The Experts below are selected from a list of 8121 Experts worldwide ranked by ideXlab platform

Fei Wei - One of the best experts on this subject based on the ideXlab platform.

  • janus separator of polypropylene supported cellular graphene framework for sulfur cathodes with high utilization in lithium sulfur batteries
    Advanced Science, 2016
    Co-Authors: Hongjie Peng, Jiaqi Huang, Xinbing Cheng, Fei Wei, Daiwei Wang, Zhe Yuan, Qiang Zhang
    Abstract:

    Owing to the conversion chemistry of the sulfur cathode, the lithium–sulfur (Li–S) batteries exhibit high theoretical energy density. However, the intrinsic mobile redox centers during the sulfur/Li2S-to-lithium polysulfides solid-to-liquid phase transition induce low sulfur utilization and poor cycling life. Herein, the Janus separator of mesoporous cellular graphene framework (CGF)/polypropylene membrane to promote the utilization of sulfur cathode is introduced. The porous polypropylene membrane serves as an insulating substrate in contact with lithium anode while CGFs that possess high electrical conductivity of 100 S cm−1, a large mesopore volume of 3.1 cm3 g−1, and a Huge Surface Area of 2120 m2 g−1 are adhered on cathode side to reactivate the shuttling-back polysulfides and to preserve the ion channels. Therefore, the Li–S cell with the “two-face” CGF Janus separator exhibit a high initial capacity of 1109 mAh g−1 and superior capacity preserved upon 800 mAh g−1 after 250 cycles at 0.2 C, which is 40% higher on sulfur utilization efficiency than the corresponding results with routine polypropylene separators. There are significant improvements on capacity as well as electrochemical kinetics. A very high Areal capacity of 5.5 mAh cm−2 combined with high sulfur content of 80% and Areal loading amount of 5.3 mg cm−2 is achieved for such advanced configuration. The negative impact of shuttle mechanism on lowering the utilization of sulfur and overall energy density of a Li–S battery is well eliminated by applying CGF separators. Consequently, employing carbonaceous materials as Janus face of separators enlightens new opportunities for improving the utilization of active materials and energy density of devices that involve complex phase evolution and conversion electrochemistry.

  • nanoarchitectured graphene cnt porous carbon with extraordinary electrical conductivity and interconnected micro mesopores for lithium sulfur batteries
    Advanced Functional Materials, 2014
    Co-Authors: Hongjie Peng, Jiaqi Huang, Mengqiang Zhao, Qiang Zhang, Xinbing Cheng, Xinyan Liu, Weizhong Qian, Fei Wei
    Abstract:

    The sp2-hybridized nanocarbon (e.g., carbon nanotubes (CNTs) and graphene) exhibits extraordinary mechanical strength and electrical conductivity but limited external accessible Surface Area and a small amount of pores, while nanostructured porous carbon affords a Huge Surface Area and abundant pore structures but very poor electrical conductance. Herein the rational hybridization of the sp2 nanocarbon and nanostructured porous carbon into hierarchical all-carbon nanoarchitectures is demonstrated, with full inherited advantages of the component materials. The sp2 graphene/CNT interlinked networks give the composites good electrical conductivity and a robust framework, while the meso-/microporous carbon and the interlamellar compartment between the opposite graphene accommodate sulfur and polysulfides. The strong confinement induced by micro-/mesopores of all-carbon nanoarchitectures renders the transformation of S8 crystal into amorphous cyclo-S8 molecular clusters, restraining the shuttle phenomenon for high capacity retention of a lithium-sulfur cell. Therefore, the composite cathode with an ultrahigh specific capacity of 1121 mAh g−1 at 0.5 C, a favorable high-rate capability of 809 mAh g−1 at 10 C, a very low capacity decay of 0.12% per cycle, and an impressive cycling stability of 877 mAh g−1 after 150 cycles at 1 C. As sulfur loading increases from 50 wt% to 77 wt%, high capacities of 970, 914, and 613 mAh g−1 are still available at current densities of 0.5, 1, and 5 C, respectively. Based on the total mass of packaged devices, gravimetric energy density of GSH@APC-S//Li cell is expected to be 400 Wh kg−1 at a power density of 10 000 W kg−1, matching the level of engine driven systems.

Qiang Zhang - One of the best experts on this subject based on the ideXlab platform.

  • janus separator of polypropylene supported cellular graphene framework for sulfur cathodes with high utilization in lithium sulfur batteries
    Advanced Science, 2016
    Co-Authors: Hongjie Peng, Jiaqi Huang, Xinbing Cheng, Fei Wei, Daiwei Wang, Zhe Yuan, Qiang Zhang
    Abstract:

    Owing to the conversion chemistry of the sulfur cathode, the lithium–sulfur (Li–S) batteries exhibit high theoretical energy density. However, the intrinsic mobile redox centers during the sulfur/Li2S-to-lithium polysulfides solid-to-liquid phase transition induce low sulfur utilization and poor cycling life. Herein, the Janus separator of mesoporous cellular graphene framework (CGF)/polypropylene membrane to promote the utilization of sulfur cathode is introduced. The porous polypropylene membrane serves as an insulating substrate in contact with lithium anode while CGFs that possess high electrical conductivity of 100 S cm−1, a large mesopore volume of 3.1 cm3 g−1, and a Huge Surface Area of 2120 m2 g−1 are adhered on cathode side to reactivate the shuttling-back polysulfides and to preserve the ion channels. Therefore, the Li–S cell with the “two-face” CGF Janus separator exhibit a high initial capacity of 1109 mAh g−1 and superior capacity preserved upon 800 mAh g−1 after 250 cycles at 0.2 C, which is 40% higher on sulfur utilization efficiency than the corresponding results with routine polypropylene separators. There are significant improvements on capacity as well as electrochemical kinetics. A very high Areal capacity of 5.5 mAh cm−2 combined with high sulfur content of 80% and Areal loading amount of 5.3 mg cm−2 is achieved for such advanced configuration. The negative impact of shuttle mechanism on lowering the utilization of sulfur and overall energy density of a Li–S battery is well eliminated by applying CGF separators. Consequently, employing carbonaceous materials as Janus face of separators enlightens new opportunities for improving the utilization of active materials and energy density of devices that involve complex phase evolution and conversion electrochemistry.

  • nanoarchitectured graphene cnt porous carbon with extraordinary electrical conductivity and interconnected micro mesopores for lithium sulfur batteries
    Advanced Functional Materials, 2014
    Co-Authors: Hongjie Peng, Jiaqi Huang, Mengqiang Zhao, Qiang Zhang, Xinbing Cheng, Xinyan Liu, Weizhong Qian, Fei Wei
    Abstract:

    The sp2-hybridized nanocarbon (e.g., carbon nanotubes (CNTs) and graphene) exhibits extraordinary mechanical strength and electrical conductivity but limited external accessible Surface Area and a small amount of pores, while nanostructured porous carbon affords a Huge Surface Area and abundant pore structures but very poor electrical conductance. Herein the rational hybridization of the sp2 nanocarbon and nanostructured porous carbon into hierarchical all-carbon nanoarchitectures is demonstrated, with full inherited advantages of the component materials. The sp2 graphene/CNT interlinked networks give the composites good electrical conductivity and a robust framework, while the meso-/microporous carbon and the interlamellar compartment between the opposite graphene accommodate sulfur and polysulfides. The strong confinement induced by micro-/mesopores of all-carbon nanoarchitectures renders the transformation of S8 crystal into amorphous cyclo-S8 molecular clusters, restraining the shuttle phenomenon for high capacity retention of a lithium-sulfur cell. Therefore, the composite cathode with an ultrahigh specific capacity of 1121 mAh g−1 at 0.5 C, a favorable high-rate capability of 809 mAh g−1 at 10 C, a very low capacity decay of 0.12% per cycle, and an impressive cycling stability of 877 mAh g−1 after 150 cycles at 1 C. As sulfur loading increases from 50 wt% to 77 wt%, high capacities of 970, 914, and 613 mAh g−1 are still available at current densities of 0.5, 1, and 5 C, respectively. Based on the total mass of packaged devices, gravimetric energy density of GSH@APC-S//Li cell is expected to be 400 Wh kg−1 at a power density of 10 000 W kg−1, matching the level of engine driven systems.

Gyorgy Marosi - One of the best experts on this subject based on the ideXlab platform.

  • solvent free melt electrospinning for preparation of fast dissolving drug delivery system and comparison with solvent based electrospun and melt extruded systems
    Journal of Pharmaceutical Sciences, 2013
    Co-Authors: Zsombor Kristof Nagy, Attlia Balogh, Gabor Dravavolgyi, James W Ferguson, Hajnalka Pataki, Balazs Vajna, Gyorgy Marosi
    Abstract:

    ABSTRACT The solvent-free melt electrospinning (MES) method was developed to prepare a drug delivery system with fast release of carvedilol (CAR), a drug with poor water solubility. To the authors knowledge, this is the first report for preparing drug-loaded melt electrospun fibers. Cationic methacrylate copolymer of Eudragit® E type was used as a fiber forming polymer matrix. For comparison, ethanol-based electrospinning and melt extrusion (EX) methods were used to produce samples that had the same composition as the melt electrospun system. According to the results of scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and Fourier transformed infrared spectrometry investigations, amorphous solid nanodispersions/solutions of CAR in Eudragit® E matrix were obtained in all cases with 20 m / m % drug content. In vitro drug release in acidic media from the extrudates was significantly faster (5 min) than that from crystalline CAR. Moreover, ultrafast drug release was achieved from the solvent-free melt and ethanol-based electrospun samples because of their Huge Surface Area and the soluble polymer matrix in the acidic media. These results demonstrate that solvent-free MES is a promising, novel technique for the production of drug delivery systems with enhanced dissolution because it can combine the advantages of EX (e.g., solvent-free, continuous process, and effective amorphization) and solvent-based electrospinning (Huge product Surface Area).

  • electrospun water soluble polymer mat for ultrafast release of donepezil hcl
    Express Polymer Letters, 2010
    Co-Authors: Zsombor Kristof Nagy, K Nyul, Istvan Wagner, Kolos Molnar, Gyorgy Marosi
    Abstract:

    Electrostatic spinning (Electrospinning, ES) was applied to prepare Donepezil HCl loaded nanofibers as a poten- tial orally dissolving dosage form. Electrospinning of water solutions of different polymers were performed in order to fab- ricate a consistent and removable web on the collector with ultra-fast dissolution in water based media. Poly(vinyl-alcohol) of low molecular weight was found to be the most appropriate for this purpose. Morphology of the prepared nanofibers was characterized by scanning electron microscope as a function of viscosity and drug content. Diameters of the fibers were between 100 and 300 nm with narrow distribution. In vitro drug release of the webs was immediate (less than 30 s) after immersion independently of their drug content owing to the formed Huge Surface Area, while cast films with the same com- positions and commercial tablets needed 30 min or more for complete dissolution. The developed technology for the prepa- ration of orally dissolving web (ODW) formulations is a promising way for producing effective and acceptable dosage forms for children, older people and patients with dysphagia.

Hongjie Peng - One of the best experts on this subject based on the ideXlab platform.

  • janus separator of polypropylene supported cellular graphene framework for sulfur cathodes with high utilization in lithium sulfur batteries
    Advanced Science, 2016
    Co-Authors: Hongjie Peng, Jiaqi Huang, Xinbing Cheng, Fei Wei, Daiwei Wang, Zhe Yuan, Qiang Zhang
    Abstract:

    Owing to the conversion chemistry of the sulfur cathode, the lithium–sulfur (Li–S) batteries exhibit high theoretical energy density. However, the intrinsic mobile redox centers during the sulfur/Li2S-to-lithium polysulfides solid-to-liquid phase transition induce low sulfur utilization and poor cycling life. Herein, the Janus separator of mesoporous cellular graphene framework (CGF)/polypropylene membrane to promote the utilization of sulfur cathode is introduced. The porous polypropylene membrane serves as an insulating substrate in contact with lithium anode while CGFs that possess high electrical conductivity of 100 S cm−1, a large mesopore volume of 3.1 cm3 g−1, and a Huge Surface Area of 2120 m2 g−1 are adhered on cathode side to reactivate the shuttling-back polysulfides and to preserve the ion channels. Therefore, the Li–S cell with the “two-face” CGF Janus separator exhibit a high initial capacity of 1109 mAh g−1 and superior capacity preserved upon 800 mAh g−1 after 250 cycles at 0.2 C, which is 40% higher on sulfur utilization efficiency than the corresponding results with routine polypropylene separators. There are significant improvements on capacity as well as electrochemical kinetics. A very high Areal capacity of 5.5 mAh cm−2 combined with high sulfur content of 80% and Areal loading amount of 5.3 mg cm−2 is achieved for such advanced configuration. The negative impact of shuttle mechanism on lowering the utilization of sulfur and overall energy density of a Li–S battery is well eliminated by applying CGF separators. Consequently, employing carbonaceous materials as Janus face of separators enlightens new opportunities for improving the utilization of active materials and energy density of devices that involve complex phase evolution and conversion electrochemistry.

  • nanoarchitectured graphene cnt porous carbon with extraordinary electrical conductivity and interconnected micro mesopores for lithium sulfur batteries
    Advanced Functional Materials, 2014
    Co-Authors: Hongjie Peng, Jiaqi Huang, Mengqiang Zhao, Qiang Zhang, Xinbing Cheng, Xinyan Liu, Weizhong Qian, Fei Wei
    Abstract:

    The sp2-hybridized nanocarbon (e.g., carbon nanotubes (CNTs) and graphene) exhibits extraordinary mechanical strength and electrical conductivity but limited external accessible Surface Area and a small amount of pores, while nanostructured porous carbon affords a Huge Surface Area and abundant pore structures but very poor electrical conductance. Herein the rational hybridization of the sp2 nanocarbon and nanostructured porous carbon into hierarchical all-carbon nanoarchitectures is demonstrated, with full inherited advantages of the component materials. The sp2 graphene/CNT interlinked networks give the composites good electrical conductivity and a robust framework, while the meso-/microporous carbon and the interlamellar compartment between the opposite graphene accommodate sulfur and polysulfides. The strong confinement induced by micro-/mesopores of all-carbon nanoarchitectures renders the transformation of S8 crystal into amorphous cyclo-S8 molecular clusters, restraining the shuttle phenomenon for high capacity retention of a lithium-sulfur cell. Therefore, the composite cathode with an ultrahigh specific capacity of 1121 mAh g−1 at 0.5 C, a favorable high-rate capability of 809 mAh g−1 at 10 C, a very low capacity decay of 0.12% per cycle, and an impressive cycling stability of 877 mAh g−1 after 150 cycles at 1 C. As sulfur loading increases from 50 wt% to 77 wt%, high capacities of 970, 914, and 613 mAh g−1 are still available at current densities of 0.5, 1, and 5 C, respectively. Based on the total mass of packaged devices, gravimetric energy density of GSH@APC-S//Li cell is expected to be 400 Wh kg−1 at a power density of 10 000 W kg−1, matching the level of engine driven systems.

Guozhong Cao - One of the best experts on this subject based on the ideXlab platform.

  • Developments in nanostructured cathode materials for high-performance lithium-ion batteries
    Advanced Materials, 2008
    Co-Authors: Ying Wang, Guozhong Cao
    Abstract:

    Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which Surface processes and transport kinetics play determining roles. This Review describes some recent developments in the synthesis and characterization of nanostructured cathode materials, including lithium transition metal oxides, vanadium oxides, manganese oxides, lithium phosphates, and various nanostructured composites. The major goal of this Review is to highlight some new progress in using these nanostructured materials as cathodes to develop lithium batteries with high energy density, high rate capability, and excellent cycling stability resulting from their Huge Surface Area, short distance for mass and charge transport, and freedom for volume change in nanostructured materials.