BESA {Bis(ethylene sulfate), or BDTD, >99.5%} as Battery Electrolyte Additive, 10-50 g/bottle, CBEABESA

Bis(ethylene sulfate)—systematically named 2,2'-bi(1,3,2-dioxathiolane) 2,2,2',2'-tetraoxide (and commonly abbreviated as BES or BDTD)—is a bis-cyclic sulfate organosulfur additive used in non-aqueous electrolytes for high-voltage lithium-ion (LIBs), lithium-metal, and sodium-ion batteries. Combining two reactive 1,3,2-dioxathiolane 2,2-dioxide (ethylene sulfate) rings linked by a direct carbon-carbon bond, BES acts as a multi-functional film-former and structural cross-linker at both electrode interfaces. Its core functional roles & electrochemical advantages are shown below:

Dual Cyclic Sulfate Architecture for High Cross-Linking Density: Mono-cyclic sulfates such as ethylene sulfate (DTD) or propylene sulfate (MDTD) contain only one reactive sulfate ring per molecule. BES incorporates two distinct cyclic sulfate rings. Upon electrochemical reduction or oxidation, both rings undergo ring-opening cleavage of C–O and S–O bonds, generating a dense, 3D cross-linked interphase network. (CH2OSO2Li2).

Conductive Inorganic Sulfur-Rich SEI on Anodes: BES possesses a high reduction potential (~ 1.3–1.5 V vs. Li/Li+), reducing preferentially on graphite, silicon-carbon (Si/C), or lithium-metal anodes before baseline carbonate solvents. It decomposes into an inorganic-rich Solid Electrolyte Interphase (SEI) composed predominantly of lithium sulfate (Li2SO4), lithium sulfite (Li2SO3), and lithium alkyl disulfates. This sulfur-rich layer provides low activation energy barriers for Li+ or Na+ ion transport, significantly reducing interfacial charge-transfer resistance (Rct) and facilitating high-rate capability.

High-Voltage Cathode Interphase Passivation (CEI): On nickel-rich layered oxides (NMC811, NCMA) and high-voltage manganese cathodes (>4.4 V vs. Li/Li+), BES participates in sacrificial oxidation. The resulting Cathode Electrolyte Interphase (CEI) passivates surface catalytic sites, suppressing transition-metal leaching (Ni^{3+}/Ni^{4+}, Mn^{3+}) and preventing parasitic oxidation of bulk carbonate solvents.

Suppression of Gas Evolution & PC Exfoliation: The rapidly formed, cross-linked sulfate interphase effectively blocks solvated cation co-intercalation into graphite, allowing propylene carbonate (PC)-rich formulations to cycle without graphite exfoliation. It suppresses gas generation (CO2, CO) and cell swelling during high-temperature storage and cycling (55–60°C).

Part Number	CBEABESA (C-BEA-BESA)
CAS	1431298-10-0
Chemical Formula	C₄H₆O₈S₂
Appearance	White Powder
Purity	>99.5% (battery grade) H2O<200 ppm, HF<150 ppm
Molecular Weight	125.4 g/mol
Density	1.433 g/mL at 25 °C
Melting Point	125.4 °C (lit.)
Package Size	10 g, 20 g, and 50 g/bottle

Notes: Please store the BESA powder in the dry place (glovebox is the best)

References: 

1. S. Azam, et al. Ethylene Sulfate Derivatives as General-Purpose Electrolyte Additives for NMC Li-Ion, LFP Li-Ion and Na-Ion Cells, J. Electrochem. Soc., 2026, 173, 110518
2. H. Wan, et al. Advanced Electrolyte Systems with Sultones Additives for High-Voltage Lithium Batteries, Batteries & Supercaps, 2024, 7, e202400477.