Na2FePO4F as a Novel Cathode Material for Sodium and Lithium Accumulators
V. R. PODUGOLNIKOV1,2 and N. V. KOSOVA1
1Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences, Ul. Kutateladze 18, Novosibirsk 630128 (Russia)
E-mail: kosova@solid.nsc.ru
2Novosibirsk State University, Ul. Pirogova 2, Novosibirsk 630090 (Russia)
Keywords: Na2FePO4F, mechanochemical synthesis, crystal structure, chemical and electrochemical exchange of Na for Li
Pages: 61–67
Abstract
A solid-phase waste-free and energy-saving synthesis with the use of mechanical activation of single-phase cathode material Na2FePO4F (sp. gr. Pbcn) for sodium and lithium accumulator has been implemented. It has been demonstrated that the product is formed already at the stage of mechanical activation (MA) and is crystallized in the course of subsequent annealing up to 600 °С, whereas heating up to 700 °С results in decomposing the product formed to give Na3PO4, Fe3O4, Na0.11FeF3 and Na3Fe2(PO4)3. Electrochemical properties of Na2FePO4F have been studied in a cell with a lithium anode and lithium electrolyte. According to results of the studies the specific capacity of Na2FePO4F surface-modified with carbon is equal to 115 mA ⋅ h/g at a rate of cycling amounting to C/10. It has been found that the process of chemical and electrochemical replacing Li by Na in the structure of Na2FePO4F is completed by the formation of a compound with the composition NaLiFePO4F (sp. gr. Pbcn).
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