Ionothermal Synthesis of High-Voltage Alluaudite Na2+2xFe2-x(SO4)3 Sodium Insertion Compound: Structural, Electronic, and Magnetic Insights

Debasmita Dwibedi, Chris D. Ling, Rafael B. Araujo, Sudip Chakraborty, Shanmugha sundaram Duraisamy, Nookala Munichandraiah, Prabeer Barpanda, Rajeev Ahuja

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43 Citations (Scopus)


Exploring future cathode materials for sodium-ion batteries, alluaudite class of Na2FeII2(SO4)3 has been recently unveiled as a 3.8 V positive insertion candidate (Barpanda et al. Nat. Commun. 2014, 5, 4358). It forms an Fe-based polyanionic compound delivering the highest Fe-redox potential along with excellent rate kinetics and reversibility. However, like all known SO4-based insertion materials, its synthesis is cumbersome that warrants careful processing avoiding any aqueous exposure. Here, an alternate low temperature ionothermal synthesis has been described to produce the alluaudite Na2+2xFeII2-x(SO4)3. It marks the first demonstration of solvothermal synthesis of alluaudite Na2+2xMII2-x(SO4)3 (M = 3d metals) family of cathodes. Unlike classical solid-state route, this solvothermal route favors sustainable synthesis of homogeneous nanostructured alluaudite products at only 300 °C, the lowest temperature value until date. The current work reports the synthetic aspects of pristine and modified ionothermal synthesis of Na2+2xFeII2-x(SO4)3 having tunable size (300 nm ∼5 μm) and morphology. It shows antiferromagnetic ordering below 12 K. A reversible capacity in excess of 80 mAh/g was obtained with good rate kinetics and cycling stability over 50 cycles. Using a synergistic approach combining experimental and ab initio DFT analysis, the structural, magnetic, electronic, and electrochemical properties and the structural limitation to extract full
Original languageEnglish
Pages (from-to)6982-6991
JournalACS Applied Materials & Interfaces
Issue number11
Publication statusPublished - 23 Mar 2016


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