Oxygen-Doped Carbon Monolayer Intercalation and Selenization Stabilizing 1T-Rich MoS2 to Enable Fast and Durable Sodium-Ion Storage

Metallic 1T-MoS₂ is a promising anode for sodium-ion batteries (SIBs) due to its excellent conductivity, abundant active sites, and low adsorption barrier for Na⁺. Unfortunately, intrinsic metastable features and defect-caused poor structure stability pose an unparalleled challenge in cycle life. Herein, a synergetic strategy of carbon intercalation and selenization is proposed to construct stable 1T-rich MoS_2-xSe_y, which is covalently bonded to intercalated carbon monolayers via C─S/Se and C─O─Mo bonds on reduced graphene oxide (MoS_2-xSe_y/m-C@rGO). The heterostructure expands the interlayer distance for fast Na⁺ diffusion, provides confined atomic-thickness spacing stabilizing the layered structure, induces the formation of the 1T phase, and promotes charge transfer from carbon monolayers to S atoms. Selenization remediates sulfur vacancies while enabling the stabilization of the 1T phase due to induced lattice strains and electronic structure modulation. Consequently, the electrode delivers a capacity of 242.3 mAh g⁻¹ after 2500 cycles at 5 A g⁻¹, corresponding to a capacity retention of 82.6% relative to the initial capacity at 5 A g⁻¹. The full cell delivers an appealing energy output of 167.7 Wh kg⁻¹ at 183 W kg⁻¹. An atomic-level mechanism of reversible reconstruction is proposed. This work provides valuable insights toward the design of durable, high-rate electrodes in SIBs.