Shuanjin Wang

Polymer electrolytes for lithium polymer batteries

In this review, state-of-the-art polymer electrolytes are discussed with respect to their electrochemical and physical properties for their application in lithium polymer batteries. We divide polymer electrolytes into the two large categories of solid polymer electrolytes and gel polymer electrolytes (GPE). The performance requirements and ion transfer mechanisms of polymer electrolytes are presented at first. Then, solid polymer electrolyte systems, including dry solid polymer electrolytes, polymer-in-salt systems (rubbery electrolytes), and single-ion conducting polymer electrolytes, are described systematically. Solid polymer electrolytes still suffer from poor ionic conductivity, which is lower than 10−5 S cm−1. In order to further improve the ionic conductivity, numerous new types of lithium salt have been studied and inorganic fillers have been incorporated into solid polymer electrolytes. In the section on gel polymer electrolytes, the types of plasticizer and preparation methods of GPEs are summarized. Although the ionic conductivity of GPEs can reach 10−3 S cm−1, their low mechanical strength and poor interfacial properties are obstacles to their practical application. Significant attention is paid to the incorporation of inorganic fillers into GPEs to improve their mechanical strength as well as their transport properties and electrochemical properties.

Synthesis and characterization of novel sulfonated poly(arylene thioether) ionomers for vanadium redox flow battery applications

High-molecular-weight poly(arylene thioether ketone) (PTK) and poly(arylene thioether ketone ketone) (PTKK) polymers were successfully synthesized by one-pot polymerization of N,N′-dimethy-S-carbamate masked dithiols with activated dihalo compounds, followed by post-sulfonation using chlorosulfonic acid as the sulfonation agent in dichloromethane solution to give the production of sulfonated poly(arylene thioether ketone) (SPTK) and sulfonated poly(arylene thioether ketone ketone) (SPTKK) with appropriate ion-exchange capacities. The chemical structures were confirmed by 1H NMR, FT-IR and elemental analysis (EA). The thermal properties were fully investigated by TGA-IR. The synthesized SPTK and SPTKK polymers are soluble in aprotic solvents such as N,N′-dimethylacetamide (DMAc), N,N′-dimethylformamide and dimethyl sulfoxide, and can be cast into membranes on a glass plate from their DMAc solution. The proton conductivities of these membranes are comparable to Nafion117 membranes under the same conditions. Cell performance tests showed that the vanadium redox flow batteries (VRBs) assembled with SPTK and SPTKK membranes possessed higher Coulombic efficiencies than VRBs assembled with Nafion117 membranes at the current density of 50 mA cm−2, because of their one-order-of magnitude lower VO2+ permeabilities. In conclusion, these ionomers could be promising candidates as proton-exchange membranes for vanadium redox flow battery (VRB) applications.

Nearly 100% internal phosphorescence efficiency in a polymer light-emitting diode using a new iridium complex phosphor

A new iridium complex with a phenylphthalazine ligand has been prepared by an unexpected method and polymer light-emitting devices doped with the complex have been achieved with nearly 100% internal phosphorescence efficiency.

Sulfur@graphene oxide core–shell particles as a rechargeable lithium–sulfur battery cathode material with high cycling stability and capacity

Sulfur@GO core–shell composites were prepared by the self-assembly of sulfur particles stabilized by a cationic surfactant and anionic graphene oxide nanosheets through electrostatic interaction. Due to the effective entrapment of polysulfide intermediates by the GO shell, the composites exhibit high cycling stability with 81% capacity maintenance over 210 cycles as the cathode for Li–S batteries.

A Rigid Naphthalenediimide Triangle for Organic Rechargeable Lithium‐Ion Batteries

Dr. D. Chen, A.-J. Avestro, Dr. J. Sun, Z. Erno, Prof. J. Fraser Stoddart Department of Chemistry Northwestern University 2145 Sheridan Road , Evanston , IL 60208–3113 , USA E-mail: stoddart@northwestern.edu Dr. Z. Chen, Dr. K. Amine Chemical Sciences and Engineering Division Argonne National Laboratory 9700 South Cass Avenue, Building 200 , Argonne , IL 60439–4837 , USA Prof. S. Wang, Prof. M. Xiao, Prof. Y. Meng The Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province Sun Yat-sen University Guangzhou 510275 , P. R. China Dr. M. M. Algaradah, Dr. M. S. Nassar Joint Center of Excellence in Integrated Nanosystems King Abdulaziz City for Science & Technology Riyadh 11442 , Kingdom of Saudi Arabia

Novel application of thermally expanded graphite as the support of catalysts for direct synthesis of DMC from CH3OH and CO2

Novel Cu-Ni bimetallic catalysts supported on thermally expanded graphite (TEG) were prepared as an example to show the particular characteristics of TEG as a carbon support material. The structures of TEG and the synthesized Cu-Ni/TEG catalysts were characterized using BET, FTIR, TG, SEM, TEM, XRD and TPR techniques. The catalytic activities of the prepared catalysts were investigated by performing micro-reaction in the direct synthesis of dimethyl carbonate (DMC) from CH3OH and CO2. The experimental results indicated that the prepared Cu-Ni/TEG catalysts exhibited highly catalytic activity. Under the optimal catalytic conditions at 100 degrees C and under 1.2 MPa, the highest conversion of CH3OH of 4.97% and high selectivity of DMC of 89.3% can be achieved. The highly catalytic activity of Cu-Ni/TEG in DMC synthesis can be attributed to the synergetic effects of metal Cu, Ni and Cu-Ni alloy in the activation of CH3OH and CO2 and the particular characteristics of TEG as a carbon support material.

Mechanical, Thermal, and Morphological Properties of Glass Fiber-reinforced Biodegradable Poly(propylene carbonate) Composites

Glass fiber (GF)-reinforced biodegradable poly(propylene carbonate) (PPC) composites were prepared by melt blending. The effects of reinforcement on the mechanical, thermal, and morphological properties of the PPC/GF composites were investigated. The mechanical properties of the composites were found to be improved obviously by the incorporation of GF. Experimental results of the thermal properties indicated that the GF addition led to the improvement on the thermal stability of the composites, and that the Vicat softening temperature (VST) of the composites was much higher than that of pure PPC resin. Scanning electron microscopic examination revealed a uniform dispersion of GF within PPC matrix at low GF loading level. It was observed that the GF appeared to be oriented within the PPC matrix to some extent, and there was good interfacial adhesion between GF and PPC matrix.Glass fiber (GF)-reinforced biodegradable poly(propylene carbonate) (PPC) composites were prepared by melt blending. The effects of reinforcement on the mechanical, thermal, and morphological properties of the PPC/GF composites were investigated. The mechanical properties of the composites were found to be improved obviously by the incorporation of GF. Experimental results of the thermal properties indicated that the GF addition led to the improvement on the thermal stability of the composites, and that the Vicat softening temperature (VST) of the composites was much higher than that of pure PPC resin. Scanning electron microscopic examination revealed a uniform dispersion of GF within PPC matrix at low GF loading level. It was observed that the GF appeared to be oriented within the PPC matrix to some extent, and there was good interfacial adhesion between GF and PPC matrix.

Novel polyaromatic ionomers with large hydrophilic domain and long hydrophobic chain targeting at highly proton conductive and stable membranes

A novel dihydroxyl monomer bearing 18 electron rich phenyl rings were synthesized and polymerized with other monomers bearing electron deficient phenyl rings to give dense and selective sites in macromolecules for post-sulfonation, which was successfully conducted in ClSO3H/CH2Cl2 solution at room temperature in a subsequential step. The chemical structures were confirmed by 1H NMR and FT-IR spectra. The ionic exchange capacity (IEC) was controlled to be from 0.65 to 1.21 mequiv g−1 to afford considerable proton conductivity. Distinct phase separation was observed in the resulting membranes from SAXS profiles. The SPAEK-5 with an IEC of 1.21 mequiv g−1 gave better proton conductivity than Nafion 117 at all tested temperatures under 100% relative humidity. The membranes exhibited an exceeding stability when immersing in Fentons reagent (3 wt.% H2O2 + 2 ppm FeSO4) at 80 °C. These properties make them promising candidates for electrochemical applications.

A proton exchange membrane fabricated from a chemically heterogeneous nonwoven with sandwich structure by the program-controlled co-electrospinning process

A composite proton exchange membrane containing electrospun nanofibers shows excellent oxidative stability and high proton conductivity as well as an extremely low activation energy of 1.30 kJ mol(-1).

Novel Cu–Fe bimetal catalyst for the formation of dimethyl carbonate from carbon dioxide and methanol

A novel Cu–Fe bimetal supported catalytic system was prepared and applied to the direct dimethyl carbonate (DMC) formation from methanol and CO2. The prepared catalysts were characterized by means of temperature-programmed reduction (TPR), X-ray powder diffraction (XRD), laser Raman spectra (LRS), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Metallic Cu, Fe and oxygen deficient Fe2O3−x (0 < x < 3) were formed during the reduction and activation step. The supported Cu–Fe bimetal catalysts exhibited good catalytic activity and high stability for the direct DMC formation. Under the reaction conditions at 120 °C and 1.2 MPa with space velocity of 360 h−1, the highest methanol conversion of 5.37% with DMC selectivity of 85.9% could be achieved. The high catalytic performance of the Cu–Fe bimetal catalysts in the DMC formation could be attributed to the interaction of base sites functioned by metallic Cu and Fe with acid sites provided by oxygen deficient Fe2O3−x (0 < x < 3) in the activation of methanol and CO2. The moderate concentration balance of acid and base sites was in favor of DMC formation.