Diffraction analysis of the lithium battery cathode material Li1.2Mn0.4Ni0.3Co0.1O2

In common with many functional materials, the composition of lithium battery cathode materials has become increasingly complex. Li{sub 1.2}Mn{sub 0.4}Ni{sub 0.3}Co{sub 0.1}O{sub 2} is a highly promising cathode material, that can have up to four cations sharing a single site. Determining the occupancies of each individual element requires more information than even a joint X-ray/neutron refinement can provide. For this material additional datasets were taken to exploit changes in elemental contrast that can be induced using resonant diffraction. Together with the actual ratios of Mn:Ni:Co determined using wavelength dispersive XRF, constraints were constructed to allow the transition metals to float across the different cation sites whilst the lithium content could be freely refined. The added complications of a C2/m monoclinic structure and anisotropic broadening made for a very complex refinement. The least squares matrices were examined in order to maintain reasonable ESDs for the variables of interest.