Yongchun Zhu

Synthesis of MnO@C core–shell nanoplates with controllable shell thickness and their electrochemical performance for lithium-ion batteries

MnO@C core–shell nanoplates with a size of ∼150 nm have been prepared via thermal treatment deposition of acetylene with the precursor of Mn(OH)2 nanoplates, which has been hydrothermally synthesized. The thickness of the carbon shells varied from ∼3.1 to 13.7 nm by controlling the treatment temperature and reaction duration time. The electrochemical performance of the MnO@C nanoplates, which were synthesized at 550 °C for 10 h with a carbon shell thickness of ∼8.1 nm, display a high reversible capacity of ∼770 mA h g−1 at a current density of 200 mA g−1 and good cyclability after prolonged testing, which is higher than that of MnO@C nanoplates with a carbon shell thickness of ∼3.1, 4.0, 4.2, 10.9 and 13.7 nm.

Synthesis of MoS2 @C Nanotubes Via the Kirkendall Effect with Enhanced Electrochemical Performance for Lithium Ion and Sodium Ion Batteries.

A MoS2 @C nanotube composite is prepared through a facile hydrothermal method, in which the MoS2 nanotube and amorphous carbon are generated synchronically. When evaluated as an anode material for lithium ion batteries (LIB), the MoS2 @C nanotube manifests an enhanced capacity of 1327 mA h g(-1) at 0.1 C with high initial Coulombic efficiency (ICE) of 92% and with capacity retention of 1058.4 mA h g(-1) (90% initial capacity retention) after 300 cycles at a rate of 0.5 C. A superior rate capacity of 850 mA h g(-1) at 5 C is also obtained. As for sodium ion batteries, a specific capacity of 480 mA h g(-1) at 0.5 C is achieved after 200 cycles. The synchronically formed carbon and stable hollow structure lead to the long cycle stability, high ICE, and superior rate capability. The good electrochemical behavior of MoS2 @C nanotube composite suggests its potential application in high-energy LIB.

Formation and morphology control of nanoparticlesvia solution routes in an autoclave

Formation and morphology control of nanomaterials is a crucial issue in nanoscience research in the exploitation of novel properties. This article presents a review of some research activities on the formation and morphology control of nanoparticlesvia solution routes in an autoclave over the last decade. Several solution systems, including hydrothermal, solvothermal and mixed solvothermal routes, are specifically discussed and highlighted. A helical belt template mechanism was proposed for the formation of the Te nanotubes in aqueous ammonia. Assisted by the surfactant of sodium dodecyl benzenesulfonate (SDBS), nickel nanobelts were hydrothermally synthesized. Ethylenediamine (En) and n-butylamine can be used as shape controllers to one-dimensional (1D) semiconductor nanostructures in the solvothermal process. The phase of metastable and stable MnS crystallites can be controlled by solvothermal reaction in various solvents. Selective preparation of 1D to 3D CdS nanostructures was achieved by controlling the volume ratio of the mixed solvents. With poly(vinylpyrrolidone) (PVP) serving as a soft template, the transformation from nanowires to nanotubes, then to nanowires was observed in the mixed solvents of distilled water and ethanolamine (EA).

Preparation of Nanocrystalline Silicon from SiCl4 at 200 °C in Molten Salt for High‐Performance Anodes for Lithium Ion Batteries

Crystalline Si nanoparticles are prepared by reduction of SiCl4 with metallic magnesium in the molten salt of AlCl3 at 200 °C in an autoclave. AlCl3 not only acts as molten salt, but also participates in the reaction. The related experiments confirm that metallic Mg reduces AlCl3 to create nascent Al which could immediately reduce SiCl4 to Si, and the by-product MgCl2 would combine with AlCl3 forming complex of MgAl2Cl8. As anode for rechargeable lithium ion batteries, the as-prepared Si delivers the reversible capacity of 3083 mAh g(-1) at 1.2 A g(-1) after 50 cycles, and 1180 mAh g(-1) at 3 A g(-1) over 500 cycles.

Amorphous S-rich S1−xSex/C (x ≤ 0.1) composites promise better lithium–sulfur batteries in a carbonate-based electrolyte

Polysulfide dissolution and the insulating nature of sulfur cause significant capacity fading and low efficiency in rechargeable lithium–sulfur batteries. Here, we show that these defects can be effectively diminished by immobilizing sulfur in porous carbon via the interaction of a small amount of selenium. Amorphous S-rich S1−xSex/C (x ≤ 0.1) composites have been prepared starting from Se and S powders at 260 °C. Raman spectra reveal the existence of S–Se bonds in S1−xSex/C composites. As cathodes for lithium–sulfur batteries, S1−xSex/C (x ≤ 0.1) composites exhibit high electrochemical performance in a carbonate-based electrolyte. S0.94Se0.06/C composites deliver the best performance with a capacity of 910 mA h g−1 at 1 A g−1 over 500 cycles, 1105 mA h g−1 at 0.2 A g−1 after 100 cycles and a good rate capability of 617 mA h g−1 at 20 A g−1.

MnO@1-D carbon composites from the precursor C4H4MnO6 and their high-performance in lithium batteries

MnO@1-D carbon composites were synthesized simultaneously through a single heating procedure using C4H4MnO6 as the precursor for both the MnO and 1-D carbon. MnO nanoparticles are uniformly dispersed inside or adhered to the surface of the 1-D carbon nanotubes, and these carbon nanotubes overlap each other to form carbon scaffolds. As an anode for lithium-ion batteries, the MnO@1-D carbon composites deliver a reversible capacity of 1482 mA h g−1 at a current density of 200 mA g−1. When the current density rises to 1460 mA g−1, the capacity remains at 810 mA h g−1 even after 1000 cycles. Such a unique carbon structure can act as a scaffold for MnO, which not only improves the electronic conductivity, but also provides a support for loading MnO nanoparticles. This synchronous process may pave a way to obtain such uniform and stable electrode materials with enhanced performance, which may find use in other applications such as catalysis, water treatment and supercapacitors.

Electrochemical performance of rod-like Sb–C composite as anodes for Li-ion and Na-ion batteries

Rod-like Sb–C composite has been synthesized by a synchronous reduction and carbon deposition process. The Sb–C composite anode exhibits a reversible capacity of 478.8 mA h g−1 at 100 mA g−1 after 100 cycles for Li-ion batteries and exhibits a reversible capacity of 430.9 mA h g−1 at 50 mA g−1 after 100 cycles for Na-ion batteries.

A Deep Reduction and Partial Oxidation Strategy for Fabrication of Mesoporous Si Anode for Lithium Ion Batteries

A deep reduction and partial oxidation strategy to convert low-cost SiO2 into mesoporous Si anode with the yield higher than 90% is provided. This strategy has advantage in efficient mesoporous silicon production and in situ formation of several nanometers SiO2 layer on the surface of silicon particles. Thus, the resulted silicon anode provides extremely high reversible capacity of 1772 mAh g(-1), superior cycling stability with more than 873 mAh g(-1) at 1.8 A g(-1) after 1400 cycles (corresponding to the capacity decay rate of 0.035% per cycle), and good rate capability (∼710 mAh g(-1) at 18A g(-1)). These promising results suggest that such strategy for mesoporous Si anode can be potentially commercialized for high energy Li-ion batteries.

A low temperature molten salt process for aluminothermic reduction of silicon oxides to crystalline Si for Li-ion batteries

A low temperature molten salt process is developed to prepare crystalline Si nanoparticles through the reduction of micro-sized high silicon zeolite by metallic Al (or Mg) in molten AlCl3. The reaction can be initiated at 200 °C, and the yield is about 40%. As the reaction temperature increases to 250 °C, the yield can reach about 75%. When the prepared Si was used as an anode for Li-ion batteries, reversible capacities of 2663 mA h g−1 at 0.5 A g−1 after 50 cycles and 870 mA h g−1 at 3 A g−1 after 1000 cycles can be obtained. Similarly, this synthetic strategy is employed to synthesize Si nanoparticles starting from various abundant raw materials including SiO2 powder, kieselguhr, fiberglass, and even the natural mineral of albite.

Changeable position of SPR peak of Ag nanoparticles embedded in mesoporous SiO2 glass by annealing treatment

Small Ag particles or clusters doped mesoporous SiO2 composite glass were prepared by the sol–gel process combined girradiation at room temperature and in ambient pressure. High-resolution transmission electron microscope (HRTEM) has revealed the existence of Ag nanoparticles and their growing through annealing treatments. With the particle size changing, an interesting reversible peak shift effect of the surface plasma resonance (SPR) was observed in the optical absorption measurement, which is explained as a comprehensive competitive result of both intrinsic property (size effect) and extrinsic influence from the matrix or the surrounding medium (interface interaction and its induced spill-out effect). # 2002 Elsevier Science B.V. All rights reserved.