RbFTFSI {[Rubidium (Fluorosulfonyl)(trifluoromethanesulfonyl)imide,], >99.9%} Powder as Electrolyte Additive for Lithium-Ion Battery, 10-50 g/bottle, CLIBEARbFTFSI

RbFTFSI (Rubidium (fluorosulfonyl)(trifluoromethanesulfonyl)imide, RbN(SO2F)(SO2CF3)) is an asymmetric alkali-metal imide salt studied as a high-performance functional electrolyte additive for lithium-metal, lithium-sulfur, and next-generation rechargeable battery systems. It features an asymmetric hybrid anion (FTFSI-) that combines the rapid, inorganic-forming reactive fluorosulfonyl group (-SO2F) of FSI- with the thermally stable, flexible trifluoromethanesulfonyl group (-SO2CF3) of TFSI-.

Self-Healing Electrostatic Shield (SHES): Like other heavy alkali cations (Cs+, Rb+), Rb+ operates through an electrostatic shielding mechanism on lithium-metal anodes: The reduction potential of Rb+ (~ -2.93 V vs. SHE) is slightly less negative than that of Li+ (~ -3.04 V). At high local current densities (e.g., emerging dendrite tips), accumulated Rb+ ions create a localized positive electric field without being reduced into metallic rubidium. This electrostatically repels incoming Li+ ions to adjacent flat areas, forcing smooth, planar lithium deposition.

The asymmetric FTFSI- anion addresses the key limitations of both pure FSI- and TFSI- anions: (1) Inorganic-Rich SEI (LiF/Li2S): The weaker S–F bond on the fluorosulfonyl arm decomposes rapidly under reductive potentials at the anode, yielding a dense inner Solid Electrolyte Interphase (SEI) rich in lithium fluoride (LiF) and lithium sulfide (Li2S). This layer provides high mechanical modulus and fast Li+ interfacial diffusion. (2) Suppressed Aluminum Corrosion: Pure FSI- can severely corrode the aluminum current collector at potentials above 3.8 V vs. Li/Li+. The presence of the fluorinated -CF3 tail in FTFSI- stabilizes the cathode surface and forms a protective passivating film on aluminum, enabling higher voltage operation. (3) Thermal & Hydrolytic Stability: The asymmetric structure increases thermal decomposition resistance relative to pure FSI- while lowering electrolyte viscosity compared to pure TFSI-.

Part Number	CLIBEARbFTFSI (C-LIB-EA-RbFTFSI)
Chemical Formula	RbCF4NO4S2
Appearance	White Powder
Purity	>99.9% (Battery Grade)
Molecular Weight	331.75 g/mol
Package Size	10 g, 25 g, and 50 g/bottle

Notes: Please store the RbFTFSI powder in the glovebox due to its sensitivity to humidity and oxygen 

References: 

1. T. J. Leckie, et al. Secondary alkali-metal salts in supporting electrolytes for lithium polysulfide flow batteries, EES Batteries, 2026, DOI: 10.1039/d6eb00050a.
   
2. K. Rajsundar, et al., Rational engineering of electrolytes for lithium–sulfur batteries, Chemical Communications, 2025, 61, 12618–12642