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Revealing the role of NH4VO3 treatment on Ni-rich cathode materials with improved electrochemical performance for rechargeable lithium-ion batteries

Abstract

Although Ni-rich layered oxides are considered a candidate of next-generation cathode materials, their inherent properties such as surface lithium residues and structural destruction, cause detrimental electrochemical performance, especially at elevated temperatures. Here, a facile ball-milling method is proposed to remove the lithium residues and enhance the electrochemical performance of LiNi0.6Co0.2Mn0.2O2. After NH4VO3 treatment, a lithium ion-conductive Li3VO4 coating layer is found on the LiNi0.6Co0.2Mn0.2O2 surface under heat-treatment temperatures of 300 and 450 ºC, with a small part of vanadium ions diffusing into the surface lattice. When the temperature surpasses 600 ºC, almost all vanadium ions dope into the bulk structure. The complex relationships among post-sintering temperature, surface structure, and their impacts on electrochemical properties are discussed in detail. Electrochemical tests show that 0.5 wt% NH4VO3 treated LiNi0.6Co0.2Mn0.2O2 at 450 ºC exhibits much improved cycling stability (96.1 % cycling retention at 0.5 C after 100 cycles and 97.2 % after 50 cycles at 55 ºC), rate capability (117.0 mAh g-1 at 5 C), and storage property (4683 ppm lithium residues amount after storing in air for 7 days). Such superior performance is ascribed to the Li3VO4 coating layer that inhibits the electrolyte decomposition and helps create a stable and thinner cathode-electrolyte interface, resulting in decreased interfacial resistance. In addition, this coating layer suppresses internal micro-stress and phase transformation from layered to spinel and rock-salt structure, which increases the structural integrity of LiNi0.6Co0.2Mn0.2O2 during repeated charge-discharge cycling.

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Publication details

The article was received on 28 Feb 2018, accepted on 08 Apr 2018 and first published on 09 Apr 2018


Article type: Paper
DOI: 10.1039/C8NR01707G
Citation: Nanoscale, 2018, Accepted Manuscript
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    Revealing the role of NH4VO3 treatment on Ni-rich cathode materials with improved electrochemical performance for rechargeable lithium-ion batteries

    C. Zhang, S. Liu, J. Su, C. Chen, M. Liu, X. Chen, J. Wu, T. Huang and A. Yu, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR01707G

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