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Molybdenum disulfide is considered an excellent anode material for lithium-ion batteries due to its unique structure and high specific capacity. However, molybdenum disulfide's inherent low ionic transport rate and low intrinsic conductivity have limited its application in lithium-ion batteries. Compounding with carbon materials is an effective way to overcome these limitations in the application of molybdenum disulfide. In this work, the effect of carbon layer on the growth of molybdenum disulfide was systematically investigated in order to disclose the role and influence of carbon in composites with molybdenum disulfide. Furthermore, our work provides an effective method for the structural optimization of one-dimensional composites based on carbon and molybdenum disulfide just by controlling the ratio of carbon precursor to molybdenum source during its formation. After structural optimization, effective MoS2@C composite materials were successfully synthesized, which exhibited greatly enhanced electrical conductivity and structural stability and maintained a specific capacity of 800.4 mA h g−1 even after 1200 cycles at a current density of 1 A g−1 possibly due to the excellent specific capacity of molybdenum disulfide. [ABSTRACT FROM AUTHOR]

A carbon layer usually covers the outside of SnS/MoS2 nanosheets produced by a traditional C-layer cladding process, resulting in a material with a lower specific surface area and fewer active sites. Therefore, it is difficult for these as-obtained SnS and MoS2 materials to be directly employed as electrode materials. There is a great need to develop a new C-layer coating process that can effectively coat active materials and simultaneously increase the specific surface area. In this study, novel SnS@C/MoS2 nanotubes were designed and synthesized by a self-sacrificing template method (SSTM). Specifically, MoO3 nanoribbons were first coated with Sn to produce Sn-MOF, and SnS@C/MoS2 nanotubes with a particular nanosheet architecture preserved were achieved via an elegant SSTM vulcanization strategy. This SSTM preparation method not only retains the nanosheet microstructure of the surface but also leaves a thin layer of amorphous carbon on the surface, which greatly improves the conductivity and effectively improves the cycling stability. In addition to above-mentioned advantages, there is a synergistic effect between the various components of the SnS@C/MoS2 nanotubes, which has a positive effect on the electrochemical performance. When used as the anode of a lithium-ion battery (LIB), the SnS@C/MoS2 composite can maintain a specific discharge capacity of 970.9 mAh g−1 after 500 cycles at a current density of 1 A g−1, and a specific discharge capacity of 778.1 mAh g−1 even after 1000 cycles at a current density of 2 A g−1. This method provides a reference for the synthesis of other nanostructured materials. [ABSTRACT FROM AUTHOR]

Inspired by the biological visual system, the biomimetic visual systems are of great significance to integrate large-scale and small-scale organic photon synaptic sensors and further construct a neural form of an artificial visual system. However, there are still many unavoidable problems in fabricating synaptic transistor arrays with good integrity. Herein, we fabricated synaptic arrays based on CsPbBr3 thin film/TIPS-pentacene nanowires. Thanks to the confinement effect of the template imprinting process on organic precursor solutions, the surface of the composite film was smooth and flat without obvious grain boundaries and the composite transistor on the synaptic array had ultra-high stability. High cycling stability of a single device was obtained, and the excellent overall consistency of steady-state leakage source current and good transient photocurrent of multiple devices under dark and light conditions were achieved. The light-to-dark current ratio of the synaptic array exceeded 8 × 103 when the light was introduced. The average transient peak photocurrent of −14 nA was achieved. Based on the compact model of organic transistors, the experimental data was fitted to estimate the impact of light power changes on the photoelectronic performance of the device and evaluate the transient operating stability of different devices within the arrays. Based on a composite synaptic array, an artificial vision system was constructed to achieve image processing functions. [ABSTRACT FROM AUTHOR]

Unsatisfactory cycling stability and rate capability due to volume expansion and poor electrical conductivity greatly hinder the practical application of MoS2-based materials. Aiming to address these issues, a novel 3D hierarchical conductive network architecture consisting of MoS2 nanotubes derived from self-assembled ultrathin MoS2 nanosheets with in situ N-doped carbon intercalation and reduced graphene oxide used as an encapsulating function (NC-MoS2@rGO) were effectively achieved. Due to many advantages mainly including hollow tubes, ultrathin MoS2 nanosheets, expanded interlayer spacing and highly conductive rGO wrapping, this architecture achieves more active sites, faster electron and ion transport rates, and greater structural stability. These advantages are finally attributable to the excellent electrochemical performance of lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs). In LIBs, NC-MoS2@rGO displays a high specific capacity of 1308.6 mA h g−1 at 0.2 A g−1 after 200 cycles, superior rate capability (834.2 mA h g−1 at 10 A g−1), and ultra-long cycle stability (528.4 mA h g−1 at 5 A g−1 after 6590 cycles). In addition, the electrode also obtained the expected discharge capacity (554.8 mA h g−1 at 0.2 A g−1 after 200 cycles) and cycle stability (463.6 mA h g−1 at 1 A g−1 after 1000 cycles and 383.2 mA h g−1 at 2 A g−1 after 1500 cycles) in Na ion storage. Furthermore, we elucidated the highly reversible electrochemical storage behavior of Na ions by using the ex situ X-ray diffraction (XRD) technique. Density functional theory (DFT) calculations further prove the positive effect of the added graphene on the improvement of battery performance. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have been extensively studied due to their porous structures and large specific surface areas. Its unique combination of central metal and organic ligand has become a common precursor for the synthesis of metal phosphides, selenides, oxides, and sulfides. However, the carbonaceous structure derived from some MOF materials is still not enough to perfectly alleviate the negative impact of the volume change of metal sulfides. Herein, bimetallic MOF (Zn‐Co‐ZIF) is used as a precursor, coated with dopamine hydrochloride, and then calcined and gas‐phase vulcanized to prepare ZnS/CoS2‐C@NC with a double‐carbon‐layer core–shell structure. The existence of the two carbonaceous structures can not only improve the electron transport ability, but also play an important role in alleviating the volume expansion caused by metal sulfides during repeated charging and discharging. Due to its stable carbon layer structure, ZnS/CoS2‐C@NC has a higher specific capacity (1175.4 mAh g−1 in lithium‐ion batteries (LIBs) and 430.9 mAh g−1 in sodium‐ion batteries after 100 cycles at a current density of 0.2 A g−1 respectively) and excellent rate capability (338.2 mAh g−1 specific capacity maintained after 2000 cycles at a current density of 5 A g−1 in LIBs). [ABSTRACT FROM AUTHOR]

Metal sulfides, one kind of electrode material with very high theoretical capacity, have been widely studied for use in lithium and sodium ion batteries. However, there are some problems hindering their applications in electrodes, such as low conductivity and volume expansion. The MOF introduces metals with different coordination strengths into an existing MOF structure, which improves the performance of the electrode to a certain extent. In this paper, Fe/Zn bimetallic MOF rod-like superstructure was prepared based on Ostwald theory. Accompanied by sulfuration, the MOF was effectively combined with MoS2 and GO, and the objective materials Fe7S8-C/ZnS-C@MoS2/rGO composites were successfully prepared. The MOF material provides a good frame and an efficient electron transport path, while the robust rGO wall effectively inhibits the pulverization of materials during the lithium/sodium intercalation/escalation courses. This particular material exhibited excellent cycling and rate capability performance when used in Li/Na-ion batteries. When used in Li-batteries, the electrode material delivered a specific capacity of 1598.3 mA h g−1 at 0.1 A g−1 and remained at 1196.7 mA h g−1 even after about 100 cycles and further exhibited a specific capacity of 368.68 mA h g−1 at the current rate of 5 A g−1 even after 1000 cycles, respectively. As for sodium batteries, these electrode materials exhibited an initial reversible capacity of 1053.6 mA h g−1 at 0.1 A g−1 and the reversible capacity was still as high as 592.2 mA h g−1 after 200 cycles. It is perhaps that this composite material with its particular architecture and composition is greatly beneficial for electron transfer and Li/Na ion diffusion. In the repeated physicochemical/nutrifying process, the appropriate distance between adjacent MOFs is of great help in preventing volume changes and thus improving the electrochemical performance. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2), which is a two-dimensional transition metal chalcogenide, has been considered to have great lithium/sodium storage potential. However, its poor conductivity, unsatisfactory mechanical stability and large volume change upon cycling make MoS2 not well applied in practice. Herein, MoS2@C nanobelts (MoS2@C NBs), which possess the nanostructure of MoS2 nanoflakes completely encapsulated within an amorphous carbon layer, were obtained by utilizing MoO3 nanobelts as self-sacrificing templates, followed by a facile thermal decomposition of solution-evaporated glucose and an in situ hydrothermal sulfidation process. This unique nanostructure provides not only good electrical conductivity and short ion diffusion length, but also excellent structure stability. When applied in lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs), the nanobelts exhibit enhanced electrochemical properties. In LIBs, the nanobelts deliver a high discharge capacity of 1189 mA h g−1 after 200 cycles at 0.2 A g−1 and a long-cycle stability of 626 mA h g−1 even after 800 cycles under 1 A g−1. Furthermore, excellent rate capabilities of 1133, 1180, 1078, 926, 704 and 1249 mA h g−1 at 0.1, 0.2, 0.5, 1 and 0.1 A g−1, respectively, are also acquired. As for NIBs, after 100 cycles at 0.2 A g−1, a charge capacity of 328.8 mA h g−1 can be maintained and the retention rate is 83.2%. [ABSTRACT FROM AUTHOR]