Search

The catalytic role of germanium (Ge) was investigated to improve the electrochemical performance of tin dioxide grown on graphene (SnO(2)/G) nanocomposites as an anode material of lithium ion batteries (LIBs). Germanium dioxide (GeO(20) and SnO(2) nanoparticles (<10 nm) were uniformly anchored on the graphene sheets via a simple single-step hydrothermal method. The synthesized SnO(2)(GeO(2))0.13/G nanocomposites can deliver a capacity of 1200 mA h g(-1) at a current density of 100 mA g(-1), which is much higher than the traditional theoretical specific capacity of such nanocomposites (∼ 702 mA h g(-1)). More importantly, the SnO(2)(GeO(2))0.13/G nanocomposites exhibited an improved rate, large current capability (885 mA h g(-1) at a discharge current of 2000 mA g(-1)) and excellent long cycling stability (almost 100% retention after 600 cycles). The enhanced electrochemical performance was attributed to the catalytic effect of Ge, which enabled the reversible reaction of metals (Sn and Ge) to metals oxide (SnO(2) and GeO(2)) during the charge/discharge processes. Our demonstrated approach towards nanocomposite catalyst engineering opens new avenues for next-generation high-performance rechargeable Li-ion batteries anode materials.

In this work, we report the synthesis of MoO2 nanoparticles grown on three dimensional graphene (3DG) via the reduction of α-MoO3 nanobelts through a facile chemical vapor deposition (CVD) approach under argon protection gas environment. In this synthesis approach, the presence of hydrophobic 3DG promoted the Volmer-Weber growth of MoO2 nanoparticles (30-60 nm). The as-prepared MoO2-3DG nanocomposite was directly used as a binder-free anode electrode for lithium ion batteries (LIBs) without additives and exhibited excellent electrochemical performance. It delivered high reversible capacities of 975.4 mA h g(-1) and 537.3 mA h g(-1) at the current densities of 50 and 1000 mA g(-1), respectively. Moreover, the electrode also showed an increased capacity from 763.7 mA h g(-1) to 986.9 mA h g(-1) after 150 discharge and charge cycles at a current density of 200 mA g(-1). The enhanced electrochemical performance of MoO2-3DG nanocomposite electrode may be attributed to the synergistic effects of MoO2 nanoparticles and 3DG layers. This facile CVD synthesis process presents a feasible route for large-scale production of high performance, environmentally friendly electrode. In addition, this process also has the potential of being utilized in other materials for energy storage devices application.

Hybrid urchin-like nanostructures composed of a spherical onion-like carbon (OLC) core and MoS2 nanoleaves were synthesized by a simple solvothermal method followed by thermal annealing treatment. Compared to commercial MoS2 powder, MoS2/OLC nanocomposites exhibit enhanced electrochemical performance as anode materials of lithium-ion batteries (LIBs) with a specific capacity of 853 mA h g(-1) at a current density of 50 mA g(-1) after 60 cycles, and a moderate initial coulombic efficiency of 71.1%. Furthermore, a simple pre-lithiation method based on direct contact of lithium foil with MoS2/OLC nano-urchins was used to achieve a very high coulombic efficiency of 97.6% in the first discharge/charge cycle, which is at least 26% higher compared to that of pristine MoS2/OLC nano-urchins. This pre-lithiation method can be generalized to develop other carbon-metal sulfide nanohybrids for LIB anode materials. These results may open up a new avenue for the development of the next-generation high-performance LIBs.

Visible electroluminescence (EL) with tunable wavelength has been observed at room temperature from randomly assembled n-CdS(x)Se(1-x) nanowires grown on a p(+)-SiC substrate by the vapor transport technique. The dominant emission peaks can be tuned from ∼720 to ∼520 nm by varying the composition of the alloy nanowires.