Moisture-Driven Degradation Pathways in Prussian White Cathode Material for Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Prussian white (PW) exhibits high theoretical capacity for sodium-ion batteries.
• PW performance is limited by capacity variability and cycling stability.
• Water content significantly impacts PW performance, but moisture exposure effects are unexplored.

Purpose of the Study:

• To investigate the influence of humidity on Prussian white structure and electrochemical properties.
• To elucidate the chemical mechanisms behind moisture-induced performance degradation in PW.
• To understand the variability in reported PW performance.

Main Methods:

• Systematic study of hydrated (M-PW) and dehydrated (R-PW) Prussian white under varying humidity.
• Analysis of structural and electrochemical property changes.
• Identification of chemical pathways leading to capacity fading.

Main Results:

• Moisture exposure causes capacity fading via two distinct steps.
• Step 1: Sodium reacts with moisture forming NaOH and Fe oxidation (reversible).
• Step 2: NaOH causes PW decomposition to Na4[Fe(CN)6] and iron oxides (irreversible), forming a passivating layer.

Conclusions:

• Moisture-driven degradation mechanisms in PW are identified.
• Understanding these mechanisms is crucial for designing strategies to mitigate performance decay.
• This research clarifies performance variations in PW for improved sodium-ion battery development.