本研究利用NiCo2S4/還原氧化石墨烯複合電極材料來改善單一NiCo2S4電極在多次充/放電循環後，因其體積膨脹所導致的電容量快速損失。而還原氧化石墨烯因其優異的導電性、高比表面積以及特殊的蜂巢網狀二維平面結構，非常適合用來作為增加電極材料之導電性及結構穩定性，並降低充/放電循環時產生之機械應變之材料。
透過Hummer’s method加上熱處理法製備出蓬鬆分散的還原氧化石墨烯粉末，並使用簡便的一鍋法合成純相之NiCo2S4奈米粒子和NiCo2S4/還原氧化石墨烯複合電極材料。實驗結果可發現我們能通過改變不同參數，如:溶劑添加量、S/陽離子比例、反應時間等，有效控制其粒徑組成與成分組成；在電化學實驗中，NiCo2S4/還原氧化石墨烯複合電極材料在1 A/g電流密度下有962.95 F/g的高比電容表現，而單一NiCo2S4電極只有556.65 F/g；在大電流密度15 A/g下，NiCo2S4/還原氧化石墨烯複合電極材料仍有699 F/g的高比電容表現，保持率為74.3%，而單一NiCo2S4電極只有356.9 F/g，保持率僅剩64%。
最後進行大電流密度(15 A/g)的多次充/放電測試，在經過3000次的循環充放電測試後，NiCo2S4/RGO(~67%)的保持率相較於NiCo2S4(~55%)有顯著的提升，這些結果證實了在添加還原氧化石墨烯之後，能有效減緩其體積膨脹的現象，並增加整體電容量的表現。

In this study, RGO was used to enhance the NiCo2S4 long cycle stability. The conductivity of the NiCo2S4 electrode can be increased and the mechanical strain during charge and discharge cycles is reduced by wrapping RGO with the excellent conductivity, high specific surface area and special 2D morphological structure.
A fluffy RGO was prepared by using the Hummer's method and heat treatment, and NiCo2S4 and NiCo2S4/RGO were synthesized by one-pot method. The electrodes were prepared by deposition of NiCo2S4/RGO and NiCo2S4 slurry onto the nickel foam surface. After 3000 times cycle charge-discharge tests, the capacity retention of NiCo2S4/RGO electrode was ~ 74%, which is superior to NiCo2S4 (~ 55%).
Finally, the as-fabricated asymmetric supercapacitors based on NiCo2S4/RGO//active carbon electrodes demonstrate a high energy density of 31 Wh/kg at a power density of 986.7 W/kg, and can still maintain an energy density of 22.5 Wh/kg at a high power density of 7418 W/kg. It suggests that NiCo2S4/RGO//active carbon electrodes with such high output energies and power densities are highly competitive compared to other recent reports.

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