Li_4/3Ni_1/3Mo_1/3O₂– LiNi_1/2Mn_1/2O₂Binary System as High Capacity Positive Electrode Materials for Rechargeable Lithium Batteries

Abstract

A binary system of x Li4/3Ni1/3Mo1/3O2 – (1–x) LiNi1/2Mn1/2O2 is studied as high-capacity positive electrode materials for rechargeable lithium batteries. Structural and electrochemical properties of oxides with different compositions in this binary system are examined. Mo ordering is retained for 1 ≤ x ≤ 1/3 with a monoclinic symmetry and disappears for x ≤ 1/6 with a rhombohedral symmetry. Compared with Li4/3Ni1/3Mo1/3O2, partial substitution of Mn for Mo lead to the improvement of reversible capacity and reduction of polarization. For Li6/5Ni2/5Mn1/5Mo1/5O2 (x = 1/3) and Li9/8Ni7/16Mn5/16Mo1/8O2 (x = 1/6), high reversible capacities of around 200 mAh g−1 are obtained. Improved cycling performance is achieved through the optimization of voltage ranges. Further structural characterization by ex–situ XRD reveals that the improved reversibility for the Mn-substituted samples mainly results from the suppression of Mo migration during cycling, probably associated with partial oxygen loss.