Morphology modification and delithiation mechanisms of LiMn{sub 2}O{sub 4} and Li{sub 2}MnO{sub 3} by acid digestion

Journal Article · Thu Jan 01 04:00:00 EST 1998 · Journal of the Electrochemical Society

DOI:https://doi.org/10.1149/1.1838203· OSTI ID:599633

Shao-Horn, Y; Hackney, S A ^[1]; Ein-Eli, Y; Averill, W F ^[2]; Robertson, A D ^[3]; Howard, Jr, W F ^[4]

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1. Michigan Technological Univ., Houghton, MI (United States). Dept. of Metallurgical and Materials Engineering
2. Covalent Associates, Inc., Woburn, MA (United States)
3. Univ. of St. Andrews (United Kingdom). School of Chemistry
4. Kerr-McGee Technical Center, Oklahoma City, OK (United States)

The structural features of equilibrium phases, LiMn{sub 2}O{sub 4} and Li{sub 2}MnO{sub 3}, and their acid-delithiated products (MnO{sub 2}) are compared using x-ray diffraction and electron microscopy. The observed morphological changes associated with acid-delithiated Li{sub 0.1}Mn{sub 2}O{sub 4} confirm the acid digestion mechanism proposed by Hunter. Three delithiated phases including {alpha}-, {gamma}-, {beta}-MnO{sub 2}-like phases can be derived from Li{sub 2}MnO{sub 3} under different acid digestion conditions. An acid-delithiation mechanism converting Li{sub 2}MnO{sub 3} to {alpha}- and {gamma}-MnO{sub 2} is proposed. This mechanism involves an acid-dissolution and precipitation process. A related scheme is also proposed for the formation of {beta}-MnO{sub 2}-like materials from {alpha}- and {gamma}-MnO{sub 2} phases. The crystallography of the {alpha}-MnO{sub 2} structure is related to the grain/crystal geometry of {alpha}-MnO{sub 2} on the basis of convergent-beam electron diffraction and lattice imaging analysis. An in situ heating experiment in a transmission electron microscope demonstrates that heat-treatment of hydrated {alpha}-MnO{sub 2} at {approximately} 300 C develops porosity within grains/crystals. It is proposed that the microstructural changes induced by acid delithiation may contribute to the reported difference in the initial electrochemical behavior of acid delithiated Li{sub 0.1}Mn{sub 2}O{sub 4} and equilibrium LiMn{sub 2}O{sub 4}. The delithiated product derived from Li{sub 2}MnO{sub 3} at {approximately} 115 C for 4--6 h, having {gamma}-MnO{sub 2} as the major phase, demonstrates superior electrochemical properties.

• OSTI ID: 599633
• Journal Information: Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 1 Vol. 145; ISSN 0013-4651; ISSN JESOAN
• Country of Publication: United States
• Language: English

Related Subjects

25 ENERGY STORAGE
36 MATERIALS SCIENCE
ACID HYDROLYSIS
DEMETALLIZATION
ELECTRIC BATTERIES
ELECTRODES
LITHIUM OXIDES
MANGANESE OXIDES
MICROSTRUCTURE
MORPHOLOGICAL CHANGES
PHASE STUDIES