Layered Li-rich oxide cathode materials (denoted as OLO), such as Li_1+xMn_1-x-y-zNi_yCo_zO₂ (x > 0), have attracted recent research interest because these OLO materials offer high capacity performance (> 250 mAh g^–1). However, it is still difficult to use these materials in commercial cathodes because their rate capability and capacity decrease with repetitive cycle life as a result of low electrical conductivity and phase transformations. Accordingly, there have been many studies focusing on structure stabilization and enhancement of their electrical conductivity, such as through substitution with Mg, Zn, Mo and Cr ions and surface coating with Al₂O₃, TiO₂ and Li₄Ti₅O₁₂. We previously reported on the stabilization of these structures and enhancing the electrochemical performance of Li-rich cathode materials via substitution and coating. There have also been recent attempts to find new approaches for surface modification such as through the use of heterostructures. S. Lee et al. reported spinel cathode material coating on layered cathode materials, which enhanced their electrochemical performance due to the spinel structure which functions as a conductive agent and prevents side reactions. J. Cho et al. also reported heterostructured cathode materials such as spinel-layered core-shell materials and Ni-rich/Li-rich core-shell materials. Y-K. Sun et al. demonstrated a concentration-gradient shell (CGS) cathode material, featuring different concentrations of transition metals (Ni, Co and Mn) at different layers in the material. While these studies showed outstanding enhancement for stabilization of structure and electrical conductivity with good electrochemical performances, they all required complex syntheses to realize their heterostructured cathode materials.

Here, we report a facile approach to realize surface modification of the OLO cathode materials with heterostructures; our approach only includes gas change for conventional synthesis without additional surface modification steps. We obtained Li_1.167Ni_0.18Mn_0.548Co_0.105O₂, layered Li-rich oxide cathode material with enhanced electrochemical performance by reductive treatment with Ar gas.