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Title: Synthesis and characterization of metastable, 20 nm-sized Pna2{sub 1}-LiCoPO{sub 4} nanospheres

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 nanospheresmore » 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+}).« less

Authors:
 [1];  [2];  [3];  [1]
  1. Technical University of Munich, Department of Chemistry, Synthesis and Characterization of Innovative Materials, Lichtenbergstr. 4, 85747 Garching (Germany)
  2. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd, Menlo Park, CA 94025 (United States)
  3. Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, 1 Cyclotron Rd, Berkeley, CA 94720 (United States)
Publication Date:
OSTI Identifier:
22658234
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 248; Other Information: Copyright (c) 2017 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:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 77 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

Citation Formats

Ludwig, Jennifer, Nordlund, Dennis, Doeff, Marca M., and Nilges, Tom, E-mail: tom.nilges@lrz.tum.de. Synthesis and characterization of metastable, 20 nm-sized Pna2{sub 1}-LiCoPO{sub 4} nanospheres. United States: N. p., 2017. Web. doi:10.1016/J.JSSC.2017.01.015.
Ludwig, Jennifer, Nordlund, Dennis, Doeff, Marca M., & Nilges, Tom, E-mail: tom.nilges@lrz.tum.de. Synthesis and characterization of metastable, 20 nm-sized Pna2{sub 1}-LiCoPO{sub 4} nanospheres. United States. doi:10.1016/J.JSSC.2017.01.015.
Ludwig, Jennifer, Nordlund, Dennis, Doeff, Marca M., and Nilges, Tom, E-mail: tom.nilges@lrz.tum.de. Sat . "Synthesis and characterization of metastable, 20 nm-sized Pna2{sub 1}-LiCoPO{sub 4} nanospheres". United States. doi:10.1016/J.JSSC.2017.01.015.
@article{osti_22658234,
title = {Synthesis and characterization of metastable, 20 nm-sized Pna2{sub 1}-LiCoPO{sub 4} nanospheres},
author = {Ludwig, Jennifer and Nordlund, Dennis and Doeff, Marca M. and Nilges, Tom, E-mail: tom.nilges@lrz.tum.de},
abstractNote = {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+}).},
doi = {10.1016/J.JSSC.2017.01.015},
journal = {Journal of Solid State Chemistry},
number = ,
volume = 248,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2017},
month = {Sat Apr 15 00:00:00 EDT 2017}
}