The conversion reaction process shows a higher capacity than graphite (1000 mAh g(-1) compared with 370 mAh g(-1)) but suffers from a number of problems, including low rate capability. Using mesoporous, nanoparticulate, and bulk Fe2O3, we examine the factors influencing the rate of the Fe2O3 conversion electrode, demonstrating that electron transport to and within the particles is rate limiting. A composite electrode based on Fe2O3 can store 700 mAh g(-1) at 3000 mA g(-1) (6 mAh cm(-2) at 26 mA cm(-2)). (c) 2007 The Electrochemical Society.