A novel carbon-free 3D porous honeycomb-like MoS2/ReS2 heterostructure with S vacancies as anodes for sodium-ion batteries

Molybdenum disulfide (MoS₂) is regarded as a promising anode for sodium-ion batteries with high theoretical capacity and unique lamellar structure. However, its practical application is hindered by inferior cycling stability and rate capability, primarily caused by low electrical conductivity and slow charge transfer resulting from polaron-induced effects. While carbon-based composites are commonly used to enhance conductivity, they often suffer from limited capacity contribution, low tap density, and insufficient interfacial stability. Herein, we designed a novel carbon-free three-dimensional (3D) porous honeycomb-like MoS₂/ReS₂ heterostructure with S vacancies (MoS₂/ReS₂-S), fabricated through a facile NaCl template strategy. The unique 3D porous honeycomb-like nanostructure mitigates volumetric change during cycling and enhances the accessibility of active sites. The built-in electric field at the MoS₂/ReS₂ heterojunction reduces the ion diffusion energy barrier and accelerates sodium ion migration. Additionally, the abundant S vacancies provide more active sites and improve reaction kinetics. Systematic characterization and theoretical calculations further show that the synergistic effect of the heterogeneous structure and S vacancies can enhance the conductivity of materials and promote charge transfer. As expected, the MoS₂/ReS₂-S anode delivers a high specific capacity (760.19 mAh g⁻¹ after 200 cycles at 0.5 A g⁻¹), remarkable rate performance (428.26 mAh g⁻¹ at 10 A g⁻¹), and exceptional cycling stability (retaining 441.8 mAh g⁻¹ after 3500 cycles at 5 A g⁻¹). This carbon-free design not only addresses the limitations of traditional carbon-based anodes but also provides a new pathway for developing anode materials for sodium-ion batteries.