Aggregation-Resistant 3D Ti3C2TxMXene with Enhanced Kinetics for Potassium Ion Hybrid Capacitors

Potassium-ion hybrid capacitors have attracted increasing attention due to good energy density, high power density, and low cost. Ti3C2Tx-MXene is considered as a promising anode material for K ion storage. However, undesirable stacking issues decrease its exposed area and breeds sluggish K ion transport. Herein, a facile spray-lyophilization strategy is proposed to construct stacking-resistant Ti(3)C(2)T(x)with 3D structures. As-prepared Ti(3)C(2)T(x)hollow spheres/tubes present stack resistance, a large specific surface area, and a short ion diffusion pathway. When serving as an anode material, it shows enhanced capacity and thickness-independent rate performance compared to 2D Ti3C2Tx. After 10 000 cycles, a specific capacity of 122 mAh g(-1)is obtained at 1 A g(-1). Systematic kinetics analyses demonstrate the significance of concentration polarization on the electrode's rate ability. Furthermore, a 3D Ti3C2Tx||hierarchical porous activated carbon (HPAC) K-ion hybrid capacitor is assembled and displays remarkable energy and power densities with energy retention of 100% after 10 000 cycles at 1 A g(-1). Following this strategy, other 3D structures from nanosheets can also be obtained, such as 3D Ti(3)C(2)T(x)microtubes and graphene oxide nanoscrolls. This study provides a viable approach to solve the stacking issues of 2D nanosheets to promote the application of 2D materials.