V. Di Noto

Poly[(oligoethylene glycol) dihydroxytitanate] as organic-inorganic polymer-electrolytes

Abstract Two new poly[(oligoethylene glycol) dihydroxytitanate] electrolytic systems were prepared by a polycondensation reaction between: Ti(OEt) 4 and polyethylene glycol 400 (PEG 400) (I), and Ti(OEt) 4 and PEG 400/LiCl complex (II). The polymers thus obtained show a solid rubbery consistency and are very stable under inert atmosphere. The structure, morphology and conductivity of these materials were investigated. On the basis of analytical data and vibrational studies it was concluded that polymers (I) and (II) are inorganic–organic materials with titanium atoms bonded together by PEG bridges. Particularly, inter-chain interactions in polymer (I) occur by means of hydrogen bonds between titanium hydroxyl groups and ethereal oxygens of PEG chains, while polymer (II) contains both titanium–PEG interactions and a second type of inter-chain interaction due to the presence of hydrogen bonding clusters around Cl − ions. Scanning electron microscopy (SEM) revealed two types of morphologies in polymers (I) and (II). Conductivity measurements made at different temperatures indicated that both polymers conduct ionically. Two conductivity mechanisms are present in these materials, which are strongly influenced by segmental motions of the polymer chains. At 25°C polymers (I) and (II) showed conductivities of ca. 3×10 −6 and 4×10 −6 S cm −1 , respectively.

Zeolitic inorganic–organic polymer electrolytes: synthesis, characterization and ionic conductivity of a material based on oligo(ethylene glycol) 600, (CH3)2SnCl2 and K4Fe(CN)6

This paper reports the synthesis of a new Z-IOPE material based on poly(ethylene glycol) 600, (CH3)2SnCl2 and K4Fe(CN)6. This material was synthesized via a sol-gel transition. FIR and MIR spectroscopy studies together with detailed compositional data allowed us to propose a final structure for this Z-IOPE material. It was concluded that this compound is a mixed inorganic-organic network in which clusters formed by tin and iron complexes are bonded together by PEG 600 bridges. The conformation of polyethereal chains in the bulk material is of the TGT (T=trans, G=gauche) type. Impedance spectroscopy measurements revealed that the material has a conductivity of 4.77.10−5 S cm−1 at 21.3°C.

Vibrational studies of the ion–polymer interactions in α-hydro-ω-oligo(oxyethylene)hydroxy-poly[oligo(oxyethylene)oxydimethylsililene]/δ-MgCl2

Abstract Polymer–polymer and salt–polymer interactions of seven electrolytic complexes based on α-hydro-ω-oligo(oxyethylene)hydroxy-poly[oligo(oxyethylene)oxydimethylsililene] and δ-MgCl 2 were studied. This aim was pursued by means of an accurate medium and far FT-IR spectroscopic analysis. By using the decomposition and difference spectroscopy techniques, intensity and frequency of terminal OH and CO stretchings were evaluated in order to detect the presence of anion clusters build up by the coordination of Cl − with -OH groups. The number of chlorine anions per chain coordinated magnesium was established. This analysis allowed us to gain a complete structural picture for these materials, pointing out three possible coordinations of magnesium by polyethereal chains.

Study of electrochemical properties and thermal stability of the high-voltage spinel cathode material for lithium-ion accumulators

This article deals with the properties of high-voltage cathode material LiNi0.5Mn1.5O4 synthesised by a solid-state reactions method. The sample—LiNi0.5Mn1.5O4—was synthesised by two steps of annealing process. A number of electrochemical and physical methods were used to analyse the samples. The obtained LiNi0.5Mn1.5O4 powder was characterised by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and galvanostatic charge/discharge measurements at different loads and high temperature in lithium-ion cells with metal lithium as a counter electrode. All these analyses were used for confirmation of the structure of the material LiNi0.5Mn1.5O4 and for investigating its electrochemical properties. A special analysis was used for this paper to understand and confirm the function of this type of material. It is called electron paramagnetic resonance (EPR) spectroscopy, which is used in the field of lithium-ion batteries and also which is not common. This analysis is typically used to analyse free radicals. It is possible to study changes of valence in cathode materials during charging and confirming the valence change of Mn from Mn3+ to Mn4+ and of Ni from Ni2+ to Ni3+ and then to Ni4+ with EPR analysis. Thermogravimetric (TG) analysis of stability of the material LiNi0.5Mn1.5O4 with in situ observation of structural changes by SEM was used as the last analysis.

Synthesis of Nanocomposites from Pd0 and a Hyper-Cross-Linked Functional Resin Obtained from a Conventional Gel-Type Precursor

Hyper-cross-linked resins stemming from a gel-type poly-chloromethylated poly(styrene-co-divinylbenzene) resin (GT) have been investigated by a multi-methodological approach based on elemental analysis, scanning electron microscopy, X-ray microanalysis, and solvent absorption. The hyper-cross-linking of the parent resin was accomplished by Friedel-Crafts alkylation of the phenyl rings of the resins with the chloromethyl groups. This produced a permanent pore system comprising both micropores (<2.0 nm in diameter) and mesopores (2.2 nm). The chloromethyl groups that did not react in the hyper-cross-linking step were transformed into methylmercaptan groups and the latter were then converted into sulfonic groups by oxidation with hydrogen peroxide. By this procedure the extensive permanent porosity of the parent unsulfonated hyper-cross-linked polymer (HGT) was retained by the sulfonated polymer (HGTS). The final exchange capacity of HGTS was determined to be 0.36 mmol g(-1). HGTS was easily metalated with Pd(II) and the subsequent reduction of the metal centers with either aqueous sodium borohydride, formaldehyde, or dihydrogen produced three Pd(0)/HGTS nanocomposites. The metal nanoparticles had diameters in the 1-6 nm range for all the nanocomposites, as determined by TEM, but with somewhat different distributions. When formaldehyde was used, more than 90% of the nanoparticles were less than 3 nm and their radial distribution throughout the polymer beads was quite homogeneous. These findings show that with this reducing agent the metal nanoparticles are generated within the pore system of the polymer matrix, hence their size is controlled by the dimensions of the pores of the polymeric support.

The influence of used precursors on the properties of high-voltage cathode materials

This article deals with the influence of precursors used in the high-voltage cathode material LiNi0.5Mn1.5O4 based on the LiMn2O4 material on its properties. Precursors with various sizes of particles were used for making the cathode material. Consequently, its influence on the stability during cycling, change of load, and the influence of higher temperatures during cycling were investigated. Produced materials were further analyzed to discover the influence of the change of the used precursor on the structure of the cathode material. The structure of the material deposited on Al foil was investigated by atomic force microscopy (AFM), and also X-ray photoelectron spectroscopy (XPS) analysis was performed. The materials were then observed by SEM and analyzed by the EDAX method. The results show that smaller particle size enhances the properties of cathode material both in the stability during cycling and higher capacity and also the potential under higher load.

Interplay between humidity, temperature and electrical response of a conductivity sensor based on a La2LiNbO6 double perovskite

The La2LiNbO6 perovskite has been prepared in the polycrystalline form by a solid state reaction. Structural characterization by means of monochromatic X-ray and neutron powder diffraction (XRD and ND) and Rietveld refinement showed that the crystal structure belongs to the group of 1 : 1 B-site rock-salt ordered double perovskites with the most common tilting system amongst them being a−a−b+ (S. G. P21/n, a = 5.61612(3), b = 5.76645(2), c = 7.94107(4) A, β = 90.276(2)°). Scanning Transmission Electron Microscopy (STEM) evidences that there is no cross-substitution between Li and Nb and that a remaining portion of lanthanum is randomly located in the projected positions of lithium. Impedance spectroscopy has been used to analyse the electrical-response properties of the materials. Conductivity is strongly dependent on the relative humidity (RH), changing by about 3 orders of magnitude between 25 and 90% RH. However, no conductivity increase with change in RH% is observed when the lateral surfaces of the sensor are covered with paraffin. This confirms that adsorption of water by the sample plays a crucial role in modulating the conduction mechanism. La2LiNbO6 also exhibits a very good durability, reproducibility, response time, hysteresis and dynamic linearity to be considered as a promising sensing material for a practical humidity sensor.