Tin-based Nanomaterial: Synthesis And Application As Anode Material Of Lithium-Ion Batteries

New anode materials for lithium-ion batteries with long cycle life and high capacity are needed urgently to meet the demands of portable electronic device and electric vehicles (or hybrid electric vehicles). Owing to the high theoretical gravimetric lithium storage capacity, tin-based lithium storage materials have been considered as one of the most promising alternative anode materials instead of carbon in lithium-ion batteries. However, the large volume change of the tin-based materials often causes a drastic pulverization problem during the lithiation/ delithiation process, which leads to the rapid deterioration and low retention of the capacity. Recent researches indicate that the use of tin-based nanostructures can solve the above-mentioned problem to a large extent. Therefore, the simple, large-quantity synthesis of tin-based nanomaterials is of great significance.In the dissertation, a rich variety of tin-based nanostructures and their nanocomposites have been generated through a solution-phase route. After that, their formation mechanism has been discussed. Moreover, the as-synthesized tin-based nanostructures and their nanocomposites have been applied as anode materials of lithium-ion batteries. The main innovative results are listed as follows:(1) Several kinds of SnS2 nanostructures including ultrathin hexagonal SnSi nanosheets and flower-like SnS2 nanostructures have been synthesized through a hydro/solvothermal route. Among them, the ultrathin hexagonal SnS2 nanosheets with well-defined layered structure exhibited a highly reversible lithium storage performance as an anode material of lithium-ion batteries with excellent capacity retention of 96% after 50 cycles, which was much better than that of graphite and other SnS2 nanostructures.(2) Various of nanocomposites consisting of tin sulfide and carbon nanomaterials including SnS/C nanostructure, SnS2@MWCNTs coaxial nanocables and SnS2/graphene nanocomposites have been achieved. The electrochemical studies indicated that compositing tin sulfide with carbon nanomaterials provided a promising structure with improved lithium storage performance. The capacity of SnS2/graphene nanocomposites remained 903 mAh g-1 after 50 cycles. (3) A chemical reduction method has been developed to assemble and anchor CoSn3 nanoparticle uniformly on the surface of MWCNTs through a polyol route. The electrostatic attraction between the charged species played a vital role in the formation of CoSn3-MWCNTs nanohybrids. The combining of MWCNTs could hinder the agglomeration, enhance electronic conductivity of the active materials, thereby result in enhanced cycling performance. However, the large surface area and small size of the as-synthesized nanomaterials might reduce the initial Coulombic efficiency.(4) One-dimensional TiO2(B) and y-Fe2O3 nanomaterials were uniformly coated with SnO2 nanoparticles via a facile wet chemical route, and then used as anodes of lithium-ion batteries. High reversible capacity, cyclability and initial Coulombic efficiency were achieved from y-Fe2O3@SnO2@C core-shell nanorods. During the lithiation/delithiation process, nanostructured metallic Fe made extra Li2O (from SnO2) reversibly convert to Li+. This nanocomposite showed improved initial Coulombic efficiency of 73% and excellent capacity retention of 879 mAh g-1 after 60 cycles. This result indicated that y-Fe2O3@SnO2@C core-shell nanorods were good candidates as anodes of lithium-ion batteries.