Influence of Mesoporosity\non Lithium-Ion Storage Capacity and Rate Performance of Nanostructured\nTiO₂(B)

Abstract

Here, we present the Li⁺ insertion behavior\nof mesoporous ordered TiO₂(B) nanoparticles (meso-TiO₂(B)). Using presynthesized 4 nm TiO₂(B) nanoparticles\nas building blocks and a commercially available ethylene glycol-propylene\nglycol block copolymer (P123) as a structure-directing agent, we were\nable to produce mesoporous structures of high-purity TiO₂(B) with nanocrystallinity and mesopore channels ranging from 10\nto 20 nm in diameter. We compared the Li⁺ insertion properties\nof nontemplated TiO₂(B) nanoparticles (nano-TiO₂(B)) to meso-TiO₂(B) via voltammetry and galvanostatic\ncycling and found significant increases in overall Li⁺ insertion\ncapacity 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\ncapacity especially at high charge rates. We attribute this effect\nto higher electrode/electrolyte contact area as well as the improved\nelectron and ion transport in meso-TiO₂(B). In this study,\nwe have demonstrated the influence of both nanostructuring and mesoporosity\non Li⁺ insertion behavior by rationally controlling the\noverall architecture of the TiO₂(B) materials.