[en] A novel ferrocene-contained pyrrole, 4-(1H-pyrrol-1-yl) phenyl ferrocenecarboxylate (FcPy) was synthesized by esterification of 4-(1H-pyrrol-1-yl) phenol (PLPY) and ferrocenecarboxylic acid. Then the homopolymer of FcPy (PFcPy), copolymer of FcPy and pyrrole (P(FcPy-co-Py)), polypyrrole (PPy) were prepared by chemical oxidative polymerization. And the structure, morphology, electrochemical properties of prepared polymers were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), cyclic voltammograms (CV) and electrochemical impedance spectra (EIS), respectively. Also, the charge/discharge properties of the prepared polymers were studied by galvanostatic charge–discharge testing. The results demonstrated that the introduction of ferrocene to polypyrrole obviously improved the specific capacity of PPy cathode and gave a well-defined plateau at the potential rang of about 3.5 V. Under our experimental conditions, the discharge capacity of undoped PPy-based electrodes only presented 16.5 mAh g⁻¹ at 20 mA g⁻¹ between 2.5 and 4.2 V, while PFcPy-based electrodes exhibited an initial discharge capacity of up to 43.2 mAh g⁻¹. Specially, the P(FcPy-co-Py)-based electrodes even showed a discharge capacity of 68.1 mAh g⁻¹ and the improved discharge platform, which were ascribed to the resonance doping effect of pendant group, the advanced electrochemical nature of ferrocene moiety and the loose morphology of copolymer

[en] Highlights: ► The conductive network formation by electric field in both the PC/MWNTs and PC/MWNTs-COOH composites were investigated by the dynamic percolation measurement. ► At the percolation time and the formation activation energy of conductive network for MWNTs filled composites decreased greatly as compared to those of the MWNTs-COOH filled composites. ► The dynamic percolation measurement method could be recommended to investigate the zero-shear-rate viscosity at the different temperatures. - Abstract: Using polycarbonate (PC) as a matrix, and multi-wall carbon nanotubes (MWNTs) and acid-treated MWNTs (MWNTs-COOH) as fillers, PC/MWNTs and PC/MWNTs-COOH conductive composites were prepared, respectively. The conductive network formation induced by electric field in both the PC/MWNTs and PC/MWNTs-COOH composites were investigated by the dynamic percolation measurement. It was found that the electrical resistivity–time curves showed a certain self-similarity under various electric fields, i.e., the electrical resistivity decreased sharply as the percolation time (t_p) was reached. And the dynamic percolation time was shorten with the increase of the electric field intensity for both MWNTs and MWNTs-COOH filled PC composites. However, the percolation time and the formation activation energy of conductive network under electric field for MWNTs filled composites decreased greatly as compared to those of the MWNTs-COOH filled composites. These results indicated that the interaction between MWNTs and PC molecules played an important role in the conductive network formation under the electric field. Furthermore, the t_p values under the electric field for PC/MWNTs and PC/MWNTs-COOH composites were successfully predicted by a modified thermodynamic percolation model. And this dynamic percolation measurement method could be recommended to investigate the zero-shear-rate viscosity at the different temperatures.

[en] Highlights: → The spindle-shaped LiFePO₄ with hierarchical microporous structure self-assembled by nanoparticles has been synthesized by synthesis route B. → The feeding sequences and iron sources seriously affected the microstructures and electrochemical properties of the resulting LiFePO₄ cathodes. → The cell performances of the synthesized LiFePO₄ by synthesis route B were superior to that of LiFePO₄ by synthesis route A. - Abstract: In this work, LiFePO₄/C composites were prepared in hydrothermal system by using iron gluconate as iron source, and two feeding sequences during the preparation were comparatively studied. The morphology, crystal structure and charge-discharge performance of the prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and galvanostatic charge-discharge testing. The results showed that the feeding sequences and iron gluconate seriously affected the microstructures and electrochemical properties of the resulting LiFePO₄ cathodes in lithium ion batteries. The spindle-shaped LiFePO₄ with hierarchical microporous structure self-assembled by nanoparticles has been successfully synthesized by synthesis route B. In addition, the cell performance of the synthesized LiFePO₄ by synthesis route B was better than that of LiFePO₄ by synthesis route A. Specially at high rates, the superior rate performance of the spindle-shaped LiFePO₄/C microstructure (LFP/C-B) was revealed. And special reversible capacities of ∼118 and ∼95 mAh g^-1 were obtained at rates of 2 C and 5 C, comparing to ∼96 and ∼68 mAh g^-1 for LFP/C-A.

[en] Highlights: ► A novel LiFePO₄/graphene/carbon composite was prepared by using an in situ solvothermal method to synthesize LiFePO₄/graphene powders as precursor and then followed by carbon coating. ► A 3D conducting network constructed by the co-modification of graphenen and carbon coating significantly enhanced the electrochemical activity of LiFePO₄/carbon based electrode. ► With the graphene as an additive, the LiFePO₄/graphene/carbon composite revealed an attractive application prospect for the cathode material of lithium-ion batteries. - Abstract: A novel LiFePO₄/graphene/carbon composite as a performance-improved cathode material for lithium-ion batteries had been prepared by using an in situ solvothermal method to synthesize LiFePO₄/graphene powders as precursors and then followed by a carbon-coating process. The prepared samples of LiFePO₄/graphene/carbon was investigated comparatively with LiFePO₄/carbon and LiFePO₄/graphene composites by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and various electrochemical testing techniques. The results indicated that the co-modification of LiFePO₄ with graphene and carbon coating could construct an effective conducting network, which significantly enhanced the electrochemical activity of LiFePO₄/carbon based composite. Particularly, the LiFePO₄/graphene/carbon composite with a low content of graphene exhibited a high initial discharge capacity of 163.7 mAh g⁻¹ at 0.1 C and 114 mAh g⁻¹ at 5 C, as well as an excellent cycling stability.

[en] A novel amperometric glucose biosensor based on the nanocomposites of multi-wall carbon nanotubes (CNT) coated with polyaniline (PANI) and dendrimer-encapsulated Pt nanoparticles (Pt-DENs) is prepared. CNT coated with protonated PANI is in situ synthesized and Pt-DENs is absorbed on PANI/CNT composite surface by self-assembly method. Then Glucose oxidase (GOx) is crosslink-immobilizated onto Pt-DENs/PANI/CNT composite film. The results show that the fabricated GOx/Pt-DENs/PANI/CNT electrode exhibits excellent response performance to glucose, such as low detection limit (0.5 μM), wide linear range (1 μM-12 mM), short response time (about 5 s), high sensitivity (42.0 μA mM^-1 cm^-2) and stability (83% remains after 3 weeks).

[en] Two 2,2,6,6-tetramethylpiperidinyl-N-oxy (TEMPO) contained polypyrrole (PPy) derivatives with the different side-chain length were synthesized by esterification of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl free radial with pyrrole butyric acid and pyrrole caproic acid. Then the homopolymers of 4-(3-(Pyrrol-1-yl)butyryloxy)-2,2,6,6-tetramethylpiperidin-1-yloxy (PPy-B-TEMPO) and 4-(3-(Pyrrol-1-yl)hexanoyloxy)-2,2,6,6-tetramethylpiperidin-1-yloxy (PPy-C-TEMPO) were prepared by chemical oxidative polymerization. The structure, morphology, electrochemical properties of prepared polymers were characterized by fourier transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV-vis), scanning electron microscopy (SEM), cyclic voltammograms (CV) and electrochemical impedance spectra (EIS), respectively. Also, the charge-discharge properties of the prepared polymers were studied by galvanostatic charge-discharge testing. The results demonstrated that the as-synthesized nitroxide radical polymers showed a reversible two-electron redox reaction process in the potential limits of 2.5–3.0 V and 3.4–3.8 V vs Li/Li⁺, respectively. Under our experimental conditions, PPy only presented the discharge capacity of 16.5 mAh·g⁻¹ at 20 mA·g⁻¹ between 2.5 and 4.2 V, while PPy-B-TEMPO with the short side-chain linked to TEMPO groups exhibited an initial discharge capacity of up to 86.5 mAh·g⁻¹ with two well-defined plateaus. Furthermore, the PPy-C-TEMPO with the longer linking side-chain even displayed a discharge capacity of 115 mAh·g⁻¹. These superior electrochemical performances were ascribed to the flexible linking side-chain and the introduction of stable conductive PPy main chain, which benefits the improvement of charge carrier transportation in the aggregated polymer bulk