Yongpeng Cui,Huanlei Wang,Nan Mao,Wenhua Yu,Jing Shi,Minghua Huang,Wei Liu,Shougang Chen,Xin Wang
The increasing demand for supercapacitors with high energy and power density has attracted extensive attention in designing advanced carbon materials with high accessible surface area, hierarchical porosity , and 2D/3D morphology. Here, we report a new approach to tune the morphology and structure of the nanocarbons by using methyl cellulose as the precursor. Due to the varying effect of different activating agents, the interconnected sheet-like carbon with a high surface area of up to 2285 m 2 g −1 and a thickness down to ∼4 nm can be obtained. These important characteristics make the nanocarbons demonstrate a high capacitance of 144 F g −1 at 1 A g −1 and 20 °C, and an excellent capacitance retention ratio of 64% at 100 A g −1 in ionic liquid . Because of the high fraction of meso/macropores for nanocarbons, an outstanding capacitance of 116 F g −1 can be achieved at 0 °C, with a high capacitance retention ratio of 39% at 100 A g −1 . A high energy of 16–17 and 9–10 W h kg −1 can be maintained at 20 and 0 °C when the supercapacitor is charged in less than 1s. The excellent electrochemical response of nanocarbons suggests that the proposed preparation process is promising for developing advanced carbon electrodes.
Reasonable structure design and component selection are crucial to electrochemical performance of supercapacitor electrode materials. Sodium alginate (SA), with a novel structure which can immobilize multivalent metal cations, was used to coordinate with Fe3+ to fabricate a carbon and Fe3O4 composite by an easy sol–gel method. Due to the chelation effect between SA and Fe3+, the carbon composite was constructed into a two-dimensional sheet-like structure, and the Fe3O4 particles were nanosize and homogenously distributed on the surface of the carbon nanosheet. As an electrode material for supercapacitors, the composite electrode showed a high specific capacitance of 550 F g−1 at 1 A g−1 in the potential range from −1.1 to 0 V, and excellent cycling stability of 89% retention after 2000 cycles. The enhanced electrochemical performance could be attributed to the abundant exposed active sites, producing high pseudocapacitance, to the two-dimensional nanosheet structure, facilitating electrolyte transport and to the strong attachment strength, improving cycle life. This environmentally-friendly design can provide an alternative to existing methods, resulting in the development of a two-dimensional carbon/metal oxide composite for energy storage devices.
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