導電奈米纖維複合碳黑/石墨烯應用於鋁離子電池之研製

Abstract

可充電式之多價金屬離子電池由於具有高理論比電容值和較低之成本而受到廣泛的關注，其中，鋁具有存量豐富，安全性高，對環境友善和利用三電子進行氧化還原反應之高體積容量等優勢，被認為是下一代可充電電池的有力候選人。 本論文以SU-8 2050厚膜光阻為材料，使用黃光微影技術於尺寸2×2 cm2之鉬箔上製作SU-8圓柱陣列結構，並以靜電紡絲技術製備SU-8紡絲奈米纖維。接著透過靜電紡絲技術製備SU-8紡絲奈米纖維。再以兩段式升溫之高溫碳化製程將SU-8光阻轉變為類玻璃碳材料(Glassy carbon)，完成直徑32 µm、深寬比5、間距80 µm之導電碳圓柱陣列結構以及線徑910 nm之碳奈米纖維(Carbon nanofiber)之製備。後續將碳奈米纖維以均質機破碎後，與石墨烯(Graphene)和碳黑(Carbon black)藉由NMP@PVDF黏著劑複合形成鋁離子電池陰極之電極漿料，並滴塗於導電圓柱陣列電極中，完成全碳之鋁離子電池陰極之製作。本論文選擇8組不同漿料用於製備鋁離子電池的陰極，包括未添加碳奈米纖維的漿料，以石墨烯：碳黑=1:0、1:1、1:5、1:8之比例製備四組電極，並於相同之石墨烯與碳黑比例下額外添加碳奈米纖維，再製備出石墨烯:碳黑:碳奈米纖維=1:0:0.5、1:1:0.5、1:5:0.5、1:8:0.5等四組電極。將電極均組裝成鋁離子電池元件後，透過恆電位儀進行循環伏安曲線(Cyclic voltammetry curve, C-V curve)測試以及恆電流充放電(Galvanostatic charge/discharge, GCD)之測試，評估電池之性能。量測結果發現，添加碳奈米纖維之四組電極的C-V 曲線面積，分別比未添加纖維之四組提升了660%、57%、-17%、314%。除石墨烯:碳黑:碳奈米纖維=1:5:0.5電極之C-V曲線面積有小幅度下降外，其餘電極之C-V 曲線面積均有大幅度提升，說明添加碳奈米纖維能夠提供更多比表面積供鋁離子嵌入與嵌出，進而提升電池效能。將上述8組電極所組裝而成之鋁離子電池中，選取性能較好之石墨稀:碳黑=1:1、1:5與石墨烯:碳黑:碳奈米纖維=1:0:0.5、1:1:0.5、1:5:0.5、1:8:0.5六組電極，以100 mA/g之電流密度進行恆電流充放電測試，並計算其比電容值，分別得到3.5、2.5、8.25、14、5、4 mAh/g的結果。其中，石墨烯:碳黑:碳奈米纖維=1:1:0.5之電極具有最高的充電比電容值12 mAh/g，以及放電比電容值14 mAh/g，並且具有85.7%之庫倫效率。此外，石墨烯:碳黑:碳奈米纖維=1:1:0.5與1:5:0.5兩組電極之比電容值，分別達到未添加碳奈米纖維電極的4倍與2倍。Rechargeable multivalent ion batteries rechargeable multivalent ion batteries have attracted intensive attention due to their high theoretical capacities and low cost. Among them, aluminum is considered as a promising electrode candidate for rechargeable batteries because of its low cost, safety, environmental friendliness, and high volumetric capacity based on three-electron redox reaction of Al ions. This study used 2×2 cm2 Mo foil as substrate, and used the lithography process to prepared an cylindrical microstructure array by SU-8 2050 thick-film photoresist. Nano spinning fiber was prepared by electrospinning technique using a SU-8 concentration ratio of SU-8 : thinner=5:1 as a spinning solution. Then the cylindrical microstructure array and the nano spinning fiber were transformed into glassy carbon material by a two-stage high temperature carbonization process. The aspect ratio of conductive carbon cylinder array was more than 5(diameter 32 µm, height 170 µm) and the diameter of carbon nanofibers(CF) were 910 nm. Carbon nanofibers were crushed uniformly by clarifixator to prepare a slurry which compound with graphene(GN) and carbon black(CB). The carbon nanofibers were compounded with graphene and carbon black by an NMP@PVDF adhesive to form electrode slurry of the cathode of the aluminum-ion battery, and were drop coating to the conductive cylindrical array electrode to finish the cathode of the all-carbon aluminum ion battery. In this research, 8 different slurries were selected for the preparation of cathodes for aluminum ion batteries, including graphene: carbon black = 1:0, 1:1, 1:5, 1:8 and graphene: carbon black: carbon nanofibers =1:0:0.5, 1:1:0.5, 1:5:0.5, 1:8:0.5. After assembling the electrodes into aluminum-ion batteries, cyclic voltammetry curve (C-V curve) test and galvanostatic charge/discharge (GCD) test were used to evaluate the performance of batteries by potentiostat. The measurement results showed that the C-V curve area of the four groups with carbon nanofibers increased by 660%, 57%, -17%, and 314%, respectively. This result improved that adding of carbon nanofibers provided more space for intercalation and deintercalation of Al-ions. 6 samples of electrode formulations with better performance: graphene:carbon black=1:1, 1:5 and graphene:carbon black:carbon nanofibers=1:0:0.5, 1:1:0.5, 1:5:0.5, 1:8:0.5 assembled into aluminum ion batteries and galvanostatic charge/discharge test was performed at a current density of 100 mA/g. The specific capacitance values of the six batteries were 3.5, 2.5, 8.25, 14, 5, 4 mAh/g, respectively. Among them, the electrode formulation with graphene:carbon black:carbon nanofibers=1:1:0.5 has the highest charge and discharge specific capacitance value, 12 mAh/g and 14 mAh/g. Its coulombic efficiency was 85.7%. In addition, the specific capacitance of the two groups of graphene:carbon black:carbon nanofibers=1:1:0.5 and 1:5:0.5 were 4 times and 2 times higher than the electrode without carbon nanofibers.