Sustainable Cu2WS4–cellulose composites for high-performance supercapacitors: synergistic effect of a metal sulfide and a biopolymer matrix

Abstract

The rising demand for sustainable and efficient energy storage technologies has spurred significant interest in high-performance supercapacitors. Among various candidates, transition metal chalcogenides (TMCs), such as Cu₂WS₄, have emerged as promising materials owing to their intrinsic layered structure, multiple redox-active sites, and high electrical conductivity. Nevertheless, their practical implementation is often hindered by issues like agglomeration and inadequate mechanical stability. Herein, we report the synthesis of a Cu₂WS₄@cellulose composite via a hydrothermal-assisted strategy, wherein cellulose functions as a flexible, porous, and hydrophilic matrix to improve structural robustness and ion diffusion pathways. A thorough electrochemical assessment in 6 M KOH electrolyte demonstrated a high specific capacitance of 537.14 F g⁻¹ at a scan rate of 10 mV s⁻¹, along with outstanding rate capability and long-term cycling durability, retaining 91.04% of its initial capacitance after 10 000 cycles. Additionally, a symmetric supercapacitor assembled from the composite achieved a maximum energy density of 58.60 Wh kg⁻¹ at a power density of 800.99 W kg⁻¹. The device was also able to power LEDs of various colours, highlighting its potential for real-world energy storage applications. The outstanding performance is ascribed to the synergistic integration of Cu₂WS₄ nanoflakes with the cellulose scaffold, which enhances electronic conductivity, prevents structural collapse, and facilitates rapid ion transport. This study underscores the promise of Cu₂WS₄@cellulose as a next-generation electrode material for environmentally sustainable and high-efficiency energy storage systems.