L.J. Fu

Natural graphite coated by Si nanoparticles as anode materials for lithium ion batteries

Nano-sized crystalline silicon particles, prepared by a laser-induced vapour deposition method, were coated onto the surface of particles of a modified natural graphite (SSG) by sonicated dispersion and a subsequent heat-treatment process. The microstructure of the Si-coated SSG was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the nanometer-scale Si particles were uniformly and completely coated on the surface of SSG particles, and both the Si and SSG particles existed in the crystalline state. The Si-coated SSG exhibits a much higher reversible capacity than pristine SSG, while keeping the good cycling performance of SSG material. The higher capacity can be ascribed to the alloying of Si with lithium. Because of the heat-treatment at 600 °C, used to achieve a good combination of Si with the SSG base, the cycling of the composites is very satisfactory. As a result, Si-coated SSG is a promising anode material for lithium ion batteries.

Core-shell Si/C nanocomposite as anode material for lithium ion batteries

We report an effective method for the synthesis of a core-shell Si/C nanocomposite, and its application as anode material for lithium ion (Li-ion) batteries. Polyacrylonitrile (PAN)-coated Si nanoparticles are formed by emulsion polymerization, and this precursor is heat-treated under argon to generate a Si/C core-shell nanocomposite. The conductive carbon shell envelops the silicon nanoparticles and suppresses aggregation of the nanoparticles during cycling. Meanwhile, the carbon shell combines closely with the nanocores, and significantly enhances the kinetics of lithium intercalation and de-intercalation, as well as the apparent diffusion coefficient of Li-ions. Consequently, the core-shell Si/C nanocomposite exhibits better electrochemical performance than pure Si nanoparticles, indicating that this is a promising approach to improve cyclability and kinetics of nano-anode materials for Li-ion batteries.

Effects of carbon coatings on nanocomposite electrodes for lithium-ion batteries

Nanocomposites of LiFePO 4 and TiO 2 coated with carbon were prepared by different methods. They exist in the forms of olive and rutile, respectively. Results from cyclic voltammetry show that the carbon coating markedly enhances the reversibility and kinetics of lithium intercalation into and deintercalation from the active materials. Both kinds of carbon coated nanocomposites exhibited better electrochemical performance than their pure counterparts due to the favorable carbon coatings, which provide passages for lithium ions, promote charge transfer, and prevent phase changes.

Nanostructured anode materials for Li-ion batteries

This paper focuses on the latest progress in the preparation of a series of nanostructured anode materials in our laboratory and their electrochemical properties for Li-ion batteries. These anode materials include core-shell structured Si nanocomposites, TiO2 nanocomposites, novel MoO2 anode material, and carbon nanotube (CNT)-coated SnO2 nanowires (NWs). The substantial advantages of these nanostructured anodes provide greatly improved electrochemical performance including high capacity, better cycling behavior, and rate capability.

Changes of LiCoO2 Cathode Material for Lithium-Ion Battery during Long Cycling

Changes of the cathode material LiCoO 2 of our homemade lithium-ion batteries with good uniformity, high capacity, and good cycling were investigated after 500, 1060, and 1600 cycles. The results show clearly that the cathode partially contributes to capacity fading of lithium-ion batteries due to two factors: (i) reactions between the electrolytes and LiCoO 2 , which produce a continuously growing surface layer on the cathode, leading to the increase of the charge transfer resistance, and (ii) the fading of LiCoO 2 structure. These results provide valuable clues to extend the cycling life for lithium-ion batteries.

Surface Active Sites: An Important Factor Affecting the Sensitivity of Carbon Anode Material towards Humidity

We report that various kinds of active sites on graphite surface including active hydrophilic sites markedly affect the electrochemical performance of graphite anodes for lithium-ion batteries under different humidity conditions. After depositing metals such as Ag and Cu by immersion and heat-treating, these active sites on the graphite surface were removed or covered and its electrochemical performance under the high humidity conditions was markedly improved. This suggests that lithium-ion batteries can be assembled under less strict conditions and provides a valuable direction toward lowering the manufacturing cost for lithium-ion batteries.