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The novel technique of centrifuged-electrospinning is employed to fabricate immiscible polyacrylonitrile (PAN)/polymethyl methacrylate (PMMA) polymer fibers, followed by carbonization to form ultra-thin carbon nanofibers (UT-CNF) with 28 ± 11 nm diameters. An additional centrifugal force provides a strong stretching force to stretch the dispersed droplets (PAN) into ultra-thin nanofibers, as confirmed by electron microscopy. This structure presents good electrochemical properties compared to electrospun carbon nanofibers with 126 ± 16 nm diameters. Electrochemical impedance spectroscopy analysis shows enhanced efficient surface areas, which accumulate ions more quickly, resulting in a decrease in the charge distribution and ion diffusion resistance because the reduction in diameter provides a short pore length and large outer surface. Applied to a supercapacitor, galvanostatic charge/discharge analysis gives a maximum specific capacitance of 243 F/g at 1 A/g and capacitance retention of 77.1% at a charge/discharge rate of 100 A/g for UT-CNF. This result is significantly higher than that of traditional electrospun carbon nanofibers.

Polyaniline is grafted onto the surface of high conductivity carbon nanotube-embedded carbon nanofibers (PANi-P-1.0) via plasma modification to fabricate an electrode for a high performance supercapacitor. The structure and morphology of polyaniline graft onto the carbon nanofiber (CNF) are confirmed by Raman, X-ray photoelectron spectroscopy, electron microscopy and transmission electron microscopy. The emeraldine base form of nanorod-polyaniline is well-distributed on the surface of the CNF. The PANi-P-1.0 has a high specific capacitance of 606 Fg−1. From the result of the electrochemical properties, the high capacitance is contributed by the electric double layer capacitance of the high conductivity CNF and the pseudocapacitance of the grafting polyaniline. In addition, compared to polyaniline coated on the surface of the CNF, the electrochemical properties of the PANi-P-1.0 are improved by reducing the charge transfer resistance (Rct) from 13.54 to 3.87 Ω, the Warburg coefficient from 101.39 to 47.96 Ωs−1/2 and the relaxation time constant from 0.794 to 0.194 s due to the covalent bond between the polyaniline and CNF. The PANi-P-1.0 also show excellent cycling stability after 1,000 cycles of galvanostatic charge and discharge because the free space around the grafting polyaniline allows volumetric change.

Plasma-treatment carbon nanotubes (CNTs) grafted with maleic anhydride (MA) were embedded in polyacryonitrile nanofibers via electrospinning and subsequently carbonizated at 800 °C to fabricate carbon nanofibers (CNFs). The grafted degree of MA on CNTs (CNTs-MA) was determined via Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The morphology, surface composition and conductivity of the CNTs-MA/CNF were characterized using electron microscopy, X-ray photoelectron and electrochemical impedance spectroscopy, respectively. CNTs-MA not only affected the conductivity of the CNFs but also the types of the nitrogen functional groups that could be represented as active sites on the CNFs to enhance the performance of the supercapacitors. When 2.5 wt.% CNTs-MA was embedded in the CNFs, the highest conductivity was obtained at 5.2 s/cm, and the amount of pyridinic and pyrrolic species increased to 70.3%. However, the highest capacitance was not obtained with 2.5 wt.% CNTs-MA added because of current leakage present in the system. The highest capacitance was 382 F/g with 1.0 wt.% CNTs-MA embedded in CNF with proper conductivity of 2.2 s/cm. Furthermore, galvanostatic charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy measurements also demonstrated that 1.0 wt.% CNTs-MA embedded in CNF resulted in better electrochemical reversibility and impendence properties.

A new gel-type polymer electrolyte (GPE) was made by the copolymerizing acrylonitrile (AN) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). The copolymer mixed with a plasticizer—propylene carbonate (PC) and lithium salt to form GPE. The lithium salts are LiCF 3 SO 3 , LiBr and LiClO 4 . FT-IR spectra show that the lithium ion in the LiClO 4 system has the strongest interaction with the group based on the plasticized polymer. FT-IR spectra also indicate that CF 3 SO 3 − prefers producing anion–cation association. Moreover, the 13 C solid state NMR spectra for the carbons attached to the PC of GPE exhibited different level of chemical shift (158.5 ppm) when the different lithium salts were added to the electrolyte. The results of differential scanning calorimeter (DSC) also indicate that the LiClO 4 system has more free lithium ions; therefore, it has the maximum conductivity. In this study, the highest conductivity 2.98 × 10 −3 S cm −1 exists in AG2/PC = 20/80 wt.% system which contain 3 mmole (g-polymer) −1 LiClO 4 . Additionally, the polymer electrolytes, which contain GMA-IDA have better interfacial resistance stability with lithium electrode.

Polyurethaneureas (PUU), which were synthesized from 4,4′-diphenylmethane diisocyanate (MDI), poly(ethylene glycol) (PEG), and 3,5-diaminobanzoic acid (DABA), were used as polyelectrolytes in this study. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) were used to monitor the effect of the various kinds of PEG on the changes in morphology of PUU electrolytes corresponding to the concentration of lithium perchlorate (LiClO 4 ) dopants. The results of DSC and FT-IR indicate the Li + ions coordinate with the soft and hard segments. Additionally, the crystallinity of the PEG soft segment and the ordered hydrogen-bonded urea carbonyl groups decreased with increasing salt concentration. Impedance spectroscopy (IS) measurements show that the PUU electrolyte with the high phase separation degree has the high ionic conductivity. The hard-segment T g and the soft-segment T m influence the conductivity behavior of polyelectrolytes with increasing measurement temperature.

Polyelectrolytes, in this study were synthesized from styrene–maleic anhydride (SMA) copolymer, poly(ethylene glycol)400 (PEG400), and lithium perchlorate (LiClO4). Fourier transform infrared spectroscopy (FTIR), and 7 Li magic angle spinning (MAS) solid-state NMR were used to monitor the interaction between Li+ ions and polymer. The results of FTIR and 7 Li MAS solid-state NMR indicate the Li+ ions are preferentially coordinated to the ether oxygen of PEG. The Tg of the PEG segments in polyelectrolyte increases with LiClO4 concentration, as determined by differential scanning calorimetry (DSC), indicating that solubility of the Li+ ions in the host polymer increases with the PEG content. Impedance spectroscopy (IS) shows that the bulk conductivity of polyelectrolytes and the conductivity behavior obeys the Vogel–Tamman–Fulcher (VTF) equation.

Polyurethaneureas (PUU), which were synthesized from 4,4′-diphenylmethane diisocyanate (MDI), poly(ethylene glycol) (PEG, MW=2000), and 3,5-diaminobenzoic acid, were used as the matrix of the polyelectrolytes in this study. Differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), and 7Li magic angle spinning (MAS) solid-state NMR were used to monitor changes in the morphology of PUU electrolytes corresponding to the concentration of lithium perchlorate (LiClO4) dopants. The results of DSC and FT-IR indicate the different polymer complexes formed by the interaction of the Li+ ions with the different coordination sites of PUU. The 7Li MAS solid-state NMR investigation of the PUU electrolytes points out that two different Li+ environments exist at lower temperature. The results of DSC and the 7Li MAS solid-state NMR show that Li+ ions are preferentially coordinated to the ether oxygen of the PEG soft-segment when the salt concentration is below 0.1 mmol LiClO4(gPUU)−1. Impedance spectroscopy measurements show that the conductivity behavior followed the Arrhenius equation and was influenced by the hard-segment Tg. One of the PUU electrolytes under the investigation has an ionic conductivity as high as 3.0×10−5 S cm−1 at 30 °C.

The behaviors of lithium ions in a comb-like polymer electrolyte with chelating functional group complexed with LiCF3SO3, LiBr and LiClO4 were characterized by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, AC impedance, and 13C solid-state NMR measurement. The comb-like copolymer was synthesized from poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). FT-IR spectra reveal the interactions of Li+ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. FT-IR spectra also indicate an increasing anion–cation association consistent with increasing LiCF3SO3 concentrations. Moreover, the 13C solid-state NMR spectra for the carbons attached to the ether oxygen atoms exhibited significant line broadening and a slight upfield chemical shift when the dopant was added to the polymer. These findings indicate coordination between the Li cation and the ether oxygens in the PEG segment. Tg and Td of copolymers doped with salts clearly increase, as shown by DSC and TGA measurements. These results indicate the interactions of Li+ with both PEGMEM and GMA-IDA segments form transient cross-links inside the copolymers. The Vogel–Tamman–Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chain in this study. The maximum conductivity of copolymers relates to the composition of the copolymers and the concentration of doping lithium ions. In summary, the GMA-IDA unit in the copolymer promotes the dissociation of the lithium salt, the mechanical strength and the conductivity of the polyelectrolyte.

Novel thermoplastic polyurethanes with chelating groups were synthesized from 4,4′-diphenylmethane diisocyanate (MDI), poly(ethylene glycol) (PEG), and EP-IDA. Differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FT-IR), and impedance spectroscopy (IS) were used to monitor changes in the morphology of these polyurethanes with the concentration of lithium perchlorate (LiClO4) dopants. Adding the salt significantly changes the FTIR spectrum of the polyurethane, indicating an interaction between the lithium cation within the urethane group and the chelating group. The soft segment Tg increases with LiClO4 concentration, as determined by DSC, indicating that solubility of the lithium cation in the host polyurethane increases with the chelating groups. IS shows that the bulk conductivity reaches a maximum as the salt concentration is increased. One of the investigated polyurethane electrolytes has an ionic conductivity as high as ∼10−6 S cm−1 at room temperature.