Unveiling Reaction Dynamics and Degradation Pathways in Microwave-Synthesized Antimony Anodes for Na-Ion Batteries

Abstract

Microwave-assisted synthesis can be used to prepare antimony–carbon composite materials for sodium-ion battery studies. In this work, antimony nanocrystals embedded in a conductive carbon matrix are obtained via a fast microwave-assisted approach. The resulting Sb/C material shows negligible bulk oxide content, as confirmed by PXRD, HR-TEM, TOF-SIMS, and thermal analysis. Furthermore, we provide a detailed electrochemical investigation into the origin of a low-potential feature that appears around EWE (vs. Na metal) = 0.30 V during sodiation and becomes increasingly pronounced at higher rates or after extended cycling. Our results indicate that this feature arises from kinetic limitations that impede the original reaction pathway, and we propose that it is consistent with an alternative low-potential sodiation process. While this alternative process can temporarily sustain capacity, its emergence correlates with electrochemical aging and the onset of long-term capacity fading. These findings offer new insights into the intrinsic reaction and degradation pathways of Sb-based anodes in sodium-ion batteries and underline the importance of kinetic stability for long-term reversibility. The resulting PAA-based composite electrodes enable efficient utilization of the active material in sodium half-cells, with capacities even increasing with cycle number and approaching the theoretical maximum. This makes the material highly suitable for probing the electrochemical behavior governing the Na–Sb system.