Journal
NANO ENERGY
Volume 64, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.nanoen.2019.103942
Keywords
Aqueous Zn battery; beta-MnO2; Phase evolution; Electrochemistry
Categories
Funding
- National Key R&D Program of China [2016YFB0700600]
- Soft Science Research Project of Guangdong Province [2017B030301013]
- Shenzhen Science and Technology Research Grant [ZDSYS201707281026184]
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Mild aqueous Zn-MnO2 battery attracts lots of attention in energy storage filed due to its low cost, high safety and environmental friendliness. To achieve high-performance in battery, phase evolution processes of MnO2 during synthesis and electrochemical reactions need to be understood. Herein, the phase evolution during microwave hydrothermal and correlated battery performance of beta-MnO2 are studied. The results demonstrate a phase evolution mechanism from an initial mixture of vernadite, nsutite, and pyrolusite (beta-MnO2) to a final single beta-MnO2 phase, along with enhanced structure stability, increased Mn valence, and decreased BET surface area. It is found that only when microwave hydrothermal time (MHT) >= 120 min, beta-MnO2 showing both high capacity and excellent cycling performance can be obtained. beta-MnO2 prepared under a MHT of 120 min shows a high reversible capacity of 288 mA h g(-1) with a median voltage of 1.36 V vs. Zn/Zn2+, and high capacity retentions of 91.8% after 200 cycles at 0.5C and 84.3% after 1000 cycles at 4C, respectively. In addition, the formation of inactive ZnMn2O4 during cycling is observed, which contributes to the capacity fading of beta-MnO2 after long-term cycling. This research makes a step forward to the practical application of ZnMn2O4 batteries, and contributes to the large-scale energy storage field.
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