Anderson type polyoxomolybdate as cathode material of lithium battery and its reaction mechanism

• Anderson type polyoxomolybdate Na3[AlMo6O24H6] (NAM) show high discharge capacity.
• 91.2% of initial discharge capacity for NAM was retained after 50 cycles.
• The molecular cluster ion is stable, in spite of rapid amorphization of crystal.

Anderson type polyoxomolybdate, Na3[AlMo6O24H6] (NAM), was studied as the cathode material of lithium battery. Discharge capacity and cycle performance of NAM cathode largely depended on the mixing method of active material with conductive additive and the type of conductive additive. NAM ball-milled with ketjen black (KB) showed very high initial discharge capacity of 437 mAh g−1 and the most stable cycle performance with high capacity retention of 91.2% after 50 cycles. The results of ex situ XRD showed that the crystal structure changes of NAM was irreversible during the first discharge–charge process and changed to amorphous state completely after 5 cycles. Ex situ Raman spectra showed the structure of molecular cluster ion [AlMo6O24H6]3− is stable during the discharge process. These data have demonstrated that the high discharge capacity and stable cycle performance of NAM originate in the improvement of the electric conductivity and the stable molecular cluster ion [AlMo6O24H6]3− that is independent from the recoverability of its crystal structure.