期刊
ACS APPLIED MATERIALS & INTERFACES
卷 6, 期 20, 页码 17637-17646出版社
AMER CHEMICAL SOC
DOI: 10.1021/am505622c
关键词
manganese dioxide; composite materials; hierarchically porous structures; supercapacitors
资金
- PAPD
- Fundamental Research Funds for the Central Universities
- Natural Science Foundation of Jiangsu Province
- National Natural Science Foundation of China
- State Key Program for Basic Research of China
Hierarchically porous yet densely packed MnO2 microspheres doped with Fe3O4 nanoparticles are synthesized via a one-step and low-cost ultrasound assisted method. The scalable synthesis is based on Fe2+ and ultrasound assisted nucleation and growth at a constant temperature in a range of 25-70 degrees C. Single-crystalline Fe3O4 particles of 3-5 nm in diameter are homogeneously distributed throughout the spheres and none are on the surface. A systematic optimization of reaction parameters results in isolated, porous, and uniform Fe3O4-MnO2 composite spheres. The spheres' average diameter is dependent on the temperature, and thus is controllable in a range of 0.7-1.28 mu m. The involved growth mechanism is discussed. The specific capacitance is optimized at an Fe/Mn atomic ratio of r = 0.075 to be 448 F/g at a scan rate of 5 mV/s, which is nearly 1.5 times that of the extremely high reported value for MnO2 nanostructures (309 F/g). Especially, such a structure allows significantly improved stability at high charging rates. The composite has a capacitance of 367.4 F/g at a high scan rate of 100 mV/s, which is 82% of that at 5 mV/s. Also, it has an excellent cycling performance with a capacitance retention of 76% after 5000 charge/discharge cycles at 5 A/g.
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