Synthetic Sweeteners as Novel CEI-Stabilizing Electrolyte Additives for Li-Ion Batteries

One of the key challenges in the development of next-generation lithium-ion batteries is designing cost-effective electrolyte additives that can simultaneously stabilize electrode/electrolyteinterfaces and sustain high-rate cycling. This work explores the use of food-grade synthetic sweeteners and their lithium salts-lithium acesulfame (AceLi) and lithium saccharinate (SachLi)-as functional electrolyte additives for LCO cathodes. Synthetic sweeteners are mass-produced for the food industry, which makes them inexpensive, readily available at high purity, and structurally attractive due to the presence of sulfonyl, carbonyl, and aromatic groups that can participate in interfacial reactions. LCO half-cells were cycled with carbonate-based electrolytes containing different concentrations of AceLi and SachLi, and their performance was evaluated by galvanostatic cycling at variable C-rates, long cycling under a stable C-rate, and electrochemical impedance spectroscopy (EIS). Rate capability tests show that low to moderate concentrations of AceLi and SachLi markedly improve discharge capacity retention at high C rates compared to the additive-free electrolyte, with the optimum effect observed near 0.2 wt.% additive. XPS analysis of the cathode-electrolyte interphase (CEI) confirms additive-specific decomposition products, including high-oxidation-state sulfur (e.g., ca. 170 eV S 2p peak for Li₂SO₃, ROSO₃Li, or -SO₂-), nitrogen species (-SNC-, -NCO- in N 1s), and Li₂CO₃ (C 1s), supporting the formation of a protective CEI that enhances high-rate performance.