Nanoscale TiO2 attracts a lot of research interest as a Li-ion intercalation material. By far anatase in different nanostructures including nanosheets and mesoporous particles has been the center of attention. In this work the Li-ion intercalation behavior of another less explored nanoscale TiO2 phase, brookite, is studied. In particular the study focuses on a unique mesoporous nanoplatelet structured brookite material synthesized via a novel aqueous solution process. These unique mesoporous single crystal brookite nanoplatelets (mNPl; 135m(2)g(-1) surface area with 5-10 x 20 x 50 nm dimensions and 2-8 nm pore size) provide both favorable large electrolyte/material interface and short Li-ion diffusion length, important considerations for good Li-ion intercalation performance. A study of the mechanism of lithiation using electrochemical impedance spectroscopy at different states of discharging and X-ray diffraction of the lithiated and delithiated mNPl brookite is reported along cycling data at different rates. It is shown that a solid-solution forms upon lithiation corresponding to orthorhombic Li0.5TiO2 that is isostructural with brookite. The brookite nanoplatelets were found to progressively undergo crystal structure enhancement upon cycling despite certain lattice distortion occurring during lithiation that allows them to quickly relax upon delithiation in an extremely efficient (> 99.7% coulombic efficiency) reversible manner translating to excellent Li-ion intercalation stability. (C) 2014 Elsevier Ltd. All rights reserved.