Quadruple modification for constructing ultra-stable lithium-rich cathodes

Abstract

Lithium-rich layered oxides are considered as the next generation cathode materials for lithium-ion batteries due to their high capacity and operating voltage. However, O2 release, side reactions at the cathode-electrolyte interface, transition metal(TM) dissolution, and microcracking evolution severely limit the commercial application of Li-rich cathode materials. In this work, the Eu is used to modify the Li1.2Mn0.54Co0.13Ni0.13O2 for the lithium-rich cathode. The doping of Eu in the bulk phase greatly improves the redox activity of the material, and a large number of oxygen vacancies extremely alleviate the irreversible changes of lattice oxygen. The Eu2O3 modified layer at the interface and the heterogeneous structure of the rock-salt phase effectively ensure the structural integrity and stability of the CEI during long time cycling, disturbing the orientation of the non-bonded O 2p orbitals. The attenuation of specific capacity (0.04 mA h g−1/cycle) and voltage (0.31 mV/cycle) is greatly reduced by the quadruple modification of Eu. The charge compensation mechanism, phase structure transition pattern, anion behavior and CEI evolution are analyzed by a series of ex-situ methods. The simple modification method provides guidance for the overall improvement of the performance of lithium-rich cathode materials.