Rational design of ZnS/CoS heterostructures in three dimensional N-doped CNTs for superior lithium storage

Abstract

Multiphase metal sulfides have proven to show better lithium storage performance than their single phase competitors. However, rational designing of multiphase metal sulfides with rich phase boundaries and heterointerfacial structures is still a big challenge. In this work, a superior structure of nanosized ZnS/CoS heterostructure that embedding in in-situ formed three dimensional N-doped carbon nanotubes frameworks (ZnS/CoS-NCNTs) is fabricated via using a bimetallic zeolitic imidazolate framework (ZnCo-ZIF) as precursor. Due to the crystalline similarity between Zn-ZIF and Co-ZIF, Zn and Co can be uniformly distributed in the ZnCo-ZIF precusor, leading to a uniform distribution of the final nanosized ZnS/CoS heterostructures within NCNTs networks. Therefore, the aggregation of ZnS/CoS heterostructures can be effectively suppressed, resulting in a higher utilization of active materials and improved electrochemical performance. Furthermore, the interconnected NCNTs endow ZnS/CoS-NCNTs with significantly enhanced electronic/ionic conductivity and structural integrity. As a result, the ZnS/CoS-NCNTs exhibits high rate capability and excellent cycling stability, which deliveres high reversible capacities of 1007 mA h g−1 at 1.0 A g−1 after 1000 cycles and 803 mA h g−1 at 5.0 A g−1 after 2000 cycles, respectively.