Yuelei Pan

A fast synthesis of silica aerogel powders-based on water glass via ambient drying

In this paper, we report the experimental results of the silica aerogel powders prepared by water glass and ambient pressure drying within 4 h. Water glass was hydrolyzed in water using HCl as the acid catalyst. In order to reduce the consumption of modifier and preparation period, the new technological process of mechanical crushing and filtration was introduced and solvent exchange/surface modification process can be rapidly carried out in this way. Furthermore, we utilized water glass instead of NH3·H2O as base catalyst. To some extent, it avoided impurities into the aerogels. Base concentration proved to have a very important influence on the physical and chemical properties of aerogels. As a result, when the dilution ratio of water glass as base catalyst is 3, aerogels with well-developed mesoporous structure (mean pore size of ~ 20 nm) and super hydrophobicity (contact angle of ~ 162°) can be obtained.Graphical Abstract

CoS2 Nanoparticles Wrapping on Flexible Freestanding Multichannel Carbon Nanofibers with High Performance for Na-Ion Batteries

Exploration for stable and high-powered electrode materials is significant due to the growing demand for energy storage and also challengeable to the development and application of Na-ion batteries (NIBs). Among all promising electrode materials for NIBs, transition-mental sulfides have been identified as potential candidates owing to their distinct physics-chemistry characteristics. In this work, CoS2 nanomaterials anchored into multichannel carbon nanofibers (MCNFs), synthesized via a facile solvothermal method with a sulfidation process, are studied as flexible free-standing electrode materials for NIBs. CoS2 nanoparticles uniformly distributed in the vertical and horizontal multichannel networks. Such nanoarchitecture can not only support space for volume expansion of CoS2 during discharge/charge process, but also facilitate ion/electron transport along the interfaces. In particular, the CoS2@MCNF electrode delivers an impressively high specific capacity (537.5 mAh g-1 at 0.1 A g-1), extraordinarily long-term cycling stability (315.7 mAh g-1 at at 1 A g-1 after 1000 cycles), and excellent rate capacity (537.5 mAh g-1 at 0.1 A g-1 and 201.9 mAh g-1 at 10 A g-1) for sodium storage. Free-standing CoS2@MCNF composites with mechanical flexibility provide a promising electrode material for high-powered NIBs and flexible cells.

Facile construction of the aerogel/geopolymer composite with ultra-low thermal conductivity and high mechanical performance

In this work, we have successfully prepared a lightweight, highly hydrophobic and superb thermal insulating aerogel/geopolymer composite by a sol–gel immersion method. After silica aerogel was impregnated, the composite exhibited nano-porous structures. Moreover, scanning electron microscopy observations revealed that the aerogel particles were tightly anchored on the geopolymer surface. With several excellent properties (bulk density: 306.5 g cm−3, thermal conductivity: 0.0480 W m−1 K−1 and maximum compressive strength: 0.79 MPa) the as-prepared composite shows great potential to be applied in the thermal insulation field.

Nanoflower-Like N-Doped C/CoS2 as High-Performance Anode Materials for Na-Ion Batteries

Novel nanoflower-like N-doped C/CoS2 spheres assembled from 2D wrinkled CoS2 nanosheets were synthesized through a facile one-pot solvothermal method followed by sulfurization. Ascribed to the optimized 3D nanostructure and rational surface engineering, the unique hierarchical structure of the nanoflower-like C/CoS2 composites showed an excellent sodium ion storage capacity accompanied by high specific capacity, superior rate performance and long-term cycling stability. Specifically, the conductive interconnected wrinkled nanosheets create a number of mesoporous structures and thus can greatly release the mechanical stress caused by Na+ insertion/extraction. Besides, it was observed from the experiments that many extra defect vacancies and Na+ storage sites are introduced by the nitrogen doping process. It was also observed that the crosslinked 2D nanosheets can effectively reduce the diffusion lengths of sodium ions and electrons, resulting in an outstanding rate performance (>700 mA h g-1 at 1 A g-1 and 458 mA h g-1 at even 10 A g-1) and extraordinary cycling stability (698 mA h g-1 at 1 A g-1 after 500 cycles). The results provide a facile approach to fabricate promising anode materials for high-performance sodium-ion batteries (SIBs).

Double-morphology CoS2 Anchored on N-doped Multichannel Carbon Nanofibers as High-Performance Anode Materials for Na-Ion Batteries

Na-ion batteries (NIBs) have attracted increasing attention given the fact that sodium is relatively more plentiful and affordable than lithium for sustainable and large-scale energy storage systems. However, the shortage of electrode materials with outstanding comprehensive properties has limited the practical implementations of NIBs. Among all the discovered anode materials, transition-metal sulfide has been proven as one of the most competitive and promising ones due to its excellent redox reversibility and relatively high theoretical capacity. In this study, double-morphology N-doped CoS2/multichannel carbon nanofibers composites (CoS2/MCNFs) are precisely designed, which overcome common issues such as the poor cycling life and inferior rate performance of CoS2 electrodes. The conductive 3D interconnected multichannel nanostructure of CoS2/MCNFs provides efficient buffer zones for the release of mechanical stresses from Na+ ions intercalation/deintercalation. The synergy of the diverse structural features enables a robust frame and a rapid electrochemical reaction in CoS2/MCNFs anode, resulting in an impressive long-term cycling life of 900 cycles with a capacity of 620 mAh g-1 at 1 A g-1 (86.4% theoretical capacity) and a surprisingly high-power output. The proposed design in this study provides a rational and novel thought for fabricating electrode materials.