Hybrid micro−mesoporous graphitic carbon spheres (M-MGCSs) featuring ordered mesoporous graphene-like cores and uniform microporous carbon shells are designed by transformation of self-assembled Fe 3 O 4 nanoparticle supraparticles and are used as an efficient, dual spatially confined sulfur reservoir for lithium−sulfur (Li−S) batteries. Such rationally designed M-MGCSs synergistically combine the merits of micro-and mesoporous carbons when used as the sulfur host in Li−S batteries: the core having interconnected spherical mesopores of 9.0 nm provides sufficient space for loading S 8 molecules, while the shell having micropores of 0.6 nm can entrap only small S 2−4 molecules, which are converted into electrolyte-insoluble polysulfides during discharge, minimizing the outward diffusion of long-chain polysulfides from the core. These advantageous structural features, combined with the highly graphitic nature and mesoscale spherical morphology of M-MGCSs, enable Li−S cathodes with greatly improved performance even at high sulfur areal loadings.

Searching for new electrode materials with high capacities and excellent rate performance is crucial for the development of next-generation lithium-ion batteries (LIBs). Silicon carbide (SiC), which is traditionally considered to be electrochemically inert toward lithiation, has recently been demonstrated to be a potential high-performance anode material upon activation by surface graphitization. Despite the great potential, it remains a grand challenge to synthesize SiC nanostructures with precisely controlled morphologies and surface properties, due to the rather high reaction temperatures (>1200 °C) typically required for SiC crystallization. Herein, we designed and synthesized a novel type of SiC nanostructures in which bowl-like, ultrathin SiC nanoshells were encapsulated in hollow graphitic carbon spheres (designated as SiC@HGSs), which exhibited unexpectedly high electrochemical performance when used as LIB anodes. SiC@HGSs retained a stable capacity of 1345 mAh g −1 at a current density of 0.6 A g −1 after 600 cycles and 742 mAh g −1 at 3 A g −1 after 1000 cycles. Even at a high current density of 6 A g −1 , SiC@HGSs could still deliver a capacity of ∼400 mAh g −1 . The superior high-rate performance is attributable to the unique architecture and exceptional structural durability of SiC@HGSs.

No abstract

Two asymmetric three-dimensional (3D) holetransporting materials (HTMs) containing a triphenylethylene core and peripheral diphenylamine/triphenylamine moieties are first synthesized and successfully used in perovskite solar cells (PSCs). Both HTMs are obtained from facile preparation procedures and simple purification techniques. The X-ray diffraction, aggregation-induced emission properties, absorption and emission spectra, electrochemical properties, thermal stability, density functional theory calculations, hole mobility, scanning electronic microscopy, atomic force microscopy, steady-state and time-resolved photoluminescence, water contact angles, and photovoltaic parameters of the PSCs are compared. The highest power conversion efficiency increases from 12.57% (CJ-02) to 18.56% (CJ-01), rivaling that obtained from the state-of-the-art 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) (18.69%). Further, the lab synthetic cost of CJ-01 is only about 15.5% of the price of commercial spiro-OMeTAD, and the concentration of CJ-01 solution for device fabrication is less than half of the concentration of spiro-OMeTAD solution (30.0 vs 72.3 mg mL −1 ). These results demonstrate that the propeller-shaped compounds with a highly twisted conformation are readily available and promising alternative HTMs for PSCs. Moreover, an applicable strategy to design new HTMs with 3D structure for achieving highly efficient PSCs is proposed.