Preparation, sintering, and electrochemical properties of tin dioxide and Al-doped tin dioxides obtained from citrate precursors

The metal-citrate method is applied to the preparation of microcrystalline tin dioxide and aluminum-doped materials. The effect of the precursor compo sition, referred to as the metal/citrate ratio, and the thermal treatment a re discussed. The different compositions produce upon thermal decomposition rutile-type SnO2 solids. For Al-containing oxide materials, AI(III) ions o ccupy octahedral sites isomorphic to Sn(IV), as shown by Al-27 MAS NMR sign als at approximate to0 ppm and Sn-119 Mossbauer signals at 0 mm/s isomer sh ift and 0.53 mm/s quadrupole splitting, respectively. A large microstrain c ontent is released by successive thermal treatments at 450 degreesC. Simult aneously, extended defects, which imply deviations from an MO2 stoichiometr y, are found upon heating. These phenomena condition the ability of the oxi de products to be used as the active anode material in lithium-ion batterie s. The best electrochemical performance of lithium anode cells is achieved for 10% Al-containing ex biscitrate oxides in which approximate to 200 Ah/k g capacities are obtained after 30 cycles.