Influence of Mesoporosity on Lithium-Ion Storage Capacity and Rate Performance of Nanostructured TiO2(B)

Here, we present the Li+ insertion behavior of mesoporous ordered TiO2(B) nanoparticles (meso-TiO2(B)). Using presynthesized 4 nm TiO2(B) nanoparticles as building blocks and a commercially available ethylene glycolpropylene glycol block copolymer (P123) as a structure-directing agent, we were able to produce mesoporous structures of high-purity TiO2(B) with nanocrystallinity and mesopore channels ranging from 10 to 20 nm in diameter. We compared the Li+ insertion properties of nontemplated TiO2(B) nanoparticles (nano-TiO2(B)) to meso-TiO2(B) via voltammetry and galvanostatic cycling and found significant increases in overall Li+ insertion capacity for the latter. While nano-TiO2(B) and meso-TiO2(B) both show surface charging (pseudocapacitive) Li+ insertion behavior, meso-TiO2(B) exhibits a higher overall capacity especially at high charge rates. We attribute this effect to higher electrode/electrolyte contact area as well as the improved electron and ion transport in meso-TiO2(B). In this study, we have demonstrated the influence of both nanostructuring and mesoporosity on Li+ insertion behavior by rationally controlling the overall architecture of the TiO2(B) materials.