Structural and electrochemical characterization of Li{sub 2}MnSiO{sub 4} cathode material.
The candidate cathode material Li{sub 2}MnSiO{sub 4} for lithium-ion cells was synthesized by an all-acetate precursor sol/gel method under a reducing atmosphere at 600, 700, and 800 C. The material prepared at 700 C was a pure phase and had the structural order of Li{sub 3}PO{sub 4} orthorhombic (S.G. Pmn2{sub 1}) phase. The temperature dependence of the molar magnetic susceptibility of Li{sub 2}MnSiO{sub 4} was found to be consistent with an antiferromagnetic material with a Nel temperature of 12 K. The calculated effective moment confirmed that the observed magnetic behavior involves Mn{sup 2+} ions in a high spin configuration in tetrahedral sites. Scanning electron microscopy of Li{sub 2}MnSiO{sub 4} showed large aggregates (10 to 50 {micro}m) composed of nanosized particles (100-200 nm). The as-prepared material was almost electrochemically inactive despite the presence of 15 wt % carbon additive. The material was treated by carbon coating using cellulose carbon source precursor and particle size reduction using high-energy ball milling. In coin-cell tests, the carbon-coated and ball-milled materials yielded charge capacities of 190 and 172 mAh/g, respectively, under a current density of 10 mA/g. At present, the cationic mixing between Li{sup +} and Mn{sup 2+} ions in their mutual crystallographic sites is the main impediment to the achievement of the full theoretical capacity of Li{sub 2}MnSiO{sub 4} (333 mAh/g).
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- EE
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 969915
- Report Number(s):
- ANL/CSE/JA-65214; TRN: US201002%%884
- Journal Information:
- J. Phys. Chem. C, Vol. 113, Issue 2009; ISSN 1932-7447
- Country of Publication:
- United States
- Language:
- ENGLISH
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