Cathode Dependence of Liquid-Alloy Na-K Anodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Alkali metal anodes offer high energy density but face challenges with dendrite formation.
• Current sodium-sulfur (Na-S) battery technology requires high operating temperatures (>300 °C).
• Developing room-temperature, dendrite-free alkali metal anodes is crucial for next-generation batteries.

Purpose of the Study:

• To investigate the feasibility of using a low-cost liquid sodium-potassium (Na-K) alloy as a dendrite-free anode at room temperature.
• To determine the electrochemical behavior of the Na-K alloy anode in relation to different cathode host preferences.
• To explore the potential of the Na-K alloy as a dual-purpose anode for both sodium and potassium rechargeable batteries.

Main Methods:

• Electrochemical plating and stripping experiments were conducted using a liquid Na-K alloy at room temperature (25 °C).
• The composition range for the liquid Na-K alloy (9.2 to 58.2 wt% sodium) was identified.
• Cathode host materials with selective ion affinity (Na+ vs. K+) were employed to probe anode behavior.

Main Results:

• The liquid Na-K alloy can be plated and stripped dendrite-free within its liquid range at room temperature.
• The alloy exhibits dual-anode behavior: it functions as a sodium anode when the cathode selectively accepts Na+ ions.
• It acts as a potassium anode when the cathode preferentially accepts K+ ions over Na+ ions.

Conclusions:

• The liquid Na-K alloy demonstrates adaptable anode performance, acting as either a sodium or potassium anode based on cathode selection.
• This unique characteristic enables the development of dendrite-free sodium-metal batteries and potassium-metal batteries using a single, low-cost liquid alloy anode.
• The findings pave the way for advanced, safer, and more efficient alkali metal battery technologies operating at ambient temperatures.