New manganese oxi-iodides were prepared by redox reaction of sodium permanganate with lithium iodide in aqueous medium at room temperature. The effects of Li/Mn ratio, carbon incorporation at the synthesis stage and grinding were systematically studied. Structural characterization showed that these materials are nanocrystalline. Best electrochemical results were obtained either on samples with carbon mixed after synthesized, submitted to extensive grinding before electrode fabrication, or on samples for which carbon black was incorporated directly in the aqueous reaction medium at the synthesis stage. Typical capacities in the potential window 1.8–3.8V are160 and 130mAhg−1 at the 40th and 100th cycle, respectively.