Search

Graphical Abstract:

The conventional fabrication of bulk van der Waals (vdW) materials requires a temperature above 1,000 °C to sinter from the corresponding particulates. Here we report the near-room-temperature densification (for example, ∼45 °C for 10 min) of two-dimensional nanosheets to form strong bulk materials with a porosity of <0.1%, which are mechanically stronger than the conventionally made ones. The mechanistic study shows that the water-mediated activation of van der Waals interactions accounts for the strong and dense bulk materials. Initially, water adsorbed on two-dimensional nanosheets lubricates and promotes alignment. The subsequent extrusion closes the gaps between the aligned nanosheets and densifies them into strong bulk materials. Water extrusion also generates stresses that increase with moulding temperature, and too high a temperature causes intersheet misalignment; therefore, a near-room-temperature moulding process is favoured. This technique provides an energy-efficient alternative to design a wide range of dense bulk van der Waals materials with tailored compositions and properties.

This review elaborately summarized the recent progress of solid-state composite cathodes, including interface issues, material design, preparation methods and characterization techniques, which provides valuable experience for understanding and engineering composite cathode of all-solid-state lithium batteries.

Dietary fiber is an important component of healthy eating patterns. Although American ginseng (Panax quiquefoliumL.) is often used to improve body immunity, less attention has been paid to American ginseng dietary fiber (AGDF) in this regard. The aim of this study was to investigate the protective effect of AGDF on intestinal mucosal barrier injury induced by cyclophosphamide (CTX) in immunosuppressed mice and the underlying mechanism. The results showed that AGDF could increase immune organ index and enhance immunity of immunosuppressed mice, such as DTH response, lymphocyte transformation and proliferation and NK effector cell activity. At the same time, AGDF could restore the proportion of CD4+/CD8+T lymphocytes induced by CTX to different extents, and promote the secretion of immunoglobulin IgG. More importantly, AGDF could up-regulate the contents of TNF-α, IFN-γ, IL-6 and IL-1β in serum and intestine of immunosuppressed mice, promote the secretion of cytokines and regulate the homeostasis balance between Th1/Th2 cytokines. It also upregulated the expression of tight junction proteins occludin, claudin-1 and ZO-1, and alleviated the degree of CTX-induced damage to the intestinal mucosal barrier. Meanwhile, AGDF could reduce intestinal epithelial cell apoptosis by activating TLR4/NF-κB signaling pathway, improving the phosphorylation of JNK and p38 signaling molecules, which may be the potential mechanism by which AGDF ameliorates intestinal mucosal injury in immunosuppressed mice. Therefore, AGDF may be used as a dietary supplement to prevent and treat intestinal mucosal barrier injury caused by CTX.

Sodium vanadate NaV6O15(NVO) is one of the most promising cathode materials for sodium-ion batteries because of its low cost and high theoretical capacity. Nevertheless, NVO suffers from fast capacity fading and poor rate capability. Herein, a novel free-standing NVO/multiwalled carbon nanotube (MWCNT) composite film cathode was synthesized and designed by a simple hydrothermal method followed by a dispersion technique with high safety and low cost. The kinetics analysis based on cyclic voltammetry measurements reveals that the intimate integration of the MWCNT 3D porous conductive network with the 3D pillaring tunnel structure of NVO nanorods enhances the Na+intercalation pseudocapacitive behavior, thus leading to exceptional rate capability and long lifespan. Furthermore, the NVO/MWCNT composite exhibits excellent structural stability during the charge/discharge process. With these benefits, the composite delivers a high discharge capacity of 217.2 mA h g–1at 0.1 A g–1in a potential region of 1.5–4.0 V. It demonstrates a superior rate capability of 123.7 mA h g–1at 10 A g–1. More encouragingly, it displays long lifespan; impressively, 96% of the initial capacity is retained at 5 A g–1for over 500 cycles. Our work presents a promising strategy for developing electrode materials with a high rate capability and a long cycle life.

With the emergence and development of wearable devices, the novel energy storage systems with flexible feature and high energy density are urgently needed. As we all know, for next generation high energy-storage systems, lithium-sulfur (Li-S) batteries with a high theoretical capacity are regarded as one of the most promising candidates. In addition, the flexible Li-S batteries have received more and more attention. The determined factor in the flexible Li-S batteries is how to design the foldable electrodes including both anode and cathode. As for the flexible sulfur cathode, it could be obtained by integrating the electroactive sulfur with a flexible substrate, generally. In recent years, the flexible cathode of Li-S batteries have made considerable progress, however there are also many huge challenges needing to overcome, such as low content of sulfur, fast decrease of capacity and short cycle life. In this paper, the current develop status of flexible cathodes of Li-S batteries have been summarized, and the future trend also be pointed out. [ABSTRACT FROM AUTHOR]

Solid polymer electrolytes (SPEs) with the advantages of high safety, low volatility, and the ability to suppress Li dendrites are highly desirable to be used in next generation high-safety and high-energy lithium-ion batteries. The exploration of SPEs with superior comprehensive properties has received extensive attention for high-performance all-solid-state batteries (ASSBs). Herein, a sandwich-like nanofibrous membrane-reinforced poly-caprolaclone diol and trimethyl phosphate (TMP) composite polymer electrolyte (CPE) has been designed by a facile “solvent-free” solution-casting method. Specifically, the flame-retardant TMP is employed as a plasticizer, which can improve the ionic conductivity effectively. The as-prepared solid electrolyte exhibits superior comprehensive performance in terms of high ionic conductivity, wide electrochemical window, good compatibility with lithium metal, and superior thermal stability. Furthermore, the assembled Li//LiFePO4ASSBs with this solid CPE show outstanding cycling stability and high average discharge capacity at room temperature (30 °C). Undoubtedly, our study provides a new facile method and a qualified solid electrolyte material for next generation high-performance ASSBs.

For solving the drawbacks of low conductivity and the shuttle effect in a sulfur cathode, various nonpolar carbon and polar metal compounds with strong chemical absorption ability are applied as sulfur host materials for lithium–sulfur (Li–S) batteries. Nevertheless, previous research simply attributed the performance improvement of sulfur cathodes to the chemical adsorption ability of polar metal compounds toward lithium polysulfides (LPS), while a deep understanding of the enhanced electrochemical performance in these various sulfur hosts, especially at the molecular levels, is still unclear. Herein, for a mechanistic understanding of superior metal phosphide host in Li–S battery chemistry, an integrated phosphide-based host of CF/FeP@C (carbon cloth with grown FeP@C nanotube arrays) is chosen as the model, and this binder-free cathode can exclude interference from the binder and conductive additives. With a systematic electrochemical investigation of the loading sulfur in such oxide- and phosphide-based hosts (CF/Fe3O4@C and CF/FeP@C), it is found that CF/FeP@C@S shows much superior Li–S performances. The greatly enhanced performance of CF/FeP@C@S suggests that FeP can well suppress the shuttle effect of LPS and accelerate their transformation during the charge–discharge process. The first-principles calculations reveal the performance variations of Fe3O4and FeP in Li–S batteries mainly because the shifts of the p band of the FeP could accelerate the interfacial electronics transfer dynamics by increasing the electronic concentration in the Fermi level of adsorbed Li2S4. The current work sheds light on the promising design of superior Li–S batteries from both theoretical and experimental aspects.

To solve the serious problems (the agglomeration of nano-Fe0, dissolution of polysulfide, and low electronic conductivity of Li2S) of earth-abundant pyrite (FeS2) cathodes for lithium batteries, a simple in situencapsulation and transformation route has been successfully developed to synthesis pitaya-structured porous carbon embedded with FeS2nanoparticles. Due to such a hierarchical architecture design, this cathode of pitaya-structured FeS2@C can effectively avoid the serious agglomeration and coarsening of small Fe nanoparticles, reduce the dissolution of polysulfide, and provide superior kinetics toward lithium storage, resulting in enhanced reversibility and rate capability. Cycling in the voltage region of 1.0–3.0 V at 0.3 A g–1, the current conversion-based FeS2@C cathode displays a high and stable energy density (about 1100 Wh kg–1), ultrahigh rate capability (a reversible capability of 660, 609, 554, 499, 449, and 400 mA h g–1at 0.2, 0.5, 1.0, 2.0, 5.0, and 10 A g–1, respectively), and stable cycling performance.

Accelerated solvent extraction (ASE) was applied to the extraction of saikosaponin a, saikosaponin c and saikosaponin d from the roots of Bupleurum falcatum. Main extraction parameters such as the extraction solvents, extraction temperature and static extraction time were investigated and optimized. The optimized procedure employed 70% methanol as extraction solvent, 120°C of extraction temperature, 10 min of static extraction time, 60% of flush volume and the extraction recoveries of the three compounds were near to 100% with one extraction cycle. The extracted samples were analyzed by HPLC with UV detector. The HPLC conditions were as follows: Hypersil ODS2 (4.6 mm×250 mm, 5 μm) column, acetonitrile and water as mobile phase, flow rate of 1.0 mL/min, UV detection wavelength of 204 nm and injection volume of 20 μL. Compared with the traditional methods including heat‐reflux extraction and ultrasonic‐assisted extraction, the proposed ASE method was more efficient and faster to be operated. The results indicated that ASE was an alternative method for extracting saikosaponins from the roots of B. falcatum.

Supercritical fluid extraction (SFE) was used to extract saikosaponins a, c and d from the root of Bupleurum falcatum. An orthogonal array design L9(3)4was employed as a chemometric method for the optimization of the SFE conditions. The effects of four factors including pressure (30–40 MPa), temperature (40–50°C), ethanol concentration (60–100%) and time (2.5–3.5 h) on the yields of saikosaponins were investigated by a preparative SFE system in the SFE mode. Under the optimized conditions, namely 35 MPa of pressure, 45°C of temperature, 80% of ethanol concentration and 3.0 h of time, the yields of saikosaponin c, saikosaponin a, saikosaponin d, total saikosaponins and SFE extract were 0.16, 0.12, 0.96, 1.24 and 16.48 mg/g, respectively. Determinations of the saikosaponins were performed by HPLC.