Quantitative determination of Mn3+ content in LiMn1.5Ni0.5O4 spinel cathodes by magnetic measurements

The magnetic properties of cation-disordered and cation-ordered LiMn1.5Ni0.5O4 spinel samples with different morphologies synthesized by hydrothermal and co-precipitation methods have been investigated. Extrapolation of the magnetization values measured below the ferrimagnetic ordering temperature to 0 K has been employed to quantitatively determine the Mn3+ content. The Mn3+ contents calculated on the basis of collinear spin ferrimagnetism from the extrapolated magnetic moment values at 0 K agree closely with those obtained from the capacity values in the 4 V region of lithium-ion cells. This study demonstrates that the magnetic method presented here could become a valuable tool to quantitatively determine the Mn3+ content in high-voltage spinel cathodes. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4722927]