Control of TiO₂ grain size and positioning in three-dimensionally ordered macroporous TiO₂/C composite anodes for lithium ion batteries

After several high-profile incidents that raised concerns about the hazards posed by lithium ion batteries, research has accelerated in the development of safer electrodes and electrolytes. One anode material, titanium dioxide (TiO₂), offers a distinct safety advantage in comparison to commercialized graphite anodes, since TiO₂ has a higher potential for lithium intercalation. In this article, we present two routes for the facile, robust synthesis of nanostructured TiO₂/carbon composites for use as lithium ion battery anodes. These materials are made using a combination of colloidal crystal templating and surfactant templating, leading to the first report of a three-dimensionally ordered macroporous TiO₂/C composite with mesoporous walls. Control over the size and location of the TiO₂ crystallites in the composite (an often difficult task) has been achieved by changing the chelating agent in the precursor. Adjustment of the pyrolysis temperature has also allowed us to strike a balance between the size of the TiO₂ crystallites and the degree of carbonization. Using these pathways to optimize electrochemical performance, the primarily macroporous TiO₂/C composites can attain a capacity of 171 mAh/g at a rate of 1 C. Additionally, the carbon in these composites can function as a secondary template for high-surface-area, macroporous TiO₂ with disordered mesoporous voids. Combining the advantages of a nanocrystalline framework and significant open porosity, the macroporous TiO₂ delivers a stable capacity (>170 mAh/g at a rate of C/2) over 100 cycles.