非對稱式超級電容器是一種兼具高功率密度與高能量密度的一新型儲電元件，主要是利用正極與負極材料之工作電位互補進而獲得更高的工作電位，並且結合擬電容與電雙層電容兩者優點，而得到更高的能量密度與功率密度，成為近年來在儲電元件中，熱門研究議題。
在電池業界上，活物重量往往佔不到總體重量的50%，因此造成過多不必要的重量或是必須增加電池串聯數量來達到高能量密度輸出，因此開發極輕薄電極便是使超級電容邁向更高效能的關鍵。本研究利用靜電紡絲技術製備聚丙烯腈奈米，再經熱處理後得到碳奈米纖維，相較於市售之碳布重量降低98.5%，且具有良好電化學特性與導電性。
在負極電極材料，本實驗係由微波電漿化學氣相沉積法製備直立式石墨奈米牆，在1M 硫酸電解液下，當電流密度為 1 A/g其電容值表現為286 F/g；且在經過5000次充放電後其電容值保持約95%以上；而在1M 氫氧化鉀電解液下，當電流密度為 1A/g其電容值表現為225 F/g。
在正極電極材料，利用電沉積方式沉積氫氧化鎳鈷水合物，並以石墨奈米牆作為中間導電層提升導電度，使得氫氧化鎳鈷水合物在進行氧化還原反應時可以擁有完整的氧化還原峰且並不歪斜。利用電流密度0.25 mA/cm2進行電沉積與1250秒電沉積時間具有最佳電容值表現，在1M 氫氧化鉀電解液下，當電流密度為 1A/g其電容值表現為131 F/g。並也利用最佳電沉積條件針對氫氧化鎳鈷水合物、氫氧化鎳和氫氧化鈷進行穩定性測試，氫氧化鎳鈷水合物因為有穩定性較高之Co2+摻入結構中，因此抑制了Ni(OH)2之相轉變，而可以擁有較氫氧化鈷高之電容值外，其穩定性也相當好。
利用上述正極與負極電極設計非對稱式超級電容器，可將工作電位擴充至1.6 V，且循環伏安法與充放電圖呈現對稱，並無其他反應發生。在電流密度0.5 A/g下，其能量密度達16.8 W h/kg且功率密度為370 W/kg；在電流密度5 A/g下，其能量密度達13.9 W h/kg且功率密度為3690 W/kg，將結果整理在Ragone Plot上可以看到成功提高能量密度。

Asymmetric supercapacitor is a kind of novel energy storage devices, which has high power density with high energy density. Asymmetric supercapacitor not only takes the two different working potential of positive electrode and negative electrode to enlarge the cell operating potential, but also combines the advantages of electric double layer capacitors and pseudocapacitors to enhance the energy density and power density. Nowadays, the asymmetric supercapacitor has been become popular research topic in energy storage devices.
In this study, we use the electrospining technology to produce the polyacrylonitrile nanofiber and two steps of heat treatment to produce high quality carbon nanofiber serves as ultralight substrate of electrode.
The vertically-aligned graphite nanowalls (GNWs) were fabricated on electrospun carbon nanofibers via microwave plasma-enhanced chemical vapor deposition. When utilizing GNWs as the electrode matericals of supercapacitors, the specific capacitance of value 286 F/g and 225 F/g can be achieved at current density 1 A/g in 1M H2SO4 and 1M KOH, respectively. After 5000 cycles of charge and discharge, the retention of capacitance still maintains 95%.
Electrodeposition method was used to deposit the binary nikel-cobalt hydroxides on the GNWs as positive electrode. The specific capacitance value of 131 F/g can be achieved at current density 1 A/g in 1M KOH. Because of the presence of Co2+ depress the capacity loss is reduced during long charge and discharge, the specific capacitance still maintains 94% after 2000 cycles.
The asymmetric supercapacitor with a positive electrode of NixCo1-x(OH)2 and negative electrode of GNWs shows a superior energy density of 16.8 W h/kg with a power density 370W/kg at a current density of 0.5 A/g; while an energy density of 13.9 W h/kg with a power density 3690W/kg at current denity 5 A/g.

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