Metal–organic cage as fluorescent probe for LiPF6 in lithium batteries

• Published in: Green energy & environment Vol. 9; no. 10; pp. 1592 - 1600
• Main Authors: Li, Xi, Xu, Dehua, Wang, Aoxuan, Peng, Chengxin, Liu, Xingjiang, Luo, Jiayan
• Format: Journal Article
• Language: English
• Published: Henan Elsevier B.V 01.10.2024; KeAi Publishing Communications Ltd; KeAi Communications Co., Ltd
• Subjects: Acids; Adsorption; Cages; Chemical bonds; Density functional theory; Electrolytes; Emission spectra; Emissions; Excitation spectra; Fluorescent indicators; Fourier transforms; Host-guest complex; Humidity; Hydrogen bond; Hydrogen bonding; Hydrogen bonds; Lithium; Lithium batteries; Magnetic resonance spectroscopy; Metal-organic cage; Microscopy; Moisture detection; Moisture resistance; NMR; NMR spectroscopy; Nuclear magnetic resonance; Photobleaching; Scientific imaging; Selective fluorescence probe; Solvents; Supramolecular compounds; VOCs; Volatile organic compounds; Selective fluorescence probe; Metal-organic cage; Host-guest complex; Moisture detection; Hydrogen bond
• ISSN: 2468-0257; 2096-2797; 2468-0257
• DOI: 10.1016/j.gee.2023.06.001

Lithium hexafluorophosphate (LiPF6), the most commonly used lithium battery electrolyte salt, is vulnerable to heat and humidity. Quantitative and qualitative determination the variation of LiPF6 have always relied on advanced equipment. Herein, we develop a fast, convenient, high-selective fluorescence detection method based on metal–organic cages (MOC), whose emission is enhanced by nearly 20 times in the presence of LiPF6 with good stability and photobleaching resistance. The fluorescent probe can also detect moisture in battery electrolyte. We propose and verify that the luminescence enhancement is due to the presence of hydrogen bond-induced enhanced emission effect in cages. Fluorescent excitation-emission matrix spectra and variable-temperature nuclear magnetic resonance spectroscopy are employed to clarify the role of hydrogen bonds in guest-loaded cages. Density functional theory (DFT) calculation is applied to simulate the structure of host-guest complexes and estimate the adsorption energy involved in the system. The precisely matched lock-and-key model paves a new way for designing and fabricating novel host structures, enabling specific recognition of other target compounds. The schematic presentation of the Lock-&-Key model. [Display omitted] •MOC can serves as a highly selective turn-on type fluorescence probe for LiPF6 detection.•The fluorescent probe can also detect moisture in battery electrolyte.•The formation of intermolecular H-bonds between MOC and LiPF6 inhibited the nonradiative decay.