Unveiling the potential of copper-doped metal oxides: A novel strategy for high-capacity hybrid supercapatteries with enhanced power, energy density, and cycling stability

Abstract

A Cu-doped ZnO/α-Fe₂O₃ composite was developed as an advanced supercapattery material, combining battery and supercapacitor characteristics. Cu doping enhanced charge transport by increasing carrier density, reducing recombination, and facilitating charge transfer, improving electrical conductivity and redox activity (Cu²⁺/Cu⁺). This study systematically investigates the role of Cu doping in ZnO and its synergistic interaction with α-Fe₂O₃ to enhance electrochemical performance. The Cu-doped ZnO/α-Fe₂O₃ (5 wt %) exhibited a high specific capacity of 689.7 C g⁻¹ at 1 A g⁻¹, with excellent rate capability and 98 % retention after 10,000 cycles. In a supercapattery device using Cu-doped ZnO/α-Fe₂O₃ (5 wt %) as the anode and activated carbon (AC) as the cathode, the system delivered 211.13 F g⁻¹ at 1 A g⁻¹, with a power density of 337.8 W kg⁻¹ and an energy density of 93.8 Wh kg⁻¹. The solid-state device retained 99 % capacity after 10,000 cycles in PVA-KOH gel electrolytes, attributed to its hierarchical structure promoting active sites and ion transport. Dunn's model confirmed a diffusion-controlled charge storage mechanism, with the capacitive contribution increasing from 35 % to 63 %, emphasizing the battery-grade performance.