Effects of Fe and Li2MnO3-like domains on structural stability in Co-free Li-rich layered oxide cathodes

Abstract

The aggregation of Li₂MnO₃-like domains in Li-rich layered oxides (LLOs) causes severe capacity/voltage fading, which seriously impedes their commercial applications. Here, we design Co-free Li-rich LiFeNiMnO system with dispersed small-sized Li₂MnO₃–like domains (D-LFNMO) and aggregated Li₂MnO₃-like domains (A-LFNMO) to investigate effects of Li₂MnO₃-like domain sizes and Fe content on structures and oxidation process using density function theory (DFT) calculations. De-lithiation structures, structural stability and oxidization mechanism of lattice oxygen ions are explored. Structural stability is finished through calculating oxygen release energies and migration energy barriers of Mn⁴⁺ ions based on a climbing image nudged elastic band (CI–NEB) method. Research shows that LLOs with dispersed small-sized Li₂MnO₃-like domains and the moderate Fe content would possess highly reversible oxygen redox and excellent structural stability and would exhibit superior cycling stability of high capacity. The findings provide new perspectives and concepts for designing high-energy Li-rich cathodes.