| At present, the problems of energy crisis became more serious and already prompted researchers to chase for renewable resources such as wind, solar energy to replace coal, petroleum, gas and other fossil fuels which are non-revewable and always impart contamination to environment. Effective, low-cost and environment-friendly energy storage devices had received extensive investigation all over the world. Among them, due to lots of advantages of high energy density, broad operation voltage, excellent safety and cycling stability, lithium ion batteries (LIBs), representatives of modern and high-performance energy devices, have been applied in various fields of life, including cells, note computers, mobile power supply. In order to meet requirements of higher-power apparatus such as electric vehicles, smart electric networks and wearable electric devices, LIBs with higher specific capacity and better safety are needed. The improvement of LIB properties strongly pertains to electrode materials. As one important part of batteries, anode materials attract more and more attention from researchers. Graphite-based materials serve as traditional anode of LIBs and only offer theoretical capacity of 372 mA h g-1, far lower than that of metal oxides (generally higher than 600 mA h g-1). However, because of low electric conductivity, serious volumetric changes always happen during processes of lithium ion extraction/insertion, causing aggregation and pulverization of electrode materials. Nanotechnoloy can effectively adjust microstructures and size of metal oxides and thus modify the corresponding electrochemical behaviors. As a result, to develop and design metal oxide with tunable hierarchical structures as anode materials is essential.In the thesis, we aimed to construct anode materials of LIBs with desired micro/nanostructures based on facile strategy and supply some experience for future study of LIBs. The exact contents can be outlined as follows:(1) Zn0.33Co0.67CO3 twin microspheres and cubes had been fabricated via tuning the amount of NH4HCO3 applied in solvothermal system, followed by annealing at 600℃ for 6 h in air to obtain respective porous ZnCo204 micro/nanostructures retaining’parental morphology. We also studied the time-dependent samples by detecting the structure and phase. The formation mechanism was proposed to explain the growth of Zno.33Co0.67C03, namely multistep spitting-in situ dissolution-recrystallization. When evaluated as anode, both ZnCo2O4 twin microspheres and cubes show excellent rate performance and long cycling stability. In testing of rate performance, tt current density of 10 A g1, specific capacity of ZnCo2O4twin microspheres is 790 mA h g-1. When the current density continuously decreased to 0.5 A g-1, reversible specific capacity can reach as high as 1260 mAh g-1 as cycling continued to 550 cycles. At 5.0 A g-1, reversible specific capacity can be retained to 550 mA h g-1 as it carried out to be 2000 cycles.(2) With n-pentanol as solvent, multilayered Zno.33Coo.67C03 bipyramid nanoframes had been produced by solvothermal method. Through calcinatations in N2 and air at 600℃ for 6 h, respectively, hierarchical ZnO/CoO and ZnCo2O4 with mesoporous structures were finalized, which could well maintain the overall morphology of their respective maternal precursors. The formation process was investigated by monitoring intermediates collected at different reaction duration. ZnO/CoO and ZnCo204 were detected as anode materials of LIBs with Li as reference electrode. Results demonstrate that they both afford good electrochemical performance, possibly originating from porous multilayered micro/nanostructures. Moreover, the cycling stability of ZnO/CoO is better than ZnCo2O4. ZnO and CoO nanoparticles were formed homogeneously with even distribution. However, the crystal structure of ZnCo2O4 partially collapsed after the first discharge cycle. |
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