Hierarchical structure of 1D spiky-like CoN-CNTs@PANI nanotubes supported on 2D Ti3C2Tx nanosheets for high-performance zinc-ion capacitors

Two-dimensional (2D) layered MXene (e.g., Ti 3 C 2 T x ) is a research focus for zinc-ion capacitors (ZICs) electrodes due to its large specific surface area and high conductivity. However, its practical use is constrained by two critical bottlenecks: low theoretical capacitance and severe interlayer stacking, which directly reduce Zn 2+ transport efficiency and electroactive site accessibility. Constructing hierarchical structures addresses this by providing efficient Zn 2+ diffusion pathways, abundant electroactive sites, and excellent structural stability. This work prepared a 1D/2D hierarchical CoN-CNTs@PANI/Ti 3 C 2 T x composite via in-situ polymerization and electrostatic self-assembly. First, 1D CoN-CNTs provide polyaniline (PANI) polymerization sites to suppress its volume expansion and to form conductive channels, while spiky PANI shells offer extra faradaic sites. Second, 1D CoN- CNTs@PANI nanotubes prevent the restacking of 2D Ti 3 C 2 T x nanosheets, and the conductive framework of 2D Ti 3 C 2 T x nanosheets further suppresses PANI volume change to enhance rate capability and cycling lifespan. Third, the 1D/2D structure leverages synergies to accelerate interfacial charge/ion transport and reaction kinetics, critical for high-power ZICs. As a result, the three-electrode tests showed the electrode delivered 861.7 F g −1 at 0.5 A g −1 and retained 91 % capacitance after 5000 cycles at 10 A g −1 . The assembled CoN-CNTs@PANI/Ti 3 C 2 T x //Zn ZIC achieved 91.2 Wh kg −1 at 1600 W kg −1 , with 86 % capacity retention after 5000 cycles at 2 A g −1 . This work establishes an advanced MXene-based hierarchical design strategy for high-performance ZIC electrodes.