The combination of a highly exfoliated, graphene-like MoS₂ cathode and ultrasmall Mg nanoparticle anode is proposed, for the first time, for rechargeable Mg batteries. Such a configuration exhibits an operating voltage of 1.8 V and a well reversible discharge capacity of ca. 170 mA h g−1, emphasizing the necessity of rational morphological control of electrode materials and opening up new opportunities for rechargeable Mg batteries.
Rechargeable lithium-ion batteries are considered intriguing power sources for a wide variety of applications because of their high energy density, lightweight design and environmental friendliness. With respect to the anode of Li-ion batteries, silicon-based materials have attracted tremendous interest owing to their extremely high theoretical capacity of about 4200 mAh g -1 (with the formation of Li 4.2 Si alloy),  which is much higher than that of commercialized graphitic carbon (372 mAh g -1 for compound LiC 6 ) and other Li alloys. [3,4] However, Si suffers from serious irreversible capacity and poor cyclability, which result from the huge volume swings during lithium ion insertion/extraction process. This pulverization disadvantage is the obstacle for practical application of Si as the anode materials of rechargeable Li-ion batteries. The current strategies to overcome the so-called pulverization of Si are focusing on two issues: reducing the alloy particle size and using composite materials.  For example,Wilson and Dahn prepared carbon-containing nanodispersed Si with reversible specific capacity of 500 mAh g -1 in the former case,  and Holzapfel et al. prepared nanosized Si/graphite composites with a stable capacity of 1000 mAh g -1 in the latter.  Recently, Liu's group reported on the synthesis of carbon-coated 44 wt % Si nanocomposites, exhibiting a capacity of 1489 mAh g -1 after 20 cycles.  In view of the literature, the significant improvement on the electrochemical performance of Si is still necessary to achieve larger gravimetric capacity, higher coulombic efficiency and better cylability. It is noted that hollow nanomaterials of metals and transition-metal oxides are promising candidates as high-energy electrode materials.  In particular, Archer and co-workers reported that hollow SnO 2 nanospheres exhibited superior cycling properties and high initial discharge capacity of 1140 mAh g -1 . On the other hand, although many methods for the preparation of Si nanocrystals have been described, [13,14] controlled synthesis of hollow Si nanospheres still remains a great challenge. Herein, we report on the preparation of nest-like Si nanospheres and their highly reversible lithium storage and excellent high-rate capability. This result suggests that the as-prepared nest-like Si nanospheres are promising candidates as the anode materials of rechargeable Li-ion batteries. The nest-like Si nanospheres were prepared by a solvothermal method,  with modified experimental setup (Fig. S1, Supporting Information and Experimental Sec.). It was found that the size and morphology of the products are greatly dependent on the experimental conditions. The direct reaction of NaSi and NH 4 Br under the solvothermal conditions, in which no cotton bags and LaNi 5 alloys were added in the reaction system, only led to Si nanosparticles ( Fig. S2a-c, Supporting Information). If the cotton bags are added into the system but without the addition of LaNi 5 alloys, the product is ...
In this paper, MnO2 nanomaterials of different crystallographic types and crystal morphologies have been selectively synthesized via a facile hydrothermal route and electrochemically investigated as the cathode active materials of primary and rechargeable batteries. Beta-MnO2 nano/microstructures, including one-dimensional (1-D) nanowires, nanorods, and nanoneedles, as well as 2-D hexagramlike and dendritelike hierarchical forms, were obtained by simple hydrothermal decomposition of an Mn(NO3)2 solution under controlled reaction conditions. Alpha- and gamma-MnO2 nanowires and nanorods were also prepared on the basis of previous literature. The as-synthesized samples were characterized by instrumental analyses such as XRD, SEM, TEM, and HRTEM. Furthermore, the obtained 1-D alpha- and gamma-MnO2 nanostructures were found to exhibit favorable discharge performance in both primary alkaline Zn-MnO2 cells and rechargeable Li-MnO2 cells, showing their potential applications in high-energy batteries.
Mg nanowires with the diameters of 30−50 nm, 80−100 nm, and 150−170 nm, which were prepared via a vapor-transport method, exhibited enhanced kinetics for hydrogen absorption/desorption. The present results clearly show that thinner Mg/MgH2 nanowires have a much lower desorption energy than that of thicker nanowires or bulk Mg/MgH2, indicating that changes in kinetics and thermodynamics are expected if the diameters of the nanowires are thinner than 30 nm.
We report on the synthesis, characterization, and electrochemical lithium intercalation of alpha-CuV2O6 nanowires, mesowires, and microrods that were prepared through a facile hydrothermal route. The diameters of the as-synthesized alpha-CuV2O6 nanowires, mesowires, and microrods were about 100 nm, 400 nm, and 1 microm, respectively. It was found that by simply controlling the hydrothermal reaction parameters, such as the reagent concentration and the dwell time, the transformation of microrods to nanowires was readily achieved via a "ripening-splitting" mechanism. Electrochemical measurements revealed that the as-prepared alpha-CuV2O6 nanowires and mesowires displayed high discharge capacities (447-514 mAh/g at 20 mA/g and 37 degrees C) and excellent high-rate capability. In particular, the alpha-CuV2O6 nanowires showed capacities much higher than those of alpha-CuV2O6 mesowires, microrods, and bulk particles. The mechanisms for the electrochemical lithium intercalation into the alpha-CuV2O6 nanowires were also discussed. From the Arrhenius plot of lithium intercalation into alpha-CuV2O6 nanowires, the activation energies were calculated to be 39.3 kJ/mol at 2.8 V (low lithium uptake) and 35.7 kJ/mol at 2.3 V (high lithium uptake). This result indicates that the alpha-CuV2O6 nanowires are promising cathode candidates for primary lithium batteries used in long-term implantable cardioverter defibrillators (ICD).
In this paper, nest-like Ni1-xPtx (x = 0, 0.03, 0.06, 0.09, and 0.12) hollow spheres of submicrometer sizes have been prepared through a template-replacement route and investigated as catalysts for generating hydrogen from ammonia borane (NH3BH3). Experimental investigations have demonstrated that the obtained Ni1-xPtx alloy hollow spheres exhibit favorable catalytic activities for both the hydrolysis and the thermolysis of NH3BH3. It was found that, in the presence of the Ni0.88Pt0.12 catalyst, the hydrolysis of NH3BH3 causes a quick release of H2, while the thermal decomposition of NH3BH3 occurs at lowered temperatures with increased mass loss. The present results indicate that NH3BH3 along with Ni1-xPtx alloy hollow spheres may find some applications for small-scale on-board hydrogen storage and supply.
Magnesium nano/mesostructures with spherical, platelike, rodlike, and sea‐urchin‐like shapes are prepared by a simple and efficient vapor‐transport method. They exhibit excellent electrochemical properties in Mg/air batteries. The figure shows discharge curves of the Mg/air batteries made from two samples, at a constant current of 0.5 mA and a temperature of 25 °C.
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