Electrochemically active MnO2 coated Li1.2Ni0.18Co0.04Mn0.58O2 cathode with highly improved initial coulombic efficiency

Abstract

Lithium-rich layered oxide is known to be one of the most promising positive electrode materials for lithium ion batteries due to its large capacity and high energy density. However, low initial coulombic efficiency is currently an urgent problem hindering its practical application. In this work, electrochemically active MnO2 coating was used to improve the coulombic efficiency of Li1.2Ni0.18Co0.04Mn0.58O2. Firstly, the pristine material was synthesized via co-precipitation following by solid-state calcination. Then MnO2-coated Li1.2Ni0.18Co0.04Mn0.58O2 was prepared by heat treatment of the mixture of pristine powder and manganese nitrate. During first discharging, lithium ions can intercalate into not only the delithiated Li1.2Ni0.18Co0.04Mn0.58O2 but also the MnO2 coating, thus noticeably improves the coulombic efficiency and discharge capacity. The initial efficiency is enhanced from 61.2% (pristine) to 84.4%, 88.8% and 95.4%, respectively, for 10wt.%, 15wt.% and 20wt.% MnO2 coated Li1.2Ni0.18Co0.04Mn0.58O2 at 20mAg−1. Furthermore, the 15wt.% MnO2 coated sample delivers an initial discharge capacity as high as 294.4mAhg−1.