Influence of composition modification on Ca{sub 0.5−x}Mg{sub x}Ti{sub 2}(PO{sub 4}){sub 3} (0.0 ≤ x ≤ 0.5) nanoparticles as electrodes for lithium batteries
Graphical abstract: - Highlights: • Cation mixing was determined in the Ca{sub 0.5−x}Mg{sub x}Ti{sub 2}(PO{sub 4}){sub 3} biphasic series. • Nanometric Ca{sub 0.15}Mg{sub 0.35}Ti{sub 2}(PO{sub 4}){sub 3} delivered 138 mAh/g at C/20 in lithium cells. • Low content of Ca{sup 2+} increases cell volume favoring Li{sup +} insertion in R-3c framework. • Diminution of R{sub SEI} and R{sub CT} for Ca{sub 0.15}Mg{sub 0.35}Ti{sub 2}(PO{sub 4}){sub 3} discharged electrodes. • Fast electrode response for x = 0.35. - Abstract: The Ca{sub 0.5−x}Mg{sub x}Ti{sub 2}(PO{sub 4}){sub 3} series (0.0 ≤ x ≤ 0.5) was prepared by a sol–gel method. X-ray diffraction patterns showed two rhombohedral phases which coexist for intermediate compositions. Despite of the absence of a solid solution mechanism for the whole stoichiometry range, an appreciable cation mixing was observed in both phases. {sup 31}P MAS NMR spectroscopy revealed that low magnesium contents are incorporated to the calcium compound inducing changes in the ordering of the alkaline earth cations in M{sub 1} sites. Derivative plots of the voltage–capacity curves revealed two reversible regions ascribed to the reduction of Ti{sup 4+} to Ti{sup 3+}, ascribable to the subsequent insertion of lithium ions into M{sub 1} and M{sub 2} vacant sites. Capacity values as high as 138 mAh/g after the first discharge were monitored for nanometric Ca{sub 0.15}Mg{sub 0.35}Ti{sub 2}(PO{sub 4}){sub 3} at C/20. Cell cycling under successive kinetic rates revealed a good capacity retention for samples with x = 0.15 and 0.25. Impedance spectra were recorded in lithium cells discharged after different number of cycles at different C rates. The increase in charge transfer resistance was shown to be an important factor determining the electrode behavior on extended cycling.
- OSTI ID:
- 22341864
- Journal Information:
- Materials Research Bulletin, Vol. 49; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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