Highly conductive cathode materials for Li-ion batteries prepared by thermal nanocrystallization of selected oxide glasses

Glassy analogs of two important cathode materials for Li-ion cells: V₂O₅ and phosphoolivine LiFePO₄ were heat-treated in order to prepare nanocrystallized materials with high electronic conductivity of up to 7 × 10⁻² S cm⁻¹ and ca 7 × 10⁻³ S cm⁻¹ at 25 °C, respectively. There is a clear correlation between the crystallization phenomena and the increase in the electrical conductivity for both groups of glasses. Electrochemical tests of heat-treated glasses of the V₂O₅–P₂O₅ system, used as cathodes in lithium cells confirm their good gravimetric capacity and reversibility. Heat-treatment of glasses of the Li₂O–FeO–V₂O₅–P₂O₅ system also leads to a high increase in the conductivity and to formation of nanocrystalline grains in the glassy matrix, evidenced by HR-TEM images. The temperature dependence of the conductivity of these materials follows the Arrhenius formula. The presented results indicate that the overall increase in conductivity in nanocrystallized materials is due to good charge transport properties of their interfacial regions.