Hierarchical vanadium sulfide nanosheets with expanded interchain spacing for high-performance sodium-ion batteries

Abstract

Sodium-ion batteries (SIBs) have been intensively researched as potential alternative energy storage devices to lithium-ion batteries (LIBs). Nevertheless, the scarcity of suitable anode materials capable of hosting the large radius of Na⁺ has hindered the further application of SIBs. Herein, we developed a hierarchical VS₄ nanosheet with an expanded interchain spacing of 0.98 nm without additives for the first time. Additionally, we found that the porous structure in the hierarchical VS₄ nanosheet provides sufficient active sites for Na⁺ storage and alleviates the volume variation during discharge/charge cycles, as supported by finite element simulation (FES) data. More importantly, a dynamic insertion-dominated storage mechanism was revealed through synchrotron X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. Thus, the optimized anode delivered a high capacity of 441 mAh g⁻¹ at 1 A g⁻¹ after 200 cycles. This work provides critical insights into the design of SIBs by correlating storage mechanisms with electrode's structural composition.