Yolk–Shell Antimony/Carbon: Scalable Synthesis and Structural Stability Study in Sodium Ion Batteries

Abstract Antimony with compelling features in capacity and sodiation voltage has not been literally considered for practical applications, due to the lack of scalable fabrication methods that can make antimony stable enough in cycling and more affordable than hard carbon. Herein, the synthesis of yolk–shell antimony/carbon composites from cheap source materials is introduced, which only entails common apparatuses and is not energy intensive. The reduction of antimony trioxide coated with polypyrrole (PPy) creates hollow space and gives rise to the construction of yolk–shell structures. The material cost is evaluated to be ≈$6.6 kg –1 , which is much lower than the price of standard hard carbon. A sublimation–reduction mechanism is revealed by a heating experiment performed in using environmental transmission electron microscopy (TEM). From real‐time observation of the sodiation process, the feasibility of such structure designing is validated to counter expansion upon sodiation. The composite delivers a reversible capacity up to 612 mAh g –1 and exhibits excellent stability in deep cycling. The stability is correlated with the confinement of antimony inside the carbon shell. Through further characterization using cryogenic TEM, the generation of solid–electrolyte interphases on both the antimony and carbon is confirmed.