Low Temperature Hydrothermal Synthesis of Na₃Fe₂(PO₄)₂F₃ and its Cathode Electrochemistry in Na- and Li-Ion Batteries

Abstract

Na3Fe2(PO4)2F3 has been synthesized under mild hydrothermal conditions. The structure of Na3Fe2(PO4)2F3 has been solved using single-crystal X-ray diffraction and the phase purity has been evaluated by Rietveld refinement from high resolution synchrotron powder X-ray diffraction data. Both methods establish the accuracy of P42/mnm space group and synthesis of so called beta2-polymorph. Room temperature 57Fe Mössbauer spectroscopic studies confirm 3+ oxidation state of the compound. The electrochemical properties have been investigated with respect to Li- and Na-ion batteries. Galvanostatic charge-discharge studies indicate that up to ~0.6 lithium ions and only ~0.4 sodium ions per Fe can be inserted at an average voltage of 2.82 and 2.42 V with respect to Li+/Li and Na+/Na in lithium and sodium ion batteries, respectively. The cycle-life studies indicate that Li-ion batteries show very stable capacity retention over long cycles while Na-ion batteries tend to lose capacity after ~35 cycles at C/5 rate.

Department(s)

Chemistry

Comments

U.S. Department of Energy, Grant DE-AC02-06CH11357

Keywords and Phrases

Hydrothermal synthesis; Li-ion electrochemistry; Na-ion electrochemistry; Na Fe (PO ) F 3 2 4 2 3; Poly-anion cathode

International Standard Serial Number (ISSN)

0022-4596; 1095-726X

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2021 Elsevier, All rights reserved.

Publication Date

01 Mar 2021

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