Li Yuanqin, Wang Kang, Chen Jiawei, Zhang Wenguang, Luo Xuehuan, Hu Zhangmin, Zhang Qiankui, Xing Lidan, Li Weishan
School of Chemistry, South China Normal University, Guangzhou 510006, China.
National and Local Joint Engineering Research Center of MPTES in High Energy and Safety LIBs, Engineering Research Center of MTEES (Ministry of Education), and Key Laboratory of ETESPG (GHEI), South China Normal University, Guangzhou 510006, China.
ACS Appl Mater Interfaces. 2020 Jun 24;12(25):28169-28178. doi: 10.1021/acsami.0c05479. Epub 2020 Jun 9.
High-voltage cathodes provide a promising solution to the energy density limitation of currently commercialized lithium-ion batteries, but they are unstable in electrolytes during the charge/discharge process. To address this issue, we propose a novel electrolyte additive, pentafluorophenyltriethoxysilane (TPS), which is rich in elemental F and contains elemental Si. The effectiveness of TPS has been demonstrated by cycling a representative high-voltage cathode, LiNiMnO (LNMO), in 1.0 M LiPF-diethyl carbonate/ethylene carbonate/ethyl methyl carbonate (2/3/5 in weight). LNMO presents an increased capacity retention from 28 to 85% after 400 cycles at 1 C by applying 1 wt % TPS. Further electrochemical measurements combined with spectroscopic characterization and theoretical calculations indicate that TPS can not only construct a robust protective cathode electrolyte interphase via its oxidation during initial lithium desertion but also scavenge the detrimental hydrogen fluoride (HF) present in the electrolyte via its strong combination with the species HF, F, and H, highly stabilizing LNMO during the charge/discharge process. These features of TPS provide a new solution to the obstacle in the practical application of high-voltage cathodes not limited to LNMO.
高压阴极有望解决当前商业化锂离子电池能量密度受限的问题，但在充放电过程中它们在电解质中不稳定。为解决这一问题，我们提出了一种新型电解质添加剂，五氟苯基三乙氧基硅烷（TPS），它富含元素F且含有元素Si。通过在1.0 M LiPF-碳酸二乙酯/碳酸亚乙酯/碳酸甲乙酯（重量比为2/3/5）中对代表性高压阴极LiNiMnO（LNMO）进行循环，证明了TPS的有效性。通过添加1 wt%的TPS，LNMO在1 C下400次循环后容量保持率从28%提高到了85%。进一步的电化学测量结合光谱表征和理论计算表明，TPS不仅可以在初始锂脱溶过程中通过其氧化构建坚固的阴极电解质界面保护膜，还可以通过与HF、F和H等物质的强结合清除电解质中有害的氟化氢（HF），在充放电过程中高度稳定LNMO。TPS的这些特性为高压阴极实际应用中的障碍提供了一种新的解决方案，且不仅限于LNMO。
