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銅鋅錫硫四元化合物奈米結構應用於高效率鋰離子電池負極材料之研究

Cu_xZn_ySn_zS Nanostructures for Applications on High-performance Li-ion Battery Anode Material

摘要


現今銅鋅錫硫(CZTS)四元材料被廣泛應用於太陽能電池吸收層及電極材料於能源儲存上。儘管被廣泛研究,但仍需要尋找更便宜,更容易的方法來獲得具有獨特結構以及更好的化學和物理穩定性的CZTS為我們主要研究目標。在這項研究中,首先我們優化溶劑熱合成法經由改變操作條件並觀察可變參數(例如:反應溫度,硫脲比例,反應時間及基板是否有修飾)。已知包括CZTS在內的大多數電極材料需具有更好的結晶度,反應穩定性和表面潤濕性於電解質系統。本研究引進奈米環境網結構於我們所開發的銅鋅錫硫薄膜電極中;當基板經由奈米環境網修飾後可使材料具有較佳的機械及化學穩定性,此概念來自於生態工法的修護方式。由於成長的奈米結構本身具有孔洞性,使其能有效釋放電解質於反應過程中所產生的應力;此外使用乙二醇作為我們合成系統的溶劑可使得表面具親水性,應用於電解液為極性溶劑有較佳的潤濕性。基於上述的結構優點,有助於CZTS奈米晶體用於電解質系統(如鋰離子電池)中,具有高比電容和出色的循環穩定性。第二部分將CZTS奈米牆應用於鋰離子電池中,突出了級聯機制,以改善過渡金屬硫化物陽極的鋰離子儲存性能。在400次循環後可達穩定電容量1400mAh g^(-1)於電流密度1000mAg^(-1);此外,CZTS奈米牆的倍率性能也非常出色,可以在1分鐘內充電,並提供495 mAh g^(-1)的電容量。最後經由非臨場X射線衍射(XRD)和X射線光電子能譜(XPS)分析電極充電/放電時晶體結構演變以及氧化態的變化。多元素金屬硫屬元素化物結合、增強與基板黏合的晶種層和最適化的奈米結構設計,是為下一代儲能設備提供超高容量和穩定陽極材料的關鍵。

並列摘要


Nowadays Cu_xZn_ySn_zS (CZTS) is widely used as absorber layer and electrode material for the variety of applications. Despite its popularity, there is still a need to look for a cheaper and easier way to obtain CZTS with its unique structures and better chemical and physical stability. In this study, first we optimize hydrothermal process which used to synthesize the CZTS from a low-cost and abundant source viz. copper, zinc, tin and sulfur precursor and observing the various effects of the variable parameters such as temperature, sulfur ratio, reaction time and step. Most of the electrode materials including CZTS known to require better crystallinity, reaction stability and surface wettability for the electrolyte system. Ecological engineering methods (EEM) inspired nanostructures offers great promises in the fabrication of electrode materials that are difficult to engineer through the conventional approaches. The CZTS nanocrystals with hierarchical structured porous material showed the hydrophilic behavior that helps CZTS nanocrystals to be used in electrolyte system such as lithium-ion batteries with a high specific capacitance and outstanding cycling stability. Second we investigating CZTS nanowalls, a cascade mechanism are highlighted in improving the lithium ion storage performance of transition metal sulfides anodes. An ultrahigh and stable capacity, 1400 mAh g^(-1) at a current density of 1000 mA g^(-1), was achieved over 400 cycles; besides, the rate capability of CZTS nanowalls is also remarkable, which can be charged within 1 min and deliver a capacity of 495 mAh g^(-1). Structural evolutions along with the accompanying changes in the oxidation state upon charge/discharge were monitored by ex-situ X-ray diffraction and X-ray photoelectron spectroscopy. Multi-element metal chalcogenides in conjunction with an adhesion-enhancing seed layer and a rational nanostructure design hold the key to such ultrahigh capacity and stable anode materials for next generation energy storage devices.

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