Degradation at the Na₃SbS₄/Anode Interface in an Operating All-Solid-State Sodium Battery

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state sodium batteries offer sustainable energy storage using earth-abundant elements.
• Solid-state electrolytes (SEs) enhance safety and energy density compared to liquid electrolytes.
• Na3SbS4 is a promising sodium-ion conductor for solid-state sodium batteries due to its high conductivity and stability in dry air.

Purpose of the Study:

• To investigate the decomposition chemistry of Na3SbS4 at the anode interface during electrochemical cycling.
• To identify the degradation products and understand the mechanisms limiting the cycle life of Na3SbS4-based sodium batteries.

Main Methods:

• In situ Raman spectroscopy combined with post-mortem characterization techniques.
• Spectroelectrochemical analysis to study the solid electrolyte/anode interface in an operating device.

Main Results:

• The SbS4(3-) counterion undergoes electrochemical reduction at potentials relevant to sodium-ion reduction.
• Multiple decomposition pathways were identified, yielding products such as SbS3(3-), Sb2S7(4-), NaSb, and Na2S.
• Decomposition was found to be irreversible, leading to product accumulation and heterogeneous degradation across the interface.

Conclusions:

• The electrochemical reduction of the SbS4(3-) anion is the primary cause of Na3SbS4 decomposition at the anode interface.
• Understanding these decomposition mechanisms is crucial for improving the long-term stability and cycle life of solid-state sodium batteries.
• Further research is needed to mitigate interfacial degradation and optimize Na3SbS4 for practical applications.