Temperature-Dependent Morphologies of Precursors: Metal-Organic Framework-Derived Porous Carbon for High-Performance Electrochemical Double-Layer Capacitors.

In this work, three Cu metal-organic framework samples with tunable rhombic, squama, and trucated bipyramid morphologies have been synthesized at 0, 25, and 60 °C, respectively, and further employed as precursors to initially prepare Cu@C composites by the calcination-thermolysis procedure. Then Cu@C composites have been etched with HCl and subsequently activated with KOH to obtain activated porous carbon (APC-0, -25, and -60). Interestingly, APC-25 presents a loose multilevel morphology of cabbage and possesses the largest specific surface area (1880.4 m2 g-1) and pore volume (0.81 cm3 g-1) among these APC materials. Consequently, APC-25 also exhibits the highest specific capacitance of 196 F g-1 at 0.5 A g-1, and the corresponding symmetric supercapacitor cell (SSC) achieves a remarkable energy density of 11.8 Wh kg-1 at a power density of 350 W kg-1. Furthermore, APC-25 shows excellent cycling stability, and the loss of capacitance is only 7.7% even after 10000 cycles at 1 A g-1. Significantly, five light-emitting diodes can be lit by six SSCs, which proves that APC-25 can be used in energy storage devices.

Spatially Guided Assembly of Polyoxometalate Superlattices and Their Derivatives as High-Power Sodium-Ion Battery Anodes.

The use of polyoxometalate clusters (POMs) with multitudinous structures and surface properties as building blocks has sparked the development of cluster-assembled materials with many prospective applications. In comparison to classic molecules and assembly processes, control over the steric interactions and linkage of large POMs to achieve superlattices with multiple levels of organization remains a great challenge. This work presents a universal approach to modulate the spatial coordination behavior and configurations, and achieves a class of cluster superlattice architectures formed by linear alignment and two-dimensional arrangement of POM units. The formation mechanism is explained as a stepwise co-assembly pathway in which POMs can intervene and dictate a typical stripping-restacking combination mode with the lamellar mediator. These cluster superlattices with long-range POMs ordering impart distinct merits to their derivatives by sulfuration, for which we demonstrate the substantially promoted power and cycling life of these POM derivatives applied as sodium-ion battery anodes.