Structure and bonding in Li2MoO3 and Li2−xMoO3 (0 ≤ x ≤ 1.7)

Li2MoO3 prepared by hydrogen reduction of Li2MoO4 was studied by X-ray and neutron diffraction. The results imply that the previous assignment of a β-Li2SnO3 structure to this material (C2c; a = 4.97Å, b = 8.61 Å, c = 10.10 Å, β = 99.5°) is inappropriate. Li2MoO3 has a novel, disordered α-NaFeO2 structure (R3m; a = 2.884 Å, c = 14.834 Å) with the molybdenum present as Mo3O13 clusters. This structural model is consistent with the diamagnetism and low electrical conductivity of Li2MoO3 and accounts for certain features of the Li2OMoO2 phase diagram. The presence of Mo3O13 clusters in Li2MoO3 was confirmed by comparison of the HeI photoelectron spectra of Li2MoO3 and Zn2Mo3O8; the latter compound is known from single-crystal X-ray diffraction to contain Mo3O13 clusters. Oxidative extraction of up to 85% of the lithium from Li2MoO3 was achieved at ambient temperature with mild oxidizing agents and electrochemically. Crystallographic studies of Li2−xMoO3 by X-ray and neutron powder diffraction show that lithium extraction is accompanied by migration of some molybedenum ions to sites in the lattice previously occupied by lithium ions. Electrochemical delithiation of Li2MoO3 is kinetically slow and not fully reversible.