Taming Solvent-Solute Interaction Accelerates Interfacial Kinetics in Low-Temperature Lithium-Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Lithium (Li)-metal batteries offer high energy density but face significant capacity degradation at sub-zero temperatures (-30 °C).
• This performance loss is attributed to increased kinetic barriers in interfacial processes, including desolvation, ion transport, and charge transfer.

Purpose of the Study:

• To quantitatively investigate interfacial kinetics in prototypical electrolytes at low temperatures.
• To identify the rate-limiting step in interfacial processes and its impact on battery performance.
• To explore strategies for improving low-temperature Li-metal battery operation.

Main Methods:

• Utilized three-electrode electrochemical techniques to probe interfacial kinetics.
• Employed molecular dynamics simulations to understand electrolyte behavior at the molecular level.
• Tested practical Li|LiNi0.5Co0.2Mn0.3O2 cells at -40 °C.

Main Results:

• Validated interfacial desolvation as the rate-limiting step controlling cell impedance and capacity at low temperatures.
• Demonstrated that a 1,3-dioxolane-based electrolyte with controlled solvent-solute interactions facilitates rapid desolvation.
• Achieved 66% of room-temperature capacity retention and enabled a 0.3 C charging rate for Li-metal cells at -40 °C.

Conclusions:

• The desolvation barrier, governed by solvent-solute interactions, is quantitatively determined.
• Taming solvent-solute interactions using low-affinity solvents is a viable strategy for developing high-performance low-temperature batteries.
• This research provides a pathway for enhancing the practical application of Li-metal batteries in extreme cold environments.