Aerosol‐Assisted Chemical Vapor Deposition of Mixed Phase Tin Phosphide Thin Films and Their Anode Performance for Sodium‐Ion Batteries

SnP/Sn and SnP/Sn ₄ P ₃ thin films were synthesized via aerosol‐assisted chemical vapor deposition on titanium foils. N‐phenyl phosphine carboxamide was used for the first time in chemical vapor deposition as an air‐stable phosphorus precursor, together with tin(IV) acetate in methanol or chloroform, respectively. The resulting films served as free‐standing electrodes in sodium half cells, eliminating the need for binders and conductive additives. Both types of films exhibited good electrochemical performance, delivering discharge capacities exceeding 500 mA h g ⁻¹ after 100 cycles at 200 mA g ⁻¹ . Ex situ diffraction and X‐ray absorption spectroscopy revealed reversible and irreversible changes in SnP/Sn during cycling. The SnP phase becomes amorphous after the first reduction and remains largely amorphous in subsequent cycles, but X‐ray absorption spectroscopy provides evidence for (amorphous) SnP reformation during oxidation. The results provide direct structural evidence for a conversion–alloying mechanism and highlight the structural stability of amorphous Sn–P networks during repeated sodiation/desodiation.