A Novel Ternary Pseudocapacitive Electrode with Synergistic Contributions

Abstract Ternary electrodes represent an exciting strategy to substantially enhance the performance of supercapacitors beyond what binary electrodes offer. However, the interplays among ternary constituents and their possible synergies remain poorly understood. This study investigates a ternary electrode design, wherein ferric oxyhydroxide (FeOOH) and magnesium dioxide (MnO₂) are co‐deposited onto carbon nanotube (CNT) mats. The results reveal that the ternary electrode demonstrates a 33.3% reduction in internal resistance and a 59% increase in areal capacitance compared to its binary MnO₂/CNT counterpart. Furthermore, the ternary electrode achieves a 25% increase in capacitance compared to the combined capacitances of separate MnO₂/CNT and FeOOH/CNT electrodes. These findings demonstrate that combining FeOOH and MnO₂ can synergistically enhance electrical conductivity and pseudocapacitance beyond their binary counterparts. This design yields a surface capacitance exceeding 3500 mF cm⁻² at an active material loading up to 15 mg cm⁻². By pairing with a binary FeOOH/CNT electrode, the resulting asymmetric supercapacitor exhibits an operational voltage window to 1.6 V. To demonstrate the potential of the new design, ternary electrodes are integrated into wearable and structural supercapacitors. The new synergistic ternary electrode approach provides a promising avenue for enhancing energy storage capacitance and expanding the scope of energy storage structure applications.