The sluggish kinetics and shuttle effect of lithium polysulfide intermediates are the major issues that retard the practical applications of lithium–sulfur (Li–S) batteries. Herein, we introduce a defect engineering strategy to construct a defected-UiO-66-NH2-4/graphene electrocatalytic membrane (D-UiO-66-NH2-4/G EM) which could accelerate the conversion of lithium polysulfides in high sulfur loadings and low electrolyte/sulfur (E/S) ratio Li–S batteries. Metal–organic frameworks (UiO-66-NH2) can be directionally chemical engraved to form concave octahedra with abundant defects. According to electrocatalytic kinetics and DFT calculations studies, the D-UiO-66-NH2-4 architecture effectively provides ample sites to capture polysulfides via strong chemical affinity and effectively delivers electrocatalytic activity of polysulfide conversion. As a result, a Li–S battery with such an electrocatalytic membrane delivers a high capacity of 12.3 mAh cm–2 (1013 mAh g–1) at a sulfur loading up to 12.2 mg·S cm–2 under a lean electrolyte condition (E/S = 5 μL mg–1-sulfur) at 2.1 mA cm–2 (0.1 C). Moreover, a prototype soft package battery also exhibits excellent cycling stability with a maintained capacity of 996 mAh g–1 upon 100 cycles.

Vanadium dioxide (VO2) is a typical metal-insulator transition (MIT) material, which changes from room-temperature monoclinic insulating phase to high-temperature rutile metallic phase. The phase transition of VO2 is accompanied by sudden changes in conductance and optical transmittance. Due to the excellent phase transition characteristics of VO2, it has been widely studied in the applications of electric and optical devices, smart windows, sensors, actuators, etc. In this review, we provide a summary about several phases of VO2 and their corresponding structural features, the typical fabrication methods of VO2 nanostructures (e.g., thin film and low-dimensional structures (LDSs)) and the properties and related applications of VO2. In addition, the challenges and opportunities for VO2 in future studies and applications are also discussed.

We propose a doping method by using [6,6]-phenyl-C-butyric acid methyl ester (PCBM) to fill the grain boundary interstices of the methylammonium lead iodide (CHNHPbI) perovskite for the elimination of pinholes. A sandwiched PCBM layer is also used between the perovskite and TiO layers to improve the interfacial contact. By using these two methods, the fabricated perovskite solar cells show a low hysteresis effect and high current density, which result from the improved compactness at the grain boundaries of the perovskite surface and the interface between the TiO/perovskite layers. The theoretical and experimental results indicate that PCBM can effectively suppress carrier recombination, regardless of the interfacial layer or dopant. We also found that the dark current reduced during the analysis of dark state current-voltage ( I- V) characteristics. The slopes of the I- V curves for the fluorine-doped tin oxide/PCBM-doped perovskite/Au device reduce monotonically with the increase in the PCBM concentration from 0.01 to 0.1 wt %, which suggest the decreasing defects in the perovskite layer. By tuning the PCBM doping and controlling the preparation process, we have successfully fabricated a planar TiO/PCBM-based PCBM-doped perovskite photovoltaic device that reaches a high current density of 22.6 mA/cm and an outstanding photoelectric conversion efficiency up to 18.3%. The controllability of the PCBM doping concentration and interfacial preparation shed light on further optimization of the photoelectric conversion efficiency of perovskite solar cells.