Fabrication of strong internal electric field ZnS/Fe9S10 heterostructures for highly efficient sodium ion storage

The interfacial properties of electrode materials have a crucial impact on enhancing their charge transfer. However, a deep understanding of this aspect remains elusive. Herein, we provide an effective strategy to manipulate the internal electric field (E-field) of metal sulfide heterostructures to accelerate their Na-ion storage kinetics. To prove this concept, we selected ZnS and Fe9S10 with a large energy bandgap difference as model components with the aim to build a strong E-field at their hetero-interfaces, thus fabricating stable ZnS/Fe9S10 heterostructures for high-rate and high-capacity sodium ion storage. The emerging built-in E-field in the carbon-coated ZnS/Fe9S10 heterostructures can accelerate ion/electron migration rates and facilitate charge transfer behavior by the internal driving force of the E-field, guaranteeing enhanced reaction reversibility and sodium storage kinetics. These engineered heterostructures deliver a high initial coulombic efficiency of 85.3%, a high reversible capacity of 636mA h g(-1) at 500 mA g(-1) and stable cycling performance. In particular, they also exhibit superior rate capacities of 295 mA h g(-1) at 30 A g(-1) and 235 mA h g(-1) at 50 A g(-1), indicating that this battery can be fully charged within 17 s. More importantly, this design concept can be extended to construct other heterostructures, such as ZnS and Sn2S3.