Assembly of flower-like VS₂/N-doped porous carbon with expanded (001) plane on rGO for superior Na-ion and K-ion storage

VS₂ with natural layered structure and metallic conductivity is a prospective candidate for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). However, due to large radius of Na⁺ and K⁺, the limited interlayer spacing (0.57 nm) of VS₂ generally determines high ion diffusion barrier and large volume variation, resulting in unsatisfactory electrochemical performance of SIBs and PIBs. In this work, flower-like VS₂/N-doped carbon (VS₂/N-C) with expanded (001) plane is grown on reduced graphene oxide (rGO) via a solvothermal and subsequently carbonization strategy. In the VS₂/N-C@rGO nanohybrids, the ultrathin VS₂ “ petals” are alternately intercalated by the N-doped porous carbon monolayers to achieve an expanded interlayer spacing (1.02 nm), which can effectively reduce ions diffusion barrier, expose abundant active sites for Na⁺/K⁺ intercalation, and tolerate large volume variation. The N-C and rGO carbonous materials can significantly promote the electrical conductivity and structural stability. Benefited from the synergistic effect, the VS₂/N-C@rGO electrode exhibits large reversible capacity (Na⁺: 407 mAh·g⁻¹ at 1 A·g⁻¹; K⁺: 334 mAh·g⁻¹ at 0.2 A·g⁻¹), high rate capacity (Na⁺: 273 mAh·g⁻¹ at 8 A·g⁻¹; K⁺: 186 mAh·g⁻¹ at 5 A·g⁻¹), and remarkable cycling stability (Na⁺: 316 mAh·g⁻¹ at 2 A·g⁻¹ after 1,400 cycles; K⁺: 216 mAh·g⁻¹ at 1 A·g⁻¹ after 500 cycles).