Construction of strongly coupled few-layer FePSe3-CNT hybrids for high performance potassium-ion storage devices

Given the layered crystal structure and tunable composition, ternary metal phosphorus trichalcogenides (MPCh3) is an attractive anode material for potassium-ion batteries with higher surface activity and mobility than their binary analogues. However, how to improve the electronic conductivity, ion diffusion, and maintain high reversible potassiation/depotassiation processes are the main key issues for the development of MPCh3-based electrodes with high rate and long cycle life. For example, theoretically, FePSe3 has a layered crystal structure with high electronic conductivity and low diffusion barrier, yet their K+-based electrochemical performance not well demonstrated. Here, we report a mechanical exfoliation method to prepare few-layer FePSe3-carbon nanotube (f-FePSe3/CNT) hybrids for use as high-efficiency K+ storage anodes. Electrochemical performance, kinetic analysis, reaction mechanism analysis, and density functional theory calculations show that this strongly coupled 1D-2D hybrids promotes the reaction and diffusion of potassium ions, giving full play to the inherent advantages of materials with different dimensions. Therefore, the f-FePSe3/CNT PIB anodes exhibit high capacity (472.1 mA h g-1, 0.05 A/g), high rate (124.9 mA h g-1, 10 A/g), and cycling stability (>1000 cycles), which significantly exceeds the performance of its binary analogue, here FeSe. In addition, the full cells of potassium-ion battery and hybrid capacitor coupled with f-FePSe3/CNT anodes exhibit good cycling stability (500 cycles) and high energy/power density of 54.7 W h kg-1/5790.8 W kg -1, respectively, revealing its practical applica-tions in a wide range of K+-based storage systems. We believe that this work will provide a universal strategy for effectively activating the K+ electrochemical performance on a wide range of layered materials.

Automated summary

Few-layer FePSe3-carbon nanotube hybrids prepared by mechanical exfoliation exhibit high capacity, rate, and cycling stability as potassium-ion storage anodes, exceeding the performance of its binary analogue FeSe. This work provides a universal strategy for effectively activating the K+ electrochemical performance on a wide range of layered materials.