ZnS spheres assembled from nanoparticles confined in bagasse-based carbon nanosheets for enhanced potassium storage

Abstract

Transition metal zinc sulfide (ZnS) is a promising anode material for potassium ion batteries due to its rich abundance and high capacity (conversion/alloy dual mechanism), while still suffering the drawbacks of sluggish kinetics process and structural degradation, which restrict its practical application. Herein, ZnS spheres assembled from nanoparticles embedded in carbon nanosheets (ZnS/C@C) were synthesized with alkali-activated agricultural waste bagasse as the carbon precursor. The removal of lignin and hemicellulose by pre-treatment of bagasse with alkali solutions opens ionic diffusion channels and promotes adsorption of Zn2+ by bagasse, which is crucial for the growth of ZnS in bagasse sheets and the suppression of ZnS particle size during hydrothermal processes. Benefiting from the synergistic effects between robust embedded structure, carbon conductive network and the nanoscale nature of ZnS, the ZnS/C@C exhibited enhanced performance with high capacity (374.7 mA h g−1 at 0.2 A g−1) and rate performance (195.9 mA h g−1 at 2.0 A g−1). Kinetic studies further demonstrate that ZnS/C@C electrodes possess faster K+ transport kinetics and lower interfacial impedance. This work provides a reference for the construction of robust embedded carbon composite structures based on surface control of agricultural waste.