Py14FSI (1-Butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide, >99.9%) Ionic Liquid as Battery Electrolyte Solvent, 25-100 g/bottle, CBESPy14FSI

Py14FSI (1-Butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide)—often abbreviated as BMPy-FSI—is a widely researched room-temperature ionic liquid (RTIL) that combines a 5-membered pyrrolidinium ring bearing a butyl chain with the highly mobile, flexible FSI anion. By pairing the stable, reduction-resistant Py14 cation with the smaller, more conductive FSI anion, this formulation strikes a balance between electrochemical stability and ionic transport kinetics compared to its TFSI-based or ethyl-based counterparts.

The key physicochemical & electrochemical characteristics of Py14FSI are: (1) Enhanced Ionic Conductivity: Relative to larger or more viscous imide-based ionic liquids (such as Py14TFSI), the smaller ionic radius and lower charge localization of the FSI anion result in lower viscosity and higher ionic conductivity at ambient temperatures, reducing internal cell polarization. (2) Favorable Interfacial Chemistry: The FSI anion readily decomposes under cathodic polarization to construct a stable, inorganic-rich Solid Electrolyte Interphase (SEI)—notably rich in lithium fluoride (LiF)—which effectively suppresses dendrite formation on lithium or sodium metal anodes. (3) Reductive & Oxidative Stability: The aliphatic pyrrolidinium cation provides excellent resistance against reduction at negative potentials. While the FSI anion lowers the upper oxidative limit slightly compared to TFSI, Py14FSI maintains a broad electrochemical window (stable up to ~ 4.4-4.6 V vs. Li/Li+), making it compatible with many mid-voltage and high-voltage chemistries.

Part Number	CBESPy14FSI (C-BES-Py14FSI)
CAS	1057745-51-3
Chemical Formula	C9H20F2N2O4S2
Appearance	Colorless liquid
Purity	>99.9% (Battery Grade)
Molecular Weight	322.39 g/mol
Density	1.304 g/cm3
Package Size	25 g, 50 g, and 100 g/bottle

Notes: Please try to store the Py14FSI liquid in a dry place (dryroom or glovebox is preferred). 

References: 

1. E. Paillard, et al. Electrochemical and Physicochemical Properties of PY14FSI -Based Electrolytes with LiFSI, J. Electrochem. Soc., J. Electrochem. Soc., 2009, 156, A891.
2. G. A. Elia, et al. Exceptional long-life performance of lithium-ion batteries using ionic liquid-based electrolytes, Energy Environ. Sci., 2016,9, 3210-3220.