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).