Metal-Organic Framework Derived Ultrafine Sb@Porous Carbon Octahedron via In Situ Substitution for High-Performance...

Alloying-type anode materials are regarded as promising alternatives beyond intercalation-type carbonaceous materials for sodium storage owing to the high specific capacities. The rapid capacity decay arising from the huge volume change during Na⁺-ion insertion/extraction, however, impedes the practical application. Herein, we report an ultrafine antimony embedded in a porous carbon nanocomposite (Sb@PC) synthesized via facile in situ substitution of the Cu nanoparticles in a metal-organic framework (MOF)-derived octahedron carbon framework for sodium storage. The Sb@PC composite displays an appropriate redox potential (0.5-0.8 V vs Na/Na⁺) and excellent specific capacities of 634.6, 474.5, and 451.9 mAh g^-1 at 0.1, 0.2, and 0.5 A g^-1 after 200, 500, and 250 cycles, respectively. Such superior sodium storage performance is primarily ascribed to the MOF-derived three-dimensional porous carbon framework and ultrafine Sb nanoparticles, which not only provides a penetrating network for rapid transfer of charge carriers but also alleviates the agglomeration and volume expansion of Sb during cycling. Ex situ X-ray diffraction and in situ Raman analysis clearly reveal a five-stage reaction mechanism during sodiation and desodiation and demonstrate the excellent reversibility of Sb@PC for sodium storage. Furthermore, post-mortem analysis reveals that the robust structural integrity of Sb@PC can withstand continuous Na⁺-ion insertion/extraction. This work may provide insight into the effective design of high-capacity alloying-type anode materials for advanced secondary batteries.