High-voltage anode-free sodium-sulfur batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Room-temperature sodium-sulfur (Na-S) batteries are sustainable alternatives to lithium-ion batteries due to abundant materials.
• Practical Na-S batteries face challenges with low discharge voltages and excessive sodium metal anode requirements.

Purpose of the Study:

• To develop a high-voltage, anode-free Na-S battery with improved energy density and practical viability.
• To explore novel cathode chemistries and electrolytes for enhanced Na-S battery performance.

Main Methods:

• A 3.6V class Na-S battery was designed using a high-valence sulfur/sulfur tetrachloride (S/SCl4) cathode.
• Sodium dicyanamide (NaDCA) enabled reversible S/SCl4 conversion and sodium plating/stripping in a chloroaluminate electrolyte.
• A bismuth-coordinated covalent organic framework (Bi-COF) catalyst was incorporated into the sulfur cathode to facilitate conversion.

Main Results:

• The anode-free Na-S battery achieved maximum energy and power densities of 1,198 Wh/kg and 23,773 W/kg, respectively.
• The Bi-COF catalyzed cathode demonstrated a discharge capacity of 1,206 mAh/g, leading to a maximum energy density of 2,021 Wh/kg.
• The battery system exhibits a low estimated cost of $5.03 per kWh and excellent scalability.

Conclusions:

• The developed anode-free Na-S battery with S/SCl4 chemistry and NaDCA electrolyte overcomes previous limitations.
• The incorporation of Bi-COF catalyst significantly enhances electrochemical performance.
• This technology shows strong potential for grid energy storage and wearable electronics due to its high performance, low cost, and scalability.