Assembly of flower-like VS2/N-doped porous carbon with expanded (001) plane on rGO for superior Na-ion and K-ion storage
Junwei Sun, Gang Lian, Laiying Jing, Di Wu, Deliang Cui, Qilong Wang, Haohai Yu, Huaijin Zhang, Ching‐Ping Wong
Abstract
VS 2 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 VS 2 generally determines high ion diffusion barrier and large volume variation, resulting in unsatisfactory electrochemical performance of SIBs and PIBs. In this work, flower-like VS 2 /N-doped carbon (VS 2 /N-C) with expanded (001) plane is grown on reduced graphene oxide (rGO) via a solvothermal and subsequently carbonization strategy. In the VS 2 /N-C@rGO nanohybrids, the ultrathin VS 2 “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 VS 2 /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).