Understanding the Highly Reversible Potassium Storage of Hollow Ternary (Bi-Sb)₂S₃@N-C Nanocube

Abstract

Metal sulfide anodes have aroused much attention in potassium ion batteries (PIBs) owing to their high theoretical capacities, but the sluggish kinetics and inferior cycling performance caused by severe volumetric change and particle pulverization greatly hinder their further development. Herein, robust hollow structure design together with phase structure engineering endow (Bi-Sb)₂S₃@N-C anode with superior (de)potassiation kinetics and excellent electrochemical performances in PIBs. Specifically, <i>in situ</i> X-ray diffraction combined with density functional theory calculations and <i>ex situ</i> X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy (TEM) analyses indicated a fresh reaction mechanism of (Bi-Sb)₂S₃ anode with a distinctive multistep (de)potassiation route along (003) plane of (Bi,Sb) alloy thanks to the Bi-Sb phase regulation in (Bi-Sb)₂S₃ anode, ensuring it with superior reaction kinetics. Moreover, <i>in situ</i> TEM characterization revealed the advantages of the hollow nanostructure with carbon shell, facilitating fast ion transport kinetics and high tolerance of volume change as well as enabling the structural integrity of electrode material during (de)potassiation. As a result, the (Bi-Sb)₂S₃ hollow nanocube with N-doped carbon shell ((Bi-Sb)₂S₃@N-C) delivers a high initial Coulombic efficiency of 66.3%, a great rate performance of 289 mAh g^-1 at 2.0 A g^-1, and an ultralong cycling life (89% retention after 220 cycles at 0.1 A g^-1 and 85% retention after 1600 cycles at 2.0 A g^-1) in PIBs. Furthermore, the full cell of (Bi-Sb)₂S₃@N-C//PTCDA affords a high reversible capacity of 281 mA h g^-1 at 1.0 A g^-1 after 300 cycles. This work combines structural design and <i>in situ</i> techniques, proving a successful nanostructure engineering strategy to rationalize alloy-type electrode materials for PIBs.