Role of Electrolyte Additives in Fast Charging Efficiency
- Formation of Stable and Ion-Conductive SEI/CEI Layers:
Additives such as fluoroethylene carbonate (FEC) and vinyl sulfonyl fluoride (VSF) promote the formation of solid electrolyte interphase (SEI) layers rich in inorganic components like LiF, which are thin, uniform, and polymeric or oligomeric in nature. These layers facilitate faster lithium-ion transfer across the SEI, leading to improved kinetics during fast charge and discharge cycles. VSF also stabilizes the cathode–electrolyte interphase (CEI), which is critical for high-voltage and high-rate charging conditions. - Reducing Cell Impedance:
Additives like LiTDI reduce cell impedance by improving electrolyte purity and stability, which enhances ionic mobility and mitigates side reactions that otherwise slow down charging and degrade battery components. This lowered impedance allows for higher current flows during rapid charging without compromising battery lifespan. - Mitigating Side Reactions and Lithium Plating:
Fast charging often leads to polarization effects that can cause lithium plating on the anode, electrolyte decomposition, and temperature rise. Electrolyte additives help suppress these detrimental side reactions by stabilizing the electrode surface chemistry and providing a more robust SEI, thereby enhancing safety and cycle life during fast charge cycles. - Supporting High-Voltage and High-Rate Operation:
Through molecular design, additives can be tailored to stabilize electrochemical interfaces under extreme conditions. The bifunctional additive VSF is an example designed to function effectively at high voltages and fast charging rates, improving cycling stability and rate capability in lithium metal batteries. - Facilitating Fast Lithium-ion Transport:
Some additives not only form protective layers but also improve the lithium ion transport pathways within the electrolyte and across the SEI, enabling rapid lithiation/delithiation processes necessary for fast charging.
Summary
Electrolyte additives improve fast charging efficiency primarily by:
- Creating robust, LiF-rich SEI and CEI layers that enable fast lithium-ion transfer.
- Decreasing cell impedance and enhancing electrolyte stability.
- Suppressing side reactions and lithium plating risks during rapid charging.
- Enabling stable operation at high voltages and high charge/discharge rates through molecular-level design.
These functions collectively contribute to higher battery performance, longer life, and safer operation under fast charging conditions.
This understanding is based on recent research findings in lithium-ion and lithium metal battery electrolytes and their additives, which are central to advancing electric vehicle battery technologies and addressing demand for rapid recharging.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-role-do-electrolyte-additives-play-in-improving-fast-charging-efficiency/
