Engineering matrix distribution in selenide-based conversion electrodes for sodium-ion batteries: from heterogeneous nanoparticle dispersion to homogeneous matrix-matrix architecture

초록

Antimony selenide and tin selenide were investigated as model systems to elucidate fundamental matrix formation mechanisms in conversion-type electrodes for sodium-ion batteries. Through comprehensive mechanistic studies combining ex situ XRD, XANES, and STEM-EDS analysis, we reveal two distinct structural evolution pathways during sodiation. The tin selenide system exhibits conventional conversion architecture with discrete metallic nanoparticles heterogeneously dispersed within ionic matrix. Conversely, antimony selenide demonstrates a fundamentally different matrix-matrix interaction mechanism, where electrochemically active matrices maintain intimate contact with nanoscale domain sizes throughout the reaction process. This architectural distinction stems from inherent differences in metal ion diffusion kinetics during conversion reactions. The homogeneous matrix distribution in antimony selenide enables superior electrochemical performance with enhanced rate capability and exceptional cycling stability. These findings establish diffusion-controlled matrix evolution as a critical design principle for optimizing conversion electrode architectures in next-generation sodium-ion battery systems through strategic manipulation of metal ion mobility characteristics.

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