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Understanding the stability of MnPO4†.

Authors :: Huang, Yiqing
Fang, Jin
Omenya, Fredrick
O'Shea, Martin
Chernova, Natasha A.
Zhang, Ruibo
Wang, Qi
Quackenbush, Nicholas F.
Piper, Louis F. J.
Scanlon, David O.
Whittingham, M. Stanley
Source :: Journal of Materials Chemistry A; 2014, Vol. 2 Issue 32, p12827-12834, 8p, 1 Black and White Photograph, 3 Charts, 7 Graphs
Publication Year :: 2014
Abstract: We have revealed the critical role of carbon coating in the stability and thermal behaviour of olivine MnPO<subscript>4</subscript> obtained by chemical delithiation of LiMnPO<subscript>4</subscript>. (Li)MnPO<subscript>4</subscript> samples with various particle sizes and carbon contents were studied. Carbon-free LiMnPO<subscript>4</subscript> obtained by solid state synthesis in O<subscript>2</subscript> becomes amorphous upon delithiation. Small amounts of carbon (0.3 wt%) help to stabilize the olivine structure, so that completely delithiated crystalline olivine MnPO<subscript>4</subscript> can be obtained. Larger amount of carbon (2 wt%) prevents full delithiation. Heating in air, O<subscript>2</subscript>, or N<subscript>2</subscript> results in structural disorder (<300 °C), formation of an intermediate sarcopside Mn<subscript>3</subscript>(PO<subscript>4</subscript>)<subscript>2</subscript> phase (350-450 °C), and complete decomposition to Mn<subscript>2</subscript>P<subscript>2</subscript>O<subscript>7</subscript> on extended heating at 400 °C. Carbon coating protects MnPO<subscript>4</subscript> from reacting with environmental water, which is detrimental to its structural stability. [ABSTRACT FROM AUTHOR]