Transition metals enrichment on the surface of layered nickel-cobalt-manganese oxide cathodes leads to the structural changes, hindering the facile lithium-ion transportation at the surface of the particles. These inhomogeneous metal distributions and structural evolutions are progressively proceeded with electrochemical cycling from the surface to the bulk, which causes to severe material degradation and short cycle life. In this study, we develop the new surface structure and chemistry on the layered cathode materials to enhance the battery performances by controlling the local concentration of transition metal. Our strategy is to improve the surface instabilities by either suppressing unwanted transition metal segregation or creating an ion conductive oxide phase or both on the specific crystallographic planes for the layered host materials. This is conducted by adding electrochemically inactive transition metals together with the active metals during the synthesis because that the transition metal elements are individually and preferentially enriched to the particular facets such as (20–2), (200), and (001) of the layered bulk. As a result, the unique surface layers are spontaneously formed along the surface planes within a few nanometer. The electrochemical characteristics shows that the newly created surface phases strongly influence on the high rate performance and long cycle life.

This work is supported by the National Research Foundation of Korea (NRF-2011-C1AAA001-0030538).