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The LiNbV(PO4)3 phosphate with the anti-NASICON structure (a = 12.126(1) Å, b = 8.6158(4) Å, c = 8.6959(6) Å, V = 908.5(1) Å3, S.G. Pbcn) has been synthesized using a Pechini sol–gel process. It exhibits reversible multielectron transitions versus Li and Na anodes. In a Li half-cell, it supports a 4e− transfer due to the activation of the Nb5+/Nb3+ and V4+/V2+ redox couples, being the first example of 4d metal redox transitions within the anti-NASICON framework confirmed by XANES measurements. X-ray diffraction performed in ex situ and operando regimes disclosed a single-phase mechanism of lithium (de)intercalation. In a Na half-cell, the material demonstrates reversible uptake of 2.77 Na+ ions. Density functional theory calculations revealed percolation barriers of ∼0.5–0.7 eV for Na+ hopping, thus supporting the activation of Na+ ion diffusion in the NbV(PO4)3 framework. This study introduces a new approach to improve anti-NASICON-structured electrode materials by utilizing redox transitions of 4d elements for energy storage. [ABSTRACT FROM AUTHOR]

The article explains the synthesis, as well as the properties of the mixed-valent palladate K[Pd.sub.2][O.sub.3] compound. The alternate sequencing and ordering of the [Pd.sup.2+] and [Pd.sup.4+] compounds present in the complex is also discussed.

Abstract: NaPd3O4, Na2PdO3 and K3Pd2O4 have been prepared by solid-state reaction of Na2O2 or KO2 and PdO in sealed silica tubes. Crystal structures of the synthesized phases were refined by the Rietveld method from X-ray powder diffraction data. NaPd3O4 (space group Pm3¯n, a=5.64979(6)Å, Z=2) is isostructural to NaPt3O4. It consists of NaO8 cubes and PdO4 squares, corner linked into a three-dimensional framework where the planes of neighboring PdO4 squares are perpendicular to each other. Na2PdO3 (space group C2/c, a=5.3857(1)Å, b=9.3297(1)Å, c=10.8136(2)Å, β=99.437(2)°, Z=8) belongs to the Li2RuO3-structure type, being the layered variant of the NaCl structure, where the layers of octahedral interstices filled with Na+ and Pd4+ cations alternate with Na3 layers along the c-axis. Na2PdO3 exhibits a stacking disorder, detected by electron diffraction and Rietveld refinement. K3Pd2O4, prepared for the first time, crystallizes in the orthorhombic space group Cmcm (a=6.1751(6)Å, b=9.1772(12)Å, c=11.3402(12)Å, Z=4). Its structure is composed of planar PdO4 units connected via common edges to form parallel staggered PdO2 strips, where potassium atoms are located between them. Magnetic susceptibility measurements of K3Pd2O4 reveal a Curie–Weiss behavior in the temperature range above 80K. [Copyright &y& Elsevier]

Abstract: Lead vanadium phosphate Pb3V(PO4)3 was synthesized by solid state reaction and characterized by X-ray single crystal and powder diffraction, electron microscopy, and magnetic susceptibility measurements. The crystal structure model of Pb3V(PO4)3 was refined using X-ray single crystal data (, S.G. ). The compound has an eulytite-like structure and its average structure model may be presented as a three-dimensional network formed by strongly distorted mixed (Pb/VIII) metal-oxygen octahedra connected by edge sharing and forming corrugated chains. The octahedra are additionally linked by tetrahedral phosphate groups via corner sharing. Lead and vanadium atoms randomly occupy two close positions in the octahedra. The electron microscopy study revealed the presence of a rhombohedral superstructure with and indicating ordering in the structure. The same type of superstructure was found by us for two another lead-containing eulytite Pb3Fe(PO4)3 where Fe+3 has an ionic radius close to that of V+3. Magnetic susceptibility measurements revealed Curie–Weiss behavior for the Pb3V(PO4)3 compound. [Copyright &y& Elsevier]

A new potassium palladate KPd2O3 was synthesized by the reaction of KO2 and PdO at elevated oxygen pressure. Its crystal structure was solved from powder X-ray diffraction data in the space group R3¯m (a=6.0730(1) Å, c=18.7770(7) Å, and Z=6). KPd2O3 represents a new structure type, consisting ot an alternating sequence of K+ and Pd2O3- layers with ordered Pd2+ and Pd4+ ions. The presence of palladium ions in di- and tetravalent low-spin states was confirmed by magnetic susceptibility measurements. [ABSTRACT FROM AUTHOR]

The LiNbV(PO 4 ) 3 phosphate with the anti-NASICON structure ( a = 12.126(1) Å, b = 8.6158(4) Å, c = 8.6959(6) Å, V = 908.5(1) Å 3 , S.G. Pbcn ) has been synthesized using a Pechini sol-gel process. It exhibits reversible multielectron transitions versus Li and Na anodes. In a Li half-cell, it supports a 4e - transfer due to the activation of the Nb 5+ /Nb 3+ and V 4+ /V 2+ redox couples, being the first example of 4d metal redox transitions within the anti-NASICON framework confirmed by XANES measurements. X-ray diffraction performed in ex situ and operando regimes disclosed a single-phase mechanism of lithium (de)intercalation. In a Na half-cell, the material demonstrates reversible uptake of 2.77 Na + ions. Density functional theory calculations revealed percolation barriers of ∼0.5-0.7 eV for Na + hopping, thus supporting the activation of Na + ion diffusion in the NbV(PO 4 ) 3 framework. This study introduces a new approach to improve anti-NASICON-structured electrode materials by utilizing redox transitions of 4d elements for energy storage.

NASICON-type NaNbV(PO 4 ) 3 electrode material synthesized by the Pechini sol-gel technique undergoes a reversible three-electron reaction in a Na-ion cell which corresponds to the Nb 5+ /Nb 4+ , Nb 4+ /Nb 3+ , and V 3+ /V 2+ redox processes and provides a reversible capacity of 180 mAh·g -1 . The sodium insertion/extraction takes place in a narrow potential range at an average potential of 1.55 V versus Na + /Na. Structural characterization by operando and ex situ X-ray diffraction disclosed the reversible evolution of the NaNbV(PO 4 ) 3 polyhedron framework during cycling, while XANES measurements in the operando regime confirmed the multielectron transfer upon sodium intercalation/extraction into NaNbV(PO 4 ) 3 . This electrode material demonstrates extended cycling stability and excellent rate capability maintaining the capacity value of 144 mAh·g -1 at 10 C current rates. It can be regarded as a superior anode material suitable for application in high-power and long-life sodium-ion batteries.

In the search for high-energy materials, novel 3D-fluorophosphates, Li2Co1- x Fe x PO4F and Li2Co1- x Mn x PO4F, have been synthesized. X-ray diffraction and scanning electron microscopy have been applied to analyze the structural and morphological features of the prepared materials. Both systems, Li2Co1- x Fe x PO4F and Li2Co1- x Mn x PO4F, exhibited narrow ranges of solid solutions: x ≤ 0.3 and x ≤ 0.1, respectively. The Li2Co0.9Mn0.1PO4F material demonstrated a reversible electrochemical performance with an initial discharge capacity of 75 mA·h·g(-1) (current rate of C/5) upon cycling between 2.5 and 5.5 V in 1 M LiBF4/TMS electrolyte. Galvanostatic measurements along with cyclic voltammetry supported a single-phase de/intercalation mechanism in the Li2Co0.9Mn0.1PO4F material.