Anionic substitution in LiMnPO4: The Li1-xMn1+x(PO4)1-y-z(VO4)y(OH)4z solid solutions prepared with a microwave-assisted hydrothermal method

Maria A. Kirsanova, Sergey V. Ryazantsev, Artem M. Abakumov

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Attempts to introduce vanadium doping into the olivine-structured LiMnPO4 cathode material for the Li-ion batteries resulted in the (y ​+ ​z)PO4 3− → yVO4 3− ​+ ​4zOH (y ​< ​0.17, z ​≤ ​0.1) co-substitution and the formation of the hydrotriphylite-type Li1−xMn1+x(PO4)1−y−z(VO4)y(OH)4z solid solutions. Their crystal structure and chemical composition were studied with Rietveld structure refinement from synchrotron X-ray powder diffraction data, energy-dispersive X-ray analysis, infrared and Raman spectroscopy, electron energy loss analysis and mass spectrometry. Li0.96Mn1.04(PO4)0.74(VO4)0.16(OH)0.4 crystallizes in the space group Pnma and a ​= ​10.5150(2) Å, b ​= ​6.11773(9) Å and c ​= ​4.78555(9) Å with up to 5% of Mn in the Li position. Charge compensation is achieved through partial oxidation of the Mn cations to the oxidation state above +2. The heterovalent substitution in anionic sublattice and defectiveness of the cationic one cause blocking of Li-ion diffusion channels that drastically impede the electrochemical performance resulting in electrochemical capacity not exceeding 35 mAh g−1.

Original languageEnglish
Article number121294
JournalJournal of Solid State Chemistry
Volume286
DOIs
Publication statusPublished - Jun 2020

Keywords

  • Crystal structure
  • Heterovalent anionic substitution
  • Li-ion cathode materials
  • Microwave hydrothermal synthesis
  • Mixed polyanion compounds

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