Rational Construction of Bi₂CuO₁₂Se₄ and VGCFs@Fe₂O₃ Composite Electrodes for High-Performance Semi-Solid-State...

Recently, supercapacitors (SCs) are extensively explored as effective energy storage devices. Specifically, asymmetric SCs are being developed to enhance energy density using suitable materials with favorable nanostructures. This study describes the construction of a bismuth copper selenite (BCS-200) working electrode with an ultrathin nanosheet (UTNS) architecture. This morphology is achieved using a low-cost electrodeposition (ED) method, followed by annealing. The impact of ED time on the development of morphology is studied by synthesizing comparative electrodes simultaneously. The optimized BCS-200 electrode prepared with a deposition time of 200 s shows higher specific capacity/capacitance (C_s/C_sc) values of 330.9 mAh g^-1/2206.6 F g^-1 than the other synthesized electrodes (BCS-100, BCS-150, BCS-250, and BCS-300). Besides, a vapor-grown carbon fiber (VGCF)-added Fe₂O₃ composite coated on nickel foam (NF) is developed as a negative electrode. The VGCFs@Fe₂O₃/NF electrode exhibits the (C_s/C_sc) values of 183.5 mAh g^-1/734.4 F g^-1, which is associated with ultra-high cycling stability. In addition, the fabricated BCS-200 and VGCFs@Fe₂O₃/NF electrodes are combined to construct a wearable semi-solid-state asymmetric SC (SSASC) with an energy density (E_d) of 20.5 Wh kg^-1 and a cycling stability of 91.7% over 40000 charge/discharge cycles. Furthermore, the real-time applicability of the SSASC is verified by powering it in practical applications.