Expanding Interlayer Spacing of VS ₂ with TEA ⁺ Cations for Enhanced Zinc Ion Storage

Layered VS2 holds great potential as a cathode for aqueous rechargeable zinc-ion batteries (AZIBs) due to its layered structure and rich redox chemistry of vanadium. However, issues such as electrode dissolution, low specific capacity, and sluggish redox kinetics caused by narrow interlayer spacing severely restrict its applications. Herein, we expand its interlayer spacing by hydrothermal reaction of VS2 with tetraethylammonium hydroxide. The intercalation of tetraethylammonium (TEA+) cations into VS2 interlayers (VS2-TEA) enlarges its lattice spacing from 0.57 to 1.07 nm, leading to a 5-fold increase of the Zn2+ diffusion coefficient, twice enhancement in specific capacity (275 vs 138 mAh g–1 at 0.1 A g–1), and a significantly improved rate capability (74 vs 14 mAh g–1 at 3 A g–1). Moreover, the TEA+ intercalation effectively mitigates vanadium dissolution with a significantly suppressed vanadium concentration (3.4 vs 12.9 μg mL–1) even after 8 weeks of soaking in the electrolyte. This property enables the VS2-TEA cathode to retain a nearly 100% capacity at 0.5 A g–1 over 100 cycles and a 71% capacity at 3 A g–1 over 1000 cycles, outperforming the counterpart of the pristine VS2 cathode with 82% and 37% capacity retention, respectively. This work offers a facile method to expand the interlayer spacing of layered transition metal oxides or disulfides for Zn2+ storage with fast redox kinetics.