Biying Huang

Lithium ion conduction in polymer electrolytes based on PAN

Abstract Polymer electrolytes based on polyacrylonitrile (PAN) with various plasticizers have been synthesized. Their electrical conductivities determined by AC impedance spectra are higher than 1 × 10−3 S · cm−1 at room temperature. IR and Raman spectra gave evidence of the interactions among PAN, plasticizer and lithium salt.

The mechanism of lithium ion transport in polyacrylonitrile-based polymer electrolytes

Abstract A dozen polyacrylonitrile (PAN)-based polymer electrolytes containing various plasticizers, have shown ionic conductivities higher than 1 × 10−3 S cm−1 at room temperature. In order to explain the high ionic conduction in these systems, X-ray diffraction (XRD), nuclear magnetic resonance (NMR), Raman scattering and infrared (IR) spectra have been measured systematically. Based on these results, a mechanism of Li+ ion transport in PAN-based polymer electrolytes has been suggested. There are three kinds of Li+ ions: one in the gel state of PAN, the other in solid PAN and the third in the plasticizer. The high ionic conduction is mainly caused by the Li+ ions in the gel state. These Li+ ions are coupled with the CN group in PAN and the CO group in the plasticizer. The Li+ ions can jump from one position to the next along a chain, while moving together with the chain.

Spectroscopic investigation of interactions among components and ion transport mechanism in polyacrylonitrile based electrolytes

Raman, infrared (IR), fluorescence, X-ray photoelectron (XPS), and nuclear magnetic resonance (NMR) spectra of various combinations of the components of the polyacrylonitrile (PAN)-based electrolytes have been studied, it is found that the so-called composite- or mixed-phase polymer electrolytes are not simple mixtures of electrolytic salt, plasticizer and polymer; instead there are strong interactions between each two of the components of the electrolytes and strong competitions between the plasticizer and PAN to associate with the Li+ ions though different systems may show different interaction characteristics. By analyzing the important roles of the plasticizer, a possible mechanism of the ion transport in the PAN-based polymer electrolyte is proposed

Investigation of the position of Li+ ions in a polyacrylonitrile-based electrolyte by Raman and infrared spectroscopy

The Raman spectra of polyacrylonitrile (PAN) and/or lithium perchlorate (LiClO4) complex containing plasticizer ethylene carbonate and the infrared spectra of the polymer electrolytes with different mass ratios of PAN to LiClO4 have been studied. It has been found that the lithium ions strongly interact with the C=N groups of PAN. However, at the ordinarily used content, say, the concentration of Li+ ions is as low as 5%, because of the high intensity of the characteristic vibration of the C=N group of PAN, it is very difficult to observe the interaction between the ions and the molecules. When the content of LiClO4 is raised to a certain extent, this interaction can be detected by way of Raman and IR spectroscopy. In both the Raman and IR spectra of the system of EC/PAN/LiClO4 with various mass ratios of PAN and LiClO4, a striking shoulder was observed at about 2270 cm(-1). By comparing the spectra of the system with that of EC/PAN and EC/LiClO4, the new shoulder was assigned to the interaction between Lit ions and the C=N groups of the PAN molecules. Copyright (C) 1996 Elsevier Science Ltd.

Infrared spectroscopic study of the interaction between lithium salt LiClO4 and the plasticizer ethylene carbonate in the polyacrylonitrile-based electrolyte

Abstract The infrared (IR) spectra of ethylene carbonate (EC) containing different contents of lithium perchlorate (LiClO 4 ) have been measured and analyzed. It is found that, with the increase of the LiClO 4 content in the solution, both the vibrational frequencies and the relative intensities of the bands related to the ring structure and to the CO group of EC molecule are changed. The data have shown that there is a rather strong interaction between the Li + ion and the EC molecule. The interactions between the Li + ions and the EC molecules mainly occur on the CO group of the molecules. In the meantime, the structure of the ClO 4 − anion is also affected by the EC molecules, forming solvent-shared ion pairs, Li + ECClO 4 .

Ion association and solvation studies of LiClO4 ethylene carbonate electrolyte by Raman and infrared spectroscopy

Dispersion strengthened (DS) Cu-Al25 alloy containing small Al2O3 particles (similar to 4 nm in diameter) was irradiated by 300 keV Cu+ ion to doses of 10 dpa and 30 dpa with a displacement rate of 3.7 x 10(-2) dpa/s at room temperature, which simulates the effects of high energy primary knock-on atoms (PKA) produced by 14 MeV neutrons. Microstructural evolution was investigated by transmission electron microscopy (TEM). Selected area diffraction (SAD) was used to study the phase stability of alumina under irradiation. The defect cluster structure formed by irradiation was investigated by dynamic two-beam techniques. Small particles of Al2O3 were dissolved under ion irradiation with increasing fluences. A large number of small Frank vacancy and interstitial dislocation loops (similar to 5 nm in diameter) with different Burgers vectors of a/3[1 1 1] are produced by ion irradiation. At the region adjacent to the irradiation surface the number of vacancy loops was greater than that of interstitial ones. This result is in good agreement with the computer simulation results

A Vibrational Spectroscopic Study on the Interaction Between Lithium Salt and Ethylene Carbonate Plasticizer for PAN‐Based Electrolytes

The Raman and infrared (IR) spectra of ethylene carbonate (EC) containing various concentrations of lithium perchlorate have been studied. It was found that both the vibrational frequencies and the relative intensities of the bands related to the ring structure and C=O group of the EC molecule change with the concentration of LiClO4 in the solution. The results indicate that there are rather strong interactions between Li+ ions and EC molecules. The interactions between the Li+ ions and EC molecules occur on all three oxygen atoms of the carbonate group. Another result given by Raman and IR spectroscopy is that the vibrational modes of ClO4- anions at 460 and at 624 cm(-1) are nearly as sensitive as the previously reported ClO4- bands at 930 cm(-1) in detecting ion aggregates in the LiClO4/EC solutions.

Vibrational spectroscopic study of the interaction between lithium perchlorate and dimethylsulfoxide

Abstract As part of the systematic research on the interactions between the components of the polyacrylonitrile-based electrolytes (plasticizer-lithium salt-polymer), the Raman and IR spectra of pure dimethylsulfoxide (DMSO) and DMSO containing different molar ratios of LiClO4 have been studied. By analyzing the Raman and IR spectra of the SO stretching band, it is found that the introduction of LiClO4 to pure DMSO leads to the dissociation of the cyclic dimers. Li+-DMSO associates are formed through the interaction between Li+ and the SO group of DMSO. The spectral changes of the SO binding bands and the CH stretching bands indicate that the interaction between the Li+ ion and the molecule not only breaks down the self-association of the solvent, but also, by way of the induction effect, perturbs the electronic nebula around the CH bond. It seems that the effect of the ClO4− anion on the molecules is too weak to be observed by the vibrational spectroscopy.

Raman scattering investigation of carbons obtained by heat treatment of a polyfurfuryl alcohol

Abstract Raman scattering was used to study the structural evolution of 4 h pyrolysed polyfurfuryl alcohol (PFA) between 200 and 900 °C. Three critical temperatures, i.e. carbonization, nucleation and crystallite growth temperatures, have been detected around 400, 550 and 700 °C respectively.

Characteristics of pyrolyzed phenol-formaldehyde resin as an anode for lithium-ion batteries

Abstract Polyacenic semiconductor (PAS) is obtained by pyrolyzing phenol-formaldehyde resin (PFR). The properties of PFR heat-treated at different temperatures are investigated. The lithium intercalation capacity of PAS as a function of heat-treatment temperature (HTT) exhibits a maximum at around 700 °C. A knee appears at 700 °C, not only in the plot of atomic ratio [H]/[C] versus HTT, but also in the plot of conductivity versus HTT. For PAS with a HTT of 700 °C, the maximum in the ratio of the relative intensity of Raman spectra at 1360 cm−1 corresponds to nanometer graphite, and that at 1580 cm−1 to graphite. A reasonable explanation of these phenomena is the transformation of nanometer graphite to graphite.