Interstratification-assembled 2D black phosphorene and V2CTx MXene as superior anodes for boosting potassium-ion storage

Abstract

Although potassium-ion batteries have been widely studied because of their low cost and high theoretical capacity, the origin of the poor potassium-ion storage kinetics and low structural stability still remains elusive mainly due to the large size of K⁺ (0.138 nm). Herein, we report an interstratification-assembly strategy via van der Waals interactions to design a novel BPE@V₂CT_x hybrid anode, wherein black phosphorene (BPE) and V₂CT_x MXene are derived from their individual 2D nanosheets. The coupled BPE@V₂CT_x hybrid anode with a 2D stacked interstratification structure and large specific surface area could efficiently take advantage of BPE and V₂CT_x nanosheets and create more active sites. This interstratification hybrid electrode not only provides an enlarged interlayer spacing and a three-dimensional interconnected conductive network to accelerate the K⁺ transport rates, but also has good tolerance to volume changes caused by phase transformations during the fast potassiation/depotassiation process. DFT calculations further confirm that potassium affinities and diffusion kinetics are significantly enhanced in the BPE@V₂CT_x hybrid anode, particularly in BPE@V₂CF₂. As a result, the hybrid anode possesses a remarkable synergetic effect and achieves a high reversible capacity of 593.6 mA h g⁻¹ at 0.1 A g⁻¹ and excellent cycling stability of 485/261 mA h g⁻¹ with 91/86% capacity retention after 3000 cycles at 0.2/2.0 A g⁻¹. This work opens a new way for the application of self-assembled hybrid electrodes in energy storage, electrocatalysis and sensors.