Zn-doped Cr₂O₃ oxides boosted the electrochemical performance of aqueous hybrid supercapacitor

Aqueous hybrid supercapacitors (AHSCs) have emerged as a promising choice for advanced energy storage systems in the next generations. It is primarily due to their exceptional characteristics, such as superior power density, non-flammability, and environmental compatibility. However, compared to non-aqueous supercapacitors, the small working potential windows and less cycle stability are their key challenges to solve. A facile method was used to synthesize Zn-doped Cr₂O₃ supported on carbon cloth (CC) as a binder-free electrode for AHSCs and denoted as ZnCr₂O₄@CC. According to the experimental findings, the ZnCr₂O₄@CC material possesses a rapid charge transfer. As a result, the ZnCr₂O₄@CC electrode showed a remarkable charge storage performance with dominant charge storage by capacitive type (68.4 % at 10 mVs⁻¹). Further, the ZnCr₂O₄@CC electrode exhibits a maximum capacitance of 374 Fg⁻¹ at 1 Ag⁻¹ and outperforms its counterparts (194 Fg⁻¹ for Cr₂O₃ and 60.78 Fg⁻¹ for ZnO). After 10,000 cycles, the ZnCr₂O₄@CC electrode still shows 98.1 % of its initial capacitance, demonstrating its potential for practical applications. The AHSC device also constructed using ZnCr₂O₄@CC as a cathode and activated carbon (AC) as an anode with 1 M KOH as an electrolyte (ZnCr₂O₄@CC//AC-AHSC). The AHSC device exhibits an excellent capacitance retention of 96.43 % after 10,000 cycles. Further, the AHSC shows a superb energy density of 26.2 Whkg⁻¹ at a power density of 800.6 Wk⁻1 g. The current work describes a new strategy for the production of next-generation aqueous hybrid supercapacitors with exceptional electrochemical performance.