Hybrid charge storage mechanism in binder-free ultrathin siloxene nanosheets-based high voltage supercapacitor

Abstract

Approaches for understanding the significance of the appropriate combination of electrode-electrolyte systems on the electrochemical behavior of electrodes and charge storage mechanism inside the supercapacitor are a prerequisite for effective and stable energy storage devices. Herein, low-cost devices were fabricated using binder-free siloxene nanosheets with aprotic and protic electrolytes to study the charge storage behavior of the supercapacitors. This study demonstrates that the novel combination of binder-free two –dimensional siloxene electrode with PVA/H₃PO₄ gel electrolyte provides a high specific capacitance of 13.15 mF/cm² with ∼98 % capacitance retention over 10,000 cycles. Additionally, it has a wide operating potential window (+4 V to –4 V), which increases the device's energy density and appeals to high-voltage applications. This improvement is attributed to the hybrid (capacitive and diffusive) charge storage mechanism which resulted from synergistic effects between the functional groups on the surface of siloxene nanosheets and H⁺ ions from protonated gel electrolytes. This work broadens the new perception toward developing cost-effective and lightweight hybrid energy storage devices using a synergistic electrode-electrolyte system for real-world applications.