No abstract

Flexible energy storage electronics have gained increasing attention in recent years, but the simultaneous acquiring of high volumetric and high areal capacities as well as excellent flexibility in order to truly implement wearable and portable electronics in practice remains challenging. Here, a conductive and highly deformable freestanding all‐pseudocapacitive paper electrode (Ti3C2Tx/MnO2 NWs) is fabricated by solution processing of hybrid inks based on Ti3C2Tx MXene and ultralong MnO2 nanowires. The resulting Ti3C2Tx/MnO2 NWs hybrid paper manifests a remarkable areal capacitance of up to 205 mF cm−2 and outstanding volumetric capacitance of 1025 F cm−3. Both the values are highly comparable with, or in most cases much higher than those of previously reported MXene‐based flexible electrodes. The excellent energy storage performance is well maintained with a capacitance retention of 98.38% during 10 000 charge–discharge cycles. In addition, the flexible supercapacitor demonstrates excellent flexibility and electrochemical stability during repeated mechanical bendings of up to 120°, suggesting great potentials for the applications in future flexible and portable electronics.

Inspired by the remarkable adhesion of mussel, dopamine, a mimicking adhesive molecule, has been widely used for surface modification of various materials ranging from organic to inorganic. However, dopamine and its derivatives are expensive which impede their application in large scale. Herein, we replaced dopamine with low-cost catechol and polyamine (only 8% of the cost of dopamine), which could be polymerized in an alkaline solution and deposited on the surfaces of various materials. By using this cheap and simple modification method, polypropylene (PP) separator could be transformed from hydrophobic to hydrophilic, while the pore structure and mechanical property of the separator remained intact. The uptake of electrolyte increased from 80% to 270% after the hydrophilic modification. Electrochemical studies demonstrated that battery with the modified PP separator had a better Coulombic efficiency (80.9% to 85.3%) during the first cycle at a current density of 0.1 C, while the discharging current density increased to 15 C and the discharge capacity increased by 1.4 times compared to the battery using the bare PP separator. Additionally, the modification allowed excellent stability during manifold cycles. This study provides new insights into utilizing low-cost chemicals to mimic the mussel adhesion and has potential practical application in many fields.

The last 5 years have witnessed rapid progress in the field of hybrid nanostructures toward enhanced optical and electronic properties. On this topic, we focus on the relevant progress that has been achieved on the basis of cation/anion exchange reactions (CERs/AERs). Different from those direct synthesis strategies, CERs/AERs can offer more freedom in tuning the chemical composition, crystal phases, doping, interfaces, and morphologies, which are key parameters to determine the optical and electronic properties of the target products. We present several examples, e.g., doped quantum dots (QDs), engineered core-shell QDs, metal-semiconductor hybrid nanostructures, hollow structures, and inorganic perovskite nanocrystals. These upgraded structures afforded by CERs/ AERs generally exhibit improved properties, such as increased quantum yields, prolonged lifetimes, and well-engineered band gaps for charge transportation and recombination, thus providing more opportunities for further advanced applications.

Traditional hydrogels always lose their flexibility and functions in dry environments because the internal water inevitably undergoes evaporation. In this study, a skin-inspired, facile, and versatile strategy for developing encapsulated hydrogels with excellent water retention capacity through a double-hydrophobic coating is proposed. The robust double-layer coating, which integrates a hydrophobic polymer coating with a hydrophobic oil layer simultaneously, can provide a barrier to prevent the evaporation of water. To overcome the weak interfacial strength between the hydrophilic hydrogel surface and the double-hydrophobic coating, (3-aminopropyl) triethoxysilane (APTES) is utilized as a chemical binding agent. Furthermore, the overall mechanical properties of the bulk hydrogel are not significantly affected, because the coating is only anchored to the surface and its thickness is much lower than that of the native hydrogel. Moreover, it is demonstrated that this proposed strategy particularly holds the capability of encapsulating various types and different shapes of hydrogels, leading to enhanced stability and a prolonged lifetime in air. Therefore, the proposed technology provides new insights for multifarious surface functionalization of hydrogel and broadens the range of hydrogel applications.