Supertetrahedral Networks and Lithium‐Ion Mobility in Li2SiP2 and LiSi2P3

The new phosphidosilicates Li₂SiP₂ and LiSi₂P₃ were synthesized by heating the elements at 1123 K and characterized by single‐crystal X‐ray diffraction. Li₂SiP₂ (I4₁/acd, Z=32, a=12.111(1) Å, c=18.658(2) Å) contains two interpenetrating diamond‐like tetrahedral networks consisting of corner‐sharing T2 supertetrahedra [(SiP_4/2)₄]. Sphalerite‐like interpenetrating networks of uniquely bridged T4 and T5 supertetrahedra make up the complex structure of LiSi₂P₃ (I4₁/a, Z=100, a=18.4757(3) Å, c=35.0982(6) Å). The lithium ions are located in the open spaces between the supertetrahedra and coordinated by four to six phosphorus atoms. Temperature‐dependent ⁷Li solid‐state MAS NMR spectroscopic data indicate high mobility of the Li⁺ ions with low activation energies of 0.10 eV in Li₂SiP₂ and 0.07 eV in LiSi₂P₃.     

Synthesis,Crystal Structure and Lithium Motion of Li8SeN2 and Li8TeN2

The compounds Li₈EN₂ with E = Se, Te were obtained in form of orange microcrystalline powders from reactions of Li₂E with Li₃N. Single crystal growth of Li₈SeN₂ additionally succeeded from excess lithium. The crystal structures were refined using single‐crystal X‐ray diffraction as well as X‐ray and neutron powder diffraction data (I4₁md, No. 109, Z = 4, Se: a = 7.048(1) Å, c = 9.995(1) Å, Te: a = 7.217(1) Å, c = 10.284(1) Å). Both compounds crystallize as isotypes with an anionic substructure motif known from cubic Laves phases and lithium distributed over four crystallographic sites in the void space of the anionic framework. Neutron powder diffraction pattern recorded in the temperature range from 3 K to 300 K and X‐ray diffraction patterns using synchrotron radiation taken from 300 K to 1000 K reveal the structural stability of both compounds in the studied temperature range until decomposition. Motional processes of lithium atoms in the title compounds were revealed by temperature dependent NMR spectroscopic investigations. Those are indicated by significant changes of the ⁷Li NMR signals. Lithium motion starts for Li₈SeN₂ above 150 K whereas it is already present in Li₈TeN₂ at this temperature. Quantum mechanical calculations of NMR spectroscopic parameters reveal clearly different environments of the lithium atoms determined by the electric field gradient, which are sensitive to the anisotropy of charge distribution at the nuclear sites. With respect to an increasing coordination number according to 2 + 1, 3, 3 + 1, and 4 for Li(3), Li(4), Li(2), and Li(1), respectively, the values of the electric field gradients decrease. Different environments of lithium predicted by quantum mechanical calculations are confirmed by ⁷Li NMR frequency sweep experiments at low temperatures.     

Lithium Ion Motion in Lithium Nitridoborate Chalcogenides Li5(BN2)Ch (Ch = Se,Te)

The compounds Li₅(BN₂)Se and Li₅(BN₂)Te were synthesized at 900 °C in a closed system utilizing weld shut niobium ampoules and obtained as white microcrystalline powders. Their crystal structures were solved and refined on the basis of single‐crystal X‐ray diffraction data with the space group I4₁md [a = 6.3983(4) Å, c = 11.1072(9) Å for Li₅(BN₂)Se and a = 6.5878(3) Å, c = 11.4382(7) Å for Li₅(BN₂)Te]. The temperature dependent Li⁺ motion was investigated by ⁷Li MAS NMR spectroscopy.     

Ionic conductivity of Li2MgSn3O8 ramsdellite

The ionic conductivity of polycrystalline pellets of Li₂MgSn₃O₈ with ramsdellite-type structure was measured by complex impedance technique. The conductivity is 1.2 × 10^?8 (Ω cm)^?1 at 300°C and 2.3 × 10^?4 (Ω cm)^?1 at 450°C. The results are discussed in relation to structural properties.     

Ionic conductivity of Li7BiO6

The ionic conductivity of polycrystalline Li₇BiO₆ pellets has been measured by complex impedence method. The conductivity is 5.7 × 10^?3 (Ω cm)^?1 and 300°C and 3.8 × 10^?6 (Ω cm)^?1 at 100°C. Li₇BiO₆ is the best lithium conductor among the structurally related Li_nMO₆ compounds.     

Neue Lithiumchlorid-Suzukiphasen: Li6MCl8(M = Fe,Co, Ni)

Novel Lithium Chloride Suzuki Phases, Li₆MCl₈ (M = Fe, Co, Ni) The hitherto unknown Suzuki phases Li₆FeCl₈, Li₆CoCl₈, and Li₆NiCl₈ ( cF 60) were prepared by fusing the binary chlorides. X-ray, DTA, and conductivity data as well as the infrared and Raman spectra are presented. The unit cell dimensions of the cubic (space group Fm3 m) halides are a = 1029.3, 1027.5, and 1023.5 pm, respectively. Li₆FeCl₈ and Li₆CoCl₈ undergo a reversible phase transition to disordered LiCl solid solutions at 275 and 355°C, respectively. The metastable nickel compound can only be prepared by quenching from about 560°C. The lithium chloride Suzuki phases are fast lithium ion conductors at elevated temperatures. The specific conductivities are 1.4 × 10^?1, 1.5 × 10^?1, and 6.9 × 10^?2Ω^?1 × cm^?1 at 500°C, respectively. Whereas the i.r. spectra of the Suzuki phases only reveal a broad band, the Raman spectra exhibit the four group theoretically allowed modes as sharp scattering peaks, which are discussed in terms of the vibrational modes of this structure.     

Polymorphism of Ba2SiP4

The three-dimensional SiP₄ network in the known phosphidosilicate Ba₂SiP₄-tI28 is analogous to β-Cristobalite if oxygen is formally replaced by P–P dimers. Here we report a second polymorph Ba₂SiP₄-oP56 [Pnma, a = 12.3710(4) Å, b = 14.6296(7) Å, c = 7.9783(3) Å; Z = 8] with chains of SiP₄ tetrahedra connected by P–P bonds, reminiscent to the elusive fibrous SiO₂. Ba₂SiP₄ is enantiotropic. The high temperature polymorph Ba₂SiP₄-oP56 transforms to the low-temperature phase Ba₂SiP₄-tI28 at 650 °C and reconstructs to the high-temperature modification at 1100 °C. DFT calculations predict an indirect optical bandgap of about 1.7 eV.     

Neue Oxoterbate(IV) mit Lithium Rb2Li14[Tb3O14] und Li6Tb2O7

New Oxoterbates(IV) with Lithium: On Rb₂Li₁₄[Tb₃O₁₄] and Li₆Tb₂O₇ For the first time we prepared Rb₂Li₁₄[Tb₃O₁₄] as yellow single crystals from Li₈TbO₆ and Rb₂O (Tb:Rb = 1:2) [Ag-cylinder, 500°C, 30 d, then Au-tube, 700°C, 27 d]. The structure refinement [652 I₀ (h kl), four circle diffractometer Philips PW 1100, ω-scan, MoKα, R = 4.69%, R_w = 3.24%, absorption considered, Immm with a = 1 283.07(10), b = 790.87(7), c = 736.87(7)pm, Z = 2, d_x = 4.30 g · cm^?3] confirms that it is isotypic with K₂Li₁₄[Pb₃O₁₄]. Furthermore we got for the first time Li₆Tb₂O₇ as a bright yellow compound from Li₂O₂ and “Tb₄O₇*” [(Li:Tb = 3.4:1), Au-ube, 750°C, 13 d (powder), 850°C 22 d (single crystals)] and by thermal decomposition of Rb₂Li₁₄[Tb₃O₁₄] (Au-tube, 850°C, 25 d). Powder and single crystal data [1 327 I₀ (h kl), four circle diffractometer PW 1100, ω-scan, AgKα, R = 9.38%, R_w = 5.23%, absorption not considered, P2₁/a, a = 1 056.30(10), b = 613.50(4), c = 546.56(5) pm, β = 109.668(7)°, Z = 2, d_x = 4.67 g · cm^?3 d_pyc = 4.53 g · cm^?3] reveal a new type of structure that may be deduced by the NaCl-type of structure. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Li17Sb13S28: A New Lithium Ion Conductor and addition to the Phase Diagram Li2S–Sb2S3

Li₁₇Sb₁₃S₂₈ was synthesized by solid‐state reaction of stoichiometric amounts of anhydrous Li₂S and Sb₂S₃. The crystal structure of Li₁₇Sb₁₃S₂₈ was determined from dark‐red single crystals at room temperature. The title compound crystallizes in the monoclinic space group C2/m (no. 12) with a=12.765(2) Å, b=11.6195(8) Å, c=9.2564(9) Å, β=119.665(6)°, V=1193.0(2) ų, and Z=4 (data at 20 °C, lattice constants from powder diffraction). The crystal structure contains one cation site with a mixed occupation by Li and Sb, and one with an antimony split position. Antimony and sulfur form slightly distorted tetragonal bipyramidal [SbS₅E] units (E=free electron pair). Six of these units are arranged around a vacancy in the anion substructure. The lone electron pairs E of the antimony(III) cations are arranged around these vacancies. Thus, a variant of the rock salt structure type with ordered vacancies in the anionic substructure results. Impedance spectroscopic measurements of Li₁₇Sb₁₃S₂₈ show a specific conductivity of 2.9×10^?9 Ω^?1 cm^?1 at 323 K and of 7.9×10^?6 Ω^?1 cm^?1 at 563 K, the corresponding activation energy is E_A=0.4 eV below 403 K and E_A=0.6 eV above. Raman spectra are dominated by the Sb?S stretching modes of the [SbS₅] units at 315 and 341 cm^?1 at room temperature. Differential thermal analysis (DTA) measurements of Li₁₇Sb₁₃S₂₈ indicate peritectic melting at 854 K.     

Fast Lithium Ion Conduction in Lithium Phosphidoaluminates

Solid electrolyte materials are crucial for the development of high‐energy‐density all‐solid‐state batteries (ASSB) using a nonflammable electrolyte. In order to retain a low lithium‐ion transfer resistance, fast lithium ion conducting solid electrolytes are required. We report on the novel superionic conductor Li₉AlP₄ which is easily synthesised from the elements via ball‐milling and subsequent annealing at moderate temperatures and which is characterized by single‐crystal and powder X‐ray diffraction. This representative of the novel compound class of lithium phosphidoaluminates has, as an undoped material, a remarkable fast ionic conductivity of 3 mS cm^?1 and a low activation energy of 29 kJ mol^?1 as determined by impedance spectroscopy. Temperature‐dependent ⁷Li NMR spectroscopy supports the fast lithium motion. In addition, Li₉AlP₄ combines a very high lithium content with a very low theoretical density of 1.703 g cm^?3. The distribution of the Li atoms over the diverse crystallographic positions between the [AlP₄]^9? tetrahedra is analyzed by means of DFT calculations.     

Fast Li Ion Dynamics in the Solid Electrolyte Li7P3S11 as Probed by 6,7Li NMR Spin‐Lattice Relaxation

The development of safe and long‐lasting all‐solid‐state batteries with high energy density requires a thorough characterization of ion dynamics in solid electrolytes. Commonly, conductivity spectroscopy is used to study ion transport; much less frequently, however, atomic‐scale methods such as nuclear magnetic resonance (NMR) are employed. Here, we studied long‐range as well as short‐range Li ion dynamics in the glass‐ceramic Li₇P₃S₁₁. Li⁺ diffusivity was probed by using a combination of different NMR techniques; the results are compared with those obtained from electrical conductivity measurements. Our NMR relaxometry data clearly reveal a very high Li⁺ diffusivity, which is reflected in a so‐called diffusion‐induced ⁶Li NMR spin‐lattice relaxation peak showing up at temperatures as low as 313 K. At this temperature, the mean residence time between two successful Li jumps is in the order of 3×10⁸ s^?1, which corresponds to a Li⁺ ion conductivity in the order of 10^?4 to 10^?3 S cm^?1. Such a value is in perfect agreement with expectations for the crystalline but metastable glass ceramic Li₇P₃S₁₁. In contrast to conductivity measurements, NMR analysis reveals a range of activation energies with values ranging from 0.17 to 0.26 eV, characterizing Li diffusivity in the bulk. In our case, through‐going Li ion transport, when probed by using macroscopic conductivity spectroscopy, however, seems to be influenced by blocking grain boundaries including, for example, amorphous regions surrounding the Li₇P₃S₁₁ crystallites. As a result of this, long‐range ion transport as seen by impedance spectroscopy is governed by an activation energy of approximately 0.38 eV. The findings emphasize how surface and grain boundary effects can drastically affect long‐range ionic conduction. If we are to succeed in solid‐state battery technology, such effects have to be brought under control by, for example, sophisticated densification or through the preparation of samples that are free of any amorphous regions that block fast ion transport.     

Single Lithium‐Ion Conducting Polymer Electrolytes Based on a Super‐Delocalized Polyanion

A novel single lithium‐ion (Li‐ion) conducting polymer electrolyte is presented that is composed of the lithium salt of a polyanion, poly[(4‐styrenesulfonyl)(trifluoromethyl(S‐trifluoromethylsulfonylimino)sulfonyl)imide] (PSsTFSI^?), and high‐molecular‐weight poly(ethylene oxide) (PEO). The neat LiPSsTFSI ionomer displays a low glass‐transition temperature (44.3 °C; that is, strongly plasticizing effect). The complex of LiPSsTFSI/PEO exhibits a high Li‐ion transference number (t_Li⁺=0.91) and is thermally stable up to 300 °C. Meanwhile, it exhibits a Li‐ion conductivity as high as 1.35×10^?4 S cm^?1 at 90 °C, which is comparable to that for the classic ambipolar LiTFSI/PEO SPEs at the same temperature. These outstanding properties of the LiPSsTFSI/PEO blended polymer electrolyte would make it promising as solid polymer electrolytes for Li batteries.     

Substitution of Lithium for Magnesium,Zinc, and Aluminum in Li15Si4: Crystal Structures,Thermodynamic Properties,as well as 6Li and 7Li NMR Spectroscopy of Li15Si4 and Li15−xMxSi4 (M=Mg,Zn, and Al)

An investigation into the substitution effects in Li₁₅Si₄, which is discussed as metastable phase that forms during electrochemical charging and discharging cycles in silicon anode materials, is presented. The novel partial substitution of lithium by magnesium and zinc is reported and the results are compared to those obtained for aluminum substitution. The new lithium silicides Li₁₄MgSi₄ ( 1 ) and Li_14.05Zn_0.95Si₄ ( 2 ) were synthesized by high‐temperature reactions and their crystal structures were determined from single‐crystal data. The magnetic properties and thermodynamic stabilities were investigated and compared with those of Li_14.25Al_0.75Si₄ ( 3 ). The substitution of a small amount of Li in metastable Li₁₅Si₄ for more electron‐rich metals, such as Mg, Zn, or Al, leads to a vast increase in the thermodynamic stability of the resulting ternary compounds_. The ^6,7Li NMR chemical shift and spin relaxation time T₁‐NMR spectroscopy behavior at low temperatures indicate an increasing contribution of the conduction electrons to these NMR spectroscopy parameters in the series for 1 – 3 . However, the increasing thermal stability of the new ternary phases is accompanied by a decrease in Li diffusivity, with 2 exhibiting the lowest activation energy for Li mobility with values of 56, 60, and 62 kJ mol^?1 for 2 , Li_14.25Al_0.75Si₁₄, and 1 , respectively. The influence of the metastable property of Li₁₅Si₄ on NMR spectroscopy experiments is highlighted.     

Synthesis,Structure and Thermodynamic Property of a New Lithium Borate: Li4[B8O13(OH)2]·3H2O

A new hydrated lithium borate, Li₄[B₈O₁₃(OH)₂]·3H₂O, has been hydrothermally synthesized and characterized by single crystal X‐ray diffraction, FT‐IR spectroscopy, simultaneous TGA‐DTA and chemical analysis. It crystallizes in the triclinic, space group , a=8.4578(5) Å, b=8.7877(5) Å, c=10.8058(7) Å, α=87.740(3)°, β=71.819(3)°, γ=61.569(3)°, Z=2, V=665.26(7) ų, D_c=2.043 g/cm³. Its crystal structure features polyborate anionic layers with the larger odd 13‐membered boron rings constructed by [B₈O₁₃(OH)₂]^4? FBBs. Through designing the thermochemical cycle, the standard molar enthalpy of formation of this borate was determined to be ?(7953.8±6.6) kJ·mol^?1 by using a heat conduction microcalorimeter.     

Low temperature synthesis of highly ion conductive Li7La3Zr2O12–Li3BO3 composites

Highly lithium ion conductive composites with Al-doped Li₇La₃Zr₂O₁₂ (LLZ) and amorphous Li₃BO₃ were prepared from sol–gel derived precursor powders of LLZ and Li₃BO₃. Precursor LLZ powders with cubic phase were obtained by a heat treatment of the precursor dried gel at 600 °C. Pellets of the mixture of the obtained LLZ and Li₃BO₃ were first held at 700 °C, and then successively sintered at 900 °C. Density of the sintered pellet with Li₃BO₃ was larger than that of the pellet without Li₃BO₃. From the TEM observation, the pellets were found to consist of cubic LLZ and amorphous Li₃BO₃. Total electrical conductivity of the obtained LLZ–Li₃BO₃ composite was 1 × 10^− 4 Scm^− 1 at 30 °C.     

Lithium aluminate-doped lithium orthosilicate: Sol-gel ceramics and lithium dynamics

Dense ceramics (Li_4+xSi_1−xAl_xO₄ with 0 ≤ x ≤ 0.3) are obtained by sintering at 700–900°C, without prior calcination, of sol-gel powders prepared by an alkoxide-hydroxide route. In comparison with the pure lithium orthosilicate (3 × 10⁻⁴ S · cm⁻¹ at 350°C), only a slight enhancement of the ionic conductivity is noted for monophase ceramics with Li₄SiO₄-type structure (5 × 10⁻⁴ S · cm⁻¹ at 350°C for x = 0.3). Higher conductivity (2 × 10⁻² S · cm⁻¹ at 350°C) is observed for an heterogeneous material formed of a lithium silicoaluminate phase (x = 0.2) with the Li₄SiO₄-type structure coexisting with lithium hydroxide. In this two-phase material, ac conductivity and ⁷Li spin-lattice relaxation data are consistent with the formation of a new kinetic path, via a thin layer along the interface, which enhances the lithium mobility.     

Reindarstellung und Kristallstruktur von Lithiumnitridhydrid,Li4NH,Li4ND

Preparation and Crystal Structure of Lithium Nitride Hydride, Li₄NH, Li₄ND Single phase Li₄NH was prepared by the reaction of Li₃N and LiH at 490°C. Its structure has been solved from x-ray and time-of-flight neutron powder diffraction data. Li₄NH crystallizes in an ordered variant of the Li₂O structure. N and H occupy the sites of two interpenetrating “extended” diamond lattices. Li occupies all N₂H₂ tetrahedral voids and is found to be shifted into a N₂H tetrahedral face. As a result H is in compressed tetrahedral coordination by Li, while N is in bisdisphenoidal coordination by Li. Alternatively, the Li₄NH structure may be regarded as a [Li₄N]⁺threedimensional net, its voids being filled up with H^?. Li₄NH is a reactive solid, which decomposes to imide when in contact with N₂ or H₂ at some 400°C.     

Li2C2, a High‐Capacity Cathode Material for Lithium Ion Batteries

As a typical alkaline earth metal carbide, lithium carbide (Li₂C₂) has the highest theoretical specific capacity (1400 mA h g^?1) among all the reported lithium‐containing cathode materials for lithium ion batteries. Herein, the feasibility of using Li₂C₂ as a cathode material was studied. The results show that at least half of the lithium can be extracted from Li₂C₂ and the reversible specific capacity reaches 700 mA h g^?1. The C?C bond tends to rotate to form C4 (C?C???C?C) chains during lithium extraction, as indicated with the first‐principles molecular dynamics (FPMD) simulation. The low electronic and ionic conductivity are believed to be responsible for the potential gap between charge and discharge, as is supported with density functional theory (DFT) calculations and Arrhenius fitting results. These findings illustrate the feasibility to use the alkali and alkaline earth metal carbides as high‐capacity electrode materials for secondary batteries.     

Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes

A series of group 4 metallocenes (RCp)[Cp―(bridge)―(2‐C₄H₃S)]MCl₂ [M = Ti ( C1 , C2 , C3 , C4 ); M = Zr ( C5 , C6 , C7 , C8 )] bearing a pendant thiophene group on a cyclopentadienyl ring have been synthesized, characterized and tested as catalyst precursors for ethylene polymerization. The molecular structures of representative titanocenes C2 and C4 were confirmed by single‐crystal X‐ray diffraction and revealed that both complexes exist in an expected coordination environment for a monomeric bent metallocene. No intramolecular coordination between the thiophene group and the titanium center could be observed in the solid state. Upon activation by methylaluminoxane (MAO), titanocenes C1 , C2 , C3 , C4 showed moderate catalytic activities and produced high‐ or ultra‐high‐molecular‐weight polyethylene (M_v 70.5–227.1 × 10⁴ g mol^?1). Titanocene C3 is more active and long‐lived, with a lifetime of nearly 9 h at 30 °C. At elevated temperatures of 80–110 °C, zirconocenes C5 , C6 , C7 , C8 displayed high catalytic activities (up to 27.6 × 10⁵ g PE (mol Zr)^?1 h^?1), giving high‐molecular‐weight polyethylene (M_v 11.2–53.7 × 10⁴ g mol^?1). Even at 80 °C, a long lifetime of at least 2 h was observed for the C8/MAO catalyst system. Copyright © 2014 John Wiley & Sons, Ltd.     

Enhanced Surface Interactions Enable Fast Li+ Conduction in Oxide/Polymer Composite Electrolyte

Li⁺‐conducting oxides are considered better ceramic fillers than Li⁺‐insulating oxides for improving Li⁺ conductivity in composite polymer electrolytes owing to their ability to conduct Li⁺ through the ceramic oxide as well as across the oxide/polymer interface. Here we use two Li⁺‐insulating oxides (fluorite Gd_0.1Ce_0.9O_1.95 and perovskite La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.55) with a high concentration of oxygen vacancies to demonstrate two oxide/poly(ethylene oxide) (PEO)‐based polymer composite electrolytes, each with a Li⁺ conductivity above 10^?4 S cm^?1 at 30 °C. Li solid‐state NMR results show an increase in Li⁺ ions (>10 %) occupying the more mobile A2 environment in the composite electrolytes. This increase in A2‐site occupancy originates from the strong interaction between the O^2? of Li‐salt anion and the surface oxygen vacancies of each oxide and contributes to the more facile Li⁺ transport. All‐solid‐state Li‐metal cells with these composite electrolytes demonstrate a small interfacial resistance with good cycling performance at 35 °C.