Proton insertion in spinel lithium manganates and the effect of manganese substitution

Lithium manganate spinels with the formula Li1+xMn2~xO4 undergo lithium-proton ion exchange to give a defect lambda-MnO2 phase which can act as a lithium selective sorbent. The substitution of manganese by other metals, such as Co, Cr, Ti and Ga allow the structural properties of the spinel lattice to be modifed and tailored. This work uses neutron diffraction, inelastic neutron scattering, XAFS and atomistic calculations to show that in the non-substituted spinel, inserted protons are present predominantly as hydroxyl groups directed into the vacant 8a site, with an orientation influenced by the presence of manganese vacancies. The influence of cation substitution is explained within this context.