Carbon Dots-Mediated Assembly of MnO2/PANI Ternary Composites for High-Performance Asymmetric Supercapacitors

Manganese dioxide (MnO2) has attracted considerable interest owing to its low cost and high theoretical capacitance. However, its poor electrical conductivity and limited long-term cycling stability severely impede practical applications. To overcome these drawbacks, we fabricated MnO2/PANI/CDs ternary composites using cellulose-derived carbon dots (CDs) as both a microstructural regulator and a conductive promoter via a two-step CDs-assisted strategy. In the first step, CDs were employed to direct the growth of MnO2, yielding a porous microstructure. This porous architecture enhances interfacial bonding with the subsequently introduced PANI, thereby facilitating the formation of the MnO2/PANI binary composite. In the second step, supplementary CDs were further introduced onto the surface of the MnO2/PANI, affording the final ternary MnO2/PANI/CDs composite. The sp2-hybridized CDs not only establish intimate π–π interactions with PANI chains but also reinforce interfacial adhesion with both PANI and MnO2 through their oxygen-rich surface functional groups. Consequently, they serve as conductive bridges and proton donors, markedly improving the overall electrochemical performance of the composite. Systematic SEM, TEM, FT-IR, and XPS characterizations verify the successful construction of an architecture with fully integrated components. The composite delivers an optimal specific capacitance of 526.1 F g–1 and retains 77.5% of its initial capacitance after 5000 cycles. An all-solid-state asymmetric supercapacitor assembled with MnO2/PANI/CDs delivers a specific capacitance of 160.4 F g–1 and achieves an energy density of 48.4 Wh kg–1 at a power density of 750 W kg–1. This strategy highlights the significant potential of MnO2/PANI/CDs as an advanced electrode for high-performance energy storage devices.