Study of Li1+x(Mn4/9Co1/9Ni4/9)1-xO2 Cathode Materials for Vehicle Battery Applications

Li 1+x (Mn 4/9 Co 1/9 Ni 4/9 ) 1-x O 2 with two lithium content (x = 0 and 0.05) has been synthesized using coprecipitated (Mn 4/9 Co 1/9 Ni 4/9 )(OH) 2 and their electrochemical properties have been investigated. Compared with the x = 0 material, the lithium-rich material (x = 0.05) exhibited superior electrochemical properties. When cycled between 2.5 and 4.4 V, the Li/Li 1.05 (Mn 4/9 Co 1/9 Ni 4/9 ) 0.95 O 2 cells showed high first-cycle coulombic efficiency (93%), reversible discharge capacity of 187 mAh/g at C/12 with 99% capacity retention after 40 cycles, and excellent rate performance (86% of C/12 rate at 5 C discharge current). The Li 1.05 (Mn 4/9 Co 1/9 Ni 4/9 ) 0.95 O 2 electrode also showed a full-cell pulse power characteristics (5 C discharge pulse) comparable to Li 1.05 (Mn 1/3 Co 1/3 Ni 1/3 ) 0.95 O 2 electrode and better thermal stability at charged state (4.4 V) than charged LiNi 0.8 Co 0.15 Al 0.05 O 2 (4.2 V). Using a battery design and cost model developed in-house, calculations found battery packs with Li 1.05 (Mn 4/9 Co 1/9 Ni 4/9 ) 0.95 O 2 as the positive electrode to be of lower cost and higher energy density than those with LiNi 0.8 Co 0.15 Al 0.05 O 2 and Li 1.05 (Mn 1/3 Co 1/3 Ni 1/3 ) 0.95 O 2 electrodes. The experimental and modeling results obtained in this work suggest Li 1.05 (Mn 4/9 Co 1/9 Ni 4/9 ) 0.95 O 2 to be a promising cathode material for vehicle battery applications.