Bismuth-antimony alloy nanoparticles encapsulated in 3D carbon framework: Synergistic effect for enhancing interfacial potassium storage

•Homogeneous BiSb nanoconfined in three-dimensional carbon framework were synthesized.•The BiSb alloy can enhance the interfacial K-storage compared with the single metal.•The 3D carbon architecture consolidates the structural integrity of the electrode. Bismuth-antimony (BiSb) alloy combines the low volume expansion of Bi with the high theoretical capacity of Sb and very suitable for application for energy storage. However, the low reversible capacity and poor conductivity of BiSb are still a challenge for promoting their potassium (K) storage properties. Herein, the homogeneous BiSb nanoconfined in three-dimensional (3D) carbon framework were synthesized by NaCl-template assisted method. In the as-constructed architecture, the nano-sized BiSb alloy particles not only shorten the electronic transport route, but also offer adequate K-storage active sites by virtue of the interface between binary alloy and graphene-like coating layers, which were theoretically validated by the density functional theory simulations. Furthermore, the carbon structure can effectively alleviate the internal stress of BiSb during the charging and discharging processes due to the robust integrated structure, i.e. graphene-like layer coated BiSb that embedded into 3D carbon architecture. As a result, the composite electrode exhibits a stable cycling of 303.5 mA h g−1 after 1000 cycles at 500 mA g−1, and a high-rate performance of 246.8 mA h g−1 at 2 A g−1. This work indicates that the enhancement of interfacial K-storage through biphasic synergistic effect will serve as a reference for the development of other energy storage materials.