Electrochemically active MnO ₂ coated Li _1.2 Ni _0.18 Co _0.04 Mn _0.58 O ₂ cathode with highly improved initial coulombic efficiency

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 MnO ₂ coating was used to improve the coulombic efficiency of Li _1.2 Ni _0.18 Co _0.04 Mn _0.58 O ₂ . Firstly, the pristine material was synthesized via co-precipitation following by solid-state calcination. Then MnO ₂ -coated Li _1.2 Ni _0.18 Co _0.04 Mn _0.58 O ₂ 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 Li _1.2 Ni _0.18 Co _0.04 Mn _0.58 O ₂ but also the MnO ₂ 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 10 wt.%, 15 wt.% and 20 wt.% MnO ₂ coated Li _1.2 Ni _0.18 Co _0.04 Mn _0.58 O ₂ at 20 mA g ^-1 . Furthermore, the 15 wt.% MnO ₂ coated sample delivers an initial discharge capacity as high as 294.4 mAh g ^-1 .