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

CsFTFSI (Cesium (fluorosulfonyl)(trifluoromethanesulfonyl)imide, CsN(SO2F)(SO2CF3)) is an asymmetric heavy alkali-metal imide salt utilized as a high-performance functional additive in non-aqueous electrolytes for lithium-metal, lithium-sulfur, and high-voltage battery systems. It pairs the Cs+ cation—the largest stable non-radioactive alkali ion—with the asymmetric FTFSI- hybrid anion, delivering dual-action protection for high-energy-density cells.

Maximum Electrostatic Shielding (Cs+): The Cs+ cation provides an effective Self-Healing Electrostatic Shield (SHES): The standard reduction potential of Cs+ (~ -2.92 V vs. SHE) is slightly less negative than that of Li+ (~ -3.04 V). During fast charging, electric fields concentrate at microscopic peaks/dendrite tips on the lithium anode. Cs+ ions rapidly migrate to these high-field regions and accumulate without being reduced into metallic cesium. This accumulation forms a localized positive electrostatic buffer that repels incoming Li+ ions toward surrounding valleys, driving uniform, planar lithium electrodeposition across the anode surface.

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	CLIBEACsFTFSI (C-LIB-EA-CsFTFSI)
Chemical Formula	CsCF4NO4S2
Appearance	White Powder
Purity	>99.9% (Battery Grade)
Molecular Weight	363.03 g/mol
Package Size	10 g, 25 g, and 50 g/bottle

Notes: Please store the CsFTFSI 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