請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/79076
標題: | 透過噴霧造粒技術製備奈米矽分散於碳表面之鋰離子電池碳矽複合負極材料 Engineering Carbon Surface with Well Dispersed Silicon Nanoparticles via Spray Drying for Lithium Ion Batteries |
作者: | Chang-En Wu 吳昌恩 |
指導教授: | 吳乃立(Nae-Lih Wu) |
關鍵字: | 鋰離子電池,碳矽負極,噴霧乾燥,高分子, Li-ion batteries,Silicon-carbon composite,Spray drying,Polymer, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | 本研究以石墨以及矽為原料,運用一系列鋰離子電池上的知識以及粉粒體的混和、乾燥等技術,搭配充放電測試以及儀器分析驗證材料之各種電化學以及物理化學特性後,合成出具商業化潛力之鋰離子電池碳矽複合負極材料。
由於我們的材料以石墨為基底,一開始我們透過研究高分子的鍍膜對於石墨電化學表現分析上做分析,一方面研究高分子鍍膜之基本方法,我們主要以聚乙烯醇PVA(Polyvinyl Alcohol)為高分子的研究對象,PVA是一個具高黏性,且溶於水可在水中形成良好分散之多羫基親水高分子,另一方面也證實石墨等碳基材料在我們的高分子改質下,不會有劣化之傾向,甚至能夠改進電極表面SEI(Solid Electrolyte Interphase)所帶來之影響,經過PC(Propylene Carbonate)的共嵌入測試更發現,該高分子分布十分均勻,可以有效在第一圈鋰化過程中阻擋PC溶劑化之鋰離子共嵌入進石墨層間,防止形成極大的不可逆電容量以及石墨結構的破壞。 接著以高分子以及石墨研究上的基礎,以小規模實驗製備碳矽複合材料,一開始先在水中分散好奈米矽,再添加入石墨以及高分子的黏著劑,本實驗同樣以聚乙烯醇為黏著劑的基底,同時加入可與聚乙烯醇做交聯反映的交聯劑,在培養皿上進行高溫乾燥,並進一步使用烘箱將水分去除並加速交聯反應的完整性,交聯過後的高分子膜可以在水中維持一定時間的穩定性而不溶解,有利於我們之後進行第二階段改質,由於此高分子膜高溫碳化後殘碳量極低,因此我們在材料外在行鍍上一層殘碳量高的酚醛樹脂,可以確保煅燒後奈米矽仍能保留在石墨表面不脫落。 經過驗證證實了該方法的可行性後,我們進一步使用較大規模的噴霧乾燥製成合成我們的碳矽複合材料,分別以球化天然石墨,KS6片狀石墨以及兩種混和使用漿料來做噴霧乾燥的碳原料,球化石墨噴霧乾燥出來的粉體會判隨著矽小球的產生,實驗顯示對於電性表現有著不好的影響,我們透過密度差的沉降方法加以分離,並得到良好之改進,而KS6石墨噴霧乾燥後產生具孔洞的的二次粒子結構,雖然有著良好的電化學表現,但是振實密度以及電極密度過低,無法進一步實際應用,因此,我們最後一部分將兩種碳材合併使用,並探討兩者比例間不同所造成的影響,最後成功製備出具高振實密度之碳矽複合材料,接著引用前面高分子鍍膜技術以及實驗室其他成員研發之PVDF電極沉浸塗布技術試圖改進材料電性表現。 Our research takes graphite and silicon nanoparticles as ingredients and utilizes a series of knowledge in lithium ion batteries and techniques in particular science such as mixing and drying to synthesize a silicon-carbon anode composite having the potential to commercialization. Our materials are well-studied by advanced instrument and battery tester to fully understand the physical and electrochemical property. At the beginning, we start with the polymer surface modification and examine the effect to pristine natural graphite electrode. We choose polyvinyl alcohol (PVA) as the main character of polymer coating, which is an adhesive, water solution polymer that can form good dispersion in aqueous solution. We want to prove that the polymer coating layer did not bring any drawback and even benefit the SEI formation. Through the propylene carbonate test, we can conclude that the polymer layer is pretty uniform and able to block the co-intercalation of solvated lithium ions. In the following experiment, we firstly made a laboratory scale batch of silicon-graphite composite based on our previous results and experience. By adding well dispersed silicon particles and polymeric PVA binder together with graphite, we successfully acquired silicon-graphite composite having reasonable capacity and performance. Still, we also introduced the usage of another phenolic resin coating. The high carbon yield phenolic resin can help bind silicon particles on carbon surface. After proving the feasibility of this concept, we applied spray drying as our large scale production method. We used three kinds of carbon sources, that is, spherical natural graphite, KS6 flake graphite and both of them. For natural graphite case, silicon balls will form during the spray drying process and it’s detrimental to the electrode. We employed sedimentation method to separate the composite and silicon balls and got good improvement. For KS6 flake graphite case, porous secondary particles formed and exhibited good cycling performance and stability. However, the tap density and volumetric density for KS6 related electrode is way too low to put into real practice. For spray drying using both spherical natural graphite and KS6 flake graphite together, we can obtain composite that provides great support for silicon particles and ideal performance without further purification. Most importantly, the tap density and volumetric density can be maintained at an acceptable value. Followed by some post processing including polymer particle coating and PVDF electrode coating, the performance is expected to be improved. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/79076 |
DOI: | 10.6342/NTU201802948 |
全文授權: | 有償授權 |
電子全文公開日期: | 2023-08-23 |
顯示於系所單位: | 化學工程學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-107-R05524067-1.pdf 目前未授權公開取用 | 8.72 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。