Pillar effect induced by ultrahigh phosphorous/nitrogen doping enables graphene/MXene film with excellent cycling stability for alkali metal ion storage

Graphene's large theoretical surface area and high conductivity make it an attractive anode material for potassium-ion batteries (PIBs). However, its practical application is hindered by small interlayer distance and long ion transfer distance. Herein, this paper aims to address the issue by introducing MXene through a simple and scalable method for assembling graphene and realizing ultrahigh P doping content. The findings reveal that MXene and P-C bonds have a "pillar effect" on the structure of graphene, and the P-C bond plays a primary role. In addition, N/P co-doping introduces abundant defects, providing more active sites for K' storage and facilitating K' adsorption. As expected, the developed ultrahigh phosphorous/nitrogen co-doped flexible reduced graphene oxide/MXene (NPrGM) electrode exhibits remarkable reversible discharge capacity (554 mA h g-1 at 0.05 A g-1), impressive rate capability (178 mA h g-1 at 2 A g-1), and robust cyclic stability (0.0005% decay per cycle after 10,000 cycles at 2 A g-1). Furthermore, the assembled activated carbon||NPrGM potassium-ion hybrid capacitor (PIHC) can deliver an impressive energy density of 131 W h kg-1 and stable cycling performance with 98.1% capacitance retention after 5000 cycles at 1 A g-1. Such a new strategy will effectively promote the practical application of graphene materials in PIBs/PIHCs and open new avenues for the scalable development of flexible films based on two-dimensional materials for potential applications in energy storage, thermal interface, and electromagnetic shielding. (c) 2024 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.