| Summary: | 碩士 === 國立中央大學 === 化學工程與材料工程學系 === 102 === As energy storage devices, lithium-ion batteries are extremely important power sources for various portable electronic devices and electric vehicles in modern society. Tin sulfide (SnS2) is low-cost, low toxicity, and high capacities (theoretical capacity：645 mAh/g), it has become one of the most promising anode materials to replace the already commercialized graphite (theoretical capacity：372 mAh/g) in the next generation of lithium ion batteries, and has attracted intensive research interest. Unfortunately, the main drawback of this system stems from the poor conductivity and a drastic pulverization problem due to the large volume change during the lithiation/delithiation process, leading to a high level of irreversibility (i.e, low columbic efficiency) and poor cycle life.
In this study, the different surface morphology of SnS2 powders is prepared by a simple hydrothermal and solvothermal route with different solvents. The powders which use ethylene glycol and DI water as solvent are nanostructures composed of aggregates. However, the powder which uses ethanol as solvent shows many 3D flowerlike microspheres with diameter of 1－2 μm that are composed of hundreds of nanosheets with thicknesses of 60¬－70 nm. Compared to previous two powders, the 3D flowerlike microspheres with hundreds of nanosheets can alleviate the volume change during the lithiation/delithiation process. At a constant current of 300 mA/g (0.47 C) , the 3D flowerlike microspheres exhibit reversible capacity of 414 mAh/g after 100 cycles with the retention of 76 %.
The powder which uses ethanol as solvent synthesized at 100 oC, can effectively reduce thickness of nanosheets with 20－40 nm. It not only can alleviate the volume change during the lithiation/delithiation process but also reduce the internal resistance, improving the electrochemical performance at high C-rate. At a constant current of 300 mA/g (0.47 C) , it exhibits reversible capacity of 460 mAh/g after 100 cycles with the retention of 84 %.And at a high constant current of 5000 mA/g (7.75 C) , it can provide the reversible capacity of 285 mAh/g. Therefore, both of the 3D flowerlike microspheres structure and a decrease of thickness can improve the electrochemical performance.
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