标题: | 高电容量锡基奈米结构作为锂離子电池之阳极 High Capacity Tin-Based Nanostructures as Anodes for Lithium-Ion Batteries |
作者: | 许凯捷 Hsu, Kai-chieh 裘性天 Chiu, Hsin-Tien 应用化学系硕博士班 |
关键字: | 锂离子电池;奈米材料;锡;氧化锡;碳;Li-ion battery;nanomaterial;SnO2;Sn;Carbon |
公开日期: | 2014 |
摘要: | 此次研究中,我们提出在不使用模板与金属催化剂的环境下,合成出锡基奈米结构,其中包含奈米棒、空球状、奈米片状之二氧化锡以及碳材包覆金属锡之核壳一维奈米线作为阳极材料。此外,本研究也对锡基奈米结构的成长机制以及电化学性质作了详细的探讨。 首先,藉由气固相反应,以氧化钙及四氯化锡作为前驱物,氩气作为载流气体之环境,合成出具有相分离奈米棒之二氧化锡(短轴为10-20奈米长度;长轴为1-2微米长度)及氯化钙盐类。接着,藉由水热法以不同的+4/+2价态锡之前驱物,合成出空球状、奈米片状之二氧化锡,其中空球之壳厚大约为200奈米厚度,球状大小为1-3微米长度;片状为40奈米厚度。根据实验所观察之结果,提出成长机制,藉其尝试了解成长过程。并且进一步讨论,在电化学性质上与不同形貌奈米棒、空球状、奈米片状之二氧化锡之间相关性。电池测试方面,以二氧化锡奈米结构作为电极(充放电速率为100 mA g-1),奈米棒、空球状、奈米片状之二氧化锡经过100次循环充放电分别有435、522以及490 mA h g-1,其效能表现优异,主要原因为二氧化锡具有独特之奈米形貌以及被非活性物质围绕着,故此在充放电过程中,以至于能达到降低材料体积变化之压力。 为了达到更佳效能以及减少不可逆现象,并以锡基为基础的复合材料,故此设计一新颖之锡碳复合奈米材料作为电极材料。我们提出一简单方式制备碳材包覆金属锡之核壳一维奈米线材料。以二氧化锡作为前驱物,通入乙炔气体及氩气作为载流气体之环境成长;其中短轴为100-350 奈米长度;长轴为数十微米长度;碳层为30-70 奈米厚度,并发现管壁中具有中空区域。根据实验所观察之结果,提出一气固相反应的成长机制,藉其尝试了解成长过程。电池测试方面,以碳锡材料作为电极 (充放电速率为100 mA g-1),经过100次循环充放电仍有525 mA h g-1;甚至在快速充放电状况(1000 mA g-1),依然保有486 mA h g-1。因本材料具有独特之一维形貌与中空区域作为体积膨胀之缓冲区域,故其效能之表现优异。 In this studies, we demonstrate the synthesis of tin-based nanostructures include SnO2 nanorods (NRs), hollow spheres (HSs), nanosheets (NSs) and Sn@C core-shell nanowires (NWs) without the usage of template and catalysts. Growth mechanism and electrochemical properties of tin-based samples were also investigated. First, phase-segregated SnO2 nanorods (NRs, length 1-2 m and diameter 10-20 nm) were developed in a matrix of CaCl2 salt by reacting CaO particles with a flowing mixture of SnCl4 and Ar gases at elevated temperatures via a vapor–solid reaction growth (VSRG) pathway. And developed a facile hydrothermal method to synthesize SnO2 hollow spheres (HSs) and nanosheets (NSs). The morphologies and structures of SnO2 could be controlled by Sn+4/+2 precursors. The shell thickness of the HSs was around 200 nm with diameter 1-3 μm, while thickness of the NSs was 40 nm. The correlation between the morphological characteristics and the electrochemical properties of SnO2 NRs, HSs and NSs were discussed. The SnO2 nanomaterials were investigated as a potential anode material for Li-ion batteries (LIBs). SnO2 NRs, HSs and NSs exhibit superior electrochemical performance and deliver 435, 522 and 490 mA h g−1 up to the one hundred cycles at a current density of 100 mA g-1 (0.13 C), which is ascribed to the unique structure of SnO2 which be surrounded in the inactive amorphous byproduct matrix. The matrix probably buffered and reduced the stress caused by the volume change of the electrode during the charge-discharge cyclings. Development tin-based nanocomposites containing suitably chosen matrix elements to achieve higher performance and reduce irreversibility processes. Designed strategy to fabricate a novel tin-carbon nanocomposites as electrodes of LIBs. Sn@C core-shell nanowires (NWs) were synthesized by reacting SnO2 particles with a flowing mixture of C2H2 and Ar gases at elevated temperatures. The overall diameter of the core–shell nanostructure was 100-350 nm. The C shell thickness was 30-70 nm. The NW length was several micrometers. Inside the shell, a void space was found. The reaction is proposed to be via a vapor–solid reaction growth (VSRG) pathway. The NWs were investigated as a potential anode material for Li-ion batteries (LIBs). The half-cell constructed from the as-fabricated electrode and a Li foil exhibited a reversible capacity of 525 mA h g-1 after one hundred cycles at a current density of 100 mA g-1. At a current density as high as 1000 mA g-1, the battery still maintained a capacity of 486 mA h g-1. The excellent performance is attributed to the unique 1D core-shell morphology. The core-shell structure and the void space inside the shell can accommodate large volume changes caused by the formation and decomposition of LixSn alloys in the charge-discharge steps. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079925811 http://hdl.handle.net/11536/75995 |
显示于类别: | Thesis |
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