Phase structure and electrochemical performance control of 0.5Li2MnO3⋅0.5LiNi1/3Co1/3Mn1/3O2 based on the concentration adjustment in a molten salt synthesis system

Abstract

The lithium-rich layered 0.5Li2MnO3⋅0.5LiNi1/3Co1/3Mn1/3O2 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 0.5Li2MnO3–0.5LiNi1/3Co1/3Mn1/3O2 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.