Microstructural features of {alpha}-MnO{sub 2} electrodes for lithium batteries
- Michigan Technological Univ., Houghton, MI (United States). Dept. of Metallurgical and Materials Engineering
- Argonne National Lab., IL (United States)
X-ray diffraction and transmission electron microscopy, including lattice imaging and convergent-beam electron diffraction, were used to study the microstructural features of {alpha}-MnO{sub 2} products that had been synthesized from different precursors. The {alpha}-MnO{sub 2} products, which were formed by acid digestion of Mn{sub 2}O{sub 3} and Li{sub 2}MnO{sub 3} oxide powders, contained water molecules in the (2 x 2) channels of their hollandite-type structures. The {alpha}-MnO{sub 2} crystals had a distinct rod-shaped morphology with the [001] crystallographic orientation parallel to the rod axis. Transmission electron microscopy data showed that the nature of the precursor directly affects the grain morphology of the {alpha}-MnO{sub 2} product. The grain morphology of {alpha}-MnO{sub 2} electrodes plays an important role in the electrochemical behavior of Li/{alpha}-MnO{sub 2} rechargeable cells: crystals with a small aspect ratio have a large electrochemically active surface [i.e., a large exposed (2 x 2) tunnel cross-sectional area] per unit volume available for lithium insertion. Lattice imaging and electron diffraction studies of chemically lithiated {alpha}-MnO{sub 2} products (Li{sub x}MnO{sub 2}: 0.4 < x < 0.5) confirmed that the {alpha}-MnO{sub 2} structure was unstable to chemical lithiation; the capacity loss that was observed during the initial electrochemical cycling of Li/{alpha}-MnO{sub 2} cells is attributed to this structure instability.
- OSTI ID:
- 599916
- Journal Information:
- Journal of the Electrochemical Society, Vol. 145, Issue 2; Other Information: PBD: Feb 1998
- Country of Publication:
- United States
- Language:
- English
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