Instability of Antimony‐Based Energy Storage Materials in Alkaline Environments

Effective energy storage is crucial for maintaining a reliable supply of renewable energy. Supercapacitors serve as buffers, storing surplus energy during low demand and releasing it during peak times. Antimony‐based materials are promising candidates for supercapacitors due to their high‐power density and long cycle life. This study demonstrates that, although antimony‐based materials have previously been investigated in alkaline electrolytes, antimony sulfide iodide (SbSI), antimony sulfide (Sb ₂ S ₃ ), and antimony oxide (Sb ₂ O ₃ ) exhibit extremely poor stability in alkaline electrolytes such as NaOH and KOH. They react with these solutions to form compounds such as potassium antimony sulfide oxide (K ₃ SbS ₃ ·(Sb ₂ O ₃ ) ₃ , PASO), which compromise supercapacitor performance. Although initially stable, PASO degrades quickly upon cycling, affecting long‐term storage applications. The study further investigates the stability of SbSI in different electrolytes through cyclic voltammetry, such as in neutral 0.5 M Li ₂ SO ₄ and acidic 0.5 M H ₂ SO ₄ electrolytes. SbSI shows improved structural stability in the acidic environment, while in the neutral electrolyte, its electrochemical response is less effective due to polarization and poor charge storage. These findings highlight the importance of electrolyte compatibility and post‐cycling characterization when evaluating antimony‐based materials for electrochemical energy storage.