Researchers at the Wuhan University of Technology in China have developed a facile, efficient, and general method to improve the electrochemical performance of electrode materials using a facile and general carbon coating technology. Their work is reported in a paper in the ACS journal Nano Letters.
Among numerous cathode materials, Li-rich layered oxide (LLO) materials have attracted increasing attention as promising candidates because of their high specific capacity (> 250 mAh g-1) and high operating voltage (> 3.5 V vs. Li+/Li). However, undesired spinel growth in the layered host structure usually occurred from the surface during long-term cycling, leading to fast capacity fading and voltage decay.
|Schematic illustration of LLO@C&NiCo; Cycling performance and the corresponding Coulombic efficiencies tested at current densities of 0.4 C; SAED patterns of LLO and LLO@C&NiCo after 50 cycles at 0.4 C. Credit: ©Science China Press. Click to enlarge.|
The Wuhan team constructed a carbon shell decorated with unique NiCo nanodots on as-prepared Li1.2Mn0.54Ni0.13Co0.13O2 nanoparticles. The obtained LLO@C&NiCo cathode exhibited enhanced cycling and rate capability with a capacity retention of 95% after 100 cycles at 0.4 C, 90% after 300 cycles at 2 C and a high capacity of 159 mAh g-1 at 5 C, respectively.
In-situ X-ray diffraction, electrochemical impedance spectroscopy and selected area electron diffraction analyses after cycling showed that the LLO@C&NiCo as a cathode material for LIBs exhibited superior electrochemical performances due to the protective C&NiCo shell.
The shell promotes the electron conductivity (5 times), reduces the diffusion impedance, provides a robust structure for LLO which suppresses the undesired formation of the spinel phase initiated from the particle surface during cycling, and also protects the surface structure from side reactions at the electrode/electrolyte interface.
… our work represents a new synthetic strategy for developing carbon-based functional materials for energy conversion and storage devices.—Meng et al.
This research was supported by the National Key Research and Development Program of China (2016YFA0202603) and the National Basic Research Program of China (2013CB934103).
Jiashen Meng, Xiong Liu, Jiantao Li, Qi Li, Chuan Zhao, Linhan Xu, Xuanpeng Wang, Fang Liu, Wei Yang, Xiaoming Xu, Ziang Liu, Chaojiang Niu, and Liqiang Mai (2017) “General oriented synthesis of precise carbon-confined nanostructures by low-pressure vapor superassembly and controlled pyrolysis.” Nano letters doi: 10.1021/acs.nanolett.7b03982
Zhitong Xiao, Jiashen Meng, Qi Li, Xuanpeng Wang, Meng Huang, Ziang Liu, Chunhua Han, and Liqiang Mai (2017) “Novel MOF shell-derived surface modification of Li-rich layered oxide cathode for enhanced lithium storage.” Science Bulletin doi: 10.1016/j.scib.2017.12.011>