Mixture Of Na2CO3 Research Articles

NaCrO2 Cathode for High-Rate Sodium-Ionbatteries

Layered lithium intercalation compounds LiMeO2 (where Me is transition element) materials have been widely studied and applied as cathode materials for practical lithium ion batteries. Cost of lithium resource, however, has doubled since commercialization in 1991, and tight supply is expected due to the ever increasing demands of electric vehicles and energy storage systems. Indeed, the lithium resource is unevenly distributed in Southern America. Meanwhile, sodium resources are abundant and unlimited everywhere. Recently, layered NaMeO2 materials are being intensively studied because of reversible Na+ insertion/extraction, in particular, NaCrO2 (R-3m) in Na cell. Here, we report physical and electrochemical properties of NaCrO2. The NaCrO2 powder was synthesized by solid-state method. Stoichiometric mixture of Na2CO3 and Cr2O3 powders were pelletized, and the pellet was heated at 900 oC in Ar. All chemicals and products were handled in an Ar-filled gloved box to avoid air exposure. Phase identification of the products was made using X-ray diffraction (XRD) with Cu Kα radiation and the collected XRD data were analyzed by the Rietveld refinement. Electrochemical test were carried out in coin type sodium cells. Galvanostatic electrochemical charge and discharge tests in 1M NaClO4 in PC solution were carried out at room temperature. XRD pattern of the produced NaCrO2 demonstrated a phase-pure product and it was crystallized to O3 type layer structure with space group of R-3m. The delivered capacity was approximately 110 mAh (gNaCrO2) -1 in voltage range of 2 – 3.6 V and 97 % of the capacity was retained during 50 cycles. Also, the Na/NaCrO2 cell exhibited surprising high rate properties, namely, 84 % of capacity retention at 100 C-rates. Details will be discussed in the conference site. Figure 1

ChemInform Abstract: Synthesis and Crystal Structure of Na4Ni7(AsO4)6.

AbstractSingle crystals of Na4Ni7(AsO4)6 are prepared by annealing a stoichiometric mixture of Na2CO3, As2O3, and NiSO4·6H2O (Al2O3 boat, 1.

All-Solid State Na-Ion Batteries Na2-2dFe2-D(SO4)3|Na3-XMxP1-XS4 (M=Ge4+,Ti4+, Sn4+) (x=0,0.1) | Na2Ti3O7

Sodium ion batteries attracted large research community because of earth-abundance and low cost of sodium. Though significant advances have been made in the development of Na-ion cathodes and anodes, a major impediment to the commercial viability of rechargeable Na-ion batteries is the lack of an effective electrolyte. Current Na-ion electrolytes are mostly based on the same fundamental chemistry as Li-ion electrolytes – a mixture of cyclic and linear organic carbonates with a Na-salt. Such organic solvent-based liquid electrolytes are flammable and have limited electrochemical windows. A promising alternative architecture is all-solid-state Na-ion rechargeable batteries utilizing non-flammable ceramic Na superionic conductor electrolytes. Na solid electrolytes such as -alumina and NAtrium Superionic CONductors (NASICON) are well-studied, but they typically exhibit reasonable ionic conductivities only at higher temperatures. Here we report the synthesis, characterization of materials that from our parallel computational studies appeared to be promising components of all-solid state rechargeable Na-ion batteries with high rate capabilities. Recently it is reported that the cubic phase of Na3PS4 (c-Na3PS4, space group: I4-3m) is a promising solid electrolyte with a room temperature Na+ ion conductivity of 0.2mS/cm. In order to increase the ionic conductivity further we prepared Na3-xMxP1-xS4 (M=Ge4+,Ti4+, Sn4+) (x=0,0.1) using mechanical milling followed by annealing at 250°C. Maximum room temperature ionic conductivity of 0.25mS/cm was observed for Sn doped NaP3S4. In situ high temperature XRD showed that all the compounds are stable up to 400°C.When it comes to identifying cathode materials for such a NIB , a considerable fraction of research activity still focuses materials analogous to those that work well in Li-ion batteries containing costly transition metals such as Co, which appears problematic for various reasons: differences in reaction mechanisms of the Na analogues to the Li transition metal oxides, different structural requirements for Na+ mobility, the fact that a cost advantage of Na over Li will only translate into low cost batteries. Hence, research on transition metal electrode materials for Na-ion batteries will have to concentrate on abundant transition metals (essentially Fe, Ti, Mn, and possibly Cr, V). On the other hand, O3- NaFeO2, and P2-type Nax[Fe0.5Mn0.5]O2 utilizing the Fe4+/Fe3+ redox couple are known to suffer from limited reversible capacity and low operating potential. Here we report the preparation of Na2+2dFe2-d(SO4)3 by mechanical milling of Na2SO4 and FeSO4 followed by annealing at 400ºC in an argon environment. The Na2-2dFe2-d(SO4)3 formed an alluaudite-type structure in space group C2/c with lattice constants a=12.654(1)Å, b=12.761(9)Å, c=6.503(5)Å, β=115.52(1)º close those previously reported for d =0.12.For anode transition metal oxides the number of low potential lithium insertion compounds is rather limited owing to the competition of insertion vs conversion reactions, the former being only favored for early 3d metal (Ti, V) oxides. Along that line, NaxVO2 was recently found to reversibly react with Na at ca. 1.5 V but sensibly lower operation voltages would be needed for enhanced energy density. Titanium-based systems are considered as best alternatives. Hence, Na2Ti3O7 was prepared from anatase TiO2 and anhydrous Na2CO3 mixtures with 10% excess of the latter with respect to stoichiometric amounts. These mixtures were milled and treated at 800ºC for 20 h with intermediate regrinding. X-ray diffraction pattern indicated the formation of pure crystalline phase as shown in the figure with space group P121/m.Based on the synthesized and characterized materials we assembled all-solid state sodium-ion batteries combining the alluaudite-type cathode with Na3PS4 as the solid electrolyte and Na2Ti3O7 as the anode. Favourable rate performance of the all solid state sodium-ion battery was demonstrated at room temperature. Figure 1

ChemInform Abstract: Syntheses and Structural Characterization of Non‐Centrosymmetric Na2M2M′S6 (M, M′: Ga, In, Si, Ge, Sn, Zn, Cd) Sulfides.

AbstractNa2Sn2ZnS6 (I), Na2Ga2GeS6 (II), Na2Ga2SnS6 (III), Na2Ga2SnS6 (IV), Na2Ge2ZnS6 (V), Na2Ge2CdS6 (VI), Na2In2SiS6 (VII), and Na2In2GeS6 (VIII) are prepared by solid state reactions, e.g. for (I) by the use of stoichiometric mixtures of Na2CO3, ZnS, and SnS in a continuous CS2 gas stream (Al2O3 boat in ceramic tube, 550 °C, 24 h).

ChemInform Abstract: Synthesis, Structure and Optical Properties of Two Isotypic Crystals, Na3MO4Cl (M: W, Mo).

AbstractPolycrystalline samples of the title compounds are synthesized by solid state reaction of stoichiometric mixtures of Na2CO3, WO3 or MoO3, and NaCl (565—580 °C, 72 h).

ChemInform Abstract: Na‐α′‐GeGaON Solid Solution Analogous to α′‐SiAlON: Synthesis, Crystal Structure, and Potentiality as a Photocatalyst.

AbstractThe polycrystalline Na‐α′‐GeGaON (NamGe12‐ (m+n)Gam+nOnN16‐n) solid solution is prepared as a single phase by gas reduction—nitridation of mixtures of Na2CO3, GeO2, and Ga2O3 in the solubility range of m ≈0.8—1.7 with n ≈0.2—0.3 (Al2O3 crucible, 875 °C, 4 h; NH3/1.5 vol% methane stream).

High electrical conductivity of nanocomposites based on Ce0.82Sm0.16Sr0.02O1.90 and (Li/Na)2 CO3 for low temperature solid oxide fuel cells

Ce0.82Sm0.16Sr0.02O1.90 (SSDC) based nanocomposites with different weight ratio of the eutectic mixture of Na2CO3–Li2CO3 have been prepared by mixing nanocrystalline powders of co-doped ceria with the carbonates. Single phase formation has been confirmed using X-ray diffraction (XRD). Samples sintered at 700°C are characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), thermal expansion and impedance analysis. SEM micrographs show a homogeneous distribution of both the phases. A sharp jump in the conductivity has been observed in all the composites at a particular temperature. This is attributed to a superionic transition at the interfaces formed between the ceria and the carbonate phases. Conductivity of the composites increases with increasing the carbonate content due to increase in the interfacial area between the two phases. Composition containing 35wt% of the carbonates shows the maximum conductivity, 7.48×10−2S-cm−1 at 500°C with activation energy of conduction 0.48eV. This value is one order of magnitude more than that of SSDC.

Synthesis and characterization of lead-free piezoelectric (K0.50Na0.50)NbO3 powder produced at lower calcination temperatures: A comparative study with a calcination temperature of 850 °C

To prevent the evaporation of alkali elements during the calcination of the lead-free piezoelectric K0.50Na0.50NbO3 (KNN), lower temperatures for the solid-state synthesis of the KNN from a mixture of Na2CO3, K2CO3 and Nb2O5 were investigated with a variety of powder-characterization techniques. The collected data suggested 550°C as a possible low calcination temperature, as well as being sufficiently high for a completed synthesis of the KNN. The XRD and TEM analyses of double-calcined KNN powder at 550°C revealed nanocrystalline, cube-shaped particles with a perovskite structure, but without noticeable unreacted precursors or secondary phases. Our investigations revealed that the morphology of the calcined powders underwent a dramatic change from small, differently shaped particles at 600°C/6h, to fully rounded, large, spherical agglomerates produced at 1000°C/6h. To explain this behavior, a mechanism involving the formation of a liquid phase during the reaction of the alkali elements with the moisture and CO2 in the atmosphere is proposed.

Soft chemical synthesis and electrochemical properties of calcium ferrite-type LixMn2O4

Calcium ferrite (CaFe2O4)-type LixMn2O4 was prepared via high-pressure and soft chemical synthesis method. The framework structure of CaFe2O4-type NaMn2O4 was synthesized from the stoichiometric mixture of Na2CO3 and MnO2 annealed by 1273 K for 1 h under 4.5 GPa. Na/Li ion-exchange of the CaFe2O4-type NaMn2O4 was carried out by soaking molten LiNO3 at 633 K for 12 h.The electrochemical properties of the ion-exchanged CaFe2O4-type LixMn2O4 were measured. The initial discharge profile in the voltage range from 4.0 to 1.0 V showed 458 mAh g−1 of the discharge capacity with two plateaus near 3.7 V and 2.7 V (vs. Li/Li+). The discharge capacity was decreased with increasing the cycle number. After 30 cycles, the capacity was decreased to 375 mAh g−1. When the range was set between 4.8 and 3.0 V, the discharge capacity was 113 mAh g−1 in initial, and 111 mAh g−1 after 50th cycle.The reference CaFe2O4-type LiMn2O4 was prepared via one-step high-pressure synthesis and compared the electrochemical properties with the ion-exchanged sample. The initial discharge capacity of the one-step synthesized one was 108 mAh g−1 at 1.0 V (vs. Li/Li+), which was 73% lower than the value of the ion-exchanged one.

Ionic transport in (nano)composites for fuel cells

Several composite materials were produced using ceria nanoparticles (<25 nm) and LiAlO2 (particle size >1 μm). The oxides were combined with a mixture of Na2CO3 and Li2CO3 (eutectic composition), and fired at temperatures in the 600–700 °C range (vacuum assisted in a few cases). The composites were characterized by scanning electron microscopy, X-ray diffraction and impedance spectroscopy, in air, in the 300–600 °C range. Irrespective of composition or grain size all samples exhibited the same type of conductivity dependence on temperature, with a steep change close to the carbonates eutectic temperature. At T > 500 °C all materials have identical conductivity, indicating that molten carbonates dominate the electrical performance. However, at low temperature (300–450 °C) significant differences can be noticed in all composites, with the best performance observed for ceria based composites with larger grain size (close to 135 nm).

ChemInform Abstract: Synthesis, Crystal Structure and Electrical Properties of a New Iron Arsenate Na2.77K1.52Fe2.57 (AsO4)4.

AbstractSingle crystals of Na2.77K1.52Fe2.57 (AsO4)4 are prepared by solid state reaction of a 1:1:1:5 molar mixture of Na2CO3, K2CO3, Fe(NO3)3, and NH4H2AsO4 (Pt crucible, 1.

ChemInform Abstract: A High‐Voltage and Ultralong‐Life Sodium Full Cell for Stationary Energy Storage.

AbstractA P2‐layered Na0.66Ni0.17Co0.17Ti0.66 O2 electrode material is prepared by solid state reaction of a stoichiometric mixture of Na2CO3, NiO, CoO, and TiO2 with a 5 wt% excess of Na2CO3 under Ar (900 °C, 15 h).

ChemInform Abstract: Synthesis, Structure and Luminescence Characteristics of a Novel Red Phosphor NaLa9(GeO4)6O2: Eu3+ for Light Emitting Diodes and Field Emission Displays.

AbstractNaLa9(GeO4)6O2:xEu3+ (x = 0—0.11) phosphors are prepared by firing a stoichiometric mixture of Na2CO3, La2O3, Eu2O3, and GeO2 in air (1.

ChemInform Abstract: Novel Mixed Cobalt/Chromium Phosphate NaCoCr2(PO4)3 Showing Spin‐Flop Transition.

AbstractThe new title compound is prepared by solid state reaction of a stoichiometric mixture of Na2CO3, Co(NO3)2, Cr(NO3)3, and (NH4)H2PO4 (Pt crucible, 1423 K, 48 h).

ChemInform Abstract: Growth, Structure, and Optical Properties of a Self‐Activated Crystal: Na3Nd9O3(BO3)8.

AbstractViolet crystals of the title compound are prepared from a mixture of Na2CO3, Nd2O3, B2O3, and NaF in the molar ratio of 9:2:14:10 (Pt crucible, 950 °C, 16 h).

ChemInform Abstract: Crystal Structure of Type Alluaudite KNa5Mn3(MoO4)6.

AbstractKNa5Mn3Mo6O24 is prepared by solid state reaction of a mixture of Na2CO3, K2CO3, Mn(OAc)3, and (NH4)2Mo4O13 in the molar ratio of Na:K:Mn:Mo = 1:1:2:3 (porcelain crucible, 950 K, 3 weeks; cooling to 900 K at a rate of 5 K/d).

ChemInform Abstract: Na3B4O7X (X: Cl, Br): Two New Borate Halides with a 1D Na‐X (X: Cl, Br) Chain Formed by the Face‐Sharing XNa6 Octahedra.

AbstractSingle crystals of Na3B4O7X (X: Cl, Br) are grown by spontaneous crystallization from a 1:1:3 molar mixture of Na2CO3, NaCl (NaBr), and H3BO3 (Pt crucible, 750 °C, 12 h;.

ChemInform Abstract: Synthesis and Characterization of a New Quaternary Borate Na2Cs2Sr(B9O15)2 with the Unprecedented [B9O19]11‐ Group, Notation of 3 x (3:2Δ + T).

AbstractSingle crystals of the new title compound are prepared from a powder mixture of Na2CO3, Cs2CO3, SrCO3, and H3BO3 in the molar ratio of Na:Cs:Sr:B = 2:3:2:17 (Pt crucible, 750 °C, 7 d).

ChemInform Abstract: Effect of Halogen (Cl, Br) on the Symmetry of Flexible Perovskite‐Related Framework.

AbstractOn the basis of the combination of B6O13 groups and XM6 (X: Cl, Br; M: Na, Rb) octahedra, Na3B6O10Cl (I), RbNa2B6O10Cl (II), and RbNa2B6O10Br (III) are prepared by solid state reaction of stoichiometric mixtures of Na2CO3, Rb2CO3, NaCl, NaBr, and H3BO3 (Pt crucible, 650—700 °C, 72 h).

Tungsten carbide coating on diamond particles in molten mixture of Na2CO3 and NaCl

Diamond compacts are prepared by bonding diamond particles with substrates. In the bonding process using a metal binder by electro-deposition, it is better to use diamond particles coated with tungsten carbide (WC) because of higher bonding efficiency between WC and the substrates caused by higher electric conductivity of WC. In this study, diamond particles were coated with WC in molten salts containing Na2CO3. Thermodynamically, sodium tungstate and WC were predicted to be generated by the reaction between metallic tungsten and Na2CO3, and the WC generation was confirmed experimentally. When the diamond powder and metallic tungsten powder were heated in a molten mixture of Na2CO3 and NaCl at 630–680°C, the diamond was coated with the WC generated by the reaction as mentioned above. Such treatment temperatures are lower than those in the previously proposed methods (800–1500°C). This reduces use of the heat quantity to raise the temperature of the feedstock by 50% compared with a NaCl bath process at 900°C. The specific resistance of the diamond particles decreased with increasing of the WC coating thickness, because of the WC layer with higher electric conductivity than diamond. The specific resistance of the diamond particles treated in a molten mixture of Na2CO3–NaCl was 220Ω·cm, whereas that of the diamond treated in a molten mixture of NaCl and KCl exceeded the upper detection limit in the used measurement system (>1948Ω·cm). Therefore, in a Na2CO3 containing molten mixture, the WC coating on the diamond particles proceeds effectively.