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8060995 
Journal Article 
Bivalence Mn5O8 with hydroxylated interphase for high-voltage aqueous sodium-ion storage 
Shan, X; Charles, DS; Lei, Y; Qiao, R; Wang, G; Yang, W; Feygenson, M; Su, D; Teng, X 
2016 
1 
Nature Communications
EISSN: 2041-1723 
7 
1 
13370 
English 
27845345 
WOS:000387971900001 
Aqueous electrochemical energy storage devices have attracted significant attention owing to their high safety, low cost and environmental friendliness. However, their applications have been limited by a narrow potential window (∼1.23 V), beyond which the hydrogen and oxygen evolution reactions occur. Here we report the formation of layered Mn5O8 pseudocapacitor electrode material with a well-ordered hydroxylated interphase. A symmetric full cell using such electrodes demonstrates a stable potential window of 3.0 V in an aqueous electrolyte, as well as high energy and power performance, nearly 100% coulombic efficiency and 85% energy efficiency after 25,000 charge-discharge cycles. The interplay between hydroxylated interphase on the surface and the unique bivalence structure of Mn5O8 suppresses the gas evolution reactions, offers a two-electron charge transfer via Mn2+/Mn4+ redox couple, and provides facile pathway for Na-ion transport via intra-/inter-layer defects of Mn5O8.