Co-Intercalation-Free Ether-Based Weakly Solvating Electrolytes Enable Fast-Charging and Wide-Temperature Lithium-Ion Batteries.

Ether-based electrolytes are competitive choices to meet the growing requirements for fast-charging and low-temperature lithium-ion batteries (LIBs) due to the low viscosity and low melting point of ether solvents. Unfortunately, the graphite (Gr) electrode is incompatible with commonly used ether solvents due to their irreversible co-intercalation into Gr interlayers. Here, we propose cyclopentyl methyl ether (CPME) as a co-intercalation-free ether solvent, which contains a cyclopentane group with large steric hindrance to obtain weakly solvating power with Li+ and a wide liquid-phase temperature range (-140 to +106 °C). A weakly solvating electrolyte (WSE) based on CPME and fluoroethylene carbonate (FEC) cosolvents can simultaneously achieve fast desolvation ability and high ionic conductivity, which also induces a LiF-rich solid electrolyte interphase (SEI) on the Gr anode. Therefore, the Gr/Li half-cell with this WSE can deliver outstanding rate capability, stable cycling performance, and high specific capacity (319 mAh g-1) at an ultralow temperature of -60 °C. Furthermore, a practical LiFePO4 (loading ≈25 mg cm-2)/Gr (loading ≈12 mg cm-2) pouch cell with this WSE also reveals outstanding rate capability and stable long-term cycling performance above 1000 cycles with a high Coulombic efficiency (≈99.9%) and achieves an impressive low-temperature application potential at -60 °C.

Effective Modulation of Exciton Binding Energies in Polymorphs of a Small-Molecule Acceptor for Organic Photovoltaics.

The operation mechanisms and energy losses for organic solar cells are essentially determined by the exciton binding energies (Eb) of organic active materials. Because the factor of chemical modifications is precluded, polymorphisms featuring different packing motifs of the same molecular structures provide an ideal platform for revealing the influence of solid-state packing. Herein, we have calculated the Eb values in three different cystal phases of a representative acceptor-donor-acceptor molecular acceptor (IDIC) by the self-consistent quantum mechanics/embedded charge approach. The results show that the differences of mere molecular packing modes can result in a substantial change in Eb of ≤50%, in the range of 0.21-0.34 eV among the three IDIC crystal phases. Moreover, a higher backbone packing dimensionality is found to be beneficial for obtaining a smaller Eb. This indicates that polymorph engineering is an effective way to reduce Eb toward low-energy-loss organic solar cells.

Chalcogen-substitution modulated supramolecular chirality and gas sensing properties in perylenediimides.

We present the modulation of van der Waals interactions to further adjust supramolecular chirality by incorporation of S and Se into the bay region. These chalcogen atom-mediated supramolecular interactions were transferred to nanostructures and affected the gas responses of devices. This study will facilitate the development of smart materials with modulated handedness in materials science.

Nitrogen-doped graphene aerogels as efficient supercapacitor electrodes and gas adsorbents.

Nitrogen-doped graphene has been demonstrated to be an excellent multifunctional material due to its intriguing features such as outstanding electrocatalytic activity, high electrical conductivity, and good chemical stability as well as wettability. However, synthesizing the nitrogen-doped graphene with a high nitrogen content and large specific surface area is still a challenge. In this study, we prepared a nitrogen-doped graphene aerogel (NGA) with high porosity by means of a simple hydrothermal reaction, in which graphene oxide and ammonia are adopted as carbon and nitrogen source, respectively. The microstructure, morphology, porous properties, and chemical composition of NGA were well-disclosed by a variety of characterization methods, such as scanning electron microscopy, nitrogen adsorption-desorption measurements, X-ray photoelectron spectroscopy, and Raman spectroscopy. The as-made NGA displays a large Brunauer-Emmett-Teller specific surface area (830 m(2) g(-1)), high nitrogen content (8.4 atom %), and excellent electrical conductivity and wettability. On the basis of these features, the as-made NGA shows superior capacitive behavior (223 F g(-1) at 0.2 A g(-1)) and long-term cycling performance in 1.0 mol L(-1) H2SO4 electrolyte. Furthermore, the NGA also possesses a high carbon dioxide uptake capacity at 1.0 bar and 273 K (11.3 wt %).

Probing the sensory property of perylenediimide derivatives in hydrazine gas: core-substituted aromatic group effect.

In this contribution, four perylenediimide derivatives (PTCDIs) with different core-substituted aromatic groups were prepared. Studies on their sensing properties in hydrazine vapor (10 ppm) suggested ∼5 orders of the magnitude in increased current for core-phenyl-substituted DEY was achieved and this value is 9, 9, and 24 times higher than that of core-pyridyl-substituted DSPY, DFPY, and DTPY, respectively. The differential response to the hydrazine vapor is less dependent on their surface area and morphologies. The lower LUMO energy and activation energy with smaller interplanar spacing allows DEY highly efficient sensing performance. A similar face-face packing mode and LUMO energy of DSPY and DFPY lead to both of them exhibiting the same sensing performance, while higher LUMO energy and head-to-tail packing modes with a greater interplanar spacing induce the less-efficient sensing performance of DTPY sensors. Discussions for structure-function relationships suggested that aromatic groups in the bay region have significant impact on PTCDI sensing performance by modulating energy level, interplanar spacing, and stacking modes.

Conducting polymer nanowire arrays for high performance supercapacitors.

This Review provides a brief summary of the most recent research developments in the fabrication and application of one-dimensional ordered conducting polymers nanostructure (especially nanowire arrays) and their composites as electrodes for supercapacitors. By controlling the nucleation and growth process of polymerization, aligned conducting polymer nanowire arrays and their composites with nano-carbon materials can be prepared by employing in situ chemical polymerization or electrochemical polymerization without a template. This kind of nanostructure (such as polypyrrole and polyaniline nanowire arrays) possesses high capacitance, superior rate capability ascribed to large electrochemical surface, and an optimal ion diffusion path in the ordered nanowire structure, which is proved to be an ideal electrode material for high performance supercapacitors. Furthermore, flexible, micro-scale, threadlike, and multifunctional supercapacitors are introduced based on conducting polyaniline nanowire arrays and their composites. These prototypes of supercapacitors utilize the high flexibility, good processability, and large capacitance of conducting polymers, which efficiently extend the usage of supercapacitors in various situations, and even for a complicated integration system of different electronic devices.

Patterned growth of vertically aligned polypyrrole nanowire arrays.

A facile strategy for preparing vertically aligned polypyrrole (PPy) nanoarrays with precisely controlled density and quantity is presented. The method involves two steps: (1) the fabrication of the patterned substrate via electron beam lithography and (2) the controlled growth of PPy nanowires via electrochemical polymerization on the patterned substrate. The electrical property of a single PPy nanowire is investigated via in situ conducting probe atomic force microscopy.

Patterned growth of polyaniline nanowire arrays on a flexible substrate for high-performance gas sensing.

Uniform patterning of polyaniline nanowire arrays on a wafer-sized flexible substrate is achieved by combining photolithography and in situ polymerization techniques. Chemical gas sensors based on the patterned polyaniline nanowire arrays exhibit excellent performance because of their highly ordered morphology and large specific surface area.

In situ electrochemical switching of wetting state of oil droplet on conducting polymer films.

Switching of wettability is achieved in situ, which is a challenge of materials science. Generally, changing liquid droplet is required to ex situ study the wettability response before and after the surface given a treatment, in the sense that the liquid impregnation in the surface structures is irreversible. Herein, an in situ wettability switch is achieved by utilizing the same liquid droplet to characterize the dynamic wettability when the conducting polymer is being stimulated. The oil droplet is facilitated to escape from the nanoscale traps through electrochemically tuning surface composition and surface micro/nanostructures, permitting a reversible and rapid transition between partly wetting and superantiwetting state. This in situ switch is promising for integration into a microfluidic system for the control of the liquid droplet's motion.

Decorating polypyrrole nanotubes with au nanoparticles by an in situ reduction process.

Au nanoparticle-decorated polypyrrole nanotubes (defined as PPy/Au nanocomposites) are prepared by an in situ reduction process. Polypyrrole (PPy) nanotubes are prepared by a self-degraded template method, and Au nanoparticles are deposited in situ by the reduction of HAuCl(4) . The size and uniformity of the Au nanoparticles that decorate the PPy nanotubes can be controlled by adjusting the experimental conditions, such as the stabilizers used and the reaction temperature. The morphologies and optical properties of the nanocomposites have been characterized by scanning electron microscopy, transmission electron microscopy, UV-vis, and FT-IR spectroscopy. Conductivity measurements show that the conductivities of the nanocomposites decrease with a decrease of temperature, and the conductivity-temperature relationship obeys the quasi-one dimensional variable range hopping model.