Ruthenium‐Oxide‐Coated Sodium Vanadium Fluorophosphate Nanowires as High‐Power Cathode Materials for Sodium‐Ion Batteries

Sodium‐ion batteries are a very promising alternative to lithium‐ion batteries because of their reliance on an abundant supply of sodium salts, environmental benignity, and low cost. However, the low rate capability and poor long‐term stability still hinder their practical application. A cathode material, formed of RuO₂‐coated Na₃V₂O₂(PO₄)₂F nanowires, has a 50 nm diameter with the space group of I4/mmm. When used as a cathode material for Na‐ion batteries, a reversible capacity of 120 mAh g^?1 at 1 C and 95 mAh g^?1 at 20 C can be achieved after 1000 charge–discharge cycles. The ultrahigh rate capability and enhanced cycling stability are comparable with high performance lithium cathodes. Combining first principles computational investigation with experimental observations, the excellent performance can be attributed to the uniform and highly conductive RuO₂ coating and the preferred growth of the (002) plane in the Na₃V₂O₂(PO₄)₂F nanowires.     

A Self‐Healing Aqueous Lithium‐Ion Battery

Flexible lithium‐ion batteries are critical for the next‐generation electronics. However, during the practical application, they may break under deformations such as twisting and cutting, causing their failure to work or even serious safety problems. A new family of all‐solid‐state and flexible aqueous lithium ion batteries that can self‐heal after breaking has been created by designing aligned carbon nanotube sheets loaded with LiMn₂O₄ and LiTi₂(PO₄)₃ nanoparticles on a self‐healing polymer substrate as electrodes, and a new kind of lithium sulfate/sodium carboxymethylcellulose serves as both gel electrolyte and separator. The specific capacity, rate capability, and cycling performance can be well maintained after repeated cutting and self‐healing. These self‐healing batteries are demonstrated to be promising for wearable devices.     

Synthesis of Ammonium‐ and 4‐Dimethylaminopyridinium Amidofluorophosphates and Crystal Structure of [DMAPH][PO2F(NH2)]

NH₄[PO₂F(NH₂)] has been prepared by the reaction of a betaine py·PO₂F with excess ammonia in acetonitrile solution, while the ammonolysis of DMAP·PO₂F with a stoichiometric amount of NH₃ yields [DMAPH][PO₂F(NH₂)]. The crystal structure of the latter was determined by single‐crystal X‐ray diffraction, which revealed that the anions [PO₂F(NH₂)]^— are linked to infinite chains by double N—H···O bridges. Additional strong N—H···O bridging bonds connect each anion with its [DMAPH]⁺ counterion. The formation of a new betaine NH₃·PO₂F in the solution of py·PO₂F in liquid ammonia was proved by ³¹P NMR spectroscopy and by identification of its hydrolysis products.     

Synthesis of Two‐Dimensional Transition‐Metal Phosphates with Highly Ordered Mesoporous Structures for Lithium‐Ion Battery Applications

Materials with ordered mesoporous structures have shown great potential in a wide range of applications. In particular, the combination of mesoporosity, low dimensionality, and well‐defined morphology in nanostructures may exhibit even more attractive features. However, the synthesis of such structures is still challenging in polar solvents. Herein, we report the preparation of ultrathin two‐dimensional (2D) nanoflakes of transition‐metal phosphates, including FePO₄, Mn₃(PO₄)₂, and Co₃(PO₄)₂, with highly ordered mesoporous structures in a nonpolar solvent. The as‐obtained nanoflakes with thicknesses of about 3.7 nm are constructed from a single layer of parallel‐packed pore channels. These uniquely ordered mesoporous 2D nanostructures may originate from the 2D assembly of cylindrical micelles formed by the amphiphilic precursors in the nonpolar solvent. The 2D mesoporous FePO₄ nanoflakes were used as the cathode for a lithium‐ion battery, which exhibits excellent stability and high rate capabilities.     

Kristallstrukturen und thermisches Verhalten von Metalldihydrogenphosphat‐HF‐Addukten MH2PO4 · HF (M = K,Rb, Cs) mit Wasserstoffbrückenbindungen vom Typ F–H…O

Structures and Thermal Behaviour of Alkali Metal Dihydrogen Phosphate HF Adducts, MH₂PO₄ · HF (M = K, Rb, Cs), with Hydrogen Bonds of the F–H…O Type Three HF adducts of alkali metal dihydrogen phosphates, MH₂PO₄ · HF (M = K, Rb, Cs), have been isolated from fluoroacidic solutions of MH₂PO₄. KH₂PO₄ · HF crystallizes monoclinic: P2₁/c, a = 6,459(2), b = 7,572(2), c = 9,457(3) Å, β = 101,35(3)°, V = 453,5(3) ų, Z = 4. RbH₂PO₄ · HF and CsH₂PO₄ · HF are orthorhombic: Pna2₁, a = 9,055(3), b = 4,635(2), c = 11,908(4) Å, V = 499,8(3) ų, Z = 4, and Pbca, a = 7,859(3), b = 9,519(4), c = 14,744(5) Å, V = 1102,5(7) ų, Z = 8, respectively. The crystal structures of MH₂PO₄ · HF contain M⁺ cations, H₂PO₄^– anions and neutral HF molecules. The H₂PO₄^– anions are connected to layers by O–H…O hydrogen bonds (2,53–2,63 Å), whereas the HF molecules are attached to the layers via very short hydrogen bonds of the F‐H…O type (2,36–2,38 Å). The thermal decomposition of the adducts proceeds in three steps. The first step corresponds to the release of mainly HF and a smaller quantity of water. In the second and third steps, water evolution caused by condensation of dihydrogen phosphate is the dominating process whereas smaller amounts of HF are also released.     

Li6PO5Br and Li6PO5Cl: The first Lithium‐Oxide‐Argyrodites

The title compounds Li₆PO₅Br (Fand Li₆PO₅Cl (F represent the first oxidic argyrodites in general and the first lithiumoxoargyrodites in particular. The overall crystal structure corresponds to the cubic high temperature (HT) modification of all known cubic argyrodites, however, with a seemingly small but important difference concerning the lithium positions. In all other HT argyrodites with similar lithium content the 24 lithium atoms per unit cell are disordered over a 48 fold position in close vicinity to a 24 fold one causing a high mobility of the Li⁺. In the title compounds, however, they occupy the 24 fold one in a strictly ordered manner thus establishing a planar triangular first sphere coordination environment. This detail is of great importance for the amount of the specific lithium ionic conductivity and for the possible phase transition to an LT (low temperature) modification accompanied by an ordering of the disordered lithium atoms. Apparently the latter transition is suppressed in the title compounds because the Li⁺ are already frozen out in the cubic (HT = LT) form. The initially open question how this structural peculiarity influences the ionic conductivity (strengthening or weakening in comparison to oxygen free argyrodites?) is answered by a series of impedance measurements. The specific lithium ionic conductivity of the title compounds in the range 313 K < T < 518 K is significantly lower than in oxygen free argyrodites.     

Pseudo‐Isomerie durch unterschiedliche Jahn‐Teller‐Ordnung: Die Kristallstrukturen des Hemihydrats und des Monohydrats von (pyH)[MnF(H2PO4)(HPO4)]

Pseudo‐Isomerism by Different Jahn‐Teller Ordering: Crystal Structures of the Hemihydrate and the Monohydrate of (pyH)[MnF(H₂PO₄)(HPO₄)] With pyridinium counter cations (pyH⁺) the Mn^III fluoride phosphate anion [MnF(H₂PO₄)(HPO₄)]^— can be stabilized. It forms a chain structure with Mn³⁺ ions bridged by a fluoride ion and two bidentate phosphate groups. Under sleightly differing conditions either the hemihydrate (pyH)[MnF(H₂PO₄)(HPO₄)]·0.5H₂O ( 1 ) or the monohydrate (pyH)[MnF(H₂PO₄)(HPO₄)]·H₂O ( 2 ) is formed. The hemihydrate 1 crystallizes monoclinic in space group P2₁/n, Z = 8, a = 7.295(1), b = 17.052(2), c = 18.512(3) Å, β = 100.78(1)°, R = 0.033, the monohydrate triclinic in space group P1¯, Z = 2, a = 7.374(1), b = 8.628(1), c = 10.329(1) Å, α = 83.658(8)°, β = 77.833(9)°, γ = 68.544(8)°, R = 0.025. Whereas the topology of the chain anions is identical in both structures, the Jahn‐Teller effect is expressed in different ordering patterns: in 1 antiferrodistortive ordering of [MnF₂O₄] octahedra is observed, with alternating elongation of an F—Mn—F‐axis or a O—Mn—O‐axis, respectively. This leads to asymmetrical Mn—F—Mn‐bridges. In 2 ferrodistortive ordering is found, with elongation of all octahedra along the F—Mn—F‐axis. Thus, symmetrical bridges are formed with long Mn—F distances. This unusual pseudo‐isomerism is attributed to the differing influence of inter‐chain hydrogen bonds.     

1,2‐Diaza‐3‐silacyclopent‐5‐ene – Synthese und Reaktionen

1,2‐Diaza‐3‐silacyclopent‐5‐ene – Synthesis and Reactions The dilithium salt of bis(tert‐butyl‐trimethylsilylmethylen)ketazine ( 1 ) forms an imine‐enamine salt. 1 reacts with halosilanes in a molar ratio of 1:1 to give 1,2‐diaza‐3‐silacyclopent‐5‐enes. Me₃SiCH=CCMe₃ [N(SiR,R′)‐N=C‐C]HSiMe₃ ( 2 ‐ 7 ). ( 2 : R,R′ = Cl; 3 : R = CH₃, R′ = Ph; 4 : R = F, R′ = CMe₃; 5 : R = F, R′ = Ph; 6 : R = F, R′ = N(SiMe₃)₂; 7 : R = F, R′ = N(CMe₃)SiMe₃). In the reaction of 1 with tetrafluorosilane the spirocyclus 8 is isolated. The five‐membered ring compounds 2 ‐ 7 and compound 9 substituted on the silicon‐fluoro‐ and (tert‐butyltrimethylsilyl) are acid at the C(4)‐atom and therefore can be lithiated. Experiments to prepare lithium salts of 4 with MeLi, n‐BuLi and PhLi gave LiF and the substitution‐products 10 ‐ 12 . 9 forms a lithium salt which reacts with ClSiMe₃ to give LiCl and the SiMe₃ ring system ( 13 ) substituted at the C(4)‐atom. The ring compounds 3 ‐ 7 and 10 ‐ 12 form isomers, the formation is discussed. Results of the crystal structure and analyses of 8 , 10 , 12 , and 13 are presented.     

Festkörper‐NMR‐Untersuchungen an Natriumoxothiophosphaten(V)

Solid State NMR Investigations on Sodium Oxothiophosphates(V) Sodium monothiophosphate(V) Na₃PO₃S is dimorphic. The metastable high temperature modification β‐Na₃PO₃S crystallizes hexagonal with a = 8.996(4) and c = 5.216(2)Å. According to ³¹P solid state NMR experiments, α‐Na₃PO₃S exhibits at 20 °C a non‐axial‐symmetric environment for the phosphorus nuclei in contrast to the results of the refined crystal structure. This discrepancy is discussed assuming ordered and disordered structural models. However, at 490 °C the chemical shift tensor of the phosphorus nuclei in α‐Na₃PO₃S is axial‐symmetric. So, the distortion of the phosphorus environment is abolished by the thermal motion of the atoms. The number of crystallographically distinguishable positions for phosphorus and for sodium in Na₃PO₂S₂ and Na₃POS₃ can be confirmed in good agreement with their crystal structures using solid state NMR spectroscopy.     

Phase formation in the InPO<Subscript>4</Subscript>-Na<Subscript>3</Subscript>PO<Subscript>4</Subscript>-Li<Subscript>3</Subscript>PO<Subscript>4</Subscript> ternary system

The 950°C isothermal section of the InPO₄-Na₃PO₄-Li₃PO₄ ternary system was studied and constructed; one-, two, and three-phase fields are outlined. Five solid-solution regions exist in the system: solid solutions based on the complex phosphate LiNa₅(PO₄)₂ (olympite structure), the indium ion stabilized high-temperature Na₃PO₄ phase (Na_{3(1 − x)}In _x (PO₄); space group Fm [`3]\bar 3 m), the complex phosphate Na₃In₂(PO₄)₃, and the α and β phases of the compound Li₃In₂(PO₄)₃. A narrow region of melt was found in the vicinity of eutectic equilibria. All the phases detected in the system are derivatives of phases existing in the binary subsystems. Isovalent substitution of lithium for sodium in Na₃In₂(PO₄)₃ leads to a significant increase in the region of a NASICON-like solid solution.     

ChemInform Abstract: Electronic Structure,Elastic Anisotropy,Thermal Conductivity and Optical Properties of Calcium Apatite Ca5(PO4)3X (X: F,Cl or Br).

The structural properties, phase stability, electronic structure, elastic properties, and optical properties of Ca₅(PO₃)₄F (FA), Ca₅(PO₃)₄Cl (ClA) and Ca₅(PO₃)₄Br (BrA) are studied by DFT calculations with the generalized gradient approximation.     

Base‐Stabilized [PO]+/[PO2]+ Cations

The salts [(BAC)₂PO][BF₄] ( 5 ) and [(BAC)₂PO₂][BF₄] ( 4 ) (BAC=bis(diisopropylamino) cyclopropenylidene), consisting of the PO⁺ and PO₂⁺ cations, respectively, coordinated to the singlet carbenes, have been prepared. Computational investigations reveal that the electronic structure of the PO⁺ cation is a hybrid between the charge‐localized and charge‐delocalized resonance forms, resulting in ambiphilic reactivity. Compound 5 reacts as a donor with the transition‐metal complex K₂PtCl₄ to furnish [[(BAC)₂PO]₂PtCl₂][BF₄]₂ ( 6 ) and KCl. Remarkably, both 5 and 4 have shown to act as electrophiles undergoing reactions with fluoride anion, leading to [OPF₂]^? and (BAC)PO₂F, respectively.     

Dirubidium fluoro­trioxophosphate,Rb2PO3F,at 290 and 130 K,and dicaesium fluoro­trioxophosphate,Cs2PO3F,at 240 and 100 K

The structure of Rb₂PO₃F was determined at 290 and 130 K, while that of Cs₂PO₃F was determined at 240 and 100 K. Both compounds belong to the β‐K₂SO₄ family. The structure analysis did not reveal signs of a phase transition in either compound. Crystal chemical considerations do not favour the presence of a phase transition in either Rb₂PO₃F or Cs₂PO₃F. However, glass‐like phase transitions were observed by differential scanning calorimetry in slightly humid samples at 175 and 177 K for Rb₂PO₃F and Cs₂PO₃F, respectively, but were not observed in well dried samples. The bond distances are normal and Cs₂PO₃F is twinned.     

Topotactic insertion of lithium in the layered structure Li4VO(PO4)2: The tunnel structure Li5VO(PO4)2

A new V(III) lithium phosphate Li₅VO(PO₄)₂ has been synthesized by electrochemical insertion of lithium into Li₄VO(PO₄)₂. This phase, which crystallizes in the space group I4/mcm, exhibits a tunnel structure closely related to the layered structure of Li₄VO(PO₄)₂ and to the tunnel structure of VO(H₂PO₄)₂. The topotactic reactions that take place during lithium exchange and intercalation, starting from VO(H₂PO₄)₂ and going to the final phase Li₅VO(PO₄)₂ are explained on the basis of the flexible coordinations of V⁴⁺ and V³⁺ species. The electrochemical and magnetic properties of this new phase are also presented and explained on the basis of the structure dimensionality.     

Olefin Insertion into a Pd–F Bond: Catalyst Reactivation Following β‐F Elimination in Ethylene/Vinyl Fluoride Copolymerization

The discrete (phosphinoarenesulfonate)Pd fluoride complex (PO^Bp,OMe)PdF(lutidine), where PO^Bp,OMe=(2‐MeOC₆H₄)(2‐{2,6‐(MeO)₂C₆H₃}C₆H₄)(2‐SO₃‐5‐MeC₆H₃)P, inserts vinyl fluoride (VF) to form (PO^Bp,OMe)PdCH₂CHF₂(lutidine) and inserts multiple ethylene (E) units to generate polyethylene that contains −CH₂F chain ends. These results provide strong evidence that the −CHF₂ and −CH₂F chain ends in E/VF copolymer generated by (phosphinoarenesulfonate)PdR catalysts form by β‐F elimination of Pd(β‐F‐alkyl) species, VF or E insertion of the resulting (PO)PdF species, and subsequent chain growth. These results also imply that β‐F elimination is not an important catalyst deactivation reaction in this system.     

catena‐Poly[bis(ethane‐1,2‐diammonium) [manganese(II)‐di‐μ‐phosphato‐κ4O:O′]]: a one‐dimensional manganese phosphate

The title compound, {(C₂H₁₀N₂)₂[Mn(PO₄)₂]}_n, contains anionic square‐twisted chains of formula [Mn(PO₄)₂]⁴⁻ constructed from corner‐sharing four‐membered rings of alternating MnO₄ and PO₄ units. The Mn and P atoms have distorted tetrahedral coordination and the Mn atom lies on a twofold axis. The linear manganese–phosphate chains are held together by hydrogen‐bonding interactions involving the framework O atoms and the H atoms of the ethane‐1,2‐diammonium cations, which lie in the interchain spaces.     

ChemInform Abstract: Labile Degree of Disorder in Bismuth‐Oxophosphate Compounds: Illustration Through Three New Structural Types.

Single crystals of [Bi₂(Bi_1.56K_0.44)O₃] K_0.88(PO₄)₂ (I), [Bi₁₀ (Bi_0.5Cd_0.5)₈O₁₆] (Bi_0.6Cd_0.8)₂(PO₄)₈ (II), and [Bi₁₈Zn₁₀O₂₁] Zn₅(PO₄)₁₄ (III) are prepared by melting K₂CO₃ (or CdO or ZnO), Bi₂O₃, and (NH₄)₂HPO₄ in a 1:1:2 molar ratio (open Au tube, 900—950 °C, 10 h).     

Monodisperse Sandwich‐Like Coupled Quasi‐Graphene Sheets Encapsulating Ni2P Nanoparticles for Enhanced Lithium‐Ion Batteries

In this report, sandwiched Ni₂P nanoparticles encapsulated by graphene sheets are first synthesized by directly encapsulating functional units in graphene sheets instead of fabricating separate graphene sheets and then immobilizing the functional components onto the generated surfaces. In this strategy, we use low‐cost, sustainable and environmentally friendly glucose as a carbon source and NiNH₄PO₄ ? H₂O nanosheets as sacrificial templates. This unique structure obtained here cannot only prevent the nanoparticles from aggregation or loss but also enhance the electronic conductivity compared to the independent nanoparticles. Furthermore, the novel sandwich‐like Ni₂P/C can be applied in plenty of fields, especially in electrical energy storage. In this paper, a series of electrochemical tests of the sandwich‐like Ni₂P/C are carried out, which demonstrate the excellent cyclic stability and rate capacity for lithium‐ion batteries.     

Neue Zirconiumphosphatfluoride mit 3D‐Gerüststruktur

New Zirconium Phosphate Fluorides with 3D‐Framework From aqueous solutions of ZrOCl₂, H₃PO₄, HF, and various amines, two new compounds of the general formula [amH₂]_1/2[Zr₂(HPO₄)(PO₄)₂F] · nH₂O ( I : am = N,N‐dimethylethylenediamine, n = 0,5; II : am = N,N‐dimethyl‐1,3‐diaminopropane, n = 0) adopting the ZrPOF‐1 structure type have been synthesized under hydrothermal conditions. In contrast to the monoclinic ZrPOF‐1, both compounds crystallize in the space group P 1 with a = 6.611(3), b = 9.109(4), c = 11.560(5) Å, α = 85.62(4), β = 89.60(4), γ = 70.57(4)° in I , and a = 6.616(2), b = 9.045(3), c = 11.565(4) Å, α = 85.26(4), β = 88.86(4), γ = 71.46(4)° in II . Compound III (am = ethylenediamine, n = 0) has been obtained by dehydration of ZrPOF‐1 and occurs in the space group P1 with a = 6.605(2), b = 8.787(3), c = 11.499(5) Å, α = 93.07(4), β = 90.42(4) and γ = 104.66(4)°. The structural motifs of the frameworks of the three compounds have much in common. The template and the PO₃OH tetrahedra in I and II are disordered. Differences in the water content in both compounds are due to differences in the chain lengths of the amines. The absence of crystal water in compound III breaks the template disordering which is present in ZrPOF‐1. The rotation of the PO₃OH tetrahedra in II and III compared with I and ZrPOF‐1 is discussed in regard with the absence of stabilizing H‐bridges in the former compounds.     

Li3PO4‐Coated LiNi0.5Mn1.5O4: A Stable High‐Voltage Cathode Material for Lithium‐Ion Batteries

LiNi_0.5Mn_1.5O₄ is regarded as a promising cathode material to increase the energy density of lithium‐ion batteries due to the high discharge voltage (ca. 4.7 V). However, the interface between the LiNi_0.5Mn_1.5O₄ cathode and the electrolyte is a great concern because of the decomposition of the electrolyte on the cathode surface at high operational potentials. To build a stable and functional protecting layer of Li₃PO₄ on LiNi_0.5Mn_1.5O₄ to avoid direct contact between the active materials and the electrolyte is the emphasis of this study. Li₃PO₄‐coated LiNi_0.5Mn_1.5O₄ is prepared by a solid‐state reaction and noncoated LiNi_0.5Mn_1.5O₄ is prepared by the same method as a control. The materials are fully characterized by XRD, FT‐IR, and high‐resolution TEM. TEM shows that the Li₃PO₄ layer (<6 nm) is successfully coated on the LiNi_0.5Mn_1.5O₄ primary particles. XRD and FT‐IR reveal that the synthesized Li₃PO₄‐coated LiNi_0.5Mn_1.5O₄ has a cubic spinel structure with a space group of Fd$\bar 3$ m, whereas noncoated LiNi_0.5Mn_1.5O₄ shows a cubic spinel structure with a space group of P4₃32. The electrochemical performance of the prepared materials is characterized in half and full cells. Li₃PO₄‐coated LiNi_0.5Mn_1.5O₄ shows dramatically enhanced cycling performance compared with noncoated LiNi_0.5Mn_1.5O₄.