Nanping Deng

A review of recent developments in rechargeable lithium–sulfur batteries

The research and development of advanced energy-storage systems must meet a large number of requirements, including high energy density, natural abundance of the raw material, low cost and environmental friendliness, and particularly reasonable safety. As the demands of high-performance batteries are continuously increasing, with large-scale energy storage systems and electric mobility equipment, lithium-sulfur batteries have become an attractive candidate for the new generation of high-performance batteries due to their high theoretical capacity (1675 mA h g-1) and energy density (2600 Wh kg-1). However, rapid capacity attenuation with poor cycle and rate performances make the batteries far from ideal with respect to real commercial applications. Outstanding breakthroughs and achievements have been made to alleviate these problems in the past ten years. This paper presents an overview of recent advances in lithium-sulfur battery research. We cover the research and development to date on various components of lithium-sulfur batteries, including cathodes, binders, separators, electrolytes, anodes, collectors, and some novel cell configurations. The current trends in materials selection for batteries are reviewed and various choices of cathode, binder, electrolyte, separator, anode, and collector materials are discussed. The current challenges associated with the use of batteries and their materials selection are listed and future perspectives for this class of battery are also discussed.

Fabrication of a polyvinylidene fluoride tree-like nanofiber web for ultra high performance air filtration

A novel polyvinylidene fluoride (PVDF) tree-like nanofiber web was successfully fabricated via one-step electrospinning. The effect of the tree-like structure on the pore size distribution and specific surface area were measured, and the filtration properties of the tree-like nanofiber webs with different basis weights were investigated. The results showed that the tree-like structure significantly decreased the pore size and narrowed the range of pore size distribution, and dramatically enhanced the specific surface area. In comparison with common PVDF nanofiber webs, the tree-like nanofiber webs exhibited excellent filtration performance. The filtration efficiency of the tree-like nanofiber webs with the basis weight of 1 g m−2 to 0.26 μm NaCl particles was 99.999% and the pressure drop was only 124.2 Pa which was comparable to ultra low penetration air filters (ULPA). The tree-like nanofiber webs will be widely used in the field of high efficiency and precision filter materials and medical protective materials.

Preparation and characterization of tree-like cellulose nanofiber membranes via the electrospinning method

A novel tree-like cellulose nanofiber membrane was controllably fabricated via the electrospinning method by adding certain amount of tetra butyl ammonium chloride (TBAC) into the cellulose acetate solution followed by a deacetylation treatment process. The morphological structure, material structure and air filtration performance of both the cellulose and the cellulose acetate tree-like nanofiber membranes were characterized. Water contact angles, mechanical properties, and air filtration properties were also evaluated. The air filtration efficiency of cellulose acetate tree-like nanofiber membrane can reached 99.58%, and the eventually cellulose tree-like membrane still maintain 98.37%. The eventual cellulose tree-like nanofiber membranes exhibited small pore size, excellent hydrophilicity, good solvent resistance and preferable mechanical property. The small average pore size caused by the tree-like structure and the strong resistance to organic solvent can make it a potential candidate for the membrane separation.

Electrospun SiO2/PMIA nanofiber membranes with higher ionic conductivity for high temperature resistance lithium-ion batteries

The nanofiber membrane prepared by electrospinning has been widely applied in lithium-ion batteries. A powerful strategy for designing, fabricating and evaluating Poly-m-phenylene isophthalamide (PMIA) nanofiber membrane with SiO2 nanoparticles was developed by electrospinning in this paper. The morphology, crystallinity, thermal shrinkage, porosity and electrolyte uptake, and electrochemical performance of the SiO2/PMIA nanofiber membranes were investigated. It was demonstrated that the nanofiber membrane with 6 wt% SiO2 possessed notable properties, such as better thermal stability, higher porosity and electrolyte uptake, resulting in higher ionic conductivity (3.23×10-3 S·cm-1) when compared with pure PMIA nanofiber membrane. Significantly, the SiO2/PMIA nanofiber membrane based Li/LiCoO2 cell exhibited more excellent cycling stability with capacity retention of 95 % after 50 cycles. The results indicated that the SiO2-doped PMIA nanofiber membranes had a potential application as separator in high temperature resistance lithium-ion batteries.

CeF3-Doped Porous Carbon Nanofibers as Sulfur Immobilizers in Cathode Material for High-Performance Lithium–Sulfur Batteries

In this study, the CeF3-doped porous carbon nanofibers (PCNFs), prepared via electroblown spinning technique and carbonization process, are used as sulfur immobilizers in cathodes for lithium-sulfur (Li-S) batteries for the first time. The cathode composed of CeF3-doped PCNFs, carbon nanotubes (CNTs), and S is successfully prepared through the ball-milling and heating method. The formed porous structure in the PCNFs and CNTs facilitates the construction of highly electrically conductive pathways and effectively alleviates volume changes, which can maintain the stability of the cathode structure and make them in close contact between the electrodes. Meanwhile, the intermediate polysulfide dissolved and lost in the electrolyte can also be suppressed because of the hierarchical porous carbon nanofibers and CeF3. The Li-S battery using the cathode can display excellent electrochemical properties and stable capacity retention, presenting an initial discharge capacity of 1395.0 mAh g-1 and retaining a capacity of 901.2 mAh g-1 after 500 cycles at 0.5C. During the rate capability tests of battery, the discharge capacity of Li-S battery with the electrode slowed down from the discharge capacity of 1284.6 mAh g-1 at 0.5C to 1038.6 mAh g-1 at 1C and 819.3 mAh g-1 at 2C, respectively. It is noteworthy that the battery can still endow an outstanding discharge capacity of 1269.73 mAh g-1 with a high retention of 99.2% when the current density returns to 0.5C.

Designing waterproof breathable material with moisture unidirectional transport characteristics based on a TPU/TBAC tree-like and TPU nanofiber double-layer membrane fabricated by electrospinning

In this study, a thermoplastic polyurethane (TPU) tree-like nanofiber membrane was fabricated via one-step electrospinning by adding a small amount of tetrabutylammonium chloride (TBAC). On the basis of the “push and pull” effect, double-layer membranes composed of pure TPU nanofiber membranes (hydrophobic) and TPU/TBAC tree-like nanofiber membranes (hydrophilic) were prepared by the direct electrospinning compounding method. The double-layer membranes were used as waterproof breathable materials with moisture unidirectional transport properties and good shielding properties. The water resistance, mechanical, waterproof, moisture permeability, air permeability, air filtration and moisture unidirectional transport performances of the double-layer membranes were tested. The results showed that the double-layer TPU membranes displayed good performances compared with the existing products on the market; they provide a new approach for the development of waterproof breathable materials.

Electro-blown spun PS/PAN fibrous membrane for highly efficient oil/water separation

The preparation of high performance separation membrane is the key technology for developing efficient oil/water separation system. In this paper, hydrophilic/oleophilic Polystyrene (PS)/Polyacrylonitrile (PAN) bi-component membranes were prepared via electro-blown spinning (EBS) technique and exhibited extremely high oil flux. The addition of PAN component significantly enhanced the tensile strength of the PS based fibrous membranes and PS/PAN membrane with the weight ratio of 5:3 achieved a tensile strength of 2.1 MPa which was 3 times higher than pure PS membrane. The PS/PAN membranes demonstrated a high light oil flux up to 18000 l·m-2·h-1 and could remain the oil flux recovery ratio of 94.09 % after 10 cycles. The as-prepared membranes exhibited the superior oil/water separation performance with the separation efficiency higher than 99.5 % and have a great potential to deal with the oily waste water in the near future.

Fabrication and catalytic behavior of hierarchically-structured nylon 6 nanofiber membrane decorated with silver nanoparticles

A hierarchically-structured nylon 6 (PA6) nanofiber membrane decorated with silver nanoparticles (Ag NPs) was fabricated by electrospinning and impregnation methods. The as-fabricated hierar-chically-structured Ag/PA6 nanofiber membrane (HS-Ag/PA6 NM) exhibits a morphology in which Ag NPs are deposited on the surfaces of both thick fibers and thin fibers. The content and size of the Ag NPs can be controlled by varying the concentration of the silver colloid solution. Compared with the non-hierarchically-structured Ag/PA6 nanofiber membrane, HS-Ag/PA6 NM has a higher spe-cific surface area and exhibits a higher degradation rate for methylene blue of 81.8%-98.1% within 2 h. HS-Ag/PA6 NM can be easily recycled and exhibits good reusability. It retains a degradation rate for methylene blue of 83.5% after five consecutive cycles. The hierarchically-structured nano-fiber membrane is therefore a potential nanocatalyst.

Preparation and characterization of crosslinked electrospun pullulan nanofiber membrane as a potential for biomaterials

Abstract Pullulan nanofiber membrane (Pull-NM) was prepared by electrospinning method and its stability in the water was improved by a chemical crosslinking with mixed solution of ethylene glycol diglycidyl ether (EGDE) and ethanol absolute as crosslinking agent. The effect of crosslinked pullulan nanofiber membrane (C-l-Pull-NM) with different process conditions was studied and the excellent crosslinking reaction condition is proved to be 1:70 (EGDE: ethanol absolute) for 24 h. The analytical methods, including SEM, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and differential scanning calorimetry, were used to study morphology, structure, and thermal performance of the nanofiber membrane. In addition, the swelling behavior and tensile were also discussed. The results showed that the water resistance of crosslinked nanofiber membrane had a significant improvement. Furthermore, the maximum water absorption and the strength were reached to about 520 and 192.7%, respectively.

Method of Structure Design and Heat Treatment of an Integrated Consolidation Sensor and Embedded Temperature Sensing Fabric

In order to solve the problem of temperature sensors easily slipping and improve the precision of temperature measurement in temperature sensing fabric, a specially designed fabric was developed. In this paper, the fabric comprised plain and multi-layered fabric. Sensors were embedded into the multi-layered fabric. The multi-layered fabric was treated by partial heat treatment to make the temperature sensors be fixed to the fabric. The temperature sensing fabrics were measured before and after the partial heat treatment. The results showed that during the heat treatment, the number of fabric layers and fabric organization had an effect on temperature measurement, and the values measured after partial heat treatment were closer to the true value than without treatment. In addition, with an increase in the number of fabric layesr, the values measured were closer to the real value. And the measurement results were closer to the true value when the multi-layered fabric’s organizational structure was plain.