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Hollow-sphere ZnSe is successfully obtained through Ostwald ripening. Carbon nanoparticles are designed and utilized to form a wrapped carbon network as a conductive buffering matrix by subsequent annealing. The ZnSe/C composites, as anode materials for lithium-ion batteries (LIBs), exhibit excellent Li+ storage properties, delivering a high reversible capacity of 573.7 mA h g−1 at 1.0 A g−1 after 800 cycles. Even upon increasing the high current density to 20.0 A g−1, the reversible capacity can achieve 318.8 mA h g−1 after 5000 cycles. The superior rate capability is confirmed through the current density return from 20.0 to 1.0 A g−1, and ZnSe/C composites still recover up to 469 mA h g−1, with a retention of 92%. The enhanced electrochemical performances of ZnSe/C composites are attributed to the unique structure and the introduction of conductive carbon networks, which can improve the Li+ diffusion coefficient in the insertion and extraction process. Furthermore, the interconnected network also alleviates the volume variation during cycling and further enhances the structural stability. [ABSTRACT FROM AUTHOR]

Heteroatom modification represents one of the major areas of carbon materials' research in electrical energy storage. However, the influence of heteroatomic state evolution on electrochemical properties remains an elusive topic. Herein, thiophene‐2,5‐dicarboxylic acid is chemically activated to prepare O,S‐diatomic hybrid carbon material (OS–C). The heteroatoms and carbon matrix coexist in the form of CO/CO and CS/SS bonds, which introduce porous networks to the partially graphitized carbon skeleton and provide abundant active sites for better ion absorption. Moreover, the heteroatoms and carbon matrix are bridged to establish stable pseudocapacitive functional groups like quinoid unit and disulfide bonds, which can be electrochemically converted into benzenoid units and mercaptan anions through Faradaic reactions to further improve the reversible capacity. Combined with the detailed kinetic exploration and in situ investigation of the electrochemical impedance spectra, the energy storage mechanism for lithium/sodium is proposed in the following steps: Faradaic reactions at a higher potential range, energy storage at active sites, and ions intercalation on the graphitized parts in the low‐voltage states. Greatly, the electrode can store lithium up to the capacity of ≈700 mAh g−1, while also delivering ≈330 mAh g−1 of sodium storage, providing lifetimes in excess of thousands of cycles. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • ZIF-8 nanocubes are rapidly synthesized and adjusted in aqueous solution. • ZnSe nanoparticles embedded N-doped carbon nanocubes (ZS-NP@NC) are first prepared. • ZS-NP@NC-600 displays high discharge capacity and excellent cyclability. • Kinetics analysis confirms the pseudocapacitive behavior of ZS-NP@NC. Abstract ZnSe is regarded as a promising anode material for reversible Li-ion batteries because of its high theoretical capacity. Herein, we report a facile chemical precipitation method to controllably synthesize ZIF-8 nanocubes and then select them as sacrificial templates to prepare ZnSe nanoparticles embedded N-doped carbon nanocubes. The as-obtained ZnSe/carbon nanocomposite at 600 °C demonstrates a high initial discharge capacity of 1170.8 mAh g−1 with the initial columbic efficiency of 68.8% at the current density of 0.1 A g−1 in the voltage range of 0.01–3 V. In addition, it displays a reversible capacity of 1166.6 mAh g−1 after 500 cycles at the current density of 0.5 A g−1, indicating the excellent cyclic stability for the designed composites. The enhanced electrochemical performance can be ascribed to its high specific surface area (493.45 m2 g−1) and unique mesoporous structure, which provides efficient Li+ transport channels and additional storage sites. Furthermore, the existence of faradaic pseudocapacitance in ZnSe/carbon nanocomposites also affords additional capacity and contributes to the increased capacity with respect to charge/discharge cycle number. [ABSTRACT FROM AUTHOR]

Hydrogenated fullerene-like carbon (H-FLC) film is of great potential in reaching macro-scale ultra-low friction. But its friction regime is still under debate. In this study, friction behavior of H-FLC was investigated in vacuum and ambient under various rotational speeds. Results show that friction coefficient is in negative correlation with rotational speed. At rotational speed of 500 rpm, H-FLC film reached ultra-low friction (0.015). Detailed nano-structure evolution research indicates that the odd carbon ring fraction at sliding interface is the origin of H-FLC's low friction. Namely, randomly oriented pentagonal and heptagonal carbon rings were rearranged in wear track, which enhanced the FL content. This work corroborated that rehybridization at frictional interface of H-FLC plays an important role in its ultra-low friction. • FL-C:H film reached ultra-low friction (0.017) in high vacuum. • FL-C:H film's friction coefficient strongly depends on the sliding speed. • Rotational speed induced pentagonal and heptagonal carbon rings' fraction change at the frictional interface. [ABSTRACT FROM AUTHOR]