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Single-Phase Lithiation and Delithiation of Simferite Compounds Li(Mg,Mn,Fe)PO4

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journal contribution
posted on 11.11.2014, 00:00 authored by Fredrick Omenya, Joel K. Miller, Jin Fang, Bohua Wen, Ruibo Zhang, Qi Wang, Natasha A. Chernova, M. Stanley Whittingham
Understanding the phase transformation behavior of electrode materials for lithium ion batteries is critical in determining the electrode kinetics and battery performance. Here, we demonstrate the lithiation/delithiation mechanism and electrochemical behavior of the simferite compound, LiMg0.5Fe0.3Mn0.2PO4. In contrast to the equilibrium two-phase nature of LiFePO4, LiMg0.5Fe0.3Mn0.2PO4 undergoes a one-phase reaction mechanism as confirmed by ex situ X-ray diffraction at different states of delithiation and electrochemical measurements. The equilibrium voltage measurement by galvanostatic intermittent titration technique shows a continuous change in voltage at Mn3+/Mn2+ redox couple with addition of Mg2+ in LiMn0.4Fe0.6PO4 olivine structure. There is, however, no significant change in the Fe3+/Fe2+ redox potential.