The metal−citrate method is applied to the preparation of microcrystalline tin dioxide and aluminum-doped materials. The effect of the precursor composition, referred to as the metal/citrate ratio, and the thermal treatment are discussed. The different compositions produce upon thermal decomposition rutile-type SnO2 solids. For Al-containing oxide materials, Al(III) ions occupy octahedral sites isomorphic to Sn(IV), as shown by 27Al MAS NMR signals at ≈0 ppm and 119Sn Mossbauer signals at 0 mm/s isomer shift and 0.53 mm/s quadrupole splitting, respectively. A large microstrain content is released by successive thermal treatments at 450 °C. Simultaneously, extended defects, which imply deviations from an MO2 stoichiometry, are found upon heating. These phenomena condition the ability of the oxide products to be used as the active anode material in lithium-ion batteries. The best electrochemical performance of lithium anode cells is achieved for 10% Al-containing ex biscitrate oxides in which ≈200 Ah/kg cap...