commercial LIBs with graphite-based materials as anode cannot meet the above requirements due to the limitation of graphite itself. It shows a low theoretical capacity of 372 mAh g −1 , [2] rapid capacity decay, and possible safety issues during cycling process. Recently, transition metal dichalcogenides (TMDs) have attracted widespread attention in the energy storage fields, especially its application in electrodes of LIBs. As a representative of TMDs, MoS 2 has shown fascinating and superior electrochemical performance due to its unique layered structure. [3,4] MoS 2 always exists in the following three phases: 2H, 1T, and 3R phase according to different coordinations of Mo and S atoms. [5][6][7][8][9] The 2H and 1T phase MoS 2 exhibit notable energy storage and conversion performance due to their characteristic structure and rich physical and chemical properties. 2H-MoS 2 is a semiconducting phase with trigonal prismatic structure. Its high theoretical capacity of 670 mAh g −1 renders it fit to be considered as a promising anode material for LIBs. [10,11] However, two severe issues of 2H-MoS 2 electrode still need to be taken into account: 1) the structure destruction induced by the large volume change during lithium-ions intercalating and deintercalating process; 2) the poor electronic conductivity, arising from a large bandgap of about 1.9 eV. [12,13] To overcome these shortcomings, a large amount of efforts was devoted to modify the electrochemical performance of 2H-MoS 2 . Two general ways are: 1) designing nanostructure materials, such as nanotubes, [14] nanosheets, [15] and nanospheres [16] ; 2) hybridizing 2H-MoS 2 with carbonaceous materials, such as graphene. [17,18] Compared with 2H phase MoS 2 , 1T phase MoS 2 presents a metallic transport behavior and its electric conductivity is approximately 5 orders of magnitudes higher than that in semiconducting 2H-MoS 2 . [19] This contributes to the transfer of electrons and ions in the electrode material. Furthermore, 1T-MoS 2 owns an expanded interlayer spacing of about 1 nm, which is nearly 1.5 times larger than that in 2H-MoS 2 (about 0.65 nm). [20,21] Such an expanded interlayer spacing makes lithium ions embedding and de-embedding much easier. However, the conventional methods to fabricate 1T-MoS 2 require an alkali metal intercalation or exfoliation process, which is unstable, dangerous, complicated, and time-consuming. [22] Preparing 1T phase MoS 2 possesses higher conductivity than the 2H phase, which is a key parameter of electrochemical performance for lithium ion batteries (LIBs). Herein, a 1T-MoS 2 /C hybrid is successfully synthesized through facile hydrothermal method with a proper glucose additive. The synthesized hybrid material is composed of smaller and fewer-layer 1T-MoS 2 nanosheets covered by thin carbon layers with an enlarged interlayer spacing of 0.94 nm. When it is used as an anode material for LIBs, the enlarged interlayer spacing facilitates rapid intercalating and deintercalating of lithium ions and accommodates volume change dur...

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Transition metal nitrides (TMNs) are considered as potential electrode materials for high‐performance energy storage devices. However, the structural instability during the electrochemical reaction process severely hinders their wide application. A general strategy to overcome this obstacle is to fabricate nanocomposite TMNs on the conducting substrate. Herein, the honeycomb‐like CoN‐Ni3N/N‐C nanosheets are in situ grown on a flexible carbon cloth (CC) via a mild solvothermal method with post‐nitrogenizing treatment. As an integrated electrode for the supercapacitor, the optimized CoN‐Ni3N/N‐C/CC achieves remarkable electrochemical performance due to the enhanced intrinsic conductivity and increased concentration of the active sites. In particular, the flexible quasi‐solid‐state asymmetric supercapacitor assembled with CoN‐Ni3N/N‐C/CC cathode and VN/CC anode delivers an excellent energy density of 106 μWh cm−2, maximum power density of 40 mW cm−2, along with an outstanding cycle stability. This study provides a neoteric perspective on construction of high‐performance flexible energy storage devices with novel metallic nitrides.

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Polycrystalline sample of the new layered superconductor Bi 4 O 4 S 3 is successfully synthesized by solid-state reaction method by using Bi, S and Bi 2 O 3 powders with one step reaction. The superconducting transition temperature (T c onset =4.5 K), the zero resistance transition temperature ( T c0 =4.07 K) and the diamagnetic transition temperature (4.02 K at H=10 Oe) were confirmed by electrical transport and magnetic measurements. Also, our results indicate a typical type II-superconductor behavior. In addition, a large thermoelectric effect was observed with a dimensionless thermoelectric figure of merit (ZT) of about 0.03 at 300K, indicating Bi 4 O 4 S 3 can be a potential thermoelectric material. PASC: 74.25.-q, 74.70.Ad, 74.25.Fy

The effects of Rh doping on the structural, magnetic, electrical, and thermal transport properties of Ca3Co4–x Rh x O9 (0 ≤ x ≤ 0.4) samples have been investigated systematically. XRD and XPS results show that the doped Rh ions are in the form of Rh3+. Only a metal–insulator transition (MIT) and an anomaly of the slope related to the transition from a Fermi liquid to an incoherent metal at low temperatures were observed in the resistivity curve for the undoped sample. As Rh ions were doped into the samples, an additional anomaly and MIT occurred in the resistivity curve near room temperature, which are suggested to originate from the spin-state transition (SST) of Co ions. The low-temperature MIT temperature increased with increasing Rh-doping content, indicating that the spin-density-wave state became stable as a result of the enhanced random Coulomb potential in CoO2 octahedral block layers induced by Rh substitution. Based on an analysis of the thermopower and XPS data, Rh3+ ions are suggested to substitute at the Co3+ sites of CoO2 layers. The substitution induced a partial SST of Co4+ ions from the low-spin to the high-spin state, leading to the formation of a spin-state polaron. The evolution of the electrical and magnetic properties with Rh doping is summarized in a single phase diagram for Ca3Co4–x Rh x O9. It should be noted that the thermopower of the system did not change obviously with Rh doping, but the thermal conductivity decreased significantly. As a result, the ZT value increased markedly with increasing Rh-doping content. The ZT value at room temperature for Ca3Co3.6Rh0.4O9 reached 0.014, which is about 2.4 times larger than that of Ca3Co4O9. The results show that Rh doping might be an effective route to improving the thermoelectric performance of the Ca3Co4O9 system.

Single crystals of Ca3Co4−xTixO9 (x=0, 0.2, 0.4, 0.6, and 0.8) are grown by flux growth technique. The effect of Ti doping at Co site on magnetic and transport properties is studied. All samples show Curie-Weiss behavior at temperatures above 50K except for the x=0.8 sample, and the effective magnetic moment μeff increases with increasing Ti content. The free-doped sample Ca3Co4O9 shows a ferrimagnetic transition at 19K. However, a spin-glass transition at Tf(∼20K) appears for the Ti doped samples and the transition temperature Tf shifts to higher temperature as the Ti content increases. The magnetic moment values M at Tf and 5K under the applied field of 4.5T increase with increasing Ti doping content. The variation of the magnetic properties may be related to the induced extra Co2+ ions in the CoO2 layer by substituting Ti4+ for Co3+. The resistivity ρ of the x=0, 0.2, 0.4, and 0.6 samples shows metalliclike behavior at high temperatures and a broad metal-insulator (M-I) transition appears as the temperature decreases to a certain value Tmin. The value of resistivity and the ratio of ρ5K∕ρ300K increase with increasing Ti content. The results are discussed according to the decrease of charge carrier concentration in the samples, which is confirmed by the Hall coefficient measurement. For the x=0.8 sample, there exists another M-I transition in the vicinity of 269K, which is suggested to originate from the spin-state transition of Co3+ or Co4+ ions.