Sb4O5Cl2 embedded in carbon polyhedra for fast charge kinetics towards high-capacity Li-ion capacitors

Abstract

SbO_x with high theoretical capacity is regarded as an ideal negative electrode material for Li-ion capacitors (LICs). However, its poor conductivity and vast volume change during the lithiation/de-lithiation process limit electrochemical performance and practical application. Herein, we present an atomic-scale structural engineering strategy to confine Sb₄O₅Cl₂ nanoclusters in a zeolitic imidazolate framework (ZIF)-derived carbon polyhedron (ZCP) as a pomegranate-like polyhedron composite anode. The incorporation of Sb₄O₅Cl₂ and the carbon polyhedron regulate the Fermi level and coordination environment of Sb atoms for enhanced electronic conductivity and accelerated ion-transfer kinetics. Moreover, the obtained pomegranate-like structure can accommodate the volume expansion of Sb₄O₅Cl₂ during cycling. As a result, the Sb₄O₅Cl₂@ZCP electrode exhibits a high capacity of about 800 mA h g⁻¹ and excellent cycling stability. The LICs based on the Sb₄O₅Cl₂@ZCP anode and active carbon cathode possess a high energy density of 122 W h kg⁻¹ and a power density of 9.7 kW kg⁻¹. Simultaneously, a halogen ion substitution chemistry is also disclosed for high-performance doped SbO_x. This study provides effective guidelines for the design of large-capacity and high-rate anodes in LICs.