Dual-Salt Low-Concentration Electrolyte for Low-Temperature Sodium Metal Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Sodium metal batteries (SMBs) offer high theoretical capacity and lower cost than lithium-ion batteries.
• Conventional electrolytes limit SMBs' ultralow temperature performance due to unstable solid electrolyte interphase (SEI) and poor ionic kinetics.
• SEI film quality is crucial for battery cycle stability.

Purpose of the Study:

• To develop a novel electrolyte for enhanced SMB performance at ultralow temperatures.
• To address challenges of unstable SEI and suboptimal ionic kinetics in cold environments.
• To improve the cycle life and operational stability of SMBs.

Main Methods:

• Formulation of a low-concentration, dual-salt carbonate electrolyte.
• Investigation of electrolyte fluidity and anion solvation structures.
• Analysis of SEI film formation and properties.
• Electrochemical testing of Na||Na symmetric and Na||Na3V2(PO4)3 full cells at -40 °C.

Main Results:

• The novel electrolyte significantly improved ionic kinetic performance and low-temperature cycle life.
• Na||Na symmetric cells demonstrated a cycling life of 900 hours.
• Na||Na3V2(PO4)3 full cells maintained 70.5 mAh g-1 over 100 cycles at -40 °C.
• The dual-salt system promoted robust inorganic SEI films.

Conclusions:

• The developed electrolyte effectively enhances the ultralow temperature performance of SMBs.
• This electrolyte design is a promising strategy for advancing cold-operable sodium metal batteries.
• The findings contribute to the development of next-generation energy storage solutions.