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...
By introducing Ag nanoclusters (NCs), ZnO-based resistive switching memory devices offer improved performance, including improved uniformity of switching parameters, and increased switching speed with excellent reliability. These Ag NCs are formed between the top-electrode (cathode) and the switching layer by an electromigration process in the initial several switching cycles. The electric field can be enhanced around Ag NCs due to their high surface curvature. The enhanced local-electric-field (LEF) results in (1) the localization of the switching site near Ag NCs, where oxygen-vacancy-based conducting filaments have a simple structure, and tend to connect Ag NCs along the LEF direction; (2) an increase in migration and recombination rates of oxygen ions and oxygen vacancies. These factors are responsible for the improvement in device performance.
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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