Search

Abstract: A new method for a facile synthesis of nano-silicon/carbon mesoporous composite is proposed. Silicon nanoparticles can be obtained through the magnesium silicide reduction of amorphous silica using high energy mechanical milling process. And mesoporous carbon matrix is fabricated via simple carbon coating method on Si nanoparticles followed by chemical etching of preexisting magnesium oxide nano-particles. This nano-silicon/carbon mesoporous composite electrode shows an excellent electrochemical performance as an anode for lithium ion batteries, achieving a reversible capacity of c.a. 1600 mAh g−1 over 50 cycles at a current of 1.0 A g−1 and superior rate capabilities with reversible capacity of about 1530 mAh g−1 at a discharge current density of 3 A g−1. [Copyright &y& Elsevier]

Abstract: Thin films of manganese oxides have been deposited on Cu foils by radio-frequency (RF) sputtering under different conditions. Crystalline MnO films cannot be obtained but Mn3+/M4+ oxides are formed when the growth proceeds under the Ar atmosphere, due to the oxidation of MnO. While they can be obtained under the Ar:H2 (95:5 vol%) reduction atmosphere at both room temperature and 500 °C. The latter films in thickness of ∼0.5 μm exhibit an initial coulombic efficiency of 75%, reversible capacities of 380 μAh cm−2 μm−1 (∼700 mAh g−1) at 4 μA cm−2 (∼0.05 C) after 100 cycles, and 230 μAh cm−2 μm−1 (∼428 mAh g−1) at 20 C. These values demonstrate that the sputtering-grown MnO films here exhibit excellent cyclability and rate performance in comparison to the reported data of MnO anodes. Pure phase with low oxidation state and certain porosity could be favorable factors accounting for such improved electrochemical performance. [Copyright &y& Elsevier]

Abstract: Magnetite (Fe3O4)/carbon core–shell nanotubes have been successfully synthesized by partial reduction of monodispersed hematite (Fe2O3) nanotubes with carbon coating. Fe2O3 is completely converted to Fe3O4 during the reduction process and a thin carbon layer is continuously coated on the surface of Fe3O4 with the nanotube morphology reserved. The Fe3O4/carbon core–shell nanotubes exhibit superior electrochemical properties as anode material for lithium-ion batteries compared with the Fe2O3 and Fe3O4 nanotubes. The Fe3O4/carbon core–shell nanotubes electrode shows a large reversible capacity up to 938 mAh g−1 as well as improved cycling stability and excellent rate capability. The promising anode performance of the Fe3O4/carbon core–shell nanotubes can be attributed to their tubular morphology and continuous carbon coating, which provide improved structural stability and fast charge transport. [Copyright &y& Elsevier]

Abstract: Tin oxide (SnO2)/graphene composite is synthesized via a simple wet chemical method using graphene oxide and SnCl2·2H2O as raw materials. Graphene of high reduction degree in the composite can provide high conductivity and large-current discharge capacity. SnO2 nanoparticles with dimension around 5 nm are uniformly distributed on the graphene matrix. The SnO2/graphene composite exhibits outstanding electrochemical performance such as high reversible capacities, good cycling stability and excellent high-rate discharge performance. The initial discharge and charge capacities are 1995.8 mAh g−1 and 1923.5 mAh g−1, respectively. After 40 cycles, the reversible discharge capacity is still maintained at 1545.7 mAh g−1 at the current density of 1 A g−1, indicating that the composite is a promising alternative anode material used for high-storage lithium ion batteries. [Copyright &y& Elsevier]

Abstract: Strontium titanate nanoparticles have been synthesized using a combination of sol-precipitation and hydrothermal techniques for subsequent testing as an anode material for lithium-ion batteries. The potentials associated with lithiation are 0.105V and 0.070V vs. Li/Li+ and 0.095V and 0.142V vs. Li/Li+ during de-lithiation. These potentials are significantly lower than the 1.0V to 1.5V vs. Li/Li+ typically reported in the literature for titanates. In an attempt to improve the lithiation and de-lithiation kinetics, as well as capacity retention, SrTiO3 nanoparticles were platinized using a photoinduced reduction of chloroplatinic acid. No significant changes in the morphology or crystal structure of the platinized nanoparticles were observed as a result of the reduction reaction. The voltage profile, charge and discharge kinetics, and cyclability of the platinized SrTiO3 nanoparticles are compared to that of the non-platinized SrTiO3 nanoparticles. [Copyright &y& Elsevier]

Abstract: The composite [Sn–BPO4/xC] to be used as negative electrode material for the storage of electrochemical energy was obtained by dispersing electroactive tin species onto a BPO4 buffer matrix by carbothermal reduction of a mixture of SnO2 and nanosized BPO4. This composite material was thoroughly characterized by X-ray diffraction, Scanning Electron Microscopy, 119Sn Mössbauer spectroscopy and Raman spectroscopy. The electrochemical tests of this new material highlight its very interesting electrochemical properties, i.e., a discharge capacity of 850mAhg−1 for the first cycle and reversible capacity around 585mAhg−1 at C/5 rate. These electrochemical performances are attributed to the very high dispersion and stabilisation of tin metal particles onto the BPO4 matrix. The irreversible capacity observed for the first charge/discharge cycle is due the reduction of interfacial SnII species and to the passivation of the anode surface by liquid electrolyte decomposition (formation of the SEI layer). [Copyright &y& Elsevier]

Abstract: The electrochemical performance of a composite of nano-Si powder and a pyrolytic carbon of polyvinyl chloride (PVC) with carbon nanofiber (CNF) was examined as an anode for solid-polymer lithium-ion batteries. Nano-Si powder was firstly coated with carbon by pyrolysis of PVC and then mixed with CNF (referred to as Si/C@CNF) using a rotation mixer. The composite exhibited good cycling performance, but suffered from a large irreversible capacity loss of which the retention was less than 60%. In order to reduce the loss, a thin lithium sheet was attached to the Si/C@CNF electrode surface as a reducing agent. The irreversible capacity of the first cycle was lowered to as much as 0mAhg−1 and after the third cycle, the lithium insertion and extraction efficiency was almost 100%. A reversible capacity of more than 1000mAhg−1 was still maintained after 40 cycles. [Copyright &y& Elsevier]

Abstract: Core–shell structured, carbon-coated, nano-scale Cu6Sn5 has been prepared by a modified carbothermal reduction method using polymer coated mixed oxides of CuO and SnO2 as precursors. On heat treatment, the mixture oxides were converted into Cu6Sn5 alloy by carbothermal reduction. Simultaneously, the remnants carbon was coated on the surface of the Cu6Sn5 particles to form a core–shell structure. Transmission electron microscope (TEM) images demonstrate that the well-coated carbon layer effectively prevents the encapsulated, low melting point alloy from out flowing in a high-temperature treatment process. Core–shell structured, carbon coated Cu6Sn5 delivers a reversible capacity of 420mAhg−1 with capacity retention of 80% after 50 cycles. The improvement in the cycling ability can be attributed to the fact that the carbon-shell prevents aggregation and pulverization of nano-sized tin-based alloy particles during charge/discharge cycling. [Copyright &y& Elsevier]

Abstract: The geometric parameters of 1, 3-benzodioxol-2-one (BO) and propylene carbonate (PC) was optimized at the B3LYP/6-311++G (d, p) level of density functional theory (DFT) with the polarized continuum models (PCM). The obtained frontier molecular orbital energies and vertical electron affinities indicate that BO is reduced more easily than PC. The transition state (TS) of ring-opening reaction BO −1 →BO −1 was optimized and confirmed by vibrational frequency analysis and intrinsic reaction coordinate (IRC) method. The bond orders and atomic charge distribution of the stable points along the minimum energy path (MEP) were analyzed using the natural bond orbital (NBO) method at the B3LYP/6-311++G(d, p) level of DFT. With these calculated results, the reduction mechanism of BO for the formation of solid electrolyte interface (SEI) film on anode of lithium ion battery can be inferred as: BO+e→BO −1 →BO −1 →⋯→SEI Film. [Copyright &y& Elsevier]

Abstract: In this work, a novel composite consisting of nanosized silicon highly dispersed within the porous, elastic and conductive oxide/carbon matrix has been developed as an anode candidate for lithium ion batteries. The composite was prepared by a mechanochemical reaction between SiO and Li under ball milling followed by a carbon coating using the pyrolysis of poly(vinyl chloride)–co-vinyl acetate. The porous structure can effectively suppress the volume change of silicon during the electrochemically Li-alloying process. No obvious capacity fading was observed up to 100 cycles with a stable capacity of 620mAhg−1. The factors influencing the microstructure and the electrochemical behavior of the composite were discussed. [Copyright &y& Elsevier]

The incorporation of ultrafine SnO 2 particles inside N-doped ordered mesoporous carbon (N-CMK3) is suggested as a method to prepare an ultrastable anode material for Li-ion batteries. Sn nanoparticles formed by chemical reduction of SnCl 4 inside N-CMK3 pores are spontaneously reoxidised by dissolved oxygen, resulting in the formation of ultrafine SnO 2 inside N-CMK3 pores. This SnO 2 @N-CMK3 exhibits superior capacity, cyclability, and rate capability. Over 100 cycles at a rate of 0.1C, SnO 2 @N-CMK3 maintains a specific capacity of 635 mAh g−1, corresponding to a capacity retention of 86.6%. Over 1000 cycles at the rate of 0.5C, SnO 2 @N-CMK3 can deliver a capacity of 433 mAh g−1. At an ultrahigh rate of 5C, SnO 2 @N-CMK3 still delivers a capacity higher than that of commercial graphite. The full cell, composed of an SnO 2 @N-CMK3 anode, LiCoO 2 cathode, and sacrificial Li electrode, presents excellent performance, better than previous reports of Li-ion cells. By employing a sacrificial Li electrode, the issue related to the low Coulombic efficiency of SnO 2 @N-CMK3 in the first few cycles and the pre-lithiation SnO 2 @N-CMK3 electrode can be successfully addressed. Image 1 • Ultrafine SnO 2 particles are filled inside mesopores of N-CMK3. • SnO 2 @N-CMK3 exhibits the reversible capacity of 635 mAh g−1 at the rate of C/10. • An original three-electrode full cell using SnO 2 @N-CMK3 anode is designed. • Sacrificial Li electrode in the full cell improves coulombic efficiency. • The full cell delivers 608 mAh g−1 with 83.8% retention over 200 cycles. [ABSTRACT FROM AUTHOR]