Quanxiang Li

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.

Capsular polypyrrole hollow nanofibers: an efficient recyclable adsorbent for hexavalent chromium removal

Capsular polypyrrole hollow nanofibers (PPy-HNFs) were fabricated via in situ polymerization of pyrrole on an organic–inorganic template, followed by acid etching. Their application in removing hexavalent chromium (Cr(VI)) from aqueous solution was then investigated. The morphologies of the capsular PPy-HNFs were studied by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which showed that the PPy-HNFs had a capsular structure in the walls of hollow nanofibers. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) data confirmed the adsorption of Cr on capsular PPy-HNFs. The adsorption capacity increased with reduced pH of the initial solution and the adsorption process can be described using the pseudo-second-order model. These capsular PPy-HNFs showed a high Cr(VI) adsorption capacity up to 839.3 mg g−1. This adsorption capacity was largely retained even after five adsorption/desorption cycles. Electrostatic attraction between Cr and PPy-HNFs was studied using a proposed adsorption mechanism. The capsular PPy-HNFs formed a flexible membrane, which allowed easy handling during application. This study has demonstrated the possibilities of using this capsular PPy-HNF membrane for heavy metal removal from aqueous solution.

A new method for preparing alumina nanofibers by electrospinning technology

A new method for synthesizing alumina (Al2O3) nanofibers through the electrospinning method was reported. The spinning solutions of anhydrous aluminium chloride/polyvinylpyrrolidone (AlCl3/PVP), wh...A new method for synthesizing alumina (Al2O3) nanofibers through the electrospinning method was reported. The spinning solutions of anhydrous aluminium chloride/polyvinylpyrrolidone (AlCl3/PVP), which were prepared by the sol-gel process of the mixture of AlCl3, PVP, ethanol and redistilled water, were electrospun to form AlCl3/PVP organic-inorganic hybrid fibers. Alumina nanofibers with average diameters of 100—800 nm were obtained by calcinations of the as-prepared fibers. The fibers were characterized by SEM, TG-DTA, FTIR, XPS and XRD. The results showed that with the increase of the concentration of spinning solution, the diameter of fibers also increased, and that the diameter of fibers decreased with the increase of the applied voltage and calcination temperature. The uncrystalline Al2O3, γ-Al 2O3 and α-Al2O3 were obtained after calcinations of about 5 h at 450, 900 and 1100°C, respectively.

Hydrophilic PAN based carbon nanofibres with improved graphitic structure and enhanced mechanical performance using ethylenediamine functionalized graphene

Polyacrylonitrile (PAN) reinforced with nano-carbons such as graphene (Gr) and carbon nanotubes (CNTs) provides great opportunity for the development of low-cost and high-performance carbon materials. However, the poor dispersion and weak interaction between the carbon nanofillers and the surrounding PAN matrix prevent the final carbonized materials from reaching their full potential. Herein, we demonstrate a chemical approach using ethylenediamine (EDA) acting as a linker between graphene nanoplatelets and PAN for improved mechanical performance. The as-prepared CNFs exhibit a higher carbon yield and tensile modulus as well as improved graphitic structure compared to pristine PAN and PAN/Gr nanofibres. Furthermore, EDA can act as a N source for N-doping during the carbonization, enabling CNFs with hydrophilicity performance.

Investigation of chitosan adsorption onto cotton fabric with atmospheric helium/oxygen plasma pre-treatment

In this study, the effects of helium or a helium/oxygen mixture atmospheric pressure plasma treatment on the adsorption of chitosan onto the cotton fabric were investigated. Fabrics were treated with plasma prior to a chitosan finishing process, whereby fabrics were surface coated using a pad/dry/cure method. Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, surface energy analyser and contact angle measurements were used to investigate the changes on the cotton surface. Furthermore, antimicrobial activity of the cotton fabric was evaluated. The results showed that plasma pre-treatment enhanced the chitosan adsorption to the cotton surface through physical bonding and there was weak evidence of chemical bonding interactions. A combination of plasma and chitosan treatment did not show any significant differences on the antimicrobial properties compared to chitosan only treated fabric. Plasma treatment changed the fibres physically and enhanced the surface energy and thickness of chitosan distributed on the fibres.

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.