Novel NASICON-Type Na-V-Mn-Ni-Containing Cathodes for High-Rate and Long-Life SIBs.

Partial substitution of V by other transition metals in Na3 V2 (PO4 )3 (NVP) can improve the electrochemical performance of NVP as a cathode for sodium-ion batteries (SIBs). Herein, phosphate Na-V-Mn-Ni-containing composites based on NASICON (Natrium Super Ionic Conductor)-type structure have been fabricated by sol-gel method. The synchrotron-based X-ray study, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) studies show that manganese/nickel combinations successfully substitute the vanadium in its site within certain limits. Among the received samples, composite based on Na3.83 V1.17 Mn0.58 Ni0.25 (PO4 )3 (VMN-0.5, 108.1 mAh g-1 at 0.2 C) shows the highest electrochemical ability. The cyclic voltammetry, galvanostatic intermittent titration technique, in situ XRD, ex situ XPS, and bond valence site energy calculations exhibit the kinetic properties and the sodium storage mechanism of VMN-0.5. Moreover, VMN-0.5 electrode also exhibits excellent electrochemical performance in quasi-solid-state sodium metal batteries with PVDF-HFP quasi-solid electrolyte membranes. The presented work analyzes the advantages of VMN-0.5 and the nature of the substituted metal in relation to the electrochemical properties of the NASICON-type structure, which will facilitate further commercialization of SIBs.

Entropy-Regulated Cathode with Low Strain and Constraint Phase-Change Toward Ultralong-Life Aqueous Al-Ion Batteries.

During multivalent ions insertion processes, intense electrostatic interaction between charge carriers and host makes the high-performance reversible Al3+ storage remains an elusive target. On account of the strong electrostatic repulsion and poor robustness, Prussian Blue analogues (PBAs) suffer severely from the inevitable and large strain and phase change during reversible Al3+ insertion. Herein, we demonstrate an entropy-driven strategy to realize ultralong life aqueous Al-ion batteries (AIBs) based on medium entropy PBAs (ME-PBAs) host. By multiple redox active centers introduction, the intrinsic poor conductivity can be enhanced simultaneously, resulting in outstanding capabilities of electrochemical Al3+ storage. Meanwhile, the co-occupation at metal sites in PBA frameworks can also increase the M-N bond intensity, which is beneficial for constraining the phase change during consecutive Al3+ reversible insertion, to realize an extended lifespan over 10,000 cycles. Based on the calculation at different operation states, the fluctuation of ME-PBA lattice parameters is only 1.2 %. Assembled with MoO3 anodes, the full cells can also deliver outstanding electrochemical properties. The findings highlight that, the entropy regulation strategy could uncover the isochronous constraint on both strain and phase transition for long-term reversible Al3+ storage, providing a promising design for advanced electrode materials for aqueous multivalent ions batteries.

Rietveld refinement of the langbeinite-type mixed-metal phosphate K2Ni0.5Zr1.5(PO4)3.

Dipotassium [nickel(II) zirconium(IV)] tris-(orthophosphate) was prepared from a self-flux in the system K2O-P2O5-NiO-K2ZrF6. The title compound belongs to the langbeinite family and is built up from two [MO6] octa-hedra [M = Ni:Zr with mixed occupancy in ratios of 0.21 (4):0.79 (4) and 0.29 (4):0.71 (4), respectively] and [PO4] tetra-hedra inter-linked via vertices into a (3) ∞[M 2(PO4)3] framework. Two independent K(+) cations are located in large cavities of the framework, with coordination numbers to O(2-) anions of nine and twelve. The K, Ni, and Zr sites are located on threefold rotation axes.

Rietveld refinement of AgCa10(PO4)7 from X-ray powder data.

Polycrystalline silver(I) deca-calcium heptakis(orthophos-phate), AgCa10(PO4)7, was obtained by solid-state reaction. It is isotopic with members of the series MCa10(PO4)7 (M = Li, Na, K and Cs), and is closely related to the structure of ß-Ca3(PO4)2. The crystal structure of the title compound is built up from a framework of [CaO9] and two [CaO8] polyhedra, one [CaO6] octa-hedron (site symmetry 3.) and three PO4 tetra-hedra (one with site symmetry 3.). The Ag(+) cation is likewise located on a threefold rotation axis and resides in the cavities of the rigid [Ca10(PO4)7](-) framework. It is surrounded by three O atoms in an almost regular triangular environment.

K2M(III)2(M(VI)O4)(PO4)2 (M(III) = Fe, Sc; M(VI) = Mo, W), novel members of the lagbeinite-related family: synthesis, structure, and magnetic properties.

The possibility of PO(4)(3-) for MoO(4)(2-) partial substitution in the langbeinite framework has been studied by exploration of the K-Fe(Sc)-Mo(W)-P-O systems using the high-temperature solution method. It was shown that 1/3PO(4)(3-) for MoO(4)(2-) substitution leads to formation of three novel compounds K(2)Fe(MoO(4))(PO(4))(2), K(2)Sc(MoO(4))(PO(4))(2), and K(2)Sc(WO(4))(PO(4))(2) with slightly increased lattice parameters and significant distortion of the anion tetrahedra without structure changes. In contrast, the antiferromagnetic structure is modified by substitution in the low-temperature region. The structural peculiarities are discussed in light of bond-valence sums calculations.

KMg(0.09)Fe(1.91)(PO(4))(2).

KMg(0.09)Fe(1.91)(PO(4))(2), potassium [iron(II)/magnesium] iron(III) bis(orthophosphate), is a solid solution derived from compounds with general formula KM(II)Fe(PO(4))(2) (M(II) = Fe, Cu), in which the Mg atoms substitute Fe atoms only in the octa-hedrally surrounded sites. The framework of the structure is built up from [FeO(5)] trigonal bipyramids and [MO(6)] (M = (Fe, Mg) octa-hedra sharing corners and edges and connected by two types of bridging PO(4) tetra-hedra. The K(+) cations are nine-coordinated and are situated in channels running along [101].

Redetermination of AgPO(3).

Single crystals of silver(I) polyphosphate(V), AgPO(3), were prepared via a phospho-ric acid melt method using a solution of Ag(3)PO(4) in H(3)PO(4). In comparison with the previous study based on single-crystal Weissenberg photographs [Jost (1961 ▶). Acta Cryst. 14, 779-784], the results were mainly confirmed, but with much higher precision and with all displacement parameters refined anisotropically. The structure is built up from two types of distorted edge- and corner-sharing [AgO(5)] polyhedra, giving rise to multidirectional ribbons, and from two types of PO(4) tetra-hedra linked into meandering chains (PO(3))(n) spreading parallel to the b axis with a repeat unit of four tetra-hedra. The calculated bond-valence sum value of one of the two Ag(I) ions indicates a significant strain of the structure.

Structural features of the oxidonitridophosphates K3 M III(PO3)3N (M III = Al, Ga).

Cubic crystals of tripotassium aluminium (or gallium) nitridotriphosphate, K3 M III(PO3)3N (M III = Al, Ga), were grown by application of the self-flux method. In their isostructural crystal structures, all metal cations and the N atom occupy special positions with site symmetry 3, while the P and O atoms are situated in general positions. The three-dimensional framework of these oxidonitridophosphates is built up from [M IIIO6] octa-hedra linked together via (PO3)3N groups. The latter are formed from three PO3N tetra-hedra sharing a common N atom. The coordination environments of the three potassium cations are represented by two types of polyhedra, viz. KO9 for one and KO9N for the other two cations. An unusual tetra-dentate type of coordination for the latter potassium cations by the (PO3)3N6- anion is observed. These K3 M III(PO3)3N (M III = Al, Ga) compounds are isostructural with the Na3 M III(PO3)3N (M III = Al, V, Ti) compounds.

Mixed-metal phosphates K1.64Na0.36TiFe(PO4)3 and K0.97Na1.03Ti1.26Fe0.74(PO4)3 with a langbeinite framework.

Single crystals of the langbeinite-type phosphates K1.65Na0.35TiFe(PO4)3 and K0.97Na1.03Ti1.26Fe0.74(PO4)3 were grown by crystallization from high-temperature self-fluxes in the system Na2O-K2O-P2O5-TiO2-Fe2O3 using fixed molar ratios of (Na+K):P = 1.0, Ti:P = 0.20 and Na:K = 1.0 or 2.0 over the temperature range 1273-953 K. The three-dimensional framework of the two isotypic phosphates are built up from [(Ti/Fe)2(PO4)3] structure units containing two mixed [(Ti/Fe)O6] octa-hedra (site symmetry 3) connected via three bridging PO4 tetra-hedra. The potassium and sodium cations share two different sites in the structure that are located in the cavities of the framework. One of these sites has nine and the other twelve surrounding O atoms.

The triple pyrophosphate Cs3CaFe(P2O7)2.

The complex phosphate tricaesium calcium iron bis(diphosphate), Cs(3)CaFe(P(2)O(7))(2), has been prepared by the flux method. Isolated [FeO(5)] and [CaO(6)] polyhedra are linked by two types of P(2)O(7) groups into a three-dimensional framework. The latter is penetrated by hexagonal channels along the a axis where three Cs atoms are located. Calculations of caesium Voronoi-Dirichlet polyhedra give coordination schemes for the three Cs atoms as [8 + 3], [9 + 1] and [9 + 4]. The structure includes features of both two- and three-dimensional frameworks of caesium double pyrophosphates.

A novel In3O16 fragment in Cs3In3(PO4)4.

The double phosphate Cs(3)In(3)(PO(4))(4), prepared by a flux technique, features a fragment of composition In(3)O(16) formed by three corner-sharing InO(6) polyhedra. The central In atom resides on a twofold rotation axis, while the other two In atoms are on general positions. The O atoms in this fragment also belong to PO(4) tetrahedra, which link the structure into an overall three-dimensional anionic In-O-P network that is penetrated by tunnels running along c. Two independent Cs(+) cations reside inside the tunnels, one of which sits on a centre of inversion. In general, the organization of the framework is similar to that of K(3)In(3)(PO(4))(4), which also contains an In(3)O(16) fragment. However, in the latter case the unit consists of one InO(7) polyhedron and one InO(6) polyhedron sharing an edge, with a third InO(6) octahedron connected via a shared corner. Calculations of the Voronoi-Dirichlet polyhedra of the alkali metals give coordination schemes for Cs of [9+2] and [8+4] (1 symmetry), and for K of [8+1], [7+2] and [7+2]. This structural analysis shows that the coordination requirements of the alkali metals residing inside the tunnels cause the difference in the In(3)O(16) geometry.

NASICON-type Na(3)V(2)(PO(4))(3).

Single crystals of the title compound, tris-odium divanadium(III) tris-(orthophosphate), were grown from a self-flux in the system Na(4)P(2)O(7)-NaVP(2)O(7). Na(3)V(2)(PO(4))(3) belongs to the family of NASICON-related structures and is built up from isolated [VO(6)] octa-hedra (3. symmetry) and [PO(4)] tetra-hedra (.2 symmetry) inter-linked via corners to establish the framework anion [V(2)(PO(4))(3)](3-). The two independent Na(+) cations are partially occupied [site-occupancy factors = 0.805 (18) and 0.731 (7)] and are located in channels with two different oxygen environments, viz sixfold coordination for the first (. symmetry) and eightfold for the second (.2 symmetry) Na(+) cation.

Reinvestigation of KMg(1/3)Nb(2/3)OPO(4).

The crystal structure of potassium magnesium niobium oxide phosphate, KMg(1/3)Nb(2/3)OPO(4), which was described in the space group P4(3)22 [McCarron & Calabrese, (1993 ▶). J. Solid State Chem.102, 354-361], has been redetermined in the revised space group P4(1). Accordingly, the assignment of the space group P4(3)22 and, therefore, localization of K at a single half-occupied position, as noted in the previous study, proved to be an artifact. As a consequence, two major and two minor positions of K are observed due to the splitting along [001], as first noted for KTiOPO(4) structure analogues. It has been shown that the geometry of the {M(II) (1/3)Nb(2/3)O(6/2)}(∞) framework is almost unaffected by the lowering of symmetry.

Rietveld refinement of whitlockite-related K(0.8)Ca(9.8)Fe(0.2)(PO(4))(7).

The title compound, K(0.8)Ca(9.8)Fe(0.2)(PO(4))(7) (potassium deca-calcium iron hepta-phosphate), belongs to the whitlockite family. The structure is built up from several types of metal-oxygen polyhedra: two [CaO(8)], one [CaO(7)] and one [(Ca/Fe)O(6)] polyhedron with a mixed Ca/Fe occupancy in a 0.8:0.2 ratio, as well as three tetra-hedral [PO(4)] units. Of the 18 sites in the asymmetric unit, the site with the mixed Ca/Fe occupation, the K site, one P and one O site are on special positions 6a with 3 symmetry, whereas all other sites are on general positions 18b. The linkage of metal-oxygen polyhedra and [PO(4)] tetra-hedra via edges and corners results in formation of a three-dimensional framework with composition [Ca(9.8)Fe(0.2)(PO(4))(7)](0.8-). The remaining K atoms (site-occupation factor = 0.8) are located in large closed cavities and are nine-coordinated by oxygen.

Rietveld refinement of the langbeinite-type phosphate K2Ni0.5Hf1.5(PO4)3.

Polycrystalline potassium nickel(II) hafnium(IV) tris-(orthophosphate), a langbeinite-type phosphate, was synthesized by a solid-state method. The three-dimensional framework of the title compound is built up from two types of [MO6] octa-hedra [the M sites are occupied by Hf:Ni in ratios of 0.754 (8):0.246 (8) and 0.746 (8):0.254 (8), respectively] and [PO4] tetra-hedra are connected via O vertices. The K+ cations are located in two positions within large cavities of the framework, having coordination numbers of 9 and 12. The Hf, Ni and K sites lie on threefold rotation axes, while the P and O atoms are situated in general positions.

Bi(nanoparticles)/CNx(nanosheets) nanocomposites as high capacity and stable electrode materials for supercapacitors: the role of urea.

The evolution of high-performance and stable electrode materials for supercapacitors plays a vital role in the next generation of energy storage devices. In this work we present a simple method for preparing Bi(nanoparticles)/CNx(nanosheets) nanocomposites as electrode materials for supercapacitors, which were synthesized by thermally treating bismuth citrate and urea at 550-700 °C under an Ar atmosphere. According to physicochemical studies (XRD, SEM, TG-DTA, XPS, FTIR, and BET), a "smeared" bismuth formation or the formation of nanoparticles on the CNx surface of interwoven 2D-nanosheets at different calcination temperatures was observed. Electrochemical measurements show that the specific capacity of the composites can reach 1251 F g-1 (more than 90% of the theoretical value) at a current density of 500 mA g-1 in a 6 M KOH electrolyte, and most two-dimensional CNx-based nanostructures remain intact after multiple galvanostatic charge-discharge processes, which is promising for the development of highly efficient supercapacitors. A supercapacitor composed of Bi/CNx nanocomposites for the negative electrode and Ni-layered hydroxide for the positive electrode demonstrates a high energy density of 58 W h kg-1 with a power density of 800 W kg-1 accompanied by a good cycle life (the parameters decreased down to only 78% after 1000 charge-discharge cycles). Our current results indicate that the addition of urea not only determines the morphology of the composites, but also lays the foundation for the development of new types of nanocomposites for the power industry.

Rietveld refinement of langbeinite-type K(2)YHf(PO(4))(3).

Potassium yttrium hafnium tris-(orthophosphate) belongs to the langbeinite-family and is built up from [MO(6)] octa-hedra [in which the positions of the two independent M sites are mutually occupied by Y and Hf in a 0.605 (10):0.395 (10) ratio] and [PO(4)] tetra-hedra connected via vertices into a three-dimensional framework. This framework is penetrated by large closed cavities in which the two independent K atoms are located; one of the K atoms is nine-coordinated and the other is 12-coordinated by surrounding O atoms. The K, Y and Hf atoms lie on threefold rotation axes, whereas the P and O atoms are located in general positions.

Cs(2)Bi(PO(4))(WO(4)).

Dicaesium bis-muth(III) phosphate(V) tungstate(VI), Cs(2)Bi(PO(4))(WO(4)), has been synthesized during complex investigation in a molten pseudo-quaternary Cs(2)O-Bi(2)O(3)-P(2)O(5)-WO(3) system. It is isotypic with K(2)Bi(PO(4))(WO(4)). The three-dimensional framework is built up from [Bi(PO(4))(WO(4))] nets, which are organized by adhesion of [BiPO(4)] layers and [WO(4)] tetra-hedra above and below of those layers. The inter-stitial space is occupied by Cs atoms. Bi, W and P atoms lie on crystallographic twofold axes.

CsMgPO(4).

Caesium magnesium orthophosphate is built up from MgO(4) and PO(4) tetra-hedra (both with . m. symmetry) linked together by corners, forming a three-dimensional framework. The Cs atoms have .m. site symmetry and are located in hexa-gonal channels running along the a- and b-axis directions.

Metal Sulfides@Carbon Microfiber Networks for Boosting Lithium Ion/Sodium Ion Storage via a General Metal- Aspergillus niger Bioleaching Strategy.

The fabrication and design of electrodes that transfer more energy at high rates is very crucial for battery technology because of the increasing need for electrical energy storage. Usually, reducing a material's volume expansion and improving its electrical conductivity can promote electron and Li+/Na+ ion transfer in nanostructured electrodes and improve rate capability and stability. Here, we demonstrate a general metal- Aspergillus niger bioleaching approach for preparing novel fungus-inspired electrode materials that may enable high-performance lithium ion/sodium ion batteries with one-dimensional architectures. The fungus functions as a natural template to provide large amounts of nitrogen/carbon sources, which are functionalized with metal sulfide nanoparticles, yielding various metal sulfide nanoparticles/nitrogen-doped carbonaceous fibers (MS/NCF (MS = ZnS, Co9S8, FeS, Cu1.81S)) with high conductivity. In addition, the as-obtained MS/NCF has a uniform fiber architecture and abundant porous structure, which can also enhance the storage ability for LIBs and SIBs. Taking ZnS/NCF as an example, the material exhibits a high specific capacity of up to 715.5 mAh g-1 (100 cycles) and 455 mAh g-1 (50 cycles) at 0.1 A g-1 for LIBs and SIBs, respectively. This versatile approach for employing a fungus as a sustainable template to form high-performance electrodes may provide a systematic platform for implementing advanced battery designs.