Synergistic Effect of F- Doping and LiF Coating on Improving the High-Voltage Cycling Stability and Rate Capacity of LiNi0.5Co0.2Mn0.3O2 Cathode Materials for Lithium-Ion Batteries

Kai Liu, Qingqing Zhang, Sheng Dai, Wei Li, Xingjiang Liu, Fei Ding, Jinli Zhang

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Abstract

A commercial LiNi0.5Co0.2Mn0.3O2 (LNCM) cathode material is purposefully modified using a small account of LiPF6 as one precursor via a simple means at low calcination temperature in air. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy images reveal that this modification process keeps the layered bulk structure of LNCM even though the surface components have obviously been modified. Electron energy loss spectroscopy and X-ray photoelectron spectroscopy with different etching depths further prove the formation of LiF and F- doping on the LNCM surface, which simultaneously triggers partial Ni3+ reduction to Ni2+ and the metal-oxygen bond is partially replaced by a higher energy metal-fluorine bond. The modified material (LNCM-2) retains 93.7% of its initial capacity and delivers 179.4 mAh g-1 at a current density of 0.5 C after 100 stable cycles at 3.0-4.5 V. Meanwhile, LNCM-2 is able to maintain capacity retention up to 81.1% after 300 cycles at 5 C, much better than the original LNCM (35.1%) in the commercial electrolyte. Remarkably, 90% of initial capacity is retained for LNCM-2 with considerably improved Coulombic efficiency (>99.5%) at 5 C after 300 cycles within a voltage range of 3-4.5 V compared with the primary LNCM using succinonitrile-based electrolyte. Consequently, these results fully demonstrate the advantages of synergistic effect between F- doping and LiF coating.

Original languageEnglish
Pages (from-to)34153-34162
Number of pages10
JournalACS Applied Materials and Interfaces
Volume10
Issue number40
DOIs
StatePublished - Oct 10 2018

Funding

This work was financially supported by the National Natural Science Foundation of China (21476158, 21621004), Program for Chang jiang Scholars and Innovative Research Team in University (IRT_15R46). S.D. was supported by the U.S. DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. This work was financially supported by the National Natural Science Foundation of China (21476158, 21621004), Program for Chang jiang Scholars and Innovative Research Team in University (IRT-15R46). S.D. was supported by the U.S. DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

FundersFunder number
Program for Chang jiang Scholars and Innovative Research Team in University
U.S. DOE
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Division of Materials Sciences and Engineering
National Natural Science Foundation of China21621004, 21476158
Program for Changjiang Scholars and Innovative Research Team in UniversityIRT_15R46

    Keywords

    • F doping
    • LiF coating
    • cycling stability
    • lithium-ion batteries
    • rate capacity

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