The synthesis, characterization and Li-storage properties of cubic mesostructured lithium titanate spinel (Li4Ti5O12) with uniform pores of diameter <= 15 nm and sub-10 nm grains is reported. The material was prepared in powder form by sol-gel co-assembly through a soft-templating method using a poly(isobutylene)-block-poly(ethylene oxide) diblock copolymer structure-directing agent. Electron microscopy demonstrates the mesoporous nature; the BET surface area is around 100 m(2)g(-1). Rietveld analysis of XRD data and results from XPS, FTIR and Raman spectroscopy indicate a large sensitivity of the phase composition to variations in the heating rate and temperature. Mesoporous Li4Ti5O12 obtained after heating to 600 degrees C at 10 degrees C min(-1) is virtually single phase, with minor traces of Li2CO3 accumulated on the surface. Half-cells with a Li metal anode display superior cycling (5% capacity decay between the fifth and 300th cycles at C/2) and rate performance (> 100 mA hg(LTO)(-1) at 10C).