Solvent Chain-Length Engineering Enables All-Climate Sodium-Ion Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) face challenges in achieving high rate capability, cycling stability, high-voltage tolerance, and wide-temperature adaptability due to solvent limitations.
• Current electrolyte designs often involve trade-offs between these critical performance metrics.

Purpose of the Study:

• To develop a molecular-scale electrolyte design strategy for SIBs by engineering solvent chain length.
• To address multi-objective optimization challenges in SIB electrolytes, focusing on kinetics, thermodynamics, and interfacial stability.

Main Methods:

• Constructed a hybrid-solvent electrolyte by combining short-chain ethers, long-chain glycol ethers, 1,3-dioxolane (DOL), and fluoroethylene carbonate (FEC).
• Investigated solvent-solvent interactions to modulate Na+ solvation and ion transport.
• Utilized FEC to induce anion-rich coordination shells for enhanced interfacial stability.

Main Results:

• The hybrid electrolyte enabled Na3V2(PO4)3||Na cells to achieve 82.75 mAh g-1 at 10 C after 9500 cycles and maintain 1 C operation for 600 days.
• Demonstrated stable Na||Na symmetric cell cycling for over one year.
• Achieved stable battery operation across a wide temperature range (-40 to 60 °C) and voltage window (2.0-4.5 V).

Conclusions:

• Solvent chain-length engineering is a viable strategy for optimizing SIB electrolyte performance.
• The developed hybrid electrolyte offers a practical pathway towards all-climate SIBs with balanced multi-performance metrics.
• This approach successfully addresses kinetic, thermodynamic, and interfacial challenges in SIBs.