Fluoroethylene carbonate (FEC) enhances fast-charging performance in lithium-ion batteries through several key mechanisms:
1. SEI Formation and Li⁺ Transport
FEC promotes the creation of a LiF-rich solid electrolyte interphase (SEI) with polymeric/oligomeric species, which facilitates faster Li⁺ transfer across the SEI. This results in improved surface kinetics during lithiation.
2. Li Plating Regulation
FEC optimizes lithium plating behavior by promoting uniform Li deposition on graphite surfaces during extreme fast charging (XFC). Without FEC, Li tends to deposit locally, increasing safety risks, while FEC redirects currents toward SEI formation, reducing dendrite growth.
3. Electrode Stability
In graphite anodes, FEC improves phase transition kinetics during XFC, shifting rate-limiting steps from surface-controlled to bulk-controlled processes as lithiation progresses. For silicon-oxide (SiO) electrodes, FEC reduces mechanical fatigue during quick charging.
4. Electrolyte Compatibility
In hard carbon anodes paired with localized high-concentration electrolytes (LHCE), FEC stabilizes the SEI over long-term cycling, achieving 99.8% Li-plating reversibility over 250 cycles and enabling 6C-rate cycling in full cells.
These combined effects result in enhanced charge transfer rates, reduced polarization, and improved safety during fast charging.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-fluoroethylene-carbonate-fec-improve-fast-charging-performance/
