Pr5Si3N9

Single crystals of Pr5Si3N9, penta­praseodymium trisilicon nona­nitride, were obtained by the reaction of elemental praseo­dymium with silicon diimide in a radio-frequency furnace at 1873 K. The crystal structure consists of a chain-like Si—N substructure of corner-sharing SiN4 tetra­hedra. An additional Q 1-type [SiN4] unit is attached to every second tetra­hedron directed alternately in opposite directions. The resulting branched chains inter­lock with each other, building up a three-dimensional structure. The central atoms of the Q 1-type [SiN4] unit and of its attached tetra­hedron are situated on a mirror plane, as are two of the four crystallographically unique Pr3+ ions. The latter are coordinated by six to ten N atoms, with Pr—N distances similar to those of other rare earth nitridosilicates

New insights into the electrode/electrolyte interface on positive electrodes in Li-Ion batteries

International audienceUnderstanding and controlling the reactivity at the electrode/electrolyte interface (EEI) is one of the key issues for the development of high capacity and efficient lithium-ion batteries. The heterogeneous and partially catalytic reaction of the electrode with the electrolyte triggers the formation of surface films on the electrode surface which can cause degradation of the cell performance. Whereas the EEI layer properties are quite well known for negative electrodes such as lithium metal and graphite [1,2], the EEI layer on positive electrode materials is still puzzling. Especially the interface layers on high voltage and high capacity positive electrodes, whose potentials approach the limit of electrolyte stability against oxidation [3], is quite unexplored. One of the challenges in understanding the reactions at the surface of the electrode is the complicated composition of the positive electrodes, containing not only the active material but also conductive agents and polymeric binders, that can modify the EEI layers on the electrode. To bypass these ambiguities, there is a need for study model electrodes such as thin films or pure active material electrodes, which allow for investigating solely the reactivity of the electrolyte at the active material surface. Here, combining X-ray Photoelectron Spectroscopy (XPS and X-ray Absorption and Emission Spectroscopy (XAS/XES), of model electrodes, we will show how the species formed at the electrode/electrolyte interface are affected by change in charging potential and the structure and nature of the transition metal in the material. XES and XAS will be used to shed light on the change of electronic structure upon delithiation

Tuning mobility and stability of lithium ion conductors based on lattice dynamics

Lithium ion conductivity in many structural families can be tuned by many orders of magnitude, with some rivaling that of liquid electrolytes at room temperature. Unfortunately, fast lithium conductors exhibit poor stability against lithium battery electrodes. In this article, we report a fundamentally new approach to alter ion mobility and stability against oxidation of lithium ion conductors using lattice dynamics. By combining inelastic neutron scattering measurements with density functional theory, fast lithium conductors were shown to have low lithium vibration frequency or low center of lithium phonon density of states. On the other hand, lowering anion phonon densities of states reduces the stability against electrochemical oxidation. Olivines with low lithium band centers but high anion band centers are promising lithium ion conductors with high ion conductivity and stability. Such findings highlight new strategies in controlling lattice dynamics to discover new lithium ion conductors with enhanced conductivity and stability.United States. National Science Foundation. Graduate Research Fellowship Program (Grant 1122374)Taiwan. Ministry of Science and Technology (Grant 102-2917-I-564-006-A1)United States. National Science Foundation (Award DMR-0819762)United States. National Energy Research Scientific Computing Center (Contract DE-AC02-05CH11231)Extreme Science and Engineering Discovery Environment (Grant ACI-1548562

Li14Ln5[Si11N19O5]O2F2 with Ln = Ce, Nd-Representatives of a Family of Potential Lithium Ion Conductors

The isotypic layered oxonitridosilicates Li14Ln5[Si11N19O5]O2F2 (Ln = Ce, Nd) have been synthesized using Li as fluxing agent and crystallize in the orthorhombic space group Pmmn (Z = 2, Li14Ce5[Si11N19O5]O2F2: a = 17.178(3), b = 7.6500(15), c = 10.116(2) Å, R1 = 0.0409, wR2 = 0.0896; Li14Nd5 Si11N19O5]O2F2: a = 17.126(2), b = 7.6155 15), c = 10.123(2) Å, R1 = 0.0419, wR2 = 0.0929). The silicate layers consist of dreier and sechser rings interconnected via common corners, yielding an unprecedented silicate substructure. A topostructural analysis indicates possible 1D ion migration pathways between five crystallographic independent Li positions. The specific Li-ionic conductivity and its temperature dependence were determined by impedance spectroscopy as well as DC polarization/depolarization measurements. The ionic conductivity is on the order of 5 × 10−5 S/cm at 300°C, while the activation energy is 0.69 eV. Further adjustments of the defect chemistry (e.g., through doping)can make these compounds interesting candidates for novel oxonitridosilicate based ion conductors

Li₁₄Ln₅[Si₁₁N₁₉O₅]O₂F₂ with Ln = Ce, NdRepresentatives of a Family of Potential Lithium Ion Conductors

The isotypic layered oxonitridosilicates Li₁₄Ln₅[Si₁₁N₁₉O₅]­O₂F₂ (Ln = Ce, Nd) have been synthesized using Li as fluxing agent and crystallize in the orthorhombic space group <i>Pmmn</i> (<i>Z</i> = 2, Li₁₄Ce₅[Si₁₁N₁₉O₅]­O₂F₂: <i>a</i> = 17.178(3), <i>b</i> = 7.6500(15), <i>c</i> = 10.116(2) Å, <i>R</i>1 = 0.0409, <i>wR</i>2 = 0.0896; Li₁₄Nd₅[Si₁₁N₁₉O₅]­O₂F₂: <i>a</i> = 17.126(2), <i>b</i> = 7.6155(15), <i>c</i> = 10.123(2) Å, <i>R</i>1 = 0.0419, <i>wR</i>2 = 0.0929). The silicate layers consist of <i>dreier</i> and <i>sechser</i> rings interconnected via common corners, yielding an unprecedented silicate substructure. A topostructural analysis indicates possible 1D ion migration pathways between five crystallographic independent Li positions. The specific Li-ionic conductivity and its temperature dependence were determined by impedance spectroscopy as well as DC polarization/depolarization measurements. The ionic conductivity is on the order of 5 × 10^–5 S/cm at 300 °C, while the activation energy is 0.69 eV. Further adjustments of the defect chemistry (e.g., through doping) can make these compounds interesting candidates for novel oxonitridosilicate based ion conductors

Li₁₄Ln₅[Si₁₁N₁₉O₅]O₂F₂ with Ln = Ce, NdRepresentatives of a Family of Potential Lithium Ion Conductors

The isotypic layered oxonitridosilicates Li₁₄Ln₅[Si₁₁N₁₉O₅]­O₂F₂ (Ln = Ce, Nd) have been synthesized using Li as fluxing agent and crystallize in the orthorhombic space group <i>Pmmn</i> (<i>Z</i> = 2, Li₁₄Ce₅[Si₁₁N₁₉O₅]­O₂F₂: <i>a</i> = 17.178(3), <i>b</i> = 7.6500(15), <i>c</i> = 10.116(2) Å, <i>R</i>1 = 0.0409, <i>wR</i>2 = 0.0896; Li₁₄Nd₅[Si₁₁N₁₉O₅]­O₂F₂: <i>a</i> = 17.126(2), <i>b</i> = 7.6155(15), <i>c</i> = 10.123(2) Å, <i>R</i>1 = 0.0419, <i>wR</i>2 = 0.0929). The silicate layers consist of <i>dreier</i> and <i>sechser</i> rings interconnected via common corners, yielding an unprecedented silicate substructure. A topostructural analysis indicates possible 1D ion migration pathways between five crystallographic independent Li positions. The specific Li-ionic conductivity and its temperature dependence were determined by impedance spectroscopy as well as DC polarization/depolarization measurements. The ionic conductivity is on the order of 5 × 10^–5 S/cm at 300 °C, while the activation energy is 0.69 eV. Further adjustments of the defect chemistry (e.g., through doping) can make these compounds interesting candidates for novel oxonitridosilicate based ion conductors

Li₁₄Ln₅[Si₁₁N₁₉O₅]O₂F₂ with Ln = Ce, NdRepresentatives of a Family of Potential Lithium Ion Conductors

The isotypic layered oxonitridosilicates Li₁₄Ln₅[Si₁₁N₁₉O₅]­O₂F₂ (Ln = Ce, Nd) have been synthesized using Li as fluxing agent and crystallize in the orthorhombic space group <i>Pmmn</i> (<i>Z</i> = 2, Li₁₄Ce₅[Si₁₁N₁₉O₅]­O₂F₂: <i>a</i> = 17.178(3), <i>b</i> = 7.6500(15), <i>c</i> = 10.116(2) Å, <i>R</i>1 = 0.0409, <i>wR</i>2 = 0.0896; Li₁₄Nd₅[Si₁₁N₁₉O₅]­O₂F₂: <i>a</i> = 17.126(2), <i>b</i> = 7.6155(15), <i>c</i> = 10.123(2) Å, <i>R</i>1 = 0.0419, <i>wR</i>2 = 0.0929). The silicate layers consist of <i>dreier</i> and <i>sechser</i> rings interconnected via common corners, yielding an unprecedented silicate substructure. A topostructural analysis indicates possible 1D ion migration pathways between five crystallographic independent Li positions. The specific Li-ionic conductivity and its temperature dependence were determined by impedance spectroscopy as well as DC polarization/depolarization measurements. The ionic conductivity is on the order of 5 × 10^–5 S/cm at 300 °C, while the activation energy is 0.69 eV. Further adjustments of the defect chemistry (e.g., through doping) can make these compounds interesting candidates for novel oxonitridosilicate based ion conductors