Electrochemical Properties of Lithium-Rich Li[sub 1+x](Mn[sub 1∕3]Ni[sub 1∕3]Co[sub 1∕3])[sub 1−x]O[sub 2] at High Potential

The electrochemical properties of lithium-rich Li 1.1 ( Mn 1 ∕ 3 Ni 1 ∕ 3 Co 1 ∕ 3 ) 0.9 O 2 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 ∕ 3 Ni 1 ∕ 3 Co 1 ∕ 3 ) 0.9 O 2 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.