Preparation Of Carbon - Composite Tin - Based Nanomaterials And Its Application In Anode Materials Of Lithium Ion Batteries

In recent years, the anode materials of commercial lithium-ion batteries (LIBs) are graphite-based carbon materials. However, carbon-based material with low specific capacities can not meet the performance requirements of electric vehicles and energy storage devices. Therefore, it is highly desirable to search for alternative anode materials with high specific capacities to replace the carbon anodes. Owing to their high specific capacities, tin-based materials have been considered to be ideal anodic candidates for advanced LIBs with high energy-density and power density. However, the practical application of tin-based anodes has been hampered primarily by their huge volume expansion-contraction during cycling, which leads to the pulverization, loss of electrical contact, and fast capacity fading. The composites of carbon and tin-based nanomaterials possess the superiorities of both nanomaterials and carbon materials, and are expected to meet the performance requirements of advanced LIBs.In this thesis, we focus on the tin-based anodes, including SnS2, SnO2, and tin-based alloys. Specifically, we have prepared a series of nanocomposites of carbon and tin-based materials through facile chemical reaction, using three-dimensional (3D) mesoporous carbon as a matrix, Sn nanospheres and SnCl4/K2Ni(CN)4cyanogel as precursors, respectively. Owing to their unique structural and compositional features, the as-prepared nanocomposites of carbon and tin-based materials manifest enhanced lithium-storage performance. The main innovative results are displayed as follows:(1) By using3D mesoporous carbon as a novel matrix, we have prepared mesoporous carbon-suppored SnS2nanosheets through a facile sonochemical route. Compared with bare SnS2sample, the mesoporous carbon-supported SnS2nanosheets integrates the structural characteristics of both two-dimensional (2D) nanosheet and3D porous carbon matrix, and is thus exhibit improved capacity retention, high capacities, and rate capability. For example, the mesoporous carbon-supported SnS2nanosheets is able to deliver a high reversible capacity of428.8mAh g-1at a current density of100mA g-1after50cycles.(2) By using Sn nanospheres as precursors, we have prepared SnO2@C yolk-shell spheres after silica coating, oxidation, PVDF pyrolysis, and etching processes. Compared with bare SnO2spheres, SnO2@C yolk-shell spheres exhibits improved capacity retention, high capacities, and rate capability. For example, the SnO2@C yolk-shell spheres is able to deliver a high reversible capacity of515.2mAh g"1at a current density of100mA g-1after30cycles. Even at high current densities of500and1000mA g-1, high reversible capacities of395.8and307.5mA h g-1can still be delivered, respectively.(3) By using SnCl4/K2Ni(CN)4cyanogel as a precursor, we have prepared3D porous Sn-Ni@C nanocomposites through a facile chemical reduction and subsequent glucose hydrothermal carbonization approach. Owing to its unique structural characteristics, the3D porous Sn-Ni@C nanocomposites exhibit excellent cycling performance, high specific capacity and rate capability. For example, the discharge capacity of3D porous Sn-Ni@C nanocomposites maintains at440.0mAh g-1at a current density of200mA g-1after40cycles.