The Preparation And The Electrochemical Performance Of Transition Metal Oxide Negative Materials For Lithium Ion Batteries

The capacity and power performance of electrode material are requested to be further improved when the application of lithium ion battery (LIB) is extended to superlarge capacitance energy storage devices and electric vehicles. Transition metal oxides are promising electrode materials for LIBs because of their high specific capacity and better electrochemical performance. The electrochemical performance of electrode materials is very sensitive to its composition, structure and morphology. Through the optimization of the synthesis process, transition metal oxide anode materials with special structure and morphology are prepared. This endows it with excellent electrochemical performance. To this end, we provide some new materials such as mesoporous SnO2 nanosheets materials, special morphology of Co3O4 nanoplates with topochemical transformation,monodisperse SnO2/rGO and Fe3O4/rGO. Scanning electron microscopy(SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), thermogravimetric analysis (EG), XPS, EDS and battery testing system are employed to test the electrochemical and physical properties of materials.1. The major challenge to promote the commercialization of SnO2 anode materials is to construct unique structures and/or composites that could alleviate the volume effect and extend the lifespan. This study develops an efficient synthetic solution for the preparation of mesoporous SnO2 nanosheets, which involves an evaporation-induced selfassembly process and the following thermal treatment. Surfactant F127 is used as the soft template to form abundant cores. The as-prepared sample intrinsically inherits flexible sheet-like structure and porous features, as characterized with XRD, SEM, TEM and BET techniques. Based on these combining structural benefits, the sample is utilized as anode materials for lithium-ion batteries and exhibits excellent Lit storage performance such as large and stable reversible capacity, good rate capability, and especially the outstanding durable cycling life of over 1000 cycles, which meets the demands of practical applications. The structural changes of SnO2 nanosheets are observed from the decomposed electrodes after different electrochemical cycles. Moreover, this synthesis strategy may offer an alternative and universal approach for synthesis of other transitional metal oxides or their binary composites as high-performance anode materials for lithium-ion batteries.2. Coordination polymer (CP) templated synthesis of metal oxides has been researched intensively for applications in enhanced electrochemical energy storage and improved catalytic activity. In this manuscript, we demonstrate, for the first time, a topochemical transformation route to synthesize novel layered Co3O4 nanoplates using lamellar structured cobalt-based CPs as a template for optimized lithium-ion battery applications. Endowed with the synergistic advantages of 2D layered textural features and highly exposed reactive (111) crystal planes, the Co3O4 nanoplates exhibit remarkably enhanced lithium storage performance, including fast and high level lithium storage (852 mAh g-1 at 500 mA g-1 after 100 cycles), good rate capability (597 mAh g-1 at 1000 mA g-1 after 100 cycles) and stable cyclability (up to 200 cycles).3. We present a facile and friendly wet chemical method to prepare monodisperse SnO2 nanocrystals assembled on reduced graphene oxide (rGO). Aided with sodium dodecyl sulfonate, small SnO2 nanoparticles (-5 nm) are deposited onto the flexible support evenly and tightly. A cheap compound, urea, is used for the controlled precipitation of SnO2 and the reduction of graphene oxide. When tested as the anode material, the hybrid composite electrode delivers excellent cyclability at high current density, such as high reversible capacity over 1000 mAh g-1 after 400 cycles at 0.5 A g-1 and-560 mAh g-1 after 400 cycles at 1Ag-1. The composites also exhibit superior rate capability varying from 0.! to 4 A g-1, and possess capacity of 423 mAh g-1 at 4Ag-1. This synthesis strategy seems to be suitable for industrial production and can also be extended to produce a variety of metal oxide/rGO composites.4. A simple one-pot hydrothermal approach is employed for the fabrication of Fe3O4/reduced graphene oxide (rGO) nanocomposite as the superior anode material for lithium ion batteries (LIBs). The reduction of graphene oxide sheets into rGO is achieved successfully during the hydrothermal process. The well-dispersed Fe3O4 nanoparticles are decorated on the surface of rGO sheets densely and homogeneously. With the introduction of rGO, the Fe3O4/rGO nanocomposite exhibits significant improvement in the reversible capability, cycling stability and rate performance in comparison with bare Fe3O4, delivering a high capacity of 884 mAh g-1 at a current density of 200 mA g-1 after 100 cycles. This hybrid composite is a potential candidate as anode material of high performance rechargeable lithium ion batteries.