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Title: 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 valuesmore » 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.« less
Authors:
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Publication Date:
OSTI Identifier:
22341864
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 49; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; CATIONS; ELECTRODES; LITHIUM; LITHIUM IONS; NANOPARTICLES; NANOSTRUCTURES; NUCLEAR MAGNETIC RESONANCE; PHOSPHATES; SOL-GEL PROCESS; SOLID SOLUTIONS; SPECTRA; SPECTROSCOPY; TITANIUM IONS; TRIGONAL LATTICES; X-RAY DIFFRACTION