The potassium-ion battery (PIB) has been recognized as a promising low-cost and high-energy battery; however, it suffers from a relatively low capacity and inferior cycling performance compared with current electrode materials. Herein, we report an effective interface engineering strategy to prepare metal−organic framework (MOF) nanocrystals tightly encapsulated by reduced graphene oxide (rGO) via strong chemical interaction as a free-standing anode for PIB. Based on experimental analysis and theoretical calculations, we systematically investigated the effect of the chemical-bonded interface between MOF nanocrystals and conductive rGO and revealed that the strong chemical interface can substantially enhance the adsorption energy and ion transport kinetics of the potassium ion within the MOF nanocrystals compared to the physical mixture of MOF and rGO with almost the same microscopic morphologies. As a result, such an MOF-rGO hybrid with strong interfacial chemical couplings delivered an ultrahigh reversible capacity of 422 mAh g −1 at 0.1 A g −1 , superior rate performance (202 mAh g −1 at 5 A g −1 ), and outstanding long-term cycling performance (an ultralow decay rate of 0.013% per cycle after 2000 cycles at 2 A g −1 ), which are not only significantly better than those of the physical mixture of MOF/rGO but also among the best for anodes for PIB reported thus far.

By introducing lithiophilic groups and electrochemically stable quinolyl aromatic ring linkages, we prepared covalent organic frameworks (COFs) exhibiting a large band gap with an ultralow HOMO value (−6.2 eV under vacuum) and oxidative stability up to 5.6 V (versus Li+/Li) as solid‐state electrolytes (SSEs). The obtained flexible COF SSE thin films showed a holistically oriented arrangement along the (001) facet with remarkable ionic conductivity up to 1.5×10−4 S cm−1 at 60 °C and excellent mechanical strength with a high Young's modulus of 10.5 GPa. Molecular dynamic simulations showed that lithium ions are transmitted in this COF SSE by directional hopping paths with fast drift velocity. The COF SSE film was used to assemble all‐solid‐state lithium metal batteries with nickel‐rich cathodes (NMC811). The batteries demonstrated stable cycling performance over 400 cycles, high coulombic efficiency (>99 %), and could also withstand abuse tests, such as folding.

A two-phase flow model is developed to simulate the fiber motion in the nozzle of an air-jet spinning machine. The computational results coincide with the images captured by high-speed photography. Three parameters, the first nozzle pressure, the jet orifice angle, and fiber flexural rigidity, are discussed in terms of their influences on wrapper formation and, consequently, on yarn structure and yarn quality. The predictions of yarn tensile properties tally with the experimental results reported by several researchers.Air-jet spinning is becoming an important system in short staple spinning because it is advantageous for processing speeds, costs, and ability to spin fine counts. Researchers have been paying much attention to this spinning method since the first single air-jet system was developed by Du Pont in 1963. Studies have focused on three subjects: the principle of yam formation, the structure of the yarn, and the effects of various parameters on yarn quality. Regarding the principle of yarn formation, there have been two points of view [1, 7, 18], and we maintain the following viewpoint: The edge fibers wrap the false twisted core in the opposite direction while passing through the first nozzle, and the second nozzle inserts the false twist into the fiber strand coming out of the front roller. Untwisting downstream of the second nozzle produces considerably more twist in these wrapper fibers, thus giving the yarn its strength. Investigations of yarn structure have been reported, and several classification systems have been developed [4, 7, 10]. The effects of the parameters of process conditions, nozzle design, and fiber properties on yarn quality have been studied using experimental techniques [ 1,4,7,10,[13][14][15]19]. The principle of yam formation and the investigation of the yarn structure indicate that the formation of wrapper fibers in the first nozzle plays a dominant role in this technology. Krause and Soliman theoretically analyzed the wrapping twist in a single-jet air system [8]. In this work, we use the numerical method to simulate fiber motion in the nozzle of an air-jet spinning machine, showing the process that causes an edge fiber (free fiber) to wrap while it is being delivered by the air flow in the nozzle. Fiber Motion Model.

Constructing heterostructures of covalent organic frameworks (COFs) and metal organic frameworks (MOFs) have gained great attention for various applications due to their well-defined skeletons, ordered porosity and designable functions. Herein,...

As a promising graphene analogue, two-dimensional (2D) polymer nanosheets with unique 2D features, diversified topological structures and as well as tunable electronic properties, have received extensive attention in recent years. Here in this review, we summarized the recent research progress in the preparation methods of 2D polymer nanosheets, mainly including interfacial polymerization and solution polymerization. We also discussed the recent research advancements of 2D polymer nanosheets in the fields of energy storage and conversion applications, such as batteries, supercapacitors, electrocatalysis and photocatalysis. Finally, on the basis of their current development, we put forward the existing challenges and some personal perspectives.