Novel MOF shell-derived surface modification of Li-rich layered oxide cathode for enhanced lithium storage

Li-rich layered oxide materials have attracted increasing attention because of their high specific capacity (> 250 mAh g(-1)). However, these materials typically suffer from poor cycling stability and low rate performance. Herein, we propose a facile and novel metal-organic-framework (MOF) shell-derived surface modification strategy to construct NiCo nanodots decorated (similar to 5 nm in diameter) carbon-confined Li1.2Mn0.54Ni0.13Co0.13O2 nanoparticles (LLO@ C& NiCo). The MOF shell is firstly formed on the surface of as-prepared Li1.2Mn0.54Ni0.13Co0.13O2 nanoparticles via low-pressure vapor superassembly and then is in situ converted to the NiCo nanodots decorated carbon shell after subsequent controlled pyrolysis. The obtained LLO@C&NiCo cathode exhibits enhanced cycling and rate capability with a capacity retention of 95% after 100 cycles at 0.4 C and a high capacity of 159 mAh g(-1) at 5 C, respectively, compared with those of LLO (75% and 105 mAh g(-1)). The electrochemical impedance spectroscopy and selected area electron diffraction analyses after cycling demonstrate that the thin C&NiCo shell can endow LLO with high electronic conductivity and structural stability, indicating the undesired formation of the spinel phase initiated from the particle surface is efficiently suppressed. Therefore, this presented strategy may open a new avenue on the design of high-performance electrode materials for energy storage. (C) 2017 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.