Two-Dimensional Titanium Disulfide Nanosheets for Enhanced Capacity of Zinc-Ion Capacitors

Abstract

Capacitors offer high power density, superior cycle stability, and fast charging, making them highly promising for energy storage. However, their energy density needs to be improved. Due to zinc’ s abundance, low cost, high capacity, and stability, aqueous zinc-ion capacitors (ZnCs) have garnered significant attention. ZnCs face challenges such as rapid capacity decrease and reduced lifespan due to strong electrostatic interactions, electrode material dissolution, and sluggish ionic diffusion. Bulk titanium disulfide (TiS₂) has been investigated as an electrode material to overcome these disadvantages, but the effects of its two-dimensional (2D) structure have yet to be discovered. With this work, bulk TiS₂ is exfoliated into semi-metallic 2D-TiS₂ nanosheets using organolithium chemistry, optimizing it as a cathode material for ZnCs to enhance energy density. The 2D-TiS₂ exhibited a specific capacitance of 214.3 F g⁻¹ at 0.1 mV s⁻¹ scan rate and a specific capacity of 116.4 mAh g⁻¹ at a current density of 0.1 A g⁻¹, while significantly outperforming bulk TiS₂. This work highlights the potential of 2D-TiS₂ to enhance the energy density of ZnCs through improved electrical conductivity and improved accessibility of ions through nanosheets, offering a new class of cathodes for enhanced energy storage.