Exploring the activating voltages on the electrochemical performances of Li1.17Ni0.139Co0.139Mn0.552O2 cathode materials

Abstract

Lithium and manganese-rich oxide (LMR) is regarded as one of the next generation of the high energy density cathode materials. However, the activating voltages have a great impact on the electrochemical performances. Herein, we explore the effects of the activating voltages on the electrochemical performances of Li1.17Ni0.139Co0.139Mn0.552O2 cathode materials. The activating voltages can mainly affect the capacity release, rather than the cycling characteristics. The comparison study reveals that the layered structure can transform into spinel and/or nickel enriched structure due to the cation migration and the hardly-being reduced transition metals, especially for the Ni4+ during activation. Meanwhile, the surface side-reactions would also deteriorate the lithium kinetic characteristics, but the formed by-products coated on the cathode surface can resist the further attack from electrolyte, which favors to the following cycles. The Li1.17Ni0.139Co0.139Mn0.552O2 cathode materials activated to 4.6 V with 25 mA·g−1 can deliver capacities of 262.0 and 209.2 mAh·g−1 over 2.0–4.8/4.4 V at 1C (250 mA·g−1) and the highest energy densities. The appropriate activating voltages play critical roles in the optimization of the structure of LMR cathode materials and improving the electrochemical performances.