Analysis of Thermal Aging and Structural Stability of Li[Lix(Ni0.3Co0.1Mn0.6)1-x]O2 (x=0.11) Cathode Active Material for Rechargeable Li-Ion Batteries

The high rate capability of Mn-rich Li[Li-x(Ni0.3Co0.1Mn0.6)(1-x)]O-2 (x = 0.11) cathode active materials is investigated by cycling the cell at a given rate for five cycles and keeping the cell idle under thermal control chamber for 10 h and the same process repeating up to 30 cycles. The before and after thermal aging of Mn-rich cathode materials deliver the initial discharge capacity of 153 and 157.32 mA h g(-1) up to 30 cycles and also it is maintained the average specific discharge capacity of 140 mA h g(-1) for before thermal aging and more than 90% capacity retention. After thermal aging of cathode materials have maintain the average specific discharge capacity of 155 mA h g(-1) and more than 97% capacity retentions. During charging, they are not oxidized further; Ni2+ and at least part of Co3+ ions are oxidized to higher valence states. During the discharge reactions, the small amount of Mn3+ reduced to the Mn4+ and some part of Ni3+ ions are reduced to Ni4+. Also the Co3+ ions are fully reduced to the Co4+ state, which due to thermal aging studies does not have major affects in the Mn-rich layered structure under thermal control chamber. These thermal aging analyses are essential to achieve a deeper understanding of the structural defects and safety views for Li-ion batteries to use in electric vehicle technologies. (c) 2012 The Japan Society of Applied Physics