Electrochemical Properties of Al Doped Li(Ni1/3CO1/3Mn1/3-xAlx)O-2 Cathode Materials

Cathode materials of Al-doped Li(Ni1/3Co1/3Mn1/3-x Al-x),302 (x=0.0, 0.005, 0.01. 0.05) for lithium ion batteries were synthesized with ultra-sonic spray pyrolysis method and single step heat treatment. No secondary phases were found in all synthesized powders. The intensity ratio of I-003 to I-104, however, slightly decreased and the particle size increased with the Al contents. The cells with bare, 0.5 and 1.0 at% Al-doped powders showed the initial discharge capacities of 182, 180 and 184 mAhg(-1) in a voltage range of 3.0 similar to 4.5 V at 1C rate, and the capacity retentions of 81, 77 and 78% at the end of 30 cycles, respectively. But in the voltage range of 3.0 similar to 4.6 V, the Al-doping significantly enhanced the cycle stability. For example, the discharge capacity after 50 cycles was maintained to 70% in the 0.5 at% Al-doped sample compared to only 30% in no doped sample. The improvement of the cycle stability was thought to be due to Mn3+ ion decrease as the Al doping from the XPS analysis results.