材料科学
X射线光电子能谱
法拉第效率
扫描电子显微镜
兴奋剂
化学工程
阴极
表面改性
透射电子显微镜
煅烧
电解质
涂层
分析化学(期刊)
电极
纳米技术
光电子学
物理化学
复合材料
有机化学
化学
工程类
催化作用
作者
Kai Li,Qingqing Zhang,Sheng Dai,Wei Li,Xingjiang Liu,Fei Ding,Jinli Zhang
标识
DOI:10.1021/acsami.8b10016
摘要
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.
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