Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 10, Issue 11, Pages 9398-9406Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.7b18762
Keywords
cycling stability; morphology evolution; Al-doped MnO2; supercapacitor; in situ NMR
Funding
- Natural Science Foundation of China [21503065, 51672065]
- General Financial Grant from the China Postdoctoral Science Foundation [2015M571924]
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In this work, Al-doped MnO2 (Al-MO) nanoparticles have been synthesized by a simple chemical method with the aim to enhance cycling stability. At room temperature and 50 degrees C, the specific capacitances of Al-MO are well-maintained after 10 000 cycles. Compared with pure MnO, nanospheres (180.6 F g(-1) at 1 A g(-1)), Al-MO also delivers an enhanced specific capacitance of 264.6 F g(-1) at 1 A During the cycling test, Al-MO exhibited relatively stable structure initially and transformed to needlelike structures finally both at room temperature and high temperature. In order to reveal the morphology evolution process, in situ NMR under high magnetic field has been carried out to probe the dynamics of structural properties. The Na-23 spectra and the SEM observation suggest that the morphology evolution may follow pulverization/reassembling process. The Na+ intercalation/deintercalation induced pulverization, leading to the formation of tiny MnO, nanoparticles. After that, the pulverized tiny nanoparticles reassembled into new structures. In Al-MO electrodes, doping of Al3+ could slow down this structure evolution process, resulting in a better electrochemical stability. This work deepens the understanding on the structural changes in faradic reaction of pseudocapacitive materials. It is also important for the practical applications of MnO2-based supercapacitors.
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