南开大学陈军团队报道了用于不易燃和长寿命锂离子电池的具有独特P-F键的单氟化磷酸盐。相关研究成果于2024年10月9日发表于国际一流学术期刊《德国应用化学》。

采用传统碳酸盐基电解质的锂离子电池（LIBs）在大规模应用中存在安全问题。磷酸盐具有高阻燃性，但由于无法形成钝化的固体电解质界面（SEI），因此与石墨阳极不相容。

该文中，研究人员报告了一种单氟共溶剂，二乙基氟磷酸盐（DEFP），其具有独特的P-F键，可以在LIBs的安全性和电化学性能之间进行权衡。DEFP中的P-F键削弱了与Li⁺离子的离子偶极相互作用，降低了去溶剂化势垒，同时降低了DEFP的最低未占分子轨道（LUMO），促进了坚固且富含无机物的SEI的形成。

此外，由于坚固的SEI和P-F键的固有阻燃性能，DEFP表现出更好的热稳定性。因此，与磷酸三乙酯基电解质和商用碳酸盐电解质相比，优化的DEFP基电解质在LiNi_0.8Co_0.1Mn_0.1O₂||石墨全电池中表现出更好的循环性能和倍率容量。即使在3.45 g Ah^-1的低E/C比下，1.16 Ah NCM811||Gr袋式电池在200次循环后也能实现94.2%的高容量保持率。

该项工作提供了一种有前景的方法来解耦磷酸盐安全性和石墨兼容性，为更安全、更高性能的锂离子电池铺平了道路。

附：英文原文

Title: Monofluorinated Phosphate with Unique P-F Bond for Nonflammable and Long-Life Lithium-Ion Batteries

Author: Yuankun Wang, Yintong Zhao, Shu Zhang, Long Shang, Youxuan Ni, Yong Lu, Yixin Li, Zhenhua Yan, Zhiwei Miao, Jun Chen

Issue&Volume: 2024-10-09

Abstract: Lithium-ion batteries (LIBs) with conventional carbonate-based electrolytes suffer from safety concerns in large-scale applications. Phosphates feature high flame retardancy but are incompatible with graphite anode due to their inability to form a passivated solid electrolyte interphase (SEI). Herein, we report a monofluorinated co-solvent, diethyl fluoridophosphate (DEFP), featuring a unique P-F bond that allows a trade-off between safety and electrochemical performance in LIBs. The P-F bond in DEFP weakens ion-dipole interactions with Li+ ions, lowering the desolvation barrier, and simultaneously reduces the lowest unoccupied molecular orbital (LUMO) of DEFP, promoting the formation of a robust and inorganic-rich SEI. Additionally, DEFP exhibits improved thermal stability due to both robust SEI and the inherent flame-retardant properties of the P-F bond. Consequently, the optimized DEFP-based electrolyte exhibits improved cyclability and rate capacity in LiNi0.8Co0.1Mn0.1O2 || graphite full cells compared with triethyl phosphate-based electrolytes and commercial carbonate electrolytes. Even at a low E/C ratio of 3.45 g Ah-1, the 1.16 Ah NCM811||Gr pouch cells achieve a high capacity retention of 94.2% after 200 cycles. This work provides a promising approach to decouple phosphate safety and graphite compatibility, paving the way for safer and high-performance lithium-ion batteries.

DOI: 10.1002/anie.202412108

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202412108