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Dual-function ethyl 4,4,4-trifluorobutyrate additive for high-performance Ni-rich cathodes and stable graphite anodes
Journal of Power Sources ( IF 9.2 ) Pub Date : 2018-06-14 , DOI: 10.1016/j.jpowsour.2018.06.046
Koeun Kim , Yeonkyoung Kim , Sewon Park , Hyun Ji Yang , Sung Ji Park , Kyomin Shin , Jung-Je Woo , Saheum Kim , Sung You Hong , Nam-Soon Choi

An ethyl 4,4,4-trifluorobutyrate (ETFB) additive, with ester and partially fluorinated alkyl moieties, is employed to stabilize the interface structure of Ni-rich layered LiNi0.7Co0.15Mn0.15O2 (NCM) cathodes and graphite anodes. The analysis of the surface chemistry of the electrodes shows that ETFB serves as a bifunctional additive for constructing protective layers on both electrodes in a full cell. Cycling tests reveal that the addition of 1% ETFB leads to excellent capacity retention (84.8%) for the NCM/graphite full cell, which also delivers a superior discharge capacity of 167 mAh g−1 and a high Coulombic efficiency of over 99.8% after 300 cycles at 45 °C. The ETFB-derived protective layer effectively reduces intergranular cracking in secondary NCM cathode particles upon repeated charge-discharge cycling and limits the dissolution of transition metal ions from the cathode at high temperatures. In addition, after ETFB reduction, the graphite anode develops a thermally stable interface structure, which suppresses the self-discharge of graphite coupled with the NCM cathode at 60 °C.



中文翻译:

双功能4,4,4-三氟丁酸乙酯添加剂,用于高性能的富镍阴极和稳定的石墨阳极

具有酯和部分氟化烷基部分的4,4,4-三氟丁酸乙酯(ETFB)添加剂用于稳定富镍层状LiNi 0.7 Co 0.15 Mn 0.15 O 2(NCM)阴极和石墨阳极的界面结构。电极表面化学分析表明,ETFB可作为双功能添加剂,用于在整个电池中的两个电极上构建保护层。循环测试表明,添加1%ETFB可以使NCM /石墨全电池具有出色的容量保持率(84.8%),还可以提供167 mAh g -1的出色放电容量在45°C下进行300次循环后,库仑效率高达99.8%以上。衍生自ETFB的保护层在反复进行充放电循环后,可有效减少次级NCM阴极颗粒中的晶间裂纹,并在高温下限制了过渡金属离子从阴极的溶解。此外,经过ETFB还原后,石墨阳极形成了热稳定的界面结构,该结构在60°C时抑制了与NCM阴极耦合的石墨的自放电。

更新日期:2018-06-14
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