Tuning the Crystal Structure of A2CoPO4F (A = Li, Na) Fluoride-Phosphates: A New Layered Polymorph of LiNaCoPO4F

Stanislav S. Fedotov, Dmitry A. Aksyonov, Aleksandr Sh Samarin, Olesia M. Karakulina, Joke Hadermann, Keith J. Stevenson, Nellie R. Khasanova, Artem M. Abakumov, Evgeny V. Antipov

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4 Citations (Scopus)

Abstract

Co-containing fluoride-phosphates are of interest in sense of delivering high electrode potentials and attractive specific energy values as positive electrode materials for rechargeable batteries. In this paper we report on a new Co-based fluoride-phosphate, LiNaCoPO4F, with a layered structure (2D), which was Rietveld-refined based on X-ray powder diffraction data [P21/c, a = 6.83881(4) Å, b = 11.23323(5) Å, c = 5.07654(2) Å, β = 90.3517(5) °, V = 389.982(3) Å3] and validated by electron diffraction and high-resolution scanning transmission electron microscopy. The differential scanning calorimetry measurements revealed that 2D-LiNaCoPO4F forms in a narrow temperature range of 520–530 °C and irreversibly converts to the known 3D-LiNaCoPO4F modification (Pnma) above 530 °C. The non-carbon-coated 2D-LiNaCoPO4F shows reversible electrochemical activity in Li-ion cell in the potential range of 3.0–4.9 V vs. Li/Li+ with an average potential of ≈ 4.5 V and in Na-ion cell in the range of 3.0–4.5 V vs. Na/Na+ exhibiting a plateau profile centered around 4.2 V, in agreement with the calculated potentials by density functional theory. The energy barriers for both Li+ and Na+ migration in 2D-LiNaCoPO4F amount to 0.15 eV along the [001] direction rendering 2D-LiNaCoPO4F as a viable electrode material for high-power Li- and Na-ion rechargeable batteries. The discovery and stabilization of the 2D-LiNaCoPO4F polymorph indicates that temperature influence on the synthesis of A2MPO4F fluoride-phosphates needs more careful examination with perspective to unveil new structures.

Original languageEnglish
Pages (from-to)4365-4372
Number of pages8
JournalEuropean Journal of Inorganic Chemistry
Volume2019
Issue number39-40
DOIs
Publication statusPublished - 31 Oct 2019

Keywords

  • Electrode materials
  • Fluoride-phosphates
  • High voltage cathodes
  • Layered compounds
  • Rechargeable batteries
  • Structure elucidation

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