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Open Access Publications from the University of California

Bivalence Mn 5 O 8 with hydroxylated interphase for high-voltage aqueous sodium-ion storage

  • Author(s): Shan, X
  • Charles, DS
  • Lei, Y
  • Qiao, R
  • Wang, G
  • Yang, W
  • Feygenson, M
  • Su, D
  • Teng, X
  • et al.

© The Author(s) 2016. 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 (1/41.23 V), beyond which the hydrogen and oxygen evolution reactions occur. Here we report the formation of layered Mn 5 O 8 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 Mn 5 O 8 suppresses the gas evolution reactions, offers a two-electron charge transfer via Mn 2+ /Mn 4+ redox couple, and provides facile pathway for Na-ion transport via intra-/inter-layer defects of Mn 5 O 8.

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