Thumbnail
Access Restriction
Open

Author Ludwig, Jennifer ♦ Nordlund, Dennis ♦ Doeff, Marca M. ♦ Nilges, Tom
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY ♦ NANOSCIENCE AND NANOTECHNOLOGY ♦ ABSORPTION SPECTROSCOPY ♦ COBALT IONS ♦ EXPERIMENTAL DATA ♦ HYDROTHERMAL SYNTHESIS ♦ INFRARED SPECTRA ♦ LITHIUM ION BATTERIES ♦ NANOSTRUCTURES ♦ ORTHORHOMBIC LATTICES ♦ PARTICLE SIZE ♦ TEMPERATURE RANGE 0400-1000 K ♦ THERMAL GRAVIMETRIC ANALYSIS ♦ X-RAY DIFFRACTION ♦ X-RAY SPECTROSCOPY
Abstract The majority of research activities on LiCoPO{sub 4} are focused on the phospho-olivine (space group Pnma), which is a promising high-voltage cathode material for Li-ion batteries. In contrast, comparably little is known about its metastable Pna2{sub 1} modification. Herein, we present a comprehensive study on the structure–property relationships of 15–20 nm Pna2{sub 1}-LiCoPO{sub 4} nanospheres prepared by a simple microwave-assisted solvothermal process. Unlike previous reports, the results indicate that the compound is non-stoichiometric and shows cation-mixing with Co ions on the Li sites, which provides an explanation for the poor electrochemical performance. Co L{sub 2,3}-edge X-ray absorption spectroscopic data confirm the local tetrahedral symmetry of Co{sup 2+}. Comprehensive studies on the thermal stability using thermogravimetric analysis, differential scanning calorimetry, and in situ powder X-ray diffraction show an exothermic phase transition to olivine Pnma-LiCoPO{sub 4} at 527 °C. The influence of the atmosphere and the particle size on the thermal stability is also investigated. - Graphical abstract: Blue nano-sized Pna2{sub 1}-LiCoPO{sub 4,} featuring tetrahedrally-coordinated Co{sup 2+}, was synthesized in a rapid one-step microwave-assisted solvothermal process. The phase relation between this metastable and the stable polymorph was analyzed and electrochemical properties are discussed. - Highlights: • Preparation of uniform 15–20 nm nanospheres of metastable Pna2{sub 1}-LiCoPO{sub 4} polymorph. • Structure redetermination shows cation-mixing (Co blocking Li sites). • In situ investigation of phase transformation to olivine Pnma-LiCoPO{sub 4} at 527 °C. • Pna2{sub 1}-LiCoPO{sub 4} reemerges as a stable high-temperature phase above 800 °C. • X-ray absorption spectroscopy confirms local tetrahedral symmetry (T{sub d} Co{sup 2+}).
ISSN 00224596
Educational Use Research
Learning Resource Type Article
Publisher Date 2017-04-15
Publisher Place United States
Journal Journal of Solid State Chemistry
Volume Number 248


Open content in new tab

   Open content in new tab