Highly Oxidized Graphene Anchored Ni(OH)2 Nanoflakes as Pseudocapacitor Materials for Ultrahigh Loading Electrode with High Areal Specific Capacitance

详细信息    查看全文

• 作者：Yongfu Tang ; Yanyan Liu ; Wanchun Guo ; Teng Chen ; Hongchao Wang ; Shengxue Yu ; Faming Gao
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：October 30, 2014
• 年：2014
• 卷：118
• 期：43
• 页码：24866-24876
• 全文大小：698K
• ISSN：1932-7455

文摘

The contact between Ni(OH)₂ and graphene oxide (GO) determines the specific capacitance, high-rate performance, and stability of Ni(OH)₂-GO composites when they were used as capacitive materials with high/ultrahigh material loading. To improve this contact, the exfoliated GO from Hummers鈥?method is oxidized twice for anchoring Ni(OH)₂ nanoflakes. The X-ray photoelectron spectroscopy (XPS) results reveal that the further oxidation process increases the carbonyl (C鈥揙) groups and oxygen content on the GO surface. The Ni(OH)₂-GO composites were obtained through a simple hydrothermal process. Morphology and microstructure characterizations indicate that the further oxidation of GO improves the affinity of Ni(OH)₂ and GO via the increased surface groups on the GO. Due to the high conductivity and suitable structure, the Ni(OH)₂ anchored on the treated GO (Ni(OH)₂/TGO) exhibits good capacitive performance and high areal specific capacitance. The Ni(OH)₂/TGO exhibits high specific capacitance of 1236.4 F g^鈥? at 1.0 mV s^鈥? and 1374.8 F g^鈥? at 0.1 A g^鈥?, respectively, which is higher than that of Ni(OH)₂ on the untreated GO. The capacitance retention of Ni(OH)₂/TGO is 52.2% even at 10 A g^鈥?, which is higher than that of Ni(OH)₂/GO (48.8%). For the high conductivity, the specific capacitance is still 996.2 F g^鈥? at 1.0 A g^鈥? even with ultrahigh material loading of 12.48 mg cm^鈥?, which can be transferred to 12.06 F cm^鈥? calculated by areal specific capacitance. Furthermore, low deterioration is observed in Ni(OH)₂/TGO (8.8% loss) after 1000-cycle charge鈥揹ischarge test at 1.0 A g^鈥?, which is lower than that of Ni(OH)₂/GO (19.5% loss). The asymmetric supercapacitor, using the Ni(OH)₂/TGO and activated carbon as the positive material and negative material, respectively, exhibits high energy density of 22.5 Wh kg^鈥? at 86.3 W kg^鈥? and 17.8 Wh kg^鈥? even at 4.05 kW kg^鈥?.