Co-solvents play a crucial role in enhancing fast-charging efficiency in lithium-ion batteries by improving electrolyte properties that are directly tied to the charging kinetics and stability of the battery.
Key Roles of Co-Solvents in Fast Charging
- Increase Ionic Conductivity: Adding ester co-solvents or other low-viscosity co-solvents increases the ionic conductivity of the electrolyte, enabling faster ion transport during rapid charging. This helps reduce polarization effects that otherwise degrade charging performance at high rates and low temperatures.
- Adjust Solvation Structure: Co-solvents can modify the solvation environment of lithium ions, which facilitates more efficient ion migration through the electrolyte. For example, bis(2,2,2-trifluoroethyl) carbonate (BTFEC) has been shown to effectively adjust solvation structures, synergistically stabilizing the solid-electrolyte interphase (SEI) layer on the anode and promoting fast ion transfer.
- Stabilize Electrode–Electrolyte Interfaces: Co-solvents contribute to forming stable interphase layers at both the cathode and anode. This stable dual interface reduces harmful side reactions such as lithium plating and transition metal dissolution that can occur during fast charging, thereby improving cycle life and safety.
- Reduce Electrolyte Viscosity: Low-viscosity co-solvents decrease electrolyte resistance, which directly enhances the rate performance by allowing ions to move more freely and quickly during charging.
- Suppress Lithium Dendrite Growth: Certain co-solvents help in forming a robust SEI layer enriched with fluorine-containing species that inhibit irregular lithium dendrite formation, a common cause of capacity fade and safety risks in fast charging.
Summary
Co-solvents enhance fast-charging efficiency mainly by improving the electrolyte’s ionic conductivity and lowering viscosity, which promotes faster lithium-ion transport. They also synergistically help form and stabilize the protective interphase layers on electrodes, preventing common fast-charging issues like lithium plating, dendrite growth, and interfacial degradation. These combined effects improve the battery’s rate capability, cyclability, and safety during high-rate charging.
Thus, the incorporation of appropriately chosen co-solvents is a key strategy in electrolyte design tailored for fast-charging lithium-ion batteries.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-role-do-co-solvents-play-in-enhancing-fast-charging-efficiency/
