Bio-templated synthesis of hierarchical polypyrrole-coated VS4 for supercapacitors†

Abstract

Vanadium tetrasulfide (VS₄) is increasingly acknowledged as a potential electrode material for supercapacitors, attributed to its unique one-dimensional structural characteristics and elevated sulfur content. However, its intrinsic low conductivity and the tendency of vanadium to dissolve in the electrolyte have severely hindered its cycling performance, resulting in limited specific capacity under practical application conditions. The realization of advanced energy storage materials predominantly hinges on the exploitation of multiple oxidation states, the design of rational nanostructures, and the achievement of high electrical conductivity. Consequently, we report the successful construction of VS₄ and polypyrrole (PPy) cross-aligned nanostructures on the surface of bio-templated diatomite (De@VS₄@PPy) using a two-step hydrothermal and oxidative polymerization technique, which has led to remarkable electrochemical performance (specific capacitance of 243.33 F g⁻¹ at a current density of 1 A g⁻¹) and outstanding energy storage capabilities (97.7% capacitance retention after 3000 cycles). The highly conductive and cross-aligned nanostructures facilitate efficient electrolyte ion diffusion and concurrently minimize charge transfer resistance. Notably, the De@VS₄@PPy nanostructured electrode materials demonstrate significant specific capacitance, a broad potential window, and outstanding cycling stability. Furthermore, this strategy can be readily extended to practical applications, exemplified by the asymmetric supercapacitors assembled employing De@VS₄@PPy nano-electrode materials, which can achieve potential windows and maximum energy densities up to 1.8 V and 21.75 W h kg⁻¹ (at 899.94 W kg⁻¹), respectively. This work serves as a valuable reference for future studies focused on the screening and optimization of superior electrode materials.