Nanofiber-Reinforced Composite Gel Enabling High Ionic Conductivity and Ultralong Cycle Life for Zn Ion Batteries.

Despite the impressive merits of gel electrolytes for aqueous Zn-ion batteries, it remains a significant challenge to design and develop the gel electrolyte with high ionic conductivity, excellent dimensional stability, and long cycle life. Herein, a composite electrolyte (PTP) with thermolastic polyurethane -poly(m-phenylene isophthalamide)  nanofiber-reinforced polyvinyl alcohol gel strategy is proposed for highly reversible Zn plating/stripping. Mechanically robust and ultrathin PTP contains functional groups for building ion migration channels and immobilizing water molecules, which accelerates Zn2+ migration and mitigates water-related side reactions. Thus, the Zn anodes exhibit excellent electrochemical performance involving high cycling stability (6500 h at 5 mA cm-2 , 5 mA h cm-2 ) and achieving an exceptional cumulative capacity of more than 16 000 mA h cm-2 . This enhancement is well maintained when combined with MnO2 cathode. This work provides a reasonable solution for stabilizing Zn anodes and also provides new ideas for the modification of nanofiber-reinforced gel electrolytes.

Customized Structure Design and Functional Mechanism Analysis of Carbon Spheres for Advanced Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are attracting much attention due to their high theoretical energy density and are considered to be the predominant competitors for next-generation energy storage systems. The practical commercial application of LSBs is mainly hindered by the severe "shuttle effect" of the lithium polysulfides (LiPSs) and the serious damage of lithium dendrites. Various carbon materials with different characteristics have played an important role in overcoming the above-mentioned problems. Carbon spheres (CSs) are extensively explored to enhance the performance of LSBs owing to their superior structures. The review presents the state-of-the-art advances of CSs for advanced high-energy LSBs, including their preparation strategies and applications in inhibiting the "shuttle effect" of the LiPSs and protecting lithium anodes. The unique restriction effect of CSs on LiPSs is explained from three working mechanisms: physical confinement, chemical interaction, and catalytic conversion. From the perspective of interfacial engineering and 3D structure designing, the protective effect of CSs on the lithium anode is also analyzed. Not only does this review article contain a summary of CSs in LSBs, but also future directions and prospects are discussed. The systematic discussions and suggested directions can enlighten thoughts in the reasonable design of CSs for LSBs in near future.

Flexible self-supporting inorganic nanofiber membrane-reinforced solid-state electrolyte for dendrite-free lithium metal batteries.

Compounding of suitable fillers with PEO-based polymers is the key to forming high-performance electrolytes with robust network structures and homogeneous Li+-transport channels. In this work, we innovatively and efficiently prepared Al2O3 nanofibers and deposited an aqueous dispersion of Al2O3 into a membrane via vacuum filtration to construct a nanofiber membrane with a three-dimensional (3D) network structure as the backbone of a PEO-based solid-state electrolyte. The supporting effect of the nanofiber network structure improved the mechanical properties of the reinforced composite solid-state electrolyte and its ability to inhibit the growth of Li dendrites. Meanwhile, interconnected nanofibers in the PEO-based electrolyte and the strong Lewis acid-base interactions between the chemical groups on the surface of the inorganic filler and the ionic species in the PEO matrix provided facilitated pathways for Li+ transport and regulated the uniform deposition of Li+. Moreover, the interaction between Al2O3 and lithium salts as well as the PEO polymer increased free Li+ concentration and maintained its stable electrochemical properties. Hence, assembled Li/Li symmetric cells achieved a cycle life of more than 2000 h. LFP/Li and NMC811/Li cells provided high discharge specific capacities of up to 146.9 mA h g-1 (0.5C and 50 °C) and 166.9 mA h g-1 (0.25C and 50 °C), respectively. The prepared flexible self-supporting 3D nanofiber network structure construction can provide a simple and efficient new strategy for the exploitation of high-performance solid-state electrolytes.

Fabrication of PS/PVDF-HFP Multi-Level Structured Micro/Nano Fiber Membranes by One-Step Electrospinning.

Recently, the multi-level interwoven structured micro/nano fiber membranes with coarse and fine overlaps have attracted lots of attention due to their advantages of high surface roughness, high porosity, good mechanical strength, etc., but their simple and direct preparation methods still need to be developed. Herein, the multi-level structured micro/nano fiber membranes were prepared novelly and directly by a one-step electrospinning technique based on the principle of micro-phase separation caused by polymer incompatibility using polystyrene (PS) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) as raw materials. It was found that different spinning fluid parameters and various spinning process parameters will have a significant impact on its morphology and structures. Under certain conditions (the concentration of spinning solution is 18 wt%, the mass ratio of PS to PVDF-HFP is 1:7, the spinning voltage is 30 kV, and the spinning receiving distance is 18 cm), the PS/PVDF-HFP membrane with optimal multi-level structured micro/nano fiber membranes could be obtained, which present an average pore size of 4.38 ± 0.10 µm, a porosity of 78.9 ± 3.5%, and a water contact angle of 145.84 ± 1.70°. The formation mechanism of micro/nano fiber interwoven structures was proposed through conductivity and viscosity tests. In addition, it was initially used as a separation membrane material in membrane distillation, and its performance was preliminarily explored. This paper provides a theoretical and experimental basis for the research and development of an efficient and feasible method for the preparation of multi-level micro/nano fiber membranes.

Preparing Biomass Carbon Fiber Derived from Waste Rabbit Hair as a Carrier of TiO2 for Photocatalytic Degradation of Methylene Blue.

In the past few years, biomass carbon materials have gained wide attention from many scholars as TiO2 carrier materials to improve photocatalytic activity due to their renewable, green, low-cost, and high-efficiency advantages. In this study, TiO2/carbonized waste rabbit fibers (TiO2/CRFs) nanocomposites with the hierarchical microporous/mesoporous structure were fabricated by a combination of carbonization, immersion, and calcination methods using tetrabutyl titanate as the titanium source and waste rabbit hair as the carbon source. The properties and catalytic activity of TiO2/CRFs composite were evaluated based on several characterization techniques and methylene blue (MB) photodegradation studies. The results showed that the degradation of MB by TiO2/CRFs could reach 98.1% after 80 min of solar irradiation. Moreover, TiO2/CRFs still maintained high photocatalytic activity after five cycles of degradation tests, exhibiting good stability and reusability. The improved photocatalytic performance of TiO2/CRFs materials is attributed to the natural carbon and nitrogen element doping of TiO2/CRFs and its morphology, which reduces the compounding of photogenerated electron-hole pairs and narrows the TiO2 band gap, while the multiple reflections of visible light in the pore channels enhance the visible light absorption of the materials. Furthermore, the large specific surface area provides abundant reaction sites for adsorbed reactants. This paper provides the experimental basis for the application of waste rabbit biomass carbon composites in photocatalytic degradation field.

Constructing Amino-Functionalized Flower-like Metal-Organic Framework Nanofibers in Sulfonated Poly(ether sulfone) Proton Exchange Membrane for Simultaneously Enhancing Interface Compatibility and Proton Conduction.

A novel flower-like MIL-53(Al)-NH2 nanofiber (MNF) was successfully constructed, in which the electro-blown spinning Al2O3 nanofibers were introduced as Al precursors to coordinate with ligand in hydrothermal reaction for the formation of MOFs nanofibers. By incorporating the functional and consecutive MNFs fillers in sulfonated poly(ether sulfone) (SPES) matrix, high-performance MNFs@SPES hybrid membranes were obtained. Specifically, the peak stress strength could be strengthened to 33.42 MPa and the proton conductivity was remarkably improved to 0.201 S cm-1 as MNFs content increased to 5 wt %, achieving a simultaneous improvement on proton conduction and membrane stability. The highly promoted performance could be ascribed to the synergy advantages of unique structure and amino modification of MNFs: (1) The flower-like nanofiber structure of MNFs with high surface area could be beneficial to construct long-range and compatible interfaces between MNFs and SPES matrix, leading to sufficient continuous proton pathways as well as strengthened stability for the hybrid membrane. (2) The hydrophilic MNFs rendered the hybrid membrane with sufficient water retention for proton transfer via Vehicle mechanism. (3) Functional -NH2 groups of MNFs and -SO3H groups of SPES were consecutively and tightly bonded via acid-base electrostatic interactions, which further accelerated the proton conduction via Grotthuss hopping mechanism and effectively suppressed the methanol penetration in the meanwhile for the MNFs@SPES hybrid membranes.

Waste spunlaced facial puff derived monolithic flexible carbon framework (WCF): an ultralow-cost, recyclable and eco-friendly sorbent for oils and organic solvents.

Due to the spunlaced effect, waste spunlaced facial puff has a high degree of fiber entanglement and an abundant three-dimensional (3D) network porous structure, which make it form a 3D carbon framework material more easily after carbonization. For the first time, the monolithic 3D carbon framework is synthesized from waste spunlaced facial puff (WCF) and used as the adsorbent for contaminants in water. The adsorption capacity of WCF for oils and organic reagents can be 34-137 times its own weight. Over five adsorption-harvesting cycles, the adsorption capacity of WCF to organic pollutants can recover up to 95% of its initial capacity. Moreover, WCF exhibits stable permeation flux and high separation efficiency in a water-heavy oil system, which is about 7714 L m-2 h-1 and higher than 99%, respectively. With a combination of waste spunlaced facial puff with monolithic 3D porous structure as a raw material, facile and green preparation process, low density, excellent hydrophobicity and lipophilicity, WCF as an adsorbent has great superiority in removal of organic pollutant solvents and environmental protection as well as other applications, such as energy storage materials, catalyst carriers, electric information, etc. Furthermore, this work would provide a new strategy for recovery use of waste spunlaced cotton materials.

Silver Nanoparticle-Doped 3D Porous Carbon Nanofibers as Separator Coating for Stable Lithium Metal Anodes.

The ever-increasing demand for electric devices and vehicles prompts the fast development of energy storage systems. Lithium metal is thought to be the most promising electrode for high-performance batteries. However, the growth of lithium dendrites impedes the industrial production of lithium metal batteries. Herein, an effective approach is proposed by coating a commercial separator with three-dimensional porous carbon fibers loaded with silver nanoparticles (Ag-PCNFs), which can be regarded as a subsidiary of the electrode to improve the cycling performance of lithium metal batteries. The porous structure with a high specific surface area endows the electrode with a high lithium-loading capacity. The silver nanoparticles provide the electrode pro-Li property and excellent electrical conductivity, which are beneficial for the electrochemical reaction and reduce the local current density to attain a dendrite-free electrode. Electrochemical cycling performance of symmetric Li-Li batteries shows that Ag-PCNF coating can hinder dendrite growth and enhance the cycling stability, indicating that Ag-PCNFs acting as host materials can effectively guide the deposition of Li and solve the dendrite problem.

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.

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.

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.