Ti 3 C 2 T x (MXene) exhibits attractive properties in different applications. However, traditional synthesis leads to unsatisfactory yield of two-dimensional (2D) Ti 3 C 2 T x , e.g., lower than 20%, which stems from the strong interactions of potential Ti−Ti bonds and residual Ti−Al bonds between the adjacent Ti 3 C 2 layers, hindering the effective intercalation and delamination. Herein, we propose a facile hydrothermalassisted intercalation (HAI) strategy to boost the yield of 2D sheets, achieving a record high value of 74%. This HAI assists the diffusion and intercalation of reagent effectively, promoting the subsequent delamination; meanwhile, an antioxidant is applied to protect these Ti 3 C 2 T x from oxidation during the HAI process. Therefore, massive Ti 3 C 2 T x 2D sheets can be easily synthesized. Thanks to the synergistic effect of high conductivity and substantial terminated functionalities, these Ti 3 C 2 T x 2D sheets show promising application in supercapacitor, providing a high capacitance of 482 F g −1 . Besides, the ultrafast carrier dynamics results of Ti 3 C 2 T x 2D sheets clearly imply the promising application in photocatalysis due to the relatively long bleaching relaxation time. Our work not only paves the way for the mass production of Ti 3 C 2 T x 2D sheets but also provides insights into their electronic and optical properties. KEYWORDS: hydrothermal-assisted intercalation (HAI), Ti 3 C 2 T x , MXene, high yield, facile

High-rate capability has become an important feature for energy storage devices, but it is often accompanied with a significant reduction in energy density. Therefore, developing an energy storage technology that combines high-rate capability with high energy density is a great challenge for nextgeneration electronic devices. Here, parallel circuitry is constructed at the nanoscale to lower the resistance for ion and electron transport that largely determines the rate performance. The parallel circuitry is constructed through intertwining continuous carbon nanotubes with an interpenetrating conductive assembly based on hierarchically layered MXene (Ti 3 C 2 T x ) functionalized by KMnO 4 (MnO x @Ti 3 C 2 T x ). The assembly shows ultrafast rate capability, e.g., maintaining 50% capacity when the current density increases from 0.1 to 10 A g −1 . Investigations of the kinetics and charge storage mechanisms confirm the efficiency of the designed parallel circuitry in improving rate capability by providing rapid pathways for ions and electrons, as well as dividing the current flow evenly into individual MnO x @Ti 3 C 2 T x flakes in the assembly. The flexible MnO x @Ti 3 C 2 T x based electrode endows zinc ion batteries with outstanding mechanical robustness and good power delivering performance. The paradigm presented here paves a new way for designing electrodes with high-rate capability toward next-generation energy storage technologies.

Owing to its electronic conductivity and electrochemical reactivity, polyaniline (PANI) can serve as the cathode for rechargeable zinc-ion batteries (ZIBs). However, it suffers from fast deactivation and thus performance deterioration because of spontaneous deprotonation during charge/discharge. Here, we report an effective strategy to improve the electrochemical reactivity and stability of the PANI-based cathode by constructing a π-electron conjugated system between PANI and poly­(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on carbon nanotubes (CNTs). The impressive performance of the post-treated CNTs–PANI–PEDOT:PSS (t-CNTs–PA–PE) cathode is largely attributed to the −SO3 –H+ groups in PSS, which acts as an internal proton reservoir and provides enough H+ for PANI’s protonation, thus promoting its electrochemical activity and reversibility. Besides, the strong interactions between PANI and PEDOT:PSS assist the stretching of π–π conjugation chains, bringing about enhanced electronic conductivity. Consequently, the t-CNTs–PA–PE cathode achieves a high capacity of 238 mA h g–1, together with good rate capability and long-term stability (over 1500 cycles with 100% Coulombic efficiency). Through exerting the freestanding t-CNTs–PA–PE, a flexible ZIB was further constructed with both outstanding electrochemical properties and superior high safety. This work demonstrates the availability of conducting polymer cathodes for high-performance ZIBs, fulfilling the need of flexible electronics.

HIGHLIGHTS • Hierarchical porous reduced graphene oxide/poly(3,4-ethylenedioxythiophene)/polyaniline hybrid was designed. • The hybrid achieves a high capacitance of 535 F g −1 along with a good rate capability and cyclability. ABSTRACT Many hybrid electrodes for supercapacitors (SCs) are a reckless combination without proper structural design that keeps them from fulfilling their potential. Herein, we design a reduced graphene oxide/poly(3,4-ethylenedioxythiophene)/polyaniline (RGO/PEDOT/PANI) hybrid with hierarchical and porous structure for high-performance SCs, where components fully harness their advantages, forming an interconnected and conductive framework with substantial reactive sites.Thus, this hybrid achieves a high capacitance of 535 F g −1 along with good rate capability and cyclability. The planar SC based on this hybrid deliver an energy density of 26.89 Wh kg −1 at a power density of 800 W kg −1. The linear SC developed via modifying a cotton yarn with the hybrid exhibits good flexibility and structural stability, which operates normally after arbitrary deformations. This work provides a beneficial reference for developing SCs.

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