Electrochemical Properties of Lithium-Rich Li_1+x(Mn_1/3Ni_1/3Co_1/3)_1–xO₂ at High Potential

Zonghai Chen,¹ Y.-K. Sun,² and K. Amine^1
1Chemical Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
²Department of Chemical Engineering, Center for Information and Communication Materials, Hanyang University, Seongong-gu, Seoul 133-791, Korea

The electrochemical properties of lithium-rich Li_1.1(Mn_1/3Ni_1/3Co_1/3)_0.9O₂ positive electrode material were carefully investigated to understand its performance limitations as an advanced positive electrode material for lithium-ion batteries. The experimental evidence on the initial irreversible capacity loss, the capacity retention, and the ac impedance data consistently demonstrated that Li_1.1(Mn_1/3Ni_1/3Co_1/3)_0.9O₂ had an intrinsic critical upper cutoff potential at about 4.3 V vs. Li+/Li, beyond which the electrochemical performance of the active material deteriorated significantly. This detrimental impact at high potential (>4.3 V vs. Li+/Li) was related to the oxidative reaction of the electrolyte by the highly delithiated positive electrode material.

©2006 The Electrochemical Society