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Issue 29, 2018
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Reversible facile Rb+ and K+ ions de/insertion in a KTiOPO4-type RbVPO4F cathode material

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Abstract

In this paper, we report on a novel RbVPO4F fluoride phosphate, which adopts the KTiOPO4 (KTP) type structure and complements the AVPO4F (A = alkali metal) family of positive electrode (cathode) materials for metal-ion batteries. RbVPO4F was synthesized via a freeze-drying assisted solid-state route and characterized via structural, computational and electrochemical methods. RbVPO4F represents the first example of reversible electrochemical Rb+ de/insertion in a crystalline oxypolyanionic framework. The electrochemical measurements on RbVPO4F in a three-electrode cell configuration in RbClO4-saturated propylene carbonate (PC) electrolyte revealed that the material exhibits reversible Rb+ de/insertion within the 0.4–1.3 V vs. Ag+/Ag potential range (∼3.9–4.8 V vs. K+/K) displaying rather high diffusion coefficients of (0.3–1.0) × 10−11 cm2 s−1 comparable to those of K+ in KVPO4F that supports reasonably fast ionic mobility in the KTP structure despite the large ionic radius of the Rb+ ions. The energy barriers of Rb+ ion transport are exceptionally low not exceeding 0.2 eV along the c-axis and correlating well with diffusion coefficients estimated using the DFT+U-NEB methodology and with the experimentally determined transport properties. These results suggest a new paradigm for the development of materials that support many monovalent ion reversible de/insertion processes in a single prototypical structural oxypolyanionic framework.

Graphical abstract: Reversible facile Rb+ and K+ ions de/insertion in a KTiOPO4-type RbVPO4F cathode material

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Publication details

The article was received on 25 Apr 2018, accepted on 02 Jul 2018 and first published on 03 Jul 2018


Article type: Paper
DOI: 10.1039/C8TA03839B
J. Mater. Chem. A, 2018,6, 14420-14430

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    Reversible facile Rb+ and K+ ions de/insertion in a KTiOPO4-type RbVPO4F cathode material

    S. S. Fedotov, A. Sh. Samarin, V. A. Nikitina, D. A. Aksyonov, S. A. Sokolov, A. Zhugayevych, K. J. Stevenson, N. R. Khasanova, A. M. Abakumov and E. V. Antipov, J. Mater. Chem. A, 2018, 6, 14420
    DOI: 10.1039/C8TA03839B

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