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Issue 35, 2017
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High-rate capability of Na2FePO4F nanoparticles by enhancing surface carbon functionality for Na-ion batteries

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Abstract

Metal phosphate compounds are considered promising candidates as positive electrode materials for Na-ion batteries because they offer higher cation-insertion potentials than analogous metal oxides. One such example is sodium iron fluorophosphate (Na2FePO4F), a compound that is typically synthesized by high-temperature solid-state routes. In this study, we prepare phase-pure Na2FePO4F using the polyol route, a low-temperature process that allows for the synthesis of nanoparticles (15–25 nm), a form that enhances Na-ion insertion kinetics and cycling stability. We then apply two methods to enhance the electronic conductivity of Na2FePO4F: (i) converting residual organic byproducts of the polyol synthesis to conductive carbon coatings; and (ii) preparing a nanocomposite with reduced graphene oxide. The resulting electrode materials are characterized in nonaqueous Na-ion electrolytes, assessing such metrics as specific capacity, rate capability, and cycling stability. A thorough electrochemical kinetics analysis is performed to deconvolve surface-vs.-bulk Na-ion insertion as a function of composite structure. Specific capacities between 60–110 mA h g−1 were achieved in galvanostatic charge–discharge tests when cycling in the range from 10C to C/10, respectively.

Graphical abstract: High-rate capability of Na2FePO4F nanoparticles by enhancing surface carbon functionality for Na-ion batteries

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Publication details

The article was received on 30 Jun 2017, accepted on 14 Aug 2017 and first published on 15 Aug 2017


Article type: Paper
DOI: 10.1039/C7TA05680J
Citation: J. Mater. Chem. A, 2017,5, 18707-18715

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    High-rate capability of Na2FePO4F nanoparticles by enhancing surface carbon functionality for Na-ion batteries

    J. S. Ko, Vicky V. T. Doan-Nguyen, H. Kim, X. Petrissans, R. H. DeBlock, C. S. Choi, J. W. Long and B. S. Dunn, J. Mater. Chem. A, 2017, 5, 18707
    DOI: 10.1039/C7TA05680J

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