- Crystal structures and local environments of NASICON-type Na3FeV(PO4)3and Na4FeV(PO4)3positive electrode materials for Na-Ion batteries
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In this work, we investigate the crystal chemistry of Fe/V-mixed NASICON [sodium (Na) Super Ionic CONductor] compositions Na3FeV(PO4)3 and Na4FeV(PO4)3 that are structurally related to Na3V2(PO4)3, a positive electrode for Na-ion batteries. To synthesize Na4FeV(PO4)3, various synthesis routes (solid-state, sol-gel-assisted, and electrochemical syntheses) were investigated. Direct syntheses resulted in the formation of a NASICON-type phase in the presence of NaFePO4 and Na3PO4 impurities. The successful preparation of pure Na4FeV(PO4)3 has been achieved by the electrochemical sodiation of Na3FeV(PO4)3. Both synchrotron X-ray absorption and M?ssbauer spectroscopy allowed probing the local V and Fe environments and their oxidation states in Na3FeV(PO4)3 and Na4FeV(PO4)3. Na3FeV(PO4)3 crystallizes in the space group C2/c (a = 15.1394(2) ? b = 8.72550(12) ? c = 21.6142(3) ? β = 90.1744(9)° and Z = 12), and it is isostructural to an ordered α-form of Na3M2(PO4)3 (M = Fe, V). It presents a superstructure due to Na+ ordering, as confirmed by differential scanning calorimetry and in situ temperature X-ray diffraction. The electrochemically sodiated Na4FeV(PO4)3 powder crystallizes in the space group R3ˉ c (a = 8.94656(8) ?, c = 21.3054(3) ?, and Z = 6) within which the two sodium sites, Na(1) and Na(2), are almost fully occupied. Na4FeV(PO4)3 allows the electrochemical extraction of 2.76 Na+ per formula unit within the voltage range of 1.3-4.3 V versus Na+/Na through the FeIII/II, VIV/III, and VV/IV redox couples. This identifies an interesting material for Na-ion batteries.
- Carlier, Dany,Chotard, Jean-No?l,Courty, Matthieu,Croguennec, Laurence,Duttine, Mathieu,Fauth, Fran?ois,Iadecola, Antonella,Masquelier, Christian,Moog, Iona,Park, Sunkyu
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- Synthesis and structure of bis-hexaaquasodium bis-nitrilotris(methylenephosphonato)decaaquamonohydrohexasodiumlanthanate trihydrate [Na(H2O)6]2[LaNa6H(H2O)10{N(CH2PO3)3}2] · 3H2O
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A complex salt of nitrilotris(methylenephosphonic acid) with sodium and lanthanum was prepared, isolated, and studied. The salt [Na(H2O)6]2[LaNa6H(H2O)10{N(CH2PO3)3}2] · 3H2O crystallizes in space group P21/c, Z = 2, a = 11.86630(10), b = 10.55060(10), c = 19.99270(10) ?, β = 94.6760°. The La coordination polyhedron is a virtually regular rhombohedron. The Na atom is coordinated at the vertices of a distorted octahedron. Both ligand molecules chelate the La atom; each PO3 group forms a La–O–P–O–Na bridge; the ligand denticity is 7.
- Somov,Chausov,Zakirova,Petrov,Shumilova,Aleksandrov
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- Mechanochemistry-Based Synthesis of Highly Crystalline γ-Zirconium Phosphate for Selective Ion Exchange
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Highly crystalline γ-zirconium phosphate has been synthesized by a novel minimalistic approach and investigated as a selective ion exchanger for cesium, ammonium and potassium. In contrast to current solution-based preparations, the mechanochemistry-based synthesis provides easy access to γ-zirconium phosphate with short synthesis times and low crystallization temperature. The addition of NaF as a mineralizer increases the crystallinity of γ-zirconium phosphate, which forms micrometer-sized uniformly shaped rectangular platelets. The crystalline material has extremely high selectivity to cesium even in the presence of 1000- or 500-fold excess Na+ or Ca2+, respectively. The removal efficiency was >98% in the pH range of 2-5.5. As an ion exchanger for purification of dialysate, crystalline γ-zirconium phosphate shows higher uptake of ammonium and potassium ions than the amorphous gel compound currently used in sorbent cartridges. This sustainable protocol opens up opportunities for many practical applications of γ-zirconium phosphate.
- Cheng, Yu,Dong Tony Wang, Xiao,Jaenicke, Stephan,Chuah, Gaik-Khuan
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