The crystal structure, thermal behaviour and ionic conductivity of a novel lithium gadolinium polyphosphate LiGd(PO3)4

Crystal structure and ionic conductivity of lithium gadolinium polyphosphate, LiGd(PO₃)₄, were investigated. Single crystals of the title compound have been grown by a flux technique. The structure of this novel phosphate was determined by single crystal X-ray diffraction techniques. LiGd(PO₃)₄ is isotypic with LiNd(PO₃)₄. It crystallizes in the monoclinic space group C2/c with the unit cell parameters a=16.386(2), b=7.059(3), c=9.677(2) Å, β=126.12(1)°, V=904.2(4) Å³ and Z=4. The structure refined from 967 independent reflections leads to R₁=0.0167 and wR₂=0.0458. The lattice of LiGd(PO₃)₄ is built of twisted zig-zag chains running along with the b direction and make up of PO₄ tetrahedra sharing two corners, connected to the GdO₈ and LiO₄ polyhedra by common oxygen atoms to form a three-dimensional framework. Differential and thermogravimetric thermal analysis are given. The thermal curve of this compound was recorded and interpreted in agreement with impedance measurements. The ionic conductivity has been measured on pellet of the polycrystalline powder and evaluated as a function of temperature. This phase showed the conductivity of 2×10⁻⁶ and 2×10⁻⁴ Ω⁻¹ cm⁻¹ at 682 and 951 K, respectively.     

Highly porous LiMnPO4 in combination with an ionic liquid-based polymer gel electrolyte for lithium batteries

A porous well defined LiMnPO₄ cathode material is synthesized by a sol-gel method. The electrochemical performance of the cathode material is evaluated in a cell with an ionic liquid-based polymer electrolyte (0.5 M LITFSI in EMImTFSI) and a lithium metal electrode. The results are compared to a cell with a traditional organic carbonate-based electrolyte (1 M LiPF₆ in EC/DMC). The cell with the ionic liquid-based polymer electrolyte presents an enhanced electrochemical intercalation performance of lithium ions, a high electrochemical stability window of 5 V, and an excellent cycling ability as compared with the organic based counterpart. Furthermore, the ionic liquid-based polymer gel electrolyte effectively prevents the dissolution of manganese — otherwise a common problem.     

Crystal structure, conductivity and reversible water uptake of new layered potassium antimonates KxL(1+x)/3Sb(2−x)/3O2 (L=Ni, Mg, Co)

Novel mixed potassium antimonates K_0.59Mg_0.53Sb_0.47O₂, K_0.5Ni_0.5Sb_0.5O₂, K_0.5Co_0.5Sb_0.5O₂ (rhombohedral P3-type structure), K_0.56Ni_0.52Sb_0.48O₂ and K_0.86Co_0.62Sb_0.38O₂ (hexagonal P2 type) have layered structures based on brucite-like (L,Sb)O_6/3 sheets of edge-shared octahedra and interlayer K⁺ cations in trigonal prismatic coordination. The preference to form P2 and P3 structures rather than closely related O3 type is dictated by the large radius of K⁺ and the value of unit cell parameter a, restricted by average size of the cations randomly distributed in the octahedral sites within (L,Sb)O_6/3 layer. The new phases reversibly absorb atmospheric moisture leading to the formation of hydrates with ca. 11% larger interlayer distances. The impedance spectroscopy of P2-type K_0.56Ni_0.52Sb_0.48O₂ and P3-type K_0.59Mg_0.53Sb_0.47O₂ ceramics shows relatively high ionic conductivity, presumably due to potassium cationic transport, with activation energies of 35±2 and 33±1 kJ/mol, respectively. At 573 K, the conductivity values are 0.016 S/cm for K_0.56Ni_0.52Sb_0.48O₂ and 0.021 S/cm for K_0.59Mg_0.53Sb_0.47O₂. Interaction with water vapor leads to increasing total conductivity.     

Ionic conductivity, structural and thermal properties of pure and Sr doped Y2Ti2O7 pyrochlores for SOFC

In the present study, SrO doped Yttrium titanate pyrochlore was synthesized using solid state reaction technique. The sintering characteristics, crystal structure, thermal and conductivity behavior of doped and undoped pyrochlores have been studied to find their suitability in solid oxide fuel cells (SOFC). The as-prepared samples were characterized using X-ray diffraction (XRD), Fourier-Transform-Infrared spectroscopy (FT-IR), thermal-gravimetric analysis (TGA) and ac conductivity up to 900 °C. The results are discussed in light of oxygen vacancy formation and structural disordering. Undoped and doped yttrium titanate with SrO (x = 0.1) exhibits single Y₂Ti₂O₇ phase with relative density of 94%. It was observed that further doping of SrO (x = 0.2–0.4) leads to formation of Y₂Ti₂O₇ phase along with SrTiO₃ phase. Excessive SrO (x = 0.4) results in increase in ionic conductivity to 1.50 × 10⁻¹ S cm⁻¹ whereas it impedes the densification process with relative density of 85%.     

Current-sensing atomic force microscopy for analyzing conformations and properties of polymer membranes for fuel cells

The three-dimensional structures of polymer membranes are different at surfaces and inside bulks, and thus, in general, physical/chemical properties are also different. Morphologies and properties of membrane surfaces are now visualized by current-sensing atomic force microscopy. The increase in performances of a single cell is discussed based on the three-dimensional structures of the polymer membrane, anion-exchange membrane as an example, used for fuel cells. Other reports on Nafion®, proton-exchange membrane, are also introduced to show the importance of this microscopic method.     

Ionic transport studies on (PEO)6:NaPO3 polymer electrolyte plasticized with PEG400

Conduction characteristics of the poly(ethylene oxide) based new polymer electrolyte (PEO)₆:NaPO₃, plasticized with poly(ethylene glycol) are investigated. Free standing flexible electrolyte films of composition (PEO)₆:NaPO₃ + x wt.% PEG₄₀₀ (30 ? x ? 70) are prepared by solution casting method. A combination of X-ray diffraction (XRD), optical microscopy and differential scanning calorimetry (DSC) studies have indicated enhancement in the amorphous phase of polymer due to the addition of plasticizer. Further, a reduction in the glass transition temperature observed from the DSC result has inferred increase in the flexibility of the polymer chains. The cationic transport number (t_Na⁺) of 0.42 determined through combined ac-dc technique has confirmed ionic nature of conducting species. Ionic conductivity studies are carried out as a function of composition and temperature using complex impedance spectroscopy. The electrolyte with maximum PEG₄₀₀ content has exhibited an enhancement in the conductivity of about two orders of magnitude compared to the host polymer electrolyte. The complex impedance data is analyzed in conductivity, permittivity and electric modulus formalism in order to throw light on transport mechanism. A solid state electrochemical cell based on the above polymer electrolyte with a configuration Na|SPE|(I₂ + acetylene black + PEO) has exhibited an open circuit voltage of 2.94 V. The discharge characteristics are found to be satisfactory as a laboratory cell.     

A novel gel polymer electrolyte based on poly ionic liquid 1-ethyl 3-(2-methacryloyloxy ethyl) imidazolium iodide

Poly ionic liquid 1-ethyl 3-(2-methacryloyloxy ethyl) imidazolium iodide (PEMEImI) as a single-ion conductor was designed and synthesized. When appropriate amount of suitable plasticizers, I₂ and polyacrylonitrile (PAN) were incorporated into it, the complex formed gel polymer electrolyte. Chemical structure, thermal behavior and ionic conductive properties of the gel polymer electrolyte were investigated by Raman spectra, UV-Vis spectra, differential scanning calorimetry (DSC), and complex impedance analysis, respectively. For the new gel polymer electrolyte, the ionic conductivity of about 1 × 10⁻³ S cm⁻¹ at room temperature was achieved.     

Effects of the porous structure on conductivity of nanocomposite polymer electrolyte for lithium ion batteries

A kind of porous nanocomposite polymer membranes (NCPMs) based on poly(vinylidene difluoride-co-hexafluoropropylene) (P(VdF-HFP)) incorporated with different amounts of TiO₂ nanoparticles from in situ hydrolysis of Ti(OC₄H₉)₄ was prepared by a non-solvent induced phase separation (NIPS) technology. The SEM micrographs reveal that a porous structure exists in the NCPMs, which changes with the incorporated amount of TiO₂. The NCPMs incorporated with 9.0 wt.% of mass fraction of TiO₂ possess the highest porosity, 67.3%, and appear as flexile fracture with an elongation ratio, 74.4%. At this content, the ionic conductivity of the NCPE is up to 0.94 × 10⁻³ S cm⁻¹ at room temperature and the activation energy for ions transport reaches the lowest, 18.71 kJ mol⁻¹. It is of great potential application in lithium ion batteries.     

抑制Q235钢CO2腐蚀的气液双相咪唑啉衍生物缓蚀剂的缓蚀行为

采用失重法、交流阻抗(EIS)及傅里叶变换红外光谱(FT-IR)、原子力显微镜(AFM)、X射线光电子能谱(XPS)等表面分析测试方法首次研究了硫脲基咪唑啉衍生物(TAI)作为抑制CO₂腐蚀的气液双相缓蚀剂的缓蚀行为. 结果表明, 该硫脲基咪唑啉缓蚀剂能有效地抑制Q235 钢在气液双相中的CO₂腐蚀. AFM测试结果表明该缓蚀剂能显著地降低碳钢表面的腐蚀破坏, 并且由于碳钢表面形成的缓蚀剂吸附膜的疏水作用,可在AFM探头和碳钢表面之间检测到更大的粘附力, 而探针与试样表面之间的长程静电斥力在气相中增加,在液相中由于表面电荷的屏蔽效应而减小. XPS和FT-IR 光谱测试表明液相中和气相中在碳钢表面形成吸附膜的缓蚀剂成分分别是硫脲基咪唑啉衍生物和其酸水解产物——酰胺. 以上结果也进一步证实了咪唑啉衍生物在酸性溶液中的水解机理.     

Preparation and characterization of gel polymer electrolyte based on electrospun polyhedral oligomeric silsesquioxane-poly(methyl methacrylate)8/polyvinylidene fluoride hybrid nanofiber membranes for lithium-ion batteries

Journal of Solid State Electrochemistry - As a kind of organic–inorganic hybrid materials with nanocage structure, polyhedral oligomeric silsesquioxane (POSS) has the advantages of good...     

Investigation on the folding mode of a polymer chain in a spiral crystal by single molecule force spectroscopy

Investigation on the folding mode of a single polymer chain in its crystal is significant to the understanding of the mechanism of the fundamental crystallization as well as the engineering of new polymer crystal-based materials. Herein, we use the combined techniques of atomic force microscopy （AFM） imaging and force spectroscopy to pull a single polyethylene oxide （PEO） chain out of its spiral crystal in amyl acetate. From these data, the folding mode of polymer chains in the spiral crystal has been reconstructed. We find that the stems tilt in the typical flat area, leading to the decrease in the apparent lamellar height. While in the area of screw dislocation, the lamellar height gradually increases in the range of several nanometers. These results indicate that the combined techniques present a novel tool to directly unravel the chain folding mode of spiral crystals at single-molecule level.     

Ionic transport in P(VDF-HFP)-PMMA-LiCF3SO3-(PC + DEC)-SiO2 composite gel polymer electrolyte

Composite gel polymer electrolytes composed of poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) and polymethylmethacrylate PMMA polymers, PC + DEC as plasticizer and LiCF₃SO₃ as salt and fumed silica as filler have been synthesized by solvent casting technique with varying plasticizer-filler ratio systematically. Films of thickness in the range of 40-70 μm were characterized by a.c. impedance measurements in the temperature range 303 K to 373 K. Addition of filler to the polymer electrolyte was found to result in an enhancement of the ionic conductivity. A maximum electrical conductivity of ∼1 × 10⁻³ S/cm at 303 K and ∼2.1 × 10⁻³ S/cm at 373 K has been achieved with the dispersion of the SiO₂. FTIR spectral studies confirmed the polymer-salt interaction. XRD patterns exhibit the increased amorphicity in the blended composite gel polymer electrolytes. Scanning electron micrograph shows the dispersion of SiO₂ particle in the polymer electrolyte.     

New polymer electrolyte membrane for medium-temperature fuel cell applications based on cross-linked polyimide Matrimid and hydrophobic protic ionic liquid

New hydrophobic protic ionic liquid, 2-butylaminoimidazolinium bis(trifluoromethylsulfonyl)imide (BAIM-TFSI), has been synthesized. The ionic liquid showed good thermal stability to at least 350 °C. The conductivity of BAIM-TFSI determined by electrochemical impedance method was found to be 5.6 × 10^?2 S/cm at 140 °C. Homogeneous composite films based on commercial polyimide (PI) Matrimid and BAIM-TFSI containing 30–60 wt% of ionic liquid were prepared by casting from methylene chloride solutions. Thermogravimetric analysis data indicated an excellent thermal stability of PI/BAIM-TFSI composites and thermal degradation points in the temperature range 377 °C–397 °C. The addition of ionic liquid up to 50 wt% in PI films does not lead to any significant deterioration of the tensile strength of the polymer. The dynamic mechanical analysis results indicated both an increase of storage modulus E′ of PI/BAIM-TFSI composites at room temperature and a significant E′ decrease with temperature compared with the neat polymer. The cross-linking of the PI with polyetheramine Jeffamine D-400 allowed to prepare PI/Jeffamine/BAIM-TFSI (50%) membrane with E′ value of 300 MPa at 130 °C. The ionic conductivity of this cross-linked composite membrane reached the level of 10^?2 S/cm at 130 °C, suggesting, therefore, its potential use in medium-temperature fuel cells operating in water-free conditions.     

A novel ternary polymer electrolyte for LMP batteries based on thermal cross-linked poly(urethane acrylate) in presence of a lithium salt and an ionic liquid

A new ternary polymer electrolyte based on thermally cross-linked poly(urethane acrylate) (PUA), lithium bis(trifluoromethansulfonyl)imide (LiTFSI) and the ionic liquid N-butyl-N-methylpyrrolidinium TFSI (PYR₁₄TFSI) was developed and tested for application in LMP batteries. The polymer electrolyte was a transparent yellow self-standing material with quite good mechanical properties, i.e., comparable to that of a flexible rubber. The room temperature ionic conductivity of the dry polymer electrolyte was found to be as high as 0.1 mS cm⁻¹ for the compound containing 40 wt% of ionic liquid (PYR₁₄TFSI) and a O/Li ratio of 15/1 (Li⁺ from LiTFSI). The thermal analysis of the new cross-linked electrolyte showed that it was homogeneous, amorphous and stable over a wide temperature range extending from −40 °C to 100 °C. The homogeneity of the polymer electrolyte was also confirmed by SEM analysis.     

In-situ FTIR investigations on the reduction of vinylene electrolyte additives suitable for use in lithium-ion batteries

Lithium-ion batteries operate beyond the thermodynamic stability of the aprotic organic electrolyte used and electrolyte decomposition occurs at both electrodes. The electrolyte must therefore be composed in a way that its decomposition products form a film on the electrodes which stops the decomposition reactions but is still permeable to the Li(+) cations which are the charge carriers. At the graphite anode, this film is commonly referred to as a solid electrolyte interphase (SEI). Aprotic organic compounds containing vinylene groups can form an effective SEI on a graphitic anode. As examples, vinyl acetate (VA) and acrylonitrile (AN) have been investigated by in-situ Fourier transform infrared (FTIR) spectroscopy in a specially developed IR cell. The measurements focus on electrolyte decomposition and the mechanism of SEI formation in the presence of VA and AN. We conclude that cathodic reduction of the vinylene groups (i.e., via reduction of the double bond) in the electrolyte additives is the initiating and thus a most important step of the SEI-formation process, even in an electrolyte which contains only a few percent (i.e. electrolyte additive amounts) of the compound. The possibility of electropolymerization of the vinylene monomers in the battery electrolytes used is critically discussed on the basis of the IR data obtained.     

传感器用镓掺杂氧化锌纳米盘/纳米花状结构催化剂的制备及表面表征

采用简便的旋涂过程和一步水热法在压电基片上制备了Ga掺杂的ZnO纳米薄膜(GZO)。在水热处理过程中,通过添加不同的聚合物可形成纳米盘和纳米花状形貌的薄膜。采用场发射扫描电镜(Fe-SEM)、X射线衍射(XRD)和Raman光谱表征了样品的形貌、微结构和组成。 XRD和FE-SEM结果证明,在AlN/Si压电基片上形成的纳米盘、纳米棒和纳米花状GZO均为纤维锌矿相。采用浸渍法进一步在所制GZO样品上固定了绿色的荧光蛋白质(GFP)。运用原子力显微镜和荧光光谱分析了GFP与GZO表面结合的性质,考察了其用于传感器和生物成像技术的可行性。痕量GFP的固定使该材料产生荧光响应,表明其用于紫外光传感器时具有较好活性。     

Synthesis of novel hybrid films of a layered silicate and alkylammonium cations on rough polymeric surfaces by Langmuir–Blodgett method

Hybrid films of a layered silicate and an amphiphilic alkylammonium (hexadecyltrimethylammonium) cation have been prepared by Langmuir–Blodgett (LB) method and transferred onto a polyamide surface by dip coating. This is the first time that stable LB hybrid monolayer and multilayer films have been formed on rough polymeric surfaces. The films were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and water contact angle measurements. XRD and FTIR showed that the hybrid multilayer was well-organized and the thickness of one layer was calculated to be 1.6 nm. Furthermore, the layered silicate was determined to be on the substrate side and the amphiphilic molecule layer was exposed to the air side. This provides a novel methodology for the surface modification of polymers.     

硫酸介质中控制碳钢腐蚀的烷基取代Piperidin-4-one Oximes的立体效应

Three synthesized piperidin-4-one oximes,3-ethyl-2,6-diphenyl-piperidin-4-one oxime(A),1-methyl-3-isopropyl-2,6-diphenyl-piperidin-4-one oxime(B),and 3-isopropyl-2,6-diphenyl-piperidin-4-one oxime(C),were tested at different concentrations to determine their ability to inhibit corrosion of mild steel in 1 mol.L-1 H2SO4 and measured by a mass loss method(at various temperatures),polarization and impedance measurements,X-ray diffraction(XRD),scanning electron microscopy(SEM) with energy-dispersive X-ray spectroscopy(EDS),and a quantum chemical method.The synergistic influence of compounds A,B and C with iodides has also been evaluated.All three compounds show good inhibition efficiency in the following order:A>B>C.Compounds A,B and C were found to physically adsorb on the surface of mild steel while obeying the Temkin isotherm.Polarization measurements indicated that these compounds behave as a mixed mode inhibitor.XRD and SEM with EDS studies revealed the formation of a protective barrier on the mild steel surface by these oximes.The electron donating ability of the studied molecules was tested using semi empirical methods.The studies revealed that the oxime nitrogen,the piperidine moiety,and the phenyl ring assist largely in corrosion control.The studies also showed that the steric crowding by the alkyl group in the piperidine ring affects the inhibitor efficiency.Further,it is interesting to note that all of the studied compounds exhibit synergism with iodide ions.     

Nonwoven materials based on polyethylene oxide for use as a polymer electrolyte in memristive devices

Nonwoven materials were prepared by electrospinning from solutions of polyethylene oxide in water and in a 0.1 M aqueous lithium perchlorate solution. Addition of lithium perchlorate increases the conductivity of the solutions but does not alter their viscosity. The mean diameter of the fibers obtained was 100–500 nm. The supramolecular structure of the polymer underwent no significant changes in the course of electrospinning. The materials obtained can be applied directly onto organic memristive devices and used as a polymer electrolyte.

     

Quasi-solid-state dye-sensitized solar cell based on a polymer gel electrolyte with in situ synthesized ionic conductors

A polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors was prepared for fabricating a quasi-solid-state dye-sensitized solar cell (QS-DSSC). The in situ synthesized Acac-Py-I₂ ionic conductors show weaker influence on the liquid electrolyte absorbency of the polymer gel electrolyte than that of Acac-Py-I₂ ionic conductors dissolved in liquid electrolyte. Owing to the higher liquid electrolyte absorbency, the polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors shows higher ionic conductivity than that of polymer gel electrolyte with Acac-Py-I₂ ionic conductors absorbed from liquid electrolyte. QS-DSSC containing the polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors shows 3.815% energy conversion efficiency, which is 21.6% higher than that of QS-DSSC containing polymer gel electrolyte with Acac-Py-I₂ ionic conductors absorbed from liquid electrolyte.