxide in the solution-based oxidation procedure produced the least amount of Mn{sub 2}O{sub 3} impurity at intermediate temperatures. However, the value of x in the lithium-rich spinel Li{sub 1+x}Mn{sub 2{minus}x}O{sub 4+{delta}} decreased with a further increase in firing temperature, and the stoichiometric spinel LiMn{sub 2}O{sub 4} without Mn{sub 2}O{sub 3} impurity was formed at 800 C. Phase analysis as a function of firing temperature for a wider range of Li/Mn ratios in the system Li{sub y}Mn{sub 3{minus}y}O{sub 4+{delta}} (0.7 {le} y {le} 1.33) also revealed that single-phase spinel could be formed for the entire firing temperature range 300 {le} T {le} 800 C only for a narrow value of 1.05 {le} y {le} 1.25. The lithium-intercalation properties of the metastable Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}} spinel were influenced by the firing temperature. A Li{sub 2}Mn{sub 4}O{sub 9{minus}{delta}} sample formed at an optimum temperature of 400 C showed a capacity of 130 mAh/g in the range 3.8--2.0 V with excellent cyclability.
- Research Organization:
- Univ. of Texas, Austin, TX (US)
- OSTI ID:
- 20080555
- Journal Information:
- Journal of the Electrochemical Society, Vol. 147, Issue 5; Other Information: PBD: May 2000; ISSN 0013-4651
- Country of Publication:
- United States
- Language:
- English
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