Reversible Na Plating/Stripping with High Areal Capacity Using an Electroconductive Liquid Electrolyte System

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Anode-free sodium-metal batteries (AFSMBS) offer high energy density and safety but suffer from poor cycling stability due to unstable solid electrolyte interphase (SEI) formation and dead sodium.
• Challenges include dendrite growth and electrolyte decomposition during sodium plating and stripping, especially at high areal capacities.

Purpose of the Study:

• To develop an electroconductive electrolyte system to improve the cycling stability and Coulombic efficiency of anode-free sodium-metal batteries.
• To investigate the mechanisms of electron transfer and dead sodium utilization in the proposed electrolyte system.

Main Methods:

• Proposed an electroconductive electrolyte system combining a liquid electrolyte with electron-accepting properties and a NASICON solid electrolyte with low electronic conductivity.
• Demonstrated the system's functionality in a seawater battery (SWB) with an infinite sodium source.

Main Results:

• Achieved high Coulombic efficiency (≥99.9%) for over 60 cycles at a high areal capacity (∼24 mAh/cm²) in anode-free SWB cells.
• The electroconductive liquid electrolyte suppressed irreversible electron transfer and electrolyte decomposition, while also enabling the reutilization of dead sodium.

Conclusions:

• The proposed electroconductive electrolyte system significantly enhances the reversibility of sodium plating and stripping in anode-free systems.
• This strategy offers a promising pathway for developing stable and high-performance sodium-metal batteries, particularly in conjunction with solid electrolytes.