Search

A comprehensive understanding of the nexus of diffusion mechanisms on the atomic scale as well as structural influences on the ionic motion in solid electrolytes is key for further development of high-performing all-solid-state batteries. Therefore, current research not only focuses on the search for innovative materials, but also on the study of diffusion pathways and ion dynamics in ionic conductors. In this context, we report on the extended characterization of the ionic electrolyte Li6.5La3Zr1.5Nb0.5O12 (LLZO-Nb). The commercially available material is analyzed by a combination of powder X-ray (either lab- or synchrotron-based) and neutron diffraction. Details of lithium disorder were obtained from high-resolution neutron diffraction data, from which the ionic transport of Li ions was determined by applying the maximum entropy method in combination with the one-particle potential formalism.

CoIn2 (Z. Metallkd. 1970, 61, 342–343) forms by reaction of the elements at 1470 K followed by annealing at 770 K for five days. The room temperature structure is orthorhombic (CuMg2 type, Fddd, a = 529.95(10), b = 940.49(13), c = 1785.8(3) pm, wR2 = 0.0563, 444 F 2 values, 17 variables) and shows a phase transition at 195(1) K (DSC data). The low-temperature modification crystallizes in the translationengleiche monoclinic subgroup C2/c and exhibits a new structure type (a = 933.7(7), b = 526.91(10), c = 1000.8(2) pm, β = 117.81(5)°, wR2 = 0.0374, 843 F 2 values, 30 variables). The structural phase transition is a consequence of a Peierls type distortion. The equidistant cobalt chains in HT-CoIn2 (270.1 pm, 175.2° Co–Co–Co) show pairwise dislocation in LT-CoIn2 with shorter (252.4 pm) and longer (284.1 pm) Co–Co distances. Each cobalt atom has coordination number 10 in the form of slightly distorted square antiprisms of indium, capped by cobalt on the rectangular faces. Density-of-states calculations reveal metallic behavior for both modifications. Integrated crystal orbital overlap populations featuring the bonding characteristics indicate a slightly higher intensity area for LT-CoIn2 along with a shift to lower energy, manifesting the stabilization by pair formation through Peierls distortion.

Synthesis, modification, and application of black phosphorus.

The metal-rich phosphide TaCrP forms from the elements by step-wise solid state reaction in an alumina crucible (maximum annealing temperature 1180 K). TaCrP is trimorphic. The structural data of the hexagonal ZrNiAl high-temperature phase (space group P 6 ‾ 2 m $P\overline{6}2m$ ) was deduced from a Rietveld refinement. At room temperature TaCrP crystallizes with the TiNiSi type (Pnma, a = 623.86(5), b = 349.12(3), c = 736.78(6) pm, wR = 0.0419, 401 F 2 values, 20 variables) and shows a Peierls type transition below ca. 280 K to the monoclinic low-temperature modification (P121/c1, a = 630.09(3), b = 740.3(4), c = 928.94(4) pm, β = 132.589(5)°, wR = 0.0580, 1378 F 2 values, 57 variables). The latter phase transition is driven by pairwise Cr–Cr bond formation out of an equidistant chain in o-TaCrP. The phase transition was monitored via different analytical tools: differential scanning calorimetry, powder synchrotron X-ray diffraction, magnetic susceptibility measurements and 31P solid state NMR spectroscopy.

In this study, we investigated the effect of nanostructured Al2O3 particles on Li ion conducting, poly(ethylene oxide) (PEO)-based membranes prepared by electrospinning, solution casting and hot pressing. Pure PEO:LiBF4 solid polymer electrolytes (SPEs) and also plasticizer containing membranes were investigated with various amounts of Al2O3. In a first step, the best-performing composition of pure PEO:LiBF4 concerning the resulting ionic conductivity was identified and used as a standard for further experiments. In the following, the influence of the preparation method, the nature of the Al2O3, and the type of the plasticizer additives on the thermal and electrochemical properties for this standard composition were investigated. The Al2O3 composition was varied between 1 and 5 wt%. The ionic conductivity of bare electrospun PEO:LiBF4 SPE standard material has been improved by a factor ten to 1.9 × 10−6 S cm−1 at T = 293 K when 5 wt% of Al2O3 is added. For solution-casted PEO:LiBF4 standard compositions 18:1 with an initial ionic conductivity of 6.7 × 10−8 S cm−1, the addition of 2 wt% Al2O3 increased the performance to 1.4 × 10−7 S cm−1, both at T = 293 K. If succinonitrile and Al2O3 was admixed to the solution casted standard material, the ionic conductivity was further increased to reach 5.5 × 10−5 S cm−1 at T = 293 K. This material with a composition of 18:3:1 + 2 wt% Al2O3, outperforms the standard material by three orders of magnitude.

One-dimensional semiconductors are interesting materials due to their unique structural features and anisotropy, which grant them intriguing optical, dielectric and mechanical properties. In this work, we report on SnBrP, a lighter homologue of the first inorganic double helix compound SnIP. This class of compounds is characterized by intriguing mechanical and electronic properties, featuring a high flexibility without modulation of physical properties. Semiconducting SnBrP can be synthesized from red phosphorus, tin and tin(II)bromide at elevated temperatures and crystallizes as red-orange, cleavable needles. Raman measurements pointed towards a double helical building unit in SnBrP, showing similarities to the SnIP structure. After taking PL measurements, HR-TEM, and quantum chemical calculations into account, we were able to propose a sense full structure model for SnBrP.

Red phosphorus offers a high theoretical sodium capacity and has been considered as a candidate anode for sodium-ion batteries. Similar to silicon anodes for lithium-ion batteries, the electrochemical performance of red phosphorus is plagued by the large volume variation upon sodiation. Here we perform in situ transmission electron microscopy analysis of the synthesized red-phosphorus-impregnated carbon nanofibers with the corresponding chemo-mechanical simulation, revealing that, the sodiated red phosphorus becomes softened with a “liquid-like” mechanical behaviour and gains superior malleability and deformability against pulverization. The encapsulation strategy of the synthesized red-phosphorus-impregnated carbon nanofibers has been proven to be an effective method to minimize the side reactions of red phosphorus in sodium-ion batteries, demonstrating stable electrochemical cycling. Our study provides a valid guide towards high-performance red-phosphorus-based anodes for sodium-ion batteries., Red phosphorus is a promising anode for Na-ion batteries but suffers from large volume change upon cycling. Here the authors show a red-phosphorus-impregnated carbon nanofiber design in which the sodiated red phosphorus is featured by a “liquid-like” behavior and ultra-stable electrochemical performance is realized.

Magnesium Ion based Solid State Batteries (MIBs) are subject of intensive studies due to abundance of magnesium, its advantages in volumetric capacity, and the reduced dendrite growth. Here we report on a true solid polymer electrolyte system without liquid additives or plasticizers that reaches conductivities above 10−5 S cm−1 at room temperature and above 10−4 S cm−1 at 50 °C. An electrospun polymer electrolyte membrane fabricated from a polymer electrolyte featuring a composition of PEO : Mg(TFSI)2 36 : 1 [where PEO stands for poly(ethyleneoxide) and Mg(TFSI)2 for magnesium bis(trifluoromethanesulfonyl) imide] was identified as the best performing system. Magnesium transport was substantiated by different methods, and the electrochemical properties including solid electrolyte interface (SEI) formation were investigated. Electrospinning as a preparation method has been identified as a powerful tool to enhance the electrochemical properties beyond conventional polymer membrane fabrication techniques.

Coinage metal polychalcogenide halides are an intriguing class of materials, and many representatives are solid ion conductors and thermoelectric materials. The materials show high ion mobility, polymorphism, and various attractive interactions in the cation and anion substructures. Especially the latter feature leads to complex electronic structures and the occurrence of charge-density waves (CDWs) and, as a result, the first p-n-p switching materials. During our systematic investigations for new p-n-n switching materials in the Cu-Te-Cl phase diagram, we were able to isolate polymorphic Cu

A diode requires the combination of p- and n-type semiconductors or at least the defined formation of such areas within a given compound. This is a prerequisite for any IT application, energy conversion technology, and electronic semiconductor devices. Since the discovery of the pnp-switchable compound Ag

The rare-earth germanium sulfide iodides RE3Ge2S8I (RE = La, Ce, Pr) have been prepared by reaction of the elements at 900 °C. They adopt the monoclinic La3(SiO4)2Cl-type structure (space group C2/c, Z = 4; a = 16.156(4)–15.9760(9) A, b = 7.9776(18)–7.8786(5) A, c = 11.081(3)–10.9281(6) A, β = 98.192(5)–98.4525(10)° on progressing from La to Pr for the RE component) consisting of isolated thiogermanate tetrahedral groups [GeS4]4– separated by RE3+ and I− ions. The optical band gaps fall in the range of 2.7–3.1 eV. Magnetic measurements indicated simple paramagnetic behaviour for Ce3Ge2S8I and Pr3Ge2S8I.

Recent evidence of exponential environmental degradation will demand a drastic shift in research and development toward exploiting alternative energy resources such as solar energy. Here, we report...

Cu9.1Te4Cl3 is a new polymorphic compound in the class of coinage metal polytelluride halides. Copper is highly mobile, which results in multiple order-disorder phase transitions in a limited temperature interval from 240 to 370 K. Mainly as a consequence of thermal transport properties, the compound's thermoelectric figure of merit reaches values up to ZT = 0.15 in the temperature range between room temperature and 523 K. Its structure is closely related to that of Ag10Te4Br3, another coinage metal polytelluride halide, which represents the first p-n-p-switchable semiconductor approachable by a simple temperature change. The title compound outperforms Ag10Te4Br3 in terms of thermoelectric properties by 1 order of magnitude and therefore acts as a link between the class of p-n-p compounds and thermoelectric materials.

Copper is a common current collector at the anode side in rechargeable batteries. The reactivity of copper is often neglected in battery applications which becomes a problem if the active material is highly reactive as well. Corrosion and compound formation results. Here, we report on the influence of the synthesis method and the role of copper on the electrochemical performance of black phosphorus anodes for sodium ion batteries. Two top-down and one bottom-up approaches were applied to prepare different samples. An easy dip coating process was developed to apply copper prior to usage significantly increasing the capacity of the system.

We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.

Inorganic semiconductor nanowires and quantum dots made of chalcogenides, III-V semiconductors and halide perovskites offer exciting potential for optoelectronic devices. The orthogonalization possible in nanowires between the normally competing processes of charge generation and charge separation have been used to project very high operating performance exceeding that of thin films and single crystals in light harvesting devices such as solar cells, photodetectors, photocatalysts and photoelectrolyzers. Likewise, inorganic quantum dots with size-tunable absorption and emission spectra are excellent candidates for light emitting devices as well as light harvesting devices. However, the practical performance of inorganic nanowire based optoelectronic devices has significantly lagged theoretical predictions. A major reason for the discrepancy between theory and experiment is the presence of surface traps and defects in nanowires and quantum dots, which exhibit a large surface area to volume ratio. Several chemical treatments and annealing regimens have been employed to heal surface defects in nanowires and quantum dots. One popular strategy involves wrapping nanowires and/or quantum dots with a thin coating of a molecular monolayer (e.g. alkanethiols) or an atomic layer deposited conformal oxide. While such core-shell architectures are frequently effective in reducing surface defects, the surface passivation is invariably accompanied by a deterioration in optoelectronic properties due to the difficulty experienced by charge carriers in tunneling through the thin shell layer. The resulting trade-off between surface passivation and carrier extraction limits performance improvements in light harvesting devices. Thus there is a strong need for passivating layers that do not negatively impact carrier extraction. Herein, we show that graphitic carbon nitride coatings are highly effective in passivating the surfaces of inorganic nanowires and quantum dots while preserving excellent carrier transport and extraction. Three illustrative examples are provided together with in-depth spectroscopic and electrical characterization: (1) Cesium lead bromide (CsPbBr3) quantum dots passivated by g-C3N4 nanosheets and performing spectacularly as CO2 photoreduction catalysts and water-splitting photoanodes (2) The double helical ternary semiconductor SnIP passivated by g-C3N4 nanosheets which experienced a remarkable improvement in photoelectrochemical performance (3) Cadmium sulfide (CdS) nanowires passivated by C3N5 nanosheets resulting in a superior photocatalytic performance

Moiré superlattices of van der Waals heterostructures provide a powerful way to engineer electronic structures of two-dimensional materials. Many novel quantum phenomena have emerged in graphene and transition metal dichalcogenide moiré systems. Twisted phosphorene offers another attractive system to explore moiré physics because phosphorene features an anisotropic rectangular lattice, different from isotropic hexagonal lattices previously reported. Here we report emerging anisotropic moiré optical transitions in twisted monolayer/bilayer phosphorenes. The optical resonances in phosphorene moiré superlattice depend sensitively on twist angle and are completely different from those in the constitute monolayer and bilayer phosphorene even for a twist angle as large as 19°. Our calculations reveal that the Γ-point direct bandgap and the rectangular lattice of phosphorene give rise to the remarkably strong moiré physics in large-twist-angle phosphorene heterostructures. This work highlights fresh opportunities to explore moiré physics in phosphorene and other van der Waals heterostructures with different lattice configurations., Twisted phosphorene offers another attractive system to explore moiré physics. Here, the authors report emerging anisotropic moiré optical resonances in twisted monolayer/bilayer phosphorene, exhibiting strong twist dependence for angles as large as 19°.

Tin iodide phosphide (SnIP), an inorganic double-helix material, is a quasi-1D van der Waals semiconductor that shows promise in photocatalysis and flexible electronics. However, the understanding of the fundamental photophysics and charge transport dynamics of this new material is limited. Here, time-resolved terahertz (THz) spectroscopy is used to probe the transient photoconductivity of SnIP nanowire films and measure the carrier mobility. With insight into the highly anisotropic electronic structure from quantum chemical calculations, an electron mobility as high as 280 cm2 V-1 s-1 along the double-helix axis and a hole mobility of 238 cm2 V-1 s-1 perpendicular to the double-helix axis are detected. Additionally, infrared-active (IR-active) THz vibrational modes are measured, which shows excellent agreement with first-principles calculations, and an ultrafast photoexcitation-induced charge redistribution is observed that reduces the amplitude of a twisting mode of the outer SnI helix on picosecond timescales. Finally, it is shown that the carrier lifetime and mobility are limited by a trap density greater than 1018 cm-3 . The results provide insight into the optical excitation and relaxation pathways of SnIP and demonstrate a remarkably high carrier mobility for such a soft and flexible material, suggesting that it could be ideally suited for flexible electronics applications.

Phosphorene—the monolayered material of the element allotrope black phosphorus (Pblack)—and SnIP are 2D and 1D semiconductors with intriguing physical properties. Pblack and SnIP have in common that they can be synthesized via short way transport or mineralization using tin, tin(IV) iodide and amorphous red phosphorus. This top‐down approach is the most important access route to phosphorene. The two preparation routes are closely connected and differ mainly in reaction temperature and molar ratios of starting materials. Many speculative intermediates or activator side phases have been postulated especially for top‐down Pblack/phosphorene synthesis, such as Hittorf's phosphorus or Sn24P19.3I8 clathrate. The importance of phosphorus‐based 2D and 1D materials for energy conversion, storage, and catalysis inspired us to elucidate the formation mechanisms of these two compounds. Herein, we report on the reaction mechanisms of Pblack/phosphorene and SnIP from P4 and SnI2 via direct gas phase formation., 1D‐SnIP and 2D‐phosphorene are formed in a gas phase reaction of gaseous white phosphorus (P4) and SnI2 via P4 activation followed by successive helix or layer growth. P4 activation takes place by Sn2I4 dimers attracting the P lone pairs (SnIP) or direct SnI2 insertion in a P−P bond (phosphorene). Both reaction mechanisms were studied between 0 K and synthesis temperature.

Tin iodide phosphorus (SnIP) is an interesting new semiconductor that is the world's first non-templated inorganic double helix. Here we report on the first ultrafast study of SnIP, where we use THz spectroscopy to measure the carrier mobility and probe the relaxation dynamics. Additionally, we observe a vibrational mode at 1.49 THz and show how carrier screening reduces the oscillator amplitude, which manifests as a reduction in differential signal with Lorentzian lineshape.

SnIP, an atomic-scale inorganic double helix compound is composed of a hexagonal rod packing of double helices in the bulk phase. A racemic mixture of P- and M-SnIP double helices is energetically most favored and present in the solid. In order to evaluate if enantiomer-pure SnIP might be able to realize three different stacking models of seven chiral double helices, an enantiomer-pure, a 2:1, and a racemic 1:1 ratio were investigated according to their energies of formation. While a top-down approach did not lead to single isolated double helices, the development of a bottom-up approach might be beneficial. Motivated by templating strategies in confined geometries we performed first principles density functional theory (DFT) calculations using carbon nanotubes (CNTs) featuring different electronic properties and suitable sizes as matrices to accommodate chiral SnIP double helices. With the aid of DFT, we determined the ideal diameter, stability, and electronic properties of different SnIP@CNT systems. Appropriate molecular starting materials and a feasible formation mechanism are identified based on chemical considerations. An interaction between the CNTs and the SnIP units is evident, causing structure and property modifications of the hybrids. The intercalation of SnIP into a suitable CNT leads to a gain in total energy compared to the isolated systems. Based on our findings, a straightforward way to introduce chirality in suitable CNTs via SnIP@CNT hybrids is feasible.

This review summarizes the development, investigation, and optimization of polymorphic lithium cobalt phosphate LiCoPO4. One of the three polymorphs known to date, olivine-type or Pnma-LiCoPO4, shows intriguing electrochemical properties as a high-voltage cathode material, which are of interest for next-generation lithium-ion batteries with higher energy density. Hence, scientists have developed optimization strategies to improve its performance for commercial applications. Herein, a number of procedures for the synthesis of Pnma-LiCoPO4 is presented, including thermodynamic as well as kinetically controlled approaches. The continuous improvement of its electrochemical performance is illustrated, which was realized by the development of solvothermal techniques that allow a precise particle size and morphology control. In the course of these investigations, two new polymorphs, Pna21-LiCoPO4 and Cmcm-LiCoPO4, have been discovered which show different physical and structural properties compared to Pnma-LiCoPO4. Despite their significantly poorer electrochemical performance, these polymorphs allow interesting insights into the variable structure chemistry of transition-metal phosphates, which canalizes in intriguing magnetic and thermal properties. The similarities and differences in the chemical and physical properties of Pnma-LiCoPO4, Pna21-LiCoPO4, and Cmcm-LiCoPO4 are discussed.

Layered black phosphorus (BP) has attracted wide attention for mid-infrared photonics and high-speed electronics, due to its moderate band gap and high carrier mobility. However, its intrinsic band gap of around 0.33 electronvolt limits the operational wavelength range of BP photonic devices based on direct interband transitions to around 3.7 μm. In this work, we demonstrate that black arsenic phosphorus alloy (b-AsxP1–x) formed by introducing arsenic into BP can significantly extend the operational wavelength range of photonic devices. The as-fabricated b-As0.83P0.17 photodetector sandwiched within hexagonal boron nitride (hBN) shows peak extrinsic responsivity of 190, 16, and 1.2 mA/W at 3.4, 5.0, and 7.7 μm at room temperature, respectively. Moreover, the intrinsic photoconductive effect dominates the photocurrent generation mechanism due to the preservation of pristine properties of b-As0.83P0.17 by complete hBN encapsulation, and these b-As0.83P0.17 photodetectors exhibit negligible transport hystere...

Electrospinning is used to fabricate sodium ion conducting fiber membranes composed of polyethylene oxide (PEO), sodium tetrafluoroborate (NaBF4), and succinonitrile (SN) as plasticizer. As compared to conventionally prepared lithium electrolyte membranes with identical composition (PEO:SN:LiBF4), those membranes exhibit conductivities up to 10−4 S cm−1 at 328 K (activation energy ∼36 kJ mol−1, 36:8:1 membrane), which favors such systems as a solid-state electrolyte alternative for batteries. The conduction mechanism is evaluated and the ion mobility are examined. We identified the segment mobility of the polyethylene oxide as the main driving force for the enhanced ion mobility in the membranes. The introduction of SN has only a minor influence on the conductivity and segment mobility at room temperature, but extents the anion and cation mobility to temperatures below ambient. For the 36:8:1 (PEO:SN:NaBF4) membrane we found the highest ion mobility of all membranes under investigation. A comparison of the present sodium membranes with lithium systems of the same composition shows that the overall performance of the sodium systems is comparable. Taking plasticizer-free sodium membranes into account they perform even better than the lithium containing counterparts, and plasticizer-modified membranes show only half an order of magnitude lower conductivities than comparable lithium ones.

Semiconducting silver tellurides gained reasonable interest in the past years due to its thermoelectric, magneto-caloric, and nonlinear optic properties. Nanostructuring has been frequently used to address quantum-confinement effects of minerals and synthetic compounds in the Ag–Te system. Here, we report on the structural, thermal, and thermoelectric properties of stuetzite-like Ag1.54Te (or Ag4.63Te3) and Ag1.9Te. By a quasi-topotactic reaction upon tellurium evaporation Ag1.54Te can be transferred to Ag1.9Te after heat treatment. Crystal structures, thermal and thermoelectric properties of stuetzite-like Ag1.54Te (or Ag4.63Te3) and Ag1.9Te were determined by ex situ and in situ experiments. This method represents an elegant chemical way to Ag1.9Te, which was so far only accessible electrochemically via electrochemical removal of silver from the mineral hessite (Ag2Te). The mixed conductors show reasonable high total electric conductivities, very low thermal conductivities, and large Seebeck coefficient...

Herein we report on the optimized synthesis process of SnIP, the first inorganic double helix compound which shows high mechanical flexibility, a strong tendency for cleavage or delamination and intriguing electronic properties. In this work we analyzed the influence of SnI 2 as a reaction promotor or mineralizer compound for the synthesis of SnIP. In previous studies Sn/SnI 4 was used as a precursor and chemical transport agent for the SnIP synthesis but significant amounts of non-reacted tin halide (SnI 2 and SnI 4 ) remained after the formation of the target compound reducing its quality and yield. Significantly less tin halide residue can be observed which suggests a reduction of side-reactions. While the Sn/SnI 4 couple works perfectly for the synthesis of the two-dimensional material phosphorene precursor black phosphorus the Sn/SnI 2 couple is beneficial for the one-dimensional ternary polyphosphide SnIP. These results strongly encourage the theory of SnI 2 as the important reaction intermediate in the synthesis of covalently-bonded polyphosphide substructures and element allotropes at elevated temperatures.

Structural, electronic, and vibrational spectroscopic investigations were performed for the solid solution NaP7–xAsx up to x = 3.5 featuring a helical polypnictide substructure. Depending on the As content the LiP7 (for x = 0 to 0.8 and 2.5 to 3.5) or KP15 (x = 1.0 to 2.4) structure type is realized up to an maximum As content of x = 3.5. The crystal structures of two selected phases were determined and the distribution of As in the polyanionic substructure was determined. The full solid solution up to x = 7 was subject to a quantum chemical DFT analysis in order to get insights into the stabilities and phase formation tendencies. Van der Waals interactions between the structure subunits were estimated and first principle investigations towards a delamination and nano structuring of NaP7–xAsx crystals into one-dimensional semiconductors were performed.

A new metastable phase, featuring a lithium-stabilized mixed-valence cobalt(II,III) hydroxide phosphate framework, Co11.0(1)Li1.0(2)[(OH)5O][(PO3OH)(PO4)5], corresponding to the simplified composition Co1.84(2)Li0.16(3)(OH)PO4, is prepared by hydrothermal synthesis. Because the pH-dependent formation of other phases such as Co3(OH)2(PO3OH)2 and olivine-type LiCoPO4 competes in the process, a pH value of 5.0 is crucial for obtaining a single-phase material. The crystals with dimensions of 15 μm × 30 μm exhibit a unique elongated triangular pyramid morphology with a lamellar fine structure. Powder X-ray diffraction experiments reveal that the phase is isostructural with the natural phosphate minerals holtedahlite and satterlyite, and crystallizes in the trigonal space group P31m (a = 11.2533(4) A, c = 4.9940(2) A, V = 547.70(3) A3, Z = 1). The three-dimensional network structure is characterized by partially Li-substituted, octahedral [M2O8(OH)] (M = Co, Li) dimer units which form double chains that run alo...

Two-dimensional (2D) nanoflakes have emerged as a class of materials that may impact electronic technologies in the near future. A challenging but rewarding work is to experimentally identify 2D materials and explore their properties. Here, we report the synthesis of a layered material, P20.56(1)Sb0.44(1), with a systematic study on characterizations and device applications. This material demonstrates a direct band gap of around 1.67 eV. Using a laser-cutting method, the thin flakes of this material can be separated into multiple segments. We have also fabricated field effect transistors based on few-layer P20.56(1)Sb0.44(1) flakes with a thickness down to a few nanometers. Interestingly, these field effect transistors show strong photoresponse within the wavelength range of visible light. At room temperature, we have achieved good mobility values (up to 58.96 cm2/V·s), a reasonably high on/off current ratio (∼103), and intrinsic responsivity up to 10 μA/W. Our results demonstrate the potential of P20.56(...

The majority of research activities on LiCoPO 4 are focused on the phospho-olivine (space group Pnma ), which is a promising high-voltage cathode material for Li-ion batteries. In contrast, comparably little is known about its metastable Pna 2 1 modification. Herein, we present a comprehensive study on the structure–property relationships of 15–20 nm Pna 2 1 -LiCoPO 4 nanospheres prepared by a simple microwave-assisted solvothermal process. Unlike previous reports, the results indicate that the compound is non-stoichiometric and shows cation-mixing with Co ions on the Li sites, which provides an explanation for the poor electrochemical performance. Co L 2,3 -edge X-ray absorption spectroscopic data confirm the local tetrahedral symmetry of Co 2+ . Comprehensive studies on the thermal stability using thermogravimetric analysis, differential scanning calorimetry, and in situ powder X-ray diffraction show an exothermic phase transition to olivine Pnma -LiCoPO 4 at 527 °C. The influence of the atmosphere and the particle size on the thermal stability is also investigated.

Durch Reaktionen zwischen Festkorper und Gasphase lassen sich Phosphorverbindungen kinetisch kontrolliert herstellen. Deren Strukturen reichen von molekular uber Schichten bis zu Spiralen. Daraus resultieren interessante physikalische Eigenschaften: Sie sind Supraleiter oder lassen sich um 180 ° biegen.

High-performance particles of the high-voltage cathode material LiCoPO 4 for Li-ion batteries are synthesized by a simple and rapid one-step microwave-assisted solvothermal route at moderate temperatures (250 °C). Using a variety of water/alcohol 1:1 (v:v) solvent mixtures, including ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol (TTEG), polyethylene glycol 400 (PEG), and benzyl alcohol (BA), the focus of the study is set on optimizing the electrochemical performance of the material by controlling the particle size and morphology. Scanning electron microscopy studies reveal a strong influence of the co-solvent on the particle size and morphology, resulting in the formation of variations between square, rhombic and hexagonal platelets. According to selected area electron diffraction experiments, the smallest crystal dimension is in the [010] direction for all materials, which is along the lithium diffusion pathways of the olivine crystal structure. The anisotropic crystal orientations with enhanced Li-ion diffusion properties result in high initial discharge capacities and gravimetric energy densities (up to 141 mAh g −1 at 0.1 C and 677 Wh kg −1 for LiCoPO 4 obtained from TEG), excellent rate capabilities, and cycle life for 20 cycles.

Few-layer black phosphorus or phosphorene is an intriguing and important 2D material. It is a single-layer material that consists of corrugated and condensed six-membered phosphorus rings (Fig. 1). Each phosphorene layer can be weakly bonded to neighboring ones by van der Waals-like interactions to form few-layer arrangements, which are also called phosphorene in many publications. Finally, attaching many phosphorene layers to each other ends up as orthorhombic black phosphorus, a long-known phosphorus allotrope. There are two different few-layer 2D materials of phosphorus known to date, which can be derived from the element structures of orthorhombic black phosphorus (1) or gray arsenic (2). The latter is discussed as blue phosphorus in the literature (3). Since 2014, when few-layer black phosphorus was first prepared by a top-down approach from black phosphorus and used as field effect transistors (4⇓–6), a continuously increasing interest can be observed for this 2D material. Recently, an elegant, well-defined, and controllable bottom-up route for partially oxidized phosphorene ( po- phosphorene) was reported (7). In a one-pot and also low-cost process, molecular highly reactive white phosphorus acts as starting material and ethylene diamine serves as a solvent and reaction promotor (4). In a low-temperature reaction at 100 °C, po- phosphorene can be achieved on a gram scale. Due to traces of oxygen present in the solvent or during the synthesis process, the target material is partially oxidized on the surface. This aspect may look like a disadvantage at first glance, but it has turned out to be beneficial for the long-term air and moisture stability of the final product. The report in PNAS by Tian et al. (7) on the first bottom-up synthesis of well-defined po -phosphorene is a major breakthrough in synthetic chemistry. It paves the way for the large-scale … [↵][1]1Email: tom.nilges{at}lrz.tum.de. [1]: #xref-corresp-1-1