Phase structure and electrochemical performance control of 0.5Li₂MnO₃⋅0.5LiNi_1/3Co_1/3Mn_1/3O₂ based on the concentration adjustment in a molten salt synthesis system

Abstract

The lithium-rich layered 0.5Li₂MnO₃⋅0.5LiNi_1/3Co_1/3Mn_1/3O₂ material was simply prepared by the molten-salt method. Effect of reactant concentration on phase and electrochemical performance was systemically studied by the X-ray diffraction, the galvanostatical charge/discharge and the dQ/dV profile, respectively. It can be confirmed that the obtained phase is sensitive to the reactant concentration. The spinel structure LiMn₂O₄ or Li₄Mn₅O₁₂ phase easily occurs, when reactant concentration is low during the molten salt synthesis of Lithium-rich cathode material. The 0.5Li₂MnO₃–0.5LiNi_1/3Co_1/3Mn_1/3O₂ material with partial Li₄Mn₅O₁₂ phase shows the higher specific capacity, and delivers a initial discharge capacity of 191 mAh g^− 1 under a 20 mA g^− 1 current rate, and then increases to the maximum value of 250 mAhg^− 1. The discharge plateau of 2.5 V and the redox peaks at 2.55, 4.6 V give the electrochemical evidence of the existing Li₄Mn₅O₁₂ phase, which also results in the higher specific capacity. Formation of partial Li₄Mn₅O₁₂ phase reduces the initial discharge voltage, but mitigates the decay rate of voltage at the higher discharge current rate.

Graphical Abstract