Molecular cluster ion material, polyoxomolybdate (NH4)(6)[NiMo9O32] (ANM), was utilized as a new cathode material of lithium battery. Discharge capacity and cycle performance of ANM largely depend on the particle size and type of conductive additive. Nanosize ANM particles (similar to 100 nm) can be easily prepared by a simple re crystallization method. Ketjen black (KB) conductive additive shows much more effectiveness than acetylene black (AB) conductive additive in improving discharge capacity and cycle performance of nanosize particles. Nanosize particles hand-ground with KB show high initial discharge capacity of 490 mAh g(-1) and capacity retention of 87.6% after 50 cycles at the current density of 17 mA g(-1). ANM in situ re-crystallized in the micropores or mesopores of KB (nanocomposite ANM/KB) shows improved discharge capacity at the high current densities but poor cycle stability at the low current densities, compared to nanosize particles hand-ground with KB. Ex situ XRD measurement reveals that the crystal structure of ANM becomes amorphous in the first discharge process and shows irreversibility in the following charge process. This result indicates that the insertion-extraction of lithium ion in the cathode is independent from the crystal structure. (C) 2015 Elsevier B.V. All rights reserved.